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View Full Version : Best water pick-up ever!



forescott
12-18-2010, 10:54 AM
I bought one of these from ose for my sv-27/stiletto outboard conversion and I have to say this is the highest flowing water pick-up I've ever used! It almost looks comical how much water shoots out the side of the hull even at low speeds. I know its not the most hydro-dynamic piece, but there is no doubt that my esc is getting all the cool water it can handle. I will definitely be using more of these!!

http://www.offshoreelectrics.com/proddetail.php?prod=oct-ocsw

dasboata
01-21-2011, 03:29 PM
Where do you have it mounted ?. I do not see it in the pic, if it is draging in the water it will work well but will cost you some speed and possible trim issues

H&MWill
01-21-2011, 03:56 PM
I used one of these too on my dads SV. It definately flows alot of water. I was actually going to use a little bit smaller diameter hose because I think it may flow too much and the water doesnt have the time to actually pull the heat away from the motor and ESC. It is a nice piece though.

forescott
01-21-2011, 07:38 PM
Its close to the center of the V, and close to the transom where I know it will pick up water @ high speed. I've used many under-hull pick ups that just don't pick-up! And rudder pick ups that lose pressure when turning opposite the direction of the hull. As far as scrubbing speed, I've found no noticeable loss in speed from this pick-up. The drag created is minimal and may only show in tenths of a mph from a gps. For me a couple of tenths of my top speed is worth getting plenty of fresh, cool water through my electronics! And as far as handling issues, I haven't had any so far.

forescott
01-21-2011, 07:43 PM
I've pulled boats out of the water with hot motors and blew mouthfulls of cold bottled water through the pick-ups as hard as I could and the water always comes out hot. I doubt even the highest flowing system is flowing fast enough to pass up the heat from the components. JMO!

sailr
01-21-2011, 07:48 PM
I'm always worried those things would snag on something and rip a hole in the bottom of the hull.

forescott
01-21-2011, 08:13 PM
LOL! I guess anything can happen! Your rudder will rip a hole in your transom first!

johnmaclean
01-21-2011, 08:21 PM
I have those installed on my sv (bought it used and it came with them) and was having trouble with handling this summer. After some fairly lengthy discussion on another site the general consensus was that they protruded too far down and was acting like trim tabs. I filed them down so that their profile was less than 1/4 inch at the lowest point. It seemed to correct the handling issue but I am still considering going back to using the rudder pick up.

westbeach
01-21-2011, 09:00 PM
Nope, almost all rudders have a break away screw (brass or nylon) so you don't rip your transom apart!!


LOL! I guess anything can happen! Your rudder will rip a hole in your transom first!

igottalongone
01-22-2011, 11:11 AM
Octura makes the same thing in a transom mount as well (mounts to the back of the transom, not bottom of the hull) I like that one a little better... It lets you have just the pickup below board, a little less drag with the same output...
Octura calls it (SMWP) Stern Mount Water Pick Up

Steven Vaccaro
01-22-2011, 11:15 AM
Octura makes the same thing in a transom mount as well (mounts to the back of the transom, not bottom of the hull) I like that one a little better... It lets you have just the pickup below board, a little less drag with the same output...

I didnt know that, do you happen to have the part number?

H2OCamel
01-22-2011, 11:29 AM
Scott, those are the only ones I have added to my boats the most famous being a super Hawaii which I put 2 in, one on each side at the rear and used the Octura outputs on the transom looking like exaust ports for the disel engines. One feed the speed control and the other the motor. It functioned very well keeping the 19v SS1 very cool during the entire run. I don't race so cooling effectiveness was more important to me. The bonus is that at any speed there is no doubt that the water pickup is working!

forescott
01-22-2011, 11:36 AM
Scott, those are the only ones I have added to my boats the most famous being a super Hawaii which I put 2 in, one on each side at the rear and used the Octura outputs on the transom looking like exaust ports for the disel engines. One feed the speed control and the other the motor. It functioned very well keeping the 19v SS1 very cool during the entire run. I don't race so cooling effectiveness was more important to me. The bonus is that at any speed there is no doubt that the water pickup is working!


YES! That's what amazed me. The flow is awesome even at low speeds!

H2OCamel
01-22-2011, 02:33 PM
Steven I'm not exactly shure but I think the part number is #71?

keithbradley
01-22-2011, 08:27 PM
I used one of these too on my dads SV. It definately flows alot of water. I was actually going to use a little bit smaller diameter hose because I think it may flow too much and the water doesnt have the time to actually pull the heat away from the motor and ESC. It is a nice piece though.

Thats a myth. As long as there is a constant suppy of water there it will cool, and the cooler the water is (faster flow), the better it will cool. Alot of people say that about cars with water pumps that flow too much but the truth is its just not true.

don ferrette
01-23-2011, 09:21 AM
Thats a myth. As long as there is a constant suppy of water there it will cool, and the cooler the water is (faster flow), the better it will cool. Alot of people say that about cars with water pumps that flow too much but the truth is its just not true.Actually that's not correct. It is both the amount of water AND the speed in which the water travels. All the water in the world may not properly cool if it does not spend enough time around the object you are trying to cool. This can be done by either restricting the outlet (typically done by the size of the hole on the outlet fitting) to slow the water down or restricting the inlet side to slow the water (the water slows once it passes the restriction) as well as reducing the amount. Controlling the rate of exit is very effective but you need to be careful with too much restriction at speeds over 90 as alot of pressure can build in the lines as a result. On my record trials boats I'll typically restrict both the inlet and outlet using both to achieve the desired temperatures. Using your car analogy going back to when I raced real cars, if you take out the thermostat completely the engine can and usually will actually overheat due to insufficient thermal transfer between the motor and the water. Companies like Moroso make restrictor plates with various size holes that fit in place of the thermostat to help regulate flow rates on race cars. The same goes for the water pumps, we used different sized pulleys to control the speed of water to improve thermal transfer. It is no different with our boats as it is possible to over cool as well as under cool. It doesn't matter if it's nitro, gas of FE powered, all have optimum operating temperature ranges and playing with the rates and speeds of the water will help you get there. :smile:

forescott
01-23-2011, 10:09 AM
I agree with keith, Why would you want to slow the water flow and let it heat up? More flow will just bring more cool water to the components. Even if the water passes through the system quickly and doesn't pick up as much heat as it might if it were sitting there, its still going to be followed by more cool water. You cant compare the flow of water from an rc boat that trickles out the side of a water outlet to a car engine with a water pump that is designed to force water through an engine. The rate of flow is far less in an FE boat and I don't that the amount of pressure created from even the highest flowing water pickup is cause for any concern.

don ferrette
01-23-2011, 10:19 AM
I agree with keith, Why would you want to slow the water flow and let it heat up? More flow will just bring more cool water to the components. Even if the water passes through the system quickly and doesn't pick up as much heat as it might if it were sitting there, its still going to be followed by more cool water. You cant compare the flow of water from an rc boat that trickles out the side of a water outlet to a car engine with a water pump that is designed to force water through an engine. The rate of flow is far less in an FE boat and I don't that the amount of pressure created from even the highest flowing water pickup is cause for any concern.I'm not going to debate what you might believe, just sharing what I know from experience. It's called thermal transfer, the water needs to be there long enough for the heat to transfer from whatever you are trying to cool to the water itself. And secondly yes you can develop very high pressure even with the smallest of water pick ups. I have to pay close attention to regulating water pressures on my SAW boats, even my faster heat race stuff is controlled. In the past I have blown even the best quality line from excessive pressure. You would be surprised how much pressure you can build through that tiny pick up at over 100....... :eek:

westbeach
01-23-2011, 10:31 AM
Don is right. There was a debate a while back, and Jay Turner pretty much summed it up what Don is saying here. Like it or not these guys have the knowledge and experience we all need to learn from. :Peace_Sign:


I'm not going to debate what you might believe, just sharing what I know from experience. It's called thermal transfer, the water needs to be there long enough for the heat to transfer from whatever you are trying to cool to the water itself. And secondly yes you can develop very high pressure even with the smallest of water pick ups. I have to pay close attention to regulating water pressures on my SAW boats, even my faster heat race stuff is controlled. In the past I have blown even the best quality line from excessive pressure. You would be surprised how much pressure you can build through that tiny pick up at over 100....... :eek:

Diegoboy
01-23-2011, 10:34 AM
A car has to re-cool the water before it cycles through the engine again. That doesn't really apply to us.

But...

Heat Convection happens when matter carries heat from one place to another.

If the water cannot thermally transfer the heat from the electronics to itself and carry it away, it isn't very effective.

egneg
01-23-2011, 10:36 AM
I would also agree with the high flow crowd. You want to get a more effective heat transfer so a faster flow will provide a greater differential throughout its path through the system. If it heats up to much before it leaves the cooling system the components at the end will not benefit as much. That is why some folks have a dual system for ESC and motor.

Chuck

forescott
01-23-2011, 10:47 AM
I'm not going to debate what you might believe, just sharing what I know from experience. It's called thermal transfer, the water needs to be there long enough for the heat to transfer from whatever you are trying to cool to the water itself. And secondly yes you can develop very high pressure even with the smallest of water pick ups. I have to pay close attention to regulating water pressures on my SAW boats, even my faster heat race stuff is controlled. In the past I have blown even the best quality line from excessive pressure. You would be surprised how much pressure you can build through that tiny pick up at over 100....... :eek:

A 100mph saw boat is a not a 40mph sport boat. Still not a good comparison.But I get your point! :beerchug:

Diegoboy
01-23-2011, 10:52 AM
Check out THIS (http://books.google.com/books?id=43U7AAAAIAAJ&printsec=frontcover&dq=Fluid+mechanics+and+transfer+processes&hl=en&ei=ck48TbjKGMSAlAecm9zqBQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCkQ6AEwAA#v=onepage&q&f=false) book, Start on section 13.1 or Page 344

egneg
01-23-2011, 11:40 AM
Also a higher flow rate will cause more turbulence increasing the rate of heat transfer.

don ferrette
01-23-2011, 12:04 PM
All I'm trying to explain is that controlling the water is an easy way to control temps, you can run both too hot and too cold and faster flow is is not the answer if things are sized properly. Optimum thermal transfer occurs when the water is there long enough to absorb the heat. For example I can more than adequately cool a twin 90 nitro heat race rigger in the dead of a southern summer running on 60% nitro with a single water pick up rudder blade. Yeah it's a nitro boat but it's just an example and capable of generating a tremendous amount of heat. Again, I'm just sharing what I know from experience and not trying to force anyone to change what they might steadfastly believe. But then again people at one time were absolutely certain the world was flat..............

It's all good fellas, you all have a fun day. :hug1:

keithbradley
01-23-2011, 12:40 PM
Actually that's not correct. It is both the amount of water AND the speed in which the water travels. All the water in the world may not properly cool if it does not spend enough time around the object you are trying to cool. This can be done by either restricting the outlet (typically done by the size of the hole on the outlet fitting) to slow the water down or restricting the inlet side to slow the water (the water slows once it passes the restriction) as well as reducing the amount. Controlling the rate of exit is very effective but you need to be careful with too much restriction at speeds over 90 as alot of pressure can build in the lines as a result. On my record trials boats I'll typically restrict both the inlet and outlet using both to achieve the desired temperatures. Using your car analogy going back to when I raced real cars, if you take out the thermostat completely the engine can and usually will actually overheat due to insufficient thermal transfer between the motor and the water. Companies like Moroso make restrictor plates with various size holes that fit in place of the thermostat to help regulate flow rates on race cars. The same goes for the water pumps, we used different sized pulleys to control the speed of water to improve thermal transfer. It is no different with our boats as it is possible to over cool as well as under cool. It doesn't matter if it's nitro, gas of FE powered, all have optimum operating temperature ranges and playing with the rates and speeds of the water will help you get there. :smile:

Restrictors in the thermostat housing on older motors are used to allow the engine to retain SOME heat. I have ran countless cooling systems w/o thermostats and the result is an engine that stays TOO COOL.
If a car does overheat without a thermostat, the water pump is not strong enough to produce sufficient pressure in the coolant system, and you end up with what people commonly refer to as an air pocket. I assure you, if you take the thermostat out, and the car runs hotter, it is due to NOT ENOUGH FLOW.

I do this stuff for a living. I have spent hours upon hours R&D-ing cooling systems for supercharger and turbocharger intercoolers. If you could run a fire hose through an automotive cooling system it would cool incredibly well.
The myth, on the automotive side, is completely ridiculous. The engine temps people refer to are actually coolant temps. So the logic is that the coolant doesnt have enough time to remove heat from the engine, adn the result is the coolant is too hot...
HUH?:ohmy:

There is a point where excessive coolant speed can hinder cooling, but it is due more to poor coolant system design in real world applications. The most important thing is when the speed increases, the volume must increase also.

As someone noted, guys like Don have been doing this for a long time, and I would support taking their advice and I would be likely to take it myself. Im not arguing against ANYTHING they reccomend to do to your boat, just defending my statment about cooling flow. I have battled this with customers and peers in the automotive world for as long as I can remember. There are many reasons that coolant speed would hinder cooling, but in real life applications most of them dont apply.

keithbradley
01-23-2011, 12:43 PM
All I'm trying to explain is that controlling the water is an easy way to control temps, you can run both too hot and too cold and faster flow is is not the answer if things are sized properly. Optimum thermal transfer occurs when the water is there long enough to absorb the heat. For example I can more than adequately cool a twin 90 nitro heat race rigger in the dead of a southern summer running on 60% nitro with a single water pick up rudder blade. Yeah it's a nitro boat but it's just an example and capable of generating a tremendous amount of heat. Again, I'm just sharing what I know from experience and not trying to force anyone to change what they might steadfastly believe. But then again people at one time were absolutely certain the world was flat..............

It's all good fellas, you all have a fun day. :hug1:

I would agree with most of that, and what works is what matters more than why it works, so for all applicable reasons, I would take what advice you have to offer on the subject adn value it higher than any theoretical info.
The only thing I would change is if you are going to restrict flow, I would ALWAY do it on the backside of a cooling system, unless you are having problems with excessive pressure.

egneg
01-23-2011, 01:10 PM
I don't know much about IC applications but have dealt with chillers, cooling towers, and heat exchangers for industrial applications for about 30 years now. I have also been involved with HVAC, including water to air systems for the same amount of time. And when pumping water through a system (whether it be a closed or open system) with an electric motor the flow has to be restricted going into the pump to prevent over amping the motor and that is the only limitation. If the motor/pump is to small for proper heat transfer than a bigger motor/pump is required. Pressure and flow rate have a direct relationship to line size and pump volume and have to be sized to do the job in a costly manner not because it provides to much cooling.

Chuck

Jeff Wohlt
01-23-2011, 05:09 PM
The key is...is the jacket constantly under full pressure at all times.

We already proved cold water recirculation keeps temps lower. Motor ran the same but water temps brought in were colder....so it seems to stand that colder water at any rate will cool better.

Some say absorb and other seem to say keep the water cooler all the time and motor will be cooler.

carlcisneros
01-23-2011, 07:50 PM
one little tid-bit that was mentioned and only a few took up on it was that the
water has to stay IN CONTACT with what ever it is trying to draw heat away
from LONG ENOUGH to reduce the heat generated by what ever needs to be
cooled. ( I think that came out right.)

Night all, going back to watching Total Recall.

H&MWill
01-24-2011, 12:37 PM
Wow, didnt mean to stir this up LOL. Was just stating what I had heard a few years ago from some smart people on this forum and other places. Oh well whatever works for ya. Have a good day. Will

Chuck E Cheese
01-26-2011, 04:46 AM
there is no question about it, don is right. if water flows through the system to fast it can not absorb the heat. everything is designed with a optimal opperating tempature, determined by tolerances. just because the water coming out and the outside can of a FE motor is cooler does not mean the internals are colder. it is possable to cool the outside can so fast that the rotor and stator do not have a chance to transfer maximum heat to that can. when you check the tempature of the motor it may be cooler in places (outer can) but the internals can verry well be hoter.
also, yes you can blow lines even at slower speeds. i know this from experience and none of my boats are faster than 62-63mph and i dont restrict the flow other than by the size of the lines and water outlets.

gerardobrandao
01-26-2011, 12:17 PM
Hello!

An water pickup that drives alot of water trough the cooling tubes is awesome, altough, mine opinion is that you have to get the correct placement for it!
I putted mine near the keel of mine DF35 and tried everything to trim the boat up...weeks after weeks....It was chine waliking a lot and dindn´t have a sable behaviour..after 2 months i thought...What a a hel...let me try taking off the water pick up......I couldn´t don anything more to trim the boat...i tried everything....
The boat behaviour was from water to wine... :D
The issue is...look where you put it...

regards

Doug Smock
01-26-2011, 01:01 PM
When things slow down for me I'm going to build a suitable water cooled heat exchanger, fire up a 30,000 BTU torch and a video camera, and put this to bed.LOL
Do you want to make coffee, or do you want to cool your componets?? Think about it.

The absolute bottom line is this. If you can't get adequate cooling by means of what we consider standard water cooling, your boat has the wrong set up, it is poorly set up, or you are running the wrong prop.
Just my .02 till I have more time.
Hang tough fellas!!
Doug

egneg
01-26-2011, 04:38 PM
:iagree: Doug has it right. Maximum Flow = Maximum Cooling!

westbeach
01-26-2011, 07:19 PM
Heat from components needs time to dissipate into the water (thermal exchange) inorder to properly cool the component. This is done by utilizing a bigger bore tubing, slows water rate down when entering the component then back to a smaller diameter bore tubing to quickly evacuate the thermally heated water.

Brushless55
01-26-2011, 11:27 PM
:iagree: Doug has it right. Maximum Flow = Maximum Cooling!

Bingo!
I run the stock cooling on my SV's with a bigger hole in the rudder pickup and I get much more flow out of the system, and get this I can run any prop I want and my temps never get above 125* no matter what and usually hand at 110* and lower :rockon2:

I think some are over thinking this :confused2:

forescott
01-26-2011, 11:52 PM
I think some are over thinking this :confused2:

:iagree: Most people don't run 100mph, or have big block chevys in their rc boats. I'm talkin your basic 40mph sport boat. Can't have too much water @ that speed.

Brushless55
01-26-2011, 11:56 PM
:iagree: Most people don't run 100mph, or have big block chevys in their rc boats. I'm talkin your basic 40mph sport boat. Can't have too much water @ that speed.

Yes! :beerchug:

igottalongone
01-28-2011, 08:57 PM
I didnt know that, do you happen to have the part number?

Hi, Steven...
Call Trudy and tell her you want part "(SMWP) Stern Mount Water Pick Up"
They are Shweet!

FRED
02-05-2011, 10:27 PM
nothing

785boats
02-06-2011, 02:11 PM
Westbeach has hit the nail on the head.

Heat from components needs time to dissipate into the water (thermal exchange) inorder to properly cool the component. This is done by utilizing a bigger bore tubing, slows water rate down when entering the component then back to a smaller diameter bore tubing to quickly evacuate the thermally heated water.
That's the theory I used when I up graded my home made ESC cooling plates from having only one pathway cross drilled through the plate (in the usual 'U' shape), to having 3 pathways. This effectively increases the volume of water in the plate at all times & it slows down as it is divided evenly over 3 tubes & then speeds up again on exit as it recombines at the outlet tube. The ESC with this plate definitely runs cooler than it did before in the same boat & setup. Might try 4 cross holes next time.
The photo shows the three cross holes in the plate about to be re attached to the ESC
Cheers.
Paul.

FRED
02-06-2011, 05:52 PM
nothing

ManuelW
02-06-2011, 06:04 PM
Hello Guys,

just want to join the discussion. First a few words about myself. I've been studying mechanical engineering for 5 years now and topically making my masters degree. Within these 5 years I also learned a lot concerning this topic due to lectures in thermo and fluid dynamics as well as heat exchange.

Therefore I can say, the more water flow, the better it is. The idea of slow water because it needs time to heat up is just a so-called hoax. So I think limitation should only be a choice when the pressure gets too high that the flexible hoses get off even if they are already secured.

And as I also run several FE quite fast FE boats for several years now I can say, the experience approved the theory. So my statement: The more - the better.

If interested I might try to explain the theory behind it with an easy explanation.

Best regards,
Manuel

mm123521
02-06-2011, 06:42 PM
I'am with Manuel:

I am a degreed engineer (for 35 years now) at an industrial plant.
One of my projects was to design a $1,000,000 cooling system for our process.
It involved many large heat exchangers.
This project gave me an oppertunity to study heat transfer.
All the principals involved are exactly the same as cooling an RC motor.

I am absolutely sure that more water cools better.
I am absolutely sure: the faster the water flows the better.
Slowing down the water flow will result in a hotter motor.

Mark

FRED
02-06-2011, 09:44 PM
nothing

mm123521
02-06-2011, 10:30 PM
Fred:

I started running water cooled RC boats 15 years ago.
I am 60 years old, so I guess I been around the block also.
I have studied all the science behind water cooling and have done it on an industrial scale.
If I could have restricted the water flow on that $1,000,000 project AND improved the cooling, I could have saved $200,000 in pumps and pipes. But it just doesnt work that way.

I have adjusted flow rates on that industrial cooling system and observed temperatures, so I also have first hand, practical, experiance that validates: More water flow= better cooling.

We would get zebra mussels (little clams) that clogged up the pipes and restricted the cooling water flow and the temperatures always went up as the water flow choked down. When we cleaned the Zebra mussels from the pipes (increased the water flow), the temperatures always went down.

I am 100% sure of what I say, as I have book learning AND practical experiance.

Its exactly the same principals: RC boat or industrial water cooling.

Mark

Brushless55
02-07-2011, 12:16 AM
Funny how this thread had gone :doh:
how about we use what works for us? :olleyes:

bottom line.............................................. .....................
if a motor is getting very hot then the setup is not 100%

wild bill
02-07-2011, 12:39 AM
just get a heat gun and pick a target temp you want.(heat you want for your application)simple!

ManuelW
02-07-2011, 02:58 AM
@ Fred:
Well, so you want to talk about my experience with FE boats? Well I might have studied and I'm quite young as well (23 to be honest), but I think I have already more experience and knowledge than most others.

And comparing apples and oranges: You compare the experience of a guy with 1:1 cars racing to the cooling system in our boats?
To explain it as simple as possible: They "reduce" flow to increase pressure and therefore avoid that the water in their closed-loop cooling system boils, which would be absolute horror. Normally water boils at 100°C, but like in a pressure cooker under pressure it will boil much later. And thats why they make it. Otherwise the water will boil in certain hot parts and cooling power will there decrease dramatically, resulting in blown engines due to overheating.

We wether have a closed-loop cooling system nor problems with boiling water (if so, get a bigger engine and ESC or rethink your setup ;-D ), therefore its just a completely different story.

I just want to help with my knowledge and experience, that's why I absolutely recommend to increase flow as much as possible. And only because something was done so for ages, it doesn't need to be the best solution.

Best regards,
Manuel

igottalongone
02-07-2011, 10:43 AM
ever see someone drill a hole in steel?
remember the little spout running coolant on the bit?
that cools as fast as it touches the bit, and falls away instantly.
the contact time with the bit is less than a second...

Shooter
02-07-2011, 01:19 PM
Heat transfer is due to temperature differential. The higher the differential, the more heat transfer. In general, higher delta T's occur when the flow is the HIGHEST!

What complicates matters is the geometry of the contact area and flow dynamics. Hot spots can be created due to flow separation at certain velocities, etc... so there is a limit to the statement above. However, it is still the "meat and potatoes" of the answer.

ReddyWatts
02-07-2011, 08:32 PM
Heat transfer is due to temperature differential. The higher the differential, the more heat transfer. In general, higher delta T's occur when the flow is the HIGHEST!



:iagree: Doug has it right. Maximum Flow = Maximum Cooling!

I agree, but keep the pressure and flow rate reasonable. The right setup is the best solution to over heating.

LarrysDrifter
02-07-2011, 09:16 PM
I used one of those water pick ups on the UL-1 I used to have.It worked great.I can say,Ill probably use another one somewhere in the future.

dasboata
02-07-2011, 11:11 PM
My 2 cents related to a car heater,, the slower the fan the hotter the air is the faster you run the fan the cooler the air gets that to me means that the higher air flow is removing more heat !!!

keithbradley
02-08-2011, 09:31 AM
Hello Guys,

just want to join the discussion. First a few words about myself. I've been studying mechanical engineering for 5 years now and topically making my masters degree. Within these 5 years I also learned a lot concerning this topic due to lectures in thermo and fluid dynamics as well as heat exchange.

Therefore I can say, the more water flow, the better it is. The idea of slow water because it needs time to heat up is just a so-called hoax. So I think limitation should only be a choice when the pressure gets too high that the flexible hoses get off even if they are already secured.

And as I also run several FE quite fast FE boats for several years now I can say, the experience approved the theory. So my statement: The more - the better.

If interested I might try to explain the theory behind it with an easy explanation.

Best regards,
Manuel

I cant beleive this arguement is still going on. I have bit my tongue with every post in this thread since my last one because it seems to be one of those things that people just choose to beleive. I am amazed at how many people buy into such a silly theory. I dont understand how one can logically come to the idea that water becomes insulative at higher flow rates, or that the water "goes away" to fast even though there is constant contact between the heat source and water. I didnt mean to create such an arguement with my initial post, but I have witnessed the same myth in auto racing and felt the need to kill it before it spread.
My wife once stuck a hot french fry out the window of our car moving down the freeway at 70 mph to cool it off before feeding it to our baby. If I told you that it never cooled down because the air was simply moving to fast to remove the heat, would that make sense?
I too work in a field that allows me to test these things, but Im honestly baffled that this is any more than common sense to people.

Shooter
02-08-2011, 01:44 PM
I understand your frustration, Keith. Not sure how that myth was started in the first place, but I would bet that people are thinking opposite......i.e. if we were trying to HEAT a fixed amount of water, then YES, the flow can be too fast! I think Doug alluded to that when he said "making coffee". Too funny!! :laugh:

Old Sloppy
02-12-2011, 06:16 PM
My wife once stuck a hot french fry out the window of our car moving down the freeway at 70 mph to cool it off before feeding it to our baby. If I told you that it never cooled down because the air was simply moving to fast to remove the heat, would that make sense?


My wife did the same thing except the french fry was frozen with dry ice, when it was held out the window it instantly burst into flames because the air was simply moving to fast to remove heat.

Seems logical enough to me...

Harry

forescott
02-12-2011, 08:59 PM
Maybe I should just seal a chocolate shake inside the hull instead?

Brushless55
02-12-2011, 10:48 PM
Maybe I should just seal a chocolate shake inside the hull instead?

and then get some marshmallows for the hot chocolate when your done! :roflol:

properchopper
02-15-2011, 11:59 AM
I bought one of these from ose for my sv-27/stiletto outboard conversion and I have to say this is the highest flowing water pick-up I've ever used! It almost looks comical how much water shoots out the side of the hull even at low speeds. I know its not the most hydro-dynamic piece, but there is no doubt that my esc is getting all the cool water it can handle. I will definitely be using more of these!!

http://www.offshoreelectrics.com/proddetail.php?prod=oct-ocsw

I've been following this thread and think there's some good info on both sides of the controversy, but agree with those that state that a proper setup is most important and proactive in controlling temps - more important than depending on cooling to prevent problems on borderline setups.

FWIW I've used the pickup for an outlet ; picture on my beater T29. Makes the flow more visible.

Old Sloppy
02-15-2011, 06:50 PM
I prefer a pair of these.
http://www.offshoreelectrics.com/proddetail.php?prod=ose-80400
one for an inlet and one for the outlet.

Harry

PDR447
02-16-2011, 12:18 AM
the french fry analogy is the best analogy ever!

if you stick a french fry out a window while driving, eventually it will cool down. the faster you drive the quicker it cools down. so you either need more time out the window or more speed to get a cold fry. are we all in agreement here?

in an open loop system(FE boats) the boat motor is the french fry and the water is the air. the faster you drive(higher flow rate) the quicker the french fry will cool off.

in a closed loop system(cars) the the coolant is the french fry and the radiator is "out the window". the time the coolant spends in the radiator is the equivalent to the time the fry spends out the window. THIS is where the too high flow rate idea comes from. if the coolant isn't in the radiator long enough it won't cool down. just like if you don't fold the french fry out the window long enough it won't cool down.

now, with the closed loop systems we have two "fry out window" scenarios within the one system. the one above, and the radiator/air relationship. radiator vs air is an open loop system much like the boats and the fry/window. the radiator is the fry and the air is, the air. the more air you get over the radiator the quicker it cools down. that's why your fan kicks on when you're idling too long, you need airflow!

anyone care to disprove this? I'm open to learning...


EDIT: you may substitute the phrase "more heat removed" for "quicker it cools down" anywhere above. and more heat removed is the goal of every cooling system.

properchopper
02-19-2011, 12:11 PM
Well it's raining & I'm bored so I thought I'd jump in to this discussion again with my latest thoughts. I have some boats with high flow rates & some with slow rates & I'd really like to learn more about what's most effective. I'm not sold on the french fry experiment application logic to water-cooled boat electronics ( and what a waste of a good french fry) ! What, at least in my thinking, is most important is the transfer rate between the heat source and the cooling medium which is critically tied to the contact time between these two.

Here's my lab experiments ( perform these at your own risk) :

Test 1:
Run your finger over a hot motor [ say 165 degrees] in one second total. How hot is your finger ?

Then do the same thing but take five seconds to do the same. Hotter finger, right ?

My take is that the longer the cooling medium (your finger) is in contact with the object to be cooled, the more heat transfer from the object to be cooled.

Test 2 : Build a ten foot by five foot bed of hot coals.
Walk (very !) quickly over them. I'm sure you've seen this done on some TV show or something. Feet maybe warm.
Now take ten seconds to do the same. Feet VERY HOT !

Again, the point I'm proposing is that the longer the cooling medium is in contact with the object to be cooled, the more heat extraction takes place.

Slower flow = better cooling
QED

Now go eat some french fries :Peace_Sign:

H&MWill
02-19-2011, 12:33 PM
Well it's raining & I'm bored so I thought I'd jump in to this discussion again with my latest thoughts. I have some boats with high flow rates & some with slow rates & I'd really like to learn more about what's most effective. I'm not sold on the french fry experiment application logic to water-cooled boat electronics ( and what a waste of a good french fry) ! What, at least in my thinking, is most important is the transfer rate between the heat source and the cooling medium which is critically tied to the contact time between these two.

Here's my lab experiments ( perform these at your own risk) :

Test 1:
Run your finger over a hot motor [ say 165 degrees] in one second total. How hot is your finger ?

Then do the same thing but take five seconds to do the same. Hotter finger, right ?

My take is that the longer the cooling medium (your finger) is in contact with the object to be cooled, the more heat transfer from the object to be cooled.

Test 2 : Build a ten foot by five foot bed of hot coals.
Walk (very !) quickly over them. I'm sure you've seen this done on some TV show or something. Feet maybe warm.
Now take ten seconds to do the same. Feet VERY HOT !

Again, the point I'm proposing is that the longer the cooling medium is in contact with the object to be cooled, the more heat extraction takes place.

QED

Now go eat some french fries :Peace_Sign:

I completely agree!

egneg
02-19-2011, 12:46 PM
Wrong! Higher flow carries the heat away faster. The greater the delta the more efficient it will be.

keithbradley
02-19-2011, 12:50 PM
Well it's raining & I'm bored so I thought I'd jump in to this discussion again with my latest thoughts. I have some boats with high flow rates & some with slow rates & I'd really like to learn more about what's most effective. I'm not sold on the french fry experiment application logic to water-cooled boat electronics ( and what a waste of a good french fry) ! What, at least in my thinking, is most important is the transfer rate between the heat source and the cooling medium which is critically tied to the contact time between these two.

Here's my lab experiments ( perform these at your own risk) :

Test 1:
Run your finger over a hot motor [ say 165 degrees] in one second total. How hot is your finger ?

Then do the same thing but take five seconds to do the same. Hotter finger, right ?

My take is that the longer the cooling medium (your finger) is in contact with the object to be cooled, the more heat transfer from the object to be cooled.

Test 2 : Build a ten foot by five foot bed of hot coals.
Walk (very !) quickly over them. I'm sure you've seen this done on some TV show or something. Feet maybe warm.
Now take ten seconds to do the same. Feet VERY HOT !

Again, the point I'm proposing is that the longer the cooling medium is in contact with the object to be cooled, the more heat extraction takes place.

QED

Now go eat some french fries :Peace_Sign:

Tony, I dont understand how you relate hotter finger/feet, to better cooling. If you were trying to figure out the best way to heat the water coming out of your boat that logic would make sense, but youre not. The idea is to cool the electronics, not heat the water. The slower the flow, the hotter the water will get. Thats what your experiments confirm. I would assume we all knew that though?:confused2:

The water is ALWAYS in contract with the item that is being cooled if the flow is good and there is some backpressue there. You are not removing your finger from the motor as you did in experimnet one, you are simply applying constant COOL finger, instead of allowing your finger to heat up and the cooling effect from your finger to diminish.

Look at it this way. Take your same coals, lets say they are 200 degreees. Put them in a pan with a little bit of water in it. Lets say that water is 70 degrees. The coals with heat the water, and water temp will rise. Coal temperature will drop, until they meet at a given temp (lets say 150 degrees, just picking a number). If this were done in an insulated situation, where there was no outside cooling source (like cooler air), and cooling was only dependant on the water, the temp would never go below 150 degrees.

Now take another set of 200 degree coals, in an identical pan, except this pan is plumbed to have a constant flow of fresh 70 degree water, in one side of the pan is a water inlet filling it, and an outlet on the other side letting water escape at the same rate so the pan doesnt overflow.. The water leaving the pan WILL BE COOLER THAN 150 degrees. The water doesnt sit in the pan with coals as long, so a given amount of water will not have absorbed as much energy. It doesnt take a leap of faith, however, to agree that this setup will cool the coals beyond 150 degrees, and eventually all the way down to 70 degrees.

Heres the moral: In these two situations, lets say the pan held 1 quart of water. The quart from the first example where the water sat in the coals would contain more heat energy per quart. HOWEVER, if during the course of cooling in the second example, you pumped 10 gallons through, while the temperature would be lower in that water, it would contain more energy (since it removed more), but since it takes more energy to heat a larger amount of water, temps would be lower.

SO...slower flow is a better means if your goal is to have the hottest water coming out of your boat, but faster flow will keep the largest constant temperature difference in your cooling system, netting the coolest components.

I dont think anyone is arguing that leaving the water in there longer will heat it more. If the opposite were true our real problem would be too fast of flow would heat the lake.:lol:

One more thing...if your motor and coal examples proved better cooling, why move water at all?

properchopper
02-19-2011, 01:58 PM
Wow, my head's starting to hurt thinking about this. Im not advocating not moving the water at all, I think you know that. Simply that the water/motor interface needs sufficient time for heat transfer to equilibrate. In my model I'm assuming that, in an imaginary sense, a "slug" of water enters the cooler, heat transfer/equilibration takes place, and then the water is discharged, and a fresh slug of water enters, and on and on. In my way of thinking ( and I got a D in Thermo in college BTW :crying:) , the length of time the slug stays in place is critical for maximum transfer to take place. In actual application, the rate of (continuous) flow is likened to the latency of slug enter/stay/exit. I think I'll go sharpen some props :Peace_Sign:

Rumdog
02-19-2011, 02:13 PM
WE're not trying to transfer heat here. Keeping the coolest water possible on the esc and can is the best way to keep the item cool. Allowing the water to warm is just allowing everything to warm. This is why when I run in ice cold water min the winter my components run cooler than in a warm pond in the summer.

forescott
02-19-2011, 02:15 PM
I just wanna see someone walk over a bed of hot coals in the spirit of this thread!

keithbradley
02-19-2011, 02:21 PM
Wow, my head's starting to hurt thinking about this. Im not advocating not moving the water at all, I think you know that. Simply that the water/motor interface needs sufficient time for heat transfer to equilibrate. In my model I'm assuming that, in an imaginary sense, a "slug" of water enters the cooler, heat transfer/equilibration takes place, and then the water is discharged, and a fresh slug of water enters, and on and on. In my way of thinking ( and I got a D in Thermo in college BTW :crying:) , the length of time the slug stays in place is critical for maximum transfer to take place. In actual application, the rate of (continuous) flow is likened to the latency of slug enter/stay/exit. I think I'll go sharpen some props :Peace_Sign:

The problem with all of this is that people seem to be missing the fact that there is always water there. People are thinking that water has to be there for a certain length of time, not realizing that water is ALWAYS there. There is no time where the cooling system is without water...its constantly being cooled (If there is aeriation that is a completly seperate problem), either by cool water, or by warm water. Keeping the same water there longer and allowing it to heat provides no advantage. Heat energy is like anything else, it will naturally seek an equalibrium. The cooler the water, the faster the heat flows to it, period. Its just the way it is guys.

Brushless55
02-19-2011, 02:37 PM
WE're not trying to transfer heat here. Keeping the coolest water possible on the esc and can is the best way to keep the item cool. Allowing the water to warm is just allowing everything to warm. This is why when I run in ice cold water min the winter my components run cooler than in a warm pond in the summer.

Yes :thumbup1:


The problem with all of this is that people seem to be missing the fact that there is always water there. People are thinking that water has to be there for a certain length of time, not realizing that water is ALWAYS there. There is no time where the cooling system is without water...its constantly being cooled (If there is aeriation that is a completly seperate problem), either by cool water, or by warm water. Keeping the same water there longer and allowing it to heat provides no advantage. Heat energy is like anything else, it will naturally seek an equalibrium. The cooler the water, the faster the heat flows to it, period. Its just the way it is guys.

and Yes :thumbup1:

I think some are forgetting the fact that there is constant water contact with our systems (heat transfer)

785boats
02-19-2011, 04:02 PM
Well after absorbing the info on this thread from you guys that know heat exchangers, & after a long discussion with a new member at our club who also designs heat exchangers for a petroleum company, I have to say that I am a convert to the 'More is Better' philosophy.
He went into the laminar flow & turbulent flow with their corresponding heat transfer co efficients & even into the Reynolds numbers of the drag on the water.( he lost me there a bit) & lots of other stuff too, but the outcome is that I'm a convert.
But as others have said, if cooling is becoming too critical in a boat, the setup & prop choice needs to be looked at.
We've got to remember that heat is a by-product of the electrical work being done by the components. If they are being over worked they will break down. Cooling or no cooling. Just like us really
Cheers.
Paul.

TotalPackage
02-20-2011, 09:10 AM
All of its a funny debate coz as far as electrics are concerned when the motor is set up right it will like a little heat the batteries too. Whats critcal in my opinion is the esc coz it is the one thing that Truly performs better cooler. If the setup is efficient the motor should not go crazy on heat anyway. With electrics it seems to me all you cooling is the waste you need an efficient set up from the get go . Who cares how much you cool it if you real hot with the electrics the you real wasteful. Most people probably get too hot coz the dont have the headroom in batteries or the motor considering the WORK they expect. Ex. a 1527 is a popular motor for scale guys it surges around 4500 watts or 6 hp but in truth they should want maybe a 2215 with 8000 watts and the batteries to support it. We look at peak specs and say wow but they mean diddly squat you should want rms power anyway. Most of us including my self are fooling ourselves coz to support 8000 watts in batts and a motor that will produce it IS EXPENSIVE so if we can abuse a motor and put a water bandaid on it we do. Thats my take.

ReddyWatts
02-20-2011, 10:54 AM
I think the misconception that a slower water flow rate produces better cooling came from the auto industry. Engineers place a water restriction where the coolant exits the block. The water pump was placed at the intake of the block, this raises the water pressure between these to points and raises the boiling point of the fluid inside the engine. These engines run close to the boiling point and needed more margin. If water boils inside the block it drastically lowers the heat transfer rate.
Mechanics thought the purpose for the restriction was to reduce the flow rate and the MYTH was created. It is still believed by many.
We are not running close to the boiling point in our cooling systems and do not need to raise the pressure. Let the water flow freely for the best heat exchange rate. Do not slow it down to a trickle for better cooling as some have suggested.

H&MWill
02-20-2011, 11:05 AM
This thread is great everyday i read more and become more confused! Nah just jokin but it is interesting.

properchopper
02-20-2011, 11:55 AM
Part of the conflict between the "slower flow/faster flow" controversy here is the possible confusion in considering and differentiating between flow rate and latency in the cooling/heat exchange environment. While it's possible to vary the flow rate by controlling the variables of inlet/ outlet size, tubing size (diameter) and length, the input pressure ( which ties to the final flow rate when combined with these variables) should be viewed as a constant, given , let's say a WOT run. [ Yes, I'm aware that heat generation is moderated by throttle position, but to keep things simple, I'm leaving WOT as a constant in this example]. Hence, the only way to control flow rate is to play with these variables. I stand by my statement that the longer the cooling medium (water in the cooling jacket or SC tubes) stays in contact with the device to be cooled ( motor/SC), the more transfer of heat, e.g. cooling) will take place. Since my "finger on the motor" and "walking on hot coals" example failed to convince some on this, let's go to the good ole' french fry out the window experiment. Simply stated, a french fry held out the window for ten seconds will be cooled more than one held out for only one second. It cooled better when it was in the cooling medium/environment LONGER. Since, in the case of r/c boats we can only vary the heat exchange TIME by controlling the flow RATE, I have concluded that a slower rate allows for better cooling.

I have a simple experiment in mind to gather actual empirical data to support this using my leak tester apparatus, which connects to my kitchen sink faucet. Problem is that in five days I'll be racing five boats in five classes in AZ and my plate is currently full with final testing/tuning and the butterflies are starting to do the Macarena in my stomach so it'll have to wait :ohmy:

egneg
02-20-2011, 12:19 PM
Your french fry example is a bit off. The air going past it is not warmer do to restricted flow. For example if you hold one out the window and one near the window where there is less air flow it will take longer to cool than the one out the window.

properchopper
02-20-2011, 12:26 PM
Your french fry example is a bit off. The air going past it is not warmer do to restricted flow. For example if you hold one out the window and one near the window where there is less air flow it will take longer to cool than the one out the window.

The speed of the airflow near the window in your example is slower than the speed of the airflow out the window. If the speed of the flow is held constant
{ as it is in a boat setup once installed}, the TIME in the flow is the critical factor, at least as I see it.

keithbradley
02-20-2011, 12:29 PM
Since, in the case of r/c boats we can only vary the heat exchange TIME by controlling the flow RATE

This makes no sense, nor does the example about holding a french fry out the window longer...Regardless of flow rate, the time that the cooling media is exposed to the heat source is the same: A-L-L ---- T-H-E ----T-I-M-E. Slowing the flow rate does not do anything but raise the temperature of the cooling media.
The equivelant to stopping exposure of the french fry to cool air would be STOPPING the flow rate, not raising it.

I have to beleive at this point that this is just a matter of looking at things with a confirmation bias. I don't know how its not crystal clear, unless some people just want to hold on to their belief so much they refuse to look at this objectively.

egneg
02-20-2011, 12:37 PM
But the speed of the water flow isn't a constant. It is being slowed down by the size of the tubing or whatever. The constant is the volume of the water jacket or ESC tubes. The time it takes for a complete exchange of water takes longer with smaller tubing ergo higher outlet temps. The more times this volume can be exchanged in a given time period the more efficient the cooling will be.

properchopper
02-20-2011, 12:56 PM
In response to " Slowing the flow rate does not do anything but raise the temperature of the cooling media" : Maximally raising the temperature of the cooling media is what is desirable in this model. Where does the heat in the cooling media come from ? From the object to be cooled. The hotter the cooling media becomes from extracting heat from the object to be cooled, the cooler the object to be cooled becomes from this transfer and the more efficient the system is. Of course a closed loop system in a car doesn't hold to this, so closed loop systems won't be a good comparison, and of course the boat system is a total-loss configuration.

keithbradley
02-20-2011, 01:01 PM
Ok, here we go...

There is an elementary equation from basic thermodynamics that states that the rate of heat transfer (Q) equals the mass flow rate (M) times a Constant (the specific heat of water) times the Delta T (fluid temp out minus fluid temp in):


Q = M x C x Delta T

In other words, the rate of heat transfer is directly proportional to mass flow rate. If you increase the flow rate, you will then increase the rate of heat transfer. Since you cannot mess with mother nature, it is very naive to think it works any other way.

Assume the object being cooled inserts a constant rate of energy (Q) into the cooling system. Then, from the relationship above, increasing the mass flow rate must result in a smaller delta T because Q remains constant. This smaller Delta T (fluid out – fluid in) also means that the average fluid temperature coming out is somewhat lower even though the rate of heat transfer has not changed.

Now let’s look at the heat transfer from the source to the water:

The rate of heat transfer between two points is proportional to the temperature difference between those points.

In our case, this Delta T (not to be confused with the one above) is the temperature of the heat source minus the average water temperature coming out of the heat source. Lowering the average water temperature, as we did above by increasing the flow rate, means we have a little better heat transfer from the heat source to the now somewhat cooler water. The result is that the heat source becomes cooler.

This all says that if you increase the flow rate and everything else remains constant, you will decrease the heat source temperature.

NAIL ---------> COFFIN

properchopper
02-20-2011, 01:12 PM
OK, sounds convincing. Bottom line, I'm heading to the lake for some test/tune
H2O therapy. Have a good one ! :Peace_Sign:




Ok, here we go...

There is an elementary equation from basic thermodynamics that states that the rate of heat transfer (Q) equals the mass flow rate (M) times a Constant (the specific heat of water) times the Delta T (fluid temp out minus fluid temp in):


Q = M x C x Delta T

In other words, the rate of heat transfer is directly proportional to mass flow rate. If you increase the flow rate, you will then increase the rate of heat transfer. Since you cannot mess with mother nature, it is very naive to think it works any other way.

Assume the object being cooled inserts a constant rate of energy (Q) into the cooling system. Then, from the relationship above, increasing the mass flow rate must result in a smaller delta T because Q remains constant. This smaller Delta T (fluid out – fluid in) also means that the average fluid temperature coming out is somewhat lower even though the rate of heat transfer has not changed.

Now let’s look at the heat transfer from the source to the water:

The rate of heat transfer between two points is proportional to the temperature difference between those points.

In our case, this Delta T (not to be confused with the one above) is the temperature of the heat source minus the average water temperature coming out of the heat source. Lowering the average water temperature, as we did above by increasing the flow rate, means we have a little better heat transfer from the heat source to the now somewhat cooler water. The result is that the heat source becomes cooler.

This all says that if you increase the flow rate and everything else remains constant, you will decrease the heat source temperature.

NAIL ---------> COFFIN

hyrulejedi86
02-20-2011, 01:12 PM
I understand both points of view and in the end a combination of both theories is what's working here. But from what I see if Q rate of heat transfer then wouln't allowing the water to sit on the motor longer (resulting in hotter water leaving the system) increase Delta T resulting in a higher Q? The question is how much higher compated to increasing M instead.

keithbradley
02-20-2011, 01:30 PM
wouln't allowing the water to sit on the motor longer (resulting in hotter water leaving the system) increase Delta T resulting in a higher Q?

Simple answer, no.

Delta T in the equation will increase at a rate relative to decreased flow rate. The slower the flow rate, the LOWER the delta T will be between the heat source and inlet water, which lowers the cooling efficiency. What I'm saying is by raising the delta T in the equation, "M" will always be lowered at a greater rate, resulting in a Lower Q. It wont work to a greater degree becuase the delta T between the heat source and inlet water temps is less. Its not physically possible.

keithbradley
02-20-2011, 01:34 PM
OK, sounds convincing. Bottom line, I'm heading to the lake for some test/tune
H2O therapy. Have a good one ! :Peace_Sign:

Im jealous! Our "cooling system" is too efficient here in Michigan. Our water will be hard for another month or two.:crying:
Enjoy the california weather!:bowdown:

Joeyhatch11
02-22-2011, 08:48 AM
Is it worth going through the trouble of adding an extra cooling system that'll be directed to just the motor or ESC rather than having one system that flows through everything? I have a stock SV27 on the way that only has the rudder pick up and was going to add this system. Was even thinking of using the pick up as an outlet too, as mentioned in the top post. Thanks guys, Joe

forescott
02-22-2011, 10:45 AM
Is it worth going through the trouble of adding an extra cooling system that'll be directed to just the motor or ESC rather than having one system that flows through everything? I have a stock SV27 on the way that only has the rudder pick up and was going to add this system. Was even thinking of using the pick up as an outlet too, as mentioned in the top post. Thanks guys, Joe

I added the transom mount water pickup from the supervee nitro version to my sv a long time ago. The stock rudder pickup would lose pressure when turning the opposite direction of the rudder pickup hole, and flow was minimal. After I added the nitro pickup, the flow inreased dramatically and was drastically improved. Especially at low speeds!

Joeyhatch11
02-22-2011, 03:43 PM
If I go with the transom or under hall mount system, what diameter hose do I need? Thanks, Joe

SweetAccord
02-22-2011, 08:48 PM
the french fry analogy is the best analogy ever!

if you stick a french fry out a window while driving, eventually it will cool down. the faster you drive the quicker it cools down. so you either need more time out the window or more speed to get a cold fry. are we all in agreement here?



Not if it's a fry from McDonalds, they get cold really fast on their own! LOL

Brushless55
02-22-2011, 09:48 PM
Not if it's a fry from McDonalds, they get cold really fast on their own! LOL

:lol:

wraith
02-23-2011, 11:52 AM
Well, Im sure Ill get flamed for chiming in on this, since Im a newb and all...

I used to build water cooled presses for making chlorine tablets. They just have a 3/4in. NPT inlet and outlet for the water. Three of these things running 24/7 use a *!***!***!***!**load of water. We tried restricting the flow to use less water. We choked down the outlet on the unit to 1/4in. ID pressurizing the cooling system. All it did was overheat the unit.

Constant flow of cold water = better cooling

Brushless55
02-23-2011, 07:33 PM
Well, Im sure Ill get flamed for chiming in on this, since Im a newb and all...

I used to build water cooled presses for making chlorine tablets. They just have a 3/4in. NPT inlet and outlet for the water. Three of these things running 24/7 use a *!***!***!***!**load of water. We tried restricting the flow to use less water. We choked down the outlet on the unit to 1/4in. ID pressurizing the cooling system. All it did was overheat the unit.

Constant flow of cold water = better cooling

I wont flame
:popcorn2:

Joeyhatch11
02-23-2011, 08:06 PM
So what MM tubbing do I need for this water pick up system?

TotalPackage
02-27-2011, 04:26 PM
Simple answer, no.

Delta T in the equation will increase at a rate relative to decreased flow rate. The slower the flow rate, the LOWER the delta T will be between the heat source and inlet water, which lowers the cooling efficiency. What I'm saying is by raising the delta T in the equation, "M" will always be lowered at a greater rate, resulting in a Lower Q. It wont work to a greater degree becuase the delta T between the heat source and inlet water temps is less. Its not physically possible.

Sorry but what kieth is sayin is not opinion it physics and it doesnt change for anyone . Let it go keith coa all anyone has to do is open up a physics book;read it and prove it to themselves. Your wasting your time when people argue with basic physics. To be honest i think the smaller orafice at the end of the line ensures a constant flow with no air pockets and thats why it does a better job. And when it done right it wont be a trickle it will be a nice small pressured stream. The velocity increases inside the small orafice.

Simple you go two hoses one is 2 inches id the other is 1 inch id the same volume of water flows through the inch with more velocity than the 2 inch

drwayne
02-28-2011, 06:24 PM
Larger surface area of coolant contact to sink can increase total heat transfer from the system. If sink cannot increase coolant surface area ( bigger journals) the optimal solution would be to increase water volume through them.. increase flow.
An ever so slightly smaller outlet Vs inlet will reduce aeration of that flow from pickup to lower pressure(air) outlet.
Compressed water is not endothermic.. let it flow freely......


W

TotalPackage
03-04-2011, 09:52 AM
thanks doc

lincpimp
07-12-2011, 02:49 PM
After reading this I have a feeling some of the variables are being left out or over simplified.

A comment was made saying that the can of the motor could be cooled "too fast" for the internals to properly transfer the heat... I do not think this can be true. Heat travels in various materials at different rates. If you put a heat gun on a piece of al sheet and then on a piece of plywood you can see the difference.

So water will conduct heat at a certain rate. And the heat will also transfer in the water. Surface shape and texture (surface area) will also determine how much heat can be transfered at any specific flow.

So trying to make a blanket statement that increased flow may or may not cool better without taking into account the other variables just will not work.

I have a feeling that you could get the water flowing too fast to properly remove the heat, but that may be well past what the normal sport boater can do with his equipment.

Increasing the volume of water around the heat source will likely remove more heat, up to a point. And as you approach that point increasing the flow may help, but you have reached the limit of water cooling, and need to redesign the system.

Shooter
07-12-2011, 03:32 PM
We need an icon for "waking the sleeping bear".

Seriously though. You are right. MORE FLOW = BETTER COOLING. The point at which too much flow becomes a problem (due to flow separation and/or cavitation) is far beyond anything we would see in practice.

Fluid
07-12-2011, 04:03 PM
MORE FLOW = BETTER COOLING. The point at which too much flow becomes a problem (due to flow separation and/or cavitation) is far beyond anything we would see in practice.

Wrong. Water has a specific heat value and takes time to absorb heat. Turbullent flow is required for maximum heat transfer, but cooling water moving 'too fast' by hot objects does not absorb the heat as well as water moving slower. (That's why auto engines run cooler with a thermostat or restrictor in place instead of no restriction). But the heck with physics guys - believe whatever you want. I'll just keep having the coolest components in my boats! :cool2: :cool2: :cool2:



.

sailr
07-12-2011, 05:02 PM
The typical water nipples on the cooling jacket are only going to let the water move through so fast so why are we arguing about this?

RandyatBBY
07-12-2011, 06:21 PM
Fluid is right and that is always use a re-stricter hose on a J tube pick up. That is one to two sizes smaller on the outlet side.

Shooter
07-12-2011, 06:39 PM
Wrong. Water has a specific heat value and takes time to absorb heat. Turbullent flow is required for maximum heat transfer, but cooling water moving 'too fast' by hot objects does not absorb the heat as well as water moving slower. (That's why auto engines run cooler with a thermostat or restrictor in place instead of no restriction). But the heck with physics guys - believe whatever you want. I'll just keep having the coolest components in my boats!

Respectfully sir, we are not trying to HEAT the water. If so, then we would surely be interested in the amount of time the water sat in the cooling can (coffee maker).

Delta temperature is absolute king here. The best way to achieve delta T is MORE FLOW. No sense having warm water sitting in the can, it only reduces the delta T and the effectiveness of the system. The water is in constant contact with the motor. I work on systems like this everyday and graduated with a concentration in cooling systems. Not trying to change the laws of physics, just supporting them.

Regarding the automotive analogy, it is a closed system with increased complexity. The restriction was there to increase the pressure, thereby increasing the boiling point.

I'm only arguing now because I can't be boating!!! :laugh:

Doug Smock
07-12-2011, 11:28 PM
Someone needs to tell these guys that they are going about this bass ackwards.:olleyes::wink:
http://www.jrcbd.com/showthread.php?54534-Best-way-to-build-heat-in-engine
Good luck with that!!!:laugh:

Shooter you are correct. If memory servers a boiler heated to 15 psi will net ya approx 250'F.

Doug
Not arguing fellas. My stuff runs cool, even my gassers.

RandyatBBY
07-13-2011, 12:36 PM
Respectfully sir, we are not trying to HEAT the water. If so, then we would surely be interested in the amount of time the water sat in the cooling can (coffee maker).

Delta temperature is absolute king here. The best way to achieve delta T is MORE FLOW. No sense having warm water sitting in the can, it only reduces the delta T and the effectiveness of the system. The water is in constant contact with the motor. I work on systems like this everyday and graduated with a concentration in cooling systems. Not trying to change the laws of physics, just supporting them.

Regarding the automotive analogy, it is a closed system with increased complexity. The restriction was there to increase the pressure, thereby increasing the boiling point.

I'm only arguing now because I can't be boating!!! :laugh:

I think there is a point of transfer rate that must be found with the flow of water. I like a good stream of water shooting out the side of the boat. But if the water goes too fast it misses picking up all the heat it can. If too slow the water gets too hot and this is not good either. Balance is key.

Shooter
07-13-2011, 01:39 PM
You said it Doug. Backwards. They are looking at it from a 'heat the water' perspective (leaving the water in to absorb the heat). They are not one in the same. The coolest the motor can EVER be is the temp of the water coming out. More flow = coolest water in contact = maximum delta T = maximum potential for heat transfer OUT of the motor. Open system.

SailR - You're right, we don't have much control over volumetric flow rate (other than increasing the inlet and piping restrictions), so perhaps we should be concentrating on other things like the position of the inlet and outlet on our cooling cans, etc... but I like arguing with you guys because I know I won't end up sleeping on the couch afterwards!!! :roflol: he he he!!!

I'm first in line to take advice from Mr. Fluid as I don't have near the smarts nor the boating knowledge, but for this particular issue I have to respectfully disagree with him. :unsure:

Brushless55
07-13-2011, 08:37 PM
Hey it's ok, we all can give input as I don't think there realy is just one on these forums who know all :wink:

Jacked1
07-14-2011, 02:29 AM
Hmmm I would look at it like If you have a 200watt heater being sprayed with a fire hose or a 200watt heater being sprayed with a garden hose, which heater would be cooler?

If you sit down and do the thermodynamic calculations it is the mass flow rate (mdot in kg/s) multiplied by the change in enthalpy (delta h in joules/kg) of the water to get the Qout (in joules/s = watts). Sooo in both cases you are dissipating 200watts (Qout). So when your mass flow rate is increased (mdot) the change in enthalpy (delta h) is decreased. And since enthalpy is a function of temp and pressure, it increases with temp. So this means the more water flow the lower the temp for a given setup. Although to a point you stop seing any change in temp and there is no need for anymore water flow and you increase the likelihood of a tube bursting or a similar type of failure.
mdot * (h2 - h1) = Qout/s (<this equation is fact)

Either way tho you are still dissipating 200watts.

I love the discussion here. :)
Dr. Hearmanz and Dr. Muzumder would be proud.

keithbradley
07-17-2011, 12:15 AM
Wrong. Water has a specific heat value and takes time to absorb heat. Turbullent flow is required for maximum heat transfer, but cooling water moving 'too fast' by hot objects does not absorb the heat as well as water moving slower. (That's why auto engines run cooler with a thermostat or restrictor in place instead of no restriction). But the heck with physics guys - believe whatever you want. I'll just keep having the coolest components in my boats! :cool2: :cool2: :cool2:



.

Seriously? I thought we put this to bed guys. I'm not sure why this is so difficult to grasp. It's really a rather simple concept. I try to approach this topic without insulting anyone's intelligence, but it becomes difficult after a while. This is one of the oldest redneck theorys out there. I deal with it all of the time and have been listening to people mouth this nonsense for years.
Before anyone gets too uptight, Im not calling anyone a redneck. I call this a redneck theory because in my experience that's where it seems to come from in the automotive world.
LET ME BE CLEAR...There is only one type of person who believes that "cars run cooler with a thermostat/restrictor plate" crap: Someone who doesn't know cars from their rear end.
It's total nonsense. An engine will run coolest at the highest flow rate possible. Before you start to tell me that a car will run hotter with the thermostat removed, do me a favor and go remove your thermostat...let me know how that works out for you.
A thermostat is there to allow an engine to heat the coolant to a specified point. It serves no extra cooling purpose at all. It is an element of the cooling system that is in place to SLOW the cooling of the engine until a desire temperature is reached. I really don't know how this isn't obvious unless you just have no idea how a cooling system in an automotive engine works.
A restrictor can be used (though very uncommon and often unsuccessfully) to create pressure in a system where an insufficient (wrong) pump is used...but is much more commonly a product of stupidity. There are a lot of reasons people in low level racing use these but the primary one is ignorance.

Sorry to rant, but I work in this field and have worked in this field for a long time. It's tough to see the same statement made over and over despite how obviously wrong it is. This is not a subject that can be intelligently debated, because there is no intelligent debate. I thought I provided enough information to put the nail in the coffin on this one, but I guess it will just have to remain a popular urban myth to some people. There is no amount of reality that can can disprove some people's broscience.

keithbradley
07-17-2011, 12:35 AM
One other thing...
Where do people get this idea of a relationship between heat absorbtion and speed? People speak of this like it's fact, but it seems to be something that is just made up for converstation/arguement purposes. The idea has been brought up a number of times that water doesnt have enough TIME to cool...are these people saying that we are bending time and space with the rate of our cooling flow? I must be missing something here...
A gallon per minute, or 10 gallons per minute. Two different flow rates. Which one has more time? The only difference between these two is that the 10gal/per minute setup spends the minute with a larger temperature delta...

drwayne
07-18-2011, 07:33 PM
The one consistent thing I observe here, is variation.

Unlike nitro/gas engines, FE do not have need a 'running temp', where in fact cooler is better.

If your flow is slow.. heat ?
If your flow is fast ? .. go try.

end of day the advice in these forums is indicative the answers we seek... yet localized interpretation and application can present any type of cloned aberration. !

If yours works, stick with it.
If not.. experiment !

DocW
Adelaide
Au

riksorensen
11-14-2011, 10:07 AM
I bought one of these from ose for my sv-27/stiletto outboard conversion and I have to say this is the highest flowing water pick-up I've ever used! It almost looks comical how much water shoots out the side of the hull even at low speeds. I know its not the most hydro-dynamic piece, but there is no doubt that my esc is getting all the cool water it can handle. I will definitely be using more of these!!

http://www.offshoreelectrics.com/proddetail.php?prod=oct-ocsw

I just invented this....
It is a new and hopefully improved way of feeding your FEs with a high PSI water flow for cooling....
Before I explain... Here is what I know...
•More PSI = More Flow
•Greter Tube Diameter = More Flow and Volume (Provided there are no bottlenecks in the design)
•Faster and greater flow volume = Better cooling
•A colder motor = More power and less energy consuption
•Air in cooling/water lines is not great

Anyway... so I JB welded a 5/32 brass tube to the back of my HK Genesis rudder and wrapped it around and underneath...
It should offer awesome waterflow into the boat with very minimal extra drag as the tube is tucked behind the rudder..
Additionally, it should improve the flow of water over the rudder reducing drag as it will now have a rounded trailing edge as opposed to a square one...
This is just to compliment and run parallel with the rudder internal water inlet... It sits deep, will never (rarely) get air sucked into it and will yeild a super high water flow!!!
I will be using both... The new mod for the motor and the other for the ESC...
Im not sure if I will put 90deg fittings on top of the rudder or leave it with direct nipples in parallel...

6398263983639846398563986

riksorensen
11-14-2011, 10:13 AM
Agreed...
Its the gross delta that can dictate the rate of heat loss/transfer.
The bigger and more consistant the delta (as what you get with a higher flow) the better the heat transfer/loss.
The less and more intermittant the delta (slower flow) the less heat transfer/loss.

I won't go into a crazy amount of detail... Suffice to say, the greater the flow the better the cooling...

desmobob
11-14-2011, 11:56 AM
Sorry but what kieth is sayin is not opinion it physics and it doesnt change for anyone . Let it go keith coa all anyone has to do is open up a physics book;read it and prove it to themselves. Your wasting your time when people argue with basic physics.

Listen to keith... Q = M x C x Delta T

If you want to know more: http://en.wikipedia.org/wiki/Heat_transfer_coefficient

Take it easy,
desmobob

Rumdog
11-14-2011, 01:08 PM
That rudder is going to seriously effect your handling.

riksorensen
11-14-2011, 01:14 PM
That rudder is going to seriously effect your handling.

How so?
There is no change in surface area... the only change is the revision of the rudders trailing edge... i.e. less drag...

Im curious to know why you think it will "seriously effect" the handling?

Rumdog
11-14-2011, 01:33 PM
There is a reason rudder pickups are flush with the rudder. Yours will cause drag, and either lift, or pull the transom down depending in the rudder's angle and boats ride attitude.

riksorensen
11-14-2011, 01:38 PM
Wrong. Water has a specific heat value and takes time to absorb heat. Turbullent flow is required for maximum heat transfer, but cooling water moving 'too fast' by hot objects does not absorb the heat as well as water moving slower. (That's why auto engines run cooler with a thermostat or restrictor in place instead of no restriction). But the heck with physics guys - believe whatever you want. I'll just keep having the coolest components in my boats! :cool2: :cool2: :cool2:.
Fluid;
Just a note on the thermostat thing... They are in place to moderate flow to ensure the engine runs a consistant and desirable temp.
More importantly, it ensures that there is steady pressure throughout the system between the water pump, through the engine and its cooling ports and back to the backside of the thermostat.
Thermostats ensure that all areas of the engine get coolant and that the coolant does not follow the path of the least resistance and introduce air...
Engines without thermostats as you noted can and do run hotter. There are 2 reasons.
One - The temp sensor is located in the thermostat housing provididng a temp measurement of the coolant as it leaves the engine.
Two - Systems without thermostats are not as presurized and therefore some areas of the engine do not recieve coolant and therefore are not cooled the same as other areas. Cars that have thermostats removed tend to have temprature inbalances between ther cylinders.

How does this translate to RC Boat Motor cooling.... More pressure and more flow = Greater cooling...

RC Boat electric motor cooling is not restricted to being a sealed system so restricting the flow is detrimental to the overall cooling.
Additionally, as already mentioned... Electric engines run most efficient when cool/cold unlike nitro or gas engines that need to be at optimal operating temprature.
Essentially, the comparrison of car engine cooling in a sealed system to electric motor cooling in an open system is the same as apples and oranges.

They are not the same.... and based on your understanding, I don't think you will "just keep having the coolest components your boats."

No offence...

riksorensen
11-14-2011, 01:44 PM
There is a reason rudder pickups are flush with the rudder. Yours will cause drag, and either lift, or pull the transom down depending in the rudder's angle and boats ride attitude.
Interesting observation... I may just modify the design to satisfy the concern...

Stay tuned...

Brushless55
11-14-2011, 02:08 PM
I've seen this mod done before on another forum..
not sure what the outcome was...
but the rudder does need a sharp edge on the back

siberianhusky
11-14-2011, 02:45 PM
It pops up then vanishes every once and a while, I first saw it back in the 80's.
Would add a pile of drag between the pickup and back of rudder!
Unless you have the entire system sized properly you are creating a lot of drag from the excess water not being able to go into the tube due to restrictions farther up the system, like the esc cooler inlets. That massive amount of disturbed water is drag. Be like an underwater bow wave on the bottom of the rudder.
Would be much better with a much smaller diameter inlet tube.
Physics sucks eh?
Thats not even taking into account the trailing edge of the rudder.

riksorensen
11-14-2011, 03:45 PM
It pops up then vanishes every once and a while, I first saw it back in the 80's.
Would add a pile of drag between the pickup and back of rudder!
Unless you have the entire system sized properly you are creating a lot of drag from the excess water not being able to go into the tube due to restrictions farther up the system, like the esc cooler inlets. That massive amount of disturbed water is drag. Be like an underwater bow wave on the bottom of the rudder.
Would be much better with a much smaller diameter inlet tube.
Physics sucks eh?
Thats not even taking into account the trailing edge of the rudder.

Yes I agree, Physics suck and gravity's a bitch.
I will be moding it to be a more streamline inlet with less forward facing drag surface...
That said, I am curious to see how it performs (drag wise) when compared to this forums original post pics of "the best water pick-up ever"
I would contest that that type of pickup creates more direct drag, granted its not mounted on the rudder...
In any case, here is a really redumentary pic of my theorised drag reduction based on the rounded trailing edge of the modified rudder...

The third example may be a better design yet...64036

properchopper
11-14-2011, 05:01 PM
Simple propwash pickup. Easy to make, no parasitic drag, flows lots of water. :thumbup1:

64037

sanyijr
11-14-2011, 05:09 PM
Simple propwash pickup. Easy to make, no parasitic drag, flows lots of water. :thumbup1:

64037

Tony,

That is the simples, cleanest method yet! Clean install too!

Sean

Fluid
11-14-2011, 05:18 PM
A propwash pickup has significant drag, more than a rudder pickup, etc. Try putting your hand in the spray coming off a full-sized boat and then tell me there is no force pushing your hand backwards! The propwash is even worse because the roostertail spray is traveling faster than the boat is moving forward, and when it hits the pickup tube it causes lots of drag. This doesn't mean that a propwash pickup shouldn't be used, but if you think it is better because there is no drag, think again.



.

siberianhusky
11-14-2011, 05:22 PM
Sorry dude once again fluid dynamics shows that at the speeds we go a sharp square edge to shear the water has less drag, in something like a sailboat a rudder like yours is better as you maintain the laminar flow over the whole length and off the trailing edge.
Once the high speed water gets past the widest part of your rudder it loses its flow and becomes turbulent as it passes back along the width of the rudder, but it never loses it's contact with the rudder, thus more drag.
There is an air pocket behind the rudder with a square edge, the water shears off the sharp edge continues behind the rudder and rejoins back behind someplace where it doesn't matter anymore.
Once again physics.
Do about a half hour of heading on line and you will find all the info you could ever want about rudder shapes at different speeds.
The SAW guys have tried just about every rudder shape you could imagine in search of speed, square sharp edges = fast.

Rumdog
11-14-2011, 07:22 PM
So.. are you saying that if I'm in a full size boat, and stick my hand into the roost that it will slow the boat down?

sanyijr
11-14-2011, 07:24 PM
:roflol:

desmobob
11-14-2011, 08:05 PM
So.. are you saying that if I'm in a full size boat, and stick my hand into the roost that it will slow the boat down?

Of course. Like fluid said, not only are you creating drag, you're creating it in water that's moving faster away from the boat than the water moving over the rudder or across the hull. That's why some guys sharpen the edges of the brackets and parts that are in the prop spray.

When you stick your hand in the roost, don't you feel the force of the water pulling your hand back away from the boat? Your hand is attached to you, and you are attached to the boat... it's drag on the boat.

Take it easy,
desmobob

properchopper
11-14-2011, 08:15 PM
A propwash pickup has significant drag, more than a rudder pickup, etc. Try putting your hand in the spray coming off a full-sized boat and then tell me there is no force pushing your hand backwards! The propwash is even worse because the roostertail spray is traveling faster than the boat is moving forward, and when it hits the pickup tube it causes lots of drag. This doesn't mean that a propwash pickup shouldn't be used, but if you think it is better because there is no drag, think again.



.

I didn't realize this until I tried to lift myself off the ground by my bootstraps while wearing my mobius strip hat. I now stand corrected (and have both a backache and headache from that little experiment) :doh:

Jay, thanks for enlightening me :tiphat:

Rumdog
11-14-2011, 08:16 PM
lol. My question was more of a joke.
Do you really believe that. Geez, I'll looka at my speedo next time I'm in my boat and have my bud put his hand in the roost.

If I shoot a fire hose at a wall which way will it try to travel?

desmobob
11-14-2011, 08:31 PM
lol. My question was more of a joke.
Do you really believe that. Geez, I'll looka at my speedo next time I'm in my boat and have my bud put his hand in the roost.


Yeah.. I do believe in the laws of physics. Call me crazy. But I doubt very much your boat's speedometer has enough resolution to measure the tiny loss of speed from the drag of someone's hand in the roostertail. That doesn't mean there isn't any loss.

Take it easy,
desmobob

Rumdog
11-14-2011, 08:40 PM
In that case, the loss is pretty insignificant, huh?

desmobob
11-14-2011, 09:08 PM
In that case, the loss is pretty insignificant, huh?

Of course it is, but that's what we were talking about here: the differences in drag produced by different types of water pick-ups. When I used to roadrace motorcycles, I learned that a few "insignificant" things add up to be significant. If you're after every advantage, you pay attention to those little things. If you're just having fun, you don't always worry about them.

I'm a sport boater and I'm not concerned about how much drag my water pick-up is making. But I am interested in the physics of it, and think the discussion is interesting.

Take it easy,
desmobob

riksorensen
11-14-2011, 10:32 PM
Sorry dude once again fluid dynamics shows that at the speeds we go a sharp square edge to shear the water has less drag, in something like a sailboat a rudder like yours is better as you maintain the laminar flow over the whole length and off the trailing edge.
Once the high speed water gets past the widest part of your rudder it loses its flow and becomes turbulent as it passes back along the width of the rudder, but it never loses it's contact with the rudder, thus more drag.
There is an air pocket behind the rudder with a square edge, the water shears off the sharp edge continues behind the rudder and rejoins back behind someplace where it doesn't matter anymore.
Once again physics.
Do about a half hour of heading on line and you will find all the info you could ever want about rudder shapes at different speeds.
The SAW guys have tried just about every rudder shape you could imagine in search of speed, square sharp edges = fast.

Thanks...
This is really great info. I just finished wrapping up some research through the tons of info and was kinda shocked at the notion of a square edge in water reacting like this, but it makes sense now especially with how rc boat rudders sit both in and out on the water allowing the air pocket to exist...

I will re-form the trailing edge to be sharp and square...

Lovin the physics on this stuff BTW

Keep the discussion going

I will post shots of a revised design as soon as I'm done

Thanks again for the info...!!!

riksorensen
12-04-2011, 08:22 PM
Tapered bottom edge and a square back on it

Should work great!!!

65122
65123
65124
65125
65126

Am very open to any further thought or feedback before I polish it up...

thx

millzee
12-04-2011, 10:32 PM
will that create lift?

riksorensen
12-06-2011, 09:45 PM
will that create lift?
I am guessing yes,,, but thats why I have a dremel and a sanding block...

I will test it in May :( and see what it does...

It's all a guessing game...

Shooter
12-15-2011, 09:48 PM
I didn't realize this until I tried to lift myself off the ground by my bootstraps while wearing my mobius strip hat. I now stand corrected (and have both a backache and headache from that little experiment) :doh:


Now that's some funny stuff!!! Hat's off!! Unless it's this one.... :w00t:


65802

Jeff Wohlt
12-15-2011, 10:30 PM
Polishing anything running in the water creates drag or actually does not release the water as fast. Matte finish is better.

madmorgan
01-22-2012, 09:36 AM
the faster the flow and less restriction in vehicles lets say forklifts in which i work on all the time cools to much especially if we have to open the thermostat because its sticking and we have to order a new one we gut em and it runs to cool sometimes . its a big factor in the propane world because you need to heat the vaporiser err in lamens terms liquid propane flows into a aluminum housing and converts it into vapor and its then sucked into the engine to make it run. if that hot coolant passing through isnt hot enough then the diaprhams etc inside freeze up and it floods the motor because its putting liquid in instead of vapor i have to agree that the faster the flow with least restriction would be more cooling .

Cooper
01-25-2012, 08:52 PM
On cars you have a closed system, in this application you have an unlimited supply of a stable temperature water supply not glycol ( antifreez) thermodynamics- heat transfer, the speed of water passing through these systems is not interfering in this situation, more water passing through system is very simple, the more heat will be transferred , actually it not transferred, heat is always being absorbed by whatever is of a lower temperature, everything is dissipating it's heat into surrounding, (ultimately to absolute zero, when molecular movement stops) so in these boats more water is better, can't compare to autos

Cooper
01-25-2012, 09:49 PM
Hey here is the ultimate example for everyone, how fast is your hot 200 degree motor and speed controller going to cool down to the temperature of the water you are running in if you drip that same water over it say for one hour verses if you throw it into the lake? Is that clear enough? I agree with whoever said if you have the right set up this isn't really an issue

Punisher 67
01-29-2012, 12:40 AM
Seriously? I thought we put this to bed guys. I'm not sure why this is so difficult to grasp. It's really a rather simple concept. I try to approach this topic without insulting anyone's intelligence, but it becomes difficult after a while. This is one of the oldest redneck theorys out there. I deal with it all of the time and have been listening to people mouth this nonsense for years.
Before anyone gets too uptight, Im not calling anyone a redneck. I call this a redneck theory because in my experience that's where it seems to come from in the automotive world.
LET ME BE CLEAR...There is only one type of person who believes that "cars run cooler with a thermostat/restrictor plate" crap: Someone who doesn't know cars from their rear end.
It's total nonsense. An engine will run coolest at the highest flow rate possible. Before you start to tell me that a car will run hotter with the thermostat removed, do me a favor and go remove your thermostat...let me know how that works out for you.
A thermostat is there to allow an engine to heat the coolant to a specified point. It serves no extra cooling purpose at all. It is an element of the cooling system that is in place to SLOW the cooling of the engine until a desire temperature is reached. I really don't know how this isn't obvious unless you just have no idea how a cooling system in an automotive engine works.
A restrictor can be used (though very uncommon and often unsuccessfully) to create pressure in a system where an insufficient (wrong) pump is used...but is much more commonly a product of stupidity. There are a lot of reasons people in low level racing use these but the primary one is ignorance.

Sorry to rant, but I work in this field and have worked in this field for a long time. It's tough to see the same statement made over and over despite how obviously wrong it is. This is not a subject that can be intelligently debated, because there is no intelligent debate. I thought I provided enough information to put the nail in the coffin on this one, but I guess it will just have to remain a popular urban myth to some people. There is no amount of reality that can can disprove some people's broscience.

Well Put Keith , I am surprised this idiotic theory still stands . a thermostat is to regulate heat and not dissipate it . come on guys get real the more cold water pumped through the more heat pumped out .

drwayne
01-29-2012, 02:18 AM
I thought this thread was dead ?

:doh:

Stephavee
03-03-2012, 02:27 PM
Is it possible to have water cooling lines that are too big? I have some 1/4" od pvc tubing that is thin walled. Will it at some point be harder to push the extra volume of water through the cooling system and stat decreasing efficacy? More cooling water=more weight to push.?

TristanJones
12-13-2012, 07:45 PM
Stephavee, I think you will be surprised at the amount of water the rudder pick ups can provide at 40+mph. I run 4mm ID piping with stock genesis rudder pick up split into 2 circuits with a Y piece for motor/mount and ESC, the water still shoots about 1mtr (3ft) from the side of the boat when I run it above 30mph. I suggest adding an extra pick up if running 2 circuits instead of the Y piece to keep the speed of the water flow up, each time you increase the ID of the pipe U potentially slow down the flow of water, or decrease the pressure in the line.

Some very interesting info in here, can't believe there is any argument as to weather more flow of water over the cooling plate will work better or not.... Simple test, get a system that runs hot, hook up a 12v windscreen washer motor to it (3rd channel) and pump water through it with that. Log temps during an otherwise normal run but with the pump on, and then run again with pump removed and a restriction placed in cooling system of boat and check temps (if you even need further convincing after running with the pump on).... Guess what!!! It's cooler with the pump on. (do the test and show video to prove before you argue)
To me its common sense, but I've also been working with high performance turbocharged race engines for years. A good debate gets people thinking outside the box which is always a good thing. Hope I haven't come across arrogant here, definitely not my intention.

drwayne
12-14-2012, 06:10 AM
You have compromised the cooling effect of the pick up by splitting the flow pathway.
Fluid ( water, and likely Ray (http://forums.offshoreelectrics.com/member.php?34-Fluid) ) will always take the path of least resistance to the exit...
Here, limiting cooling effect on flow bypassed areas. ( I read an earlier thread where your motor was wickedly overheating )
Run one line from in to out...

burn and learn

DocW



Stephavee, I think you will be surprised at the amount of water the rudder pick ups can provide at 40+mph. I run 4mm ID piping with stock genesis rudder pick up split into 2 circuits with a Y piece for motor/mount and ESC, the water still shoots about 1mtr (3ft) from the side of the boat when I run it above 30mph. I suggest adding an extra pick up if running 2 circuits instead of the Y piece to keep the speed of the water flow up, each time you increase the ID of the pipe U potentially slow down the flow of water, or decrease the pressure in the line.

Some very interesting info in here, can't believe there is any argument as to weather more flow of water over the cooling plate will work better or not.... Simple test, get a system that runs hot, hook up a 12v windscreen washer motor to it (3rd channel) and pump water through it with that. Log temps during an otherwise normal run but with the pump on, and then run again with pump removed and a restriction placed in cooling system of boat and check temps (if you even need further convincing after running with the pump on).... Guess what!!! It's cooler with the pump on. (do the test and show video to prove before you argue)
To me its common sense, but I've also been working with high performance turbocharged race engines for years. A good debate gets people thinking outside the box which is always a good thing. Hope I haven't come across arrogant here, definitely not my intention.

dogg
12-31-2012, 09:45 PM
Actually that's not correct. It is both the amount of water AND the speed in which the water travels. All the water in the world may not properly cool if it does not spend enough time around the object you are trying to cool. This can be done by either restricting the outlet (typically done by the size of the hole on the outlet fitting) to slow the water down or restricting the inlet side to slow the water (the water slows once it passes the restriction) as well as reducing the amount. Controlling the rate of exit is very effective but you need to be careful with too much restriction at speeds over 90 as alot of pressure can build in the lines as a result. On my record trials boats I'll typically restrict both the inlet and outlet using both to achieve the desired temperatures. Using your car analogy going back to when I raced real cars, if you take out the thermostat completely the engine can and usually will actually overheat due to insufficient thermal transfer between the motor and the water. Companies like Moroso make restrictor plates with various size holes that fit in place of the thermostat to help regulate flow rates on race cars. The same goes for the water pumps, we used different sized pulleys to control the speed of water to improve thermal transfer. It is no different with our boats as it is possible to over cool as well as under cool. It doesn't matter if it's nitro, gas of FE powered, all have optimum operating temperature ranges and playing with the rates and speeds of the water will help you get there. :smile:

I'll probably cop some flak for this as I'm a newbie on this forum; but when it comes to heat transfer in cars, I would like to clarify something...
It is a totally different scenario to the one you are relating it to.
Firstly the overheating of the motors in cars (be them race or road) without use of the thermostat is NOT due to too much flow through the motor but due to the speed of flow through the radiator being TOO HIGH/FAST to effectively cool it before it re-enters the motor to begin the cooling cycle again.

It is however true with an internal combustion motor that too much cooling can cause increased wear and less efficiency with fuel consumption and overall performance.

With boats, be them model or full scale (bearing in mind the less efficient and higher wear of internal combustion engines that may result) the fact is that no matter how fast the flow of the water/coolant passing through the motor (water jacket in the case of an inrunner), the higher flow of water will always cool the motor faster and more efficiently.

Try cooling your motor with 80 degree water when its running at 130 degrees and it will only ever cool to minimum of 80.
Try cooling it with almost freezing point and the minimum possible it can get down to is the same as the almost freezing water.

The higher the flow rate, the faster the cooler water reaches the motor replacing the preheated water from the motors water jacket, resulting in better cooling period.

I hope I don't offend people with this frank description but I believe this to be true and am interested to know if anyone else finds fault with the logic. I've been in the automotive industry for almost 22 years and have had both road and race cars and this has been my experience and is the only logical explanation in my opinion.

Mike Caruso
01-16-2013, 04:50 PM
A propwash pickup has significant drag, more than a rudder pickup, etc. Try putting your hand in the spray coming off a full-sized boat and then tell me there is no force pushing your hand backwards! The propwash is even worse because the roostertail spray is traveling faster than the boat is moving forward, and when it hits the pickup tube it causes lots of drag. This doesn't mean that a propwash pickup shouldn't be used, but if you think it is better because there is no drag, think again.



.

2nd that yes what he said.

Mike Caruso
01-16-2013, 04:53 PM
I'll probably cop some flak for this as I'm a newbie on this forum; but when it comes to heat transfer in cars, I would like to clarify something...
It is a totally different scenario to the one you are relating it to.
Firstly the overheating of the motors in cars (be them race or road) without use of the thermostat is NOT due to too much flow through the motor but due to the speed of flow through the radiator being TOO HIGH/FAST to effectively cool it before it re-enters the motor to begin the cooling cycle again.

It is however true with an internal combustion motor that too much cooling can cause increased wear and less efficiency with fuel consumption and overall performance.

With boats, be them model or full scale (bearing in mind the less efficient and higher wear of internal combustion engines that may result) the fact is that no matter how fast the flow of the water/coolant passing through the motor (water jacket in the case of an inrunner), the higher flow of water will always cool the motor faster and more efficiently.

Try cooling your motor with 80 degree water when its running at 130 degrees and it will only ever cool to minimum of 80.
Try cooling it with almost freezing point and the minimum possible it can get down to is the same as the almost freezing water.

The higher the flow rate, the faster the cooler water reaches the motor replacing the preheated water from the motors water jacket, resulting in better cooling period.

I hope I don't offend people with this frank description but I believe this to be true and am interested to know if anyone else finds fault with the logic. I've been in the automotive industry for almost 22 years and have had both road and race cars and this has been my experience and is the only logical explanation in my opinion.

Correct!
anyone can look at http://www.stewartcomponents.com/Stewart_faq.htm
Mike

TristanJones
01-16-2013, 05:56 PM
Hi guys Ive just fitted these..

http://imageshack.us/a/img405/7946/2013011419001751.jpg
http://imageshack.us/a/img18/8964/20130114185951445.jpg

I was wandering the pro's and cons of using them, Ive been told to expect them to cause a 10kmh drop in speed form the drag they will cause, which Im not to worried about. Just want to be sure Im not going in circles creating more heat with the drag, than Im gaining in cooling ability with this type of pickup.

TheShaughnessy
01-16-2013, 08:48 PM
I would definitely file them down some, you don't need that much in the water to get good flow. Seems like a bad spot for them too. Have you ran the boat like that yet?

TristanJones
01-16-2013, 10:26 PM
No not yet, will try this weekend. Why do you say bad spot?? Have you used this position on the genesis hull and had issues??

Heaving Earth
01-16-2013, 10:34 PM
That's gonna create ALOT of drag

Cooper
01-16-2013, 11:00 PM
Correct!
anyone can look at http://www.stewartcomponents.com/Stewart_faq.htm
Mike
I'm not sure if even alot of top car guys realize what the thermostat actually does, the system is really based on the radiator and not the thermostat. The thermostat and cap are in relation to the amount of heat dissipation the radiator can preform at a given airflow. Bigger radiator more cooling. No forward movement of auto= no cooling. This is why they install fans, to help with cooling. The thermostat is designed to restrict water flow at certain temps (allowing radiator to dissipate more heat through air thermodynamicly). So it's not really addressed in simple physics because the components in use are limited. X amount of coolant in closed system dependant on x amount of cfm (airflow) all in a relative ambient temperature. Anybody know why ski boats don't have radiators? The lake they run in is there radiator. So please for those that still believe to slow restricted water flow will cool better just believe in physics, it works on keeping you from putting 50 volts through that 3500kv motor with a 15 amp esc doesn't it?

TheShaughnessy
01-16-2013, 11:37 PM
No not yet, will try this weekend. Why do you say bad spot?? Have you used this position on the genesis hull and had issues??

Oh for some reason I thought those were sponsons on a 3 point hydro. They should be fine there. Try them how they are and see what happens. I've only used that style on a super vee hull and ended up doing what stadium Yamaha described in your other post. Flush with hull at the front with just a lil nub at the rear. When they were longer I was getting weird handling characteristics

TristanJones
01-16-2013, 11:44 PM
Thanks heaps mate. Wish I had a hydro!
I just wanna run over 60mph even just 2 or 3 times then I'll run it on lower voltage if its unstable.

Mike Caruso
01-17-2013, 08:21 AM
I'm not sure if even alot of top car guys realize what the thermostat actually does, the system is really based on the radiator and not the thermostat. The thermostat and cap are in relation to the amount of heat dissipation the radiator can preform at a given airflow. Bigger radiator more cooling. No forward movement of auto= no cooling. This is why they install fans, to help with cooling. The thermostat is designed to restrict water flow at certain temps (allowing radiator to dissipate more heat through air thermodynamicly). So it's not really addressed in simple physics because the components in use are limited. X amount of coolant in closed system dependant on x amount of cfm (airflow) all in a relative ambient temperature. Anybody know why ski boats don't have radiators? The lake they run in is there radiator. So please for those that still believe to slow restricted water flow will cool better just believe in physics, it works on keeping you from putting 50 volts through that 3500kv motor with a 15 amp esc doesn't it?

Yes,
A lot of people still think water moving FAST through an ESC, motor or IC race engine does not have time to pick up the heat from the casting. They are wrong! I love the ski boat reference that should hit home. HA I still believe this nonsense came from the 60's when people Drag racing the 283 -327's would over-heat. Back then and for many years and yes even today still the fix was to slow the water pump down. It worked great but why? Water must be moving too fast right? WRONG The truth is the high RPM that the SBC could turn the stock water pump was too fast causing it to go into Cavitation. Now pumping the foaming water through the engine like A&W Root Beer Foam which did not cool the casting. Less water to contact the castings to remove the heat. This is what caused the over-heating.
Mike

danzigneg
09-22-2014, 02:17 AM
Good day all... Since there is no rudder with 4 water pick ups, I made this. Prop wash water pickup.
I bent the brass tube (ID 4mm, OD 5mm) using tube bender and the bracket were made using 3D printer.
The water flow was fast. But, the drag, not sure.
Only I'm not sure whether current inlet mouth is the at its best position or not.
Feel free to comment and suggest.
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