Silicone tubing question

[tlandauer]

"Smaller diameter will increase velocity and pressure. However that does not mean more flow (volume). Small tube equates to high pressure low gpm and larger diameter equates to higher gpm at lower pressure. The simple answer is higher velocity (small tube) will move the water faster. Maybe too fast for it to transfer? I don't know. Brain hurt yet?"

That's what puzzles me. I think this afternoon to give my brain a rest I'll work on simpler stuff : Reconciling the Palestinians and Israelis, curing the World of all known diseases, and learn how to play the accordian.

I like to learn to build a boat , that would be my wish.
If I may offer my observation: A lot have to do with the rudder pick-up. If the rudder pick-up has small dia., then using a larger tube really slows the flow, in that case there won't be enough velocity to fill up the whole system quickly to promote good circulation. ( WATER DOESN'T EXIT UNTIL THE SYSEM IS FILLED)
Since volume is certain amount in a given time. I have come across certain rudders that are smaller than the Speedmaster verities and using a larger tube slowed the flow to the extend that I wasn't able to see the water shooting out of the out let. ( Because I have poor eye sight and have to slow the boat down to see, by then water is only trickling out) .
The opposite is that if the pick-up is relative large and using too small a dia. tube will certainly increase pressure and hence the velocity, but at the expense of flow volume. So it is a balance of these two factors for me.
I am not going near the "heat transfer" issue. BTW.

[jetskier]

more flow=more cooling. at work, we do a test whenever we size a radiator/heat exchanger for a new engine that we're gonna use for our machines. we use water not antifreeze, we physically block open the thermostat to get the max flow and we run the machine full load. for example: ambient temp is 80F, engine temp is steady @ 165F full load, and engine overheat temp is rated @ 230F the formula to fine out at what ambient the machine can survive at full load is 230-165+80=145

[T.S.Davis]

Plus we are not talking about a pump, it's water ramming into a pickup...and that brings to another question. how much flow can the pickup intake at max speed.

Depends on the size of the opening and the size of your tubing.

Friction loss is a matter of physics. Your source of pressure makes no difference. Water pick up, pump, gravity tank, turbine. The physics are the same once your into the tubing. That could be calculated. I think where it gets tougher is in the cooling cans, the speedos, the additional twists and turns in the system. Difficult to quantify that.

I think you hit it on the head. Lose zero sleep over it. Did I see water? Yep. I'm good!

[properchopper]

To prove that I'm not simply jumping on the mental pudwhacking bandwagon regarding the dreaded cooling flow debate for my own amusement, I'll show some pix of what I'm up to as we speak - a single pickup setup where, thanks to what appears to be confirmation that larger conduit [fittings + hoses] is the way to go, here's how I've used the larger 5mm fittings on the rudder (and on the ESC which I had to narrow to fit with opposed 90deg. thingies) AND a large through-hull entry tube.

I'll also concur that it all starts with the rudder pickup inlet. I have one boat where one channel (to the motor) has very little outflow which hadn't occurred before with the same motor and rudder on a previous boat. I modded the inlet; haven't tested it yet.


[BTW Terry your new red cat should be named "Disaster" [ say it s-l-o-w-l-y - you'll get it ]

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[properchopper]

Large fittings, 4mm hose, short tubing runs. No way to get motor jacket outlet on top ( I'd have to pull jacket off, plug & re-tap but the CC jacket is ON FOR GOOD; guess I'll live with that.

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Angled outlet keeps wind shear from obscuring output flow at speeds over 200mph


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[tlandauer]

Tony, do these fittings screw right into the jacket? Looks like they allow much freer water flow than the adjustable fittings on some of the HRC jackets. That fitting on the rudder is awsome! That settles the argument: size DOES MATTER!!!
Where do you guys get 4mm tubes, I order from Tower Hobbies , and the DuBro brand doesn't tell in metric sizing, is 5/32 considered 4mm?
Thanks in advance,
Tim

[martin]

5/32" is the equivalent of 4mm.

[properchopper]

Tim,

Depending on which fitting is used, and which device is getting the fitting, it's best to have on hand a 10-32 tap (Aeromarine 90 deg. fitting) and a 5mm tap (5mm 90 deg fitting)

Either way I VERY CAREFULLY apply some JB Quick on the threads before mating to not only create a watertight seal but to hold the 90 deg fitting in place. The 5mm 90 deg fittings don't have a lot of thread depth.


HRC, Aero, and 5mm L to R ; top to bottom

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JB on rudder joint

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While I'll agree, as you said, that "Size Does Matter", my Ex had another complaint and gave me this sticker :

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Truthfully, in light of the copious amount of discussions on this topic, I've (1) been pretty much convinced that more flow is better even though there's not been any empirically valid scientific data collection done with FE boats that I know of, and (2) feel that no amount of watercooling, however optimized, will be a panacea for a bad setup.

For now, I'll just go as big as practical ; it's no big deal during the build process.

[larryrose11]

I'll also concur that it all starts with the rudder pickup inlet. I have one boat where one channel (to the motor) has very little outflow which hadn't occurred before with the same motor and rudder on a previous boat. I modded the inlet; haven't tested it yet.

[ATTACH=CONFIG]99699[/ATTACH]

the rudder mod, I like it!!! How did you go about it?

[properchopper]

the rudder mod, I like it!!! How did you go about it?

I'll try to explain - Took a tiny drill bit, coated it with grease and laid it in the existing groove/channel. Flowed some JB Quick carefully on it and as it began to set I used an X-Acto to form the blend outline into the rudder. After cure, I gently twisted/pulled the drill bit out. Did some final outline trimming with the X-Acto.

[tlandauer]

Tony,
Thank you for the detailed pictures and explanation, I had no idea that the 5mm fittings have such shallow thread depth, I think the advantage of such character is that it will not protrude into the jacket too much. I had bulged my caps on my tunnel ( VS-1) because I screwed in too much and it actually was biting into the motor can!! Didn't know until I had to change the jacket and the jacket won't budge!
and YES! As proof of my divorce, I was awarded with a few stickers and one of them is quite like yours. I now consider it an ultimate honor knowing that I am in this league.

[madmikepags]

Hey Terry stop talking about the size of the HOLE and the size of your TUBE???!!! WTF this is a family show.

OK heres the REAL explaination: The wider the tubing the more water flows against the walls of the tube causing more friction thus causing the water to increase in temperature just by flow. The faster you go the hotter the water gets. You must also take into account the coefficients of static and kinetic friction and multiply by the volume of water/unit of time of contact to the heated surface times the velocity of the water. Then divide that number by the total surface area of the inside of the tubing and the outside can of the motor and the inside of the cooling can. Then cross multiply that with the density of the motor cooler/the change in temperature from the beginning of the run to the end of the run (in Kelvin) times the density of water, also you must take into account that the entire system is under pressure thus increasing the density of the water flowing through the system. These are fairly simple physics calculations????
If all else fails, put small tubing on and run for a minute and take a temp reading, then put big tubing on and do the same thing!!! I did it and there was a difference of about 3 degrees cooler with the larger tubing, I did this back in 2006 when I was wondering the same thing. Basically the inlet and the outlet are the limiting factors, the size of the tubing doesn't make much difference.

[larryrose11]

True, ther cooling system will be constrained by the smallest diameter of the system. Tubing size wont make a difference if one of the fittings has a tiny opening.

[T.S.Davis]

haha Mike, that's the best way to know.

The size of the tubing will make a difference. Again, physics. Friction loss through a tube changes based on diameter at a given flow. I do these kinds of calculations every day. You can pinch the tube and slow the flow but the friction loss is still different in different sized tubing. Friction loss at the pinch may be higher than all of the tubing.

There's also a coefficient of friction known as a C-factor. Think of it as a smoothness factor. That could vary slightly based on which tube you buy and effect that actual flow in gpm.....oh....ow.....my brain.......think I may have broken something.

Best bet, do it Mikes way.

[madmikepags]

yes but r we using the Cs (staic friction) Ck (kinetic friction) I always messed that up in Physics??