Water cooling hole

[koolstrike]

Has anybody made the water cooling hole that is in the rudder larger? I noticed today when running at very fast speeds that the water was exiting the side port hole slowly, my guess is that the boat is going so fast that it cavitates past the entrance port.

Also, what is the max temp my 5000mAH battery should run at, after running today the pack had a 140 F temperature.

[Rex R]

140F while a bit warm...it sounds about right, if you ran most of the pack out. you should consider 150F to be an upper limit. I've heard of people enlarging the hole(water pickup), you'll want to do so a little at a time.

[Doby]

Install a metal pickup tube on the transom and stop using the rudder for picking up water cooling. I use a brass tube about 1/4" below the transom and water files out the side about 2 feet !

[Fluid]

While water flying two feet out the exit hole looks cool, it is probably compromising the cooling effectiveness of the system. Water needs some time in contact with the hot parts to pick up the heat, and if the water runs through the system too fast, heat transfer will be too low. As long as you can see some flow of water out the exit, you are probably fine.

Picking up water in the rudder is less draggy than an external pickup tube placed in the roostertail. The water coming off the prop is going faster than the boat is, so the "push" against the tube is very high making high drag. The drag penalty with a rudder pickup is very low.



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[Doby]

[QUOTE=Fluid;37501]While water flying two feet out the exit hole looks cool, it is probably compromising the cooling effectiveness of the system. Water needs some time in contact with the hot parts to pick up the heat, and if the water runs through the system too fast, heat transfer will be too low.


Motor and speed control always never above ambient on even the hottest day. Give me volume of water any day.

[G Doggett]

While water flying two feet out the exit hole looks cool, it is probably compromising the cooling effectiveness of the system. Water needs some time in contact with the hot parts to pick up the heat, and if the water runs through the system too fast, heat transfer will be too low. As long as you can see some flow of water out the exit, you are probably fine.

Picking up water in the rudder is less draggy than an external pickup tube placed in the roostertail. The water coming off the prop is going faster than the boat is, so the "push" against the tube is very high making high drag. The drag penalty with a rudder pickup is very low.



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I restrict the water flow on my gas boats to improve cooling and use rudder pick ups.
Graham.

[Ctonez]

larger rudder hole, OSE cooling jacket, large bore outlet, and bigger ID tubing made the temps in my SV much lower.
rarely do I see temps above 110.

[Fluid]

Sigh. You can lead a horse to water......



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[Doby]

Sigh. You can lead a horse to water......



.

.....But if he drinks to much, the horse will run hotter?!?!?

[Eyekandyboats]

you can always push him in.. that should cool him off

[Chop]

This is my understanding of the thermodynamics at work here:

Any change in flow is insignificant, as long as you don't have steam coming out of the exit hole. Basically if you run water through a cooling jacket at 5 ounces per second you will get x amount of heat transfer. If you run it through at 10 ounces per second you will still get x amount of heat transfer, but the change in temperature of the cooling water will be half as much.

The amount of surface area of the cooling jacket would be more critical. This is a “six of one, a half dozen of the other” type of argument.

[Doby]

Hey, sounds as good as any other theory . Whatever works.

[Doby]

you can always push him in.. that should coll him off

I love it

[Mich. Maniac]

larger rudder hole, OSE cooling jacket, large bore outlet, and bigger ID tubing made the temps in my SV much lower.
rarely do I see temps above 110.

Could you share how you did this exactly? dud you also drill vertcal part of rudder?

[Ctonez]

Could you share how you did this exactly? dud you also drill vertcal part of rudder?

I'd use a round file to remove burrs or obstructions in the vertical hole, but I find it to be plenty large.
To enlarge the rudder blade hole, (btw - this isn't originally my process, I asked the same question you did and got this info...) use a dremel with a pointy grinder stone...the greenish one and CAREFULLY enlarge the rudder inlet only a slight bit. you could probably use a drill bit, but the possibility for screwing it up is much higher.
use the round file to remove any excess bits/shape the opening, and blow through the vertical hole/outlet to make sure it's all cleared.
My stock rudders came with really small inlets, almost "shrouded" a bit by the aluminum, my intent was to make sure this didn't obstruct any flow to the already smallish opening and then I really only opened it a little more than stock...I can see water coming out of the outlet when I drive the boat by.

I did that with both my SV's (OSE jackets on both as well...I find my boats stay drier and cooler with these), and in my Pmono version (Ammo/Bar125) I use the yellow tygon fuel tubing, but until recently used stock tubing on my stock SV. I could feel much more resistance when blowing through the stock boat...I have since gone to larger ID tubing on the stock boat as well. Gimme a few hours and I'll post some pics...