Best water pick-up ever!

[don ferrette]

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.

[forescott]

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]

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.......

[westbeach]

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.

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.......

[Diegoboy]

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]

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]

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.......

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

[Diegoboy]

Check out THIS book, Start on section 13.1 or Page 344

[egneg]

Also a higher flow rate will cause more turbulence increasing the rate of heat transfer.

[don ferrette]

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.

[keithbradley]

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.

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?

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]

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.

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]

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]

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]

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.