Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Working Vessels => Topic started by: philgg1946 on September 16, 2021, 08:20:27 pm
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I've just put cooling to my brushless motor, on my Raf launch, I tried it running at full speed on Etherow lake but the water wasn't coming out of outlet pipe ,would putting a bigger propeller on prop shaft increase water flow or is there a trick of the trade Ineed to know about, the prop now is a 3 bladed 35mm brass blade. help Phil
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Prop will make no difference. Would be good to see some photos of your setup, first step is to blow through all the lines to ensure there are no blockages
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Thanks mate, I was going to get a bigger prop so youv've a least saved me that avenue, I'll put pics up tommorow , I did blow it through ,so there are no blockages and I pumped water through the pipes . Phil :-)) :-))
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Is the pickup tube close enough to the prop arc?
Regards Ian.
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Hi lads I thought maybe the pipe is to high running from the pickup to the motor, I took some pics Phil
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I hope the pics are now up
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Looking at your pics the inlet is too far back and too high. It should really be close behind the prop where it is directly in the prop wash.
Jim
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Cheers for that Jim, it was boiling hot when I started this project ha ha :-)) :-)) , I'll move it and see what happens Phil
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If you don't get a water stream from the outlet, with the boat in the water and restrained, and the motor running, the inlet is in the wrong place. It might be called a water "Scoop" but it rely s on the propeller pushing water through it.
Regards Ian.
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I moved the scoop to just behind the prop and it still didn't work, my mate looked at the scoop position after and said it needs to be to the left and behind the prop for a right hand prop as that's were the water is forced, the other side with a left hand prop ie looking at the prop from the rear/ I'll be back in a few days CHEERS Phil {:-{
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A prop pushes water rearward THROUGHOUT its rotation no mater which pitch UNLESS it's going backwards in which case it sucks. O0
Regards Ian.
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Not sure why this is in working vessels R&D but I'll ask the question:
- What motor are you running to need water cooling. Same for the speed controller?
- Usual caveat that a well matched motor and ESC very rarely needs water cooling in most applications outside of racing
- I have never used your bolt through type of water scoop. I always thought it looked more like it did noting but create drag or charge a customer 5-6 quid when all that was needed was just a short section of tube. My Perkasa and other models back in the day before I learned they weren't necessary had a simple brass pipe merely poking through the bottom skin, nothing more protruding than an edge cut at 45 deg to the bottom skin so total protrusion of something like 3 or 4mm and probably not that near to prop wash . Forward motion over about everything more than 1/3rd throttle was just enough to start movement of water
If you really need this cooling circuit have you tried disconnecting the outlet and running the boat with the pipe just sticking up through the hatch? Without seeing the model or knowing more details -I struggle to believe it needs that big scoop and power sapping drag on one side of the boat, or why it wouldn't work if the pipework is clear.
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Wonder why Mersey Marine and Rip Max used brass tube with a curved end? That lump of plastic looks like you would need a water pump to pull water into it. If you rotated it so the hole is facing backwards, the fitting would make a good rudder.
Regards Ian.
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I thank you for your input all things being equal I'll now see what I can do with the advice given, and good advice to, Phil