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Just hit the lake with my winter project. (pic attached) Obviously not a racer, 1/8 scale of my 18' fishing boat. It's 28" long and 6 lbs. complete, CG at 40%. Has a functional RC fishing reel with a cutoff when I'm not using it. Being my first boat, I had to guess a lot on the components to use. Sure learned a lot in a hurry the other day. First, I have to revise the drive and prop trim to get it to plane. Maybe I can get CG below 40% by moving the motor a bit. Running 3S Lipo 5000,Octura X438 prop and HK 3660SL 3060kv motor. I smoked a Seaking 120 esc in 200 feet. The caps popped and it won't even beep when I turn it on. Put in a HK B200A esc which lasted 10 minutes before the boat slowed to a crawl. LVC is set right and battery was still at 11.4 v. It still beeps OK and runs the motor fine with the drive unhooked. Any load at all and it quits. ie. just hooking up the drive. Motor turns smooth but I can't tell what failed. I'm trying to get this boat to run fast enough to be a bit of fun at full speed but not necessarily as fast as now. I'd really like to be able to run at 2mph for trolling as well. From what I've read, it might be hard on things trying to go slow. I'm going to start over on motor and esc but I really need to find out what you experts would use. Any input is appreciated.
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That's a nice boat looks great!!
Somebody here should be able to help you here with the right set up. -
A beautiful boat! But a totally inappropriate motor. The Kv on that motor is way too high for a sport boat and especially one with a fully submerged drive. You were probably pulling well over 200 amps, no wonder the ESCs quit!
I'd suggest getting a motor the same size, but with a Kv around 800-1000 rpm. This will keep the prop speed and amp draw down while still giving scale-like 15 mph top speed. It has been awhile since I built a scale boat but the drive requirements are way different from a typical FE race boat.
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Thanks Fluid
Any suggestions on Brand?Comment
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Forgot to mention that it looks like I have cooling flow but on the long run, the motor and esc got warm but not too hot to touch. Probably just over-amped?Comment
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It is tough to find a motor with that low Kv except for helicopter motors. The two below are in the ballpark, but I have zero experience with the Turnigy - others like them. The Scorpions have a good reputation. This is still a guess as far as the 'best' motor for you, but the two should be pretty close. You can adjust amp draw and speed by playing with props.
These are both outrunners, meaning no practical watercooling other than a water cooled mount...but the Scorpions at least can take a lot of heat. I run a Scorpion 4025 in my 34" 6S cat without watercooling and it is fine. Keep all wires away from those spining magnets!
http://www.hobbyking.com/hobbyking/s...dProduct=11143
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winter project
The esc can be fixed on the caps by removing the existing ones and putting 5-470 35 caps from local electronic shop since your in BC. You mention resetting the stuffing tube; have it come down and then bend it so it is parallel to bottom of keel and have prop about 1/8" ( tip of prop ) from bottom for boat to ride almost flat. Just solder brass to stuffing tube and up thru bottom of hull. The brass for stuffing tube can be made to look like a " T " and inserted from inside the boat down to stuffing tube. Now to really make the T stable would be to solder a brass piece crosswise with basswood so it won't go anywhere. The brass crosswise would fit into basswood like an insert. These are suggestions only. Cooling for outrunner can be bought. Now a computer fan to suck air from outrunner or a fan with low amp draw would help when running slow. Beautiful boat. 4074 @1050 kv @ 74.00 is alot of money. The trouble with inrunner motor at slow speed requires a pump to pump water for cooling the can and also for a outrunner with cooling at the m/mount would also need a pump. Now if your going to have to pump water anyway, why not get the 880 outrunner ( Turnigy ), Fluid suggested and also buy a cooling water mount for the 880. There's afan for cooling the rear end. What Fluid suggested about props for speed is spot on with real small props for low speed and bigger props for higher speed. The higher speed can use 14.8 40c lipos and 40c 2s for low speed. All you would have to do is change lipos and props. That way, you can have your cake and eat it too.Last edited by FRED; 03-29-2011, 12:26 AM.Comment
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Are leopard motors any good? 4074 comes in 1050kv. I assume that I'm going to need a 180 esc if I don't get mine working.Comment
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leopards are good but i don't think you need anything special to run your boat.Comment
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in fact i would just get one of these for $25.00 i used this brand before and they work fine .... use a good old cooling coil around it and it should be fine.
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I'll be cutting out the stuffing tube to relocate/trim the prop. At the same time, I'm going to try to move the motor back to improve the CG. The inner end of the tube is currently just above the static water level. Moving the motor back will necessitate more bend in the tube. How much bend is acceptable before drag becomes an issue? Or is there a good way to seal the shaft so the inboard end can be lower? Any suggestions are appreciated.Comment
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Just trying to cover all the bases. If I have 15" of 12 ga. between batteries and esc, will it hurt the esc? Read somewhere that wire length is important but figured that 12 ga would be OK.Comment
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I'm trying to remember the lenght of wire on esc/motor end; i think it should be fairly short but don't quote me on that. Now esc to batteries was brought up but that was along time ago.----*** Fluid who frequents this site can reflect on that but i think that is too long. I see your reasoning on this as 12 gauge is thicker and carry more juice. There's an equation on line loss here but does it effect rc equipment. Someone tried 10 gauge and found it to be to stiff like in boats need the flex. Someone will chime in.---Ok, on lenght motor wires that go to esc, keep fairly short and as far as 10 gauge compared to 12 gauge isn't much difference but shortening is best and sounds like you did your homework.Last edited by FRED; 04-08-2011, 09:02 PM.Comment
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Cutch;
Start the stuffing tube bend sooner so you'll have a gradual slope and add support for stuffing tube. While you're at it add an oiler about 2" down from end of stuffing tube ( motor end ). The angle of motor won't hurt anything as long as alignment is spot on. Whether you can have it lower or at waterline with flex cable is questionable. I know what i would do then would be to go straight shaft, but that's me. Pictures would sure help for the inside.Comment
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