edf boat

[LarrysDrifter]

After seeing another members air boat build, I've decided I want to build a wooden boat 25"-28" long using a NIB UL-1 motor and Seaking 120 I have laying around. I also want to use an edf unit instead of an airplane prop. The problem is I don't know a thing about edf's. I see they come in different sizes, but don't know what size will be right for me. I don't need all out speed just something fun. Anyone have suggestions or tips? Help would be appreciated.

[Diegoboy]

Will the hull be a standard airboat "flat" bottom?

[LarrysDrifter]

I'm thinking so, as this is new to me. I don't want to buy a RTR hull and go from there. I'd like to try my own hull build. Did you have something in mind, Danny?

[Fluid]

EDFs have very low thrust levels and usually don't work well in boats. A typical air prop provides a lot more thrust, but matching the motor Kv to the required prop size the hull needs can be a challenge. I've built several nitro air boats, and a club member built an electric one years ago. Typical flat-bottomed boats have so much wetted area that they are relatively slow, although they can run in very shallow water, on wet grass, and they slide around a lot. My fastest was a Dumas Big Swamp Buggy with a 7.5 engine. It was a tunnel hull and ran in the low 40s. Similarly-powered flat bottoms were lucky to get into the 30s.


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[damfurst]

After seeing another members air boat build, I've decided I want to build a wooden boat 25"-28" long using a NIB UL-1 motor and Seaking 120 I have laying around. I also want to use an edf unit instead of an airplane prop. The problem is I don't know a thing about edf's. I see they come in different sizes, but don't know what size will be right for me. I don't need all out speed just something fun. Anyone have suggestions or tips? Help would be appreciated.

You may want to go with 2 55mm or 64mm edf's. Hobby partz has them but hobbyking has a whole section with fan blades, adapters, housings, etc. I don't know that a UL1 motor would be the best way to go. Usually the less weight the better. Edf's are also amp hogs so the smaller the motors are able to be the better because you won't need as big a battery.

[LarrysDrifter]

Thanks for the response. I might have to reconsider my propulsion system. If I use an air prop, is it common place to use an outrunner, or can I use the ul1 motor? If so, is a cooling jacket needed?

[Basstronics]

I know early on in my design stages someone mentioned going with an EDF. I decided against it as Im not familiar with them or their characteristics. So I went with something I understood better, a puller setup. I then got a few props to try which seemed sensible.

It appears you want to step up the size quite a bit. If you considered building smaller I would recommend that motor I got on 3S. I had to do some investigation but it appears 15K-17K is about the free rpm's of such setups.

[Fluid]

The UL-1 motor is probably not suitable, the Kv is too high. My personal experience with FE airboats is limited to a larger 6S cat version using a Scorpion HK2025 spinning an 11" prop. In- or out-runners will work fine. With the motor sitting out in the open behind the propwash, no water cooling is needed.

There are a couple airboat forums with guys having quite a bit of experience. Most are with nitro or gas power, but there are enough FE guys to make it helpful. For what it's worth, a Scorpion forum has a calculator which you can play with to determine the appropriate motor and prop for your application. It gives static thrust and amp draw and seems reasonably accurate. Since we can no longer post links to other forums all I can do is this:

RC Groups > Aircraft - Electric - General > Power Systems > Download Scorpion Calculator (SC)

You may have to search around a bit to find it.





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