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Prop question for air boat...

I am preparing to construct an air boat to use on water/snow/etc. I have twin 550 Titan motors and an EVX esc from an E-Maxx truck and will use 2 6-cell nicd batteries. I plan to use both motors on the boat as a pusher model with above water rudders. The length of the boat will be ~28" with a beam of ~14". I am thinking since I am new to construction of boats, it will be made out of 2" rigid insulation foam with some kind of a panelling decking. This will allow me to "trial and error" somewhat cheaply until I really find out what will work with these motors. I've done a fair amount of research into this, but never could find a good source to what propellers to use.

Can anyone shed some light on the props I should use? My LHS is over two hours away and I won't be there for another couple weeks. I'd like to have an idea of what I need before I can get there.

Thanks a ton!

Pete_W.

Reply to
peter_walden
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Here's a place to start for information on swamp buggies and other air boats.

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Ken

Reply to
Ken Day

Cool, thanks! If anyone else is looking for the same info, here are a couple sites that were brought to my attention:

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Good info, and lots of math if that's your thing!

pete

Reply to
pete_w.

You should be able to run 8 x 4 or 8 x 6 APC E props on those motors. Watch your amp draw, especially with only one speed controller! The beauty of electrics is that you can mount a regular tractor prop backwards (concave side to the rear) and run the motors in reverse!

Good luck

Reply to
Jim Slaughter

| You should be able to run 8 x 4 or 8 x 6 APC E props on those motors. Watch | your amp draw, especially with only one speed controller! The beauty of | electrics is that you can mount a regular tractor prop backwards (concave | side to the rear) and run the motors in reverse!

Yes, you can run the motors in reverse ... as long as the timing is neutral or you adjust the timing after reversing them.

Motors last longer and perform better when the timing is advanced somewhat, and last much less long and perform much worse when the timing is retarded. Unfortunately, when you reverse a motor, you reverse the timing -- advanced becomes similarly retarted.

Many cheap motors don't let you adjust the timing, and because of this they come with neutral timing. But bigger/better motors might have the timing advanced somewhat ...

This is all only for brushed motors. Brushless, sensorless motors have the timing controlled by the ESC. (Sensored motors require manual timing adjustments, but they're also rare.)

Reply to
Doug McLaren

It's an specifically made esc that can handle 2 motors and 2 batteries.. it's a rather beastly thing! Cool, 8x4 is much bigger than what I thought I could put on it. Of course 8's would widen the beam a touch. Would 7x4's be much of a difference I'd notice? Either way, I'm starting to think with props that big, such a light craft and very tourqy motors.. this thing should rocket! Almost kinda giddy thinking about it!

Reply to
pete_w.

Go ahead and try the 7 x 4 props but you may want to have some 7 x 6's on hand too. You'll need some pitch to produce enough thrust to get the results you want.

Reply to
Jim Slaughter

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