Prop question for air boat...

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peter_walden - 18 Sep 2006 17:47 GMT

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.

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Ken Day - 19 Sep 2006 03:11 GMT

>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
[quoted text clipped - 10 lines]
>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.

Here's a place to start for information on swamp buggies and other air
boats.
http://www.rcgroups.com/forums/showthread.php?t=369688&highlight=airboat

Ken

>Thanks a ton!
>
>Pete_W.

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pete_w. - 19 Sep 2006 16:32 GMT

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

http://www.rcfaq.com/RPMSTATS/propfaq.htm#Rules
http://www.findarticles.com/p/articles/mi_qa3819/is_200107/ai_n8978472

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

pete

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Jim Slaughter - 19 Sep 2006 23:13 GMT

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

>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
[quoted text clipped - 14 lines]
>
> Pete_W.

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Doug McLaren - 20 Sep 2006 00:25 GMT

| 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.)

Signature

Doug McLaren, dougmc@frenzied.us
He was deeply in love. When she spoke, he thought he heard bells, as
if she were a dustcart reversing.

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pete_w. - 20 Sep 2006 01:07 GMT

> 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!

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!

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Jim Slaughter - 21 Sep 2006 14:18 GMT

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.

>> You should be able to run 8 x 4 or 8 x 6 APC E props on those motors.
>> Watch
[quoted text clipped - 7 lines]
> tourqy motors.. this thing should rocket! Almost kinda giddy thinking
> about it!

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Model Forum / Radio Controlled / Air Models / September 2006

Prop question for air boat...