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Is 21 inch cat hull to small for nitro

Old 04-14-2006, 04:07 PM
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YZF Desert
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Default Is 21 inch cat hull to small for nitro

I have a 21 inch long and 10 inch wide homemade cat hull that I originally made for electric, its slow as electric so I was thinking of nitro engine in it, the only small block nitro engine I have is an o.S. .18 but I think that the hull is to small for that big of an engine.
Old 04-14-2006, 05:31 PM
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Ron Olson
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Default RE: Is 21 inch cat hull to small for nitro

It might just work if you can get everything in there
Old 04-14-2006, 05:55 PM
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Default RE: Is 21 inch cat hull to small for nitro

I know in gas boats you dont need a clutch but nitro boats you probably need a clutch because of the high idle rpms, so were online would I find a clutch bell that has the collect in it for a flex shaft
Old 04-14-2006, 06:00 PM
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Default RE: Is 21 inch cat hull to small for nitro

huh?...most nitros do not run clutches, only the wicked angle and nitro vee that I have seen have them, the proboat stuff and aquacraft stuff doesnt use clutches, more gas boats have them than nitros...hope that helps you out, It will make it alot simpler also
Old 04-14-2006, 10:46 PM
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Default RE: Is 21 inch cat hull to small for nitro

If there is no clutch do they still idle through the water slow, and what size flex shaft would I use a 3/16. Also to buy a flex shaft, the collect, and a prop, about how much would that cost. All the hardware I can fabricate from aluminum. Im new to nitro boats but I own a couple of nitro trucks and have built a few gas boats, what percent is the center of gravity suppose to be on cat hulls. Also do boat engines use a heavier flywheel or would a standard rc car flywheel work, would a hevier flywheel make it idle lower or smoother through the water
Old 04-14-2006, 11:01 PM
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Default RE: Is 21 inch cat hull to small for nitro

A standard RC car flywheel will work. If you want them to idle real slow I would suggest trying to find one of the heavier flywheels out there.

Ryan
Old 04-15-2006, 07:39 AM
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Ron Olson
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Default RE: Is 21 inch cat hull to small for nitro

OK, let's go through your questions slowly.
You're going to need a 1/8" flex cable because of the cable collet that you need only uses that size. You can get a 1/8" or 3/16" stub shaft for the props depending on what size props that you'll need. A decent .18 will probably use a 3/16" shaft.
The CG on a Cat should be at around 27% forward of the transom.
I prefer boat flywheels such as the one made by O.S. but ithers from that size can work such as one from a Miss Bud.

Getting a cost together isn't easy. Don't forget a drive dog, prop nuts and cable grease. www.finedesignrc.com carries a lot of the parts that you'll need so you can at least look in there to get an idea of what you'll need.
Old 04-15-2006, 07:57 AM
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Default RE: Is 21 inch cat hull to small for nitro

ORIGINAL: YZF Desert

If there is no clutch do they still idle through the water slow...
Ron covered the other questions, so I'll just comment on this one. If you want a boat that can go slow and fast, and perhaps reverse, you may be better off staying with electric. It used to be that in general electric = slow toy and nitro = fast. With advances in batteries, brushless motors, and hardware this is no longer true. In fact, I believe the current speed records are held by electrics. Another advantage electric gives you for a small boat is the motors run much smoother so you can build a lighter hull. In the long run you might be better off upgrading the batteries, motor, and prop than trying to convert it to nitro.
Old 04-15-2006, 01:25 PM
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Default RE: Is 21 inch cat hull to small for nitro

I would like to leave it electric, but to make it a fast electric the good batterys good charger and a good motor and speed control would cost two much, what size nitro outboard do you think would work with a 21 in cat hull.
Old 04-15-2006, 02:00 PM
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Default RE: Is 21 inch cat hull to small for nitro

none, not any real r/c outboards, even a k&b 3.5cc(.21) outboard is very heavy to hang off the back of that, the only thing would be maybe get a .12 powered one off an old abc boat but they wernt much good either, itd maybe make 20-25mph tops with the .12 outboard,
Old 04-15-2006, 07:54 PM
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Default RE: Is 21 inch cat hull to small for nitro

Im still in the thinking stage of what to do with the hull I will have to find out some prices of things and I might make it nitro or keep it electric. I guess I could buy all the parts and try nitro and if it doesnt work out use the flex shaft and just go back to electric in it because I have the traxxas villian steel shaft and u-joint setup but it wasnt a gear reduction just prop turned the rpm of the engine. Thanks for the help

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