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Mount engine on top

Old 03-18-2010, 09:43 AM
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P-Y
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Default Mount engine on top

I have a Hobbistar 60 and I'd like to mount the engine (OS 61FX) on the top of the wings. So I'm looking for information about building that kind of "nacelle".
I did search on RCU but I didn't find anything.
Any help would be greatly appreciated.
Thanks.


PY
Old 03-19-2010, 05:31 PM
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Default RE: Mount engine on top

Are you converting it to a flying boat format?

The pitching torque from the high thrust line will require you to angle the thrust line upward at quite an angle. Also if you can set it up so the prop comes down below the wing leading edge in front of the windscreen that would assist in keeping the angle from being too extreme. I'd suggest starting with around 6 degrees upthrust and allow for adding more or going with slightly less. By having the engine basically located directly over the leading edge in this manner it will also reduce the amount of nose weight you'll need to add to make up for shifting one of the model's heavier components back that far.

Your wing will need to be held on with much more than rubber bands in this case as well. And for this size of engine you can forget about just a glider like rubber banded on mount. Or at least you'll need some postive manner of keying it to the fuselage to avoid it shifting it's position so the thrust line and wing remain stable and locked in place at all times. The nacelle will need to be built directly into the wing to ensure the best strength and stability. This pretty much means building a new wing since modifying the one you have will be just as much work or more than building a new one. It's not like you can just peel back some covering and glue the pylon to the wing. The engine generates too much power and vibration for that to be an option. It needs to be something that ties into the wing spars and leading edge more properly. Well, perhaps it could be adapted but it would require cutting away much of the top surface sheeting so plywood joiners that connect to the leading edge and spars can be properly installed. These joiners would extend up into the pylon for the engine naccelle so the engine mounts or firewall are connected down into these main wing members. Otherwise I'd be worried about the pylon just tearing off if only glued to the sheeting.

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