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Post by coyote on Aug 19, 2013 11:14:02 GMT -4
How does one calculate nitro/gas engine size for weight?
I know that on electric side there is a watt per pound whether you want to sfly scale, sport or 3D
example -
50 watts per pound = Casual/scale flying
75 watts per pound = Sport flying and sport aerobatics
100 watts per pound = aggressive aerobatics and perhaps mild 3D
150 watts per pound = all out performance.
Is there an equivalent for nitro using CCs?
Crux of matter is I have cub and have added scale-like (read heavy shock-absorbing gear) plus heavy cub tires and am concerned it will be heavy. Weight all up according to specs is supposed to be 7.5 lbs for a 4 stroke recommendation of .40-.90. I have an HK ASP .61 4 stroke (likely underpowerd from normal .61 FS). Wondering if I should change motor now or keep pressing.
I'll likely try and get a weight estimate tonight and have my first peek. She was build solid (read wellbond glue) and should be on heavy side.
Tks in advance
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Post by Deleted on Aug 19, 2013 11:48:42 GMT -4
I read the box the kit came in, and it tells me. Also, the instructions usually do to. . . . .
Sorry, had to. You probably noted the difference between Timberman's cub, and Leeann's cub, power wise. The Saito 130 makes nowhere near the power that the 26cc gas does, but it still performs like the real deal, and then some. With a 61 four stroke, you'll probably be quite scale. Down the road, if you want a bit more fun, build a second clipped wing, and put a 91 OS or Saito on it.
Medium and thin CA are all I use for all but giant scale, with epoxy for high stress areas, or wellbond, but it's massive overkill for 90% of the aircraft, and really slows building time. Medium CA has over 30,000 lbs per square in of breaking strength, and can be used on homebuilt aircraft (I've done it, approved by the RAA).
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Post by gregh on Aug 19, 2013 17:32:28 GMT -4
I agree with Dave. While there is no chart or anything like that I'm aware of, using the manufacturers guideline is best. But it's just that, a guideline. If you were to stick a .40 4S on there it likely would barely get off the ground. .60 4S will be scale, and a .91 will have power to spare. It's all a matter of preference.
7.5lbs is a little heavy, but don't forget its still a cub with a nice high lift wing.
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Post by Deleted on Aug 20, 2013 17:36:51 GMT -4
I got in a pair of Saito 65s, Greg is going to work them over, see if they can be made into a reliable matching pair for my C-47, If not, one engine seems good, other not too sure, so might have a good and a parts bin for sale. I'd go for the OS 70 though, that's on RCC for the cub.
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