ORIGINAL: Rob2160
22lbs weight..
11lbs of thrust..
as long as your
lift to drag ratio is better than 2:1 it will fly...
(a Cessna 150 has an L/D ratio of about 7:1)
Unless your scale aircraft looks like the apollo Command Module (L/D of 0.368) then you should be fine..
Seriouslythough.. that should be a nice combination of plane and motor..
That's true but it makes one huge and incorrect assumption.. that is that the prop will make 11lb of thust constantly regardless of the plane's flying speed.
In reality, for fine pitch props such as used by the OP, thrust will decrease in roughly a linear fashion between it's maximum thrust at static and zero thrust at pitch speed. In this case pitch speed is a very low, lets say 50mph to allow for some unloading and revving out. Stall speed on the other hand assuming the previously mentioned 34oz/sq ft wing loading is high it about 30mph. Minimum safe flying speed then will be about 35mph. Assuming linear thrust decay then thrust at 35mph = 3.3lb
ok i accept that these are rough and ready calculations but they are enough to show that there is a big problem.
Sorry but with that engine and prop and at that weight i think this plane will struggle to get off the ground, and probably best if it doesnt because if it did struggle into the air it would be seriously underpowered and probably couldnt climb out of ground effect.
Maybe the OP will prove me wrong by reporting that it fies like a bird?
Steve
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