hiigaran said:
ok well is there a way i can calculate all the necessary info in all this -
There are sites that show recomemded power in watts per pound for model airplanes. I suspect those recommendations would lead to a greatly overpowered ultralight. Even at the low end, though, you will be looking at a 10KW to 15 KW motor for a flying weight of 300# or so.
Edit (from a hobby site):
50W/Lb = Scale or slow flight
75W/Lb = Sport and mild Aerobatic
100W/Lb = High performance and Fully aerobatic
200W/Lb = 3D aerobatics
On the other end of the scale, McCready (hope the spelling is close) had less than a horsepower for his man-powered airplanes.
There are formulas from aerodynamics that would allow calculation once you have projected speeds, weights, drag, and lift figures. You also need to decide whether you want just power-assisted flight or you want the thing to take off from the ground. The latter requires much more power.
However, for a start, I suggest you look at powered ultralights similar to what you plan to build. Find the horsepower and assume that an electric of the same equivalent wattage or less will work. In fact, an electric of 1/2 to 2/3 of the IC engine wattage may work just fine. Note: modern brushless electrics can give power outputs of 80 to 90% of the power input. With that information, you can make a rough guess of the power train requirement and weight. Add that to the initial weight estimate and repeat calculations.
Neu motors (
https://www.neumotors.com/) has a motor calculation program and makes some pretty large motors. Just go to any of the motor selection sections like the 1105. Once there, click on motor calculator and you can chose any motor you want. I have read about one model design that used a single 8 KW motor! My impression was that that might provide enough power to assist flight in a full size airplane. John