thrust to weight ratio

[Joe_in_AZ]

Help
In the progress of learning this hobby I am very curious in the thrust to weight ratio. I am not sure what a good ratio is. How do I know if my plane is under or over powered. (no such thing as too much power) here is an example of what I have tested I have a mini max with the stock motor and on my home made thrust meter it puts out 4.2oz of thrust. Buy the plane weighs 14oz.

Also is there an easy calculation for wing loading?? Is there a software program that will do all the math for me??

So many question so little time.

Thanks
Joe

[Wright Flyer]

Originally posted by Joe_in_AZ
Is there a software program that will do all the math for me??

Joe,

There are two programs that will do all the maths you need - Motocalc or Electricalc and there's even a dynamic web site where you can do a rudimentary form of calculation but Pcalc doesn't give you as much "depth" as the commercial programs.

By the way, these programs are designed for working out the best power system for a model. To work out wing loading it's actually a much easier calculation. You just measure the wing (so maybe 3ft wide by 8" in chord) and work out that this is 2sq ft (8"=0.66ft and 0.66 * 3 = 2). Then weight the plane. If it's 14oz then your wing loading is 7oz/sq ft

Light backyard flyers like the LiteStick and Tiger Moth will have a wing loading of about 3-5oz/sq ft. Reasonably fast park flyers (like a Switchback say) would maybe be about 7-10oz/sq ft and "heavy" scale planes of about 3-4ft wing span might be anywhere between about 10 and 20 oz/sq ft.

On the whole, the lower the wing loading the slower you are going to be able to fly it.

Cliff

[strouse]

Static thrust to weight is an imperfect way to judge plane performance but pretty useful on slow flying models. With that said I try for 1:2 - 2.5 on the planes I build, but you can fly on less.

For the more common motors, do an internet search for P-Calc. Its free software that lets you enter all the variable of a plane to see the predicted performance

You don't really need software to calculate wing loading. Ounce per square feet is simply the weight divided by your wing area in square inches divided by 144. WL=ounce/(WA/144).

Hope that helps. I started about 4 years ago and remember feeling very lost and overwhelmed in the beginning. The Litestick wasn't even around when I started. You pretty much built planes yourself.