jd_boggs

I'm going to simulate my new air foil design and I need to know how much lift is required beyond the weight of the airframe to achieve stability? Is the answer in percentage or factor of 2 etc. I simply don't have a clue..... Merry Christmas to all.
thanks in advance..

Lownverted

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What do you mean by stability? The airfoil and its lift making ability have very little bearing on stability. Some have better pitching moments, but that is all.

combatpigg

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I think you want to have at least a 4 to 1 thrust to weight ratio..especially if this is your first model. If you stay true to this advice..then your choice of airfoil is not so important.

jd_boggs

thank you ......I will note this and remember the 4 to one ratio

speedracerntrixie

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Although if you did the math you would soon realize that 4:1 power to weight really isn’t feasible.

combatpigg

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I was being facetious.
I learned to fly with a 6 foot glider powered with a Cox .049 engine.
Lots of lift .not much power..but after a 3 minute engine run that plane would be 400 feet up.
Probably 12 ounces of thrust hauling 36 ounces of weight.....a 1 to 3 ratio..not real thrilling but I was thrilled to be learning basic flight control.
Next step was the same engine mounted on a lightly built "Old Timer" type design that probably weighed 1/2 as much as the glider but with 1/2 the wing area of the glider.
This plane was a great "second trainer" and it was obviously a lot more "sporty" with a power to weight ration of 12 ounces for the engine and probably 18 ozs for the plane..a 2 to 3 ratio or about 66%
Pretty amazing how much airplane can be flown with such limited power.
Here is an old design that fits the description..the Airtronics Q-TEE

speedracerntrixie

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I had a Q-Tee as well as a teenager. Always liked the classic lines. My granddaughter now 3 is showing interest in airplanes. In another few years I’ll break out a ST .29 and scratch out a 60” version for her. Yours is a great looking example.

BMatthews

Jd Boggs, assuming you're still checking on this thread you started you need to stop and realize a few things.

1- the wing makes the lift it does from the airfoil, the size of the wing (area), the speed the wing is flying at and finally the angle of attack that the stabilizer and elevator hold it at.
2- in level flight at a steady speed the lift from the wing is exactly equal to the weight of the airplane. If it were even a fraction of a percent different the plane would either climb or descend. And even then the new speed caused by the climb or steady descent would then shift to where the lift of the wing was exactly equal to the weight of the airplane.
3- Where the wing gets called on to generate extra or less lift is during pitching maneuvers. Examples are looping or during banked turns. In those cases the need to accelerate the plane through some degree of pitch change causes a vector addition of the effects of centrifugal forces and gravity to increase the load on the wing and require that some excess lift above that needed to match the airplane's weight is required.

And as mentioned this has nothing to do with stability. At least not in as the term is used for describing an airplane in flight. Stability in aerodynamics refers to the degree that an airplane will try to return to some previous trim state when disturbed.