thrust, wing area, etc

[Texy]

Is there a basic simple relationship between thrust, AUW and wing area?
I,ll be setting work on a homebuild cd-rom motor, and I,d like to know how much weight it will be capable of lifting. I guess that will depend on the size of the wings and the AUW of the plane its trying to lift (wing loading ?).

I,m sure someone will have a simple answer:D

Cheers,
Texy

[Mark Wood]

This might have a better chance of a good answer in the Modeling Science area. Off it goes!

mw

[Ollie]

For level flight at a constant speed, the thrust equals the drag and the lift equals the weight. At a constant angle of attack, the lift and drag go up as the square of the speed. For the model to climb, the trust must be greater than the drag and the lift must be greater than the weight.
There are four ways to improve performance. Decrease weight, decrease drag, increase lift and increase thrust. Even though the power may be limited by the motor's capability, the thrust can be increased if a better propeller can be found. All the factors that improve performance interact with each other. Until you can put numbers on the power and weight of your motor, battery etc. the rest will be up in the air so to speak. :)

[Dick Huang]

Texy,
Look at my reply to "Aircraft performance/flight summary formulas" by groundfx. It has the equations Ollie is talking about.
All you need to do is know how to use it.
Dick Huang;)

[Hasina75]

Texy,

There are some relationships among thrust, wing area, and wing loading. Thrust to weight ratio is very critical for electric planes compared to gas planes. Because this forum is aimed to help people who are interested in electric power, we focus more our discussion on electric planes. Let's say you are going to build an airplane, but you are not really sure about its power plant. You may choose one of the following options after you build the model. My advice is not to fly the plane at this step.

If the airplane with battery installed is quite heavy and the CG is in the right location:

Increase the wing area to minimize the wing loading without adding too much weight on the plane, OR

Increase the wingspan to the chord ratio for a better glide. The better the glide the less thrust you need to make the aircraft stay in the air. For example, the GWS Mustang's motor needs to deliver more thrust to keep it in air than the GWS Slowstick's motor does. The slow stick flies like a glider and thrust to weight ratio is not an issue, OR

Remove some unecessary parts of the airframe to minimize the wing loading, OR


Add one cell and get a bigger prop with low pitch, OR

Assuming that you are eager to fly after you spent many hours on your plane, use a brushless motor to be on a safe side.

[Texy]

OK guys - thanks for the replies.
I understand that the planes design has to meet certain criteria in order to be able to fly.
I thought that there a general simple rule-of-thumb equation that could be applied. Something like 'the static thrust should equal at least half the AUW' ?
I,ve read it somewhere......


Cheers,
Texy

[RSCherry]

Check the FAQ under "Design Issues" for some basic guidance on Watts/lb. Should get you in the ball park on what size plane you can fly on a given motor. Although you are working backwards from the norm, you should be able to rearrange the logic to determine some basic specs such as weight and wing area.

Bob