scratch building airframe

[kindred]

would anyone be kind enough to outline the steps I should be taking when trying build a model aircraft from scratch. basically, how will one know wether it will actually stay in the air. how does one get things like c.g position and center of lift position accurately. i realise its a broad question but would really appreciate any kind of help.

[MarkusN]

This Guy's (http://en.wikipedia.org/wiki/Andy_Lennon) books seem to be a good start.

[maxvtol]

If you want to try building something in a simulator to see if it will fly, try this x-plane.com (http://www.x-plane.com/) . Build your plane in PlaneMaker and see if it will fly in the sim.

It won't teach you how to build it, but the physics is pretty close once you decide on what you want. Trial and error can be pretty fast.

I've been using this for years to design aircraft for fun.

[kindred]

Appreciate the suggestions guys. Guess I have a long road ahead of me

[Lon Enloe]

My suggestion is to look at a number of current designs in the general vein of what you want the plane for--aerobatics, tooling around the park, etc.--and use that as a jumping off point. You can get a lot in the way of originality by relatively small alterations in the wing and tail planforms, fuselage shape, etc. The maxim of "If it looks right, it flies right" can take you a long way.

The other alternative is to pick a scale subject. If the original flew, it's likely your model will, too, although the less exotic the scale subject, the more likely it is to fly nicely. My Howard Ike, for example, is pure joy to fly--it simply has no bad habits, but it's one of the most "normal" planforms among the 30's racers. A Gee-Bee, on the other hand...

I like 270-300 sqare inches on the wing, given the power plants I typically use. Then I pick the airfoil--The Eppler 168 for aerobatics, the Selig 3021 for scale models are my current favorites--and the rest usually falls into place fairly quickly.

I've had them fly straight off the drawing board without a hitch, and I've had them last 10 seconds on their maiden flights. Each instance has taught me something--the latter ones probably more than the former.

Give it a shot--it's fun having the only copy of something on the planet.

[groundfx]

If you want a typical airplane, here are some rules of thumb: http://www.uoguelph.ca/~antoon/hobby/pmdesign.htm

If your design is quite unique, a simple approach is to just build a smaller, free-flight glider from balsa or foam to test out your design and do some trial and error testing and changes with it.

Finally, I'll let you in on a secret... as long as your airplane looks like an airplane, has it's CG in roughly the right place, is not too heavy and has enough power... it will fly! Even airfoil selection is not critical. i.e. as long as the airfoil looks like an airfoil, it will work. It's only when tuning for maximum performance where things like the particular airfoil used start to matter.

The key thing is don't get scared away... it's not that hard to do.

[kindred]

thanks a lot for the replys.I managed to get a copy of andy lennon's books.its got alot of information.I would recommend it for sure.