Small Flying Arts

Up to now, all of my builds have been from kits. Some built really stock and some slightly modified but nothing to drastic. I would like to build from 3 View drawings but I have no idea about how to decide concerning airfoils etc. How do you scratch builders do this?

The simplest method that I learned was to spend time looking at other plans of similar models. There are masses of plans available online in sites like Outerzone. If for example I was wanting to design my own Piper Cub for rubber power at 24" span then I would browse plan collections looking for similar sized models of similar types of aircraft that were also rubber powered. With that example there will be hundreds of similar plans, less so with rare or odd aircraft but there are usually enough to get some good ideas of what other designers have done.
Next would be, just try it. you will learn more by doing, than by thinking about doing, and if it doesn't work you will still have learnt something.
Lastly, ask questions on great modelling forums! There are plenty of helpful people to point you in the right direction if you need advice.
Tim

I have the same apporach as Tim...
To choose a wing profile, I take a profile from a model with similar flight characteristics. This might not be the most scientific way to build from a 3-view plan, but it works quite well.

In the book of Don Ross (Rubber Powered Model Airplanes) are some formulas on how to plan a new plane. Have to try this approach one time...

Roman

I follow the same route as Tim, I decide what I want to build and then find plans of similar and spend ages looking at them asking why the designer did this or that . Then I print out the three view to the size I want and begin adding in the structure as I go. This is usually a combination of the best bits from those plans with certain of my own preferences thrown in.

Sometimes my models fly well, sometimes not, but designing and building is half the fun for me. I learn and expand my skills during each new model.

Hey Monz, great to see you've surfaced again. I guess I''d be more connected if I did Facebook, but I don't.

art.

Wow! Good stuff here. Thanks for the informative replies. I will try these techniques as my skills increase. Thanks again
Gwyl

For airfoils I was advised by the late Walt Mooney to keep your airfoils under 12% thickness and put the high point of the airfoil at the 33% of the chord point. The actual curve, he said, was not that important as no stick and tissue wing can be built to very tight tolerances and at the low Reynolds numbers our planes fly at, nothing is predictable. The sharper the leading edge the more turbulent the boundry layer (good) but the more critical it is for the airfoil to fly at its own special angle of attack (bad). The result is: round off the leading so it looks nice to you and it will work as good as anything.

tom arnold wrote:For airfoils I was advised by the late Walt Mooney to keep your airfoils under 12% thickness and put the high point of the airfoil at the 33% of the chord point. The actual curve, he said, was not that important as no stick and tissue wing can be built to very tight tolerances and at the low Reynolds numbers our planes fly at, nothing is predictable. The sharper the leading edge the more turbulent the boundry layer (good) but the more critical it is for the airfoil to fly at its own special angle of attack (bad). The result is: round off the leading so it looks nice to you and it will work as good as anything.

This sounds like good advice. Walt sure has a long and lasting effect on this hobby. Thanks Tom

Gwyl

A good way is also to check what the Czechs have done, lately I've copied construction methods and airfoils from them! People like Alfery, Koutny etc. do know a thing or two of well flying scale models. Pistachio, Peanut and 1/20 scale being the most popular. Plans can be had for example from Mike Woodhouse, Free Flight Supplies http://www.freeflightsupplies.co.uk/ind ... ucts/plans

A great resource is: http://airfoiltools.com/
you can find almost any airfoil there.

FAC rules require a flat bottom airfoil unless the actual airplane used an under camber airfoil - then you can use the scale airfoil. So I just finished a 36" Fafnir for the new FAC Glider event. The real Fafnir transitioned from the Go 535 to a Clark Y at the tip - so does the model.



I hope this is the right way to post a photo
have fun - Rick