Ram-bro

My Feedback: (101)

here is a question for all you scratch builders and designers. If a guy desides to design and scratch build an airplane, how do you choose an airfoil and wha is the difference between them?

w8ye

My Feedback: (16)

http://www.rcuniverse.com/forum/m_7274662/tm.htm

There is an aerodynamics forum

http://www.rcuniverse.com/forum/forumid_76/tt.htm

kdc

The short & practical answer to your question is to find a plan of a similar size model of the type you want and see what airfoil was used. Many plan articles show the airfoil number NACA, Clark Y , Gottingen. Wortman or RAF etc. An airfoil plotting program such as Profilli will plot one of these for you at the required size.

You could go to http://www.rcmmagazine.com/issues/re...eMEt64lzI6E7M4 and use the log in details provided free to gain access to dozens of RCM plan articles most of which have the airfoil number shown.

You could also refer to plan articles by people such as Peter Miller who almost always explains what airfoil he used and why. I think one of Peter's books has this info too-it might be in "High Flying on a Low Budget". For your first own design you might just re-style an existing design to your taste and construction methods.

BMatthews

Welll.... first you need to set the flying style. For hot aerobatic models this is easy, symetrical. For something more fussy like a sailplane we need to look at what sort of speed range you want and then figure out what the Reynolds number range will be and from that look at airfoils that provide low drag and predictable handling over the range of lift coefficients that it'll fly with.

Then you have to consider just how accurate you can make the overall wing. For open framed designs covered with material pick only shapes that are known to be tolerant of airflow problems over the Reynolds number range. There's lots of super airfoils out there but in many cases their advantages can only be realized if you can build the wing to a VERY high standard of accuracy. The rest of us are better off using an airfoil that is known to be a lot more tolerant.

There was one other method that was a lot easier to do a few years back when there were two or three construction articles in every model magazine that came out..... PLAGARIZE! Just look around for a known good design and copy the airfoil.

Ram-bro

My Feedback: (101)

I understand the idea of using what is out there already. I hear so much about '"clark Y" and selig and etc. I have scratched one airplane from my own design. It flew, it was snappy but it was mine.

w8ye

My Feedback: (16)

Undoubtedly there have been many somewhat popular models designed around aerodynamics that could have been better chosen but most people thought the planes were OK.

kuldeep

easiest way would be G2 to G4 flight sim. choose the kind of plane you want, go to edit plane. You will get all the info you need. You can change parameters and test fly your plane even before you start building one.

BMatthews

For power sport type planes you can get away with quite a lot. It's different when the model has to perform really well in some specific aspect such as racing or soaring. Then it gets a lot more fussy.