Hello Fellows from Stunthangar!

What is the best airfoil (simetrical) to use in a stunt airplane designed to use .35 to .40 engines?

Best Regards!

Adriano,
Agree with most of what Ken said, for the Fox you would want to have a ship with 16 - 18% thickness and max span of 46 - 48", keep the weight below 40oz. Also if you use a Fox 35 with muffler cut the prop diameter to 9 1/4 - 9 1/2" to reduce load (heat) in the engine. If using a more current engine then what Ken said fits the bill, Vector is a good ship to look at.

Best,   DennisT

Your actually best to ' RESTYLE ' a existing competant design , perhaps .







Twink , twink , glorious twink .



These suckers will carry a bit of weight . LIKE ANYTHING , building it light straight & true with ' solid ' controls
is essential if its to behave itself .

Thank you Guys for your answers and sugestions!

I haven´t flying Control line models sice 1990!
In the last weekend i flow an old model with an O.S. Max .15 III on it, and I became motivated to fly again the Control line models.
I like to design and build my planes, so I intend to design a model for the intermediate flyer to start practicing again.
The plane will have flaps and a profile fuselage to make the construction easier.
I have two engines to choose, an old FOX .35 and a brand new OS .40 LA.
I thought to use the Fox .35 in the begning and the OS .40 LA later when my abilities became better.
What´s your opinion about this guidelines?
 

If the FOX is reliable it will be OK if it is a newer one.  On a profile you will have to deal with the unnerving "Burp" of a FOX.  The motor appears to quit then comes back.  The OS is more reliable and considerably more powerful and very polite (no burping).  If it were me I would use the OS.  Power when you are learning is very important.  I like to build my own as well.  If you want an airfoil appropriate to a profile for this size motor look at the SIG Twister/Banshee profiles.  The sharp LE of the 60's designs is not the best you can do. 

Ken

Ok Ken, I will follow your advice and use the OS .40 LA engine.
I found a Sig Twister plan on internet and downloaded it, I think that I have all I need to start my project.
I will post some pictures here after the plane is ready.
Best Regards!

If he has an LA40 available as the powerplant, there are plenty other common designs that are out there superior to the Twister with more wing area and a better overall design.  No shade against the Twister.
Brodak profile Cardinal 40, Legacy 40, Pathfinder, Chipmunk, Vector 40, Imitation, just to name a few of the many. 

Did someone mention CARDINAL .Profile Plan THERE .

https://stunthanger.com/smf/open-forum/windy's-profile-cardinal/msg568125/#msg568125

Sgota fairly usefull airfoil .



True things outer cardinal 92 ribs . vailable laser cut . you LOOSE the center few , Like THIS /. https://stunthanger.com/smf/nostalgia-30/gieseke-nobler-46/msg613419/#msg613419

Post 54 here gives you some dimensions to Suit a LA 40 / 46 , if you wanna go the Greenaway way . https://stunthanger.com/smf/nostalgia-30/big-jim's-n30-designs-patternmsater/50/

Thick Wing means good support , easier slower flight , maybe . LASER CUT Ribs , unless your a rib afficionado , are a big ' accuracy ' ensurer . You want a few jigs / blocks / packers & suchlike .

https://stunthanger.com/smf/open-forum/cardinal-profile-vs-pathfinder-profile-some-of-your-thoughts-please/

Damp marshy grounds safer than sun baked concrette , if youre tripping over things for a while .

The Fox needs a little smaller ship you could reduce the number to match as a 46" span or do a Tutor with a bit thicker wing, but keep it light with good wood and a light (like UltraCote) finish. To use the film covering you should plank the last section of the wings (wing tip bay) with 1/16" balsa to get the rigidity (this is the way the original Tutor wing was done, it was designed for film covering and works really well.

   I am not sure why you want to make the Tutor wing thicker, it is a quite excellent proportions, size,  and shape for a Fox and nearly ideal for a 20FP or 25LA. I would make only one change to the original Tutor plans, make the stabilizer about 30% bigger and leave the elevators alone. With good wood, the stock kits built to extremely good weight - I had two of them, from the kit, one weighed 27 ounces with a Fox 35, the other one weighed something like 30 ounces with a ST46.

    Note that I mean the *original* Tutor, from the kit, not the ARF version, which is vastly larger - as in the plans Dennis posted above.

      Brett

Thank you Guys for your answers and sugestions!
I haven´t flying Control line models sice 1990!
In the last weekend i flow an old model with an O.S. Max .15 III on it, and I became motivated to fly again the Control line models.

I like to design and build my planes, so I intend to design a model for the intermediate flyer to start practicing again.
The plane will have flaps and a profile fuselage to make the construction easier.

I have two engines to choose, an old FOX .35 and a brand new OS .40 LA.
I thought to use the Fox .35 in the begning and the OS .40 LA later when my abilities became better.
What´s your opinion about this guidelines?
 

Welcome Adriano!
The USA has been a lottle muddled the last 10 years, but we've more or less managed to keep the real losers in check.  Hopefully smart, healthy people can keep it up.

Anyone who builds and flys MODEL planes is almost always good,   So Welcome!

The problem for you is to build a "new " profile.  There is no way, without some mistakes and some studying, to t just slap a 15-50 profile together. 
Some guidelines:
Get a smooth running, very reliable engine.  Right now, for the USA OS engines are still the most likely to fill the bill.  I just bought a new OS 25FP and a new OS FP 40.
At this point they are the easiest I've ever had.

Another US source is Mecoa Engines out in California.  They built up a small array of quality engines, somewhat  costlier than OS, such as the K&B 25 design, and on sporty larger engine, either a plain bearing 35, or a ball bearing 40 that can be fixed up for stunt- lower compression, adjustable venturi, add a head gasket or to to make the "break" heel.\

Get either a suitably sized metal tank from Brodak's, and/or several plastic RC tanks such as DuBro with 2-4-6 or more ounces.  The main difficulty is putting the fuel/air/exhaust lines in the right places and hooked up for C/L.  Look around here.  There are several posts on taming plastic RC tanks.  Once you get one hooked up and running it will usualy work just fine for several years until Sun damage, crashes, or cracks in the plastic.

I won't preach Profiles.  Virtually every single engine, single pilot WW-II airplane design will make a decent profile stunter that is sturdy and reparable.  Or just dream up you own "look" to fit the same approximate designs.  DON'T try to make it exact scale.  It often will have problems from not getting the right match between wing area, stab/elev are, the spacing between them.  The main wing and the tank, engine have to be positioned to get the balance point around 25%(1/4)of the wing area behind the leading edge of the wing.  A straight front spar is the easiest to place.

If you want to try a plane nearly guaranteed to suit you, I've worked out a Rugged Stunt Trainer that looks decent, is easy to build, flies well, and is very sturdy.  If you can fly over tall grass and at least somewhat softer ground it's almost bullet proof.  The hardest part is clean up the engine after a crash.

Join the FUN  Adriano!

Phil Cartier
717-566-3810  Speaker/recorder answering phone.