Has anyone used, or tried to use two types of airfoils on a wing? One type at the root and another at the tip and fused them together, rather than use washout. If so what were the results?

A lot of full scale aircraft use a different airfoil for the root and tip. A good example, the Cessna 152 has a NACA 2412 at the root and uses a NACA 0012 for the tip.

I was wondering if anyone had bothered to try it in a model airplane, or if it would even be worth the effort. I am working on a design using very stubby wings and was wondering if it would be worth the time and effort of using a tip airfoil that by its shape would stall way after the root. To give me a greater margin, or should I just use washout and leave it at that.
P.S Check out oddball design in the scratch build forum.

The idea works at model sizes, although most model airfoils all stall at around the same angle, 10~12 deg. An example of the thing is the popular FlopTite Stinson SR9 kit, which uses a similar airfoil change as aerodynamic washout.
Evan, WB#12

If you want to see a MAJOR change in airfoil on a full size plane check out the wing on a Navion. Navions were designed and built by North American {same as the P-51 Mustang} The root is almost symmetrical and the tip is so under cambered it looks like it's from the Wright flier.
Try this: http://aeroweb.brooklyn.cuny.edu/dat...ge.htm?id=5806

Control Line Precision Aerobatics (stunters) have been doing it forever.

Symmetrical airfoils do this extremely well. When I was flying competition stunt long ago it was at a level where most guys designed their airplanes, and almost all of them did it.

When I started flying RC gliders and playing with airfoils on my own designs, I discovered that almost all the guys who drew up their own wings were doing it too. I'd say that it was something almost everyone did who had advanced to drawing their own airplanes. Matter of fact, if you read almost any book on model airfoils, there is probably mention of it. And there will be a good probability that the airfoils listed will include pairs that were designed to have one at the root and the other be the tip.

I have a couple of buddies who fly RC precision who said they thought most of those designs employ it. They don't do their own building but were familiar with it. I got a few IMAC buddies that think the ARFs they bought have it. Don't know any IMAC guys who build their own, much less draw their own.

It works.

Hi,
The ZLIN of some years ago -sig- used two diffrent airfoils, and flew very well.

BTW, the term "washout" often is used with modifiers. You might see "aerodynamic washout" used. And sometimes you see "physical washout" and such.

A lot of people think that washout just means the wing is twisted. But aero washout is a wing with it's airfoil changing from root to tip. The idea is to do what twisting the wing to get washout does without the problems that causes. So how does that work? Great..... and what's the theory of it? If the airfoils are symmetrical then it calms the wing's tip stall potential. And it does it right side up and upside down. If you were to twist the symmetrical wing to get some washout, you'd be screwing the airplane's performance when inverted or when doing outside maneuvers. So what about cambered wings.....

Most designs that choose cambered are for airplanes that won't be doing maneuvers where inverted performance is paramount. However, there are cambered airfoils that don't kill the airplane when upside down, and there are lots of aerobatic airplanes that have cambered wings. And there are pairs of cambered that do pretty good outside and inverted. You just don't expect to need cambered and inverted with models thanks to their light wing loadings and high power loadings. So you don't often hear much aero washout talked about for the model designs that employ cambered wings. And after all, if you're using a cambered wing, what 'cha gonna lose if you twist the sucker. It's already not symmetrical.

If the wing's chord tapers more than the wing's thickness does, then you have a different airfoil at the tip than at the root, even if the aifoils don't have official names.

Thouroughbred speed designs usually do it too. they'll use the thinnest airfoil they can get away with, and may have to use a thicker foil at the root than the tip foor strength. Check out the extreme speed forum and look for a thread called "let's build a speed plane" Cambatpigg used a NACA 0008 at the root and a 0006 at the tip.

The Funtana ARFs have it. They have also had some problems either with how they implemented it or with quality control.

Thanks guys,
I was thinking of doing this where I am using stubby wings on my design. And concerned about the chance of the tip stalling before the root when doing a landing approach. The plane I am working on is not being designed as an aerobatic model, what I am trying to do is make a STOL type of design. Flying inverted is not high on the list of design concerns, but loss of lift on the wing tip would be a real issue with the stubby wings I am using.

From the full scale.. North American Aviation drawings..
The NAA B-25 has the same scheme.. Semi-symmetrical at the root, undercamber at the tip.
Any good airfoil program (Profili) will compute the intermediate rib shapes..

That answers this question, I am going to go for it...
Thanks guys!

Different airfoils at wing root and tip are very common in the full-scale world; in fact, more the rule than the exception. The root section is made thicker, up to 18%, purely for structural strength at the expense of drag, while the tip section may be as thin as 9%. This results in a wing that needs washout, of course, in order to prevent the wingtips stalling well before the root.

I know they are common on full scale I was wondering about how it would work in the model world also. I have since found out that it is common, even more than I would have guessed.

A real eye opener is the Avro Vulcan bomber of the 60's. Almost a full symetrical at the root for airducts and fuel. By the tip of the wing, it is a DEEPLY undercambered foil. The plane looks like the father of the Concorde.

Sharp looking bird the Vulcan...
Many have made mention of the looks of that plane and the Concord.
That was the Brit's supersonic bomber, we had the B-58 Hustler and the XB-70.

That is a good example of a full scale using varied airfoils on a wing. I was just wondering if it had been done for models, and if it was worth the effort.

What I am going to try is a Selig8036 at the root and a eppler 230 at the tip.
I might also consider putting tip plate on it also, the plane is a design still in flux.
Check out oddball design 101 in the Scratch Build and Design forum.

I still have a Hustler Delta I built back in the 60s. It has a relatively sharp leading edge at the root and a blunt rounded leading edge at the tip. You can take off holding full up el. and it won't stall what so ever. Looks like a 747 taking off with the plane moving forward with he nose at a very high attitude. Lands the same way.

A number of turbine models, including most of the BVM sport jets, have a symmetrical root foil that transitions to a cambered tip foil.

The L-1011 and DC-10/MD-11 go to extremes on changing airfoils.. this is the wing root of the Tristar.
One of less capable instrumentation engineers on the program saw this, and wrote a letter to the president of the company telling him that the aerodynamicists had put the wing on upside down.. The guy knew this, because he flew Cessna 150s, and knew all about wings. He didn't last long.

Actually, a good tip airfoil to use with the S8036 is the S8037. They were designed to be complementary to each other, and the Top Flite scale aircraft from the P-47 on use this combination. The two airfoils were designed especially for model use and have turned out to be excellently-suited for scale models.

Bax do you have a drawing of the 8037?

I know now that that was used on several models but have not seen what the profile looks like.

The reason I had chosen the eppler 230 is that the design I am working on has some of the properties of a flying wing to some degree. One other thing I had in mind with using the eppler was to counteract the pitch down effect of the main wing area to take a bit of the down force load off of my tail surfaces.

Using two different airfoils used to be pretty common on the older pattern planes. I have seen planes with a symmetrical root airfoil and a semi-symmetrical tip with washout. This is easy to do if you cut a foam wing.

Back when I used to design and build a lot, I used a 15% root airfoil and a 17% tip airfoil. As I said, easy to do with a foam cutter.

Thanks for the tip Ed.

I had no idea that this was so common in model aircraft. I had seen may mention washout and alike, but they would most often use the same airfoil root to tip with no mods other than a bit of taper or sweep.

I had not thought about using a foam cutter to make the wing. I could then just slice out the pieces for rib patterns and build them up from wood. The design I am working on was for a competition that one of the rules was that most of the airframe had to be constructed in wood. But that does not mean I can not use the foam as a design tool. A plywood pattern for the root and tip would be easy to do then cut the foam and take out the slices I need for the ribs is still an idea.

Thanks again for the tip, that method should work well for what I am doing.