Pattern Airfoils
 

Posted this question in the Aero thread with minimal response.

Any airfoil recommendations for pattern aircraft would be appreciated. Thinking of doing a scratch build.

RE: Pattern Airfoils
 

You need to be more specific about your goals. Size of model, type of flying (old style turn&burn or newer turnaround), etc.? Typically, the smaller the model, the thicker the airfoil. Current 2M ships are using 9-10% thick foils that will not work well on a 40 size plane.

The NACA 00 series are good, especially the 0012 and 0010. Also the NACA N-64 series works well and is a laminar flow foil with the high point back around 40% chord, which is very similar to many of the current foils used. If you don't have the coordinates for these, do some Googling on naca and airfoil coordinates and you should find lots of info.


Mark

RE: Pattern Airfoils
 

Thank's Mark. I'm considering a 78 inch span .90 size ship. Smooth and accurate aerobatic performance, but I won't be overly picky as I'm still learning. I've heard that the NACA 00 series are good and I have access to them and others.

My perception is that most pattern ship foils are symmetrical (or almost?) Is this true? And if so, I assume a small angle of attack would be needed.

I would also assume that the thinner the foil, the lower the drag and greater that stall exposure.

If someone with experience on these issues could address these points I'd be much grateful. All advice and recommendations are appreciated. Thanks.

RE: Pattern Airfoils
 

If you want to build a 90 size ship, 78" is too much wing. For really good vertical performance on a 90 2 stroke or 90-110 4 stroke you need to stay around 7.5lbs AUW. Look at current designs for ideas on size. The Boxer 90 has a 65" span (I think) and 820 sq.in. and a target weight under 8lb. This is a reasonable area to be in. If you want to fly it on the wing instead of massive power, your wing should be OK. But it will probably be heavy and not have really killer vertical.

Yes, they are all symmetrical. Typically, the planes are set at 0degrees and the angle of attack is introduced in the plane's attitude in the air. Depends on the model, though, they do vary.

Yes, the thinner foils are lower drag (as is the N-64, which is a laminar flow section) and typically stall harder. A fair number of current 2M planes start with about a 10% section at the root and taper to 8.5-9% at the tip, to promote tip stall for the spinning and snapping maneuvers.

If you are still learning, I would say you are better off buying a proven kit and practicing a lot instead of tinkering with an unknown design. If your goal is to simply fly your own plane, then go ahead. But it will be more cost and time effective to buy a proven design and build it straight and light... I understand your desire, I have designed and scratch built a number of my own planes and enjoy it tremendously. But it is not the best way to get a really good pattern plane. If you like scratch building (as I do), then buy plans for one of the Boxer series and go to it. If kits are OK, the CA Models Widebody 60 and Epsilon 90 have a great reputation and are not too expensive.


Mark

RE: Pattern Airfoils
 

Thanks again Mark. Great advice. I find I learn a heck of a lot more by scratch building as I get into a new type of plane. I realize this is an unconventional approach and understand the pitfalls. But it forces me to do a ton of research on virtually every aspect of the design, to get lots of advice and wisdom from the masters, and to learn from a few mistakes of my own. Its a steeper learning curve for sure, but in the end I feel I've learned much more. It has worked well for me in the past on other designs. Its like me to beat through the brush even when a proven trail exists. It's all about the journey for me!

RE: Pattern Airfoils
 

Well, I have cut parts (ribs) for a couple of the older aerobatic types. One cites the use of a NACA 0012 airfoil, but it doesn't resemble such. One A/C cites using a 65A015 or a 65A012 and that fits good.

All of the wings which I have done seem to indicate in their documentation the thickness runs from usually 15% down to 12% or 10% at the tip.

Wm.