Need Help Designing Wing

[Matt Chester]

Hey guys,

Thought this would be the best place to start designing a wing.

Heres what I need:

I am looking for a wing that has high stability, great low speed handling and as shallow a glide as possible.

Its for an Aerial Photography slow stick that has lots of stuff hanging out in the wind, so there is a ton of drag already there to batle against.

My first thoughts were for a S3021 with a 10inch root and 5-6 inch tips, either straight taper (both LE and TE) and about a 60 inch span.

But lately I have had good results using a cresant shaped under camber wing for my slow flight light wind use, so I also thought that may work.

Please let me know what you think of the suggestions I have made and please correct me if I have overlooked anything. Also if you have suggestions for any other style wing with any other Airfoil please also let me know that.

One last thing, I plan on cutting these wings from Dow Pink Foam and utilize carbon tube spars. Like sailplane wings.

[Tom Harper]

Sounds like you are doing fine. Got any pictures?

[Ollie]

With a gross weight up to about 2.5 pounds will be fine but lighter is better.
A very thin airfoil is OK, with 3% to 4% camber is good, for slow speeds but not good for higher speed.

It will be OK with a S3021 too. The S3021 will have good at slow speed and a higher speed capability than the thin airfoil.

With R-E-T use 10 to 12 degrees of dihedral.

Use Hollow Carbon Tube .196 O.D. x .120 I.D. x 36" (cut to 30"). Drill ID to 0.125 and use 0.125 dia. musicwire jointer bent to 20 degrees.

Use mylar packing tape (color) to skin pink foam wing.

[BMatthews]

For truly slow "hang time" flying of a model of this size and weight I would suggest your first order of battle is to reduce the wing loading. The proper airfoil will help but the most effect on flight comes from wing area effects. Since much of your fixed weight comes from equipment the only option is to add wing area. With a 10 x 60 wing you've got 600 sq inches. I would suggest bumping up to 10 x 72. Not only will you get more wing area but your aspect ratio will be raised and that will add a little bit of help to go with the extra area. To make it easier on yourself I would not bother with any taper. Or if you are not using ailerons then go with polyhedral with the tips only tapered to 6 or 7 inches at the tip and bump the span to 78 inches to retain the wing area. If using ailerons be sure to use LOTS of differential so the up moving one moves the most and the down moving one hardly moves at all. In fact for such a model spoilers would work great. About 6 inches long located at the tips and one servo each operating from a computer radio with 100% on one side of neutral and 0% on the other so only one at a time moves up with aileron input. This would help avoid the low speed tip stall issue.

For an airfoil I'm going to offer up two rules of thumb first.

All else being equal, and within reason, an airfoil with higher camber will raise the optimum lift coefficient range for more effective slow speed flying
All else being equal, and within reason, a thicker airfoil will carry excess wing loading better than a thin airfoil


With this in mind I would suggest that for better low speed range work something with 5 to 6% camber would be a big help. Similarly something more like 12% thick would also help. A Goettingen 501, at 6.3% camber and 12.8% thick, fits this bill well and I can bear witness that in this size chord it's a great performer that will fly slowly but has SOME ability to punch out into wind. It's not a speedy choice by any means but a big old timer I have that uses this airfoil has surprised my on more than one occasion. It also flys slowly very nicely with a gentle, and quick to recover stall.

At 72 inch span and 700 sq inches a .25 will be enough to lift up a total airplane weight of up to 5 lbs easily. It's not going to be a good windy weather machine though. Up to about 10mph will be fine but if it's worse than that or gets turbulent you should stay on the ground. At these numbers it'll glide well in a deadstick situation but if you want more glide ability than that you need more wing area or less weight.

More info on fixed equipment weights would help us to analyze and suggest something more specific.

[Sparky Paul]

A plane intended to fly -only- slowly can't be flown in a wind.
If you must fly slowly, make the configuration adjustable with flaps. This permits you to come back from downwind, when the plane gets there. (They always dol :) )
A Great Planes Spirit or Spirit Elite will do what you want.

[Highflight]

Wait a minute; when I read the necessary parameters to be: "I am looking for a wing that has high stability, great low speed handling and as shallow a glide as possible.", are you guys telling me that I'm the only one who immediately thought "Clark Y"?

Highflight

[Antonsoarer]

Consider the S7012, a great load carrier and doesn't mind a bit of drag or bad surface finish.