Airfoil Choice for Mini-UAV?

[Mel Duval]

I asked this over on the UAV forum, but after thinking about it, I should have asked it here. So here is the question. I've been asked to build a mini-UAV about 36" span and 5" chord with a nominal cruise speed of about 40 MPH and a dash speed of 60+. I have the basic moments and packaging sorted out and am working on the wing now. I have built a rough prototype using an RG-15 and it flew pretty well. Now I am wondering if there are any newer technology airfoils out there that would allow a decent speed range while also being able to slow down for a "soft" landing. One of the Selig-Donovan sections like the 3021 perhaps? One of the even newer Drela series?

thx!
Mel D.

[BMatthews]

For what you want even the good ol' Clark Y would work fine. The dash speed will have to come from the powerplant and propellor in any event. The speeds you're looking at are easily within the range where the Clark Y would do well and still provide a nice slow landing speed.... if you can make it come out light enough that is. If you can't make it come out light enough then none of the airfoils will slow it down to a nice soft short field landing.

Keep in mind that with a smaller craft like this you're fighting the old scale effect again. That's reynolds numbers. And as the size of the vehicle goes down the optimum wing loading goes down with it. If you're looking at a softer/slower landing with this size you really do not want to be over 10 oz/sq ft. And 6 to 8 would be more of an optimum number.

[Mel Duval]

Hi Bruce,
Good points. The wing loading is less than 10 ounces/sqft on the prototype (I'm hoping for 7-8) and did pretty well with the RG-15. I was thinking about an SD7032 or maybe the SD3021. I have seen the 3021 on hand launch planes and have flown the 7032 on 100 inch planes. Both did very well. And of course, I have flown the Clark Y on a number of older designs.

Thx for the input!

Mel D>