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I am trying to design a free flight glider (I don't know what I'm doing, however, I'm interested in aerospace engineering and am trying to learn) And I was wondering, what would a good airfoil be? I also want to know; how much lift can something create before it begins to stall? I have calculated my CoL of the glider, I think I found the CoT, but I need help finding the right airfoil and AoA for a styrofoam glider. it currently ways around three pounds and is 14 inches (from nose to tail), and it has a flat bottom.

Hboi
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  • I'm thinking of around a 7-inch wingspan, but I can't find a good airfoil, I also think the one I want to use (Eppler E393 airfoil) may cause too much lift. I also don't know how to calculate how much thrust I will be creating when I throw the glider. – Hboi Apr 25 '22 at 14:07
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    I believe free-flight gliders are normally thrown in a banked attitude to prevent the plane from trying to loop when thrown at a speed high enough that the wing generates more lift than the weight of the plane. So the plane is launched in a turn. – quiet flyer Apr 25 '22 at 14:12
  • Consider asking your question on a model airplane forum like "rcgroups.com" (check out the "modeling science" section there). – quiet flyer Apr 25 '22 at 14:13
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    I’m voting to close this question because it belongs on Drones.SE, not Aviation. – Ralph J Apr 25 '22 at 15:53
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    How is my question a drones question? – Hboi Apr 25 '22 at 16:27
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    3 pounds is VERY heavy for a glider of that size. You really ought to consider removing a large amount of that weight, especially if the wingspan will only be 7 inches. – MD88Fan Apr 25 '22 at 23:02
  • Yes, 5-6 ounces per square foot of wing is a good number. See Mark Drela's Alegro if interested in AE. http://www.charlesriverrc.org/articles/allegrolite2m/markdrela_allegrolite2m.htm – Phil Sweet Apr 25 '22 at 23:31
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    3 pounds/14" is a missile, not a glider. At the very least, you need to specify whether you are optimising for distance or time of flight. For reference, competition gliders for time weigh under 1 lb for a wingspan over 2 m (80"). They are not thrown, but they will outcompete yours in most circumstances. – Zeus Apr 26 '22 at 01:22

1 Answers1

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The cambered Eppler E 393 is a great choice if you are going to a hill top for a smooth slow constant speed glide.

For a throwing glider, or one that experiences change of airspeed, a thin low drag wing with lower lift coefficient is better. This is why deltas are very popular for paper airplanes! This is particularly true with low wing loading.

a 14 inch glider need not weigh 3 pounds

If you want to throw like a spear for distance, reduce weight and camber, going for low drag.

throw it hard and it just loops

This is where you move your CG back and reduce nose up trim.

Ideally, you want the plane AoA to increase as it slows down. (To keep lift the same). It will have a flatter trajectory when thrown hard, only stalling at the very end of the flight.

Having tried both, free flight from hill tops seems better, but too much camber will not perform well in gusts either for the same reasons.

Robert DiGiovanni
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