Changing a wing

[Mike Griffin]

Here is a question for anyone who may know the answer.

If I have a wing that has a 52" span counting the wing tips and a root chord of 12 1/2 inches at the center and 10" at the tip (not counting the wing tips), and I want to make it a barn door type wing with a constant chord of 12 1/2" all the way across, is there any adjustment you would need to make in span one way or the other?  The current leading edge is straight with a swept forward trailing edge (ref the chords) .  I know I had this discussion with Allen Brickhaus years ago and he said yes but I cannot remember what he told me.

Thank you
Mike

[Brett Buck]

Here is a question for anyone who may know the answer.

If I have a wing that has a 52" span counting the wing tips and a root chord of 12 1/2 inches at the center and 10" at the tip (not counting the wing tips), and I want to make it a barn door type wing with a constant chord of 12 1/2" all the way across, is there any adjustment you would need to make in span one way or the other?

     To do what, keep the same area? Your starting wing area is 11 1/4 x 52  = 585 square inches. To get the same area with a constant 12 1/2" chord, your wingspan should be 585/12 1/2 = 46.8", say, 46 3/4".

   However, that takes your already low aspect ratio (ratio of span to average chord) from an already-low 4.6:1 down to an extremely low 3.75:1. That will drastically increase the induced drag when maneuvering, meaning it will slow dramatically in the corners and make extreme demands on the power/propulsion. If this is for sport/stunt, be prepared to get the honkin'est very low pitched piped IC system or very large feedback electric (since the drag will also require a massive battery to make it through a flight).

     A more typical aspect ratio for stunt models about this size is 5.2-5.5:1. For 585 square inches, that's a span ~56" and an average chord of 10 3/8". That will demand far less of the engine/propulsion than even 4.6:1, without being so high as to cause other issues

       If you meant to adjust it for something else or for some other goal, I think we need to know what the goal might be.

     Brett

[Mike Griffin]

Brett,

Thank you.  You told me what I needed to know.  I was trying to figure out if I wanted to take the wing I described and make a constant chord wing, what chord width should I use for the ribs.  If I understand correctly, if I did this, the constant chord should be 10 3/8?  This is not a flapped wing.  That was the goal.

Mike

[Brett Buck]

Brett,

Thank you.  You told me what I needed to know.  I was trying to figure out if I wanted to take the wing I described and make a constant chord wing, what chord width should I use for the ribs.  If I understand correctly, if I did this, the constant chord should be 10 3/8?  This is not a flapped wing.  That was the goal.

Mike

  If that was the point, you are no longer modifying it ,you are designing a new one.

   If you just want a straight-wing equivalent of your original tapered wing, I think you want 11 1/4" chord - the average chord of the original. That will give you a constant-chord wing with 585 square inches, and an aspect ratio of 4.6:1, same as you started with

     Brett

[Mike Griffin]

That was what I was after.  I guess I did not explain it well.  Thank you again.

Mike