bio15
Posts: 1048
Joined: Fri Mar 23, 2001 8:10 am

Why Is The Wing's LE/TE Dist. Shorter On The Tip?

Thu Sep 11, 2003 2:40 am

Hi everyone, I was wondering why aren't most wings the same length from the leading edge to the trailing edge (is that is called the chord of the wing?) all along the span. I was making a small model airplane, and I guessed that with more surface area all along the wing but maintaining the same wingspan it would have more lift. My prediction was accurate, and the airplane flew better that the others I made. But why aren't airliners that way?

If it is not clear I'll try and re-explain my inquiry. Thanks in advance!

-Alfredo
 
buckfifty
Posts: 1278
Joined: Tue Oct 16, 2001 4:05 pm

RE: Why Is The Wing's LE/TE Dist. Shorter On The Tip?

Thu Sep 11, 2003 3:01 am

Because to hold more weight at the wingtips means the structual integrity of the wing inboard would have to also increase. Having a tapered wing can reduce the amount of strengthening required, and thus reducing weight.
 
broke
Posts: 1299
Joined: Wed Apr 24, 2002 8:04 pm

RE: Why Is The Wing's LE/TE Dist. Shorter On The Tip?

Thu Sep 11, 2003 3:28 am

In addition, the lift generated by the wing would be greater on the outer wing panels; resulting in larger moment force causing the wing to try to bend upward more.
But, on many light aircraft the wing chord (straight line distance between the leading edge and the trailing edge) length is constant. This is done to reduce the cost of construction by being able to use the same ribs throughout the wingspan. On these aircraft, the moment force on the outer wing panels is not that great due to the lower speed of these airplanes.
There is one airplane, that I know of, that has inverse wing taper; where the wing chord length is greater at the tip than at the root. It is the Republic XF-91 and the reason was to test the concept that reverse taper might counteract the tendency of the airflow on a swept wing to go spanwise and not chordwise. I don't think it helped. If you want to see what the XF-91 looked like, go to;

http://www.wpafb.af.mil/museum/annex/an.htm

This is a page on the U. S. Air Force Museum web site and they have a XF-91 in their collection.
 
MITaero
Posts: 485
Joined: Mon Jul 28, 2003 8:00 am

RE: Why Is The Wing's LE/TE Dist. Shorter On The Tip?

Thu Sep 11, 2003 6:00 am

Taper is a more manufacturable way to get a better lift distribution than an elliptical wing is (elliptical lift distribution is ideal). Taper ratios of .5-.6 have been found to be pretty good.
 
bio15
Posts: 1048
Joined: Fri Mar 23, 2001 8:10 am

RE: Why Is The Wing's LE/TE Dist. Shorter On The Tip?

Fri Sep 12, 2003 8:30 am

Hi MITaero, I see what you mean about making an elliptical wing vs. making a 'regular' wing. I'm not very familiar with the term "tapered". What does it mean strictly? And what does the taper ratio indicate? I appreciate your response!

-Alfredo
 
liamksa
Posts: 301
Joined: Mon Oct 29, 2001 1:13 pm

RE: Why Is The Wing's LE/TE Dist. Shorter On The Tip?

Fri Sep 12, 2003 3:20 pm

The taper ratio is the ratio of the chord at the tip : the chord at the root.

So a typical cessna has a taper ratio of 1 (ie: rectangular wings). A wing which gets 'thinner' when you are looking at it from above has a taper ratio < 1.

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