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Extended upper leading edge skins

This thread has drifted away from the original question about extended leading edges. IF the leading edge was only 1", the shape of the airfoil in the center of a bay behind the LE would be different than the shape of the airfoil at the ribs. These two airfoils would have different characteristics. The airfoil in the center would be slightly variable due to the ballooning effect of the fabric. According to experts this would be minimal. However, if the leading edge was extended back to the maximum airfoil thickness location, the characteristics would be consistent across the entire span.

Now if there was no difference between the short and the long leading edge, there should be no difference in performance between like airplanes with thick or thin airfoils. Thin or flatter airfoils tend towards efficiency at high speeds. Thicker airfoils tend towards increased lift at lower speeds. Do you want your Cubs to be efficient at low speeds or higher speeds? How would your Cubs perform if the entire wing's airfoil was the same as that with a short leading edge having that in the center of the bay shape?

Personally I will take the full sized airfoil over the entire span.
 
Got lifting eyes on your planes? It took about 15 minutes to make a simple squeeze plate camera mount for my lifting rings. It uses a 1" Ram ball mount if any local guys would like to borrow it. Point a camera at your wing tops and go see what they do.

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Sent from my iPhone using SuperCub.Org mobile app
 

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I am with Greg on this one, regardless of physics theorys, most of the doggyest Cubs I have flown over the years had one single factor ( besides weight) they all had lots of scalloping between ribs......... Imho.

Sent from my LM-X210 using SuperCub.Org mobile app
 
The question is at what speed are scallops lifted and how far does the fabric lift? And is it different than fabric lift on a wing with less pronounced scalloping? What factors determine rate and amount of total fabric lift? I’m sure the answer varies by airplane but perhaps a trend can be identified?

I suspect slats increase the tug on the fabric aft of conventional leading edges. VGs may as well but to a lesser degree. Interesting stuff. Maybe this spring I can get a couple of handfuls of slat wing owners to meet up and do some slow flying with video of the wing tops. That could be interesting.
 
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A HAH!! Here we go again...reading the Poly Fiber covering book, Page 20-21, there is a section that discusses scalloping. The author says SCALLOPING doesn't present any aerodynamic problems, it's merely a cosmetic issue. They continue to say that Medium fabric results in little or no scalloping. The use of HEAVY fabric creates deeper scalloping than MEDIUM fabric. Since I originally posted this rant I've read that their are folks that used to be concerned with scalloping, hence extended the leading edge, and NOW, have returned to not extending the leading edge, the original concept that scalloping doesn't affect anything to any Nth degree. Just, more food for thought...
 
2 cents worth. Years ago a friend of mine in Anchorage praised the results of his leading edge extension. He and his best friend flew nearly identical cubs together for years and they were pretty competitive. Being able to fly slower then the other when side by side was one such contest. He said that they were pretty much equal and would both stagger and stall about the same time with equal loads. These were basically stock airplanes and prior to VGs. He recovered his wings and extended the leading edge with no other modifications. He said that after that he could easily fly slower then his buddy who would be stalled out. He believed the airplane even felt more stable when slow. I had no reason to dispute his experience.

It was his testimony that convinced me to change mine.
All I can tell you is that mine a very good flying and very stable cub when slow.

Arguing the effects of scallops is about the same as down wind turns. I don't like big scallops and am very cautious in "down wind turns". I believe in both.

If I were selling covering material that could produce unsightly scallops and another that doesn't; without specific measurable evidence as to its effect; then I would probably say that it doesn't make a difference either.
 
Good answer...
2 cents worth. Years ago a friend of mine in Anchorage praised the results of his leading edge extension. He and his best friend flew nearly identical cubs together for years and they were pretty competitive. Being able to fly slower then the other when side by side was one such contest. He said that they were pretty much equal and would both stagger and stall about the same time with equal loads. These were basically stock airplanes and prior to VGs. He recovered his wings and extended the leading edge with no other modifications. He said that after that he could easily fly slower then his buddy who would be stalled out. He believed the airplane even felt more stable when slow. I had no reason to dispute his experience.

It was his testimony that convinced me to change mine.
All I can tell you is that mine a very good flying and very stable cub when slow.

Arguing the effects of scallops is about the same as down wind turns. I don't like big scallops and am very cautious in "down wind turns". I believe in both.

If I were selling covering material that could produce unsightly scallops and another that doesn't; without specific measurable evidence as to its effect; then I would probably say that it doesn't make a difference either.
 
One thing to consider is installation of the extended leaving edge makes for a very stiff wing. If do you have an older fuselage that may be tweaked it can be made to fly straight with rigging. Having extended leading edge can limit the amount of adjustment you can get out of the wing.
DENNY
 
They continue to say that Medium fabric results in little or no scalloping. The use of HEAVY fabric creates deeper scalloping than MEDIUM fabric. ..


This I would agree with....and light fabric, double covered produces very very little scallop! (exprimental) It's also going to be less apt to lift...since it's 2 layers....think plywood stiffness.
John
 
The fabric lifted between the ribs just a little on all the T-50s regardless of the condition of the fabric. The plywood leading edge went back to the spar which was at the thickest point of the airfoil so that the section which had fabric between the ribs was almost flat. Because of the leading edge the sag scallop which we have been discussing did not happen on this plane. Only the lift shape caused by the lower pressure on top. Loved that airplane. Light on fuel, flying solo it would fly off pavement in about 200 feet. Unbelievable for such a big airplane, but it did.
 
Bill, in the case of covering with heavy fabric the Polly Fiber manual says that with the blanket method, the aircraft will fly the same, it will just show a bit deeper trough between ribs...I'm still a thinking extending the leading edge is a moot point...
 
Cool beans. I flew a T-50 back in 1978...I can't remember what the fabric was doing, 'paying too much attention to being in one cool cat!

The fabric lifted between the ribs just a little on all the T-50s regardless of the condition of the fabric. The plywood leading edge went back to the spar which was at the thickest point of the airfoil so that the section which had fabric between the ribs was almost flat. Because of the leading edge the sag scallop which we have been discussing did not happen on this plane. Only the lift shape caused by the lower pressure on top. Loved that airplane. Light on fuel, flying solo it would fly off pavement in about 200 feet. Unbelievable for such a big airplane, but it did.
 
This thread has drifted away from the original question about extended leading edges. IF the leading edge was only 1", the shape of the airfoil in the center of a bay behind the LE would be different than the shape of the airfoil at the ribs. These two airfoils would have different characteristics.


Interesting discussion. Regarding the 1929 Fleet biplane article below: “nose ribs of a curvature different from the former ribs to prevent fabric sag are inserted between the former ribs.”

The Navy used Fleets so it’s possible the reference to “a wing structure that reduces the usual fabric sag” in the NACA report is referring to smaller “nose ribs” rather than full leading edges.

The Fleet leading edge is only 4 inches wide.

Best,

HT

 

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Fred Weick and the group were thinkers and doers. Tufting and testing a variety of aircraft airfoils in pursuit of knowledge. Must have been lots of accidents that formed their goals to understand flight. That Taylorcraft 23012 wing was later shown to have flow separation issues close to the leading edge that maybe the tufting didn't fully reveal. VG's to a great extent maintain flow at higher AOA. They do show the disturbed flow downstream of the aileron's pushrod slot which some have reduced by flexible lower wing seals.

A book about Fred that's a good read: https://www.amazon.com/GROUND-UP-Fred-Weick/dp/0874749506

Gary
 
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