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extended leading edge

F

flywhatever

MEMBER
Hey all, I'm rebuilding a cub, the wing's I thought were ready for cover, my IA overseeing the project and also a very experienced and great cub builder, suggests I extend aft of the leading edge skins, another 6" or so on the upper surface. My question is: Why would you want to do this? I know Heavy fabric causes scalloping between the ribs. Does this extension reduce the scalloping? Thx
 
yes, and it's about 15" you want...

the scalloping is caused by someone shrinking/installing the fabric wrong...

you need to tighten end to end FIRST in the bowed area that tends to scalp, NOT front to back! then there will not be much scallop
 
It makes for a stiffer wing. Soooooooo depending on how much twist you want in your wing put them on with the wing twisted the amount you want on the plane. You can still adjust but easier if they are set close to what you want.
DENNY
 
Unless you are experimental then you may be out of luck. Can’t get field approval on this anymore even in Alaska. (Unless something has changed).

This has been discussed quite a bit here. I will try to find it.
 
Personally I wouldn't recognize a stiffer wing and Jerry Burr debunked the scallops being a lift issue about 15 years ago. I like the extended metal because it protects the ribs from broom damage when sweeping snow. The top caps on my new ribs are a lot tougher than original Piper, though. Probably unnecessary now.

I wonder what the fabric life difference would be if there was reliable data available. All the lift tugging on the rib lacing through the years must take a toll.
 
Last edited:
Untrue, I know of lots of certified cubs with the heavy fabric applied and the extension of the leading edge over the top...


cubpilot2 said:
Unless you are experimental then you may be out of luck. Can’t get field approval on this anymore even in Alaska. (Unless something has changed).

This has been discussed quite a bit here. I will try to find it.
Click to expand...
 
What is the current FAA attitude? 10 years ago when I asked about extending LE metal I was told there would be no chance of any wing mods being field approved. Any wing mod including extended leading edge metal would need to go through engineering. I haven't heard that anything's changed since. Anyone have any current info? Nobody cares about yesterday's news.
 
stewartb said:
What is the current FAA attitude? 10 years ago when I asked about extending LE metal I was told there would be no chance of any wing mods being field approved. Any wing mod including extended leading edge metal would need to go through engineering. I haven't heard that anything's changed since. Anyone have any current info? Nobody cares about yesterday's news.
Click to expand...

That was my experience as well. I have one cub with it that was field approved years ago and like it.
I haven’t tried lately.
Scalloping for me is no longer an issue as I found that installing the wing fabric with sewn seams chordwise nearly eliminated them. 1/8 inch max.
 
mike mcs repair said:
yes, and it's about 15" you want...

the scalloping is caused by someone shrinking/installing the fabric wrong...

you need to tighten end to end FIRST in the bowed area that tends to scalp, NOT front to back! then there will not be much scallop
Click to expand...

cubpilot2 said:
That was my experience as well. I have one cub with it that was field approved years ago and like it.
I haven’t tried lately.
Scalloping for me is no longer an issue as I found that installing the wing fabric with sewn seams chordwise nearly eliminated them. 1/8 inch max.
Click to expand...
Start by shrinking over all the ribs first. Then after it is shrunk spanwise shrink between the ribs. This will lift the fabric and hold it up while you finish. This will minimise scalloping.
 
skywagon8a said:
Start by shrinking over all the ribs first. Then after it is shrunk spanwise shrink between the ribs. This will lift the fabric and hold it up while you finish. This will minimise scalloping.
Click to expand...
I agree. I will do an envelope, but prefer blanket for the cleaner finished look., It's about how you put it on and how you shrink it.
 
Got any in flight pics that demonstrate the fabric lifting? Are concave scallops while parked directly proportional to convex scallops under a lift load? I could imagine that some concave scalloping may prevent fabric lifting, but I have nothing to back that up. One way to keep the airfoil shape whether parked or flying is to use extended metal.
 
With the extended leading edge the fabric is basically stuck/adheared to the metal. So no ballooning at least at first.


Sent from my iPhone using SuperCub.Org
 
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