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Oil Canning W-1204B Skin

joedallas

Well Known Member
Oil Canning

I know this subject has been discussed many times and for the most part I have had it in control to a acceptable point.
I finished my wing tanks and finely closed up my skins on the top of the wings a few weeks ago.

The W-1204B Skins at the outboard end of the wings have Oil Canning that has caused me not to get a good night sleep since then.

This area is 13.75" by 23.1" and is a simple span design ( one side at the end of the wing and the opposite on the last outboard wing rib ) and should provide about 22.93 lbs of lift.
It is also the largest and most flat area on the top of the wing.
The span on the wing ribs is only about 11.6" ( 2.15" less than the W-1204B span ).

I went out to the shop today and removed the W-1204B skins and will order two new ones from Vans on Monday.
Has anyone had the same problem with this or maybe the dimpling of my skins in the problem.
I will make a stiffener out of the top 1.5" of two new wing ribs.

Any Suggestions are welcome

Joe Dallas
 
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The Fix

The Stiffener to control my Oil Canning of the W-1204B Skin

A_15_01_05.jpg


Link

http://joesrv12.com/Builder Log/al_15_01.htm


Joe Dallas
 
I have similar oil canning in that location on both wings, and I suspect it's probably quite common. It's probably got something to do with the way the twisted skin that forms the underside of the wingtip pulls on the ribs. Whatever the cause, the plane flies fine.
 
I have also suffered from this on one wing tip (the other was fine). I put it down to not fluting/shaping the end rib and W-1204 correctly although it could also have been building it in the cold and having a heater next to me meaning it didn't 'can' until the temperature evened out later, which would explain why I didn't notice it at the time :(

Due to the build space I have it was done in the dark corner of the shed with little room and working in awkward positions, I wasn't until after I had painted the wing I noticed, the shiny paint showing up the dip more than the flat primer.

I didn't have time to fix it then (fuse kit was about to turn up and I needed the space) so I asked my inspector to look at it. His view was that it would fly ok and doubted this blemish would affect performance that much (given some of the fabric aircraft he inspects).
More important will be whether I can put up with the look of it once all put together on the field, it may not be that noticeable or it could stand out like a sore thumb.

A suggested fix was to use shaped foam blocks inserted through the rear holes into the end cavity to provide support. Although I would probably remove and re-do the wingtip if it bothers me.

Who knows, it might even oil can back up once in flight or after a few day/night temperature cycles, although I doubt it with my luck.

This is what my wing tip looks like, I just wish I had noticed it before painting and when I still had time to fix it. :mad:
 
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Cosmetic problem

I think that Robert is right

After taking off the skin I put a straightedge across the last wing rib and the flange of the W-1204-L.
The W-1204-L top flange was not on the same plane as the top of the wing.
I was able to tweak the top flange of the W-1204-L flange and alien it with the plane of the top of the wing.
I may have caused this problem myself by dimpling the flanges for flush rivets.

For you who have not installed the top W-1204-B skins, I would cleco and not rivet them until the W-1204D Wing tip close out is installed.
Then remove the top skin and check the angle of the top flange and tweak if necessary ( pinch or open ).
MY View

Jon
Thanks for sharing your photo, there are a few more that have this problem and don't want to post it.

I wish more builders would share the problems so we can learn from them.

Fact: Over 49% of us builders are below average builders.


Joe Dallas




I have similar oil canning in that location on both wings, and I suspect it's probably quite common. It's probably got something to do with the way the twisted skin that forms the underside of the wingtip pulls on the ribs. Whatever the cause, the plane flies fine.
 
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I wish more builders would share the problems so we can learn from them.

Fact: Over 49% of us builders are below average builders.


Joe Dallas

I agree Joe; both that I enjoy the sharing experience here and that 49% of us are below average builders (...and pilots, too!). :cool:
 
I agree Joe; both that I enjoy the sharing experience here and that 49% of us are below average builders (...and pilots, too!). :cool:

Haven't noticed oil canning in this area on our previous three builds at Clear Springs HS but d*** it, right after reading this thread and examining the recently completed wings on our 4th build, one wing is ok and the other has a severe case. Alternating pressure with one hand just inboard of the outboard rib and another hand on the upper tip skin and you can play it like a drum. Hummm... replace or foam... can't leave it the way it is! Not withstanding, our "oil canning" tip skin now raises the below average builders percentage to 50% (mentors only... not the students).
 
The oil canning on my wings is about the same on each side, and not very deep. Only noticed it after painting and not worth trying to fix now. Still annoying when you're trying for perfection.
 
Average is 50 %

One thing good about this statistic is we can never get to 50 %

This Site helps how good that 50% builder is.

Joe Dallas



 
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