Question for the experts

[rpzo]

I was hoping that one of the experts that regularly view this board could explain what I am seeing in the attached image. This shot was taken from the pits during Saturday's race last year. In particular I am looking at the blue area just below the checkerboard pattern that runs the length of the fuselage.

To my uneducated eye it looks as if the skin of the aircraft is rippled, something that is not noticeable on any of the other shots I have of Furias from last year. Optical illusion, G-forces on the airframe, or something else?

Rick

[AAFO_WSagar]

Boy Rick,

I'm not, by any means, an expert and it's hard to tell from the image if it is an illusion or not but it sure does look like what I've heard called "oil canning"

You'll see it on many shots of Rare Bear, though not as bad, I believe the area that it happens on her is just behind the trailing edge of the wing, up about a foot on the fuse.

I think, years ago, it was much worse until a shot, I believe it was by Neal Nurmi, revealed a large area of deep oil canning..

Tough call to whether this is an illusion caused by oil streaks or something or, ripples..

I'll give Bill Rogers a heads up and have him take a look.. Do you have a larger version of the image? Maybe a crop with just that section??

Shoot me an email if you do.

Wayne

[rpzo]

Wayne,

In laymans term what is oil canning?

I'll rescan the image at a much higher resolution and e-mail you a crop of the area in question later this evening or this weekend at the latest.

Rick

[King]

I would say that is "oil canning". And very deep "oil canning" at that!

Caused probably by g-forces, loads and mostly torque of the mighty 4360.

That engine is trying it's hardest to roll the entire airplane. The tail, attached by the long arm of the fuselage, is trying it's hardest to keep the engine from doing that along with the wings. Whalla, torsional "oil canning".

I do not know the sea fury structure at all, but this would disturb me somewhat.

Thin skinned airplanes will "oil can" (flex, distort or deform) under loading conditions in-between ribs, stringers and other lighter structures. Go out and fly in any general aviation aircraft made from aluminum and you will see this happenning, especially on the wings.

[rwflyboy]

before Risky ate her

This was taken before Risky and her had a minor disagreement on position and altitude....Risky's prop struck the elevator/horz. stabilizer.....

[AAFO_WSagar]

Originally posted by King
I would say that is "oil canning". And very deep "oil canning" at that!

Caused probably by g-forces, loads and mostly torque of the mighty 4360.

That engine is trying it's hardest to roll the entire airplane. The tail, attached by the long arm of the fuselage, is trying it's hardest to keep the engine from doing that. Whalla, torsional "oil canning".

I do not know the sea fury structure at all, but this would disturb me somewhat.

Thin skinned airplanes will "oil can" (flex, distort or deform) under loading conditions in-between ribs, stringers and other lighter structures. Go out and fly in any general aviation aircraft made from aluminum and you will see this happenning, especially on the wings.

King,

Sure does look like it doesn't it.. What's strange about it is, I've got a ton of pictures of the airplane in similar location on the course, pulling, I'd think, similar amount of G's... no evidence of the oilcanning.....

I'm gonna get on the phone right now with Bill and show him this photo and see what he thinks..

RPZO: King answered the question about what is oil canning pretty well... The term is pretty easy to see where it came from when you think about it.. squeeze a can slightly, it dents and comes back with no lasting deformation...

About what we see here.. or in the case of oil canning..

Wayne

[rpzo]

The next laymans question I would have is how serious of a problem can this be and how common is it? I can't imagine that over time this would be too good for the aircraft. At some point would there be a catastrophic failure if it wasn't corrected? (Given the G-loads that are put on these planes)

[AAFO_WSagar]

I just got off the phone with Bill Rogers and what we see here is normal for all Sea Fury airplanes.

The "oil canning" in this photo is very much highlighted because the lighting was just right to show it and actually amplify it from what is really there.

Apparantly this is a compression of the skins caused by the horizontal stabilizor pushing down to keep the plane level. The ripples are barely noticable, unless the light is "just" right, which is why we're seeing them so clearly here in this photo.

Bill tells me that the 737 is also an airplane that does this at high speed and, again, this is normal. The skins on the top of the airplane are in stretch at this mode, the skins on the bottom are in compression.

Again, all normal, all OK..

Though this photo is frightening looking, it's the lighting that makes it so, not a problem in reality...

If you look closely at this picture http://www.aafo.com/gallery/week/0205-124.jpg (lighten the picture if you can't see it) you'll see the same distortions here. The reason you can't see them is because of where the light is coming from. In the other picture, the light is exactly at the tail causing it to only highlight the area of the ribs, where there is no "denting"...

Also, look closely at this shot of Critical Mass.. http://www.aafo.com/gallery/week/1015-124.jpg and you'll see the same thing.. compression is very slight and not that noticable, unless we have the exact right lighting....

Wayne

[rpzo]

That's a relief. I will accept the judgement of the experts and I even learned something in the process.

Quite a dramatic difference though that the lighting makes.

Rick

[Sailing South]

This truly looks scary, the Bear does the same thing. If you think a 737 is bad, you should see a 757 sitting at the gate. Just sitting there on the ground you can see wave after wave. Every aircraft is a little different but it seems they all do it, whether flying or sitting.

Scott Litster
Bear Tech

[RandyGoss75]

Oil Canning

Scott- Neal Nurmi has some VERY interesting pictures of Rare Bear's fuselage oil canning- from the Bakersfield race I think.

All the best, Randy