Cooling Ramp Oil-canning

[apatti]

Folks,
Of all the places... I have an oil-canning problem with the cooling ramp. I am worried that with the exhaust booming in this area I will have problems down the road. Both with excess noise and cracks. I am seeking opinions on whether I should just cut my losses and go ahead and re-do it now. Or did others have trouble here and it turned out not to be a problem later.

Thanks,

 

[sf3543]

Mine cracked!

I have a QB RV8 and found a crack coming out of one of the rivets on the ramp after 159 hours. Since it was getting ready for paint, I made a pretty simple repair, as follows:
I drilled out the rivets along the bottom of the firewall. (Take a sharpie and draw a line across just aft of the rivet line, about 3/8 to 1/2 inch.)
By removing the hinge pin from the trailing edge, you can bend the entire piece down enough to cut the trailing piece off, on the line you drew. I then removed the stiffeners and hinge and fabricated a new piece out of .032. (The original is really thin.)
Then I put a chamfer on the curved piece, where it was cut, while it was still attached to the firewall by the top rivets.
Then, I riveted it back together. (With help, of course.) It really looks good and you wouldn't know anything was done, unless you are familiar with how it is supposed to be a single piece.
I'm hoping that the heavier piece will resist cracking down the line.
I have heard that this is getting to be fairly common for RV8s.

I don't think I would do anything unless you see a crack developing. It may never happen, even though it is oil canning now.

I guess you could bond a stiffener, or even another piece of aluminum to it if you felt like it. Since you have access to the inside of it. Maybe a piece of .032 or .020 with some lightening holes in it and bonded on with pro seal or JB Weld.
Good luck.

 

[jbDC9]

(Take a sharpie and draw a line across just aft of the rivet line, about 3/8 to 1/2 inch.)
By removing the hinge pin from the trailing edge, you can bend the entire piece down enough to cut the trailing piece off, on the line you drew. I then removed the stiffeners and hinge and fabricated a new piece out of .032. (The original is really thin.)
Then I put a chamfer on the curved piece, where it was cut, while it was still attached to the firewall by the top rivets.

Any chance you took a pic or two of this repair work, especially the curved/chamfered piece? I have the same job waiting for me; my QB ramp developed a crack at the 8(!) hour mark, and the thin sheet metal vibrates quite a bit at high power/low speeds. A quick patch or doubler over the crack might do the trick, but it'd be nice to have a whole new ramp of .032 sheet with better stiffeners to cut down on the racket.

 

[sf3543]

Will take pictures tomorrow

I don't have any pictures, but I can take a few tomorrow and then post them.

 

[Bill Dicus]

Oil canning

I believe Steve Raddatz put some foam in that area to dampen the oil canning. Said it decreased noise and vibration considerably aas I recall. Steve - correct me if I'm wrong - I know you had some similar solution. Bill

 

[DanH]

I used cast-in-place foam to make a plug that completely fills the void behind the ramp. Line it with plastic, dump in mixed urethane and slam the lid. After cure I popped it out and sheeted it with some lightweight glass fabric. Later I'll install it with a few dabs of orange silicone or pro-seal. I expect the ramp and floor to be "dead".

 

[sf3543]

Here's how I fixed mine

My earlier post gives the steps I used, but here's a picture. If you wanted to, I suppose you could drill out the rivets and use #6 screws and nuts instead. Since you need to take out the rudder pedals to rivet, it would be equally as easy to just get a new part from VAN's and just replace it, but I wanted the heavier aluminum there. Besides, I had the piece (used the cut out for the baggage door from the top front skin.) and got it done that same day instead of paying VAN's for the part, handling and shipping and the at least one week wait.
Good luck.

 

[jbDC9]

Thanks for the pic Steve; it helps to see a pic of this stuff, worth a thousand words and all that. Now I just gotta find the time to get it done...