Underbody pop rivets.

[Wingeezer]

Just wondering if any owners who live in Canada or Northern USA have experienced this .....

I have found that more than half of the pop rivets used under the trailer - the ones that secure the wrap around painted panels to the bottom skin and the ones that secure the belly pans to the trailer frame have corroded away to the point of failure.

In at least one case while our trailer was parked in storage I went to check it one day this summer and found the corner of one panel had dropped right down the the ground! That was when i started examining all underbody pop rivets.

Looks to me that the problem has been caused by road salt + dissimilar metals, (ie steel frame & steel mandrel stubs in the rivets together with the aluminum panels.)

We do travel south each winter and I imagine that is where the problem is happening as we usually have no choice but to drive on wet salty roads for the first day of our trip.

I have replaced all the rivets and in areas where the alum. skin has corroded badly around the rivet hole, added large square washers cut from
one inch 1/8" alum strip.

Certainly from now on I will be trying my best to give a good wash to that area when we get to our southern destination - as soon as we stop at an RV park that allows it ....... or maybe after dark!

I always do give it a good wash and wax, but obviously have not paid enough attention to the underside.

Actually suspect that salty water is actually finding its way into the underbody and laying there. Reason I say this is that apart from the rivets & rivet holes, I have found that especially towards the front of the trailer, several of the painted wrap panels are rotted through where they contact the transverse curved trailer ribs. This is even the case on a panel that was just installed new by JC only two years ago.

It is oner thing to give the exterior a good rinse, but pretty hard to flush any salt out from behind the panels.


Guess we should move to Tucson instead of just visiting .... or leave the trailer there!

Brian

[idroba]

I think the underbody belly pan and it's rivets have always been a problem, no matter what climate you are in. Even with no salt, I have found the rivet heads pull out by fatigue through the flexing of the metal around them, which is quite soft. I once had my belly pan try to peel off altogether when I was on the Ohio Turnpike. That was a fun experience which I will never let happen again.

I think the only solution is either fender washers under the rivets (large head ones) or strips of metal holding the pan as a sandwich as you have done. That and seasonal checking and repair before too many pull out of rust off is the best policy.

[dznf0g]

+2 what Idroba said. Mine has never seen salt and I have had a few rivet heads WEAR THROUGH the belly skin. I repair as Wingeezer does, with squares cut out of the thicker scrap skin aluminum.

[TG Twinkie]

It is electrolysis that cuts holes thru the belly pan. With the rivet fasten to the steel frame and the thin belly pan material, plus A$ used galvanized washers about a half inch in diameter, the pan was the first to go.
I cut washers from a sheet of fiberglass, then sandwiched them between fender washers and the belly pan. Using 3/16" rivets. Completed the job 3 years and 18,000 miles ago and it still looks good.

[Sneakinup]

Having just installed my belly skin today, I did what others have done by making aluminum washers to cover the hole and allow the new rivet to hold better. I rubber coated my frame prior to putting the skin back on in the hopes that will slow down the corrosion issue.

I also added long strips of aluminum on the edges to get a better hold. Pretty much every rivet hole was 4 times the size of the head of the rivet. The only thing originally holding the belly skin in place was that it was sandwiched together and lots of Vulkem.

My original belly skin and what I did today....

[dznf0g]

I found no usual signs of electrolysis. Mine had vibrated through...no question.

[wahoonc]

Older trailers are more prone to have the electrolysis damage. I used large flange rivets, cutout washers and in some cases screws with a rubber gasket.

Aaron

[Wingeezer]

Well, it sounds as though I have lots of company!

Seems lots of folks feel that the problem is vibration rather than corrosion and maybe both can be a factor

The reason I thought it was corrosion encouraged by salt, was that in many cases there were whitish crusty deposits around the failed connection and also the original rivet holes in the aluminum were much larger than original and what was left of the metal of the panel in the near vicinity of the rivet hole was paper thin and flaky. That was why I had to use 1" square pieces of aluminium trim as large washers when I re-riveted.

The original pop rivets used in most locations had extra large heads - in many of the failed connections, the heads were left still adhering to the panel, but the body of the rivet was gone! You could just pick the rivet heads off with your fingernail!


Brian

[deauxrite]

Add me to the list. I used two aluminum yard sticks to bolster my belly pan and reiforce the area. I decided on the aluminum yard sticks because I wanted to use aluminum (and they were cheap) and I wanted to use one piece material if possible to prevent the tear out that I was seeing.

[wahoonc]

There is an aluminum "stick" with holes already drilled in it. It is called termination bar. You can buy it at a commercial roofing sales center (ABC Supply is probably a good start).

Aaron