Aluminum bubble?

[Tripmaker]

Although some have glued their AL to the sides I went with the majority of advice and floated my AL skin. Yesterday I had it out for the first time in the sun to wash it and after a short time the AL expanded to the point that it, for lack of better term, bubbled out from the sides giving it what has been called an oil can look. I had what I would guess to be about 1/2" or more of space between the skin and the plywood when I would press on it. Did I do something wrong or is this what it is supposed to do? The AL is fastened at the bottom but at the top is held in place by the trim which is screwed in only on the roof edge. After it cooled down the AL went back to normal. I haven't named it yet, maybe I should call it the "Oil Can Camper". Anyone have any thoughts or suggestions?

[toypusher]

I am far from being an expert, but it is my understanding that what you are experiencing is normal.

[Keith B]

This is why they put creases in duct work...it's going to happen with heat/cool, contraction and expansion... You may have made your joints TO GOOD.. I know some talked about cutting it a 1/4" short all the way around to help prevent this...if that works or not I cannot tell you... I think regardless of paint, aluminum, etc. there's going to be pros and cons on how it looks, how it performs, etc., etc... I think what you're experiencing is probably just the nature of the beast.

[madjack]

TM...we floated our AL...we had some slight oil canning behind the door and above the fender on a really hot day...it did this once and never really seemed to doit again...Talking to the CampInn folks, they said this is somewhat normal...like I said...ours did it once and then it seemed to "settle" into place and not do it again in a noticeable fashion...
madjack

[tonyj]

Mine does the same, but I expected it to since it is fastened and sealed around the perimeter. If someone points it out as a flaw, just say it is supposed to do that, and lead them on to the other craftsmanship on the trailer.

Aluminum sheet is going to expand, and at a different rate than the wood under it. I'm still glad I followed MJ's suggestion to float it.

[Tripmaker]

Thanks guys. Like I said I don't know what is normal. I only saw one TD before I started my build so I don't know what to expect. I'm guessing that the silicone under the trim is keeping the sides from sliding upward when it heats up.

Has anyone tried putting on an automotive type trim strip across the middle. I don't know if that would help or make it worse. That might cause two bulges a that are even more apparent than what I have now. Just thinking out loud.

[madjack]

...It would probably help...I don't think it would cause anything worse to occur and would help anchor the skin in one more place...
madjack

[reiltear]

When attaching solid wood table tops to bases it is a common practice to screw them through slotted cleats, so that wood in the table top has room to move a little with humidity and temperature changes.

If I was in your situation, I would make holes in aluminum somewhat bigger than necessary for the screws under the trim, so aluminum can move with temperature changes. Don't know what it would do to the weather-tightness, though.

Jus' my 2 cents,

Ilya

[Cary Winch]

What thickness aluminum? We found that the thicker the aluminum the less noticable the bubble is. With a .020 thick aluminum it is really noticable but with the .040 we use it far less noticable. It is still bubbling out but much smoother and somewhat resisted by the thicker metal.

This is why it can't be glued on. Had you glued it on the bubble would have delaminated your glue in the largest area and left a permanent bubble. The aluminum will grow in the sun.

Cary

[Tripmaker]

Thanks guys. Sounds like what I am experiencing is normal.

Cary, my AL is .030

Ilya, The AL on the sides is not fastened at all at the top, it is held on by the trim which is screwed along the roof edge. I think the silicone under the trim is restricting the movement of the sides causing the bubble.

Thanks for your thoughts guys. Like I said I didn't know what to expect with this being my first TD. I'll be seeing many more TD's May 17 at our Turkey Run Gathering. Looks like there will be 21 of us.