Aluminum expansion ...

[GPW]

Guys , we have a shedload of cargo trailers running around here... everybody and their brother in law has one .. Thing we noticed is some are terribly skin wrinkled in the Heat , and others are not ... Why? Could it be the time of the year the skin was applied ... ? Seems as if it was applied during the HOT weather it would be fully expanded (and flat) and only contract during cooler weather (staying tight) ... If applied during cool weather , it would start out flat and then wrinkle in the Heat ... Does that make any sense ???

[RandyG]

Every B-52 has wrinkled skin on the fuselage just below the wing root. It's caused by the stress from the wings pushing down, so when it is flying the wrinkles go away cause the stress reverses and the fuselage is hanging by the wings. I don't know if there can be similar stresses with a cargo trailer. Maybe you can pull one at 70 mph and see if the wrinkles go away.
But really, I think they wrinkle because it is such a long hollow structure with no curves to add any ridgidity. If they were made with a slight curve in the side like a wing, would it still wrinkle?

[Shadow Catcher]

There is thermal expansion and contraction. One method of preventing this is to use something like 3V VHB tape and not try and fasten the bottom so it can float to a small extent.

[OverTheTopCargoTrailer]

GPW

My screw less exterior has some minor wrinkles , though not that bad!!
It's all applied with 3M VHB glue.

I would say your theory is not correct because workers could not install siding in the full sun
It would be to hot.

Most factories have a temp of min 50 to max 80 deg from what I have seen.

If I had to guess I would say thinner .025 & .030 black or colored metal would tend to wrinkle more then
White .040 and .050 metal


Jerry

[GPW]

Thanks , appreciate the information !!!

[Quadriderdad]

Guys , we have a shedload of cargo trailers running around here... everybody and their brother in law has one .. Thing we noticed is some are terribly skin wrinkled in the Heat , and others are not ... Why? Could it be the time of the year the skin was applied ... ? Seems as if it was applied during the HOT weather it would be fully expanded (and flat) and only contract during cooler weather (staying tight) ... If applied during cool weather , it would start out flat and then wrinkle in the Heat ... Does that make any sense ???

Yeah I hate that! and I agree with this to an extent and I feel the metal gauge plays a big part as well. Mine had very few wrinkles on the day I bought it and it was snowing cold. Now days at anywhere from 80-100 degrees out it looks terrible. Sometimes I even think about installing fiberglass lamination panels like you would see on an rv exterior just to get rid of the ugly waviness also the thought of less cold transfer is alluring. Also I have seen this expansion in a slightly different application where as horizontal metal siding on the exterior of an rv will buckle and bulge if all the conditions are not right.

In regards to 'overthetops' comment...I'm not to sure how other manufacturers operate but at out facility inside temps run easily 80-90 degrees when it's 100+ outside and down to maybe 40-50 at times when it's freezing out. Our bay doors are constantly open and closed with materials coming in and out so depending on your location inside the plant it can be quite a weather pattern inside I definitely think the metal gauge plays a part in this but I also think that the expansion and contraction will be there regardless if the material is in direct sunlight or not.

[GPW]

Quad , it’s been really Hot lately and we see a lot of them wrinkled pretty good (badly) .. but then a lot we see are drum tight, even in this heat ...??? We just never saw any wrinkly ones in the Winter... I’d have noticed , with all the CTs around here, there’s lots to look at ...
Thanks for the “inside” info ...

[OverTheTopCargoTrailer]

I would still bet my last dollar on the thickness of the metal & the color black


When have you ever seen a large truck box with wrinkles ? NEVER
They are all .040 and .050 skin thickness.

When my trailer sits in full sun , the roof temp hits 150 deg, that's what I meant
Most manufactures would not , cannot install under those conditions.
My silver roof sheet does not wrinkle and is 8 x 18 ft
So there is another question ??

[Quadriderdad]

It would be interesting to do a comparison of waviness vs. gauge thickness. I have no idea what mine is. I'm getting ready to cut out a window hole soon...if I remember I'll measure the thickness before I scrap the metal. I'l report back then

[RandyG]

What is the skin attached to on a cargo trailer? Wood studs?

[GPW]

Randy , most of the ones we’ve checked out around here were Al skins riveted to steel frames ...

[aggie79]

Quad , it’s been really Hot lately and we see a lot of them wrinkled pretty good (badly) .. but then a lot we see are drum tight, even in this heat ...??? We just never saw any wrinkly ones in the Winter... I’d have noticed , with all the CTs around here, there’s lots to look at ...
Thanks for the “inside” info ...

I used 0.040 aluminum on my teardrop. The aluminum was installed in the winter. It is floating except at the perimeter and around openings. I do get very slight oil-canning when the temperature gets over 100 degrees in the summer. There isn't much physical change that indicates the oil-canning but the images in the reflections start to have a carnival "house of mirrors" effect.

In the winter, it tightens back up.

[Quadriderdad]

What is the skin attached to on a cargo trailer? Wood studs?

Mine is aluminum skin attached to steel studs with 'tek' screws. Studs are 24 o.c.

[Prem]

No wrinkles on mine any time of year. (It's taped and rivet-less.)

Prem

[GPW]

Prem , you have a date code when it was made ... what time of year ? Just curious ...