Newbie builds a foam toy hauler/camper

[Pmullen503]

Just noticed this. It's been subzero around here and it looks like the foam contracted in the cold more than the wood structure it's attached to causing the wood structure to stand out. I suppose foam and wood have different thermal expansion coefficients. Anyone else seen this?

[GPW]

Curious , it never gets sub 0 here , so we’ve no chance to notice this effect ... How did it look when it warmed up ... ???

[Pmullen503]

I'll let you know in May when it warms up!

I spent a lot of time sanding and filling to make the foam flush with the wood structure so I hope it comes back.

[GPW]

Likely it will ... it always expands with heat , and is the reason it heals itself ... Considering the nature of foam ... it’s mostly AIR ... trapped in many little plastic balloons all glued together, so when the air expands the balloons expand , in the extreme cold , the opposite happens ... The self healing is just “balloons that have been “compressed” and the air in them also compressed , so when heated it all expands again and Bob’s your uncle ... self-healing .... no magic at all here at Foamwarts...
PM , we will be awaiting May with much anticipation ... I guess you will be too eh ???

[Pmullen503]

I actually looked up the thermal expansion coefficient of EPS.

My 2" thick foam should shrink about 0.050" with a 70 degree temp drop which is about how much it appears to have shrunk.

[ghcoe]

I have noticed some of the same effect on my front wall where it attaches to the side walls. Especially near the floor. I concluded the same thing, that the foam wall is moving at a different rate as the floor. On my next build I am planning on doing my canvas edge overlaps at 2" instead of 1", this should hide any contraction/expansion lines. On the other hand I have used flashing for my door openings and hard points and have not noticed any issues with those areas. The flashing is however able to expand and contract with the foam since it really has no depth into the foam such as a foam block would have.

[Pmullen503]

Nice thing about canvas and glue is that it stays somewhat flexible and can move with the material underneath. I'm not concerned structurally. Not sure what can be done asesthetically to avoid this other than a paint scheme that makes it less noticeable. Not important to me, I prefer a workman like finish but some are really trying to get a high level of finish on a foamy. It will be interesting to see if it disappears when it warms up.

[GPW]

Ever notice this happens with those Metal trailers .... tight skinned when Cold , Wrinkly when hot in the summer ...