Newbie builds a foam toy hauler/camper

[GPW]

... and more ... ( Oh No, not more ? )
I think once we find a readily available source for 4’ X 8’ sheets of Chipboard , we can better utilize this material to make the Smooth skinned campers everybody seems to want ... It just might come on a Big roll from the manufacturer ...
It may seem troublesome right now when new , but it is much MORE DENSE than canvas ... Frozen Turkey bird strikes , remember ...

Best lead so far ... http://www.papermart.com/brown-gray-chi ... =4661#4661

 

[Pmullen503]

I wonder how you would do the corners.

What about 2 or 3 layers of Kraft paper? You can get 60" wide rolls and it would go around the corners easier than chipboard. Apply one layer fore and aft and second layer at an angle to that. I cover foam airplanes with it all the time. A coat or two of high build primer and you can sand it to a smooth enough surface for silver paint. I use water based poly as an adhesive. 2 or 3 layers of 75lb Kraft would be very strong and as smooth as you could want.

 

[GPW]

PM, you know we used Kraft paper years ago over beaded foam wing panels that we’d hot wire . Much cheaper than Balsa skins and we loved the way it would shrink up tight . Actually we proposed the Kraft paper idea ( big thread probably) a while back , but it may have been too radical a thought for those that were just getting used to the idea of building a trailer from Foam ...
We’ve seen various thicknesses of Kraft paper , and it does seem like a good idea for skinning as long as you don’t mind the work of applying several layers ... or finding some that’s really thick ... We actually saw some really thick paper , sold as floor protection , but it was treated with some kind of waterproofing that MIGHT make it not work with white glue and foam ... Nobody tested it , so it may actually work ...
Paper covered foam campers could be Very smooth , strong Enough , and very easy to repair. Cheap too ... more money for Ballast ...

 

[Pmullen503]

I'll have try a test piece next time I cover a wing. Grocery bags as a source of Kraft paper. Cover one side with canvas, the other with paper and have at with a hammer to check the relative dent resistance.

I seem to recall someone covering a floor with paper. I wonder how well that held up.

 

[KCStudly]

That was Sharon's MyAway camper. I'm sure she will pipe up here shortly.

 

[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 ...