Sandwich insulation thickness VS wood thickness

[tcolar]

So 1x2 are like .75 thick whereas 1'' insulation is ... 1''

so how do you deal with that (not flat) ... i would guess leaving the gap would remove a lot of the strength of the sandwich

Thanks.

[Ageless]

Foamboard is made 1/2", 3/4" and 1"

[tcolar]

They have those sizes for the white foam -rtech - buut is that good for a sandwich ?

The rigid foam -pink- is avail in 1 1/2 I guess that would work with a 2'' wood, kinda spendy though.

[tcolar]

So the big box stores have rtech in 3/4 but that kinda foam is kinda messy and doesn't feel like it would be that good structurally.
HD has pink foam in 1 1/2 which would work although that makes for kinda thick walls.
Can blue/pink foam be bought in 3/4 somewhere ?

[aggie79]

I used the "white" insulation. It is a little messy, but works well. The "blue" and the "pink" are available in 3/4" thicknesses in our area. The reason I chose "white" over the others is that the white compresses more. Insulation tends to run wild on thickness - usually slightly greater than 3/4" - but the "white" compressed nicely to fit between the 3/4" framing.

I glued my foam too, but the majority of the strength of a stressed panel or torsion box is in the skin.

[tcolar]

On the white stuff did you remove the plastic film or nit ? Did you use special foam glue ?

[john]

I ripped 1/2" plywood on the table saw for my (battens?) studs -- the spacers between the skins of a built-up wall.

Advantages:

--It was cheaper than the 1x3's as one piece of $12 plywood would make around twenty 1/2"x2" studs each 8 feet long. That is 160' of length. So one piece of plywood could have provided me with all the studs I needed.

--I used two sheets of plywood, though, because of another advantage -- I could cut the studs to the width I needed. In some places like along curves I found additional width useful. In other places I used the extra width to create a skirt along the sides of the camper or as extra support for the fenders.

[planovet]

I used all three...blue, pink and white. Don't ask me why but it just worked out that way. One was thinner than the others but I can't remember which one. I did not glue mine, just wedged it in between the studs. The walls will hold it in place and no noice if you have a tight fit. And yes, I removed the plastic film.

[aggie79]

On the white stuff did you remove the plastic film or nit ? Did you use special foam glue ?

I removed the plastic skin and the mylar foil. As far as glue, I used PL Premium - just a few dabs.

[Cliffmeister2000]

I used the white stuff. Didn't remove the skin. It worked great. I remember seeing a post where somebody ran the pink stuff through a surface planer.

[john]

Do you not have 1/2" insulation available at Lowes or HD?

I turned the foil to the outside to aid in reflecting heat. I have found it is easier to heat the camper than to cool it, so reflecting the heat away when I want to cool it is the best way to go for me.

I did not find it necessary to glue anything to the insulation. It just rides inside the wall.... insulating.

The studs, ply sandwich, and things like cabinets, walls for bathrooms, and benches add more strength than expected.

[kennyrayandersen]

It's best if the foam is glued to the facesheets (skins) since that is how the outer skins become effective together. Without the foam reacting the shear the facesheets both act independently (not bearly as strong). In that case, it makes sense to remove any kind of coating or plastic that would prevent the foam from sticking to the skins.

You can also plane the wood to match the foam. It also appears that there are some insulation companies that make the foam in big blocks that can be custom cut, but I haven't figured out how expensive they are.

[Nobody]

When I built my TD in 2006 I had no problem finding appropriate thicknesses of 'closed cell' foam board locally. We have a large HD within 3mi & a new Lowes approx 6mi away. Both had a selection of the pink (Owens-Corning) & blue (Dow) from 1/2" to 1 1/2". I used 1" under the floor, 3/4" in the walls & two layers of 3/4" in the top/front. Since my spars are approx 1 1/2" square (ripped 2x4's) the two layers worked better on the curves & I only had to 'kerf' the foam in a few places for proper fit. A few pix -

[john]

I live in NC, but within 5 miles of the VA. state line.

The NC Lowes/HD had different selections of foam board than the lowes/hd in VA.

VA. had thicker stuff than NC.

[kennyrayandersen]

you can even get on-line and check the inventory. What you will find is that it varies by store location and also region. Down south, it's hard to get the 2 inch thick stuff -- most of it is 3/4 or 1 inch. They may be able to order stuff in, but usually they want you to order a lot of stuff (like a full pallet).