Sandwich adhesive question.

[jhouk2000]

I am planning on building my TT with sandwich walls. (1/8 luan, 3/4 plywood framing and EPS insulation, 1/8 luan)

What would be the best adhesive to bond these 3 materials together?

Should the insulation be bonded to the inner and outer skins also?

Has anyone had problems with the insulation squeaking?

[bobhenry]

The extruded polystyrene is usually cut to fit snug and will not move. No movement no squeek. The pink ( owens corning) and blue (dow chemical) both have a thin plastic coating so the face that would slide before it squeeked. The Foam bead board might ??? . If you want to dab the foam in place a spot or two of construction adhesive will hold it but a good tight fit makes it unnecessary. the wood to wood sheet adhesion can be yellow carpenters glue or gorilla glue (Polyurethane adhesive). Yellow glue clamped over night, gorilla glue 1-2 hours per manafacture.

Gorilla glue just came out with a fast drying version 1/2 hour - 1 hour depending on the humidity. If you are wiring leave a chase I wish I had used some 3/8 or 1/2 inch pvc in the wall for electrical. The are 1/2 depth plastic electrical boxes that will allow access to the wiring after the inside skin is on. Think out the electrical scheme before you lay on that inside skin and save yourself a lot of grief.

[toypusher]

I would recommend taking the plastic film off and using Titebond II or II and just glue everything up on both sides. If you are going to use Gorilla Glue (or any polyurethen glue) make sure and test it on the insulation first. Some of them at least will eat into the insulation.

And Bobhenry's advice about the electrical is excellent. I really pays to plan ahead.

[asianflava]

I used epoxy and epoxy thickened with micro fibers on mine.

[Steve Frederick]

For a turkey sandwich, miracle whip... ...For a T/D wall, I've used Titebond 2, and PL2000. As Kerry indicated, some foam has a film on it to prevent damage during handling. It will not bond to glues very well, so remove it.

[davefullmer]

I have noticed that everyone seems to be using the polystyrene bead foam (pink and blue).

My question has been why not use the Poly Eurethane board? Poly Eurethane has a R value of 7 per inch thick and I don't think poly styrene comes close.

Any comments on this?

Dave

[toypusher]

I don't recall seeing any Poly Eurethane board around here.

[bdosborn]

I used the Polyurethane in my roof, it worked fine. I liked it a lot better than the polystyrene insulation I used in the walls as it cut cleaner and didn't leave little white bits *EVERYWHERE* in the garage. I used two layers of 3/4" and put the foil towards the outside and the inside. The only down side to polyurethane is that the foil blocks a stud detector.

Bruce

[asianflava]

For my sidewalls, I used a rigid polyisocyanurate foam board with a reflective facing on one side. For the roof, I used polystyrene (the little balls held together) because it was more flexible.

[ARKPAT]

I used solid polyurethane foam sheets from Insulated steel doors. "Gorilla Glue" to glue up after trimming up the sheets.






Pat

[Steve Frederick]

I have noticed that everyone seems to be using the polystyrene bead foam (pink and blue).

My question has been why not use the Poly Eurethane board? Poly Eurethane has a R value of 7 per inch thick and I don't think poly styrene comes close.

Any comments on this?

Dave

Foil and glue issues? I've never tried it though. I'm starting a new project, maybe I'll do a test.

[bdosborn]

For my sidewalls, I used a rigid polyisocyanurate foam board with a reflective facing on one side. For the roof, I used polystyrene (the little balls held together) because it was more flexible.

Oops, polyisocyanurate is the stuff I used in my roof, not the polyurethane. And yeah, it didn't bend nearly as well as the white stuff. That's why I used two sheets of 3/4" to make up a 1-1/2" space.

Bruce

[Bronco302]

I'm doing sandwich style 1/8" skins on a poplar frame. One thing I have found around Knoxville is the 3/4 blue and pink stuff is thicker than planed 4 sides lumber so I'm using the expanded stuff(also was given a bunch). I have the means to work rough lumber but didn't want do all that ripping and planing. For my glue up I'm using PL Premium Construction Adhesive and came across this web site today http://www.simplicityboats.com/pl_premium.htm some pretty good hands on info. HTH

Joe

[jeepr]

Titebond III is good stuff.

[davefullmer]

Bruce wrote:

Oops, polyisocyanurate is the stuff I used in my roof, not the polyurethane. And yeah, it didn't bend nearly as well as the white stuff. That's why I used two sheets of 3/4" to make up a 1-1/2" space.

Actually, Poly Eurethane is made by mixing Polyol and Isocyanruate together under high pressure so it is the same thing.

The reason I ask is I have worked in the Poly Eurethane manufacturing industry off and on since 1981. When I built the addition on my mobile home I salvaged garbage bag test shots from the factory I worked at, sawed them in slabs about 3 inchs thick and just a 1/4 inch wider than the stud openings and stuffed the pieces in the studs and the rafters. You wouldn't believe how snug and cozy this made the home. I installed a wood burner in the new addition and until about 2000, I never burned more than a full cord of wood in my stove. This was the only source of heat we had in a total of 1500 square feet of house here in West Tenn.

Then in 2000, I decided to install a central heat and air system but we still use the wood. Now I fill my 10 x 10 woodshed almost full and have 2 years supply of fuel to burn.

I was wondering if anybody had used it and if there were any issues. Like mentioned, flexability, or glue. As far as the foil, I would think you could remove it. Just be careful about getting rid of the scraps. Don't burn them because the Iso side of the chemicals puts out a fume that shuts off the air supply. It is fire retardant, but not fire proof usually.

By the way, that 1 1/2 inch that Bruce put in the roof would equal an R value of about 10.5. That is very close to 3 inches of fiberglass bats.

Dave