Expanding foam insulation

[SpottyDog]

Hello Everyone,

I am a new member and new to the teardrop world.

I am looking to build a teardrop and have been looking at lots of them in this site for ideas. They sure look nice!

One thing I have thought of is whether anybody has tried using expanding foam insulation when building their teardrop?

My thought was to frame the walls with 1x2 material. I then could fill the cavities with expanding foam. This I think would help to add strength while saving some weight and of course provide some insulation.

I would probably construct the walls on a big table before attaching them to the trailer frame. Once the walls were attached I would then put in the roof spars and the inside skin. Then fill the rest of the cavities with foam.

What are your thoughts?

Thanks,

Dan

[Woodbutcher]

Welcome Dan, If I remember right someone was doing some test panels using expanding foam. But I believe they put the skins on and made 2 holes on one side. One to fill the cavity and the second to gauge how full it was getting and an escape to keep the expanding from bulging the wood. You might try the search section or wait till one of the experts chimes in.

[toolman]

Welcome to the forum!

I cannot see any advantage in doing what you described over purchasing insulation sheets at HD or Lowe's. I think it would be more expensive to use the cans. A 4x8 foot sheet costs around $11.00 to $13.00 a sheet, depending on thickness.

Jerry

[John Ayers]

Hi!
To be honest, I'm not sure about TD's but there are some issues with residential construction you might want to know.
Spray foam obviously grows once it's exposed to oxygen... and hardens when it's finished. Once a home owner came in behind my crews and sprayed it to seal the air gaps between his studs and the windows. After it hardened, he could not open his windows anymore, and he had voided his warranty. I have used spray foam before, and it's messy and will stain the wood if it drops on it because of the high concentration of polymers. I would not recommend it to you based on my experience with it...
... but there is a different material that's a new "green" material I've used as an icynene substitute for homes that's, flexible, non toxic, and UBER expensive. Not something I'd do for a TD because of the price tag, but it's really cool.

[H-Balm]

What ever you decide, be careful!

That spray foam can be great, but it is SO AMAZINGLY MESSY if it gets on you!
Also, before you crack a can, plan out all you locations.
Once it sets a bit you can't ever use that applicator straw again.

[OuttaHand]

Take a look at the build journal I have for our "Little Tow" that I'm building:
http://webpages.charter.net/outtahand/littletow/index.htm

I have used expanding from (Great Stuff brand mostly) a LOT in the build. I used it for insulation in the roof and for insulation and extra rigidity in the nose of the trailer. I found it to work pretty good.

Yes, it does continue to expand for a while. You'll see pictures of this in my build journal. In trying to build panels as you described, you'll need to put in a couple "emergency escape" holes for the pressure to bleed off.

Other than the expansion issue, I think it would be a great way to build.

A couple notes on its use that have been mentioned, but I thought I would expand upon:
1) If you get any on your clothes, the clothes are done. It will NOT come out. Period. Wear lousy work clothes that you don't care about.
2) If you get it on other things that are porous, you'll have a heckuva time getting it off. Best to wait until it dries and hope that it didn't attach itself too hard.
3) Once you start a can, use it to the end. If the stuff hardens in the little delivery tube, that tube is done. You won't have a good way to use the rest of the can.
4) Buy a can or two more than you think you'll need. If you take a look at the Cost Log on my build journal, you'll see several places where I had to buy the Stuff. Although it expands, it will probably take more than you think.
5) Before you put in the foam, remember to think about whether you may need to run wires or anything else through that area. Once the foam is in, you won't run wires. If there's even a chance you might need to wire through the area, either put in a piece of pvc pipe or conduit to run the wires through after you've "foamed" it, or just put in some wires with the ends exposed just in case you need them later.

[NathanL]

If you just have to use an expanding foam forget the cans. They sell 2 part mix expanding foam that has a formula right on the can that tells you exactly how much you will get out of it instead of the guess work of the spray cans which get real expensive in a hurry if you need much of it.

I personally don't see the appeal but that's how I would do it if I had to, cheaper and less chance of an out of control expansion.

[SpottyDog]

My thoughts were that the expanding foam would be able to fill all the crevises and voids and at the same time act like a glue to stiffen everything up. I think I will put together some test sections to see what happens. I will keep you posted.

[Artificer]

I've done it, and it can work. I used two part expanding foam that you mix by hand then pour into the cavity. Great Stuff will not work, since it will blow out the sides. What you want is the slower expanding foam, which allows it to fill the cavity without overfilling it. Urethane foam in the cans also doesn't do a good job in thick sections. The board foot cost is way up there as well.

It makes no sense to use expanding foam for the walls. Get some urethane glue and extruded urethane foam. (pink or blue stuff) Glue your stringers/framing onto the wall skin. Then cut rigid foam pieces to fit into the cavities. If you leave space on the edges you can fill that in with Great Stuff later for air tightness. Pour a bunch of urethane glue onto the foam, and use a trowel to get an even coating. Put the foam in the cavity and weigh it down. Let it cure. If you left the foam pieces smaller, or you have gaps between the foam and stringers, backfill with great stuff. If you want more strength, get Foamular 250, or foam for placing under concrete.

Once one side is done and cured, coat the other side and stringers, and apply the second skin. This is a very strong and lightweight construction method.

Some notes: urethane foam (Great Stuff) and urethane glue cures with moisture, not oxygen. You don't have to add moisture to the wood. If you do, you get extra foaming.

For the person who had expanding foam applied to the windows... It says on the cans that it shouldn't be used in that location. Use either latex foam, or the stuff made for windows and doors. As long as the window isn't cracked/damaged, you can kerf the foam, and restore function.

Two part foam can be used in the curved sections of the roof. Its expensive, nasty to use, and not that easy. It can work. Its easier to hot wire the curve into expanded foam, and use urethane glue to stick it to the inner plywood. After its glued in, apply glue to the exterior and apply the outer skin of plywood.

Zip lock bags make mixing two part foam much easier. Make two compartments with the bottom folds, and weigh out the two parts, one to each side. squeeze most of the air out, and kneed for 30 seconds to mix. Cut a corner of the bottom off, and squeeze the mixture into the cavity like piping frosting.

Michael
(haven't been on the forum for awhile, but I'm starting another teardrop)