Spray foam vs sheets

[raveen]

Spray foam are popular option for all you, and this is full of covers. Spray foam are have benefits and and disadvantages.

 

[rruff]

Spray foam will fill every crevice and bond to whatever it is prayed on adding structural strength. Cutting rigid foam will leave gaps.
Cover the foam with thin plywood.

Thanks to you and tommyt for the replies.

I understand these advantages, especially the elimination of gaps. For the OPs application the spray foam makes sense. Of course I was wondering about my own project which is substantially different. I'm planning to use sheets and wood stringers in a structural sandwich. If I used spray foam then both skins need to be intact when the foam is sprayed, and this is not easy from my understanding. I was curious if sheets of polystyrene are inherently inferior in other ways. At lower temperatures I've read that polyurethane foam has poor insulation value compared to polystyrene, even though it is better at room temperature.

 

[raveen]

Yes, this is major advantage of eliminate of gaps. and Spray foam are cover all over corners. But sheets has no these advantage.

 

[Joe917]

Instead of trying to make a structural sandwich you would be better to just buy the panels pre-made cut to size.

 

[rruff]

Instead of trying to make a structural sandwich you would be better to just buy the panels pre-made cut to size.

Where? And how much $$$?

 

[java]

Where? And how much $$$?

There is a company out of BC that will have then cut and packages as a diy kit. Not cheap though. I can find the link tomorrow

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[Joe917]

http://totalcomposites.com/ (no affiliation, no experience with company or product)
There are many others, google is you friend.

 

[rruff]

http://totalcomposites.com/ (no affiliation, no experience with company or product)
There are many others, google is you friend.

Thanks. They say kits start at $9900 but no indication of what that includes. Probably a very minimal small box.

Looks like there are using blue Dow Highload XPS foam. He has a thread here so I'll ask over there. http://www.expeditionportal.com/for...North-America/page8?highlight=totalcomposites

 

[java]

I got a quote for a 13' with a cabover. 18k plus engineering for a subframe

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[Joe917]

Unfortunately you have to decide what you are building.
If you are trying to build a top quality solid comfortable cabin you will have to spend on the box. After you add up the cost of solar, wiring, inverters, cabinetry, plumbing, heating and on and on, not to mention labour, I see no point in building it in a stick frame box full of frost bridging and structurally poor compared to composite panels.
Truck refrigerator box manufacturers is also a place to look.

 

[java]

I do agree, that's why I was looking into them. But at the same time I prefer an aluminum skin, it's all trade offs.

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[rruff]

If you are trying to build a top quality solid comfortable cabin you will have to spend on the box. After you add up the cost of solar, wiring, inverters, cabinetry, plumbing, heating and on and on, not to mention labour, I see no point in building it in a stick frame box full of frost bridging and structurally poor compared to composite panels.

For a deluxe rig it makes sense for sure, especially if you are going to have $100k+ invested at the end. But there are other ways to do it.

I'm planning to build my own bonded sandwich panels. It isn't really a stick frame box, and frost bridging is no worse than in most houses. Starting at the inner wall 1)3mm marine ply (6mm on the floor) 2) light XPS (1" walls, 2" ceiling and floor) and redwood stingers 3)3mm marine ply (6mm on the floor) 4)fiberglass cloth and vinylester resin 5) gelcoat

I built one similarly about 16 years ago, only with luan ply, pine, and polyester resin. The cost was ~$2500 for all the materials, including the inside, doors, windows, sink, cabinets, solar, batteries, etc. I'm figuring >$5k total this time, but I don't think I'm in the market for a $18k shell.

 

[DzlToy]

foam is inherently flammable..

Having used a can of spray foam to fill some gaps around the shop doors, I was cuirous. So, I sprayed some out onto the concrete and let it dry good.

A few hours later, I tried to light it with a cigarette lighter and it did not do a thing. Hitting it with a MAPP gas torch simply resulted in melted foam and an acrid odor. There is no ignition or combustion of the foam itself, due to the presumed use in residential and household applications to seal windows and such.

Find someone who is a professional to spray your camper box. The DIY kits that I have seen, leave much to be desired. You may wish to trade labour or otherwise exchange services instead of using $$, if the retail price is too steep.

 

[Healeyjet]

Java, I believe the foam being flammable discussion is more surrounded around the installation. Heat is a byproduct of the curing process of the foam. What has happened, on more than one occasion, an inexperienced installer has filled a cavity with foam too full and too rapidly. What happens so I am told is that the foam trapped deepest inside generates too much heat and combusts. I believe once it is cured the combustibility is a non issue. It would be a non issue combusting during installation in a camper as the application is so thin. I was told while having a basement project foamed that someone in town filled a cavity under a bow window or similar and the heat caused it to burn the project to the ground.
Others may have more or better experience though.
Ward

 

[java]

Interesting, I didn't think about the heat from the reaction.

I am pretty sold on it. I will be doing 1 3/4" in the walls and 3 1/2" in the ceiling.