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Came across a build video this morning of a build technique I hadn’t seen. I’d seen similar ideas in scratch-built model RC airplane construction of ‘foamies’, but wouldn’t have considered it for a van build.

The idea is to glue cheap semirigid eps and xps foam together and laminate screening, paper and other materials over it to strengthen it. There’s a bit of a community of people doing it. They don’t seem big on more conventional epoxy resin or fiberglass coating, I guess because of the mess and fumes factor. It’s light, doesn’t require many tools and looks very forgiving, but time-consuming and of questionable strength and finish quality.


Not sure I’d use it for production, but it might be good for prototyping or temporary builds.
 

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The only advantage I can see is the weight savings. My 1500 PM HT van can carry 3,000+ pounds. For my time and money 1/2 inch hardwood plywood at double the price of 1” foam is such a superior product, so much stronger, easy to glue up, finish, and can hold screws for doors, hinges, and drawer glides. I think it's great to innovate but the end product must be better not worse or what’s the point? Now don’t get me wrong weight savings can be so important if it trumps the other issues. I have built strip cedar canoes and cedar’s lightness gives you an 18 foot canoe at something like 55 lbs. instead of the normal 70+ lbs. Portage that up in the North Maine Woods across Mud Pond Carry someday and you are going to wish it was made of foam in order to save another 3 or 4 lbs. In my van ...... not a design factor. Thanks for sharing.
 

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total brain synapse from my past... There were many planes at an Experimental Aircraft fly in that were made from Kraft paper and fiberglass : ) for any who really want to think beyond standard wood products and save some weight (but not time or money!)

The Rutan VariEze comes to mind (and similar DIY/Kits)

Thom
 

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...There’s a bit of a community of people doing it. They don’t seem big on more conventional epoxy resin or fiberglass coating, I guess because of the mess and fumes factor...
Or, possibly cost. Fiberglass is relatively expensive. Never tried resin on foam either. Might melt it.

This seems like a ghetto version of EIFS which is applied to the outside of buildings. EIFS screen is much stronger, but very expensive and they don't like to sell it to people who aren't certified to do EIFS.

Kind of clever actually. I could see doing this for overhead cabinets where weight is less desirable and the shape flexibility is a plus. You could laminate in wood blocks to hold screws for doors and other attachments. I like the brush-on bedliner idea too. This could seal the inside of overhead cabinets and create non-skid surface.

I checked out the HWFF site and they have some good stuff at reasonable prices. I could see building curved surfaces using layers of thin foam bonded with their Foam Fusion product. I've thought about that before but wasn't sure what glue to use. Foam-board adhesives like PL-300 are expensive and don't spread thin enough to laminate. Air-dry carpenter glue doesn't work well either. Foam fusion is $70/gallon - not that bad and will probably go farther. Will be ordering an 8oz to try it.

Didn't care for the his "precision" with the hot knife but it got me to thinking about using my router and dovetail jigs on foam. Will give that a try some day.
 

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Discussion Starter #5
I like the brush-on bedliner idea too. This could seal the inside of overhead cabinets and create non-skid surface.
Yeah, I had been thinking about using bedliner on other surfaces too. Also looking at garage floor epoxy kits for finishing and countertops too. The problem with most of these is they don't store well, so you'd have to use them all at once. The epoxy stuff self-levels and you can achieve a high gloss with it.
I've thought about that before but wasn't sure what glue to use. Foam-board adhesives like PL-300 are expensive and don't spread thin enough to laminate. Air-dry carpenter glue doesn't work well either.
RC hobbyists use what they call foam-safe cyanoacrylates, I'm not sure if that's the same stuff.
Didn't care for the his "precision" with the hot knife but it got me to thinking about using my router and dovetail jigs on foam. Will give that a try some day.
Yeah, I immediately thought of dovetailing when he started doing finger joints. Not sure what a router would do to foam, might melt it. Wonder if you could cut foam with a laser cutter or rig up some kind of hot-knife 3D printer.

Let us know how the adhesive works out. I'm also thinking these techniques might work for overheads, built-in shelves and maybe drawers and such. I have a HF hotknife and some foam leftover from insulating my garage doors. His hotknife looks very 'precise' compared to it. Everythings relative I suppose. The glue may hide a multitude of sins too.
 

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..Not sure what a router would do to foam, might melt it. ...
Foam routs very nicely (with carbide anyway, which is all I buy). And, as a plus, the bit will last virtually forever. Biggest issue is the dust which sticks to everything.

If you haven't tried it, cutting foam on a table saw can be very dangerous. It likes to catch and pull the work away from the fence very quickly. Much safer to set up a guide for a router or hot knife.
 

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I came across this video yesterday myself. I remember thinking it was interesting but overengineered and a lot of work for not enough gain. I'm with RD on this matter, he said it best.

If our vans were human powered like the Flintstone, sure, the weight issue could be important. But we've got 283HP on tap.

Also, I'm not sure how strong it would be. Yeah, I saw him sit on his cabinet. But I'm thinking it's strong like an eggshell. Plenty good enough for its intended purpose, but vulnerable to catastrophic failure if subjected to any forces that it wasn't designed for. Think "egg against the lip of a skillet".
 

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This is also very similar to Structural Insulated Panels (SIPS) used in home construction. Very strong and probably overall stronger than wood by itself. Your also adding insulation where you place one of these units against a van wall.

I'd probably actually make a SIP, using thinner materials than home construction and then cut the pattern out of the completed SIP. You then have wood screwing surfaces and could even use solid wood through pieces instead of foam at attachment points. The disadvantage that I see to this method is that you will generally have thicker walls that consume space.

Homemade SIPS would probably be an effective way to insulate your van without spraying or gluing foam to your vehicle walls.
 

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Came across a build video this morning of a build technique I hadn’t seen. I’d seen similar ideas in scratch-built model RC airplane construction of ‘foamies’, but wouldn’t have considered it for a van build.

The idea is to glue cheap semirigid eps and xps foam together and laminate screening, paper and other materials over it to strengthen it. There’s a bit of a community of people doing it. They don’t seem big on more conventional epoxy resin or fiberglass coating, I guess because of the mess and fumes factor. It’s light, doesn’t require many tools and looks very forgiving, but time-consuming and of questionable strength and finish quality.

https://www.youtube.com/watch?v=IJv0pEjvC34

Not sure I’d use it for production, but it might be good for prototyping or temporary builds.


Speaking as an old VW Bus owner...... The weight savings on this foam built cabinet could be worth another 1 to 2 mph getting a bus up a hill!
 

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My sister made the bed in her E350 with laminated foam and says she hasn't had any issues with it.

Main advantage, other than weight, seems to be for those who don't have the tools or skill to work with wood.
 

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https://en.wikipedia.org/wiki/Structural_insulated_panel

These engineered panels are used to build strong homes that go up quickly and provide insulation with virtually no thermal break. They are often used to enclose timberframe homes, which is how I was introduced.

Commercial walk-in freezers use a similar concept, but the foam walls are laminated to stainless steel instead of wood.
 

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Early in my build, I made a table of 1" polyiso sandwiched between 1/8" Luan. It worked well--very flat, light and strong, but ultimately too thick for my purpose.
 

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Discussion Starter #15 (Edited)
Early in my build, I made a table of 1" polyiso sandwiched between 1/8" Luan.
I was wondering if the same techniques would work for polyiso. My current ceiling plan is the 1” polyiso covered with headliner treatment RD pioneered, but I’m a bit worried about crushing or denting the polyiso with cargo or my fat head ;).

Not sure if it’s just because I’m more familiar with it, but polyiso seems to have more tensile strength than eps or xps. Around here 1” polyiso seems impossible to come by, but 3/4” and 1/2” are readily available.
 
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