Construction Question

Canvas covered foamies (Thrifty Alternatives...)

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Construction Question

Postby ae6black » Tue Jul 11, 2017 9:04 pm

I'll be honest, I've never built a foamy. But I do like the idea. Would you foamy experts please tell me if this would be practical. Would it be possible to build a sandwich with 1/8 plywood on either side of a piece of foam board to use for the walls and side profile? Cutting windows and doors and the side profile in such a glued up sandwich would be a piece of cake. A router template would make cutting out the spar fittings for the roof practically a no brainer. Wouldn't the walls be strong enough to hold/mount conventional spars made out of 1X1 Pine and then simply cover with roof with 1/8 plywood with pieced foam board for insulation, working from the inside out? The wiring could all be run through the roof construction part of the tear drop and be located in the galley area without any channels needing to be cut in the sidewalls. I mean glued sandwich sideboards ought to be really strong enough for anything mother nature could throw at it. Such a unit could be covered with poor man's fiber glass or even aluminum. When I built my TD I built heavy because I take the thing off and use the trailer for other things at least once a year. I actually built in a fiberglass base sled to make siding my TD off easier. I built like a tank and problem is my unit tows like a tank. After reading about the virtues of foam I have to wonder if perhaps I couldn't have gone another route. The foam would be cheaper than the 3/4 plywood that I used for walls and I wouldn't run into that pesky frost action that I get during really cold temperatures which is when I primarily use my current TD, where I've only got wood making up my sidewall. (the way I built my walls, there are places where only wood on top of wood makes up the wall. The insulation is patched in next to it which is really not a great thing in really cold temps below 0 F). I would think between the 1/8 plywood inner lining wall along with the foam board would support both roof and anything I would ever be carrying in my galley shelves. For those of you that have built with foam what are your thoughts? It could be that I am overestimating the strength of a composite foam sidewall.

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Re: Construction Question

Postby linuxmanxxx » Tue Jul 11, 2017 10:11 pm

No your not at all. Use 1x2 turned up for roof spars double foam or it will sag. You glue and screw it all you can walk on it after it's finished.

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Re: Construction Question

Postby KCStudly » Fri Jul 21, 2017 8:16 am

The next thing you need to consider is how and where you will be fastening "stuff". 1/8 ply and foam does not have very good screw holding capacity. Everything from cabinets and shelves, to coat hooks, and every other thing, should be considered (maybe someday you will want to add a cup holder or other doodad). Some have used those screw in drywall anchors, or you could drill and glue in a dowel to screw into (though screwing into the end grain of a dowel is less than ideal).

When I started my build I thought it would be a great weight savings to plan out everything and sink small pieces of 1x blocking into the foam before skinning. I suppose I have saved some weight in that area, and it seemed like a simple method to start, but in the end boy did it take a lot of planning and effort. After about the 100th and fifty time routing out several pockets, hand cutting the corner radii square, gluing several blocks in, stacking weights on, removing weights, sanding and fairing it started to feel very time consuming and tedious.

On running electrical, you could avoid running wires in the walls if you don't want light switches, porch lights, reading/pillow lights, and/or running/clearance lights in or on the walls, otherwise it is best to plan well ahead.
Last edited by KCStudly on Tue Jul 25, 2017 5:57 am, edited 1 time in total.
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Re: Construction Question

Postby GPW » Sun Jul 23, 2017 5:20 am

QUOTE: “ I built like a tank and problem is my unit tows like a tank. “ … We had a couple of those before … No Fun !!!

"It could be that I am overestimating the strength of a composite foam sidewall.” … or Underestimating the strength of Foam …

Art, since there are No Rules here ( only a shed load of suggestions ) Please feel free to build anything , any way you want to … Build what You need !!! Only you know what you require as far as strength , appearance and load carrying ability … ( Like a Yak Rack on the top ) And the best way of controlling the weight is to weigh everything before you install it on the trailer … ;) And remember some woods are lighter than others and that can make a difference too … When controlling weight , remember 10 little things add up to a Big thing ….weight adds up more quickly than we like ...
There’s no place like Foam !
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Re: Construction Question

Postby dancam » Sun Jul 23, 2017 12:50 pm

KCStudly wrote:The next thing you need to consider is how and where you will be fastening "stuff". 1/8 ply and foam does not have very good screw holding capacity. Everything from cabinets and shelves, to coat hooks, and everything other thing, should be considered (maybe someday you will want to add a cup holder or other doodad). Some have used those screw in drywall anchors, or you could drill and glue in a dowel to screw into (though screwing into the end grain of a dowel is less than ideal).

.


I just planned where all my stuff would attach beforehand and put 1/4in thick strips of wood into the foam before canvassing over. Works quite well. Easy if you have a plan beforehand

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Re: Construction Question

Postby dancam » Sun Jul 23, 2017 12:52 pm

Art- how thick of foamboard, what outer dimensions and do you intend to put anything on the roof?
You can build it so it will work well. I think this is a good idea.

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Re: Construction Question

Postby dancam » Thu Sep 28, 2017 6:56 pm

what to you guys use to glue foam to wood on large surfaces like this? I'm just going to glue my 1/8th Baltic birch door skins onto the 1 1/4in foam and suddenly wondered if it would dry well enough using tb2. I used gorilla glue or pl premium on all my other wood to foam joints but this is a larger flat panel and I don't want the glue to be pushing it around as it expands. So does tb2 work fine? Tried searching for a bit and was surprised I didn't come up with an answer right away. But my searching skills are likely poor.
Thanks for any help.
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Re: Construction Question

Postby KCStudly » Fri Sep 29, 2017 11:08 am

I had success with TB2 on large panels (wood to foam) provided that the foam is clean and level (i.e. fair at all butts and wooden inserts); and by making sure to roll the glue on in a thin layer with a relatively dry roller... no big beads of roller tracks or droplets. Do not brush or squeegee it on. The trick is to only leave enough glue that the wood can absorb before it seals itself off, otherwise it does not cure.

Basically spread it on and roll as much back off as you can. For me this actually worked better than 3M 30NF.
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Re: Construction Question

Postby dancam » Sat Sep 30, 2017 9:54 pm

KCStudly wrote:I had success with TB2 on large panels (wood to foam) provided that the foam is clean and level (i.e. fair at all butts and wooden inserts); and by making sure to roll the glue on in a thin layer with a relatively dry roller... no big beads of roller tracks or droplets. Do not brush or squeegee it on. The trick is to only leave enough glue that the wood can absorb before it seals itself off, otherwise it does not cure.

Basically spread it on and roll as much back off as you can. For me this actually worked better than 3M 30NF.


Thanks! I had gone ahead and used tb2 on one door. I did roll it on but i wasnt overly careful about not having ridges or thicker parts :/ hopefully it worked. Havent inspected it too close yet.
If that door looks flat still i will do the second door following your advice, thanks again!



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