Share your thoughts with me on wood/fiberglass vs. foam laminate construction

TheAlmightySam

Adventurer
Hey all. This is going to be rambling and only semi-sensical, so I apologize in advance.

So I'm contemplating building a shell for my W250, since I can't find what I want on the used market for a reasonable price. Somehow being extremely picky and extremely cheap hasn't worked out in my favor... go figure :sombrero:

So, I'm gonna build one, I guess. I've been researching on here trying to figure out how I wanna do this thing. The two building methods I'm kicking around right now are a foam sandwich build a la the POD, and a wood build along the lines of the Sawtooth XL. I've ruled out a metal frame on three counts: cost (have you priced steel lately?), skill (I am a crap welder fo' sho'), and thermal characteristics (a steel frame is a horrid insulator, no matter how much bloody insulation you pump into it).

Here's my goals:

1. Cheap
2. Cheap
3. Water-tight and warm. If you're not familiar with the northwest corner of the country, it's wet and cold here.
4. Strong as hell and resistant to vibration. A W250 rides like a military truck - it's rough, and just about anything will shake itself to death on the back of one.

I do not care (much) about weight. My truck already clocks in at nearly 8000 lbs - what's another few hundred? I could use more weight over the back axle anyway :bike_rider:

In my head, I envision a wall structure like this:


...where the sidewalls are a sort of honeycomb filled with insulation, like so:


You may recognize the idea being that I straight up jacked it off the Sawtooth XL. Great artists steal, or something. The only modification I plan to the Sawtooth structure is to laminate the wood front and back with a couple plys or so of fiberglass cloth, making a (hopefully) waterproof structure, with the exterior aluminum skin existing only for cosmetics. For the record, no, I will not be sanding and painting the fiberglass if I can avoid it. I hate bodywork.

So, the other option, one I'm not nearly as familiar with, is a foam laminate construction, like the POD. There's something really neat about how space age that all seems, and surely 60psi foam has a much higher R-value than plywood, but I know very little about how it handles extended vibration and rough roads, nor do I know anything about how the cost compares to wood construction. Any thoughts on these subjects?

Just in case you're interested, here's some sketches of what I intend this thing to look like, basically an old-fashioned camper, only with non-crappy construction.



I know it seems odd to build something I can probably find on Craigslist, but it's nigh impossible finding exactly what I want that's not all rotted out or way overpriced. All the old wood shells are junk (don't ask me how I know), and the Callen shells are steel frame (which I'm hesitant about) and everyone seems to think they're gold (I am NOT paying $800 for some old camper shell). Plus, what can I say, I like to build stuff, and I've got a bunch of old camper windows in my junk pile :D

Thanks in advance for any thoughts you have!
 

nosnerd

wanna be tourist
I Feel for ya buddy...

i much rather sink coin into my 800hp nova street machine slash race car.....plus my truck is in great mechanical condition...so..i am going to build my own...angle iron and square tube..VCB urethane glued 3/8 plywood sides...and 1/2 roof painted over with a roll on bedliner kit...

the sides will be skinned over with 30 thou alum...rear door offset to passenger side..

a place to properly organize my shtuff....and crash an occasional night...twin group 27 marine batts on frame (with 3000w inverter) fed by a 140 amp alternator...twin group 34s under hood OE style..

need to purchase a BEDRUG......but am still digesting the price....lol


alan
 

stomperxj

Explorer
Here's a great writeup on fiberglass over foam:

http://www.goldbrand.info/motorcykelhusvagn2.html

On my next trailer I am going to be combining a few different methods I think. Thin ply, lots of foam and lots of fiberglass and epoxy. Should be a good compromise between light weight and strength. I too am watching the POD build and seeing how that works out for pods8. Lots of good info there too...

Just FYI, the insulation I put in the side panels of the Sawtooth didn't do much at only 1/2" thick and 2" spacing between the pieces. It looked cool in CAD but thats about it I think. The stuff in the roof was a full 3/4" thick and you can see on a cold morning that its doing its job.

Also I don't think you need marine grade ply. Lots of chemicals in that stuff anyway. If you encapsulate the whole thing with fiberglass you shouldn't have any worries about rot. Just get a good cabinet grade ply like Baltic birch or similar....

Looking forward to your build. Good luck ;)

Jess
 

Dale

Adventurer
You may want to take a look into Nyloboard.com. They make 4'x8' sheets (or custom) made from recycled carpeting and laminated in fiberglass in 3/8, 1/2, 3/4, and 1". Can be painted with Sherwin Williams (written guarentee) or Gel coated. No offgassing of VOC or Formeldehyde. I am a green building contractor and plan on building my next cap to use for work and weekend get aways. I can't find anything on the market that fits my needs. I like the fact that I can use my tools to make and do not have to sub out a welder (except for roofrack). I am going to sandwich 2" rigid foam in between 1/2" sheeting. I have the 7.3L F250 so weight isn't a concern for me either and I like having the extra weight on the rear wheels. Here are a few photos of the basic idea, mt set up will be a little different.


but with a hatchback instead of barndoors
 
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Dale

Adventurer
Also, it will be just like a regular truck cap and not a slide in shell. I plan on bolting it to the bed and using compression springs on the bolts to allow for twisting.
Something like this
 
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pods8

Explorer
For something basic like you're doing you may want to consider a minimalist wood "frame" (mainly to define the shape) then have XPS foam between and rather than sheet in plywood and then glass over it perhaps just use some of the prefabbed FRP sheeting. Places like homedepot usually sell 4'x8' sheets of it, unfortunately it usually has a pebble surface but the companies do make a smooth version as well so if your store doesn't carry it perhaps they'd order it. I'd use an epoxy slurry of something like wood flour & cabosil with a shallow V-notch trowel to skim the stuff over your structure and glue down the FRP sheets (you'll need to weight them in place). Round off the corners and do a little hand laid fiberglass work there to joint the two faces together and seal things up. Since the panels are prefabbed the amount of finish work on the exterior you'd have to do for a smooth surface would be very minimal verse hand lying fiberglass cloth. Mainly fair in the hand laid work, scuff the rest so primer/paint will adhere and spray/roll it, I'd suggest making sure you have a UV adsorbing/blocking paint. Overall it would probably be substantially faster...

I disregarded doing it that way because the strength/weight ratio on those prefab panels (made of polyester resin and glass strands) isn't what I desired (at the time anyways, as my build drags out I question myself :) ).
 

scrinch

New member
stomperxj said:
Also I don't think you need marine grade ply. Lots of chemicals in that stuff anyway. If you encapsulate the whole thing with fiberglass you shouldn't have any worries about rot. Just get a good cabinet grade ply like Baltic birch or similar....
You need to get exterior grade plywood at a minimum. Epoxy seals pretty well against liquid water, but water vapor can pass through it. And with fatigue, epoxy/fiberglass can develop hairline cracks that can let water through. You don't want to risk plywood delamination due to a little moisture getting in. The difference between exterior grade plywood and marine grade plywood is the quality of the plies...uniformity of thickness, voids, patches, etc. They both use the same waterproof glues (if that's what you mean by chemicals). There are no other chemical treatments in marine plywood.
 

followmydrift

New member
in regards to this construction, which glue/adhesive would you use to build the wood frame?, attach the wood frame to the interior plywood skin?, adhere the XPS to the plywood skin?, and finally, adhere the FRP outer skin to the XPS/wood framing?
i'm trying to minimize the number of different glues/adhesives i will need to use.
 

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