rruff
Explorer
The one I'm talking about was done 22 years ago. It's long gone. The one I'm working on now is all hand laid fiberglass and carbon fiber with foam core, no wood. Not comparable to what you are doing, and I don't have a build thread.
Plywood camper fabrication questions (thinking of idaSho)
- Thread starter ReluctantTraveler
- Start date
ReluctantTraveler
Well-known member
Yes. I edited my post above.
@IdaSHO 's frame is quite strong, but building the frame up from layered plywood could be even stronger than what he created. Going with a larger 2" frame (I think he used 1.5") would be even stronger, which might be what you are seeking for your rig.
Whether all the extra work is something you want to do, and whether it is truly needed for your camper?
Please do think about it, as it will likely help you with your thoughts on how to make a light and strong camper frame.
That all makes sense. My main reason for leaning towards 1.5" foam core was that 2x4s and 2x2s have an actual width or 1.5", so it would make the fabrication a lot easier.
I could, of course, get 2x4s and cut them down to 2" instead. I'm trying to be realistic about both costs and my fabrication skills.
ReluctantTraveler
Well-known member
Another reason I was leaning towards NOT the Owen's Corning stuff, if I can avoid it.
I came up with the idea of layered 3/4" plywood to become (about) 2" to allow me to use 2" foam.
Baltic Birch plywood made with exterior glue was available and much cheaper than it is today (if one can even still get it) when I came up with the idea.
I suspect that you could build a jig to help you cleanly cut 8' long 2" wide strips of 3/4" plywood.
You might be able to have it CNC cut locally. I suggest you also check local hardwood suppliers for what they have. In particular, check on 1.5"x1.5" and 2"x2" ash.
Keep in mind that the layered 3/4" plywood frame (about 2") allows for some adhesive on each side of the 2" rigid foam insulation when the skins are applied. Make sure that your frame allows you to glue your skins in place without "bulging".
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IdaSHO
IDACAMPER
Probably close enough but...
6mm (1/4) exterior skin, which includes walls and roof
3mm (1/8) interior skin, again, walls and roof
6mm (1/4) interior floor, both cabover and main floor
13mm (1/2) belly
All of which is a 1-1/2" core, using standard 25PSI XPS ridged foam
All that said and done, Ill say this....
If I were to do it again, I would either shed a considerably amount of framing or drop to 3mm (1/8") exterior skin.
The thing is stupid strong the way its built, so shedding a bit of weight by loosing some material might be worthwhile.
IdaSHO
IDACAMPER
As another poster mentioned, fasteners were more of less used as a method to hold things together while the glue dried.
The PL premium I used for the builk of construction requires joints to be "clamped" until cure.
So a combination of screws and nails were used for the required clamping load.
The frame was assembled using pocket hole screws in order to pull the joints together and hold things while the PL cured.
This allowed me to glue, screw, and keep moving. Had it been just glued and nailed, I would have had to wait for each section to cure overnight before moving on.
The screws provide the strength to allow work to continue. Though their holding strength is likely a fraction of the holding strength of the PL premium itself.
The skins were attached in a similar fashion, but instead of using large fasteners like screws, the panels were wet set and fastened with PL premium.
There were a couple of trouble spots that required screws to pull things into shape, but the nearly 2500 18GA brads did the rest.
IdaSHO
IDACAMPER
My build utilized DOW brand XPS foam
Every sheet cut/fit and glued snuggly into the framing cavities.
A bit of scraps and a bunch of paint stir sticks helped a bit
IdaSHO
IDACAMPER
With regards to plywood framing, I considered it but its screw/nail holding capability on end grain is terrible.
And unless you are paying good money for boil proof, void free ply, IMO you are asking for trouble.
The issues with voids and delamination in todays plywood is terrible. Ive been finding voids in baltiv birch lately.
Well, almost lately... I snagged a unit of both 1/2" and 3/4" 5x5 months ago in hopes of weathering the Russia debacle.
Framing I used is "1x2" 3/4"x1-1/2" vertical grain Fir. Tough, stable, and lightweight.
And unless you are paying good money for boil proof, void free ply, IMO you are asking for trouble.
The issues with voids and delamination in todays plywood is terrible. Ive been finding voids in baltiv birch lately.
Well, almost lately... I snagged a unit of both 1/2" and 3/4" 5x5 months ago in hopes of weathering the Russia debacle.
Framing I used is "1x2" 3/4"x1-1/2" vertical grain Fir. Tough, stable, and lightweight.
rruff
Explorer
It seems to be pretty consistent per batch... not so good between batches. I think Carbon Core cuts all theirs, and it isn't exact either...
ReluctantTraveler
Well-known member
@IdaSHO @rruff Thank you both, this is great stuff!
Where I'm planning to build on an F-550/5500 platform, I'm a bit less concerned about weight and am OK going a bit heavier for stupid amounts of durability.
This was all really enlightening! Much appreciated!
It sounds like DOW might be a bit more reasonably priced, and from looking online, it looks like they've got some pretty high densities as well.
Where I'm planning to build on an F-550/5500 platform, I'm a bit less concerned about weight and am OK going a bit heavier for stupid amounts of durability.
This was all really enlightening! Much appreciated!
It sounds like DOW might be a bit more reasonably priced, and from looking online, it looks like they've got some pretty high densities as well.
ReluctantTraveler
Well-known member
If you use XPS, I'd recommend a wallpaper perforator to texture the surface. Really work the glue it, then add more and trowel it.
Is the PVC foam core XPS as well, or am I confused about terms?
rruff
Explorer
No, totally different. The reason for texturing like that is because the XPS is very tiny cells and weak, and glues don't stick to it well. So, increase the surface area and also give it more of a 3D surface. It should be rough sanded first as well. The PVC is much stronger and large cells so when it's cut it's already rough, and adhesives stick to it much better.
XPS is cheaper... that's the only good reason to use it.
PVC is polyvinyl chloride. XPS is extruded polystyrene.
ReluctantTraveler
Well-known member
Thanks! It looks like through the vendor you linked I could get all of the foam core I need for around $4k. Honestly, for the peace of mind having more structural support for what's an expensive home on wheels, that feels like money well spent.