ultra compact slide in / sleeper

IdaSHO

IDACAMPER
FYI, Im running 6mm Okoume for an exterior skin, 1.5" XPS for foam, and 3mm veneer for interior skin.
All constructed over a VG fir frame.

My entire shell weighed roughly 700# before finishing it out. And it is rugged as hell.
I've smacked it off of a few trees since the build, and all it does is scratch the paint.

Roughly 15' long, 7' wide, and 6.5' tall

chassis219.jpg
 

CoyoteThistle

Adventurer
Done! I happened to have some very old epoxy and some Bondo cloth (~5.5oz), so I laid that on the 2.7mm luan with 15psi XPS underneath. Bomber. I can't ram a screwdriver through that either.

Cool! The test piece I made seemed pretty tough but it's great to have a comparison to the other materials.

Loving this discussion guys! I went through a lot of these options in my head a year or so ago and I couldn't find much info from others - other than some nice builds with name brand panels ($$$) and a few folks who made their own panels (cost unknown).

One thing to consider in making your own plywood faced panels rruff (you probably have factored this but I'll just make a point for the general discussion) is the cost of the adhesive. The amount of epoxy (maybe there's something cheaper?) it takes for each panel can add a fair bit of cost to the equation.

I did some experiments making my own panels with cheap insulation foam and fiberglass. Long story short, it took a lot of glass to make a strong panel (I had stringers on 2-foot spacing IIRC). And the result wasn't all that light. And fairing would have been a big task.

I'd be curious to see how strong/light a home-built ply-cheap foam-ply panel would be...
 

IdaSHO

IDACAMPER
I'd be curious to see how strong/light a home-built ply-cheap foam-ply panel would be...

I'm strongly considering building a press to mfg custom panels for future builds.

It wouldn't be terribly hard. And would allow me to mfg panels with whatever skins and core I want, all bonded with a good marine epoxy.
 

rruff

Explorer
FYI, Im running 6mm Okoume for an exterior skin, 1.5" XPS for foam, and 3mm veneer for interior skin.
All constructed over a VG fir frame.

My entire shell weighed roughly 700# before finishing it out.

As I recall, you also had some steel framework. Did you actually weigh it or is the weight estimated? The dimensions on our campers are similar. A 6mm Meranti outer skin only would add ~200lb to my build. But I think I'll be ahead on durability by using a fiberglass outer skin with 3mm Okoume, and the fiberglass weighs ~40 lb.
 

IdaSHO

IDACAMPER
As I recall, you also had some steel framework. Did you actually weigh it or is the weight estimated? The dimensions on our campers are similar. A 6mm Meranti outer skin only would add ~200lb to my build. But I think I'll be ahead on durability by using a fiberglass outer skin with 3mm Okoume, and the fiberglass weighs ~40 lb.

I did not weigh the empty shell. When being built, I actually finished out much of the interior before dropping the roof on it, so empty shell weights are estimated by my weight charts.

Although total dry weight came in spot on at my 2200lb target weight, so Im confident in my estimates for just the shell.

Since then I've added a few things, like solar, and a few small cabinet alterations. Currently it runs about 3k wet and loaded.



Yep, the unit does have a steel subframe. Primarily for camper jack mounting.

Knowing what I know now, I could have done away with much of the steel, and would be able to get away with just steel framework in the corners.

I pretty much refuse to depend on bolts thru plywood to hold the jacks. As designed, the steel framework is a cradle for the camper, so none of the forces of the jacks are applied to the shell itself.

I've also got a 1/2" thick plywood belly on it for piece of mind when loading/unloading.


chassis17.jpg



Also, I should mention that I did not glass the entire shell. So I saved a decent amount of weight (and labor) there.
Only the joints were glassed.

For future builds (especially smaller campers) I intend to use 4mm ply and glass the entire thing.

Larger scale builds, Im still on the fence. Though Im leaning the way of keeping the 6mm ply and glassing the entire thing.
 

The Artisan

Adventurer
I'm strongly considering building a press to mfg custom panels for future builds.

It wouldn't be terribly hard. And would allow me to mfg panels with whatever skins and core I want, all bonded with a good marine epoxy.

Thats what i am doing in the next few months. Already have the 5hp blower from my cnc material cutting table so it will be easy to retro.
Kevin
 

rruff

Explorer
One thing to consider in making your own plywood faced panels rruff (you probably have factored this but I'll just make a point for the general discussion) is the cost of the adhesive. The amount of epoxy (maybe there's something cheaper?) it takes for each panel can add a fair bit of cost to the equation.

I did some experiments making my own panels with cheap insulation foam and fiberglass. Long story short, it took a lot of glass to make a strong panel (I had stringers on 2-foot spacing IIRC). And the result wasn't all that light. And fairing would have been a big task.

The adhesive I used to make some test panels is PL Premium. Buy the large tubes, rip them open, and use a notched trowel to spread the glue. PLP seems to work very well so far and it's much cheaper than epoxy (~$30-35/gal). One big advantage is that it works fine in cold temperatures, so you can use it all year in an unheated garage. You need to prep the foam first! That's true of any bonding to XPS foam. Nothing soaks into it, and it's weak so you need to really score the surface. I run over it lightly with rough sandpaper, wipe it off (air would probably be good too if I had a compressor) then texture the surface with a carpet seam roller. BTW, I tend to use more glue than I thought I would. It's ~.25 lb/sq ft for both sides.

How much fiberglass did you use on the test piece and how thick was the foam? I'm surprised that it wouldn't be stiff if you had at least 17oz faces, unless the skins were coming loose from the foam. The 48"x15" sample I made with 2.7mm luan skins and 1" core (no wood) is very stiff. I can support it on the ends and jump on it (180 lbs) and it's very solid.

Fairing, who needs that ;)? If you are doing fiberglass over foam, I'd consider doing a textured final layer like Monstaliner. Trying for a smooth shiny surface would be a lot of work, fairing and sanding.

Another comment regarding stringers. I have no idea how many (if any) are needed. The issue is we are using foam that is weak in shear, so isn't able to support large bending loads. It will certainly fail before the skins when stressed that way. I don't know what the stingers add to that, but at the least they will provide some support to the skins if the foam fails. 24" is the max spacing I'm comfortable with on walls, and on roof and the floor, it will be 12-16".

On the other hand if I paid the money for actual structural foam I'd be comfortable with just putting wood at the edges of the sheets, so 48" centers. But it's nice to have closer spacing for hard points to mount anyway... which leads me back to just using the cheap XPS.
 
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rruff

Explorer
I've also got a 1/2" thick plywood belly on it for piece of mind when loading/unloading..... For future builds (especially smaller campers) I intend to use 4mm ply and glass the entire thing.
Larger scale builds, Im still on the fence. Though Im leaning the way of keeping the 6mm ply and glassing the entire thing.

It's tough to get this stuff right. Baring a lot of experimenting and detailed structural analysis, we are just guessing. Hopefully semi educated guesses though!

16 years ago when a built a similar camper (under time duress and no internet and minimal budget in someone elses garage) I worried about a lot of things and just hoped for the best. I initially was going to paint it but decided to fiberglass at the last minute. My previous camper built with similar constraints was painted with the wrong paint (and had a sunroof! bad idea) and ended up rotting. I figured better paint and design would fix that, but fiberglass would be an even better choice. I'd never glassed anything in my life, but it wasn't hard, even with polyester resin and widely varying temperature. On some parts around door and window frames I merely painted the resin over the wood and it held up great. Trying for a smooth surface with fiberglass is a lot of annoying (itchy) work, but if you leave it textured, it isn't bad at all. No sanding or cutting of glass, except a little on the edges when the tape is applied after assembly. I built the panels and glassed them first, so I could work horizontally, then did the edges after joining. The front piece was curved so I had to do vertical there, but it wasn't that hard. I used thin 2.7mm luan skins for walls and top, but they were better quality than they are now. Anyway, the fiberglass over luan was super tough. The fairly thin but rock hard skin seemed to add a lot to the durability.

The foam I used in the panels was crap. Really cheap and weak EPS. I'm guessing XPS wasn't around or I didn't know about it. Based on my prior experience of similar EPS coming debonded from the face sheets fairly quickly, I used a lot more stringers in this build, 12-16" centers.

One thing I worried about quite a lot was the floor. Like now, I mounted the camper directly to the truck frame, only on my '84 Toyota there were only 4 points. I found some steel "hat" pieces used to clamp 2x4s that were very heavy duty (I'd guess 3/16 thick) and screwed and glued those to the floor, and mounted them with bolts to frame. No cushioning, no bushings, hard mounted. That floor was 1.5" core and 5mm luan faces, with mostly 2x2 stringers, with 2x4 under the mounts.

The end result was that I put ~45k miles in 3 years on that camper before I had to give it up. Lots of bounding over washboard and rocks, bashing through trees branches, and sitting out in the weather 24/7. No leaks and no problems whatsoever. The mounts held and the lack of isolation from the frame didn't seem to hurt the camper. No evidence of the foam failing or debonding, but the stringer spacing was tight enough that I'm not sure I would have been able to tell.

One thing that concerns me now is that I have more time to plan and build, internet access, more money, and my own garage!... but I'll still screw something up that is hard to fix. There is a fair amount of luck involved I think.
 

IdaSHO

IDACAMPER
I use a lot of PL premium on by builds and love the stuff, but for building panels, there is no way Id consider anything but epoxy.

In order to get a panel bonded 100% flat to a core, you need the adhesive to flow well. PL Premium doe not. It also expands as it cures, so your clamping pressure would have to be pretty substantial.


Rolling on a layer of epoxy between core and skin should be pretty idiot proof, and wouldn't require a whole lot of clamp pressure.
 

The Artisan

Adventurer
I'm strongly considering building a press to mfg custom panels for future builds.

It wouldn't be terribly hard. And would allow me to mfg panels with whatever skins and core I want, all bonded with a good marine epoxy.
I am in that process right now. I have a 5hp blower used for my CNC fabric cutting table so its easy to move the connection back and forth. I was told 2psi min for 3 hours or so using an industrial Gorilla glue.
Kevin
 

rruff

Explorer
In order to get a panel bonded 100% flat to a core, you need the adhesive to flow well. PL Premium doe not. It also expands as it cures, so your clamping pressure would have to be pretty substantial.
Rolling on a layer of epoxy between core and skin should be pretty idiot proof, and wouldn't require a whole lot of clamp pressure.

PLP doesn't need much clamp pressure, it actually works quite well with none, since it is very sticky out of the tube. Use a notched towel to spread it and get an even coat, no flowing necessary. It should expand some amount as it cures, but I didn't notice any. Since it starts as a thin coat, I'm guessing it doesn't amount to anything. My panel skins seem to be intimately stuck to the foam as evidenced by cutting through the panels. Skins are covered with a good layer of foam when they are ripped off.

I don't know how much you've investigated bonding to foam, but I know of several people who have had problems with epoxy and XPS. It is definitely not a sure thing with any adhesive. Deep scoring helps a lot, sanding alone doesn't do it. And filling that scoring with epoxy would get expensive. For panels I think thickeners are commonly used with epoxy.

Anyway, big advantages to PLP are lower cost and not being temperature sensitive.
 

IdaSHO

IDACAMPER
Lots of different epoxies around. But thanks for the heads up.

Where have you heard about bonding problems with XPS and epoxy? Any links?

And I'm still not seeing the benefit of PL for panel construction. Its simply too thick.

You are referring to the loctite brand in the caulk tube, right?

The stuff is the consistency of peanut butter.


And my mention of clamp load isn't related to what the PL needs, but instead the clamp load that would be required to compress/squish the PL to the point of being one uniform (thin) layer between the core and the skin.


ALL that said, a polyurethane adhesive is certainly a viable option. Maybe Gorilla glue? Its certainly thin enough.
 

rruff

Explorer
Lots of different epoxies around. But thanks for the heads up.
Where have you heard about bonding problems with XPS and epoxy? Any links?
And I'm still not seeing the benefit of PL for panel construction. Its simply too thick.
You are referring to the loctite brand in the caulk tube, right?
The stuff is the consistency of peanut butter.

No links handy, but if you search XPS, fiberglass, and surfboards, you'll find some links. That's where I got the idea for the carpet seam roller, a surfboard builder trying to solve the problem. Also, there is someone who posted a build thread on ExPo, pop up camper I think, and his fiberglass over XPS debonded when exposed to heat. There was another camper build too that had similar issues, but not on ExPo.

I thought PLP was thick also, but troweling it seems to work well. Yep, it's Loctite. I've heard of people thinning it with a solvent, xylene I think? But I'm happy with how it works out of the tube. I wouldn't call it peanut butter thick. Maybe organic peanut butter ;).

Loctite actually recommends against using it on styrofoam, but I've read about many people using it successfully with no one reporting a problem. The "foamie" camper builders on tnttt use it a lot. The PL300 that's recommended for foam is useless. Very weak.
 

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