DIY Composite Flatbed Camper Build

[Stingy49]

I really like the exoskeleton they did... is that your plan? You good with CAD? I'd be curious to know what that would cost. I guess they also got the panels CNC cut?

If you only have the aluminum on the outside and no inner reinforcement it makes sense to use thicker material. 3/16 seems about right.

If this is representative, it's quite weak compared to the PVC foam. https://www.carbon-core.com/pdfs/pds-carbonfoam-pu-pir.pdf

https://www.carbon-core.com/pdfs/pds-carbonfoam-pvc.pdf

I'm decent with CAD. It's part of my job so I use it a fair bit. I plan to cad up my whole subframe/exo/body. I've actually already got a rough model of the truck that I've been using to size the body.

Yeah I like the alu on the outside only, like everlanders and turtle V did.

Those foam compressive strength numbers are similar to what I linked so I bet the rest are close. While the 90 psi comp strength at 4lb/cf doesn't scare me the ~2000 psi comp modulus does compared to the ~6000 of PVC foam. I wonder what XPS is. I'll google it tomorrow. If it's better than XPS, not much concern. Cause the cost is comparable to $40 2" XPS sheets with better strength so if the bond is good you're golden. Saves on epoxy cost also because you could cast it onto the foam. At least that's what I interpreted the datasheet to say about the VR2 panel's cloth backing.

Edit: 40 psi XPS is 1400 psi compressive modulus, 60 is 2200, and 100 is 3700.

It's dangerous for me checking the forum at night way to easy to end up staying up late thinking about this stuff.

@Terra Ops Thanks for the link to the other page. Definitely some good info to look at there. That bridge composite panel link could be interesting.

 

[Watersmeet]

If you want to reinforce the XPS I'd use wood. Get some 1x or plywood and cut it into strips that are the thickness of your panels. Then cut your foam into 1 foot wide vertical strips, and glue the wood in between each piece of foam. I'd probably use PLPremium for that. Then you'll have a foam panel with a wood stringer every foot that bridges the two sides of the panel.

You could also use the lightest luan (2.7mm) on the interior walls... would be pretty and save money to boot. Believe it or not the stiffness is better than the composite sheet. You could even use that for the exterior too and put a layer of wet FG on it. I've done this, I know it works well.

Wow this is great! I have been wanting to build a truck camper for about a year, maybe a little less. I’m ready to build now and have been trying to decide which way to go. I want light weight, low cost, great quality and great insulation. In the last couple of months I’ve made my mind up and decided on a few different methods of construction, always changing my mind after a while to another idea or some build I saw that looked great. Then I came up with an idea I hadn’t seen anywhere and it seemed like I had found my answer. It was 25psi XPS panels with plywood laminated on both sides with epoxy. Okoume marine ply on the outside and luan or something similar on the inside. That’s so awesome that you suggested using wood. You guys are many levels above me on this stuff and I really appreciate your help.

So when I added up the weight of all the materials for the amount of materials I’d need and it was 610lbs. That’s just for the shell, with nothing inside at all. That’s with 1/4” ply in and out (Okoume is 21lbs per 4x8 and luan is 17lbs ( .65lb/ft2 and .53lb/ft2 ) And then I was calling around about windows and doors a very nice and helpful guy at one company told me my build was going to be too heavy and not good. And then I went looking for more familiar methods people are using and then I got on to the FRP on foam. That stuff is so attractive. It’s completely finished when you buy it, how great is that? At one point I considered making my own wet layup panels but the amount of work and time doing the layup, sanding and sanding, fairing, sanding, painting, painting, painting all to get to where the FRP is when you buy it. It really seems like great stuff and a really solid choice.

My original idea’s plan for the seams was going to be three layers of 12oz fiberglass tape, or more of needed, effectively making a fiberglass frame over all the seams. I’d mitre cut the panels to fit together so there’s maximum surface area of each panel all the way to the very edge of the corner for the epoxy and fiberglass to really bond and seal well. Since square angles in fiberglass are very weak and rounded angle changes are very strong I’d soften the corners, and have three or more layers of heavy 6” tape, or maybe 6”, 5”, 4”, etc.

Do you guys think there’s a point where enough fiberglass would be a strong enough frame, or is it always just going to crack? What would you guys do on the exterior edges?

 

[rruff]

At one point I considered making my own wet layup panels but the amount of work and time doing the layup, sanding and sanding, fairing, sanding, painting, painting, painting all to get to where the FRP is when you buy it. It really seems like great stuff and a really solid choice.

Easy to solve that problem... just skip it. I mix up some microspheres and epoxy and cover/fair with that a little but I sure as hell don't try to make a perfect flat finish. Use a roller with some texture for the UV coat, it will cover a world of sins. When I'm using the camper it will be covered in dirt and scratches... don't think it needs to be too pretty. Just good enough so the cops don't bother me, and janky enough that thieves ignore it .

Do you guys think there’s a point where enough fiberglass would be a strong enough frame, or is it always just going to crack? What would you guys do on the exterior edges?

If you are talking FRP/XPS you want a healthy exterior radius. If it's a 90 degree joint, I'd have the outer FRP an inch+ short, and round the foam to taste. Then cover that, overlapping the FRP. Sure it will be strong enough if you do a good job!

You could also edge the panels with wood edges so you have a solid edge you can screw and glue together. You'd still need to round it and wet lay the corner, but this would be stronger, and you'd need less FG.

Make sure the FG bonds well to the FRP of course...

My panels are wet-laid and I'm going to leave an outer gap of at least an inch at each joint. This will be filled with epoxy and fumed silica, and rounded. Then the extra FG layers go over that. The inner seam will have a radius of epoxy/fumed silica and then FG there as well. You could do something like that if you wanted, too... many ways to do it.

 

[Terra Ops]

Wow this is great! I have been wanting to build a truck camper for about a year, maybe a little less. I’m ready to build now and have been trying to decide which way to go. I want light weight, low cost, great quality and great insulation. In the last couple of months I’ve made my mind up and decided on a few different methods of construction, always changing my mind after a while to another idea or some build I saw that looked great. Then I came up with an idea I hadn’t seen anywhere and it seemed like I had found my answer. It was 25psi XPS panels with plywood laminated on both sides with epoxy. Okoume marine ply on the outside and luan or something similar on the inside. That’s so awesome that you suggested using wood. You guys are many levels above me on this stuff and I really appreciate your help.

So when I added up the weight of all the materials for the amount of materials I’d need and it was 610lbs. That’s just for the shell, with nothing inside at all. That’s with 1/4” ply in and out (Okoume is 21lbs per 4x8 and luan is 17lbs ( .65lb/ft2 and .53lb/ft2 ) And then I was calling around about windows and doors a very nice and helpful guy at one company told me my build was going to be too heavy and not good. And then I went looking for more familiar methods people are using and then I got on to the FRP on foam. That stuff is so attractive. It’s completely finished when you buy it, how great is that? At one point I considered making my own wet layup panels but the amount of work and time doing the layup, sanding and sanding, fairing, sanding, painting, painting, painting all to get to where the FRP is when you buy it. It really seems like great stuff and a really solid choice.

My original idea’s plan for the seams was going to be three layers of 12oz fiberglass tape, or more of needed, effectively making a fiberglass frame over all the seams. I’d mitre cut the panels to fit together so there’s maximum surface area of each panel all the way to the very edge of the corner for the epoxy and fiberglass to really bond and seal well. Since square angles in fiberglass are very weak and rounded angle changes are very strong I’d soften the corners, and have three or more layers of heavy 6” tape, or maybe 6”, 5”, 4”, etc.

Do you guys think there’s a point where enough fiberglass would be a strong enough frame, or is it always just going to crack? What would you guys do on the exterior edges?

I'm really not qualified to speak towards overlaying on the panels. My concern would be flexing and cracking. I would imagine the frp panels would need sufficient glass composition for adhesion.
GXV and Earthroamer use the mono shell, but that's a different animal and costs $$$$$$$$. Another forum member, Diplostrat, owns an XP Cube that had panels glassed in the corners. I think there may have been an initial concern, but I think there have been no issues. Perhaps he will chime in. I think some aluminum angle was added, just not sure the purpose.
Most panel construction I've seen uses some type of extrusion.
One thought that comes to mind; if you construct the panel with an outer frame of wood, meaning a 2x something embedded as part of the panel, when you mitre the panels to fit, this wood edge would be bonded, screwed, etc. to each other for strength. The seam could be sealed and covered with a small aluminum L channel or just glass it. So many facets to this!!!

 

[rruff]

So when I added up the weight of all the materials for the amount of materials I’d need and it was 610lbs. That’s just for the shell, with nothing inside at all. That’s with 1/4” ply in and out (Okoume is 21lbs per 4x8 and luan is 17lbs ( .65lb/ft2 and .53lb/ft2 ) And then I was calling around about windows and doors a very nice and helpful guy at one company told me my build was going to be too heavy and not good.

That's not heavy for a camper you can stand in and has a cabover. Not at all. You can save some weight by using thinner ply; 3mm is plenty with 25psi foam. If you can get 1.5" foam, put a 1x2 on edge inside the panel every foot or so (maybe 2' would be fine actually). Pretty simple and not a lot of work, and lots of hard points for mounting inside. No worries about foam failing. At each edge, install a mitered 2x2; makes it easy to join panels. Use a router to make a nice exterior curve, or just cut it and hit it with a flap disc to round it. Then FG the exterior. I actually did all my flat surfaces on the ground and just did the joints after it was put together.

Wood is great stuff IMO. It gets a bad rep because of all the crappy campers built with wood frames and a bunch of external screws and seams. Water gets in and it rots. Eliminate the strews and seems, and you'll have no worries.

Plus I think it's beneficial to have a step down in hardness/strength/weight for impact. In this case you'd have FG (to taste... I'd say at least .5mm), then a 3mm layer of ply, then the reinforced 25psi foam.

If you like the idea, build a sample... I think you'll be impressed.

 

[Watersmeet]

Thank you all so much! I really appreciate all this invaluable information. Your input has really boosted my confidence helped eliminate some bad ideas and validate some good ones. I don't want to hijack @TerraOps incredibly impressive build thread and I think I'm ready to get started, so start my own thread if I have more questions.

Well shoot, maybe I'll just talk about epoxy for a second.

That Adtech epoxy at Soller looks really good, great price, UV safe and no blushing. I've been using US Composites epoxy but don't want to use it any more. The price is great but some of it's specs seem very low, and it's blushes badly and isn't uv safe. The Adtech appears to be a great choice, and it's not that expensive, but if I want to use it I have to do it now. I'm in Oregon and Soller says if you have to work below 80 degrees don't use the Adtech, use something else instead. I don't have a heated shop and July and August are the only months when every day is almost always above 80. So I gotta get started. Originally I was going to use System Three which doesn't blush either and if you use System Three epoxy and System Three WR-LPU paint you don't have to use primer, but the Sys3 is not UV safe so it does need paint of something on it.

One funny thing happened when I called Soller to ask about the nano tubes, I said I hadn't seen any mention of blushing on their web site and asked if the Adtech epoxy blushes at all. The response was that I had used an unfamiliar word, this word blush. "What? Does it what?" I described it's an amine blush and there's a waxy greasy secretion that needs to be washed off and that some epoxies do it. I heard "WAX? Wax comes out?!" So I suppose that's good news, if it blushes they'd definitely know about blushing. ?

Most of the high end epoxy specs are pretty similar, except for one: tensile elongation. This could be off or wrong, but my understanding of tensile elongation strength comes into play during an impact. For example when hit by a hammer how much will the epoxy crack and window pane due to it's inability to stretch and absorb the impact, or how much can it resist cracking when it's stretched and stressed by twisting on a camper? The tensile elongation of System Three is the highest at 11%, Adtech is 3ish%, West Systems is 3.4% and US Composites is 1.6%

 

[Stingy49]

That Adtech epoxy at Soller looks really good, great price, UV safe and no blushing. I've been using US Composites epoxy but don't want to use it any more. The price is great but some of it's specs seem very low, and it's blushes badly and isn't uv safe. The Adtech appears to be a great choice, and it's not that expensive, but if I want to use it I have to do it now. I'm in Oregon and Soller says if you have to work below 80 degrees don't use the Adtech, use something else instead. I don't have a heated shop and July and August are the only months when every day is almost always above 80. So I gotta get started. Originally I was going to use System Three which doesn't blush either and if you use System Three epoxy and System Three WR-LPU paint you don't have to use primer, but the Sys3 is not UV safe so it does need paint of something on it.

I think when he talks about curing and 80*F he doesn't mean it has to constantly be above 80*f. Epoxy cure time can vary dramatically with temperature. When I talked to him on the phone he said if my piece were small enough, it could cure in 2-3 hours at 140*f. He also talked a lot about other ways to tell when it is done curing (no odors, can't scratch/dent with a finger fingernail). So I think as long as it is getting above 80*F during most of the day you'll be fine.

I'm going to try and peel test my panels tonight and over the 48 hours they've been sitting I'll have given them ~20 hours of above 80*F time and a few hours of +90*F time from the midday heat here in Sacramento.

-Derek

 

[rruff]

I use Ebond with the slow hardener so far. Last time I bought some (2 years ago?) it was only $30/gal (plus shipping)... and I liked it better than anything else I've tried. Never seen any blush. Slow hardeners are less likely to blush, and dry conditions was less likely to blush. If the person you talk to sounds clueless about blushing, my conclusion is that they are clueless... not that the epoxy doesn't blush.

Don't know that I'd put a lot of faith in the elongation numbers. Also note that the glass is the strong and stiff part of the matrix, so you only need to match that. If you aren't going to use much epoxy, then might as well get the expensive stuff, though.

Oh... and another thing. You need to put a UV coat over epoxy no matter what type it is. At best it is UV resistant.

Regarding "twisting and stretching of the camper", you'd best avoid this in any case by letting the camper mount independent of the frame if the frame is flexible (some trucks are and others aren't). If not, then you need to make the camper flexible rather than stiff. What truck is it going on and how is it mounted?

 

[Stingy49]

I did the peel testing tonight. I'd love to hear what y'all think about its strength compared to yours.


-Derek

 

[rruff]

Seems very weak... did you sand it? As I recall my XPS samples stuck better than that. Make sure you use plenty of adhesive. And the PVC foam takes more strength than I have to pull it apart. I can't even get it started.

Note that your panels have to carry shear loads in bending (the foam too!), and there will be lots of vibration.

 

[Stingy49]

Seems very weak... did you sand it? As I recall my XPS samples stuck better than that. Make sure you use plenty of adhesive. And the PVC foam takes more strength than I have to pull it apart. I can't even get it started.

Note that your panels have to carry shear loads in bending (the foam too!), and there will be lots of vibration.

Interesting. Glad to have a point of reference. I'm gonna do a 4' by 8" test strip of the foamular 400 so I can put a bigger load on it. I will go heavier (probably shoot for overkill) on the epoxy to try and get a good bond. I will also use some mulch bags to weigh it down more evenly than the warped wood.

-Derek

EDIT: Yeah with 60 grit. I will take a closer before and after this time to show the amount of sanding.

 

[Terra Ops]

I'm still wondering about the VR2. From the video it doesn't look smooth where the epoxy bonds to the foam. Also, not sure of glass content and if that makes a difference.
You stated "My FRP seems to have a light fabric on the back so I wonder if that will help adhesion (http://www.uslco.com/download/VRTech_W.pdf, mine is VR2)." Light fabric?
I recall the edges being tricky to lay flat. I would use tape or clamps to hold them down. Below is a pic of the bonding side for the frp I used. It's smooth, rigid, and you can see the glass content. Weight on the panel while curing is also important. I used the slow cure epoxy as it is suppose to give maximum strength. Takes about a week for full cure. If you go back to post #1, I used regular 3/4" foam found at Lowes. When bonded with the FRP using the adtech slow cure epoxy, this thin piece of foam could support my weight.

 

[rruff]

Interesting. Glad to have a point of reference. I'm gonna do a 4' by 8" test strip of the foamular 400 so I can put a bigger load on it.

I'd suggest a narrower piece so you can more easily take it to failure. 4" wide should easily hold your weight with a 48" span and center load... ~360lb before the core fails, but whatever you weigh you should be able to break it with a good stomp.

If you look at the foam test page I linked earlier, you can see that a lot more of the foam pulls up when the foam is textured. That doesn't necessarily mean it took more force though! But you should definitely have foam attached over the whole surface when you pull the skin off.

You stated "My FRP seems to have a light fabric on the back so I wonder if that will help adhesion. Light fabric?

In the video you can see that. It could be there to soak up adhesive and provide a better bond?

 

[Watersmeet]

Regarding "twisting and stretching of the camper", you'd best avoid this in any case by letting the camper mount independent of the frame if the frame is flexible (some trucks are and others aren't). If not, then you need to make the camper flexible rather than stiff. What truck is it going on and how is it mounted?

It will go on a 2000 F-350, crew cab, long bed. I will remove the bed. I need to learn more about the mounting options and preferences. Keeping the cost down is imperative. A flatbed obviously allows the truck to remain useful without the camper mounted, which seems like a really good choice.

 

[Stingy49]

Laminated a larger panel today. Also tried emulating dog hair brush scuffing on part of it.