Plywood camper fabrication questions (thinking of idaSho)

[ReluctantTraveler]

You don't need multiple panels, you build each as one piece. You need multiple pieces of ply for each side, but these are butted together at the center of a wood rib. That isn't a real strong junction, but I never had an issue with them... and it would be the same if you framed it out first.

You can angle cut the wood on the edges all you like. If it's a 90 degree junction you don't need to.

Are you planning to use marine ply?

something just clicked for me. Thanks!

And yes, marine grade ply from a supplier up near me. I live near a coast.

 

[ReluctantTraveler]

Attaching the panels to each other is super easy. The edges will be solid wood. Just screw and glue.

Regarding the door and window placement, I guess I can't relate. That is pretty straightforward, and you really won't know for sure until it's all enclosed and built out. Plus I'd absolutely glue the wood pieces together, so they wouldn't be coming apart anyway.

But... you can do what you like... that's the beauty of DIY!

I’d imagine you glass the whole thing after assembly?

 

[rruff]

I’d imagine you glass the whole thing after assembly?

I'd glass it while it's laid flat since it's much easier. Then put another layer on the edges when assembled. You can buy what they call "tape", which is just rolls of narrow width cloth with woven edges.

If you are using quality ply, 6mm would be overkill I think. 4mm would be plenty... or even 3mm for side walls. Especially if you use PVC foam. But make samples and see what you are happy with. On the other hand, with an F550 rig, the shell weight will be a pretty tiny fraction of your payload, so no reason to worry about it too much.

If you are considering CC PVC foam, it's about 2.5x the weight of 25psi XPS, which for a 2" thick panel means you'd add about 0.4 lbs/sq ft. Looks like they haven't raised prices much. The 2" is $237, 1.5" is $169. https://www.carbon-core.com/product/pvc-structural-foam-sheets/

Do you have a sketch of how your camper will be shaped?

 

[ReluctantTraveler]

I'd glass it while it's laid flat since it's much easier. Then put another layer on the edges when assembled. You can buy what they call "tape", which is just rolls of narrow width cloth with woven edges.

If you are using quality ply, 6mm would be overkill I think. 4mm would be plenty... or even 3mm for side walls. Especially if you use PVC foam. But make samples and see what you are happy with. On the other hand, with an F550 rig, the shell weight will be a pretty tiny fraction of your payload, so no reason to worry about it too much.

If you are considering CC PVC foam, it's about 2.5x the weight of 25psi XPS, which for a 2" thick panel means you'd add about 0.4 lbs/sq ft. Looks like they haven't raised prices much. The 2" is $237, 1.5" is $169. https://www.carbon-core.com/product/pvc-structural-foam-sheets/

Do you have a sketch of how your camper will be shaped?

yea, I’m not worried about weight much. I’ll get something posted soon. All of my sketches are rough notebook scratch at the moment.

 

[ReluctantTraveler]

Do you have a sketch of how your camper will be shaped?

Here's a sketch for you. The arrow is the part I'm most concerned about.

I'm confident the composite panel can support the weight, but I'm not sure how to secure the bottom in such a way that it properly handles load.

If I had to guess, you'd say that you glue and screw all of the seams, and that distributes the load across the walls (and ultimately up to the roof as well). In other words, the weight isn't solely at the bottom joint, but across all of the seams where it meets the other panels. Is that right?

 

[ReluctantTraveler]

@rruff You should have told me you were answering the same exact question a day earlier in another thread! Sorry for asking you a bunch of questions you were already answering elsewhere!

Structural stability for my Camper box build and materials selection.

That looks ... TY ...that means I can't get rid of it... ?

expeditionportal.com

 

[rruff]

@rruff You should have told me you were answering the same exact question a day earlier in another thread! Sorry for asking you a bunch of questions you were already answering elsewhere!

Ha, not really! I missed your earlier post for some reason.

I don't know if this will help, but if you look at the sides of the cabover, that is a very tall and strong support beam on each side. It's going to take a lot of force to bend that vertically much at all. So the floor of the cabover has very good support around its perimeter. You just need to make the floor stiff enough that it doesn't sag in the middle... which you will see is easy to do if you make a sample piece.

BTW regarding the plywood sheets, it is good to consider high stress areas when you lay out the places where they butt together. You wouldn't want to do that right where the cabover starts for instance; best to have full sheets for the sides of the cabover, that extend into the main walls. Make sense?

That edge of the cabover meets the lower wall seems like it could be an issue with a sharp corner... but I really doubt it. Maybe if it was just foam core, but where those panels meet you are going to have solid wood, which I think would be plenty stout. At the link below you can see some braces that others have used to address that, DDG, and thumbnail for ArcLab farther down. Overkill or piece of mind... ?

How far back from the frame rails should you go for habitat?

Tumbling ideas around my head. Assume a F550/5500 crew cab chassis truck with a custom frame mount. Something like a Total Composites box on top and proper SRW conversion with something like Liquid Springs and 2" lift and 42" GoodYears etc. Use case: casual off road - bad forestry roads...

expeditionportal.com

I changed your sketch a little just to show different possibilities. One thing you can do is use your front wall as storage; in which case you can extend your cabover floor panel inside a couple feet and attach it to the walls. I'm pretty certain that will eliminate any concern at that point you marked. At any rate that's what I've done with mine with just foam in the core, and I'm not worried about it in the slightest.

I realize this isn't drawn to scale, so I don't know if you were planning on a NS bed or not, but I'd highly recommend it... which is another good reason to extend the bed floor inside a bit. It's way easier for two people to use that space if you don't have to climb over each other.

I can't find it right now, but I remember an old vehicle aero analysis, and it showed that rounding the leading and upper edges made a huge difference. Since you have solid wood on the edges you can shape them pretty easily. I put an aero nose cap on the front, carved out of foam and fiberglassed, to give it a bigger radius.

 

[ReluctantTraveler]

Ha, not really! I missed your earlier post for some reason.

I don't know if this will help, but if you look at the sides of the cabover, that is a very tall and strong support beam on each side. It's going to take a lot of force to bend that vertically much at all. So the floor of the cabover has very good support around its perimeter. You just need to make the floor stiff enough that it doesn't sag in the middle... which you will see is easy to do if you make a sample piece.

BTW regarding the plywood sheets, it is good to consider high stress areas when you lay out the places where they butt together. You wouldn't want to do that right where the cabover starts for instance; best to have full sheets for the sides of the cabover, that extend into the main walls. Make sense?

That edge of the cabover meets the lower wall seems like it could be an issue with a sharp corner... but I really doubt it. Maybe if it was just foam core, but where those panels meet you are going to have solid wood, which I think would be plenty stout. At the link below you can see some braces that others have used to address that, DDG, and thumbnail for ArcLab farther down. Overkill or piece of mind... ?

How far back from the frame rails should you go for habitat?

Tumbling ideas around my head. Assume a F550/5500 crew cab chassis truck with a custom frame mount. Something like a Total Composites box on top and proper SRW conversion with something like Liquid Springs and 2" lift and 42" GoodYears etc. Use case: casual off road - bad forestry roads...

expeditionportal.com

I changed your sketch a little just to show different possibilities. One thing you can do is use your front wall as storage; in which case you can extend your cabover floor panel inside a couple feet and attach it to the walls. I'm pretty certain that will eliminate any concern at that point you marked. At any rate that's what I've done with mine with just foam in the core, and I'm not worried about it in the slightest.

I realize this isn't drawn to scale, so I don't know if you were planning on a NS bed or not, but I'd highly recommend it... which is another good reason to extend the bed floor inside a bit. It's way easier for two people to use that space if you don't have to climb over each other.

I can't find it right now, but I remember an old vehicle aero analysis, and it showed that rounding the leading and upper edges made a huge difference. Since you have solid wood on the edges you can shape them pretty easily. I put an aero nose cap on the front, carved out of foam and fiberglassed, to give it a bigger radius.

View attachment 767519

I planned on a North/South bed orientation, so no climbing over each other ?

good call on where the plywood seams end for the cab over. I can’t put storage up front because we’re at max length for the flatbed already and I want to maximize internal floor space.

do I need to use lag bolts where the bed floors meets the front wall, or special grade screws?

as for core composites, it looks like their thickest PVC foam is 1.5”. How would you vid 3” floor/roof pieces? Different product? Two foam boards glued together?

 

[ReluctantTraveler]

@rruff oh, and how do you get chest cuts with the foam? I hear it’s tough to work with.

 

[rruff]

Well, you gotta put storage somewhere, and low and forward is the best place for weight.

When the panels just have foam in the core they probably just glue those supports. So I think normal screws and glue would be fine. You don't need to get crazy with those; you could shape some thick ply, screw and glue them in place, and finish like the rest of the camper.

CC has 50mm PVC foam which is 2" thick. I think they will make 3" for you; they cut it in house from big blocks. Build a sample piece using parts from the hardware store, and see if you think 2" would be adequate.

Also, since you have a basement, it seems like it would be real easy to make that very solid by connecting the walking floor to the exterior base. Yes?

I don't know what a "chest cut" is, but I cut all my foam free hand with a long blade utility knife. A saw creates a hell of a mess with tiny particles. Tried a saber saw with a knife blade but that didn't work too well.

Will you building this in a large shed? I wondered if you'd have an easy way to lift panels from the ceiling.

 

[ReluctantTraveler]

@rruff DUDE! Just a quick aside to say, "Thanks for taking so much time to respond to all of my questions!" ?

Do you have a build thread, btw? I'd love to see your work-in-progress!

Well, you gotta put storage somewhere, and low and forward is the best place for weight.

I'm planning to build this on the max WB F-550/5500, with an 11' flatbed and a 1.25' basement in the habitat.

All of my heavy storage—water, propane, batteries—are going in the basement, close to the front, to keep the weight low and centered between the axles.

I also planned on adding storage boxes to the flatbed itself for keeping all of the gear that doesn't need to be temperature controlled: camp chairs, tools, etc.

When the panels just have foam in the core they probably just glue those supports. So I think normal screws and glue would be fine. You don't need to get crazy with those; you could shape some thick ply, screw and glue them in place, and finish like the rest of the camper.

Cool! I can 100% see the value in building a test panel, by the way. I'm an "I need to see it" kind of person, so having a tangible panel to mess with would be really helpful.

CC has 50mm PVC foam which is 2" thick. I think they will make 3" for you; they cut it in house from big blocks. Build a sample piece using parts from the hardware store, and see if you think 2" would be adequate.

The Core Composites you're talking about is not this company from Rhode Island that also makes structural PVC foam, right?

ABOUT | Core Composites

Rhode Island-based distributor of advanced composite materials and project management company

www.corecomposites.com

I ask because these dudes are within an hour or two drive from me, which would be really helpful if their stuff is good.

Also, since you have a basement, it seems like it would be real easy to make that very solid by connecting the walking floor to the exterior base. Yes?

That's a good point!

I'd planned to have a single exterior wall, with vertical interior studs that walking floor mounted into. But those studs would be attached to the exterior wall, and add more structural support.

I was also planning to place the entry door "in the basement," with a step or two into the main living area. That would provide a lower entry with storage for boots/shoes, and make keeping dirt and dust out of the main living area a bit easier than it is now in our cheap travel trailer.

I don't know what a "chest cut" is, but I cut all my foam free hand with a long blade utility knife. A saw creates a hell of a mess with tiny particles. Tried a saber saw with a knife blade but that didn't work too well.

That was supposed to say "clean cuts," but autocorrect on the latest version of iOS has gotten much worse. Sorry about that!

Yea, I'd heard that saws make a mess of things. Utility knife it is!

Did you warm it up at all? I'd seen in one video that using a heated blade helped it slide much more smoothly through the foam.

Will you building this in a large shed? I wondered if you'd have an easy way to lift panels from the ceiling.

That part is still TBD.

I have a standard sized garage I could fabricate the panels themselves in. But when it comes time to assemble, I'll need to do that outside unless I can find a workshop with rental space to do everything.

 

[rruff]

A heated blade may work but I just used a normal one. Scribe a shallow cut right on the line, and then cut a little deeper each time.

Fill any gaps between the foam and wood with spray foam or something.

Unless your "standard size garage" is a lot bigger than mine, a full side panel won't fit in there. They are also going to be heavy!

Carbon Core: https://www.carbon-core.com/product/pvc-structural-foam-sheets/ Let us know what the other place charges, as they don't list prices.

 

[ReluctantTraveler]

A heated blade may work but I just used a normal one. Scribe a shallow cut right on the line, and then cut a little deeper each time.

Fill any gaps between the foam and wood with spray foam or something.

Unless your "standard size garage" is a lot bigger than mine, a full side panel won't fit in there. They are also going to be heavy!

Carbon Core: https://www.carbon-core.com/product/pvc-structural-foam-sheets/ Let us know what the other place charges, as they don't list prices.

For the store you linked to, did you choose rigid or scored for the surface treatment?

 

[rruff]

For the store you linked to, did you choose rigid or scored for the surface treatment?

Always rigid. Scored is for tight curves I think. I have some curved sections on the cabover and roof, but I bent and glued .75" sheets for that.

 

[ReluctantTraveler]

@rruff Once I let them know desired thicknesses and quantities, they're going to send pricing. But I've attached the spec sheet.

I'd love your perspective on which of the four available weights/densities makes the most sense for a project like this, and how on earth to figure out R-value from the conductivity ratio provided.