Box Wall construction

[svenwesley]

Ha ha ha! Great site. Two cameras dedicated for crash monitoring. And I though my hobbies are weird.

I found this one in another build thread.

 

[david506th]

Douglas fir has the same density as pine.

While true, you are looking at density as a product of strength & weight. Go pick up Fir then go grab Yellow Pine, you will immediately feel the difference in weight. Since this is a vehicle based build, Fir would be a much better choice for your weight to strength ratio along with its other qualities.

 

[pairospam]

Hello Svenwesley:

I agree with the idea of the composite sandwich panel with no wood in it, at all. Check www.stadur.com as another source of inspiration.

If you like, I can give you the proper contact coordinates.

Good luck with your project.


Pairoa

 

[Joe917]

Ha ha ha! Great site. Two cameras dedicated for crash monitoring. And I though my hobbies are weird.

I found this one in another build thread.

This is the construction of my camper box except that the wall is 2 1/2" thick (more foam). The roof is 3" without plywood on the exterior. The floor is 4" with 1/2" ply inside and none on the exterior side. There are plywood ribs in the panels but I do not know what the spacings are.

The box is very solid and comfortable with no signs of failure. The only problem I have had is where some clown cut the roof open to put in a backing pad for a roof mount then made a very bad patch repair. All good now.
The box is now 22 years old and traveled to 5 continents.

Done right this is probably as strong as you can get. Do not hesitate to use plywood in the sandwich. It has been used with great success in the boat building world for many years.

 

[svenwesley]

This is the construction of my camper box except that the wall is 2 1/2" thick (more foam). The roof is 3" without plywood on the exterior. The floor is 4" with 1/2" ply inside and none on the exterior side. There are plywood ribs in the panels but I do not know what the spacings are.

The box is very solid and comfortable with no signs of failure. The only problem I have had is where some clown cut the roof open to put in a backing pad for a roof mount then made a very bad patch repair. All good now.
The box is now 22 years old and traveled to 5 continents.

Done right this is probably as strong as you can get. Do not hesitate to use plywood in the sandwich. It has been used with great success in the boat building world for many years.

Thanks for the info Joe!

Yes, wood seems OK. We make a lot of prototypes and one off builds in the workshop with wood core. Fast rowing boats and kayaks that are tested and then used as plugs for making the production molds. We have a few racing yachts around here made in fiber/epoxy sealed strip wood core and they look like new after 15 years of abuse. I was more worried about the movement in the box and that it will make the seal crack somewhere, but the more I search the more campers I find with wood in the structure.

I still talk to the PIR-insulation company and they can make some extra boards next time they run a paper foiled batch. I did get a decent price, right now it's uncertain when they can make them. If it takes a long time I will probably go back to my old ideas with (ply)wood strips.

 

[svenwesley]

I was at the hardware store the other day and bought some different sheets. I tried to source S100 EPS but they only had S80 at the moment (different densities, S100 is heavier). I also bought a sheet of PIR, which is more than twice as dense as the EPS I have. I'll make some wall samples and do some destructive testing, it will give a good figure how the construction will work. The sheets are 30 mm thick and my plan is to use 40-50 mm when I finally build the walls. If a sandwich construction is doubled in thickness it will roughly be four to seven times stronger (depending on layup and material). Going from 30 to 40 will make a huge improvement in stiffness, but still I will get a good hint with the sheets I have.