15mm ply on walls and platform

[shiftsave]

Hi everyone!

I live in NZ where 3/4in XPS boards are non-existant, although just found a supplier of 15mm boards.

With that I am thinking on changing my design to a 27mm floor (6mm/15mm/6mm) and 31.2mm walls 1.2(alum)/6mm/15mm/9mm.

Curious if anyone sees an issue with those dimensions?

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[noseoil]

I think the floor scantlings are a bit on the stout side for a small trailer. You could get by with 4mm on the underside (we used it for the top & bottom of the deck, with 19mm stick-framing, insulation & a thick mattress). The walls could also be 4mm inside or outside, with some sheet foam in the framing. Materials are a tough one at times, due to availability, supply & quality.

[shiftsave]

I think the floor scantlings are a bit on the stout side for a small trailer. You could get by with 4mm on the underside (we used it for the top & bottom of the deck, with 19mm stick-framing, insulation & a thick mattress). The walls could also be 4mm inside or outside, with some sheet foam in the framing. Materials are a tough one at times, due to availability, supply & quality.

Thanks!

If I understand you correctly, you think the floor walls could be taken down to 4mm? Do you see any problem moving from 18mm to 15mm for the walls skeleton and floor framing due to the insulation issue I mentioned?

The overall trailer is roughly 2700x1540mm, queen mattress inside and a Yeti cooler and built in HOB/sink on the galley

[MickinOz]

I do believe that those people who use extra thin decking on their floors are relying on the compressive strength of the XPS foam.
If you screw a 4mm floor sheet down so that the sheet is pressing on the foam and the foam is transferring some of the load to the bottom sheet, you have more strength than a single 4mm sheet can provide as the load is being shared with the bottom sheet.
Assuming your original plan for the floor was 6mm sheet, 19mm frame, 6mm sheet, with 19mm xps foam to help share the load to the bottom sheet, you are now proposing to do the same thing but simply make the frame narrower.
I'd do that. If it were my trailer, I would stick with the 6mm floor sheets. In my mind. it's the one place I would not want to skimp.
But there is a lot of variables.
What centres are your cross members on, for example? The narrower the gap you floor sheet has to span, the thinner you can get away with.
But for me, getting away with it is not something I want to do. I want the floor to be a dead cert.

[shiftsave]

I do believe that those people who use extra thin decking on their floors are relying on the compressive strength of the XPS foam.
If you screw a 4mm floor sheet down so that the sheet is pressing on the foam and the foam is transferring some of the load to the bottom sheet, you have more strength than a single 4mm sheet can provide as the load is being shared with the bottom sheet.
Assuming your original plan for the floor was 6mm sheet, 19mm frame, 6mm sheet, with 19mm xps foam to help share the load to the bottom sheet, you are now proposing to do the same thing but simply make the frame narrower.
I'd do that. If it were my trailer, I would stick with the 6mm floor sheets. In my mind. it's the one place I would not want to skimp.
But there is a lot of variables.
What centres are your cross members on, for example? The narrower the gap you floor sheet has to span, the thinner you can get away with.
But for me, getting away with it is not something I want to do. I want the floor to be a dead cert.

Thanks!

Yes, I am mostly concerned about the change from 18mm to 5mm, I think you're right on the 6mm floors, I would even be ok going up to 9 on the top to make up for the 3mm lost on the frame thickness. Any issues you might see on reducing the 18 to 15mm on the walls?

Thanks again!
Ivan

[MickinOz]

I do believe that those people who use extra thin decking on their floors are relying on the compressive strength of the XPS foam.
If you screw a 4mm floor sheet down so that the sheet is pressing on the foam and the foam is transferring some of the load to the bottom sheet, you have more strength than a single 4mm sheet can provide as the load is being shared with the bottom sheet.
Assuming your original plan for the floor was 6mm sheet, 19mm frame, 6mm sheet, with 19mm xps foam to help share the load to the bottom sheet, you are now proposing to do the same thing but simply make the frame narrower.
I'd do that. If it were my trailer, I would stick with the 6mm floor sheets. In my mind. it's the one place I would not want to skimp.
But there is a lot of variables.
What centres are your cross members on, for example? The narrower the gap you floor sheet has to span, the thinner you can get away with.
But for me, getting away with it is not something I want to do. I want the floor to be a dead cert.

Thanks!

Yes, I am mostly concerned about the change from 18mm to 5mm, I think you're right on the 6mm floors, I would even be ok going up to 9 on the top to make up for the 3mm lost on the frame thickness. Any issues you might see on reducing the 18 to 15mm on the walls?

Thanks again!
Ivan

You were happy with your design when you were designing the cavities to take 19mm foam, and now you simply want to narrow it down to 15mm to account for the available foam thickness.
I do no think there are any issues with that. But, make sure your foam is not a loose fit between top and bottom sheets in the floor. If it is tight, so that there is some transmission of load, you essentially have a composite panel of 6mm plywood, 15mm foam, 6mm plywood. Should be OK for tank warfare, withstanding roadside improvised explosive devices, landing helicopters on, etc.