Floor construction thoughts: 3 specific ?'s

[DogStar]

My floor will be stick framed with plywood skins on both side and foam filled and fully glued.
(appx size 5' x 9+')

1.) I want it to be as light as is reasonable possible, to that end how thin can I get with ply skins?
(I am confident of using a 1/4 inch, but wonder if 1/8 could be strong enough.)

The skins will cover the frame which most likely will be made of 1x3 pine, thinking I could re-mill to an actual 2 inch dimension.
(maybe even 1x2 poplar).
2.) If I go with poplar, do you think my floor sandwich can be made of 1x2's?

3.) For stick building of the floor can I get away with 16" centers, or would it be advisable to use something narrower, say 12" centers?

That's it... for now!
P.S. Still learning Sketch Up 8 and hope to post some design ideas soon.

[Larry C]

Mine is 5X8 with 1" thick lumber, and foam. Skinned with 1/8" Door skin on the bottom and 1/8" Russian Birch on top. All surfaces coated with epoxy, framing and skins glued with thickened epoxy. Outside skins glassed with a single layer of 3oz.. The addition of the thin glass dramatically stiffened the whole torsion box. Also the 1/8" top skin with glass passed the knee test.


viewtopic.php?f=50&t=35852&start=15

Larry C

[Wolfgang92025]

Eric,

I used 1/4" on top and 1/8" on bottom with 1/2" x 2" framing.

If I do it again, I would try using 1/8" on both the top and bottom. Remember, the mattress will distribute the weight over a much larger foot print.

[DogStar]

Great build Larry,
Studying it now, giving me lots of input.
I am not going super light so I can see how I can change things up,
but the information is priceless

Mine is 5X8 with 1" thick lumber, and foam. Skinned with 1/8" Door skin on the bottom and 1/8" Russian Birch on top. All surfaces coated with epoxy, framing and skins glued with thickened epoxy. Outside skins glassed with a single layer of 3oz.. The addition of the thin glass dramatically stiffened the whole torsion box. Also the 1/8" top skin with glass passed the knee test.


viewtopic.php?f=50&t=35852&start=15

Larry C

[DogStar]

Exactly the type of input I was looking for!
So very cool.

Eric,

I used 1/4" on top and 1/8" on bottom with 1/2" x 2" framing.

If I do it again, I would try using 1/8" on both the top and bottom. Remember, the mattress will distribute the weight over a much larger foot print.

[Breytie]

Sorry if I sound a bit stupid, but does the 1x2 go on edge for a 2" thick floor or on the flat for a 1" floor?
Is there much to be gained or lost by either? Except for insulation thickness, that is.

[DogStar]

Seems they can go either way.
There certainly is better structure/stiffness by going on edge and like you mentioned better insulation values.
In my construction I am referring to the floor joist going on edge.

Sorry if I sound a bit stupid, but does the 1x2 go on edge for a 2" thick floor or on the flat for a 1" floor?
Is there much to be gained or lost by either? Except for insulation thickness, that is.

[linuxmanxxx]

I have built 2 of them with 1/8" luan on both sides glued with 3M 30NF water based contact cement about 18" centers resulting in 1" thickness with simple white wood 1x2s from lowes and was able to walk on it after it was installed. The 30nf sticks to the foam like crazy and I added lines of titebond3 on the 1x2s over the 30nf sprayed and it won't come apart and the glue creates the strength more than the 1/8" luan does so all the glass epoxy and so forth is over building and not necessary and a preference thing.

I only flipped the 1x2 vertical on the roof to prevent any sagging and it worked perfectly with double 3/4" foam in between same glue which I applied with HVLP cheap gun from harbor freight. Its green and is lime when wet and darkens when it has flashed and ready for bonding. It's water based so it's not a stinking nasty toxic mess which is a huge plus. Pricey around 120 to 130 a gallon but most campers would be done with a gallon to 1 1/2 gallons. We used aluminum on outside on top of luan with this glue and it stuck very well and on first we used frp and weldwood contact cement which had horrible coverage short flash life and toxic mess of the utmost degree so it wound up being as costly just for the outside skin as the 30nf was for our whole next camper. In the end I could stand and walk on the roof of the camper and very little deflection while doing it so the sandwich is massively strong and the way to go for sure.

[Larry C]

so all the glass epoxy and so forth is over building and not necessary and a preference thing.

I think it all depends on whether you have a full frame under the floor, and the width. In my case the glass and epoxy is certainly not overbuilding. Mine is 5' wide, and I don't have a full perimeter chassis, basically just a tongue. My floor is a major strength component of the build. The addition of glass/epoxy dramatically increased the strength of my 1/8"/ 1"/ 1/8" sandwich panel.

[DogStar]

Fantastic info Steve.
Thanks for the leads, looking into the 3M water based product now!

[jonw]

I have built 2 of them with 1/8" luan on both sides glued with 3M 30NF water based contact cement about 18" centers resulting in 1" thickness with simple white wood 1x2s from lowes and was able to walk on it after it was installed. The 30nf sticks to the foam like crazy and I added lines of titebond3 on the 1x2s over the 30nf sprayed and it won't come apart and the glue creates the strength more than the 1/8" luan does so all the glass epoxy and so forth is over building and not necessary and a preference thing.

I only flipped the 1x2 vertical on the roof to prevent any sagging and it worked perfectly with double 3/4" foam in between same glue which I applied with HVLP cheap gun from harbor freight. Its green and is lime when wet and darkens when it has flashed and ready for bonding. It's water based so it's not a stinking nasty toxic mess which is a huge plus. Pricey around 120 to 130 a gallon but most campers would be done with a gallon to 1 1/2 gallons. We used aluminum on outside on top of luan with this glue and it stuck very well and on first we used frp and weldwood contact cement which had horrible coverage short flash life and toxic mess of the utmost degree so it wound up being as costly just for the outside skin as the 30nf was for our whole next camper. In the end I could stand and walk on the roof of the camper and very little deflection while doing it so the sandwich is massively strong and the way to go for sure.

Excellent information! Will use for my next build. Thanks...

[linuxmanxxx]

I think it all depends on whether you have a full frame under the floor, and the width. In my case the glass and epoxy is certainly not overbuilding. Mine is 5' wide, and I don't have a full perimeter chassis, basically just a tongue. My floor is a major strength component of the build. The addition of glass/epoxy dramatically increased the strength of my 1/8"/ 1"/ 1/8" sandwich panel.

I've just been researching or trying to research what DOT standards are for trailer construction and I can't find anything about whether or not having a coupler without a full frame is legal or not. Of course then you fall under 50 different states DOT rules as well. I've been considering building a unibody type camper but haven't figured if it is fully legal to do this or not. The trailer world is so murky about standards and information as to what is actually legal beyond weight limits and lighting requirements. In your instance the stiffness is definitely needed and could be added by closer centers on 1x2 as well as glassing it.