Foamie with a slide

[mdk]

I'm stymied right now, in terms of building space, so I have been exploring design ideas.

One of the things I've been thinking about is using a slide - about a 12 inch slide out on one side to get everything in it in the size of exterior I'm after.

How would you construct things so as to have a strong slide when the trailer is a box (not a tear) and is constructed of skinned foam? One of the goals here is absolute minimum weight.

The walls / floor / ceiling would be constructed of (depending on location) 1-1/2 or 2 inch foam skinned on both sides by 1/8, 1/4 or 1/2 inch ply. The slide area would ideally keep this construction, but I don't see how you make it strong and prevent flexing. Or perhaps it's not really an issue. I just don't see where the strength would come from, unlike the "box" of the trailer, which is strong due to its shape and distribution of forces.

[Hardryder56]

Not exactly seeing what you are looking for but I think a 12 inch slide out could be supported with heavy duty bottom mounted drawer slide mounts. The number and spacing of the sliders would depend on the over all size of the slide out.
Tom

[GPW]

MDK, perhaps you could do a simple drawing of what you intend ... there’s Always a way of doing it ...once we know what It is ???

[mdk]

I can't draw for squat, and have yet to figure out any of the CAD programs.

But, it shouldn't be too difficult. The design is a 12 foot long, 6 foot wide, 6.5 foot high box (inside dimensions), with a V-shaped nose ADDED to the 6X12 floor plan.

In the back, the last 5 feet in length, by about 4-5 feet high needs to slide out on one side about 12 inches, to create enough room for the bed / dining area.

A couple slides on the bottom seems workable, but it would also seem to need at least 2 more on each side. It would shaped roughly like a very shallow U, on it's side, with the bottom being solid.

The problem is, I can see this thing flexing like a sheet of paper in the wind... Unless the skinned foam is more rigid than it seems it would be to me. And it needs to be very rigid, because it needs to be part of and reinforce the structure of the 'box' itself. Using lots of thick plywood might overcome such, but it adds a LOT of weight.

[GPW]

That shouldn’t be so hard to do..
You know , I never drew a squat either...

[atahoekid]

I think it would be easy enough to skin one wall with thin ply and skin the outside with a skin of 'canvas or other material of choice and it should be plenty stiff. It's amazing what the skin does to the rigidity of the wall

[Hardryder56]

I think you will find that 1 1/2 or 2" foam laminated with a thin plywood on one side and cloth on the other would be very stiff. Even at 5 foot long you would have some framing included that would add to the structural strength. I think if you build the slide out first you would be surprised at how rigid it becomes.
Tom

[mezmo]

Possible approaches:

You could also use a perimeter edge frame on the
"open" end of the slide out of either wood, nominal 1x ?
size [hardwood would be stronger], or aluminum "U"
channel over the foam or tube at the perimeter's edge.
Do this also around the opening's perimeter in the
sidewall for the slide-out.

Think of the slide-out as an inverted drawer, even if it is
shallow in depth, or a 5 sided box. The full-extension type
drawer slides should work fine to locate and move it. Since
it is at the end of the body side, the slides [4 in total, one
located at each corner.] could be attached to the end wall,
or a clete attached to it, and to a flange-wall at the other
side [located on the middle of the trailer body wall] of the
slide-out opening. The flange wall should run floor to ceiling
at 90 degrees to the side wall. That only needs to be as deep
as the slide-out is, but can be deeper if desired. If you don't
want a flange wall, a roof spar at the top, deep enough to take
the top corner's slide, and a similar stub-piece attached
to the floor, at least as long as the slide, at the bottom, would
probably work too at the mid trailer location. The flange wall
would be much stiffer though, by far, and could be incorporated
into, or serve as part of the structure for interior cabinets/closets
etc..

Also, consider using the "mini-SIPS" construction method. It uses
nominal 1x? perimeter frames of wood or square metal tubing
around the panel's outside perimeter and on the interior perimeters
of the openings within the panels with thin ply on both sides of the
foam. This should give the strength you need. See Linuxmanxxx's
posts on that.

Cheers,
Norm/mezmo
of the panels

[KCStudly]

Will the floor of the 12 inch slide out be a stepped on area (or any heavy load) or will it just be there to provide air space above floor level?

If it is a loaded area then you may want to start looking at equipment slides instead of drawer slides; much higher capacities.

5mm or 1/4 inch ply skin laminated to 1-1/2 or 2 inch foam will be very, very strong in a 5 sided box, especially with a 1x3 flange frame surrounding the inner opening (as a slide stop and sealing surface). If you are going to be stepping on the floor of the slide much, you may want to go up to 3/8 nominal, IMO.

having said that, my first impression is that it is an awful lot of work, expense, and risk of leaks for 5 sq ft. Go bigger or not at all, but I suppose we don't have a clear enough idea of your interior arrangement or intended usage to understand that.

[mdk]

I think you will find that 1 1/2 or 2" foam laminated with a thin plywood on one side and cloth on the other would be very stiff. Even at 5 foot long you would have some framing included that would add to the structural strength. I think if you build the slide out first you would be surprised at how rigid it becomes.
Tom

I am intending to skin both inside and outside with thin ply. The outside wood would be thoroughly painted with clear penetrating epoxy, and then likely finished with this: http://www.amazon.com/MFM-Building-Prod ... B0004I0MG0 to provide color, sun protection, water protection, and total sealing of every seam, joint, etc, without any brittleness.

I have no experience with it (skinned foam), however. Perhaps I just misjudge the combination's strength.

[mdk]

Will the floor of the 12 inch slide out be a stepped on area (or any heavy load) or will it just be there to provide air space above floor level?

If it is a loaded area then you may want to start looking at equipment slides instead of drawer slides; much higher capacities.

5mm or 1/4 inch ply skin laminated to 1-1/2 or 2 inch foam will be very, very strong in a 5 sided box, especially with a 1x3 flange frame surrounding the inner opening (as a slide stop and sealing surface. If you are going to be stepping on the floor of the slide much, you may want to go up to 3/8 nominal, IMO.

having said that, my first impression is that it is an awful lot of work, expense, and risk of leaks for 5 sq ft. Go bigger or not at all, but I suppose we don't have a clear enough idea of your interior arrangement or intended usage to understand that.

Oh, well... here's the parameters...

It must be short as possible to have as short of overhang in back and as much ground clearance behind the hitch as possible. My goal is 12 feet. It must be fully self contained, including a shower, bathroom, and a queen size bed. It needs LOTS of ground clearance so that it can handle dirt and gravel roads. I'm going to be using two axles (with brakes) for maximum terrain handling and stability over rougher roads (and not exploding the tires). It's no more than 74 inches wide when travelling, so it can be pulled by my Jeep or pickup, without any mirrors that stick out. Besides, narrowing to 6 feet far more than makes up for the extra height (in terms of square feet of frontal area - aerodynamic drag) needed for rougher terrain. I want a minimum of 50 gallons of water and waste capacity - prefer more.

To get an 80 inch long bed in crossways (queen size), it simply will not fit in 70 inches of inside width. And turning it lengthwise adds 20 inches of length to the trailer. I want it to be very well insulated, so it can handle the occasional cold weather excursion - that's why I want a foamie - insulated well and very low weight.

[KCStudly]

Got it. So the slide out is just a foot well for the bed. Should be very doable.

[GPW]

"I am intending to skin both inside and outside with thin ply.” ..........

[mdk]

"I am intending to skin both inside and outside with thin ply.” ..........

Tell me what's wrong with that idea?

[GPW]

MDK, we’re NOT a big fan of plywood on the outside , having had Many de-lamination and splitting problems in the past .... But if you want to do that , I’d highly recommend putting a light fabric skin (or Fiberglas) on top of that ... that’s proven to really Help ...

Ps. You DID read the entire Thrifty Alternatives thread huh ? (required reading) I know , it’s BIG , but explains most everything and how and why this got started... and assorted other things too ... (which you can skip over)