hybrid foamie micro tiny house

[pchast]

Please test your design in small scale to prove it works.

Screws to hold a foaming urethane while curing could
be a problem.

[woodie72]

Please test your design in small scale to prove it works.

Screws to hold a foaming urethane while curing could
be a problem.

This is a test piece i made. The 'nailers' are routed and epoxied into the foam. The strips planking is epoxied and nailed perpendicular to the 'nailers', creating a lattice inside the foam. After curing nails are removed and toothpicks fill the nail holes in the strip planking. All is sandwiched between fiberglass inside and out. I stood on the test piece, which is only 35mm thick and it didn't deflect one bit. The clamping battens can be screwed through nailers and foam to floor cleats while the polyurethane cures.





The finished trailer will be ridden to location and left there. It will not be used for travelling as such.

[woodie72]

The tongue and groove has no shear strength so just the fibreglass. Perhaps 3 or 4 or more layers of glass and resin would come close to a piece of ply. Stability perpendicular to grain will be iffy because of changes from humidity, especially outside. No tensile strength in t&g. Just pulls apart.

Look at sips. Continous one piece skin. The skin is subject to tension and compression parallel to the panel.

Just like a hollow door with honeycomb, or an I beam or a tji (wood joist) all the stress is in the flanges or skin.

would this work ? Fiberglass the foam just like a foamie and then glue 3/8 nailer strips on top of the fiberglass and nail the strips treated with the mix onto the nailers. Easy to repair when needed

Or would gluing the strips directly to the fiberglass be better ?

Did i mention i hate plywood well apart from marine ply that is, which is ridiculously expensive here

[QueticoBill]

Woodie
I think my concern is what appears to be a wall much taller than a tear. Simply, the forces on a member, like a bean, column, or wall, is proportional to the square if the length. So a wall twice as tall needs to be four times as strong.

I appreciate your dislike of plywood, but it does have some great structural attributes.

1/4" thick strips let into both sides would be stronger than 1/2" on one side, but not the way I would go.

I'll try to reread whole thread and see if something else comes to mind.

[woodie72]

Woodie
I think my concern is what appears to be a wall much taller than a tear. Simply, the forces on a member, like a bean, column, or wall, is proportional to the square if the length. So a wall twice as tall needs to be four times as strong.

I appreciate your dislike of plywood, but it does have some great structural attributes.

1/4" thick strips let into both sides would be stronger than 1/2" on one side, but not the way I would go.

I'll try to reread whole thread and see if something else comes to mind.

Thanks for looking into this.

Would for example routing and gluing 1/4 by 2 inch wide plywood strips on both sides of the foam, in such a way as to mimick classic framing with 1 inch lumber be a possible solution, then attach the strips to this 1/4 inch framework and then encapsulate everything in fiberglass, work ?

The easiest i see if to just glass the foam, attach glassed walls to the cleats and the floor with a 4 to 5 inch glass strip going from the underside of the floor up the bottom of the walls, tying walls, cleats and floor together. Tape nailers with epoxy to the glassed walls and attach the wood strips to the nailers ? Doing it this way would give continuous layer fiberglass. I don't see a difference with a classic foamie and canvas sock method apart from the extra nailers on the outside. The gap between the walls and the strips would mean airflow to dry out the strips for example, and extra insulation.

Important to know as well is i don't intend to put any cabinets higher than waist level making the inside feel as spacious as possible, maybe apart some small shelves higher up.

[QueticoBill]

I agree just glassing foam and adding furring and clapboards is a better approach, but I don't know if the basic foam and glass - the furring and claps not adding strength but adding weight - is strong enough for the height you show. Probably thick enough foam and heavy enough fiberglass would work.

Bulkheads and cabinets are often relied on for bracing. I don't know what you have planned or how the framing for a folding bed might brace the walls.

[woodie72]

I agree just glassing foam and adding furring and clapboards is a better approach, but I don't know if the basic foam and glass - the furring and claps not adding strength but adding weight - is strong enough for the height you show. Probably thick enough foam and heavy enough fiberglass would work.

Bulkheads and cabinets are often relied on for bracing. I don't know what you have planned or how the framing for a folding bed might brace the walls.

Well the weight will not be that much. The strips are only about 5mm thick so for the long walls it would add 27 pounds over an area of about 63 sq ft. That is for a full wall, no windows or door. Quick calculation with door and windows brings it down to 21 pounds. Don't see much of an issue there.

As for folding bed.
Thinking of maybe using a hollow core door as base and adding slats suspended in those rubber thingies.
For supports for the bed either small cabinets, maybe 8 inch deep, supporting the head and foot end. Or might just go with some 3 inch posts on the front corners and an 10 deep cabinet at the back, the length of bed platform. In the up position there would be a fold up table that is attached to those the cabinets. Probably best to add a single removable center support.

I have built skin on frame kayaks, and just can't imagine it not being strong enough. I always cruise, 60mph on the highway, even without anything in tow

[QueticoBill]

Well, I was thinking about wind and other lateral loads on the wall. The weight of the gravity load of wall and roof is insignificant.

Maybe someone else here has experience with tall foamie walls and should weigh in.

PS. Formula for force of wind. P = 0.00256 x V2 (thats V squared - I don't know how to superscript in this editor) where P is the pressure in psf and V is wind velocity in mph. For example 70 mph is 12.5 psf.

[woodie72]

Well, I was thinking about wind and other lateral loads on the wall. The weight of the gravity load of wall and roof is insignificant.

Maybe someone else here has experience with tall foamie walls and should weigh in.

PS. Formula for force of wind. P = 0.00256 x V2 (thats V squared - I don't know how to superscript in this editor) where P is the pressure in psf and V is wind velocity in mph. For example 70 mph is 12.5 psf.

Thanks. the only frontal surface exposed is about 17 by 35 inches, the rest is tucked behind the car. And as for driving in 70mph side winds, personally i think it wouldn't be wise to go out on the road in such conditions.

I am going to focus on my other trailer, which will be a runaway style travel trailer, with a partial pop up roof. Again want to go wwith wood stripping glued directly to the foam and glass encapsulating everything. Build up some experience before tackling the larger one. Titebond 2 over here is about as expensive as epoxy, really not much in it.

[QueticoBill]

That will probably work. Just never camp in a windy place.