That floor to wall join ...

[IASCOTT]

If I were building a foamie my wall to floor attachment would be is this. I would either inset a piece of quarter inch plywood along the the length of the floor attachment on the inside or skin the whole inside with quarter inch birch. Then on the outside I would also inset a half inch thick piece of wood the whole length of the floor attachment area. All glued in with gorilla glue this would spread the clamping pressure over a wider area of the foam .

Scott

[Wobbly Wheels]

FWIW, this is how I plan on doing my floor-wall joint. It will be sheathed in glass on the outside and tabbed corners on the inside.

It's also my first shot at figuring out SketchUp.
Is that a good drawing program for occasional use ?
Since I'm at the start of the learning curve, it'll be easier to switch now...

[GPW]

W2, Nice drawing !!!

[oz97tj]

Nice drawing, but I'm not sure the foam would be a good support. You are putting the walls into compression, but the foam lip is all that is holding the walls up which I could see breaking fairly easily.

[Wobbly Wheels]

Thanks, GPW


Breaking how, oz ?

The foam is really just acting as a mold for the glass. That joint will be tabbed inside and out and sheathed on the outside over the tabbing. When it's done, it will be a monocoque structure with all the strength and rigidity that suggests. Unless I've overlooked something ?

EDIT: I think I know what you mean, but the 'lip' is just a chamfered ring to make sure that the roof drops down squarely and 'locks' into its recess to transmit highway loads through the whole shell and mitigate the effect of the gap in the shell from the roof cutout.

[swampjeep]

In joints its all to do with area and having no movement on any right angle joint. Bonds with large surface areas are more difficult to break.

Titebond II has amazing strength when used on materials its designed for and remember foam is not one of those listed.
...

wouldn't the "joint" you keep talking about actually be held together by the cloth to wood, where it wraps around the underside of the trailer? the cloth is pourous, and the glue should bond the cloth to wood with "amazing strength" then... right?

[starleen2]

Nice

[oz97tj]

Thanks, GPW


Breaking how, oz ?

The foam is really just acting as a mold for the glass. That joint will be tabbed inside and out and sheathed on the outside over the tabbing. When it's done, it will be a monocoque structure with all the strength and rigidity that suggests. Unless I've overlooked something ?

EDIT: I think I know what you mean, but the 'lip' is just a chamfered ring to make sure that the roof drops down squarely and 'locks' into its recess to transmit highway loads through the whole shell and mitigate the effect of the gap in the shell from the roof cutout.

I guess I missed the part about glassing it. And yes I'm talking about the lip that is routered into the floor for the wall to sit on.

Even still, and keep in mind I'm no expert, I'd want something stronger than the foam to hold it up. Foam is fairly easy to break, and the weight of the walls and the roof (and anything attached to it) will ultimately be resting on that edge.

On the other hand, until now, I never considered what the frame will be underneath. For some reason I was thinking it won't be supported directly underneath the wall and was thinking it'll flex the foam on the floor until it breaks. I'm kind of thinking you'll likely have a frame rail underneath though so this is a non-issue.

[Wobbly Wheels]

Gotcha, oz - I can see it would clearly be a probably if the joint was cantilevered outboard of the frame rails. My trailer frame is a bit of a different beast: it's like a boat trailer with two rails rather than a grid for the deck, so a failure there is certainly possible between that joint and the rail.

I haven't looked into how to frame the floor yet, but I've assumed it'll be something like a series of transverse 1X2s with foam between, a ply panel on the inside (top) and glass and undercoating underneath (prob Rhino liner or equiv). Regardless, I'll definitely need to make sure the floor is framed well, so thanks for bringing it up. I could use a sheet of 3/4 ply if it weren't for the weight...

I'm going to start a build thread pretty soon after seeing GPW's off-frame build. Mine's a bit bigger, but I should be able to build it the same way and keep using the tent trailer through the summer.

[Conedodger]

In joints its all to do with area and having no movement on any right angle joint. Bonds with large surface areas are more difficult to break.

Titebond II has amazing strength when used on materials its designed for and remember foam is not one of those listed.
...

wouldn't the "joint" you keep talking about actually be held together by the cloth to wood, where it wraps around the underside of the trailer? the cloth is pourous, and the glue should bond the cloth to wood with "amazing strength" then... right?

TB2 sticking wood to wood, the wood would break before the glue,

Below the join of the wall to floor we have cloth stuck to floor and above the join we have cloth stuck to foam. The join I am talking about is between them. Along the join all we have is cloth and TB2 and even if its for a few thousands of an inch, its basically a bit of cloth and if it fails there is nothing.

The cloth will be stuck to the wood and the cloth may still be stuck to the foam and when it goes (if it ever does) you would hear that sound we all dread, a bit like when you split you pant from front tp back bending over.

Dont forget we have a join of bottom of the wall onto the floor but that does not have a lot of area and is TB2 to foam unless you are using another glue.

[GPW]

Just FYI , we're using gorilla Glue for all the foam to foam , and foam to floor (wood) joins...

[oz97tj]

Gotcha, oz - I can see it would clearly be a probably if the joint was cantilevered outboard of the frame rails. My trailer frame is a bit of a different beast: it's like a boat trailer with two rails rather than a grid for the deck, so a failure there is certainly possible between that joint and the rail.

I haven't looked into how to frame the floor yet, but I've assumed it'll be something like a series of transverse 1X2s with foam between, a ply panel on the inside (top) and glass and undercoating underneath (prob Rhino liner or equiv). Regardless, I'll definitely need to make sure the floor is framed well, so thanks for bringing it up. I could use a sheet of 3/4 ply if it weren't for the weight...

I'm going to start a build thread pretty soon after seeing GPW's off-frame build. Mine's a bit bigger, but I should be able to build it the same way and keep using the tent trailer through the summer.

What sort of weight goal are you hopin for. I have a 5x8 offroad tear. Uilt out of all 3/4 ply with a heavy frame a large tired and im still around 1500 lbs. I don't think a 3/4 ply floor will really hurt you too much. You're only really talkig about 40 lbs for a 4x8 sheet. Then again, a basic ladder style frame should give you enough support, but with a foam floor you will need more crossbracing. Even wit lots of crossbracing, id still be curious about flex in the floor when you're in there crawling around. Might be worth going solid wood floor anyway?

In the end, your weight savings will be in the walls. Not to mention, a trailer that's too light will bounce off the ground over every bump.

[eaglesdare]

who is building the floor out of foam? did i miss that part?

i know i probably have thought about it.

[Wobbly Wheels]

Rather than shooting for a particular weight, I'm trying to avoid the inevitable weight creep right from the start. I'm looking at everything to see if I can make it lighter and still keep it as strong as it needs to be.
If it's harder to do, then so be it....IF it will work.

For example - I don't see the need on my build for a 3/4 ply floor that's going to be under cabinets mostly...that's why I'm addressing the structural issues in the framing.
I'm going to have my wife and I, a shepherd and a retriever, a cooler of food and a cooler of beer in a 2wd 4 cyl Ranger....and a 9' boat to top it off.
With the trolling motor, trailer batteries, boat batteries, & a water tank in the trailer behind it, every pound counts.

I know the next question but I can't really justify getting a bigger truck just to pull it with when my Ranger covers everything else I need and is better on gas.
That's for the next build after we use this one enough to justify replacing the truck. Besides, I only have one parking spot.

I agree that the trailer will bounce more if it's light, but it won't be light once it's loaded, that's why I need to get the layout right. I also want to make it separate from the trailer's frame (like GPW's) so it needs to be light enough to do that empty. Then I'll have to wheel it around back on a dolly (the 'one parking spot thing' again)

So yeah eagles, that would be me that's thinking about a foam sandwich floor.
Well, as much foam as I can get away with anyway....

[GPW]

W2, just thinking , a foam sandwich with 1/4" ply on each side would probably be strong enough , but still 1/2" of plywood and then the foam glue ... probably wouldn't save any weight that way ... 3/4' ply floor has worked well so far for so many ...