What next .....

[Shoebone]

Hi guys,
I've been a member of this forum for some time now, got half way through reading the big thrifty thread and have checked out many builds, I know exactly what I want ... 'Classic' teardrop shape in foam built on a 8 x 4 trailer and as light as practically possible. All the plans are in my head .... and subject to change dependent on beer consumption. er, anyway, I suddenly realized I don't know where to start so I thought I would start with the floor and build upwards. Yesterday was a great day ... I finalized trailer electrics and tow vehicle receiver, everything works, I went to Lowe's and bought five sheets of 2" foam and two sheets of 1/4 inch plywood. I was going to sandwich one sheet of foam with the two sheets of plywood and call it a floor. Everything I read about foamies ... all that information ... has suddenly deserted my brain. looking for an answer using the search function brings up more questions than answers, asking you guys gives me the most current thinking ... So, is the floor sandwich a good idea ... it feels heavy, could i get away with thinner plywood, do I even need plywood, I will be doing PMF everywhere else. If I use the plywood, which adhesive should I use. Your thoughts please, Thanks

[Shoebone]

experimenting with a photo .. a trailer with foam sheets on it. Bet you never seen anything like this before ...

[dancam]

Others can help you more than me, but what do you have for braces on the trailer frame widthwise? What size are they and what spacing? That makes a big difference in what you NEED for strength in the floor. And do you need rigidity in the floor to keep your frame from bending over bumps or is the frsme able to support the teardrop weight?

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[Don L.]

Congrats on your new project!

I saw your photo and wondered about the foam, it looks white which is what expanded foam board looks like. Is it or is it XPS (extruded foam)? There is a big difference in strength. You may know that already. If so just pay no attention to me.

Looking forward to seeing your trailer!

[pchast]

How are you going to bolt the cabin to the trailer? You will want to install
crush blocking where you intend to do so before covering the foam with your
sandwich.

The sandwich is a good idea. Just make sure to scuff sand your foam and/or
wipe it down with alcohol/solvent to remove mold release and oil before
gluing. A thin film of TB II worked for me.

Use a brayer to roll it out thin enough for the ply to soak it up and leave it
weighted for a few days drying.

PS
I would cut back the top plywood to allow your sides to bond foam to foam.
JMHO

[amandacreiglow]

I did a sandwich floor and I like how stiff it is, for sure. Also really like that it'll be insulated beneath me (although I know the floor is the least important part of the insulation equation). But I was unhappy with how well the gladden gripper held, even though I had it weighted for days and days, the edges still came up around the corners of I pulled at them. Felt I needed to add some Alex plus around those areas on assembly day to hopefully mitigate that issue. That said, the sandwich will be held together by the canvas skin just as much as everything else, and isn't likely, I don't think, to suffer too much of the direction of force that it's vulnerable to...

Haven't finished mine yet, so I can't offer more than that. But for sure don't use gripper if you go that way. :-)


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[ghcoe]

Do away with the beaded foam and get the XPS. It is more expensive, but I feel a much better product for building a foamie with.

A sandwiched floor is a strong structure and well insulated, but keep in mind that you will be adding 2 1/2 inches of height to the overall structure and almost 60lbs to the overall weight than if you just go with a single sheet of OSB/ply. In my opinion the 4' wide body already looks a bit tall from the rear without adding a extra 2" to it. If you want insulation in the floor you can cut pieces of insulation and glue it under the floor once the body is attached to the trailer frame.

As far as gluing you can read through my glue tests thread http://tnttt.com/viewtopic.php?f=55&t=69308 . Of course there is the standard foamie glues that have been proven to work, Great Stuff and Gorilla Glue. You can do your own tests to see what works best for you.

[Shoebone]

Thanks for all of your constructive comments, I'm glad I asked the question. My foam is XPS so that's good, more trailer bracing and crush blocking are two things I hadn't considered and yet they are so obvious now you mention them, this forum is the best, Thanks again

[dancam]

Thanks for all of your constructive comments, I'm glad I asked the question. My foam is XPS so that's good, more trailer bracing and crush blocking are two things I hadn't considered and yet they are so obvious now you mention them, this forum is the best, Thanks again

I hadnt thought of crush blocking either in this thread i asked about what glue to use for bonding large pieces of foam to plywood. http://tnttt.com/viewtopic.php?t=68876
I think gorilla glue would work best if you could weight it down enough but tb2 worked for that guy and it appears so far that it worked for me.
With trailer bracing you may have enough, i cant see your trailer so its hard to say. Mine was poorly built and i removed 337 pounds of metal and wood from the frame before starting. So mine didnt have a lot of its own strength. But its 5x10. I only used 3/8 ply for the floor. I had enough support widthwise that the floor doesnt move that way, but the frame wasnt very strong down the length. If i picked one side up a foot and dropped it (on the tire) the back would bounce up and down a lot compared to the middle...
Lots of different ways you can do the floor. Keep in mind what you need to attach to it as far as walls, cabinets and furnature. Maybe 1/8th ply on the bottom, 1.5in foam and 3/8 ply on the top? Glued with tb2 or tb3 thinned down a little for more work time and the bottom wood sealed with 'the mix' and then thin plastic glued to it. To keep rocks from chipping it. We can buy 4x8 sheets of plastic like this for $15 CAD.
I would glue that to the bottom if i did a trailer again. I glued canvass to my plywood, painted it and put rockgaurd on that, but i think the plastic would be better.


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[GPW]

Here’s some ideas … https://www.youtube.com/watch?v=irAcBNe69zo&t=5s Interesting use of wood and Foam …

[amandacreiglow]

A sandwiched floor is a strong structure and well insulated, but keep in mind that you will be adding 2 1/2 inches of height to the overall structure and almost 60lbs to the overall weight than if you just go with a single sheet of OSB/ply.

Agreed on the height addition -- I actually wanted this, for height/hatch/door reasons, but yeah, it's a concern if you don't want that height. Don't think it adds that much to the weight, though. The floor is 50-60lbs with 1/4 ply on top and bottom, yes, but without the sandwich method, most people go with 1/2 ply, which is nearly as heavy. You're really only looking at an addition of 10-15 pounds, I would think.


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[ghcoe]

A sandwiched floor is a strong structure and well insulated, but keep in mind that you will be adding 2 1/2 inches of height to the overall structure and almost 60lbs to the overall weight than if you just go with a single sheet of OSB/ply.

Agreed on the height addition -- I actually wanted this, for height/hatch/door reasons, but yeah, it's a concern if you don't want that height. Don't think it adds that much to the weight, though. The floor is 50-60lbs with 1/4 ply on top and bottom, yes, but without the sandwich method, most people go with 1/2 ply, which is nearly as heavy. You're really only looking at an addition of 10-15 pounds, I would think.

Yes, I forgot you could go with the thinner plys with the sandwich method. I was thinking two 1/2 sheets which weigh about 48lbs each.

[John61CT]

I just hate wood for flooring, too heavy, ends up wet and stinky.

For my ground-up custom build, I'm thinking floor crossmember /beams spaced at 18" centers, minimum tube profile but heavier gauge to the rear near the wheels / suspension (likely Timbren or Flexiride), lighter ones forward where the A-frame supports, but of course everything lining up at the top level of the deck.

Done so the underframe on its own is sound, no extra strengthening from a ply floor needed for lateral and twisting / torsion strength. So, very strong load-bearing floor beams, double purpose with trailer frame strength.

Then these 18" X 36" high-density greenhouse bench / flooring panels, polypropylene grid, super-light but very strong when supported at each edge.

http://www.greenhousemegastore.com/prod ... p-material

Layers from the bottom: a thin insulating layer stuck to /sealing below the grid, followed by the grid+airspace, then Reflectix pointed down, then a 1/2" or maybe 1" foam layer, then floor covering.

Or maybe fill the grid with expanding foam, need to research cost on that.

But I don't think it'd need anything too strong below to shield from road damage, little chips and dents in plastic are NP, or if one panel breaks, cheap and easy to replace.

Feedback welcome.

[dancam]

Interesting idea.
The reflectex im familiar with is fairly soft, 3/8 thick or so and comes in a roll, is that what your thinking of?
Im not sure what you would be using as a floor covering but it would have to be reasonably tough. If you are 200 pounds and you put all your weight on one heel thats like 75psi. If you sit on a chair with skinny legs thats 50-100 pounds on each skinny leg and your floor covering has to support that. It has to keep any furniture from deflecting the foam really.

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[aggie79]

I just hate wood for flooring, too heavy, ends up wet and stinky.

That's a broad generalization that in many if not most cases is not true.

My 6mm ply, 3/4 poplar framing and insulation, and 6mm ply "sandwich" floor is light. The outside ply is sealed with epoxy and automotive spray undercoating. The top (interior) is not finished or sealed. My floor has never been "stinky" except for some slight short-term initial outgassing of formaldehyde from the insulation and ply glues that dissipated after a month or so. Even when driving for hours in heavy rains, the bottom surface of the floor has very little moisture accumulated from the rain, and the moisture has never found its way to the interior of the floor, at least in the 8 years my teardrop has been in existence.