Question about my frame and floor

[23Sojourney45]

Hey guys, the frame has been built as well as the floor. The floor is 1/4 birch on the bottom, 1x2 frame, 3/4 insulation in the voids, 1/4 birch on top. The trailer is a 5 x 8 steel frame with two metal crossmembers 2 ft from the back and 2 ft from the front. There is no cross member in the middle, obviously the axle is under that area. Since its a 5x8, the 4x8 plywood was cut so the plywood would measure 4x5 and fit on the frame. The two 4x5 pieces are joined in the middle with a 1x3 along with the other parts of the wood frame. Basically, the whole floor system consists of 2 1/4" 4x5 pieces of plywood, 1x2 frame, 3/4 insulation in the voids, and 2 1/4" 4x5 pieces for the top.

Ive read and asked about the floor thickness and I went with it. Its plenty strong but paranoia came in to say hello. Is it o.k to NOT have a metal crossmember in the middle? I figure the torsion affect will take place and the middle is supported by a 1x3 board attached using PL3. I know that some of you have had experience with this setup but I completely forgot to ask about the middle metal crossmember. Thanks in advance.

[Pmullen503]

If the plywood is well adhered to the internal bracing, you'll be fine. It may flex a bit if you were kneeling in the center of the unsupported area. But mostly the weight will be spread out in use.

Before the roof is on, you can test it by standing in that area. Give the glue a good week or two to fully cure.

Worst case, you could bolt a beam to the underside of the floor to stiffen it up.

[23Sojourney45]

If the plywood is well adhered to the internal bracing, you'll be fine. It may flex a bit if you were kneeling in the center of the unsupported area. But mostly the weight will be spread out in use.

Before the roof is on, you can test it by standing in that area. Give the glue a good week or two to fully cure.

Worst case, you could bolt a beam to the underside of the floor to stiffen it up.

Pmullen, yeh, it flexes a little, my wife and I layed on it to see how it would feel and the weight dispersed, wasn't causing a grand canyon effect or anything. I guess its normal to flex a little. I didn't want to build the whole thing only to have the middle crack out on me. Granted, I put the top 1/4 plywood on top today, didn't glue it, just to see how it would feel to lay on it like I said earlier, felt a little flex. I can imagine that if I glued the top on with PL it wouldn't flex as much. Also, with a mattress on top it may help even more. Worse case, I COULD bolt a beam which I'm hoping not to or else I would be kicking myself for not having the guy weld on one for me when he built the trailer.

[QueticoBill]

Is the foam glued to the ply top and bottom? Glueing foam to ply forms a very strong "beam".

[Pmullen503]

You definitely want the top and bottom ply securely attached to the middle layer. Gluing the foam layer helps too, because of the large surface area.

[23Sojourney45]

Is the foam glued to the ply top and bottom? Glueing foam to ply forms a very strong "beam".

As of today, the only thing glued to the 1x2 frame is the bottom birch ply. The EPS foam is just placed in the voids, no glue or any adhesive. I didn't know if PL 3x premium would have any effect on the foam such as warping or melting. The top ply isn't glued just yet, still cutting the final dimensions of the top. So, what you're saying is, glue the frame to the bottom and top ply AS WELL as glue the 3/4 EPS foam to the bottom and top ply as well??

[23Sojourney45]

You definitely want the top and bottom ply securely attached to the middle layer. Gluing the foam layer helps too, because of the large surface area.

I was on the fence with glueing the 3/4 EPS foam with PL 3x premium, some have said that they didn't glue it. But, it seems that the majority of you guys glue it??

[Pmullen503]

Gorilla glue will safely glue foam. You need very little, it expands as it cures. Squirt a little in the foam cavity and spread, then scrape it off with an old credit card (playing cards work well too.) The little film that is left is enough.

Spritz it with water and put the foam back into the cavity. Weight it down with whatever you have. The white (CLEAR) GG sets in less than an hour, the brown takes a couple hours.

You'll probably want to use the brown GG on for the top for the longer working time.

[QueticoBill]

In simple terms, the foam is the web and the ply are the plates, just like an "I" beam.

[KCStudly]

I would use a non-expanding glue. In my part of the world summer humidity causes expanding glues to react too much.

Epoxy would be best because it doesn't need moisture or air to cure. Perhaps thickened slightly to better grab the texture of the roughed up foam and fill any slight voids in fitment.

TB2 or 3 would be easiest and least expensive, but won't cure well do to lack of air.

The PL300, intended for foam, absolutely needs air and would not be a good choice. Also, it has a thick consistency and doesn't flow out well when squeezed, even when applied with a notched trowel (which also hinders air reaching the middle).

Based on my experience, I would not recommend the 3M green contact adhesive. It just didn't work well for me. In hind sight I would have used epoxy.

The foam doesn't have super tight tolerance on its thickness and might stick up some after gluing into the wooden frame and first side of ply. Definitely level this with a long board or other technique so that the second ply skin lays evenly on foam and frame. Don't assume that the foam will compress under weight or clamps, it won't; there's just too much surface area of foam and it does a good job of resisting compression in this scenario.

[Pmullen503]

...... Definitely level this with a long board or other technique so that the second ply skin lays evenly on foam and frame. Don't assume that the foam will compress under weight or clamps, it won't; there's just too much surface area of foam and it does a good job of resisting compression in this scenario.

Good tip regardless of the glue you use.

[23Sojourney45]

Gorilla glue will safely glue foam. You need very little, it expands as it cures. Squirt a little in the foam cavity and spread, then scrape it off with an old credit card (playing cards work well too.) The little film that is left is enough.

Spritz it with water and put the foam back into the cavity. Weight it down with whatever you have. The white (CLEAR) GG sets in less than an hour, the brown takes a couple hours.

You'll probably want to use the brown GG on for the top for the longer working time.

P, I've used gorilla glue before to glue some odds and ends but nothing to this extent. Squirt a little and spread? For example, 12" x 12" square cavity, spread GG like paint in the cavity? I was thinking of putting a few glue "dots" and just putting the insulation on the top hoping that it will spread but that might not be the way to do it.

[23Sojourney45]

In simple terms, the foam is the web and the ply are the plates, just like an "I" beam.

Quetico, I guess glue-ing the foam will make it less "bendy"?, I didn't think of it that way. Some of the videos and DIY that I've seen didn't glue the insulation at all just in case they wanted to do something else with the floor frame in the future.

[23Sojourney45]

I would use a non-expanding glue. In my part of the world summer humidity causes expanding glues to react too much.

Epoxy would be best because it doesn't need moisture or air to cure. Perhaps thickened slightly to better grab the texture of the roughed up foam and fill any slight voids in fitment.

TB2 or 3 would be easiest and least expensive, but won't cure well do to lack of air.

The PL300, intended for foam, absolutely needs air and would not be a good choice. Also, it has a thick consistency and doesn't flow out well when squeezed, even when applied with a notched trowel (which also hinders air reaching the middle).

Based on my experience, I would not recommend the 3M green contact adhesive. It just didn't work well for me. In hind sight I would have used epoxy.

The foam doesn't have super tight tolerance on its thickness and might stick up some after gluing into the wooden frame and first side of ply. Definitely level this with a long board or other technique so that the second ply skin lays evenly on foam and frame. Don't assume that the foam will compress under weight or clamps, it won't; there's just too much surface area of foam and it does a good job of resisting compression in this scenario.

KC, good point about glue under the foam and it not leveling out. I was literally going to just use a little PL premium under the foam and flattening it out by pressing on it and with the weight of the top plywood. I guess that may not be a good idea eh?

[Pmullen503]

P, I've used gorilla glue before to glue some odds and ends but nothing to this extent. Squirt a little and spread? For example, 12" x 12" square cavity, spread GG like paint in the cavity? I was thinking of putting a few glue "dots" and just putting the insulation on the top hoping that it will spread but that might not be the way to do it.

Putting down dots of glue is actually a good way to meter out the glue. But still use card to spread out the dots. And do spritz with water to make sure the glue cures.

The wood framing in your floor will provide most of the strength, but gluing the foam will make the floor stiffer.

This style of floor has been used alot (including in my now 10 year old trailer), you'll be fine.