Wall and Floor Attachment to Trailer

[Campin' Texan]

I posted this on the general construction forum, but wanted some offroader's opinions. My tear won't be climbing any mountains, but it will definitely spend a lot of time on the backroads of the west Texas desert. As well as some time on pavement.

I have a 5x10 trailer that is currently being welded together. I'm getting my plans together to attach the floor and walls to the trailer. I've seen this illustration on the different methods of attachment to the frame:



I'm considering modifying the Lap Joint. What would be the issue of attaching the wall directly to the metal trailer frame and leaving out a 2x2 frame? Like this:



Would I have any problems using self-tapping screws and them pulling through 3/4 plywood walls on rough roads? I don't want them to eventually work through.


Thanks for any input.

[Socal Tom]

I don't see an issue with bolting to the frame, but I think sheet metal screws will ultimately fail for a couple of reasons. First, the entire weight of the sides and top will be held up by those little screws as you bounce through wash board roads. This will cause them to bend down and possibly pull out of the frame. If the frame is heavier than sheet metal, they probably won't bite very well anyhow. ( Don't forget the wood weighs about 75# per sheet of 3/4 plywood)
2) They will rust, or the frame will rust and weaken the hold they have.

Now, if you drill through the frame and use 5/16 bolts with locking nuts on the underside, and use something on the outside like fender washers, or some aluminum trim acting like a washer, then you would have a very stout design IMO. Putting some silicon under the washer will help keep water from getting inside the plywood where you drill through.
Tom

[Campin' Texan]

After doing some more thinking, I think I'm gonna go with this:



I hadn't considered in my other design the fact that the screws would also be holding up the weight of not just the walls, but the roof and etc. This new design should give me a lot more support. The weight of everything can rest on the trailer frame, and I will gain some inside height as well. I'll bolt the floor through the frame and sink the bolts down flush with the floor surface. Then I can screw the walls into the 2x4 sub-floor.

Any other thoughts or concerns I haven't thought of?

[bc toys]

I like you decision but use lots of screws wood screws not drywall ones least 2'' long

[kludge]

Any other thoughts or concerns I haven't thought of?

Yes, weld in some flat stock or cut square tube in the corners and other strategic locations to bolt your trailer down to the frame. By setting the wall on the frame, and screwing it to the floor, you'll need a place to bolt your floor to the frame.

This has the added advantage of being able to put on/take off the camper/tear when needed to make building/painting easier or to repair trail damage.

My thought is, when I get around to doing my tiny camper, is that I will be able to take the box off the frame and have truck bed liner sprayed on the floor and a little up the sides a few inches, and to repurpose the trailer for cargo mode when needed. I need a cargo trailer more than a tiny camper, and I don't have room to store two.

[M C Toyer]

Yes, weld in some flat stock or cut square tube in the corners and other strategic locations to bolt your trailer down to the frame. By setting the wall on the frame, and screwing it to the floor, you'll need a place to bolt your floor to the frame.

I was thinking of almost the exact same type of mounting plate on the trailer frame and a matching piece built into to the floor with a nut welded on. That way you wouldn't have the head of the bolt exposed within the trailer or hidden within the wall or be concerned the head would pull through the floor.



M C