3/4 plywood walls attachment

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3/4 plywood walls attachment

Postby FBJcreation » Sat Mar 30, 2019 2:52 pm

I am going simple to keep down weight and just doing 3/4 inch walls and floors. I may toss on a 1/4 hardwood laminated layer making the walls and floor more like 1". My thought is to bolt the outer walls (& floor) through trailer frame rather than the floor and glass the interior corner (or use an L bracket) to tie them together. Not going to bother insulating walls or floor. I've spent way many years of wilderness camping and the mattress on the floor will be more than enough insulation even in winter. I'll do an epoxy of the wood in and out to seal, waterproof, and strengthen said walls and floor. Anyway thoughts on this? size of bolts? 3/6"? 1/4"? Did some searching on tnttt and didn't easily find a discussion on this, though is it likely there some place. Thanks all.
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Re: 3/4 plywood walls attachment

Postby edgeau » Sat Mar 30, 2019 5:09 pm

Mine is held on with 3/8th x 2" bolts Image

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Re: 3/4 plywood walls attachment

Postby working on it » Sat Mar 30, 2019 11:30 pm

FBJcreation wrote: 1) I am going simple to keep down weight and just doing 3/4 inch walls and floors.
2) My thought is to bolt the outer walls (& floor) through trailer frame rather than the floor and glass the interior corner (or use an L bracket) to tie them together.
3) Not going to bother insulating walls or floor. I've spent way many years of wilderness camping and the mattress on the floor will be more than enough insulation even in winter.
4) I'll do an epoxy of the wood in and out to seal, waterproof, and strengthen said walls and floor.
5) Anyway thoughts on this? size of bolts? 3/6"? 1/4"? Did some searching on tnttt and didn't easily find a discussion on this, though is it likely there some place. Thanks all.

* Sounds like familiar territory for me, since I also intended to go "simple", by using 3/4" plywood w/no insulation, mainly bolted together, employing steel brackets, PL adhesive, and mostly stainless bolts, washers, & nuts. I did go overboard in using double or triple the amount of adhesive, coatings, lock & hinge hardware, and packing the 4x8 with equipment that's normally carried externally, but integral to my design. Thus, though intended to be simple, it turned out to be complex, and very heavy for its' size.
* 1) 3/4" plywood is very strong, but not lightweight...by using steel angle & corner brackets, and gluing every seam and joint twice, it needs no supporting spars or bracing (though I, in my usual fashion, did use 1/2" oak boards to create inner bracing around the doors, windows, and A/C unit).
* 2) My base floor (1/2" birch plywood) is bolted to the frame using eight 3/8" carriage bolts, then a 1/4" Luan sheet was glued over it (to cover the semi-recessed bolt heads) with TB2, then then entire perimeter of the floor was Tek-screwed down with thirty-eight screws into the tubular steel frame. The walls are simply bolted to the floor using the steel brackets (and PL adhesive, of course...I used 10-12 cartridges during the initial build, and several more since modifications began).
* 3) Since I camp in Texas and Oklahoma, only in Spring thru Fall, it never occurred to me that insulation might be needed, since I provided for both heating and cooling enough...but dealing with condensation without insulation requires that I always have sufficient airflow inside. And I used to use two foam mattresses, sheets, blankets & comforters, but now a simple fold-up mattress and a summer weight or winter weight sleeping bag make it simpler.
* 4) Instead of using epoxy, and/or fiberglass to waterproof the wood on my trailer (I'd never had much luck when using either, before), I opted to use the "mix" (polyurethane/paint thinner) to saturate the plywood (practically plasticizing it) and then use outdoor equipment enamel to provide color & UV protection. Once again, I doubled & tripled the # of coats used, but it was worth the trouble. Any of the three wood-covering methods would work fine.
* 5) As I previously stated, I started out with 3/8" carriage bolts, and also with 1/4"-20 stainless carriage bolts (+ acorn nuts or nylocks, fender washers, too, all stainless...over two hundred $$ worth), and added in specialty theft-resistant bolts, and numerous size and length Spax or Tek screws (where needed). All bolt & screw-holes were sealed with PL (which also makes a fine way to prevent non-locking nuts from backing off).
* Yes, it seems I overdid the strength/weight aspect of what was originally intended to be a sub-1000 lb sleeping trailer for my wife, but became a heavyweight Franken-trailer when I assumed sole ownership of it (she never told me that she was claustrophobic...a sealed 4x8 is a bit too tight for her tastes). good luck with your trailer, and keep it simple.
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Re: 3/4 plywood walls attachment

Postby FBJcreation » Sun Mar 31, 2019 7:05 am

Thanks, for the tips. We are doing 5x10 trailer with a larger 3/16 polycrab "picture/star glazer window'. (3/16 polycarb will cold bend to the radius needed and is at about race car windshield thickness). The 3/4 plywood is heavy but an insulated wall will be too when all said and done, I ran the math and it was surprisingly not that much different. The condensation can be dealt with. Thanks,
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Re: 3/4 plywood walls attachment

Postby FBJcreation » Fri Apr 05, 2019 3:17 pm

Got the trailer (custom 5 x 10 for $350 more the Northern Tools 5x8 and much better build) from the welder, not quite enough room for mounting wall on the side of the frame plus the frame of the trailer is 2x2 square steel tubing which adds some difficulty. Looking at two other options for attaching walls to the floor.

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Any thoughts on these two options? The floor will have a mattress, so carriage bolts should be fine.
Is 1/4' x 1.5"x1.5" aluminum angle too thick, thinner like 1/8"? wider 2"x2"?

I see some of the mfg's use this method for attaching walls to floors. I will start a thread for our build here soon.
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Re: 3/4 plywood walls attachment

Postby troubleScottie » Fri Apr 05, 2019 5:44 pm

Kreg screws along the inside wall. Never did 3/4" plywood to 3/4" plywood, but their charts say that thickness and thinner can be done. Every 6" to 12" with epoxy at the interface, should be pretty strong. You are left with those ugly pockets -- which is probably no worse than the metal angle.

The "L" idea has the issue of the screws will have to be shorter then 3/4" so as to no penetrate the plywood.

Screws/nails into the edge of plywood generally do not hold well for a number of reasons.
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Re: 3/4 plywood walls attachment

Postby FBJcreation » Fri Apr 05, 2019 7:17 pm

If I did option 2 with the wall on trailer I was thinking of log screws to pull tight with epoxy. Then reinforce with with alum L angle at 6 inch punched intervals. Accounting for L thickness and 3/4 ply, then 3/4 inch kreg screws through the alum. and wood. I suppose I could even glass the corners first. All panels will be epoxy coated and exterior seams glasses taped and epoxied. Planning to go with one of the bend liner products for the outside final coating.
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Re: 3/4 plywood walls attachment

Postby les45 » Sat Apr 06, 2019 3:51 am

On my 5X10 weekender (on a 5X8 NT trailer), I ran a 2X4 nailer on both sides and screwed my 3/4" plywood walls to that with 3" deck screws. The 2X4 is simply bolted to the 1/2" plywood deck with a 3/4" lip for the side walls to sit flush on the frame. I did insulate the floor by filling the space with 1.5" foam board and installing a luan floor over that. The front and rear end pieces were actually 2X6 cut at an angle to accommodate the bottom bevel on each end.

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Re: 3/4 plywood walls attachment

Postby FBJcreation » Sat Apr 06, 2019 6:23 am

Thanks for sharing. Your design is similar to what we had in mind, on the front we are planning to add a polycarb picture window too. I like what you did to the corners before adding the walls.
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Re: 3/4 plywood walls attachment

Postby les45 » Sat Apr 06, 2019 6:34 am

FBJcreation wrote:Thanks for sharing. Your design is similar to what we had in mind, on the front we are planning to add a polycarb picture window too. I like what you did to the corners before adding the walls.


If you put a window on the front, especially polycarb, you might want to consider a hinged or removable cover to protect it while towing.
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Re: 3/4 plywood walls attachment

Postby FBJcreation » Sat Apr 06, 2019 10:14 am

Still thinking about to do a cover for the polycarb window, if I did it would be to reduce scratches, not for breakage. Something that would shatter a car or truck windshield will only scratch a polycarb one. They are required on race cars with speed excess of 200mph, blue water boats, skylights, greenhouses, safety glasses and face shields, and other similar applications. Starting at about 1"+ thickness it is bullet resistant depending on the round. I'll most likely use a 3/16 polycar, 1/4 seems an overkill. It does flex some and can have usable cold a bend radius at 1/4 or less thickness. You can get it UV and scratch resistant, even tinted. Lots of mounting options as it can be glued, screwed, or bolted plus drilled, routed, and sawed; like wood, unlike glass or acrylic. Great stuff. It is not used more because it doesn't break like safety glass (so a safety issue in some situations) and does scratch more over time than glass. Some chemicals like DEET will fog it, mostly though it is chemical resistant.
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Re: 3/4 plywood walls attachment

Postby FBJcreation » Thu Apr 11, 2019 2:27 pm

les45, decided to follow your lead on attaching the walls like you did. Looks like the best option overall. Thanks for your suggestions.
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