Newby trailer build

[girvin]

Aloha what a great source of info here. I was a welder/fabricator in my previous career(cyber security now). SO I have fixed a lot of heavy trailers and built a lot of aluminum flatbeds for trucks. Since we have a child now (1month old) I decided to build a square drop for traveling as a family. I am building the poor mans version of a Bruder exp4. So I had a few Q's that spanned different categories but thought I could put them all in one here.

-I am building 2x3x3/16 main frame rails with 2in c channel cross beams and 2x2 outside rails. At 17ft total length and being an off road Baja trailer I beefed it up a bit. I am welding a cabin frame out of 1x1 and attaching ply to that then foam in the gap then ply or frp on the inside. I thought this would be a better overall conection to the frame for rigidity if I should be Making a plywood box and puting it on the frame for some reason please let my know why!

Should I just screw into the metal frame and use pl as an adheasive?

Is it better to use pl on the 2part epoxy primed metal or sand to bare metal? I am worried about corrosion since this is a surf based camper.

is there a cost effective outer skin besides ply or aluminum I am missing?

I really dont want to epoxy 14 pieces of ply top and bottom but I am guessing that is all I can do if using ply?

I was going to use 1/4 in ply on inside an out but was told by my cabinet making buddy I should use 1/2 ply outside and 1/8th inside.

Is monsterlining the whole thing the best way to go for waterproofing the ply after a coat of epoxy or should I just use an oil enamel?

what is the best coating for the ply undercarriage I have heard roofers tar?

Sorry for all the questions my metal will be here fri so I can get started on sat with the frame.

[girvin]

Also I wanted to make the 3 doors out of 1x1 tubing all gullwing style does anyone have a website that sells all the stuff I would need

[noseoil]

Congratulations on the little one, it's a game-changer to be sure.

The frame sounds pretty beefy, you might think about 0.120" instead of 3/16" to save a bit of weight. Also, a lighter gauge 2x4 rail might be better for the 17' long body, but you may play with the numbers to see where you end up. Any good paint system will last, since it's not going swimming in the salt (at least I hope it isn't). That's a pretty big trailer! 1x1 (16 gauge?) will be plenty strong, but is it really necessary? 1x2 battens have been used for many trailer builds with good results over the years. A frame of 1x2's with 1/8" inner & outer plywood skins should hold up well enough if it's glued in place with PL or Titebond adhesive. With a 17' box, weight will be an issue sooner or later, so take a look at how people have built. The Astroliner will be a good build to look at as well (Mike's beautiful build! http://tnttt.com/viewtopic.php?f=50&t=6 ... astroliner ). The trailer "box" is really a torsion member & will help stiffen the frame if it's glued over a fairly light frame.

I used 1/8" for the top & bottom of my deck with good results, but the 1/8" top deck is just for sleeping with a thick mattress. It was a 1x framework with cross pieces located for loading. I did beef up the galley with 2 layers (1/4" deck there, battery, etc) but there have been no problems. I used 2 coats of polyurethane on the top & bottom, then applied some white roof coating to the bottom of the deck. It's easier when you have to crawl around under the trailer to see with the white bottom than with black asphalt emulsion. I figure if it holds up for years in the sun, a little road grime isn't a problem & a car wash will clean it up to looking like new in a few minutes.

Take a look at Tony Latham's #4 for his use of bed liner ( http://tnttt.com/viewtopic.php?f=50&t=71588 ). He did a fiberglass layer on the wood, then rolled it with the liner. You can't miss it when you see what he did & his build journal is really good for details, take a look!

[girvin]

thanks so much for the reply!

The box is 13ft, the trailer will be just under 17 with the hitch. The purpose of welding the 1x1 into the trailer was to make a stronger connection for the whole thing. My other Idea was to build the box separately like a ply and glass boat and through bolt it onto the trailer frame. Do you think this method can hold up to really bad roads in Mexico most of them are dirt? I wont be doing moab with it but I have seen trucks die on bad washboard and potholes.

I have built surfboards and fixed boats most of my life so the glass isn't a problem. I just couldn't figure out if it would be better to have the 1x1 skeleton attached then ply foam ply fiberglassed around that or just a box through bolted.

when epoxing to the frame do you grind away paint where the connection will be or just epoxy to the paint?

Im towing it with a gx470 so I have a v8 but would like to stay under 2500 definitely under 3000 lbs

[girvin]

after thinking about it I might do a boat style build of .5 ply with a .75 frame glassed and epoxied and the gaps filled with ,75 xps foam and interior sheeted in 1/8 or is that overkill? It seems working with 1/4 would be harder.

[GPW]

Girvin , hard to beat boat construction methods ! Just flip it over for a trailer ...

[girvin]

Yeah thats back where I am at. I rebuilt a 42 ft wharram catamaran I think Ill go that route. Any suggestions on how to connect it to the frame?