All the photos for this build can be found in my PhotoBucket Album at http://s1101.photobucket.com/albums/g42 ... ?start=all. Just a few have been added to these posts.
If you have seen my previous attempt at a camper lid for my ute viewtopic.php?f=134&t=105324 you will know all the requirements I had and the positives and negatives of that experience. It's what brought me to design and make this current camper.
Prelude – RIP Camper Lid Ver 1.0
The first thing I did was tear apart the old lid to see what a few years worth of offroad abuse and living outside full time did to it. It wasn't pretty. There was water seepage and rotting had started and all the galvanised exterior wood screws has started rusting. The construction adhesive I used came apart fairly easily on all the joints with only some laminations hanging on and breaking with a very loud pop!! All the joints failed at the glue and not the plywood which is the sign of a glue not designed for building a camper with. The only real positive was the self adhesive foam seal used around the joint between the lid and the tub. It was in excellent condition and didn't let in any water after all those vibrations and weather.
So that definitely put that camper experiment to rest as there was no rebuilding it. It did us well for a while but time to move on to bigger and better things.
Stage One - Research
Because I wanted to something that would be waterproof and dust proof I first thought of just enlarging a ute tool box to my dimensions and fitting it out inside with drawers etc. I couldn't understand why all the slide-ons I had seen had steel frames with either steel sheet or alloy sheet attached. Surely a 3mm checker plate alloy box would be strong enough. No!!! Further research showed many people had thought the same and how many alloy tool boxes had cracked after thousands of kilometres of corrugations in the outback. A steel box wasn't going to happen because it would weigh more than my truck and a framed box wouldn't work because I would just lose too much space on the inside (remember I have a tub, not a tray). What to do...
My search took me to exotic materials way out of my price range and back again before finally landing on all the hundreds of wooden boat building websites, teardrop camper websites and expedition trailer websites. These taught me the wonders of epoxy glues, waterproofing and encapsulation ideas. Building methods utilising lamination, stitch and glue and fibreglassing to easily build things strong, light and tough. I had my building method and I could do it myself. If it was good enough for a T-Van it was good enough for me!!!
Stage Two - Testing
So I read and read and read but I still couldn't get away from the idea of “12mm ply with screws holding it together” so I needed to do some tests. I got a sample epoxy kit from BoteCote (great Aussie company in QLD) and some bits of ply to play with and away I went. With the exception of boats, most wooden camper and teardrop builds use a frame but I wanted to build a torsion box slide-on design so I needed to test simple butt joints.
First I glued and screwed three 12mm ply dado'ed butt joints with PVA glue (white glue), PU glue (yellow polyurethane) and epoxy mixed to a glue, waited a couple of days, removed the screws and broke the joints with the following results.
- 1. The PVA glue was like tearing paper - very easy.
2. The PU glue was tougher but still broke at the glue joint. It fills the gaps well but only with foam which has no strength.
3. The epoxy glue took a bit more force to break than the PU but this time the ply was the weakest link instead of the glue joint. All the gaps were filled well and it pulled the ply apart. Perfect.
Next I made another joint out of 12mm ply and epoxied and screwed the corner. When dry I removed the screws and filleted the inside of the joint with a thickened mix of epoxy and filler. This adds enormously to the strength of the joint and provides a radius for the fibreglass tape to fit around. I also routered the outside edge and then laminated on some fibreglass tape inside and out. The result is a corner joint I cannot break!!! I've clamped it to a bench and hauled on it, hit it was a hammer, hit with a 4lb hammer and jumped on with my 80kgs. Nothing, Nada, Bubkiss!!! It is one hugely strong joint!!!
Then I thought “they build kayaks and racing dingies out of 4mm ply” so I couldn't see why a camper needed to be out of 12mm. So I repeated the test with 9mm ply and this time only fibreglassed the outside joint. The result was exactly the same. One hugely strong joint I still haven't broken!!!
The last test was durability. I painted 9mm ply with fibreglass matt and epoxy on one piece and just epoxy only on the other piece. I want to find out how much the epoxy only and the epoxy with fibreglass strengthened the ply and what impact resistance it had. When clamped to a bench it was easy to snap a piece of ply with no epoxy at all but it took my full weight to break the one coated in epoxy only. But I had to stand on the piece with fibreglass in it to break that!!! I then hit the remains with a hammer to test impact resistance, twice flat and twice with the edge of the hammer. The epoxy only piece dented with a loud pop and the epoxy cracked like plastic (which it is). The piece with the fibreglass barely dented when hit with the corner of the hammer and I can't find where I hit it with the flat!!! It added a lot of impact and flexibility strength overall.
The end result of all this is a easy build process that should be light and strong. So the plan is -
- 1. The camper to be built with a mixture of 12mm and 9mm exterior grade ply.
2. Epoxy glue all corners. Clamp screws to be removed afterwards.
3. Fillet all inside corner joints.
4. Coat interior with penetrating epoxy for waterproofness.
5. Fibreglass all exterior surfaces and joints for waterproofness and strength.
6. Paint exterior.