exterior shell question

[arktrekker]

I have been planning a build for a while now and have reached a point where I am considering materials for the exterior. Basically I am looking at building my own shell onto the back my F350. The plan so far is to go with a metal frame. I had given thought to covering it with a thing plywood, somewhere around 1/4-3/8 thick and then glue on the exterior covering like they use on motorhomes.

Today I was at a friends house and he had just bought a canoe. The previous owner had sprayed the wooden seats with bedliner at one of the places like line-x.

So the gears in my head started turning. Would it be possible to spray the exterior of a custom wood shell with something like this to create a waterproof shell? Any reasons why it would not work?

 

[arktrekker]

I would have thought that the bedliner would only need to adhere to the wood instead of soaking in to provide a watertight seal all around it. I guess if I would need to cover the wood with epoxy I could always get it from one of the places that serves the wooden boat crowd.

I was thinking of going with either a lighter grey or a dk blue which would match the cab. Only problem with the dk blue is that I am afraid it might be a huge heat sink.

 

[DrMacZed]

One other thing to consider when using bed liner over epoxy over ply. The wood expands and contracts differently than the bedliner and can and will cause the bed liner to split over time. I made a box out of ply and sealed it with epoxy and a layer of Fiber glass cloth. I have noticed of late there are some splits and cracks in the bed liner.

 

[arktrekker]

Whatever material the exterior shell is made out of will not end up being the same material that is seen from the interior. I plan on making a metal framework, sheathing it, filling in the gaps with insulation and then adding an interior panel for the interior finishing.

I wish I was more comfortable working with nidacore.

What might be some other suggestions for the exterior?

 

[jeepdreamer]

Just some strange thoughts...

So...
What if you sheathed the frame/plywood with aluminum panels or light gauge steel THEN bed linered (is that a word?) the exterior? No idea how the different mediums would effect each other...hmm. IS there a good answer out there..?

 

[arktrekker]

I have been sitting here this evening working over my plan.

If I were to build my metal frame and cover that in sheet metal which was then covered in bedliner, what gauge of cold roll do you think I could get away with to keep the weight of the shell itself down yet keep it from being too flimsy? The frame itself will be fairly rigid and if I am able to build this the way I have in mind I might possibly be able to use a spray in insulation which in turn should add to the strength of the overall unit.

I am fairly certain that the sheet metal should be able to come in under the weight of the original plywood idea and would allow for some nicer rounded edges. Plus I am way better at working with metal than I am with wood

 

[63tlf8]

So...
What if you sheathed the frame/plywood with aluminum panels or light gauge steel THEN bed linered (is that a word?) the exterior? No idea how the different mediums would effect each other...hmm. IS there a good answer out there..?

Now you're talking. Whilst not a popular option, I used 0.5mm prepainted sheet steel for my MOG camper cladding. Weight wise it comes in well under 2mm Aluminium, is tough enough to be used as roofing material and easy to work. For me though, it requires a different construction technique.

Still use the square tube frame. Apply the interior panels to the frame first using a Polyurethane adhesive, infill the frame with closed cell foam sheet the same thickness as the frame (glued to the lining) and lastly apply the exterior sheet steel gluing to the sheet foam and steel frame using appropriate adhesives. If you have a particular requirement for extreme cold weather you can increase the thickness of the sheet foam and glue battens to the interior of the frame to further reduce the cold bridge. Not everyone camps in the snow so personal circumstances etc etc.

Do you need bed liner? So, allowing we all have different tastes, this is another option to be considered. The finished product looks just like the sheet GRP sides of commercial motor homes so you can achieve a very professional finish with a little care.

Tony

 

[arktrekker]

Why not apply the exterior skin first? I would think if yoiu applied the metal skin first you could spray a sealer/primer to the inside of it to retard any future rusting caused by sweating or other possible moisture penetrations.

If I end up using metal skin I would probably want to glue it as well as add tack welds along the inside. I am a firm believer in overkill

 

[63tlf8]

Why not apply the exterior skin first? I would think if yoiu applied the metal skin first you could spray a sealer/primer to the inside of it to retard any future rusting caused by sweating or other possible moisture penetrations.

If I end up using metal skin I would probably want to glue it as well as add tack welds along the inside. I am a firm believer in overkill

You may do as you wish. I did stress this was my design to my requirements and complete, so any better solutions that I come across later will have missed the boat. If you have an engineering background then you will know that when properly bonded over the surface area, the cladding attachment will be as strong as welding. I'm glad you recognise "overkill" for what it is, cost and time for NO result. Don't forget that the sheet steel is pre-painted in my case so welding would also break the film and add another potential corrosion source. Spray foam is a good / great alternative, but wasn't available in my case. I would still do mine from the inside out using spray foam instead of sheet

As to the construction sequence, again your choice. My frame is a space frame with the bed and cupboard frames welded to the main frame. In my case working from the outside in would have caused considerable extra work in cramped conditions without the clamping options available the way I did it. My choice made the task quite easy for me with my design and in fact much of the interior fitout was completed before the cladding was applied. You will prove yourself right or wrong when you finish the construction the way you choose to do it.

At my age I can confidently say that the camper will well outlast me. The original MOG fire cab was steel, 47 years old and still with only surface rust, no penetration.

So that said, I wish you luck with what ever solution you choose.

Tony

 

[arktrekker]

I think most mogs will outlast all of us. If I could afford one of the versions with a cab to hold 4 of us I would love to do a mog buildup.

When I was thinking about the metal, I hadn't thought about the prepainted panels. That throws another twist into the whole affair.

I am planning on some serious winter camping, so I had given thought to making the walls 2" thick using 1" square tubing for all but the top and bottom sills. This would allow me to have 2 layers of insulation with very little of the framing coming from the outside all the way through. I had wondered whether it would be worth the trouble to drill a few small holes in the horizontal framework and fill it in with spray foam as well. the holes would be small enough and on an interior side. The hole itself could be covered over with epoxy when finished.

Tony- I appreciate all of your input. It has given me a lot to think about.

 

[63tlf8]

I think most mogs will outlast all of us. If I could afford one of the versions with a cab to hold 4 of us I would love to do a mog buildup.

When I was thinking about the metal, I hadn't thought about the prepainted panels. That throws another twist into the whole affair.

I am planning on some serious winter camping, so I had given thought to making the walls 2" thick using 1" square tubing for all but the top and bottom sills. This would allow me to have 2 layers of insulation with very little of the framing coming from the outside all the way through. I had wondered whether it would be worth the trouble to drill a few small holes in the horizontal framework and fill it in with spray foam as well. the holes would be small enough and on an interior side. The hole itself could be covered over with epoxy when finished.

Tony- I appreciate all of your input. It has given me a lot to think about.

Yes, my tube frame is filled with expanding foam (at least as far as I can tell it should be 100%) We occasionally camp in the snow so ours is adequate for the limited use but in your case I would be looking at 60 - 100mm of insulation as you are.

Prepainted is the best solution. Usually comes on rolls with a great plastic protection layer so no chips or dings when fabricating.

Tony

 

[63tlf8]

......
Prepainted is the best solution. Usually comes on rolls with a great plastic protection layer so no chips or dings when fabricating.

Thanks for the kind words Peter. The outcome is the result of design "overkill" though. The ratio of thinking to doing was probably too high but so far I haven't found any major flaws in the concept or execution. From my perspective the separate roof section has made my task easier in many ways (harder in others) and unless I was going the full GRP route, including taped GRP bulkheads and furniture, I would still seriously consider building in to out on a fixed roof design.

A few quick pictures from the build. The interior Bed / lounge / table area was complete before exterior cladding. What you can't see is the plumbing and tanks are all in place too. Despite building these systems in before the cladding I have ensured that they can be easily removed for maintenance / repair. Left and right sides with the cladding before application of the corner and door trims. You can see the plastic film that protects the surface finish where I have peeled it back in some places. The camper is an Alaskan style as a quick explanation of the shape and lack of a roof at that stage. The sheet steel is full length, one piece, so no seams along the sides. A one person job except for the 3 Mtr length where my wife helped.

Good luck

Tony

 

[tom]

If you end up using metal on the outside check out 3M's VHB (very high bond) tape. It is designed to take the place of rivets and screws and is designed specifically for attaching metal skins to trailers etc.The 3M site has detailed info on how to use it. They seemed to have left out how to remove it. I call their techs and the guy chuckled when I ask how to remove the tape. There's two ways. One with a special saws all blade or a pneumatic chisel. The tape is very serious stuff but it really saves on installation labor.

Have fun and good luck with your build.

Tom

 

[half-cab]

Here is the link to Line-X for their claims about 'alternative' uses for their product: http://www.linex.com/other_applications_6.shtml

 

[arktrekker]

Here is the link to Line-X for their claims about 'alternative' uses for their product: http://www.linex.com/other_applications_6.shtml

The Line-X xtra coating was the one I had in mind. It was the finish I had on the exterior of a jeep and it was really nice. Pricey, but I plowed a deer and got rear ended without breaking through the finish.