Camper Shell Materials

[DiploStrat]

I am sorry; I seem to be annoying you and that was certainly not my intention. I have offered my opinions and experiences only to be helpful.

My only comment in reference to the Mitsubishi thread (which I have followed closely) is that several people have taken a single approach to the problem of mounting a camper and in the process have badly damaged their trucks. There are several ways to solve the problem and extended off road/bad road travel poses many challenges in addition to those of crawling over a big rock. Different approaches, taken by other travelers and commercial firms, have been more successful.

The UNICAT blurb is actually a very good analysis of the problem from start to finish. It discusses why the approaches employed on some the Mitsubishis under discussion might not work, notes the need to use a approach engineered by the vehicle manufacturer, and underscores the need for a holistic approach; the suspension, chassis, and camper must each be matched to the other. This is not easy – it is certainly beyond my skills.

Pax!

[iandraz]

I should have clarified earlier - here's a view of my planned box construction method:



Link

This is sort of an exploded view, the foam wall goes into the corner made by the metal. Three walls go into the three faces in this view, but I've only shown one, for clarity.

The edges are 3x2" .095" steel tubing, with 2" x 1/8" strip welded on for the flanges.

The wall is foam with fiberglass on the inside and outside. The wall attaches with some sort of adhesive to both faces of the metal.

I think this is similar to the construction used in most of the German expedition campers, although I haven't been able to find good pictures or diagrams online. The idea is to combine the advantages of both materials - the foam provides good insulation, stiffness, and light weight across the wall, while the metal provides impact resistance, corner strength, and integration with the floor frame.

[iandraz]

This site has some useful wall construction pictures:

http://www.bocklet-fahrzeugbau.de/kabinenbau.html

This method appear similar to what I plan to do. Unfortunately I don't know German and the text is an image so Google Translate doesn't work for it.

[oltmann]

iandraz,

I like your planned construction method. It is right inline with how I plan to build.

Have you found a source(preferably local) for the panels?

[iandraz]

oltmann,

I'm in Portland OR but my truck is in Vancouver WA so if you want to stop by and have a look just PM me!

I'm leaning towards the Fiber Tech product right now - it's not exactly the material Unicat uses, but I think it may be okay for my purposes. And they are in Spokane WA which is sort of local. They said shipping would be around a couple hundred dollars.

There's an interesting point that we haven't really gotten into in detail here - matching coefficients of thermal expansion. You can see on the Unicat site that they make note of this a lot - "Matched thermal coefficients of expansion prevent distortion with changes in temperature ". The idea is that you want both the wall and frame to expand and contract the same amount with temperature swings, so there isn't any warping or delamination.

I've been looking through some of the German expedition forums lately with Google Translate which is very useful. There is a good thread on one which was started by Emil (EGN) who posts here as well:

http://www.lkw-allrad.de/forum-I/index.php?showtopic=1373

The rough English translation is here:

http://translate.google.com/translat...ate.google.com

In it the following site is mentioned:

http://www.c-kroeger.de/Homepage/html/german/ausde.htm

This site lists the coefficients of thermal expansion for various materials.

There is another one from the same site here which describes how to calculate the required adhesive thickness for given coefficients, using a rule of thumb that the adhesive can "stretch" 50% of it's thickness:

http://translate.google.com/translat...istory_state0=

Looking at the translated chart, you can see the following expansion values, measured as millimeters per square meter at a temperature difference of 60 ° C:

Steel: .66 mm
GfK (I think this is fiberglass): 1.2-3.0 mm
Wood: 0.18-0.36 mm

Based on this, it might not be bad to have the plywood layer in the wall material, since it is a better match with steel than fiberglass. However I'm not sure how good a match it is with the foam core. I assume it must be okay since it appears Fiber Tech has been making this sort of product for a while for similar applications (trucks and trailers).

[oltmann]

Thanks for the invite. I will have to stop by sometime, I really like how the truck is shaping up.

I've been thinking of making my own panels, just not sure if it's realistic.

Also, every time I search for honeycomb fiberglass materials I see a lot of ads for Chinese companies. Has anyone ever worked with any fiber panels from China? Group buy on a container full?

[iandraz]

In another thread Echo_29 linked to the site for Der Fehntjer, a German camper manufacturer. They have some nice photos on their website showing how their walls fit together:

[Greg]

I am hoping this discussion of camper or shell materials will continue. The weight of the camper and the joining and sealing methods used at wall-to-wall and wall-to-roof appear to be the main concerns. My thoughts on material are to use extruded polystyrene which has about a 2lb density and is inexpensive and then cover with expoxy and fiberglass. I am considering using 2inch thick polystyrene and possibly covering the exterior with .25inch plywood for compressive strength. The plywood may be overkill. I am still trying to understand how many layers of fiberglass and what weight and type of fiberglass.

Other people using extruded polystyrene and fiberglass are hovercraft and surfboards. Universal Hovercraft is a site will also see materials. Some of the builders are using a 4inch thick hull of polystyrene with .125" marine plywood on top only. This gives their deck the compressive strength for 2-4 people walking on it. Polystyrene is sensitive to solvents if they somehow get past the fiberglass.

If you use one of the more expensive marine polyurethane foams of around 5lb density, the sheet thickness can drop to 1" or less. See construction photos of Pedigree Catamarans and construction photos of the ocean going row boat, Brother of Jared. Glen-L.com shows the same for their boat building methods. There are parts of a book online written by Ron Palmer called Building a Foam Core Boat. This talks about foam thickness and also fiberglass thickness.

The Turtle V and later on the Supercamper both used NidaCore however I do not fully understand the sanding issues Ryan had as he built the Supercamper.

[Christian]

Hi Peter
That looks like an interesting build, is there a thread about it somewhere?

About Nida-core and the sanding issues, you can get Nida-core panels, with skins, both smooth and sanded. I am pretty sure that the Supercamper used smooth surfaced panels. As I read it Ryan had issues getting in to the tiny "dimples" in the surface created by the honeycomb cells.
I have talked to an old and very knowledgeable boat-builder, who advised me to use smooth panels and sand them myself to avoid contaminating the sanded surface when building, thus making it difficult to get a good bond.

Best Regards, Christian

[Christian]

I see your point, and I have samples of nearly all Nida-Cores products, and I don't see the dimples. Maybe it's because the sample is too small, maybe there are a very tiny dimpling that comes out when sanding? Or maybe Ryan and Holly were not experienced in working with fibre glass and got suprised by the hours needed. As I recall they started painting with the wrong paint and had to sand it all down right? That might be the issue.

All in all we plan on using Nida-Core for our 6X6 Volvo project.