Habitation Cabin Construction

[Neil]

I am in the planning stages of building an oveland camper on a flatbed truck

The habitation cabin will be approx 5 mtrs long

There appears to be two methods of construction for the cabin

1 Laminated GRP in sheet material with corner joints

2 Steel subframe ( Skeleton ) clad with sheet alluminium on the outside and insulated on the inside followed by an internal ply inner skin.


My question is simply

What are the pros and cons of each of these construction methods .

I would value your views

many thanks

Neil

UK

 

[Iain_U1250]

I decided to go with the steel frame and aluminium skin mainly because of strength and resistance to vibration issues.

I did a lot of research before embarking on this path and looked and listened to a whole lot of diifferent opinions. Composite panels were the easiest in theory, but the joints particular around the roof area are a major weakness and source of leaks, in addition, they are so rigid that when subject to vibration, they tend to crack at the stress point which is most case are the joint again. As recently pointed out by a boat builder - you don't see many boats made out of jointed composite panels - they are monolithic moulds with an inner and outer hull.

In the end I had two choices, build a monolithic fibreglass shell ( that would mean building moulds for both the outer and inner skins, or use the aluminium over steel frame method.

Time will tell if my decision has been a good one, but based on the reports I have had from people who have professionally built trucks using composite panel ( GXV and Unicat) that over time have developed leaks - I stand a better chance of remaining water tight.

My build thread is:

U1250 Camper build

 

[63tlf8]

There appears to be two methods of construction for the cabin

1 Laminated GRP in sheet material with corner joints

2 Steel subframe ( Skeleton ) clad with sheet alluminium on the outside and insulated on the inside followed by an internal ply inner skin.


My question is simply

What are the pros and cons of each of these construction methods .

I would value your views

Neil

Hi Neil,

There are quite a few options, which largely depend on the facilities available and the skills you have. Iain chose Steel frame with Alu skin. I chose steel frame and steel skin. Actually lighter than Alu in the respective sizes used and you don't need to be so particular about galvanic corrosion or differential expansion rates. Suited me and my design but not everyone, albeit very few ever do the sums on this option as it is seen as old fashioned.

Commercially, economical manufacturing processes and a pleasing finish drive many construction options. When it is a one off then the world is your oyster.

From memory Iain has incorporated passenger seating in the cabin so ROP standards have to be met. This may apply to you too. In researching the options I came to the conclusion that almost any construction method could be used if the outcome suited your intended use and construction intentions.

Elsewhere on the forum there is a brilliant wood and GRP replica of an Alaskan camper. Downside is it is probably a little heavy as constructed but could be lightened considerably without loss of utility. ROP issues and the like aside, high tech wood construction has the potential to live as long as anything on todays market so I do believe it remains on the viable option list too.

I found that the commercial construction techniques are not always easily achieved on your own without the significant tooling and facilities that are a part of an assembly line process.

So my suggestions are that you could start out by considering everything. The depth of your pocket and skills / facilities will help you decide.

Tony

 

[Neil]

Thanks folks

Plenty to take on there.

best wishes and happy travelling

Neil

 

[Eric S.]

I've been planing a Unimog Camper myself and am leaning toward the steel skeleton. The main reason is if I have a problem with the frame the middle of no where I will be able to repair it myself with an on-board welder.

 

[Bogo]

2 Steel subframe ( Skeleton ) clad with sheet alluminium on the outside and insulated on the inside followed by an internal ply inner skin.

Slightly modify this one. Make the skeleton external, and glue aluminum clad foam panels to the inside. That is the style used for this camper: http://www.expeditionportal.com/forum/showthread.php?t=20822

If you are willing to have fittings made for the corners you can glue the whole thing together with auto body adhesives but cleanliness and proper surface preparation are necessary. Most metals are weakened by welding and gluing avoids this. When the glue patches are sized right and proper surface preparation is done they can be much stronger than a weld. Most car bodies are now glued together. Ungluing is done with a knife and heat gun.

 

[Iain_U1250]

I used SikaFlex 252 and using the proper cleaner and primer, the aluminium tore before I was able to pull it off the steel.

 

[LukeH]

Two variations of a method seen here in France:
Skeleton made of light wood battens, foam cut to measure fitted in the gaps.
exterior primed with resin and glass fibre mat draped over.
Start with the sides and drape the top last.
The whole lot rolled with resin and then gel goated.
That's kept one company going for a while now: http://www.clemensonamenagement.com/

Same method with an aluminium skeleton, but that gives massive cold bridges unless you double insulate afterwards.
http://forum.bernard.debucquoi.com/viewtopic.php?f=81&t=4315

Another one that I've seen is an internal skeleton, and all the insulation on the outside.
http://famillenomade.free.fr/dotclear/index.php?pages/La-construction-du-camion

I'm going for the refrigerated lorry panels. Construction is simpler but you lose in the flexibility of shapes. My camper body will always look like a brick. The two styles above mean you can make any shape you want.
The danger is overbuilding the skeleton. I did my masters thesis on replacing the triangulation of a vehicle spaceframe with a skin, a glass fibre weave at 45%.
Weight savings and more rigidity. You only need to triangulate to hold the overhanging parts before skinning.
Good luck

 

[ersatzknarf]

Hi Luke,
Thank you very much for the descriptions and links. Very informative.