Aluminium framed body?

[nathane]

Hi folks,

I'm in the development stages of my plan to build a camper based on a unimog with the vehicle bought and chassis modifications to start after the summer. I have been working the last week on a box design concept that I want to run past experienced folks here.

I was originally planning a foam composite monocoque, but recently courtesy of a friend who builds industrial hvac systems saw the boxes he makes using aluminium framed boxes with foam composite panels using extrusions and corners from these folks https://www.pro-lam.net/en

These boxes are a similar scale to my planned living unit (13 foot box), carry similar loads (3,000kg including box), can use panels up to 70mm deep, thermally bridged, and are robust enough to be lifted by crane or forklift by the frame.

I'm seriously thinking about building using this system, bonding panels in place with methylmethacralate adhesive to become structurally integral to the box.

I know most builders just glue panel to panel and the reinforce corners, but a small number (blissmobil) seem to use this idea. If anyone has observations as to why this might be a bad idea please can you shout?

Thanks

Nathan

 

[Buliwyf]

I'm seeing a ton of aluminium bonding in airplanes and trucks. Done right, it's much stronger. But from what I've seen, they still had a few bolts rivets mixed in there.

The new Fords are bonded where the back wall of the door or hood, come together with the outer skin. They are riveted as well.

 

[javajoe79]

Mine is all welded aluminum frame with aluminum skin glued on with Sika. Seems quite rigid and not too heavy yet. It's not done and hasn't been on the road yet so there is that. I have confidence in it. It won't be the most insulated thing ever but it will do just fine for me. I'm not planning on wintering in Alaska, yet

 

[nathane]

Correct. The profiles in question are 70mm square Al extrusions that build into the edges of the box. The profiles extend on the inner corner of the square to form a right angle V lip on the inside and I will glue foam composite panels into the gaps in the frame to form the faces of the box.

The benefit is that building the frame will be fast and easy to get precision dimensionally and whilst this is also possible with the foam to foam approach I think it will be harder and more time consuming.

The additional benefit is that it will be straightforward to incorporate fork lift pockets and container corners to make it easier to lift and manoeuvre (my box will be detachable to fit into a container).

Disadvantages: more joints - more potential failure modes? Is the thermal bridging adequate to stop cold spots (20mm plastic insert/air gap between outer and inner profiles)? Other?

 

[nathane]

Sadly not to my knowledge, as their main application only calls for right angles. I suspect cast corner joints require expensive tooling. This would be perfect welded though.

 

[Coachgeo]

Or just buy a used ambulance and use its box for half the price. Rip out keep all or part of interior. Insulate to desire

 

[nathane]

I think ambulance design is different in the UK, this isn't really an option. The price indication I have received (not a quote from the supplier yet) was surprisingly affordable. When I get a proper quote I'll let you know.

 

[tanuki.himself]

If you are UK based have a chat with these guys about how they build stuff including things like welfare vehicles (I think that means ambulances) and also look like they do boxes on their semi-articulated which may give you the lifting points you want.

http://www.coldsaverpanels.co.uk/

i'm thinking of using their panels for a slide in camper build in the coming months, and Neil Bloor their MD has been very responsive and helpful. Personally i'm planning on just using fibreglass/foam laminate panels without framing, but i'm not expecting to be as off-road oriented as a 'Mog....

 

[nathane]

Thanks for the heads up. The other attraction of the frame is the added rigidity when demounting, especially if this is done using a forklift from the rear (making it easier to load into a container). I was struggling to work out how I could easily properly reinforce edge joints otherwise without leaving "ugly" overlaminations of composite.

 

[tanuki.himself]

Agree with you 100% on ugly exterior laminations, but it looks from their portfolio page that they do some units with metal edges. As my scope is more occasional dirt roads and it will have its own legs/jacks on all 4 corners of the subframe for demounting at any time it should put less strain on the joints than lifting from one central area like a forklift, but i understand where you are coming from. My plan is also to be able to containerise it once it is off the truck, but i'm relying on being smaller and able to lower the camper gently onto a pallet that can then be rolled into the container on a handcart forklift - my weight should be well under 1000kg dry.

 

[Victorian]

I find it interesting that so many people are looking into a "de-mountable" system for shipping. In my years in this field, I have come across many world travellers. 99% of them ship their trucks either through RoRo ferries or on open platform containers. No need to have some underpaid worker at some port around the world undue your camper and lift it around. Most ports wont let you in anyway... You hand the keys over and they take care of it, or not.... In theory you could do the de-mounting at a safe place outside the port. But imagine you are travelling from Australia to India. In Australia you would find qualified shops and logistics fairly easy. Getting to India, it's a totally different story.
I would rather ship a complete vehicle.
Then there is the argument about being able to ship the camper body as a container. We do container shipments all the time. Have you ever seen how those containers look like? I would not want to have my $300.000 camper in between those! Apart from that, shipping containers need to be sea freight certified. Can't see a camperbody getting that certification.
Then there is the cost:
Why pay for the camperbody and truck separately? Having one unit is half price and less hassle!

In other words: Mount your camperbody proper and ship RoRo. It's being done every day around the world.

 

[tanuki.himself]

In other words: Mount your camperbody proper and ship RoRo. It's being done every day around the world.

I'm sure it is, but its not always available. I'm currently stuck in Guatemala as I can't drive past Nicaragua, and there is no RORO available - I have to containerise. There is also what you do with all your contents - my understanding on this is that some RORO don't allow personal belongings in the vehicle in case of theft, whereas if you containerise the vehicle outside the port its locked in,

 

[Victorian]

I'm sure it is, but its not always available. I'm currently stuck in Guatemala as I can't drive past Nicaragua, and there is no RORO available - I have to containerise. There is also what you do with all your contents - my understanding on this is that some RORO don't allow personal belongings in the vehicle in case of theft, whereas if you containerise the vehicle outside the port its locked in,

What about an open platform container?

 

[nathane]

Few thoughts here.

First the single dual unit question doesn't apply. I am building a modest sized hab unit to fix on the back of a mog. There will be very little difference in construction if it's a permanent mount or demountable, just a little thought up front to make it work. Therefore I'd say why not build in the optionality? We will be able to roro where appropriate and container where roro isn't an option.

My plan would be to do the load unload ourselves and yes, I agree that will add a little complexity to the logistics in some countries but I'm happy to take that risk, especially if the bail out option is what we'd be forced to do anyway.

Finally this is not a body that will ship as a container, but a body that will ship in a container. The mog and box will fit together in a 40' hicube with space to spare. I agree it would be insane to build the hab box to a standard that could take stack loads of 60 tonne containers on top.

For me it's a no brainer to build in the additional option of demount as it will add little cost and no net weight.

 

[tanuki.himself]

For me it's a no brainer to build in the additional option of demount as it will add little cost and no net weight.

Hear Hear - prepare for all eventualities and you'll seldom get caught out. Or a pessimist is only ever pleasantly surprised.....