Overlander Camper Frame Material: Aluminium vs Mild Steel vs Stainless Steel?

[rruff]

Links please.

Everlanders Build - F550 Composite Overlander

Hello all, As you can see, we've been lurking around here since Oct 2012, planning, saving and working towards our Overlander. In early 2013 we found the exact truck we were looking for and snapped it up. As you could see it had quite the appendage on it at the time. I started filming odds...

expeditionportal.com

Also, the Ram 3500 linked above.

I would suggest following this example.

Build: Ram 3500 and Aluminum/Composite Expedition Camper

Welcome to the documentation of our build! Intro: My wife Courtney and I have decided to make the move towards full time adventure. We currently live in a self built shipping container house: To anyone considering tiny living I say go for it and never look back. Simplify your life and focus on...

expeditionportal.com

External aluminum frame with bonded panels.

Except I'd suggest a stronger foam if you can afford it. 15psi XPS is weak stuff. I'm using 4lb/cu ft PVC foam from Carbon Core, and it's ~2.5x the weight, ~10x the strength, and ~5x the cost. I'm using 1.5" on most; 2" on the floor/base. Total of ~$2,500 in foam for a big truck camper. Not that much in the grand scheme of things.

 

[rruff]

Not sure if you’ve seen these ready made panel products, but might be useful to your build, or at least for reference.

Someone mentioned this company recently: https://www.plascore.com/

 

[Peter_n_Margaret]

Someone mentioned this company recently: https://www.plascore.com/

Avoid honeycomb. Edge finishing is problematic and the thermal insulation qualities are poor.
Cheers,
Peter
OKA196 motorhome

 

[rruff]

Avoid honeycomb.

Ah yes! But he said they do foam core as well... and it looks like they do foam filled honeycomb.

 

[Alloy]

You design for the material and what you can get. Steel makes sense if you can get thin wall tubing in the dimensions you want to use otherwise you're carrying around a lot more weight than you need.

A think about this, aircraft airframes are made from aluminum and you have no qualms about boarding one, do you? If you're worried about aluminum's ability to flex and resist fatigue you probably shouldn't get a window seat.

These airplane wings that flap like a bird. Amazing the cycle times that are achieved.

 

[IdaSHO]

I say go with whatever you are most familiar and comfortable with, and openly acknowledge its benefits/downsides so you can work with/around them.

There is no one size fits all.

Personally, I prefer wood. Even though nobody else does.
But when compared to anything metal, it is superior in one way that I could never overlook... thermal performance.
It is simply amazing just how well this camper performs in ANY weather.
And at the end of the day, that is job #1 for a camper. To protect its occupants from weather.

8 years on the road now, and going stronger and looking better than ever

 

[Peter_n_Margaret]

These airplane wings that flap like a bird. Amazing the cycle times that are achieved.

That is an aluminium wing. Aluminium has a very specific fatigue life (remember the Comet?)
Gliders on the other hand are made from fibre reinforced plastic and they can not only flex MUCH more, but have an almost unlimited fatigue life by comparison.
Pin on Gliders & non-motorized aiplanes (pinterest.com.au)
I used to fly high performance sailplanes and I can say from experience that the wing flex in the top pic above is "normal".

Wood actually has an extremely high fatigue resistance too, but lacks the consistency, variable applications and rot resistance of FRP.
Cheers,
Peter
OKA196 motorhome

 

[shirk]

I say go with whatever you are most familiar and comfortable with, and openly acknowledge its benefits/downsides so you can work with/around them.

There is no one size fits all.

Personally, I prefer wood. Even though nobody else does.

Recently came across another wood camper build on Youtube. He's making torsion box flat panels filled with foam the covering in fiberglass.

 

[alanymarce]

In the grand scheme of things, I’m not too worried about the cost difference between these materials, so that’s not much of a deciding factor.

If that's really the case, then titanium would be best. In case it's true only for the three you mentioned, then I think the key here is that if you go for steel you'll have to ensure complete protection against weather, to avoid corrosion. Stainless steel would be better in terms of corrosion. Aluminium is tricky to weld, so if you do it yourself you need to be competent (in aluminium welding, specifically). Marine ply is strong, relatively light, and may be a good choice. I have no idea what the regulations may be for your jurisdiction, however you should make sure the structure is robust.

Lastly, the mass issue - steel is relatively heavy, aluminium better (as is titanium). Mass is your enemy (fuel consumption, structural stress, CoG and stability, handling, as well as reducing the available GVM for other stuff you want to carry). I suggest making sure that your design is elegant (in the structural engineering sense, although elegance in terms of grace is fine too) - you need the best structural integrity for the least material. It's worth an engineering check on this (if you can do it yourself, perfect!).

THe structural stuff we've done on our previous and current vehicles has been a combination of mild steel and wood, however this has been for the interior of the vehicle so no real concern about corrosion. We did build a roof rack from mild steel for our previous vehicle, and didn't protect it well enough so that after six months or so corrosion was starting... Next time we start a new design we'll seriously consider titanium.

PS: I imagine that some will wonder why I refer to "aluminium" instead of "aluminum" - for those people I'll ask why, if it should be "aluminum" it isn't "titanum"? I respect the fact that spellings are different; I'm just interested in the inconsistency.

 

[rruff]

Personally, I prefer wood. Even though nobody else does.

Wood is great! Strength and stiffness to weight is close to metals, and there are many places where a less dense material performs better... like interior and exterior skins. A layer of plywood and fiberglass will be much more sturdy against impacts than fiberglass alone (for the same weight). It's much better at protecting a weak core material too.

I believe a very well designed and constructed fiberglass+plywood skinned camper with a foam core will result it the lightest and most durable structure. Better even than carbon and foam.

Just need to be careful with penetrations and leaks. But they build boats out of this stuff, so...

Recently came across another wood camper build on Youtube. He's making torsion box flat panels filled with foam the covering in fiberglass.

Pretty cool! But suboptimal, I think. He could use a lot less wood if he used a stronger foam. Plus his skins are ~5mm wood, and ~0.2mm fiberglass. 3mm wood and 0.5mm fiberglass on the outside with 3mm+0.2mm on the inside would be

 

[Alloy]

Aluminum offers a marginal weight saving but steel is far easier to weld.

When we compared the cost of sandblasting or grinding (to remove mil scale) for painting to bare alum cheaper the aluminum was less expensive. At the time alum cost 50% (before 2018 duties) more but is cheaper to (person can carry small piecs, cutting / welding / grinding is faster) fabircate.

Problems arise when engineers asked for details that were used for steel. Seal welding the hollows (pipes / squares / rectangles) is an example.

The #1 mistake I see made with DIY is quality control. Fit up is poor and the quality of welds are not checked .

To be done correctly the fit-up of steel can be 7 our of 10 while aluminum needs 9 out ot 10.

 

[HAF]

I built my camper out of aluminum. I used canon steel to build a sub frame. Aluminum sides are taped on. Its robust and thermally efficient (no cold bridges).

 

[rruff]

I built my camper out of aluminum. I used canon steel to build a sub frame. Aluminum sides are taped on. Its robust and thermally efficient (no cold bridges).

How are your walls constructed?

 

[HAF]

How are your walls constructed?

Two inch square tube. Base is made from a irked 2 x 12 channel that ties the floor into the walls. Floor and roof are 1/8” aluminum-all welded. Bare frame weighs about 890 pounds.

 

[rruff]

Two inch square tube. Base is made from a irked 2 x 12 channel that ties the floor into the walls. Floor and roof are 1/8” aluminum-all welded. Bare frame weighs about 890 pounds.

How do you prevent cold bridges with an aluminum frame? Do you have aluminum skins on both inner and outer walls? How is it insulated?