Overlander Camper Frame Material: Aluminium vs Mild Steel vs Stainless Steel?
- Thread starter FurthurMore
- Start date
FurthurMore
New member
Thanks for all the responses everyone. Some really good info.
I like the links to similar truck camper builds; I’ll definitely check those out in detail.
Good points, thanks. Based on what everyone has been saying here, I’m leaning towards going with mild steel for the frame, as it will just make my life easier especially with welding. Coat the inside with linseed oil or Fluid Film as suggested, and I could put a small tapped hole with a screw at the bottom of each tube member for occasional draining if needed.
As people have mentioned, I’ve have probably gone overkill with the frame structure, so I’ll look into removing some of the members to save a bit of weight, especially if I am going with steel.
From a quick search of Huck bolts, it doesn’t look possible to use these when you don’t have access to the back of the part you are bolting, e.g. half way down an 8ft square tube. Is this the case? In a similar vein, I suppose I could use blind rivnuts/nutserts, but I think they have a tendency to come loose and spin when experiencing a lot of vibration.
The main reason I’m choosing not to go with composite foam-core panels is because they are significantly more expensive than a welded frame and riveted construction, and I am working to a fairly tight budget. No doubt though, composite panels have benefits such as lighter weight and less thermal bridging.
My estimates for cost for a camper box constructed of a welded box section frame ($500-1100, depending on material) with 1mm aluminium sheet metal panels ($1200) externally coated in bedliner ($1000), held onto the frame with rivets ($300), and with XPS foam insulation ($500), gives a total of $3500-4000 for a complete camper shell.
On the other hand, pre-cut composite panel kits as linked by REF are ~$10,000. Even if I bought and cut my own ready-made composite panels, I’m looking at least $7000+ (at least based on the readily available online prices I could find; maybe there are cheaper options but I’d have to dig deeper) and I would then still need to make an outer framework to hold it all together. If I could find a supplier of composite panels that works out cheaper then I may strongly consider that method.
I’ll read more into the viability of custom bonding my own composite panels, as perhaps that would work out to a similar cost as a welded and riveted frame.
Very cool that you made that all out of wood. What is the outside coated with, fiberglass?
Sorry, I should have explained. Yes, there will be insulation foam board bonded onto the outer metal skin. To combat thermal bridging from the metal frame, non-corner members will be half the width of the corner members. Thus, I can overlay a thinner section of foam insulation over these, so no metal parts fully bridge from outside to inside. I hope the cross-sectional view below illustrates what I mean. Any thoughts on constructing the walls like this?
I like the links to similar truck camper builds; I’ll definitely check those out in detail.
Good points, thanks. Based on what everyone has been saying here, I’m leaning towards going with mild steel for the frame, as it will just make my life easier especially with welding. Coat the inside with linseed oil or Fluid Film as suggested, and I could put a small tapped hole with a screw at the bottom of each tube member for occasional draining if needed.
As people have mentioned, I’ve have probably gone overkill with the frame structure, so I’ll look into removing some of the members to save a bit of weight, especially if I am going with steel.
From a quick search of Huck bolts, it doesn’t look possible to use these when you don’t have access to the back of the part you are bolting, e.g. half way down an 8ft square tube. Is this the case? In a similar vein, I suppose I could use blind rivnuts/nutserts, but I think they have a tendency to come loose and spin when experiencing a lot of vibration.
The main reason I’m choosing not to go with composite foam-core panels is because they are significantly more expensive than a welded frame and riveted construction, and I am working to a fairly tight budget. No doubt though, composite panels have benefits such as lighter weight and less thermal bridging.
My estimates for cost for a camper box constructed of a welded box section frame ($500-1100, depending on material) with 1mm aluminium sheet metal panels ($1200) externally coated in bedliner ($1000), held onto the frame with rivets ($300), and with XPS foam insulation ($500), gives a total of $3500-4000 for a complete camper shell.
On the other hand, pre-cut composite panel kits as linked by REF are ~$10,000. Even if I bought and cut my own ready-made composite panels, I’m looking at least $7000+ (at least based on the readily available online prices I could find; maybe there are cheaper options but I’d have to dig deeper) and I would then still need to make an outer framework to hold it all together. If I could find a supplier of composite panels that works out cheaper then I may strongly consider that method.
I’ll read more into the viability of custom bonding my own composite panels, as perhaps that would work out to a similar cost as a welded and riveted frame.
Very cool that you made that all out of wood. What is the outside coated with, fiberglass?
Sorry, I should have explained. Yes, there will be insulation foam board bonded onto the outer metal skin. To combat thermal bridging from the metal frame, non-corner members will be half the width of the corner members. Thus, I can overlay a thinner section of foam insulation over these, so no metal parts fully bridge from outside to inside. I hope the cross-sectional view below illustrates what I mean. Any thoughts on constructing the walls like this?
FurthurMore
New member
Thanks for the reply. Are you referring to the corners of the box where I have diagonal braces on all three of the perpendicular planes (in the image in my initial post)? Maybe it’s overkill but my intention here is not just structural but also to stave off distortion when welding by first tacking the diagonal braces before doing full joint welds. Do you mean this should be done differently?
Do you mind explaining what the importance behind that is?
I thought TIG causes less distortion than MIG due to a smaller heat-affected zone? I tried looking online and I can’t find much definitive information at all on which method causes less distortion. Although I did find this video which seems to say that TIG causes less distortion in sheet metal work so I assume it would apply to framework welding as well?:
Again, I’ve never used TIG before so I have no idea myself.
IdaSHO
IDACAMPER
Only issues I have with that are the fasteners between dissimilar metals, and the cold bridges created by fasteners.
The dissimilar metal contact will cause corrosion in short order.
Similarly, Rivet-Alum-Steel-Screw connections, as shown, will likely rot out the plywood due to temp differences and condensation (on the inside of the cabin)
Solution? For that assembly, ditch the rivets all-together and go with VBM tape or an adhesive.
And for the welded nut, riv-nuts would likely be a great alternative, as already mentioned.
rruff
Explorer
Similar or lower cost, probably less learning curve since you don't know how to weld, lighter, and better insulating.
I built a camper 20 years ago that was similar to Idasho's method, and have no qualms about recommending that. I lived in it for a few years and beat the crap out of it and it was flawless. The "torsion box" video posted earlier is a similar idea. I coated it all with a good layer of wet laid fiberglass and then gelcoat. The only reason I'm doing it different now (wet layup fiberglass and carbon on PVC foam and no wood) is because I have more money to spend and I like trying different things.
The only thing that would shy me away from just skins glued to garden variety XPS is that some people (camper builders and surfboard makers) have had issues with outgassing and debonding at higher temperatures. Plus the foam is weak in the best of circumstances, and better alternatives are expensive. But you can allay any worries about that by using some internal wood structure in the core... like in the video I mentioned but not so excessive... just enough to give extra support to the foam, and keep the skins where they belong. Say vertical 1x board strips on edge every 18" or so, with thinner strips laid in between with similar spacing. The foam will be cut to precisely fit in those spaces. That will be your core. If there are any gaps seal them with expanding foam, and glue the skins to both the foam and wood strip edges.
At any rate it would be best to start thinking in terms of structural panels, rather than attaching stuff to frames. Go to your local building store and buy some thin ply, boards, XPS (the highest rated they've got) and PLP glue, and make some samples and see what you think.
In my case, need to support 600-800lbs of gear on a roof rack.
Hence the idea of a fully external lifting frame
with an insulated "living pod" that sits within,
the top half pulled upwards lifted by the rack above
whole pod can be removed so the trailer has working utility when not using it for camping.
There need be no bridging with that idea, since all the structural framing is outside
the pod has very little load bearing strength, other than "wind" resistance and internal cabinetry and bunks
DIY composite or maybe even foamie PMF with some strategically embedded wood should do, design for as light weight as possible
and good insulation for ski area camping in northern winters.
the pod has very little load bearing strength, other than "wind" resistance and internal cabinetry and bunks
DIY composite or maybe even foamie PMF with some strategically embedded wood should do, design for as light weight as possible
and good insulation for ski area camping in northern winters.
Joe917
Explorer
That is a different case. A composite camper does not require any external strengthening. Our truck carried 500 lbs of spare leaf springs on the roof for 23 years on a steel roof rack that was only supported by the box corners. One of the first things I removed. All that weight up high is crazy.
HAF
Active member
formed!
HAF
Active member
Those countersunk screws will transfer cold to interior. They can act as a bridge. Metal has no insulation value and will transfer cold. When the cold hits the head of screw where it will be warmer, condensation can result. You could try using fiberglass fasteners (Mcmaster Carr). If you use foil face insulation, you could apply glue before the plywood. An alternate to plywood (heavy) would be KAPATECH. Its a 3/8" thick foam board with thin aluminum face on either side. Glue to Foil insulation-you get more insulation value. You could then use fiberglass screws to further secure it.