(USA) panel options Total Composites or GXV DIY Adventure Kits

[rruff]

You'll see sub frames incorporated into the floor. It reduces the OA height but there is allot more thermal transfer.

Use composites instead of metal.

My camper doesn't have a subframe. The bottom panel is 44oz carbon+epoxy skins on 2" 4lb PVC foam, with mounting areas reinforced with 3/8" epoxy cylinders on 2" centers. The reinforcement is probably not necessary (the foam is good for 150 psi), since I have large carbon mounting plates that are 20mm thick to spread the load.

 

[boogie944]

I thought the whole point of the subframe was to provide a stiff platform to mount the box to? The stiffest member is the one that takes the bulk of the load.

If the box is strong enough to take the load then you can remove the subframe and just provide reinforced mounting points between the frame and box. In your 3 point design, this means that 3 locations need reinforcement, and you can ditch the rest of the subframe. Seems like it would be more weight efficient.

The point of the sub frame is to provide a hinge and raise the box enough so it can move around (or the truck chassis torque freely underneath). It does eliminate all torsion intrduced by anything below the box (eg axles going over uneven terrain). But the box itself still needs to take up some torsion for let's say a person not standing in the centerline of the box but on one side. This is a small force, but if you would consider only the subframe the subframe itself would not be able to take up this torsional load. Try standing at a corner of the subframe.

You are right from structural analysis purpose the stiffest member is the one taking all the load and considering only subframe and box that is in all cases the box.

 

[Alloy]

The point of the sub frame is to provide a hinge and raise the box enough so it can move around (or the truck chassis torque freely underneath). It does eliminate all torsion intrduced by anything below the box (eg axles going over uneven terrain). But the box itself still needs to take up some torsion for let's say a person not standing in the centerline of the box but on one side. This is a small force, but if you would consider only the subframe the subframe itself would not be able to take up this torsional load. Try standing at a corner of the subframe.

You are right from structural analysis purpose the stiffest member is the one taking all the load and considering only subframe and box that is in all cases the box.

I disagree. If 150-200lbs can twist a subframe then it won't be strong engough. Once the subframe hits the stops it needs to be rigid enough to make the wheel(s) of the truck come off the ground.

 

[boogie944]

Use composites instead of metal.

My camper doesn't have a subframe. The bottom panel is 44oz carbon+epoxy skins on 2" 4lb PVC foam, with mounting areas reinforced with 3/8" epoxy cylinders on 2" centers. The reinforcement is probably not necessary (the foam is good for 150 psi), since I have large carbon mounting plates that are 20mm thick to spread the load.

Not all trucks need a subframe. Likely @Victorian does not have one either on his Transit. And I have an inbetween solution with spring mounts (Isuzu NPS 7t chassis). My truck is not behaving very well with a 3 point subframe as the chassis is relatively light.

All depends on weight of the truck and the terrain you like to go to. Looking at what others have done I noticed anything below 5t GVW most have no torsion free sub frame.

 

[rruff]

Looking at what others have done I noticed anything below 5t GVW most have no torsion free sub frame.

It depends on the frame stiffness. Newer 1 ton and under pickups (except for Tacomas and Tundras) have fully boxed stiff frames. 20 years ago I don't think any of them did. Over 1 ton the frames are flexible C channel, so the frame articulates rather than the suspension. When the frame is flexible you need to deal with it somehow, or your box will end up being the stiff part of the structure and take all the load.

Can you describe the "not behaving very well" of the 3 point?

 

[Alloy]

The foam has a crack. How long will it last when it is bolted to a sub-frame and people are walking on it. By the time the issue become serious the 1 year warranty would have expired.

 

[rruff]

The foam has a crack.

Their marketing is not giving me a warm feeling. If there was some actual engineering done, they wouldn't need dumb it down like this. The PUR vs PIR comparison is pure BS. PUR made for structural applications is rigid. I don't know where they got that stuff... maybe from a spray can?

The "standing on the panel" test is funny also. First... shaky cam and no actual measurement. I computed that a similar sized panel of the stuff I'm making should be able to hold 10x that weight... 2,500 lbs. Maybe I'll build a sample and make a video of my truck being supported on it...

 

[Alloy]

Their marketing is not giving me a warm feeling. If there was some actual engineering done, they wouldn't need dumb it down like this. The PUR vs PIR comparison is pure BS. PUR made for structural applications is rigid. I don't know where they got that stuff... maybe from a spray can?

The "standing on the panel" test is funny also. First... shaky cam and no actual measurement. I computed that a similar sized panel of the stuff I'm making should be able to hold 10x that weight... 2,500 lbs. Maybe I'll build a sample and make a video of my truck being supported on it...

I hate it because it's first time buyers that gets nailed by stuff like this.

I just watched the box assembly videos. At 3:49 the guy says "there is no shear point here in the panel"....that's wrong. The only thing carrying the load between the extrusion and the sub-frame is the floor panel.....so the floor panel is under shear. The flat bar in the floor does nothing to support the walls.

 

[boogie944]

It depends on the frame stiffness. Newer 1 ton and under pickups (except for Tacomas and Tundras) have fully boxed stiff frames. 20 years ago I don't think any of them did. Over 1 ton the frames are flexible C channel, so the frame articulates rather than the suspension. When the frame is flexible you need to deal with it somehow, or your box will end up being the stiff part of the structure and take all the load.

Can you describe the "not behaving very well" of the 3 point?

At low/normal road driving speeds the suspension is not working well as it is too easy for the chassis to torque. Causing lot of movement of the driver cab which is not very comfortable.

 

[boogie944]

I disagree. If 150-200lbs can twist a subframe then it won't be strong engough. Once the subframe hits the stops it needs to be rigid enough to make the wheel(s) of the truck come off the ground.

Depends all on size of your truck. If the sub frame and/or box survives lifting an axle I would say you do not really need a 3 point suspension on yur sub frame/box. If you have something like LMTV size truck subframe and/or box is unlikely strong enough to lift an axle once you hit the end stops.

 

[rruff]

At low/normal road driving speeds the suspension is not working well as it is too easy for the chassis to torque. Causing lot of movement of the driver cab which is not very comfortable.

This is typical of HD trucks. The suspension is very stiff for load carrying, and frame articulates to keep the tires on the ground. A twisting frame is an undamped spring. It should help to upgrade your suspension with a greater number of thinner leaves and appropriate shocks.

Curious what your setup looks like exactly. You mentioned both a 3 point, and spring mount. The spring mounts typically have a subframe that is "clamped" to the main frame rails with springs. This will keep the two together until the frame twist reaches a certain threshold. These should work better on the street, but they will impart more torque to the box when offroad.

 

[simple]

This is an interesting discussion covering the subframe subject from various angles. Can someone move it to a new thread with appropriate title?

 

[Blackdogvan]

Back to the intent of the original post...

Total Composites has been in business for quite some time and seems to have a pretty loyal following of builders and customers who attest to the longevity of the product. It is my understanding that the same factory that produces their panels also delivers the same technology and materials to some pretty major European manufacturers of very high end trucks. So in this day and age where negative word spreads instantly online, crap products can't hide anymore & it seems to me you can't really go wrong with their system should you lean that way as if it was as inferior as the g trekker guys seem to think, we'd all know about it here.

Globe Trekker is the new guy on the block so it may be too soon to really know if they have a winning combination. Their posts here imply to me they are heavily invested both financially and emotionally. Custom extrusion dies and mill runs of custom extrusions aren't cheap so they are likely very keen to make an early impact in the industry. I can't say if their youtube videos help or hinder their cause. They certainly have incorporated some new features like the t slot channels into their extrusions and there are enough systems out there that use aluminum bonded to grp that it likely isn't an issue. For me I'd rather have L-track there. The block of uhmw is a great idea to tension the inner and outer extrusions to each other if you're searching for an aluminum to aluminum connection with a broken thermal path. I'd like to see some weight comparison numbers as the extrusions look heavy and I wasn't super impressed with the gallons of sika they pump in their videos to fill voids.

Of note here as I've heard it compared to Boxmanufaktur, from what i can see online, Box bonds their panels directly via dadoed edges and then applies an aluminum top cap and i'm not sure if that is for strength or protection but the boxes seem to be fully intact without the edges installed. So not really the same idea or bond to globe trekker.

So given their history and loyal following I'd have tip the hat to TC for known quality. I'm not saying GT isn't good; we just don't know yet. Given the investment, these habs should be expected to last well over 20yrs. Lets circle back to this conversation in 5-10 years with a few more GT's on the road.

Cost wise from my research a TC 14' cubic box is less than ½ of the GT online numbers. Add shipping, customs, some solar mounts and a brush guard and my math still puts that cheaper than GT.

I saw some comments on cutting windows at the factory - I would avoid this unless you are extremely confident in your final layout.

So long story short, I'm a devil you know kinda guy so my recommendation would be Total Composites based off my own research. Having seen a few in person the panel quality is really good. Far flatter that I was expecting. If they were a pain 5500camperthingy guy certainly would have flamed them, he was brutally honest along the way in all of his videos.

 

[Dave Anderson]

I don't think the foam is an issue at all, but rather the FRP skins. Fiberglass composites that are optimized for strength/weight have a low thermal expansion coefficient in the 7x10-6 range (deg F) vs Al which is ~13x10-6... but I looked up data for Filon and their skins are ~17x10-6... so it looks like a good match is possible if the right skins are chosen. Typical FRP skins have a lot more resin than a high strength layup, and the resin has high expansion, vs glass which is very little. What are you using for the skins?

What are specs on the PIR foam you use, and why was it chosen vs PVC or PU?

I really like the concept of the slotted rail edges... very versatile!

Globe Trekker uses a sheet of FRP inside and out, plus AZDEL as a sub-laminate, inside and out. A total of 1/2" of laminates in a 2.5" thick panel. Thicker AZDEL is on the walking surfaces (floor and roof) and outside walls for better gouge protection. PIR insulation is more dense, so you don't have to add a layer of plywood in the floor to manage the deformation from walking on it. PIR is also has a better R-value insulation, because it is dense. It is also fire resistant, and submergible without soaking up water, unlike PUR insulation. Different colors and body wraps are also not as much a problem, as the FRP laminates don't tend to delaminate since there are also sub-laminates supporting it as well. Check out this video... I did a bunch of testing from my garage... not scientific enough for nerds, but the proof is very apparent none the less. Many blessings!

 

[rruff]

Azdel should be good stuff; it's popular in RVs now. Oddly I can't find any tech specs on it though... like stiffness or strength.
PIR isn't "more dense" than other foams. You can spec pretty much any density you like for PU and PVC, but I think 4 or 5 lb/ft^3 would be most common in this application.
Higher density doesn't improve the R value of foam; rather it drops as you'd expect.

Do you know the density of the foam?
Do you know what the full panel weighs per area?