Do it your self Fiberglass Extrusions by Total Composites

[highwest]

It's gelcoat as stated... ie polyester resin I suppose; standard stuff.

Curious why you'd want to fiberglass over these joints?

Gel coat is usually applied over a fiberglass and is not structural, only cosmetic. In this case, it seems like the gel coat might be mixed in to the whole extrusion..? I don’t know... In any case, it’s preferred to bond epoxy to polyester or epoxy, not gel coat.

To further spitball the conversation on XPS, I’m curious about adhering these extrusions to XPS panels and then, more or less, glassing over the whole structure. This way you wouldn’t have to trim the XPS at all.

 

[rruff]

Gel coat is usually applied over a fiberglass and is not structural, only cosmetic.

Gelcoat *is* polyester resin... with pigment and UV inhibitors. It's probably about as strong as the resin is.

I don't understand why you'd want to construct a camper that way, though. Joining the foam pieces is very easy. Then you can round the outer edges with a surform tool and the inner edges with filler. And you can reinforce the edges as much as you'd like with wet layup. The sharper edges on these extrusions would make it more difficult rather than easy, I think.

I'd advise laying your panels flat and glassing them, then joining and glassing the edges... at least for the interior surfaces. Don't build the box out of foam first. It's hard to get good adhesion to XPS in the first place without working on vertical surfaces... or worse, upside down!

I thought "layup" was a fiberglassing term? If not, then I don't know what it means.

Heck, I don't know? I'd call PMF wet layup as well since it uses the same method, just different materials... vs getting skins already made and gluing them to foam, like TC does.

 

[highwest]

I don't understand why you'd want to construct a camper that way, though.

Corners. If one can avoid glassing around corners, then you only need to worry about glassing flat surfaces. This also allows use of a heavier cloth. XPS needs all the help it can get, right? Then skip all the rounding of outside corners and filling of inside corners.

I have not glassed XPS before, but I agree that working on the horizontal is much easier. The build plan could be worked around this as much as possible.

Good thoughts.

 

[Peter_n_Margaret]

I saw videos of Styromax (another Oz company) building joints like that, and like Victorian mentioned, thought "no way in hell is that a strong joint!" The strength is in the skins and the glue contact skin-skin is very little.

But... if you make a completely torsion free subframe and reinforce edges with internal structure, and use the right glue, then it apparently works! Seems a bit crazy to me, but the proof is always in the result.

Couldn't you make any angle you wish using that method? With CNC it should be easy. Also, what glue did you use?

I used Sikaflex 252 (along with the appropriate cleaner and primer). Others are probably just as good.
The use of aluminium corner reinforcements requires a consideration of differential expansion between the aluminium and the FRP skins and that effects the thickness of the glue joint. That is not required if the corner reinforcements are hand laid up or are FRP extrusions.

I suggest that closed cell polyurethane foam is superior to EPS both structurally and in terms of its insulation qualities.
Some urethane foams are "drilled" with 1mm holes allowing resin to create tiny pillars joining the outer skins when it is vacuum bagged wet-on-wet. This creates a panel that is far superior to that made by simply gluing pre-made skins to sheets of foam. The skins are also typically thinner and lighter with no risk of delamination.

This is a camper made by a friend.
The sandwich panel was made wet on wet and vacuum bagged on his shed floor (14 years ago). The corners are all hand formed and laid. The foam is closed cell polyurethane. The floor is glued to rubber pads which are in turn glued to the chassis direct. There is no steel sub frame. The body is stiffer than the chassis. The outer is painted with 2 pack paint after completion. All the interior "furniture" is also sandwich panel and part of the structure.
Despite appearances it is actually a Defender.
His effort, skill and finish puts mine to shame.

Cheers,
Peter
OKA196 motorhome

 

[rruff]

Corners. If one can avoid glassing around corners, then you only need to worry about glassing flat surfaces. This also allows use of a heavier cloth. XPS needs all the help it can get, right? Then skip all the rounding of outside corners and filling of inside corners.

That part is easy IMO. You can create a 2" radius on 2" thick foam which is way more than enough. Good for aero, too! And good for holding up to tree branches and such. You can use heavy cloth on that with no worries. A corner will be more difficult, which is why I'd recommend light and very conforming cloth there, but those are small spots, and with good rounding, not bad at all. The inside edges aren't hard either... mix up a batch of epoxy and fumed silica, glop it in, and smooth it with a rounded spatula.

BTW, Volan treated cloth tends to be very soft and conforming (for corners).

Some urethane foams are "drilled" with 1mm holes allowing resin to create tiny pillars joining the outer skins when it is vacuum bagged wet-on-wet.

That would make a very solid core. Your friend's camper is very nice as well. Thanks for the info, Peter!

Getting back on topic... I think it's great that TC is making these extrusions available. It should be a big benefit for people constructing a camper using sandwich panels.

 

[Louisd75]

@Victorian Have you guys looked at doing thinner composite panels? Say, 1"? I think that using the same composite panels as the bulkheads would be a bit overkill for fitting out the inside with, but I see it mentioned above.

 

[jwiereng]

@Victorian Please show photos of what you offer for joining 90x90x90 corners and 90x90x45 corners.

 

[skirunman]

@Victorian Have you guys looked at doing thinner composite panels? Say, 1"? I think that using the same composite panels as the bulkheads would be a bit overkill for fitting out the inside with, but I see it mentioned above.

I believe TC does offer FRP composite panels for internal buildout in 1" thickness, both foam and honeycomb polyethylene cores. Probably best to contact them directly for details https://totalcomposites.com/contact/

 

[jwiereng]

@Victorian Please show photos of what you offer for joining 90x90x90 corners and 90x90x45 corners.

bump

 

[Peter_n_Margaret]

I believe TC does offer FRP composite panels for internal buildout in 1" thickness, both foam and honeycomb polyethylene cores.

I have used honeycomb polyethylene cored panel and I would not choose to use it again. It was a tad heavier than foam core and a tad cheaper (and that is why I bought it), but when cut it exposes an edge made up of large voids so adding a bench top edge trim (for example) burns vast quantities of adhesive. It also lets the light through (if that is an issue) and has very poor insulation qualities. Foam core is easier and better to work with.
Our supplier in Oz is supplying 12mm foam core panel as an interior option.
Cheers,
Peter
OKA196 motorhome

 

[Snowboard.wa]

The floor is glued to rubber pads which are in turn glued to the chassis direct. There is no steel sub frame. The body is stiffer than the chassis.Cheers,PeterOKA196 motorhome

This is really interesting. I was just thinking of the different ways you could attach a custom box/camper to a bed deleted truck frame. Never would have thought to do it this way. One obvious benefit would be that you would inherently have a protective waterproof layer in the rubber as well. Sounds like a lot of work to fabricate, but impressive nonetheless.


Sent from my iPhone using Tapatalk

 

[Peter_n_Margaret]

This is really interesting. I was just thinking of the different ways you could attach a custom box/camper to a bed deleted truck frame. Never would have thought to do it this way. One obvious benefit would be that you would inherently have a protective waterproof layer in the rubber as well. Sounds like a lot of work to fabricate, but impressive nonetheless.

Be careful attempting this with on a chassis that is more flexible (and that is "most").
Cheers,
Peter
OKA196 motorhome

 

[vintageracer]

Concerning vehicle chassis flex as it relates to foam core panel boxes brings forth this question that I have that is a little off subject however I would think would be a major design element when constructing a foam core box:

How effective would it be to add multiple say 6 inch boxing plates along the length of a C channel chassis/frame from the vehicle cowl back at specific points along the chassis to add rigidity to the frame for less chassis flex (not eliminating) while still providing access to wiring, brake lines of other items run through/along the frame rails on a vehicle upon which you will mount your foam core box?

 

[rruff]

...for less chassis flex (not eliminating)

If you box half of it, it will be about half the flex. But I don't think that will save you. HD trucks with open C frames flex a huge amount. Ram5500 Camperthing posted a video recently of a test on his truck, and he picked up one of the rear wheels ~2ft and the suspension barely moved. It was all frame twist. Reducing that to 1ft wouldn't be enough I think.

Newer domestic pickups up to 1 ton all have a fully boxed frame that is very stiff. For most on and off road running I think this is superior, although a flexible frame will keep all its wheels on the ground when crossed up and a stiff frame usually won't... you need a suspension that really articulates with a stiff frame.

 

[Victorian]

The endless topic of subframes... LOL
If you go off road and your truck is subject to twisting, you need to isolate that frame flex from your camper, no matter of the camper material. You will at least get mis alignment issues with your cabinetry, windows, doors... Worst case: your truck or camper will be severely damaged. I have seen camper bodies manufactured by a well known US Expo truck builder that had the floor ripped away from the body as there was not enough flex in the subframe. I have also seen subframes stripped from the floor panel by the same manufacturer. Therefore, please do your self a favour and consult with someone that has a PROVEN track record. There are simply too many people out there making things up...