introducing T-Shell

[T-Shell]

A few years ago I got the dream of building empty camper shells for owners to finish out themselves. There are some options for self-builders now but it looks like there is still room to grow the market.

T-Shell is now open for business. Our purpose is to provide camper shells and materials for the self-build overlanding community. We now offer custom campers as ready-to-mount shells, and also raw composite panels for your own design. At this point, it's just my wife and I operating from our personal shop in Eastern Washington State.

Early on, I recognized that I wanted to build with composite FRP panels. We've completed one prototype with honeycomb core panels and I'm pretty proud of the result. I'll follow-up with a walk thru of the build and design details but here's a shot of our first finished camper. I've seen others announce their big plans and then go too long without progress so I've just lurked on these forums till now and soaking up all your hard-earned knowledge. That's just as well since it's taken a while to get to this point.



Last of all I'd like to thank Mark (@Jeep) from Overland Explorer & Andreas (@Victorian) from Total Composites for sharing so much with the public and potential competitors. You've been a big inspiration to me and are great examples of what makes this community so amazing.

-Karl

 

[T-Shell]

Five panels arrived one cold morning. Each sheet was 7' x 17' and weighed about 200 lbs. The shop space I was using was in an industrial basement with a long icy ramp for access. All I can say is we eventually got them down there without any injuries or damage.



Panels are 2" thick polypropylene honeycomb with fiberglass skins and UV stable gelcoat.


A CNC router table would be nice but cutting panels with a Festool track saw and router is amazingly easy. Similar to working with wood but a lot less cutter load. Everything was designed in CAD so everything was cut-to-print, not cut-to-fit. Cross-checked every setup before cutting because this stuff is too precious to have any spare material.

 

[highwest]

Hey, the pics aren’t showing up for me on iOS.

 

[rruff]

Can't see any pics on the computer either (Firefox).

 

[simple]

The link to their website works and it is a nice site with a lot of info.

 

[T-Shell]

Thanks for the heads-up - should work now. I've attached the pics and it works in all the browsers I could test.
It seems like the BB Code for linked images only works on Chromium browsers.

 

[ITTOG]

I looked at your website for an answer to my question and didn't see it. So, what is the r-value of the honeycomb panels you are using?

 

[rruff]

I looked at your website for an answer to my question and didn't see it. So, what is the r-value of the honeycomb panels you are using?

It's tricky... from what I've been able to find PP honeycomb that is 1" thick has an R value of ~3. Because the cells are so large and extend through the thickness, increasing the thickness doesn't buy you much. The main transfer mechanism is air circulating in the cavity. Not the best choice for insulation.

EDIT: This place has some data: https://www.nidaplast.com/sites/default/files/downloads/COMP_FT_NIDASKIN-POLYESTER_UK_2018.pdf

Heat insulation for 20 mm honeycomb coreR = 0,3 m².°C/W(λ = 0,067 W/(m.°C)) 20mm is .79", US R is .3*5.68= 1.70 or 2.15/inch
Heat insulation for 90 mm honeycomb coreR = 0,6 m².°C/W(λ = 0,14 W/(m.°C)) 90mm is 3.54", US R is .6*5.68= 3.41 or 0.96/inch

I'll take a foam core any day...

 

[simple]

What do you think about their offering of a foam core with 3.5mm honey comb outer layer and fiberglass skins? It seems like the PP layer will take impact and small area pressure loading better than foam. I think of foam being crushed and not bouncing back like plastic. I wonder about long term longevity of foam in high stress areas. It seems like it will get compressed and or turn to dust resulting in a buckle and delam of the outer skin.

 

[rruff]

What do you think about their offering of a foam core with 3.5mm honey comb outer layer and fiberglass skins?

The polyiso foam appears to be the weak stuff, which is why it needs the honeycomb outer layer. The strength specs on PP honeycomb are very good, but the modulus in tensile or compression is about the same as 4lb PVC, so I think cracking of the skin from impact will still occur at about the same time. I'd worry a bit about the polyiso withstanding shear forces and vibration in a structural application. I'd definitely want to see some specs and tests on that foam before buying.

Polyiso has great insulation value at higher temperatures but not the best at low temperatures... something to consider if you will be snow camping.

I bought my PVC foam from these guys. They sell PP honeycomb panels with skins, and the price seems pretty reasonable. 4'x8' 1.5" for $254. If you wanted to buy just panels though you'd probably want larger ones, and always factor shipping into the cost! T-shell may end up being cheaper, and if they have big sheets in stock that's another bonus.

Composite Panels - Sheets - Carbon-Core Corporation

SANDED: ADD $ 0.45 per square foot per side GELCOAT: Fiberglass panels have a T102 pigment mixed in the skins. For regular Gelcoat add $.43 per SqFt. per side, for both sides $.86 SqFt. 40 gelcoat colors available, consult your sales representative for details. OTHER THICKNESSES (UP TO 18″) ARE...

www.carbon-core.com

Specs: https://www.carbon-core.com/pdfs/pds-plastic-honeycomb.pdf

I wonder about long term longevity of foam in high stress areas.

You definitely need to consider it... but 4lb PVC for instance has ~150 psi compressive strength. A 2,000 lb force spread evenly over a 6"x6" area is only 55psi.

If you have really high forces it's best to join the two sides together with a stronger material than foam. Like Total Composites has fiberglass square tubing in the floor at the mounting points.

 

[simple]

Good thoughts. The company producing their panels also makes all the panels for UHaul bodies. I wonder if they have any case study examples showing performance of the polsio foam, pp honeycomb matrix in the field.

 

[rruff]

If it has a long use history that would certainly help inspire confidence.

 

[T-Shell]

You're right - the R-value of honeycomb isn't much but a small volume is pretty easy to heat/cool as long as it's weather-tight. I've been told it's similar to wood, between R-1 and R-2 per inch, but the non-linear explanation by @rruff seems the most reasonable. I'd take foam for four-season camping too but you can't beat honeycomb for toughness and durability.

Like @simple noticed, we also offer foam core clad with 3.5mm of HC on both faces. The polyiso comes recommended by the manufacturer but I have not been able to do any testing yet. I have much higher expectations for this than any foam panel I've seen without the HC layers. I currently only have polyiso listed but we can get nearly any high-melt-point foam (i.e. not XPS) you're willing to pay for. EDIT: Removed for further testing.

The goal with any composite panel design is to spread the loads out over as large an area as possible. I'll show pictures later, but this design puts all the concentrated loads at the edges thru the structural angle, with steel inserts at the tie-downs.

U-Haul panels don't use any foam that I know of, mostly fiberglass clad plywood. Their bodies use the panels like traditional truck skins, attached to reinforcing ribs.

-Karl

 

[rruff]

For anyone thinking about PP panels, I'm pretty sure that's what Everlanders used, so you might get some insights from them: https://www.youtube.com/channel/UC76GYXW3j9z5g3OdW--Sf5g

Also the oldie but goodie, Super Camper on a Tacoma: https://www.google.com/search?q=The...&ved=0ahUKEwjI9ITth5XwAhVPmK0KHQ8PABkQ4dUDCA0

 

[SDDiver5]

Make one for that firetruck/brush truck in the background of the first pic. That would be killer!