DIY EarthRoamer (sorta)... newbie questions

[ReluctantTraveler]

I was referring to how the back end of a long bus moves when the bus is turned. The long overhang allows a shorter wheelbase for a given length vehicle (which is great for twisting narrow neighborhood streets), but does require the driver to be aware of how the back of the vehicle moves.

For sure! The tail will swing out a bit and all that. Can lead to some dicey situations.

 

[ReluctantTraveler]

I don't know if you are already there, or still figuring out just what can be done with adhesives rather than relying on mechanical bolts and screws, but, in case you aren't there yet, I'm trying to get you there, because it will really help with the big picture!

i’m still trying to wrap my head around just how much load you can support like that.

I wanted to have some mounts on the back for bikes, snowboards, and such. I’m having a tough time believing that adhesives alone could support that kind of load.

my understanding with this approach is that you create a skeleton out of 2x2s, place rigid 2” foam in it, then sandwich it with thing plywood and coat with epoxy?

I know I’m the one who mentioned wood from the start, but is building with structural fiberglass panels functionally the same thing? It feels like you need a lot of support under the cab over bunk to keep it from flexing.

 

[rruff]

I wanted to have some mounts on the back for bikes, snowboards, and such. I’m having a tough time believing that adhesives alone could support that kind of load.

The adhesive isn't an issue if you do it right. The weak point is usually the foam core. If there is only foam in the core, you need to spread the load over a larger area using a stiff "doubler". You also need to have an excellent bond between the skins and foam. You can put solid material in the core also that joins the two skins together. I mentioned using wood slats, which works very well IME. I built a camper like this 21 years ago and it turned out great. Spacing was 16" I think.

Rather than build a skeleton it's better to make flat panels, then join the panels together. This way you can get a good bond between the skins and core... hard to do that around a skeleton. Everything needs to be bonded well... any gaps will be weak points and the skin will bubble.

The cab over bunk will not be an issue with this sort of construction. A 2" core with 1.5-2mm fiberglass skins will be plenty rigid, and very strong.

I used 2.7mm luan skins on the build I mentioned above, with an external wet-laid fiberglass coat. Even though I haven't used them, the fiberglass+gelcoat sheets you can buy, which are made specifically for this purpose, seem like the best way to go. Some people on this site have purchased from this company:

Production of GRP laminates - Vetroresina Spa

Vetroresina produces a wide range of fiberglass reinforced plastic panels and laminates also in customized versions. Discover all our GRP laminates.

www.vetroresina.com

https://www.vetroresina.com/media/uploads/allegati/4/us-20042020-matstuoia.pdf

 

[rruff]

DIY Spotlight: Ian Azariah's 'Mobile Dojo' Wooden Truck Topper

When it comes to truck camper construction, wood gets a bad rap. That's too bad because when it comes to wood nothing is more beautiful. The key to wood

www.truckcamperadventure.com

Build-your-own Teardrop Camper Kit and Plans

Stitch and glue refers to using wire (typically) stitching to join edges of plywood together, then fill the joint with thickened epoxy, following up with wet-laid fiberglass on both sides of the joint, and usually over the whole exterior. The rigidity of the structure relies on curved surfaces... flat pieces of plywood that size and thickness would be very floppy.

The truck camper you linked is wood, and probably glued, but is a totally different concept. The teardrop is good example.

 

[IdaSHO]

For what its worth...

Ours is a 7'x14' unit, essentially a 10' cabover camper. Shell itself weighed right about 700#
Been on the road now for 10 years. And looking and performing better than ever.

Fair warning. This method isnt for everyone. It labor intensive, and if you do not mind your weights,
you will be HEAVY. If I were to do it again, Id loose some of the framing as well as drop to a 4mm okoume.
It works great as is, and is absolutely bomb proof, but I feel I could save a bit of weight and cost otherwise.

I drew the entire thing up in Google Sketchup and constructed using the following:

1.5 x 1.5 12ga square steel tube base
Framed with VG fir 1x2's all joints wet set with PL premium and pocket screws
Skinned with 6mm BS1088 okoume using PL premium and stainless brads
Wall cavities filled with XPS foam, tight fit, glued with PL premium
Interior skinned with 2mm birch ply using pl premium and stainless brads
Exterior joints glassed, entire exterior saturated with CPES, alkyd primer, alkyd industrial enamel top coat (recently color change using Monstaliner)
Interior epoxy painted then finish painted with Marine Topside paint

A few photos below... and feel free to snoop in my Flickr that hosts the photos.

 

[ReluctantTraveler]

The adhesive isn't an issue if you do it right. The weak point is usually the foam core. If there is only foam in the core, you need to spread the load over a larger area using a stiff "doubler". You also need to have an excellent bond between the skins and foam. You can put solid material in the core also that joins the two skins together. I mentioned using wood slats, which works very well IME. I built a camper like this 21 years ago and it turned out great. Spacing was 16" I think.

i’m a visual guy and I’m having a tough time picturing this in my head. You don’t happen to have any photos of what it looks like, do you?

 

[ReluctantTraveler]

For what its worth...

Ours is a 7'x14' unit, essentially a 10' cabover camper. Shell itself weighed right about 700#
Been on the road now for 10 years. And looking and performing better than ever.

DUDE! I’m so grateful you replied. Your build is very close to what I wanted for my own (with a few modifications based on family needs).

From looking at the pictures, it looks like you built a wood frame, filled the gaps with tight fitted solid foam, laminated the interior and exterior with a thin material (fiberglass or polywood), and then use a fiberglass and a epoxy coat over the entire thing to waterproof?

For any exterior mounted items, did you mount directly into the wooden frame and then waterproof the seals?

and if you’ll allow me one more question: what are you using as a truck for your base? It looks like you actually have a short wheelbase on yours with an 10 foot floor?

well I recognize this is very labor-intensive, it fits squarely in my skill set, and feels much more achievable then a more “perfect approachusing composite panels.

 

[ReluctantTraveler]

@IdaSHO I just realize that 14 foot length includes the cab over. That’s not the floor length.

Also, is 700lbs the shell weight, or the weight with all of the internals (fridge, bath, etc)?

 

[rruff]

i’m a visual guy and I’m having a tough time picturing this in my head. You don’t happen to have any photos of what it looks like, do you?

No, sorry. What exactly are you wondering about, how the core looks? It sorta looks like stick framing only with XPS foam in the gaps. For instance, 1x boards (3/4" deep) cut to the same thickness as the foam, and on edge. Could use 2x (1.5") also. Space them however you like; mine was 12"-16". Glue the slats to the foam. Top, bottom, and side edges would be wood also. Then glue on the skins.

IME texturing the foam with a wallpaper roller and really working the glue in before bonding, is a good way to do it. One note about hardware foam is that the thickness tolerances aren't great. Check that, and be sure to buy all the foam for one panel that is the same thickness. Then cut the slats to match... try to be precise so your panel will be flat and bonded well.

 

[IdaSHO]

yes, 700# for shell only. Complete dry weight as it sits is about 2200#
Wet and loaded, its a bit more than 3000#

---

There are very few penetrations in the exterior (by design)

The exterior grab handle is the only item that is fastened to framing, as it needs a ton of strength to prevent pull-out.
The rear eye-bolts and the front under cabo-over eyes are bolted thru the body, with stainless hardware and rubber washers for seals.
The rest, the solar panel mounts, the roof hatch, lights, etc are all simply fastened to the 6mm ply skin. All are gasketed, some have a bit of silicone.

Truck is a 2011 superduty. Its a heavy-spec F250 (10kGVWR) We still run overweight, (near 12k fully loaded with gear, two adults and two dogs) but it does great.
Extended cab, long bed. I stretched the frame 24" to allow for the 24" x full width cross body box, while maintaining an 8' bed.
I also built the bed, complete with said cross body box, 3-point torsion free subframe, integrated stairs, under bed stowage, etc, etc...

 

[ReluctantTraveler]

No, sorry. What exactly are you wondering about, how the core looks? It sorta looks like stick framing only with XPS foam in the gaps. For instance, 1x boards (3/4" deep) cut to the same thickness as the foam, and on edge. Could use 2x (1.5") also. Space them however you like; mine was 12"-16". Glue the slats to the foam. Top, bottom, and side edges would be wood also. Then glue on the skins.

IME texturing the foam with a wallpaper roller and really working the glue in before bonding, is a good way to do it. One note about hardware foam is that the thickness tolerances aren't great. Check that, and be sure to buy all the foam for one panel that is the same thickness. Then cut the slats to match... try to be precise so your panel will be flat and bonded well.

that’s helps a lot, thanks!

What’s the benefit to building the panels and bonding vs. using rigid foam into a framed skeleton? The end result seems identical.

 

[ReluctantTraveler]

and feel free to snoop in my Flickr that hosts the photos.

Do you have a link to your Flickr account? I can't work out how to snag your username or album ID from the deep-linked photos.

 

[IdaSHO]

Oops….

Try this

idacamper2.0

Explore this photo album by Kenny Bonnefin on Flickr!

www.flickr.com

 

[ITTOG]

Oops….

Try this

idacamper2.0

Explore this photo album by Kenny Bonnefin on Flickr!

www.flickr.com

Whattdid you use to fill the tubing? I don't know of any product that would fill end to end without filling in the middle as well.

 

[IdaSHO]

I used a Frothpal foam kit

Multiple holes drilled, entire steel frame section is filled with foam.
Only reason was an attempt to avoid condensation build up inside the tubing in order to prevent rust/rot.
It has proven effective best I can tell.

Category Page

www.greatstuff.dupont.com