Foamie Jeep Camper Hardtop

[redveloce]

Here's my latest concept for the layout of the camper top. The colors are just for contrast.

Top down


Top popped up. The rear of the top portion folds down to become the foot area of the bunks. This allows the top to be within the Jeep's footprint when retracted.

[redveloce]

I've been doing some experiments with different skin and glue materials to help determine what I want to use.

Cloth/Denim
I used some denim (what I had laying around) with Glidden Gripper, and I'm not sure that I'm comfortable with the result. I fully encased a small section of 1" thick Foamular 250 foam in the denim, using the gripper as a resin, and squeegeed it like I would with a fiberglass lay up, but after a couple weeks it still didn't seem completely cured. It stayed in a heated 70 degree room, and felt dry to the touch, but still smelled 'wet' (to me). It was somewhat stiff, but I could still bend and crease the foam by hand without a huge amount of effort. I had no trouble peeling the denim from the foam. It did pull some foam in a couple small spots, but mostly the Gripper just separated from its self.

ABS Plastic
I enjoy working with plastic, so I have quite a few ABS scraps laying around to play with. I was curious about the possibility of bonding ABS to the Foamular 250, so I did a bit of research into glues without finding anything with which I was really comfortable. Finally I was playing around with the chemical resistance of the foam, and noticed that lacquer thinner only melts the foam while the thinner is actually present in liquid form; once the thinner has evaporated, the foam will stay melted for a relatively long working period before eventually solidifying to a plastic. With this in mind, I soaked a rag in thinner, just so the rag was moist but not dripping wet, and wiped the surface of a test scrap of foam. This caused a thin layer of the surface to melt, but no deformation or holes. I then pressed a small scrap sheet of ABS onto the surface of the foam. The plastic became nearly impossible to remove after only a few seconds, without even having sanded the ABS first! Trying to pry the plastic from the foam, it would slowly 'goo' off of the foam with quite a bit of effort while the foam was still melted, but once it set up, there was no way to remove the abs without destroying the foam! Just covering one side of the foam with 1/16" ABS sheet made it very strong and stiff. The material is about $36 for a 4x8" sheet, so I'm considering using this for my external skin, and possibly something different for the interior.

Some additional advantages of the ABS, are that it can be heat formed around corners to provide much greater stiffness, and it is possible to strategically reinforce the attachment with screws into the foam.

Burlap
I picked up a couple yards of nice burlap this weekend for somewhere around $2/yard. It's VERY strong, and (unlike the denim) I cannot tear it by hand as hard as I try! I'm going to experiment with the burlap and Glidden Gripper. I think that the more open nature of the burlap weave may help the Gripper cure. If this works out, I may use it for the interior panels, and possibly larger exterior panels like the center of the roof.

StyroSpray 1000
I did some research into StyroSpray 1000 from Industrial Polymers, and eventually had them send me some samples. I'm impressed by the toughness of the material, and the tenacity of the hold on the foam sample, but according to the rep, it would take 4 gallons to achieve the thickness of the samples on my application. I was able to tear it, and it does seem to have a little bit of stretch, but not really much. The one thing that may worry me is that I was able to get the material to crack with relatively little effort by flexing it multiple times. I would worry that the slightly flexible nature may allow it to flex enough to eventually develop stress cracks over time. This combined with the price makes me rule it out as a primary coating material, but there may be a few places on the build, such as the doorjambs, where it could be useful.

[KCStudly]

I soaked a rag in thinner, just so the rag was moist but not dripping wet, and wiped the surface of a test scrap of foam. This caused a thin layer of the surface to melt, but no deformation or holes. I then pressed a small scrap sheet of ABS onto the surface of the foam. The plastic became nearly impossible to remove after only a few seconds, without even having sanded the ABS first! Trying to pry the plastic from the foam, it would slowly 'goo' off of the foam with quite a bit of effort while the foam was still melted, but once it set up, there was no way to remove the abs without destroying the foam!

Very interesting. Do you think that you can scale that process up to 4x10 and still achieve uniform results in the allotted time required to get a whole wall or roof wetted and covered? How about the initial tack; is there any forgiveness for initial placement of the panel, or do you have to get it right on the first go?

[redveloce]

Very interesting. Do you think that you can scale that process up to 4x10 and still achieve uniform results in the allotted time required to get a whole wall or roof wetted and covered? How about the initial tack; is there any forgiveness for initial placement of the panel, or do you have to get it right on the first go?

I'm thinking so, but I won't know for sure until I do some more testing. I'm going to try using a kitchen sponge as an applicator, and if that works, then I imagine you could use a sponge mop on really large panels. I only played with it for around 5 minutes initially, so I know it stays wet for at least that long. I'll have to apply some and time how long it takes to dry. Initial tack is pretty strong. I think you could move a panel if only a small part had touched, but once it's down you'd have a really hard time removing it. One advantage of the thinner 1/16" ABS sheet ends up working would be that it's would be flexible enough to line up an edge, and 'roll' it onto the foam. This could possibly allow you to wet it out as you go if working time turns out to be an issue.

The process I'm thinking about is kind of backwards from a normal foamy. I'm going to try making the panel first, then cut the foam to exact size, so it can be wetted and pressed into the panel. The next step will be some durability testing. I'm going to make up a panel at least 1 sq/ft, wait for it to harden completely, then shoot it with my pellet gun to be sure it wouldn't pop off with a rock impact. I'll likely use strategically placed screws to reinforce the panel application in the final project, even if it passes this test.

[atahoekid]

Instead of wiping/mopping it on, could you spray it on evenly and thinly enough. Maybe using a garden sprayer or something similar? Intriguing idea... most of the best ideas come about because someone is willing to experiment. Can you answer a few questions for a plastic newbie. Where can you buy ABS plastic and is there another name we would know it by, what is this type of ABS normally used for?

[KCStudly]

And what size sheets does it typically come in? Can we get 4x10?

[redveloce]

Instead of wiping/mopping it on, could you spray it on evenly and thinly enough. Maybe using a garden sprayer or something similar? Intriguing idea... most of the best ideas come about because someone is willing to experiment. Can you answer a few questions for a plastic newbie. Where can you buy ABS plastic and is there another name we would know it by, what is this type of ABS normally used for?

It's possible, but the reason why I used a rag for my test is to prevent the lacquer thinner from actually sitting on the foam. It will continue to eat the foam as long as it is in contact, so by this method I was able limit the contact to the time the rag was in contact with the foam, and a very small period of residual evaporation time. I would be afraid that even a fine spray would pit the foam unevenly where any droplets landed, and anywhere that had a larger amount land would be eaten deeper until that had evaporated. The effect I got using the rag was basically like a thin layer of glue.

More experimentation is definitely necessary to be sure I can replicate the results!

Tap Plastics is my local supplier
http://www.tapplastics.com

I'm not aware of any other name for it.

From Wikipedia: "Acrylonitrile butadiene styrene is a common thermoplastic. Its glass transition temperature is approximately 105 °C. It is a terpolymer made by polymerizing styrene and acrylonitrile in the presence of polybutadiene."

The majority of plastic used in cars is ABS plastic. It's also used to make a huge number of different products from boats to black plastic water pipes.

And what size sheets does it typically come in? Can we get 4x10?

4x8' is the largest size that Tap Plastics can get. I don't know about whether other sources can get larger sheets or not.
I just checked the price for a 4x8' sheet of 1/16" ABS, and it's nearly doubled! I still don't think it's that bad even costing $60 though...

[Bogo]

Instead of wiping/mopping it on, could you spray it on evenly and thinly enough. Maybe using a garden sprayer or something similar?

I was thinking paint sprayer turned down low with fast strokes.

I'm not sure about using ABS on the outside due to desert heat. It's normally only given a use range up to 176F. Vehicle skin temperatures can get up to 225F. It's "glass transition temperature" for thermal forming is around 221F. It also needs UV protection as it is degraded by UV light. The fluorine based plastics are much better at handling UV, but cost more. I don't know how well a UV stabilized ABS would last. If it was garaged between trips it would last allot longer.

My thoughts on panels is to make them using vacuum bagging with aluminum or FRP skins. You can get pre painted aluminum and fiberglass skins, but it isn't hard to paint them yourself. Just pay attention to what needs to be done for surface preparation before priming and painting. You can also make your own skins with the vacuum bagging equipment. When you do that you can gel coat them whatever color you want, stiffen them up in some areas and make them thinner in other areas. Once a panel is made, a router with a carbide bit can be used to cut it to shape. You'll want a sacrifice surface below it to allow the router to cut fully through the panel. a 1/4" sheet of plywood or foam would do.

[redveloce]

FRP skins are an interesting idea, I hadn't thought of that. Most of what I can find online seem to be from places like Home Depot. The prices are pretty good, but they all seem to say they're not for exterior use. Not sure what ill effects there would be if you used them on an exterior though.

I'm attracted to the relative indestructibility of ABS. I'm not sure if the material from Tap Plastics has a UV stabilizer added, but I've used it on the outside of my vehicle for several years without any signs of degradation or fading. It's definitely worth doing some experiments with the desert heat. I suppose the easiest thing to do would be just to leave a sample sitting in direct sunlight through a hot day, and check it during the hottest part of the day to see if it is soft? ABS can be painted, so that may be the solution to both the heat and UV susceptibility.

I'm set up to work plastic, but not fiberglass or painting (other than from a spray can). I'll see what I can figure out to test the fine mist idea, unless someone else who has the equipment wants to give it a try?

[Bogo]

On FRP panels. I've been looking a construction method that should be mostly able to be done at home with common tools plus a vacuum bagging setup. Boxy with angle iron corners. The curved angles would likely need to be made by somebody else, and the exterior frame welding is also an outside job.

There is an overall angle iron frame on the outside made from aluminum, then the panels are glued to it. After the panels are glued in place, then the corners are filed with expanding foam, and angle irons are fitted to the insides and glued in place. That ties the inside skins together. The back on this hard sided pop up off road vehicle is built using this technique: http://forum.ih8mud.com/expedition-builds/245430-travelling-cruisers.html There are some shots of its construction starting around post 61. Here is a part of a post I made in that thread showing a cross section of a corner for a hard sided pop-up.

Effectively the frame of his is rounded corner AL angle irons welded at the corners with panels glued into them to make the sides. The panels are pre-made composite panels.


This is a quick detail for the box corner I designed showing both the lifting top and the base in a 3D cross section. Lifting top has the curved corner for the outside and a angle iron for the inside. The base has both inside and out as angle irons. The red pieces are delrin plastic glides, and likely need to be thinner to prevent binding. The panels are 1" thick AL/foam/AL composite panels. Their skins will be on the order of .032" thick. The outside curved corner can be formed from a 1/8" thick sheet AL plate. No need for a custom extrusion of that shape. The panels will be glued to the outside corner pieces first. Then the inside corner angle irons will be glued in place to finish off the corner. The inside angle irons are not welded to the frame. They are only glued in place.

I've been looking into making fittings for the corners of the outer frame so that I can glue and rivet the angles together at the corners instead of welding them. I don't have the needed welding equipment. Also the above cross section is for an off road vehicle. It is using 0.125" thick angles in the corners. I figure 0.080" or 0.100" would do fine for a TTT.

The angles can be bent onto long arcing curves, but that obviously takes some metal working. It can be done at home with the right hammers, and anvil, a leather sandbag, and a torch to anneal the metal. For annealing get some means to read the temperature like an IR thermometer, or those temperature indicating wax pencils. You need to know when the aluminum is up to temperature to get it properly annealed without overheating it and destroying the alloy's properties.

Angle iron corners with a 1" to 3" radius curve instead of the tight 90 degree angle can be made on a slip roll, but you need a long enough one and that machine costs $$$. It would likely require having that done by a fabrication house, but it can be done. There is also the possibility of doing it yourself with multiple uses of a press and some forms, but it would take some trial and error to get it right.

The other technique is to go with fiberglassed corners. A few layers of fiberglass would be laid up over the corners and edges. Much messier. and lots more fumes.

[Wobbly Wheels]

FRP skins...all seem to say they're not for exterior use. Not sure what ill effects there would be if you used them on an exterior though.

They probably use an ortho ('general purpose') resin in the gelcoat (or no gel at all) because it's quite a bit cheaper than using vinylester resins the way you do in the outer layers on a boat hull.
Nothing a coat of paint won't seal.

[Bogo]

FRP skins...all seem to say they're not for exterior use. Not sure what ill effects there would be if you used them on an exterior though.

They probably use an ortho ('general purpose') resin in the gelcoat (or no gel at all) because it's quite a bit cheaper than using vinylester resins the way you do in the outer layers on a boat hull.
Nothing a coat of paint won't seal.

Also allot of these sheets are thermal set resins. That way they can mass produce them in a reasonable period of time. BTW, everything that is pulltruded is thermal set. It needs to be set hard enough to be pulled on by the time it leaves the forming die.

[redveloce]

A quick note. I realized last night that I was mistaken about the chemical. I had somehow thought I used lacquer thinner, but it was actually 'Goof Off'. I guess that's what happens when you do this stuff when you're tired... I tried lacquer thinner last night, and it does melt the foam, but it makes it slick and hard instead of sticky. So it looks like I'll need to see how much a larger bottle of goof off would cost, or find something less expensive with the same active ingredient.

BTW, I stopped into Tap Plastics last night, and discussed the concept with them, and they said it is actually chemically bonding the to styrene based plastics into one plastic.

[Junkboy999]

Bogo

Hey I just gave that other forum a look. Wow that is a kool looking rig. I Hate all the Ads on every single post.
That does look like most of if can be made at home. I might have to make a little mock up foam and FRP panel test.
I think even the corners can be rolled at home if you make a die set for a cheap metal forming machine. Not sure
how you would cap the three corners where they come together.

So is that what gave you the idea of making a Triple pop-up camper in your other thread?

[Bogo]

I think even the corners can be rolled at home if you make a die set for a cheap metal forming machine. Not sure
how you would cap the three corners where they come together.

For the corners where the edges come together, I was thinking of making a male/female mold pair, then pressing them with a 40 ton press. The other possibility is to just hammer then out of a flat sheet.

So is that what gave you the idea of making a Triple pop-up camper in your other thread?

Partially. I'd thought of doing a hard sided pop-up before, but was thinking along different lines. I was thinking of hard sides that would fold down, and not of the box that lifts.