Thrifty Alternatives ..Building Foam Campers

[starleen2]

it happened to davel on the Bluebonnet II build. His was a foam core covered with fiberglass cloth and epoxy resin - on some places it did bubble.

[GPW]

One reason to paint it White or a light color ... Our Southern sun is Very Hot , and any dark color really turns up the heat on the materials used ... The black areas on my Camo job get so hot they will give you a 3rd degree burn ... ask me how I know ...
That , and the perforated foam should solve this problem ... better attachment , less Heat ...

Another consideration is Moisture under the glass , glassing is best done on a DRY day , on a DRY, Clean surface ...

[Wolffarmer]

The big reason I am interested in the Bolus look is for aerodynamics. I pull with small TVs and pulling into a wind will prove to a person just how much the drag is. But maybe instead of a curvy hard to make Bolus type, this might be a way to go.

Facetmobile

It worked pretty good, until a motor malfunction crashed it at the airport I dive pass most days to and from work.

Might not look as cool as the Bolus but work better than a blunt face. At least until I can convince the rest of the world to drive slower.

Randy

[mezmo]

Hi Wolffarmer,

Thanks for posting that link. That little airplane is very interesting.

Cheers,
Norm/mezmo

[GPW]

Wolf, already built one , out of Foam ... Flew OK...

[mikeschn]

Hey guys,

I'm still reviewing the canvas and glue vs the fiberglass and epoxy.

Just for the heck of it, I went out and checked the adhesion...

It peeled right off. No resistance whatsoever...



Mike...

[eaglesdare]

is that the glue/canvas or the fiberglass/epoxy? and is that laid on one flat piece?

if so, not saying the answer was yes, but if so, don't forget the idea is to wrap the foam, plus overlapping on the corners and roof, bottom etc.
lay a sock on your foot, then shake your foot, that sock might slide off, yes? now put your foot into the sock and shake it, its not falling off.

i hope that made sense.

[mikeschn]

Louella,

That's canvas and titebondII on the left. 2 part epoxy resin and fiberglass on the right.

Correct, at the point it is not bent over anything. But what we are trying to prevent is bubbling of the cloth in the hot sun. The guy at the epoxy place told us that epoxy resin and fiberglass cloth will delaminate and bubble in the hot sun.

We don't want the canvas and glue to delaminate in the hot sun, hence the testing.

I am currently in the garage, testing myriad samples. But today I am using bedsheet, like GPW did, instead of canvas.

I'm testing on wood and foam...

And I am testing
1 part epoxy paint
exterior latex paint
2 part epoxy resin
titebond III

Mike...

[eaglesdare]

oh so this is the bubbling effect testing? ok, i will have to go out and check mine. never thought that my canvas would do anything in this sun.

would it make a difference if its covered with a tarp? or just straight out right in the sun?

[Conedodger]

Mike:

So far in all my testing I have yet to get TB2 to stick to just foam, and in the same way as your test it does not stick, but should we be suprised, NO. TB2 spec says it will only join porous items and foam is not at all porous.

In the same tests mine came off with little effort but over a large area it does stick a bit, Not sure how, maybe by filling the holes in the foam surface but the join has very little strength.

However if you use TB2 to cover the foam but stick to anything porous such as wood or more cloth (The floor, spars Etc) it will stick and as such hold the foam. Try a peice of foam inside two peices of wood and you will be suprised. To get any real strength you have to do both sides and sort of wrap the whole chunk of foam. Also the more parts you use that are porous the better.

TD2 is not a structual glue, once it moves it has no strength.

As to epoxy, its better than TB2/Cloth, several people have made epoxy / foam campers and they have been fine but they have used several layers of cloth to give strength and the strength is not epoxy to foam, its epoxy to more epoxy. The foam just holds the layer in place but its the layers of epoxy and cloth thats gives it the strength. Its all about wrapping not covering.

Think of it this way. Even if you made a perfect join between foam and anything, it would still come apart as the foam is not super strong. Wrap it and the foam is held in place and the whole thing becomes strong.

I have yet to have delamination of epoxy to epoxy but i would not trust epoxy to foam unless the epoxy wrapped the foam and as such spread the stress.

GPW and Eagles idea was taken from how old Kayak's were made and that was just cloth pulled between spars with some sort of liquid coating that went hard and waterproof. I think of it as early plane wings. In our case the foam is there to hold the cloth and coating in place, but the strength is the cloth and coating. Yes, spread over a large area of a whole panel of foam would add a bit of strength but its the whole combination that becomes strong. Delamination starts at an outside edge but if the whole thing is wrapped there is no edge so it stays together.

I have found its difficult to test little bits as they all fail, but as a whole it seems to work.

Wrap a piece of foam with two coatings of cloth and try it.

[DJT]

Mike,

Just a quick note on the bubbling. They build boats out of Epoxy and Cloth all the time which are exposed to high temps and they don't have issues.

http://www.westsystem.com/ss/building-a-guillemot-kayak

This one was constructed when ambient temps were >100* and saw no issues with bubbles or blemishes.

[mikeschn]

Since 1969 they've been building corvettes out of a polyester resin...

Mike...

[squatch]

Pretty interesting test results and something to think about. Years ago when I started thinking about doing epoxy over foam for a homemade truck cap. I kinda figured the concept was that the foam was just a shaped form and insulation for fiberglass. Basically an internal mold. If we keep with that idea we will probably have better structures. Not much of anything bonds well to foam over the long haul in my experience.

2 layers of well treated canvas would probably hold up fine with the foam removed after everything has cured. as a shell anyway. Unless you beat on it. Like any composite structure every component adds something to the whole. I think the foam adds shape integrity and some impact resistance. Foam is strong under compression. Canvas is strong under tension as is fiberglass. Carbon fiber has little tension strength but is strong under compression. You need both compression and tension. A foam core adds rigidity. A tightly stretched canvas shell is like wrapping a stack of lumber with a load strap on a truck. It doesn't have to bond with the load to keep it tightly together. Obviously it would be better still if there was some bonding over the long haul.

Many items are called "carbon fiber" these days but in reality most of those are really composites. Different types of cloth materials bonded together with resin. Some are rigid, some flex, some like fiberglass are used as a surface layer to protect the underlying fabric from dings and such. A modern molded Carbon Fiber bicycle is a great example. 1/2 dozen or more materials used in different locations in the frame to add strength and "feel", or flex to keep the matrix from cracking in high stress areas. On the early versions they found that carbon fiber cloth used to make tubes conducted electricity when bonded to aluminum lugs. That caused galvanic corrosion and failure of the frame. It also fails catastrophically if the surface of the tube was damaged. Notch failure. So they started wrapping the carbon fiber layer with fiberglass as an insulator and to protect the underneath fibers. Problem solved. Some molded frames are placed in a mold with an internal bladder to squeeze the composite together as it cures. In some places this is not practical so they shape foam and wrap it with the cloth composite. The foam is mainly there as an internal mold.

I've owned several older fiberglass structures over the years. Boats, truck caps ect. Sooner or later the bonds tend to fail with whatever is used as a core material. wood, foam, aluminum.

These foamies are indeed modern composite structures. Even though we seem to be taking a fairly low tech approach to them. Hence my above rambles. Just some food for thought.

Has anyone tried using the poly (GG) or similar to bond the cloth to the foam? TBII with fiberglass cloth? There are a zillion glues on the market. Might be one that works easy like TB but bonds better with the foam.

Polyester resin is cheaper!

[mikeschn]

Squatch,

look here for the poly: http://tnttt.com/viewtopic.php?t=44801

Mike...

[RAYVILLIAN]

DJT I've heard that the key to not getting the sun bubbles is to cover the epoxy with paint or varnish if you want to see the wood like the guy with the kayak did. The last thing it mentions is covering the epoxy with 5 coats of varnish. I don't think that the bubble problem is caused by heat but by break down by the suns ultra-violet rays.

Gary