A more durable Foamie?

[KCStudly]

atahoekid built the Road Foamie as a foamie hybrid with epoxy/glass outer skin similar to TPCE.

[gizmotron]

I figured out a better way to hold it down. I'm building a cantilevered facade, at the floor line, that serves as the strength for the bottom of the sides. I don't want to draw a picture. I don't want to use a computer to draw a picture. I can build an entire custom home from a drawing on a napkin. So I'll paint a picture with words as if I were telling my lead carpenter how to do it. I hope that satisfies.

I need the standee to be low. I've figured out how to get a full sized trailer that only sticks up 36" above my Toyota Corolla.

Everybody has framed out the floor on their Harbor Freight 4 x 8 trailers with 2 x 2, 2 x 4, or 2 x 6. I'm going to just run two sheets of 3/4 inch Douglas Fir tongue and grove sub floor and let it cantilever out without a frame under it. I need it to stick out 7" on each side of the steel frame. I discovered that I will use shims on top of the uneven points of the top of the HF trailer so that the sub floor is dead on flat. This method needs to be shimmed and bolted to the cross members of the HF frame as well in order to prevent up and down flexing. Once that is properly achieved it is going to get a very strong rail type "Box Beam" configuration that is built out of 5/8" Fir plywood for the outside runner that makes up the bottom of the side panel. It will run the full length of the floor, including the cutout for the wheel, including the drop step for the standard industry RV door, and will be glued and screwed to the edge of the cantilevered 3/4" floor making the beginning of the box beam structure.

So you have a 3/4 inch floor running into a 5/8 inch perpendicular rail that sticks up 6" above the floor and 6" below the floor. On top of the floor a channel is added to the inside of that rail, made out of 5/8" plywood, both bottom and side, to receive the 2" foam panel that makes up the sides. The top of the rail / channel is beveled at 45 degrees inside and outside. The foam will be glued and doweled before the 18 oz duck canvas is applied. I found a great resource for that too, http://www.mytarp.com/numbered-duck-natural-canvas.aspx You can get 18 ounce that is six feet wide without a seam and in almost any length. http://www.mytarp.com/no-8-cotton-duck- ... -yard.aspx

Below the floor, in the cantilever on the outside, the box beam will be framed out of more 5/8" plywood and filled with scraps of 2" foam, all glued together to prevent the frame from deforming, It will have TB II and screws all over the place.

Because this lock down technique is being used, I decided to go with the PMF with one layer of 18oz duck canvas. I will only run 1/4" stringers in the roof, not in the sides or the back. The front will have three layers of 1/4" stringers laminated together to form my rounded front stringers with 2" foam in-between. A beveled matching base board will match up with the side bottom panel to complete the effect both front and back.

Now that I've decided how to do the cantilever I can get started as soon as the snow melts. I will take plenty of pictures for this build. Then you will have your images of what I mean.

[rruff]

This is interesting. My PMF is exhibiting a huge level of CREEP!

As I reported earlier this panel initially sagged a little of over an inch under the weight of the concrete block. Just for fun I left the block on it (about 1.5days) to see what would happen, and it sagged all the way to the ground! I don't know what the temperature was in the garage, but it's been 30s to high 60s outside.

PMF_block_sag.jpg (56.8 KiB) Viewed 913 times

The panel doesn't appear to broken in any way though and seems to retain stiffness that is very close to what it had before. I flipped it over and it has no trouble holding up the block with minimal sag. I do expect that gradually creep and flatten out over time.

PMF_block_bridge.jpg (56.82 KiB) Viewed 913 times

PMF certainly has interesting properties! You wouldn't want to put it in a situation where panels are constantly loaded, but so long as that is avoided this creeping behavior is just a curiosity.

[rruff]

Just went out and checked on it, and it was already past level. Maybe an hour? It happens pretty fast.

I put the FG panel in the same place but with 2 blocks to see what happens to it. I'm concerned that the foam might be creeping rather than the TB2.

[ghcoe]

That is interesting, but you might have just stumbled onto a way to curve foam without heat! GPW has talked about this for some time trying to figure out a way to heat foam panels to make nice non-kerfed curved panels for foamies. This might need more testing with a full sized panel now.

[ghcoe]

I am wondering if maybe the TBII is still not totally dry yet.

[rruff]

I am wondering if maybe the TBII is still not totally dry yet.

It's had a long time. I haven't kept track but it's over a week.

If you google "titebond creep" you will get a lot of hits, so I think it's normal for this glue. I don't think it's a problem for a camper, so long as you don't put a big load on the roof.

Just checked the FG piece and it isn't showing any signs of creep.

[GPW]

... Just FYI , a wooden board will do the same thing with a proportional amount of weight on it ... plywood too ...

[gizmotron]

"There’s no place like Foam !"

All this discussion and experimentation, that has led to important data, is fantastic. I'm looking at 1/4" Sande plywood on the outside and 1/8" loan plywood on the inside. I love that classic trailer look you see in all those retro trailer rehab projects on TV. I'm working on 1/4" Sande plywood box beam studs and rafters and recycled corrugated cardboard as insulation. It's free and all I have to do is a little glue and cutting. I did a weight estimate and have managed to drop the weight to 800 lbs. That's 100 lbs less than the foamie with 18 oz Duck Canvas and glue. It comes down to the spars and ribs styled construction. It works in light aircraft and it will work in this. All the box beam framing is cut on a table saw and assembled with TB III and with brad nails. I'm going to build it as a unibody method of construction before I skin it.

[KCStudly]

Corrugated cardboard glued up will weigh a lot more than EPS/XPS foam. Just saying, sometimes "free" isn't.

[gizmotron]

Corrugated cardboard glued up will weigh a lot more than EPS/XPS foam. Just saying, sometimes "free" isn't.

Looks like testing time is ahead. I could also use R-13 Kraft Faced Insulation at less than half the price of XPS. I would just make the wall studs 3" wide also. One great thing about the 2" foam though. It is simply way more quiet inside.

[rruff]

... Just FYI , a wooden board will do the same thing with a proportional amount of weight on it ... plywood too ...

I tried it with the FG sample with double the weight and it sagged ~1/8" after a couple days. Currently I have 3 blocks on a 48"x15"x1" piece and it hasn't sagged at all after 8 hrs. So if these do creep, it's a lot less with an equivalent load.

PMF skins certainly have interesting properties. I don't think creep is an issue unless you wanted to carry a load on the roof or something.

[gizmotron]

PMF skins certainly have interesting properties. I don't think creep is an issue unless you wanted to carry a load on the roof or something.

I want to carry a load on the roof. I know I've been jumping around on how to do this. It looks like one coat of 4oz or 6oz fiberglass cloth with epoxy over 2" XPS foam is the lightest and strongest method. I want to add to that 1/4" Sande stringer studs and rafters with a continuous 1/4" six inch wide stringer embedded in the upper surface of the foam on each edge running the long way down the roof. Each 1/4" stud will be tied to each 1/4" rafter and run on 16" on center. like the ribs in a wing. Only the front will have 1/4" plywood with fiberglass over it. Let's see if I stick with this. Weight is the motivating factor, based on those demonstrations in the weight thread.

[rruff]

Best to get some foam and fiberglass materials and see if you think such a light skin of fiberglass is enough. It isn't for me. 1708+ 6 or 10oz cloth looks about right.

If you are going very light, PMF has some advantages. It bends and dents (and the dents can come out with heat), while other materials will break and crack.

GPW mentioned that Durasip is a potential skin material: viewtopic.php?f=55&t=67805 http://www.durasip.com/pdf/LaminateDataSheet.pdf The thicker one is $1.25/sq ft, didn't get a price on the thin one. They sell it in 8' rolls so you can do the sides and top of even a large camper without seams.

[gizmotron]

OK now, I changed the framing to 1/4" stringers for studs that support the 1/4" rafter/stringers. All that framing sandwiched between 2" foam. With 2 layers of 6oz fiberglass and Epoxy, the estimated weight comes down to 770lbs. That makes it the strongest and it also allows for the entire inside done in 1/8" Luan plywood.