A more durable Foamie?

[rruff]

Now you just need to take a piece of unsupported aluminum siding used in the RV industry and jab a screwdriver into it....... Just for a comparison.

I don't know where I'd get some, but my neighbor's trailer is sitting in his yard. Think he'd mind? In the name of "science" and all...

[dancam]

I have made a little progress. It takes a good while (week or more?) for the TB2 to fully cure, and it needs to be fully cured for "poking a hole" tests. I've discovered that epoxy also takes several days to fully cure.

I'm testing how hard it is to force (strike) a medium size flat head screwdriver through the skin. It's totally qualitative, but I do try all the samples several times to get a good feel for it. All skins are over 1" 15 psi XPS. Note that the weights below for glued on skins (luan) include the glue weight, which in this case is PLP at ~.12 lb/sq ft.

Sample, Skin weight (lb/sq ft), Penetration resistance WAG (scale 1-10)

PMF 10oz 1 layer, .15, 1
Laun 2.7mm, .50, 2
PMF 10oz 3 layer, .45, 3
Luan 2.7+ 6oz FG, .62, 4
6oz FG 3 layer, .36, 6

PMF seems to be better than plywood on an equivalent weight basis, with the added advantage of not rotting. And if 1 layer of 10oz PMF is "good enough" there isn't any plywood you can buy that is near the weight. Multiple layers of PMF are quite time consuming though, at least the way I did it. I'd use a trowel to spread a layer of TB2 on, place the canvas and roll it down with a FG roller, let it dry for 8-12 hours, apply a layer of TB2 spread with a flat blade, let that dry 8-12 hrs, repeat. If you want a stronger PMF layer it's easier to use heavier canvas.

Would you mind trying one more puncture test for us? Could you take a bathroom scale, zero it to the weight of the screwdriver and sample piece, then stick the screwdriver pointing up in the middle of the scale and push down onto the screwdriver tip with the sample piece. Watch how far the scale moves and you should be able to feel when the screwdriver punctures the sample piece and that will give a better rating. Another person watching to tell you exactly when it punctures may help.



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[GPW]

In the real world , I wonder how many times a trailer gets punctured by someone with a screwdriver , and lives to tell about it ... ... we don’t read about it much ... Another thing to consider is how easy it is to FIX ... Seems the harder it is to puncture , the more difficult it is to fix ... ( ? )

Ruff.... Gripper works to secure canvas , but it has to be done carefully and perfectly ( 100% coverage on both foam and canvas ) ... TB2 worked better for us , then gripper on the outside ... JMHO

Another thing , Gripper doesn’t seem to re-heat and get sticky again like the TB2 does ... so ironing doesn’t help ... we tried that onthe FS where an area was glued down with Gripper and lifted ... eventually we had to peel that back and re-glue using TB2 ...

[QueticoBill]

From an associate re: styrospray:

"A company I worked for used Styrospray extensively. We had a lot of luck but also some issues. If there was anything between the substrate and the coating it had a tenancy to peel. We suffered some impact cracks that had to be filled and sanded. We used this on an installation that was up for a year outside in the elements and did not have any issues. A word of warning for any of these products, make sure you use appropriate PPE. Styrospray contains isocyanates these can cause reactions ranging from irritation to nervous system problems. We had an OSHA violation because of our use of Styrospray. I strongly recommend that if you use any of the 2 part coating products discussed here you read the MSDS and comply with all requirements."

[rruff]

Would you mind trying one more puncture test for us? Could you take a bathroom scale, zero it to the weight of the screwdriver and sample piece, then stick the screwdriver pointing up in the middle of the scale and push down onto the screwdriver tip with the sample piece. Watch how far the scale moves and you should be able to feel when the screwdriver punctures the sample piece and that will give a better rating. Another person watching to tell you exactly when it punctures may help.

That makes a lot of sense! Would be nice to have a real number. Unfortunately I only have a digital scale that won't read unless the weight is stable.

I did some playing around with denting. Just turned the screwdriver around and used the rounded handle and put my weight on it. I could dent the single layer of PMF fairly easily, but could not detect any obvious dent on the 3 layer sample. The luan would make crackling noises but no visible denting. A layer of fiberglass over the luan nearly eliminated crackling, but not quite. The 3 layers of fiberglass crackled a lot, and I could see cracking in it. But oddly this did not compromise the structure when I tried the penetration test. At least not enough that I was able to get through it.

I now have a bunch of other fiberglass samples. 18oz roving + 10oz cloth, 10oz cloth x2, 10oz cloth x2 with 2mm bulking matt, 17oz biax, 17oz biax + 10oz cloth, 17oz biax x2. I was surprised that I could poke a hole in the first two. Maybe the epoxy is less strong than what I used before, or I need to let it cure longer. All of them crackled when subjected to the blunt end of the screw driver, though the one with 2mm bulking matt did the least. I didn't know what to expect from the bulking matt. It makes the fiberglass layer much thicker but it takes a lot of resin (~.2 lb/sq ft), so I don't know if it would make sense for this "lightweight" application.

[rruff]

Ruff.... Gripper works to secure canvas , but it has to be done carefully and perfectly ( 100% coverage on both foam and canvas ) ... TB2 worked better for us , then gripper on the outside ... JMHOAnother thing , Gripper doesn’t seem to re-heat and get sticky again like the TB2 does ... so ironing doesn’t help ... we tried that onthe FS where an area was glued down with Gripper and lifted ... eventually we had to peel that back and re-glue using TB2 ...

I tried using PLP instead of TB2 to glue down the canvas. Very different! PLP is sticky but also slimy (?), it seems to slide relative to itself when wet. With TB2 the wrinkles smooth out easily. TB2 gripped pretty well right away, but PLP had little grip until it cured.

At what temperature does TB2 get sticky?

[KCStudly]

TB2 open time varies by temperature, humidity, and, I suppose, application thickness. It gets sticky when the water in the solution evaporates away. Hotter temp, less humid atmosphere, thinner application, windy conditions should all result in quicker dry times.

[GPW]

TB2  seems to re-liquify at higher temps ( why we “Iron" troublesome spots . ) Not sure exactly but somewhere between the Sun ’s heat 140F +(measured ) and before the foam starts to melt ... We need to test that somehow ...

[linuxmanxxx]

From an associate re: styrospray:

"A company I worked for used Styrospray extensively. We had a lot of luck but also some issues. If there was anything between the substrate and the coating it had a tenancy to peel. We suffered some impact cracks that had to be filled and sanded. We used this on an installation that was up for a year outside in the elements and did not have any issues. A word of warning for any of these products, make sure you use appropriate PPE. Styrospray contains isocyanates these can cause reactions ranging from irritation to nervous system problems. We had an OSHA violation because of our use of Styrospray. I strongly recommend that if you use any of the 2 part coating products discussed here you read the MSDS and comply with all requirements."

I'm still totally intrigued with using this on a hybrid foam build. A plastic foam camper how cool is that?

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[rruff]

TB2  seems to re-liquify at higher temps ( why we “Iron" troublesome spots . ) Not sure exactly but somewhere between the Sun ’s heat 140F +(measured ) and before the foam starts to melt ... We need to test that somehow ...

Heck I found a regular lightbulb and have a IR thermometer. Bet I can get a fair reading on that if I'm careful.

[rruff]

I'm still totally intrigued with using this on a hybrid foam build. A plastic foam camper how cool is that?

Buy some and play with it! Worst that can happen is you'll be a few $ poorer, but you'll learn something!

Which reminds me, I need to buy some more epoxy...

[QueticoBill]

From an associate re: styrospray:

"A company I worked for used Styrospray extensively. We had a lot of luck but also some issues. If there was anything between the substrate and the coating it had a tenancy to peel. We suffered some impact cracks that had to be filled and sanded. We used this on an installation that was up for a year outside in the elements and did not have any issues. A word of warning for any of these products, make sure you use appropriate PPE. Styrospray contains isocyanates these can cause reactions ranging from irritation to nervous system problems. We had an OSHA violation because of our use of Styrospray. I strongly recommend that if you use any of the 2 part coating products discussed here you read the MSDS and comply with all requirements."

I'm still totally intrigued with using this on a hybrid foam build. A plastic foam camper how cool is that?

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It would be interesting to be able to test it in different combinations. It seems to have very little or no tensile strength, so can't replace ply or canvas on either side of a vertical panel or underside of a horizontal panel. The peeling noted made me wonder if it would work better with roughening of the foam substrate. I believe I read it works fine on fabric and wood and such, so that had some interesting possibilities. But the real fun begins with maybe a late 1950s tow vehicle, and adding fins to the TD. Or just being a lot more free form in other ways.

[rruff]

Heck I found a regular lightbulb and have a IR thermometer. Bet I can get a fair reading on that if I'm careful.

....and. At 150F the PMF (just 1 layer of 10oz canvas and TB2 over foam) was quite soft. At 170F it was still soft and had turned reddish brown!

[GPW]

Ruff, had that been allowed to cure completely ( weeks ) ....

[gizmotron]

So I know for sure that my Standy will have a foamie body. Many variations on a foam Standy have been published here. I'm thinking of making mine a hybrid where I don't count on just foam for lateral bracing. If I was using fiberglass and epoxy over foam then I might not.

Has anyone discussed how windsurf boards are built? They take a Clark Plug, plane and sand it into shape, before they add hard points to it. These Clark plugs have a one or two rigid spar system running down the center of the long way of the plug. These spars are like the main structural strength in a wing design. I would like to use these techniques in the design of my true ultralight foam trailer. I'm just guessing here but it looks like everyone is using Gorilla Glue for adding studs and trimmers to their door and window cutouts. They also use it to make changes on the fly to their foam panel sections, like the side panels. I wonder just how strong are those glue points. If the foam was pushed on hard enough would the walls separate from the floor where the glue failed first or the foam failed next to the glue first?

I'm just wondering if adding stringers, like wing spars, to the 2" Owens Corning Foam, glued with GG would add strength and stability to it or actually decrease the strength?

As far as hard points go, I need a way to bolt down two rails of angle aluminum down each side of the top, running the long way, in order to hold three or four solar panels. If you take a six inch diameter disk of 3/8 or 1/2 inch plywood and router a matching six inch diameter indentation in the foam, where the hard point is needed, you can glue the plywood plug where the hard point is needed, to the inside of the roof. Foot strap hard points and fin box insertions are done all the way through the foam plugs from top to bottom of the surf board. They are epoxied in and then bonded on top and bottom by the fiberglass and epoxy skin. These items are non compressible. But a 6 inch plywood washer, hard point, would be subject to compression. I see that all the builders that are using PMF are folding the materials over the inside of doors and window framing as they apply the structural skins. I believe that these foamie structures are strong enough to withstand lateral pressure enough to hold together. Like all homes built now on the West Coast of the USA there must be a way to hold the frames down to the foundations and slabs for earth quake protection from catastrophic failure. This is why I'm making considerations for spars, 1/4 inch plywood stringers, that can be fastened down to the floor. If the Gorilla Glue won't bond with the foam then it could defeat the purpose of making the foamie an engineered mono body design in the first place. The foam has break points at 16" and or at 24" running the long way down the foam. 2" wide 1/4 inch plywood stringers could be glued between those snap points to facilitate a stronger hold down technique. They would become embedded stringers, just like the foam plugs made by Clark.

The key to all this is in knowing how well the Gorilla Glue does bonding to the door and window frames. Any advice would be welcome.