Laminated SIPs?

[mikeschn]

Giz,

That sounds like a really lightweight tear. Gary needs to look at this for his WW.

Mike...

[gizmotron]

Giz,

That sounds like a really lightweight tear. Gary needs to look at this for his WW.

Mike...

Mike,

I've been looking at a 5' 9" tall Widget for the inside dimension. That would make a 7' 2" tall (from the road) mini-trailer. This would mean that the rounded top trailer would only stick up 24" above the tow vehicle. That would not produce that much drag at a 55 tow speed.

So to save weight I think I have it now. By use of a combination of lightweight aluminum studded walls, the Dow, 1" thick, pink foam, and PL200 construction adhesive I can build a very strong and light TTT.

Like this:
Aluminum Skin Aluminum Skin
glue -------------------------glue
FOAMXXXXXX][XXXXXXXFOAM
glue -------------------------glue
Aluminum Skin Aluminum Skin

][ = a 1" tall by 1/2" wide .040 aluminum bent at 90 degrees. The two channels are then riveted together to form I beam shaped studs. These studs then have the foam insulation glued inside of them with PL200. Later after the frame and insulation is installed the aluminum skins are glued and riveted together to form a sandwich.

The trick with PL200 is that pressure is not that important because as stated before the glue does not give off a gas and expand while curing. In fact it is used all the time to bond Truss-Joist I-beam floor joist and plywood flooring. I'm convinced that the experiments with this adhesive have shown just how strong the stuff is without traditional vacuum bagging or pressure clamping.

I haven't gotten around to testing this yet... but I will someday.

Mark

[goldcoop]

Mike-

For what its worth, I did discover this on the Aliner I'm working on:

Inner skin is 3/16" paneling, 3/4" foam insulation (not sure what type; but it is white and forms loose balls when broken up) & aluminum skin on the outside.

Gorilla Glue worked great for bonding ALL three. I simply put 3 car tires/rims on top for weight.

Cheers,

Coop

[ARKPAT]

Mike that is what I'm using on my TTT is Gorilla Glue.



SteelSteelSteelSteelSteelSteelSteelSteelSteel outside
Glue------------------------------------------Glue
PolyfoamPollyfoamPolyfoamPolyfoamPolyfoam
Glue------------------------------------------Glue ----total insulated wall thickness is 4 7/8"-- I know it is very thick but strong and light
PolyfoamPollyfoamPolyfoamPolyfoamPolyfoam -- --total wall is R-56
Glue------------------------------------------Glue
PolyfoamPollyfoamPolyfoamPolyfoamPolyfoam
Glue------------------------------------------Glue
SteelSteelSteelSteelSteelSteelSteelSteelSteel inside and or 1/8"plywood


One steel skin outside three layers of polyfoam then steel or luam.

I'm using fir 1x or 2x as an edge only framework except for the bottom which is a like a big foam core wood door with steel clad as a base to build the shell on.


I know a little fuzzy but my money is going to keep up Gorilla Glue going because I'm not finnished yet.


Pat

[gizmotron]

Mike that is what I'm using on my TTT is Gorilla Glue.
...
I know a little fuzzy but my money is going to keep up Gorilla Glue going because I'm not finnished yet.


Pat

Pat,

Is that a foam core panel clad with a steel skin on the bottom?

If yes, then how thick of a steel sheet did you use please?

Mark

[ARKPAT]

I used 1/4" exterior plywood inset into the frame with two layers of polyfoam board sheet criss-crossed inside the frame work and two 34"x120" - 24 ga. steel sheet glued to the plywood bottom and frame. The sides at 48"x 120" - 24 ga steel sheets. LOTS of "Gorilla Glue". The foam board is attached the same way except without the plywood in the framework as the floor as in the wall and as the roof will be and yep the front and back. One big foam cooler with a door and windows.It would be cheaper to buy a case of Gorilla Glue I think.
The yellow stuff you see at the lower front edge of the frame and foam is Gorilla Glue between the foam and framework.

Lots of straps and tubs of water for weight ( Dollar Store tubs filled with water for weight to glue sheets together ).

And I forget more Gorilla glue.


Pat

[Trackstriper]

Mark,

I'm thinking something similar. I want to stay with aluminum sheeting even on the inside as my wife and I are quite sensitive to formaldehyde from plywood products. Less ply the better. Some thoughts on this:

(This is where Suzan says "TMI" - too much information)

1) Using aluminum skins with an aluminum stud will solve a lot of the coefficient of expansion problems that occur with mixed material systems. Ever see a wrinkle sided cargo trailer? Maybe one with a steel framework that is then skinned with aluminum? Aluminum expands or contracts three times as much as steel when heated or cooled. The only time things should fit correctly on these standard cargo trailers is at the temperature that they were built at. At other temperatures stresses are put on the fasteners and/or the skins wrinkle.

2) For your studs consider 1" square aluminum tubing. Yeah, sounds expensive, but.... try going to a local fence fabricator and ask if he has any surplus or damaged aluminum prefab fence panels. They will often use 1" pickets which are perfect for our use. I picked up about 40 pieces from a local scrap metal dealer for $1.50/lb which was about a dollar per six foot stick, powder coated in black. Might be easier than fabricating the "I" beam from two channels, and it would probably be stiffer in bending as it is truly one piece.

3) We would have a bit of a thermal transfer issue to deal with in that the whole structure is aluminum (even though there is insulation located between the skins and between the studs. The heat (or cold) will transfer locally at the stud and aluminum is very good at heat transfer. I have considered pre-gluing 1" x 1/2" wood strips to the studs (to make walls 1-1/2" thick ) on the interior face to act as a thermal break. I would probably place cuts through the wood at one foot intervals so that there is not a stress built up, straining the glue joint, due to different expansion characteristics. The aluminum will lengthen with heat while the wood will lengthen with additional moisture content. This effect may be insignificant in a practical way, but it's easy enough to make a few cross cuts nearly though the wood but not into the aluminum.

4) I have tried very small samples so far. The aluminum sheet sample was about 12" x 18" and I glued down four different pieces of tubing that were about 8'" long. The .065" aluminum sheet was factory painted so I sanded it lightly, but not through the paint, and the powder coating was sanded lightly also. I tried standard-set J.B. Weld, PL400, Gorilla Glue, and a single component moisture-cured polyurethane binder that I had from work. The aluminum sheet was placed on a flat surface and the tubes were glued down. No additional weight was placed on them for these samples and they were not clamped. All of the glue systems worked well, the moisture cured binder was marginal and took too long to set - several days. The bonds with the glues were very strong. The binder was marginal here also. I would imagine that Raka would have some epoxy that would work great.

5) I also fastened one sample with an acrylic adhesive 1/32" foam bonding tape from a sign supply company. Once cured, I could not tear off the 8" sample with my hands, quite impressive, and it would help create a thermal break. I test loaded this piece (8 sq. inches) in shear with a 60# weight, but it failed after three days constant loading...the foam separated rather than adhesive failure. I would be hesitant to use this on a trailer if the skin is carrying a load, although it might work OK when you consider many studs and lots of square inches of bonding surface to distribute load. This was not 3M bonding tape but a house brand. I think a glue would be more bulletproof. Haven't destructively tested the glued pieces.

Hope this gives you some food for thought.

J.B.

[gizmotron]

... One big foam cooler with a door and windows.

...Pat

Ha! That's exactly what these things would be. Beer coolers on wheels.

Mark

[gizmotron]

Mark,

I'm thinking something similar. I want to stay with aluminum sheeting even on the inside as my wife and I are quite sensitive to formaldehyde from plywood products. Less ply the better. Some thoughts on this:

(This is where Suzan says "TMI" - too much information)

1) Using aluminum skins with an aluminum stud will solve a lot of the coefficient of expansion problems that occur with mixed material systems. Ever see a wrinkle sided cargo trailer? Maybe one with a steel framework that is then skinned with aluminum? Aluminum expands or contracts three times as much as steel when heated or cooled. The only time things should fit correctly on these standard cargo trailers is at the temperature that they were built at. At other temperatures stresses are put on the fasteners and/or the skins wrinkle.

J.B. ,
Yep, I've seen that wrinkling before. I've never seen it on our AlumiLite Holiday Rambler. It is constructed of an all aluminum frame and skin. They used a plywood or hardboard on the inside and that stops heat transfer cold spots.

2) For your studs consider 1" square aluminum tubing. Yeah, sounds expensive, but.... try going to a local fence fabricator and ask if he has any surplus or damaged aluminum prefab fence panels. They will often use 1" pickets which are perfect for our use. I picked up about 40 pieces from a local scrap metal dealer for $1.50/lb which was about a dollar per six foot stick, powder coated in black. Might be easier than fabricating the "I" beam from two channels, and it would probably be stiffer in bending as it is truly one piece.

Perhaps a much stronger wall too. But by using I-beams I have the foam glued inside the I-Beam so that the bond will add to the strength of the sandwich system. The only way to know is to test it. Still, that's a great way to get 1" aluminum.

3) We would have a bit of a thermal transfer issue to deal with in that the whole structure is aluminum (even though there is insulation located between the skins and between the studs. The heat (or cold) will transfer locally at the stud and aluminum is very good at heat transfer. I have considered pre-gluing 1" x 1/2" wood strips to the studs (to make walls 1-1/2" thick ) on the interior face to act as a thermal break. I would probably place cuts through the wood at one foot intervals so that there is not a stress built up, straining the glue joint, due to different expansion characteristics. The aluminum will lengthen with heat while the wood will lengthen with additional moisture content. This effect may be insignificant in a practical way, but it's easy enough to make a few cross cuts nearly though the wood but not into the aluminum.

I don't know---- maybe that's the way to go with it. With a heater or an air conditioner that would force the comfortable temperature to out side edge.

4) I have tried very small samples so far. The aluminum sheet sample was about 12" x 18" and I glued down four different pieces of tubing that were about 8'" long. The .065" aluminum sheet was factory painted so I sanded it lightly, but not through the paint, and the powder coating was sanded lightly also. I tried standard-set J.B. Weld, PL400, Gorilla Glue, and a single component moisture-cured polyurethane binder that I had from work. The aluminum sheet was placed on a flat surface and the tubes were glued down. No additional weight was placed on them for these samples and they were not clamped. All of the glue systems worked well, the moisture cured binder was marginal and took too long to set - several days. The bonds with the glues were very strong. The binder was marginal here also. I would imagine that Raka would have some epoxy that would work great.

That's great. Did you stand on it like a scene from a magic glue commercial. Remember the guy that hangs from a hard hat that is glued to a cross beam and says "Would you try this with your glue?"

I saw those pictures of other testers here that stood on their tests. Now that's proof.

5) I also fastened one sample with an acrylic adhesive 1/32" foam bonding tape from a sign supply company. Once cured, I could not tear off the 8" sample with my hands, quite impressive, and it would help create a thermal break. I test loaded this piece (8 sq. inches) in shear with a 60# weight, but it failed after three days constant loading...the foam separated rather than adhesive failure. I would be hesitant to use this on a trailer if the skin is carrying a load, although it might work OK when you consider many studs and lots of square inches of bonding surface to distribute load. This was not 3M bonding tape but a house brand. I think a glue would be more bulletproof. Haven't destructively tested the glued pieces.

Hope this gives you some food for thought.

J.B.

It sure does. Great work.

I'm a fan of PL200. I'm thinking that a channel shaped stud is all that is needed to add enough strength to prevent sheering / delaminating.

Thanks for all the suggestions.

Mark

[ARKPAT]

To be exact I was going to use steel studs and pop rivit the seams and forget the wood all together but the experiment got larger and now the shape of a trailer. I can remove the wood altogether and make a tubular exterior frame like the Ausies use to attach too. I want to see how this works out and the lifecycle of racking and vibration play on it.
As far as buckling I think the steel sheeting glued directly to the polyfoam would be too much surface area attached to buckel or be wavy no seams on the sides only bottom and top down the center.


Pat

PS: The only place plywood ( exterior grade ply. very little formaldehyde gassing ) is use is inside the bottom framing ( to make a rigid floor to build from ). The wall and all the rest is steel sheeting and three layers of polyfoam glued together with steel sheeting inside and out ( SIP ).
I do not fear the strength would be a problem, because I could stand on one layer panel with the steel clad ( insulated door blank ) on both ends of the panel across a pickup bed with very little bowing. I showed Madjack the samples I glued together ( polyfoam to polyfoam to steel sheeting to steel sheeting )at Bever Bend over a year ago. I could not shear the glued panels apart or the steel sheeting also glued to the polyfoam boards. I could break the foam boards ( bending ) at the holding points ( one layer thick ) only but not where there where two or three layers thick. But I'm not a testing facility so the strength and usability is up to the user to try.

And yes I have stood on the panels to test them across a 72" open space accross a frame. It held me up at nearly 300# barefoot ( not to spread the weight with boots or shoes but to consentrate the load at the heels and toes ) in the middle with no other support.

[gizmotron]

To be exact I was going to use steel studs and pop rivit the seems and forget the wood all together but the exteriment got larger and now the shape of a trailer. I can remove the wood altogether and make a tubular exterior frame like the Ausies use to attach too. I want to see how this works out and the lifecycle of racking and vibration play on it.

The Holiday Rambler has crossed the USA five times. The only stress point was just above the door. The floor flexes at least 2" up on both ends while setting down the stabilizers. The aluminum skins run horizontally with a seam at the middle. If the seams where vertical then I think some of the joints would have popped loose. So the aluminum flexes without breaking.

I just love those stainless steal polished sided $1,000,000 motor homes. They look bomb proof. I checked it out at 24 gage stainless sheet. You could use your method with sheet metal channel shaped studs, (my idea) and the weight of a side wall would be the same as 3/4 plywood.

Just think, a Prevost Teardrop.

Pat

PS the only place plywood ( exterior grade ply. very little formaldehyde gassing ) is use is inside the bottom framing ( to make a rigid floor to build from ). The wall and all the rest is steel sheeting and three layers of polyfoam glued together with steel sheeting inside and out ( SIP ).
I had not a fear because I could stand on one layer panel with the steel clad on both sides with the panel across a pickup bed with very little bowing. I showed Madjack the samples I glued together at Bever Bend over a year ago. I could not shear the glued panels apart or the steel sheeting also glued to the polyfoam boards. I could break the foam boards ( bending ) at the holding points ( one layer thick ) only but not where there where two or three layers thick. But I'm not a testing facility so the strength and usability is up to the user to try.

And yes I have stood on the panels to test them across a 72" open space frame. It held me up at nearly 300# barefoot in the middle with no other support.

That's enough strength for me.

Mark

P.S.

From here:
http://www.precisionsheetmetal.com/home/materials.htm

Aluminum sheet vs steel sheet

The following table gives a quick point of reference when you need the approximate thickness of aluminum sheet to use in replacing steel sheet. The designated aluminum thickness will give you about the same stiffness. Or, putting it another way, the deflection will be about equal. As a rule of thumb, plan on using an aluminum sheet about 40% thicker than steel. Since aluminum weighs only 1/3 as much as steel, this means that the equivalent aluminum sheet will weigh only half as much as the steel sheet it replaces.

Approximate stiffness equivalence:

Steel LB/SF | Steel Thick | Alu Thick | Alu LB/SF
.975 .024 .032 .452
1.22 .029 .040 .564
1.47 .035 .050 .705
1.80 .044 .063 .890

[Trackstriper]

Correction to item #4 in my post of September 6.

I used PL Premium Polyurethane Adhesive rather then PL400. I was checking their website to see what the difference was between PL200 and PL400 and I realized I made a mistake.

J.B.

[Thawley]

This is a GREAT thread.

[GuitarPhotog]

You might want to look at 3M's Fastbond30. It's water based so it won't eat the foam, nor explode. It's very strong when applied properly and has great high temperature characteristics. Down side is it's expensive at $30+ per quart.

Info here http://tinyurl.com/apy9gp7

<Chas>

[Thawley]

Have you used it before? How is it different from the water based contact adhesives sold Home Depot?