Laminated SIPs?

[Mitheral]

The last desktop I had laminated cost me $52! If I were going to build SIP walls on my teardrop, I'd cut out the parts and take it to a shop that could do perform that process.

Alternatively if you do two sides plus the floor you'll have invested $156 (assuming they charge the same amount for doing one or two sides otherwise $312) plus travel time (twice) getting the stuff bagged. You'd have to do it on their schedule and you'd have to trust them to get it right with a process they aren't familiar with (SIPs rather than veneer).

Besides when you do tear MKII you'd have the tools on hand and you'd be able to vacuum bag your doors.

The materials aren't all that much for non production bagging:
1) Some plastic sheeting, A 1000' foot roll of vapour barrier poly 8'6" wide is C$35
2) A vacuum pump. Even the shop vac that most builders own can do the job for our purposes. Make sure to allow a little bleed so you cool the motor. Not always required but good insurance. Or for C$30 you can get an auto A/C pump from the junk yard (look for a York V, they have sumps for oil) and connect it to a $30 surplus 1/2-1 hp electric motor. Use your shopvac to exhaust the bag then hook the intake of the compressor to the bag and you can draw 15-20 in-hg.
3) some pvc piping and fittings to allow hook up of your shop vac and/or A/C pump.
4) a flat area as large as your largest piece to do the bagging. A couple saw horses supporting a few 2X4s on edge with a sheet of plywood on top would be sufficient.

You don't even really need to seal the edges of the plastic. Fold it over on itself a couple of times and then clamp between two 2X4s. It'll leak a bit but that just means a little less vacuum and more motor run time. If you don't have clamps just screw the 2X4s together every six inches. Use some tuck tape if you want to get fancy.

[captainsam]

I tried using the two-part polyurethane to pour between sheets of luan to build a panel again. I still think this is quite difficult. As the foam sets it is outgassing and swelling(expanding). It seems that a great degree of clamping is required to hold the luan in a stable position. I read that it can generate up to 6 psi. I at first thought an escape route for the excess foam was the answer, but it seem that the expansion continues to apply pressure after the position of the foam has set. In my opinion, this is a more difficult task that laminating the luan to a sheet of existing foam. Unless someone has a good idea how to do this, I am going to focus on the laminated panels using a vacuum system.

[Artificer]

Did a bit of vacuum bagging this weekend. I finally got around to making up some SIP test pieces. Expanded, Extruded, Isocyanurate foams, 1", 2", PL glue, Polyurethane, tile adhesive.

Here's a pic. I wasn't watching the setup, and developed a leak, so I may have to redo the glueing. Also, don't put a 1" thick piece next to a 2" piece.

Plastic is a spare Ag Bag that I had.

The green stuff is the cheapest outdoor carpeting I could find. It acts as the breathable material. Allows the air to be removed over the entire surface. Note to self: make sure there is a glue barrier (wax paper/plastic) between the carpet and the wood.



CaptainSam: I'll check the vacuum pump's flow rate. Seemed to have a bit of problem this weekend, but that could have been the setup. I'll use the old inflated garbage bag trick to check out the flow rate of the pump, and let you know.

[Artificer]

I tried using the two-part polyurethane to pour between sheets of luan to build a panel again.
...
In my opinion, this is a more difficult task that laminating the luan to a sheet of existing foam. Unless someone has a good idea how to do this, I am going to focus on the laminated panels using a vacuum system.

If you're going to make flat pannels, I think laminating them is the way to go. A 4'x8', 1" thick expanding foam core is going to cost over $20 in foam. If you use the PL polyurethane glue, like you mentioned, the price will be a lot less. Total cost will probably be similar in price, but a lot less hassles.

I would reserve the expanding foam for curved segments of the trailer, like the roof. Even then, I might rethink it. The foam doesn't like to expand more than a foot or so from the pour point. (at least in a 1 1/2" cavity) I ended up drilling holes in the roof, and re-pouring foam to fill voids. But the stuff still has a high "coolness factor."

One thing I've been thinking about is the people that add foam insulation to hold houses. Could you build the panels, drill access holes, and have the spray the stuff in? Take the trailer to one of their jobsites, and see what the price would be.

[angib]

Note to self: make sure there is a glue barrier (wax paper/plastic) between the carpet and the wood.

Top tip:

The cheap resin/glue barrier used by professionals is 'bread wrap' - micro-perforated plastic (maybe polyethylene) used in bakeries to wrap bread. Ask nicely and you might get the end of a roll for free.

Of course, it's possible 'bread wrap' may be used only in the UK and not in Merka/Canuckia!

Andrew

[Melvin]

Plastic is a spare Ag Bag that I had.

Good idea, what would one of those bags cost?

The green stuff is the cheapest outdoor carpeting I could find. It acts as the breathable material.

Also a good idea. Wouldn't work for fiberglass work or vacuum forming but perfect for clamping SIPs.

[Melvin]

One thing I've been thinking about is the people that add foam insulation to hold houses. Could you build the panels, drill access holes, and have the spray the stuff in? Take the trailer to one of their jobsites, and see what the price would be.

I was quoted $3-6 a square foot to do my house for a 3.5" cavity. They must be using a fairly low pressure foam otherwise it would blow the gyproc off. You'd have to make sure to design large cavities without a lot of cross bracing to minimise your number of penetrations.

[GPW]

When we used to pour two part Urethane foam into fuselages , we'd pour them vertically .... pour the foam in from the top a little at a time(small batches ) and it will always rise if unobstructed and not put much pressure on the outside walls ...The foam will act the same way in a paper coffee cup ... foam rises , overflows cup , cup not distorted...

Why is it you guys have a tendency to complicate these things ... It's becoming painfully obvious , that if you're building just one TD , all this procedure MAY not be worth all the set up / eqpt. that you have to do/buy ...Old school TD's were built by "home builder" type guys ...practical methods ... SIPS were invented by guys that wanted to build houses cheaper /quicker... of little concern to we "quality guys " eh ????
Now if you're going to build a few of these bad boys, then this may be practical ....any FEMA contractors out there ????Given the state of things we could sell the Government a TD for what ? $50 K .... easy , if we were big campain donors .... or oil companies

We always fixed the leaks in our vacuum bags , works so much better and does not draw moisture into the mix...Humid here ...

[asianflava]

Why is it you guys have a tendency to complicate these things ...

That is the understatement of the year.

[Melvin]

Why is it you guys have a tendency to complicate these things ... It's becoming painfully obvious , that if you're building just one TD , all this procedure MAY not be worth all the set up / eqpt. that you have to do/buy ...Old school TD's were built by "home builder" type guys ...practical methods ... SIPS were invented by guys that wanted to build houses cheaper /quicker... of little concern to we "quality guys " eh ????

I'll be doing SIPs for the sidewalls and floor (and maybe roof/hatch) to reduce weight and maximise R value (no or minimal bridging). I'll use foam sheets rather than pouring liquid foam though.

The only thing I'll need to buy is a few PVC fittings. And maybe some indoor outdoor carpet.

[Artificer]

Why is it you guys have a tendency to complicate these things ...

That is the understatement of the year.

Welcome to my world

I see a distressing number of similarities in myself with the Engineer Identification Test, especially the section that says:

"Engineers like to solve problems. If there are no problems
handily available, they will create their own problems.
Normal people don't understand this concept; they believe
that if it ain't broke, don't fix it. Engineers believe that
if it ain't broke, it doesn't have enough features yet."

Pouring 2-part foam: As long as the height of the pour is less than 2-3 widths of the cavity, you should have little side pressure. As for the cup, I can dump a bunch in, and seal it, and still have no/little distortion. The round sides are stronger than you think. The problem we've been experiencing is that we're trying to get the foam to fill a cavity that is many times higher than it is wide. Too much friction/viscosity holding the foam back, so pressure builds up. Also, the panels are flat, so no curved surfaces to give them strength.

Complications: The first time is always complicated, unless you have someone there holding your hand, telling you what to do. If Captainsam comes up with a simple vacuum bagging method using inexpensive parts, more people might try it. The people building ultra-lightweight trailers could certainly benefit from his efforts. Equipment could be as cheap as $10 tape/plastic sheeting, $5 carpet, $17 for vacuum pump (if they have a compressor), and bit of tubing. Don't have a compressor? Use an water aspirator.

This all comes down to the similar argument about the water-jet cut side panels. Some say "just use a jigsaw, and cut it", while others are intrigued by the process and finished product.

"Quality construction": If I had a choice between 2 identical homes, one with "quality" stick construction with fiberglass insulation, and a SIP home, I would choose the SIP construction in a heartbeat. Personal preference. You can't beat them for energy efficiency.

Vacuum leak: I set the system up, checked it after 1/2 hour, then basically left if for the next 6 hours since I used polyurethane glue on some of the SIPs. Some tape came loose, and I didn't catch it.

I've seen this in several threads. Some people want to keep it simple, build their trailer, and go camping. They don't seem to understand that for some it's the BUILDING that's the enjoyable part. Having a trailer at the end of the process is a nice benefit.

[GPW]

Some do actually enjoy the building , some enjoy talking about it ....

Guys , for my time and bucks , Teardrops built in a "conventional " manner viz. outer skin/foam insulation / inner skin ...with the appropriate framing is the time proven way for us small guys just having FUN !!! and with the variety of methods expressed here, simplest seems best ...

The Structural Insulated Panels that are mass produced are somewhat different from our homemade contrivances...just because we stick foam between plywood , doesn't make a SIP , just a sandwich !!!:D

[hightechcoonass]

keep up the good work Captian....I am enjoying the tread

[captainsam]

Artificer

Tell me more about your vacuum setup. I have been busy with a vacation and work so I haven't done much lately on my SIP project, but hope to dive in again soon. I did get a vacuum gage and tested my shop vac. It pulls 2.5 psi ( about 5 in.Hg) of vacuum. I think that would be enough with the PL adhesive to get a good bond. My test panel built with 0.5 psi is pretty darn strong. I wonder if I could seal the setup tight enough to hold the vacuum, or would the vac have to run continously for hours?

I looked at your setup and see you have outdoor carpet as a breather layer. Some of the veneering setups I saw online used a sheet of heavy plywood above and below the veneer panels as a platen...I guess to hold the flat shape. It also had a grid of 1/8" deep saw cuts about 6" apart along and across the platen panels(on the sides away from the veneer stack). I thought these cuts (channels) were designed to create a path for the vacuum to get to all areas of the bag. The carpet seems easier and could cover sharp corners that could puncture the bag.

I was thinking of using a 1" ball valve between the shop vac and the bag so I could isolate the vacuum and shut off the motor (to rest it). Also, I have two vacs so I guess I could alternate running them so one doesn't have to run continously.

My main concern is making a bag that is leak free. I was looking at 4 mil PVC sheet. I was going to try silicone as an adhesive to seal the bag edges.

I covet comments you or others may have about how to best do this before I try it.

Sam

[madjack]

Sam, I don't think that I would use silly-cone to hold/seal the sheeting...I bet it would peel/seperate...I would try duck tape OR we have a 30x50 green house that we cover with 6mil poly...when it rips, we repair it with "greenhouse tape" a clear tape that when stuck to the sheeting is virtually impossible to remove and seems to be unaffected by heat...all I can actually tell ya about it is the fact we get it from a grennhouse supply house and it is simply known as greenhouse tape...
madjack