Jim @ Susan, I read the thread that you referenced in your above post. It is a great thread that I was unaware of. My feeling is, with the scores of various formulations of foams for many different applications, the biggest challenge is finding the right one, and the application personnel to apply. There are probebly foams out there used in military applications that are only sold in tank-car lots, such a product would obviously be out of our reach. But, some formulations may be just what the doctor ordered, as far as use in an AS. It may take some effort in tracking down the most ideal product that is available to us, in small amounts, suitable for us. I am going to keep my own recearch going in this direction, I want to foam my own AS, but know that there are indeed different strokes for different folks, and that no one answer will fit all situations.
I want to use the spray expanding polyurethane foam. Mainly due to the sealing properties. If I say please will you do a test panel of this. Please. I will be glad to chip in for the cost.
Hi FC7039;
As some others may agree with me the pour or spray foam comes in few different chemical structures. This will require you to be aware of many negatives associated with either the application process, and, or it's effectiveness associated with the lapsed time changes in integrity.
The Great Stuff is NOT a true closed cell foam. If installed in area of existing leaks, it will eventually absorb water. With time your aluminum will suffer greatly from corrosion. As a rule, you should seal the leaks at entry point, not at the exit where the water comes in.
The true closed cell Urethane foam is very costly in spray foam. Pour type closed cell urethane will expand your walls. Despite the relief holes you may provide for expansion it will seriously deform your walls. Second, there is no way to fill the roof section unless it is applied from the nozzle. In the end you will be shocked where this stuff will surface.
Even if the Urethane closed cell foam can be successfully applied, aside of all other complications which I have not mentioned, there is a reason why airstreams are riveted and not welded. The reason is that the structure must flex. How many aircraft did you see that are welded? What happens when frame separation goes unnoticed for a while. At each flex point the foam will turn into dust. Frames in Airstream's are not built as stiff platform.
They need to be locked into the shell to form a structural assembly, and YES they do flex.
In my humble opinion I cannot see the reason why anyone would endure so much difficulty and increased cost of insulating, in order to gain a couple of points in R value where the heat loss or transfer through your windows may overcome those gains in R value anyway. I wonder if you could not gain more by installing UV reflective shield film on your windows, than insulating the shell with urethane foam. In addition to that the heat transfer through contact of the rib with inner walls will transfer perhaps only a negligible amount, but that counts as well. The question is, will the increased cost and difficulties associated with such application overcome the cost of couple pounds of LPG per week of camping?
It is nice to be able to tune-up through extensive scientific tests if we have time, money and equipment to do so. Why not just insulate with basic method, and let's go camping. And while I truly respect and admire Zeppelenium's knowledge in that field, not all of us can take the insulating of the trailer to that measure. Even if I was able do do so, how much is there for me in return? I do not intend to ever camp in a 120 degree desert heat because I could not stand to walk out into it anyway. For those who do, there just may be a valid reason. Please remember, I do not intend to disagree with the scientific measures of gain, it is ONLY my sensible opinion. Thanks, "Boatdoc"
Jim @ Susan, I read the thread that you referenced in your above post. It is a great thread that I was unaware of. My feeling is, with the scores of various formulations of foams for many different applications, the biggest challenge is finding the right one, and the application personnel to apply. There are probebly foams out there used in military applications that are only sold in tank-car lots, such a product would obviously be out of our reach. But, some formulations may be just what the doctor ordered, as far as use in an AS. It may take some effort in tracking down the most ideal product that is available to us, in small amounts, suitable for us. I am going to keep my own recearch going in this direction, I want to foam my own AS, but know that there are indeed different strokes for different folks, and that no one answer will fit all situations.
Hi rangebowdrie;
Yes, it would blow your mind of how many different products there are in the foam specialty market. In my ha'y days, I used to drive a Tunnel Hull race boat for Sunoco Fuels [the only Sunoco sponsored boat] APBA 841. Prior to introduction of Safety Capsules, high speed related accidents used to end up in serious injury or death, as the very light and fragile hulls came apart. Sunoco, being concerned about my safety have sent a prominent US aircraft development company to make my boat so called "bullet proof". Two men came in large sophisticated trailer conversion and went to work with 1/2 lbs weight per cubic foot of installed foam. Each tunnel hull was blocked off with special heat shrunk film and 1" hole was drilled at each tunnel hull bow. Boat was hung with bow up at 45 degree and foam was poured in. Excess foam discharge hose was affixed to the pour holes so that the expanding foam would not come in contact with outside gel coat. Apparently there was no solution to clean that excess. Cockpit was then bagged for vacuum forming. Three hours later one man has emerged from a trailer with a 20 lbs mull and piece of plastic in hand. One man held the piece of plastic against the foam filled hull, the other swung the mull as hard as he could while my heart was at my throat. The mull bounced back spinning the man around. Please feel secure now, he said. They had me sign agreement not to allow anyone to have a piece of it, so that it cannot be tested for chemical properties.
All expanded excess foam was collected by them and loaded into their trailer. Not a scrap was left to be found. When I quit racing some years later the boat was purchased back by the company who poured the foam for destruction. There is your sign in today's technology. Thanks, "Boatdoc"
...And while I truly respect and admire Zeppelenium's knowledge in that field, not all of us can take the insulating of the trailer to that measure. ...
Thanks, Boatdoc, but the reason I'm testing is that I agree with you. The ribs and windows kill 95% of any improvement you can make in R-value in the cavities. Maybe foil is better for air leaks and mold, but I don't think it does any more than glass mat in the cold. I'm really more interested in how it does when the outside skin is hot hot hot.
Quote:
...I do not intend to ever camp in a 120 degree desert heat because I could not stand to walk out into it anyway. For those who do, there just may be a valid reason. ...
Acutally, it's a dry heat. But seriously, you are right. The problem in the SW in the summer is that the ambient temperature may be tolerable (95 degrees and 10% humidity is actually OK if you're in the shade), but the sun beating down on the shell can raise the shell temperature to more than 160 degrees. By late afternoon, the insides are at 120. This is not nice. I'm looking for any technique that will reduce this.
The best technique I've found is $150 for a carport tent frame (at the Tools for Less outlet on Tropicana in Vegas) and blue plastic cover! So if you're going to stay more than two days it makes sense to put it up. Better than taking your shell apart to reinsulate.
I think the best move you can make is if you take down some part of the inner shell for other work, eg, taking out windows, put the foil in next to the skin, then the glass mat back in. The combination might be worth it if you've already got your inner skin off.
Hi FC7039;
As some others may agree with me the pour or spray foam comes in few different chemical structures. This will require you to be aware of many negatives associated with either the application process, and, or it's effectiveness associated with the lapsed time changes in integrity.
The Great Stuff is NOT a true closed cell foam. If installed in area of existing leaks, it will eventually absorb water. With time your aluminum will suffer greatly from corrosion. As a rule, you should seal the leaks at entry point, not at the exit where the water comes in.
The true closed cell Urethane foam is very costly in spray foam. Pour type closed cell urethane will expand your walls. Despite the relief holes you may provide for expansion it will seriously deform your walls. Second, there is no way to fill the roof section unless it is applied from the nozzle. In the end you will be shocked where this stuff will surface.
Even if the Urethane closed cell foam can be successfully applied, aside of all other complications which I have not mentioned, there is a reason why airstreams are riveted and not welded. The reason is that the structure must flex. How many aircraft did you see that are welded? What happens when frame separation goes unnoticed for a while. At each flex point the foam will turn into dust. Frames in Airstream's are not built as stiff platform.
They need to be locked into the shell to form a structural assembly, and YES they do flex.
In my humble opinion I cannot see the reason why anyone would endure so much difficulty and increased cost of insulating, in order to gain a couple of points in R value where the heat loss or transfer through your windows may overcome those gains in R value anyway. I wonder if you could not gain more by installing UV reflective shield film on your windows, than insulating the shell with urethane foam. In addition to that the heat transfer through contact of the rib with inner walls will transfer perhaps only a negligible amount, but that counts as well. The question is, will the increased cost and difficulties associated with such application overcome the cost of couple pounds of LPG per week of camping?
It is nice to be able to tune-up through extensive scientific tests if we have time, money and equipment to do so. Why not just insulate with basic method, and let's go camping. And while I truly respect and admire Zeppelenium's knowledge in that field, not all of us can take the insulating of the trailer to that measure. Even if I was able do do so, how much is there for me in return? I do not intend to ever camp in a 120 degree desert heat because I could not stand to walk out into it anyway. For those who do, there just may be a valid reason. Please remember, I do not intend to disagree with the scientific measures of gain, it is ONLY my sensible opinion. Thanks, "Boatdoc"
That is why I put my ideas out there first, to get some feedback. I am not sure of anything I do except for that the fact that I will make misstakes. Besides, if I do everything correct what will some poor sap, I mean, restorer, do 50 years from now.
Hi Zep; You are again on the money. Dense and impervious to UV's tent over your AS will stop lot of radiant heat along with ultraviolet gamma ray's. It is the cheapest form of additional insulation from the sun. But, on the other hand, you will still have contact transfer to contend with in ribs and windows. Thanks, "Boatdoc"
I have occasionally given some thought to the idea of having a roll up or fold up awning that covered over the top of my AS as well as extending out over one or both sides. Of course the AC unit is in the way a bit for what I had in mind but that could be dealt with I guess. Perhaps it would be possible to combine Zeps idea of a car cover type of unit with a simple framework that actually mounted on the roof sort of like a luggage rack.
I have occasionally given some thought to the idea of having a roll up or fold up awning that covered over the top of my AS as well as extending out over one or both sides. Of course the AC unit is in the way a bit for what I had in mind but that could be dealt with I guess. Perhaps it would be possible to combine Zeps idea of a car cover type of unit with a simple framework that actually mounted on the roof sort of like a luggage rack.
Malcolm
Now that is a good idea. If you could take the idea of the pop-up dining canopy and apply it to fitting over and attaching to an Airstream that would be a good idea. Especially if you could get it to fit into a bag like the canopies. You wouldn't need it every time but, when you did you would have it and it wouldn't take up that much space. hmmmmmm...........
However, at rallies, I don't spend much time at all in my trailer. So maybe that cost would be prohibitive.
Interesting idea though.
FWIW, I put all new fiberglass insulation in my Caravel and in cold weather it is quite warm inside. But, during warm weather it doesn't seem as effective and that is where I think he is going with this study here. If and/or when I do another I am keeping a close eye on his test results, as any novice restorer should.
Kudos to Zep for taking the time to study the differing effects of various insulating methods for our Airstreams.
I'm still taking data, but the canned foam so far doesn't look at all that spiffy.
First, it's not that straightforward to make the panel. It takes some care to get a nice uniform load of foam into the space. You'd be surprised how voids between the "tubes" of foam tend to remain, albeit smaller, once the foam expands. Second, the solid foam that makes up the edges of the panels and the aluminum panel itself are impervious to moisture, so the humidity that the foam requires in order to cure, can't get to the interior of the foam--at least not very fast.
Here's what the first foam fill looked like before I trimmed it.
Here's what I found--a large gooey cavity. This cavity would have never filled in, regardless of how much water vapor eventually crept inside.
There's no doubt that I got the first layer of uncured foam too thick. But I think this will be a typical installation problem, not to mention that I put this in horizontal and most Airstream installation will be vertical or nearly so. I think a temporary inside skin of some kind would be required in the vertical installation case, which would further impede the flow of moisture into the foam. See below for manually adding water to the mix.
This tells me that filling large (say bigger than about 1/2 to 3/4" thick) cavities requires several passes hours apart. If you fill a cavity from a hole (that has aluminum on both sides) would require even longer intermediate cure times.
I went back and sprayed the gooey hole with a mist of water, then filled it again with foam and sprayed that with another mist. After a couple hours I misted the whole thing again. The result was a good, solid foam pack.
When I trimmed the second time, I found voids of dime to quarter size, which I filled with small squirts of foam from the can. Then I sanded that face down flat and glued on the second panel.
I'm still working the data, but it doesn't look exceptional for the canned foam. The first numbers for the canned foam panel are good, but not obviously better than glass mat or Prodex. It'll be a few more days before I enough data confidence to post, but I thought these early installation observations might be helpful.
Using 1" fiberglass behind foil would allow you to put a small air gap between the foil and the outside shell. So what should a test panel look like?
1. foil against outside panel and full fiberglass (1-1/2") behind it, or
2. foil 1/2" off the outside panel and then full glass (1") behind it.
Despite the technical attractiveness of #2, it would be a difficult installation [in the real Airstream] and might not last, eg, the tape or other sealing method would fail over time.
The advantage of #1 is you don't really need to seal the foil, since a full fiberglass pack behind the foil would effectively stop/slow any air movement. You'd seal it, of course, but a subsequent failure of the tape/glue wouldn't have a great impact.
Even if the Urethane closed cell foam can be successfully applied, aside of all other complications which I have not mentioned, there is a reason why airstreams are riveted and not welded. The reason is that the structure must flex. How many aircraft did you see that are welded? What happens when frame separation goes unnoticed for a while. At each flex point the foam will turn into dust. Frames in Airstream's are not built as stiff platform.
They need to be locked into the shell to form a structural assembly, and YES they do flex.
"Boatdoc"
Interesting point. So what type of insulation do aircraft use.
Closed cell foam is used in the building industry all the time and can be sprayed horizontal ,vertical , and upside down . I would not think application is a problem ( not talking Great Stuff , but real stuff )
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But seriously, you are right. The problem in the SW in the summer is that the ambient temperature may be tolerable (95 degrees and 10% humidity is actually OK if you're in the shade), but the sun beating down on the shell can raise the shell temperature to more than 160 degrees. By late afternoon, the insides are at 120. This is not nice. I'm looking for any technique that will reduce this.
Better than taking your shell apart to reinsulate.
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