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offgrid ![]() Senior Member ![]() Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
![]() Posted: 23 Feb 2019 at 7:29am |
Spray on two part closed cell polyurethane foam was my original suggestion and is still my favored approach. But texman is concerned about it for several reasons he has identified in an earlier post.
You don't want to use plain old open cell "great stuff" type foam, it will become water logged. And it will be important to test to be sure it adheres to the polyethylene tank, its hard to get anything to stick to that. If the tank is filled with water when you spray it I can't imagine there would be any tank distortion, its going to be like spraying foam on a rock
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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lostagain ![]() Senior Member ![]() ![]() Joined: 06 Sep 2016 Location: Quaker Hill, CT Online Status: Offline Posts: 2595 |
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What about using polyurethane rigid foam. You could spray it from cans and to ensure complete coverage, put a few access holes into the base or "tray" that will be mounted below the FW tank. The hardest thing with that kind of foam is to get it evenly applied so that you don't have excessive expansion that could distort the FW tank. The problem I see with polystyrene beads is that it's hard to keep them where you want them once you spray them inside and there is no way to bond them to one another.
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Never leave footprints behind.
Fred & Maria Kearney Sonoma 167RB Our Pod 172 2019 Ford F-150 4x4 2.7 EcoBoost |
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offgrid ![]() Senior Member ![]() Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
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Re: using loose fill polystyrene, there is an issue with pour filling it into cavities due to static buildup. So its going to be an problem with filling an irregular cavity in bag surrounding the water tank with beads or peanuts too. The beads are going to have to be blown in to get a nice tight pack I think. A shop vac used as a blower could work, or you could make up a gun using compressed air to draw the beads in at a venturi. Here's a commercial gun that does that but its not cheap.
And a home made gun using a show vac as a blower. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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offgrid ![]() Senior Member ![]() Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
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The tank will get condensation on it overnight in warmer weather. I've seen it on mine. Insulation will reduce that a lot of course, but I'd be a little afraid of an impermeable membrane. Maybe just punch some drain holes in it?
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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texman ![]() Senior Member ![]() ![]() Joined: 24 Jul 2014 Location: TeXas Online Status: Offline Posts: 446 |
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thanks for the feedback. do you think that condensation is a concern with the metal or "unbreathable" liners ? Water in the tank will be warmer than outside the enclosed space. I like the idea of using a liner like TPO and enclose it like you said with the peanuts or something. (good idea on peanuts BTW) I like the metal too and that is good idea to form the insulation. Not sure i want to subject myself to removing the tank, but that would work well. but it would cost more and TPO is super tough and should be easier to attach. metal could have access doors/panels which would be nice too. i think i have a source for TPO from a roofer friend. Comes in 10 ft wide rolls. he is gonna donate it so worth a shot. |
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lostagain ![]() Senior Member ![]() ![]() Joined: 06 Sep 2016 Location: Quaker Hill, CT Online Status: Offline Posts: 2595 |
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What about fabricating a metal tray to mount under the trailer with enough space between it and the FW tank to allow insulation. Remove the tank to use as a mold [with mold release smeared all over it] and fill the space between the tank and the tray with foam insulation, then when the foam has cured, remove the tank, reinstall it, then mount the tray with the insulation below the tank. If you need access points and such you could allow for them in fabrication of the tray and application of the foam. The insulation would adhere to the tray, not the FW tank. I haven't a clue whether this would work, but it seems like a possible approach as you could fabricate the tray to be pretty tight against the underbody so it would not let in much moisture.
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Never leave footprints behind.
Fred & Maria Kearney Sonoma 167RB Our Pod 172 2019 Ford F-150 4x4 2.7 EcoBoost |
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offgrid ![]() Senior Member ![]() Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
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My thoughts:
The tank would be the last thing to freeze and even if it did it probably wouldn't hurt anything, especially if it was kept pretty full (not not so full that the ice had nowhere to expand to). But as it is in the heat recirculation loop it will never have a chance to freeze anyway, since it needs to be kept above freezing or the pump supply line can freeze up. Ergo, the need to insulate it to keep the propane consumption down. I'm pretty sure it will be high otherwise, but its not going to hurt anything to wait and see. I'd add to the cons with the options where the insulation is directly attached to the tank the need to adhere the insulation to the poly tank surface, which can be problematic. A pro for these is there isn't any need to cover every inch of the tank surface, you could leave access points open for servicing fittings, sensors etc. To the cons for the ones which aren't attached add the need to create a tight seal over the whole tank against wind entry. On the spray foam, I think its around a $100 option too so probably not any different from most of the others. And personally I don't care what it looks like under there, its not like its someplace I plan to spend a lot of time ![]() Your idea of using a flexible liner of some type reminded me of another possible option. When I insulated the floor of my (elevated) house a year ago I had to do it from underneath and wanted an easy and inexpensive way to get a higher r value than using the pink stuff. I stapled landscape cloth between my floor girders and filled the entire 20 or so inch space with blow in insulation on top of that. Then installed the plywood underpinning. So how about a "bag" of landscape cloth filled with some type of loose fill water resistant insulation, like maybe polystyrene packing peanuts? That would be very inexpensive, give a high r value, and be removable in future just by pulling the bag and insulation off and throwing it away. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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texman ![]() Senior Member ![]() ![]() Joined: 24 Jul 2014 Location: TeXas Online Status: Offline Posts: 446 |
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Insulating the fresh water tank discussion: Is it really necessary and/or beneficial to this project?
If insulating is to be done, here are what is see as viable options and their pros/ cons:
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offgrid ![]() Senior Member ![]() Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
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Looks like pipe insulation in sheet form. Should be good if it doesn't absorb water and you can figure out a good way to attach it to the fresh water tank. You would need 2 pcs. Its not critical to get all the gaps perfectly closed up if you do it this way. If you use the boards and box in the tank it would be because there would be an air gap between the insulation and the tank where cold air could blow through.
I was thinking to use these kits. Each is supposed to be 12 board feet, I don't know if the folks that are complaining about them don't know what a board foot is or if they really don't have the foam volume they claim, but 2 kits should be enough. Should be done only in warm weather for sure.
Or a couple of these, ppl seem to be getting around 10-12 board feet out of one kit. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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texman ![]() Senior Member ![]() ![]() Joined: 24 Jul 2014 Location: TeXas Online Status: Offline Posts: 446 |
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https://www.zoro.com/k-flex-usa-insulation-sheet-36-x-48-x-34-in-6rsx3x4068/i/G1542721/
I think this might be a good tank insulation material |
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