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Old 06-15-2012, 02:11 PM   #85
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Originally Posted by CrawfordGene View Post
For many years contractors told me Thompson's was a terrible product, but CR recently rated it very highly. But I think you get a more impervious surface with an exterior urethane (spar urethane).
Your comment didn't jive with what I remembered of results for Thompson's, so I went to CR's website and looked up the resutls for that test.

It seems the trick is to NOT use a clear sealer. NONE of the clear sealers, including Thompson's, made it past the 3 year part of the CR test. Thompson's WaterSeal Waterproofer Plus Clear Wood Protector got "worse than average" rating for the 1-3 year part of the test, and when you fail that part, the test stops. Rating was 34 out of 100

OTOH, in the top-rated type of protectant (the Solid Stains: they form a paint-like film that shows only texture of wood grain) the top-rated stain was a Behr product, and got 80 out of a hundred, and made it to the 6 to 9 year part of the test.

So all in all, don't bother with Thompson's or any of the clear sealers. Wood can make it to three years all on it's own, from what I have seen...
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Old 06-15-2012, 03:03 PM   #86
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Aage,

Any clear sealer has gotten bad ratings in CR tests over the years. If you want to see the color of wood, you have to use a clear one. Untreated wood turns grey over the years and as long as it can dry out after it gets wet, will last a very long time. CR tests for a solid stain and and semi-transparent stain (I may have the names of the classes wrong) and maybe Thompson's was #1 in the semi-transparent group. I know it was #1 in something.

Coating wood with anything creates problems if water gets underneath the coating (see Wayward's post #79) because it is likely the moisture won't get out easily. This would also be a problem when siding was put on a house without sealing the back and ends—water would get under a perfectly good paint job on the face and the paint would fail and the wood would deteriorate. Now siding is supposed to be coated everywhere. There is also supposed to be an air space behind the siding to allow it to dry. Construction techniques in this and other areas have changed significantly in recent decades.

Whether you can paint or otherwise seal wood in a way that allows no pinholes allowing moisture intrusion is arguable. Some sealants can be thinned and will penetrate pretty far into the wood preventing problems. Other products exist which claim to penetrate the wood all the way through. That would seem to cover all bases, but maybe water could still get in.

Coating the exposed surface of the subfloor can do a pretty good job of preventing leaks from being absorbed into top of the wood. The sides and bottom are inaccessible, so it makes sense to focus on the leaks.

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Old 06-15-2012, 05:52 PM   #87
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Exactly. So if you are going to use that type of material, don't choose clear; it just doesn't have the lifespan of a full tint.

And who cares, anyway: it won't be seen!
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Old 06-16-2012, 08:38 AM   #88
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This discussion has been really helpful to me.. I've played out 100 scenarios in my head and I think I've decided on one. I'm going to build an aluminum torsion box system that includes the subfloor, frame and bellypan with 1/8" aluminum sheet on top, .032" aluminum sheet on the bottom and an array of thin 3" aluminum c channels as well as the existing steel frame to provide the webs of the box. I'll fill all the spaces with 3" thick foam blocks to add rigidity. I'll use regular pop rivets on the bottom and countersunk pop rivets on the top. Where the top and bottom sheet meet the steel frame I'll use stainless rivets. Overall this should be lighter and stronger than the current system and be more resistant to water. I may beef it up a bit near the edges where it ties into the shell. I am trying to figure out the optimum spacing and where to get light c channel for the web. I may make the channel myself with really light weight sheet since the job of the web is only to keep the space of the skins at a fixed distance.
I know that this will be a lot harder than using wood, but I only want to do this once and after seeing all of the challenges people have faced tracking down, repairing and recovering from leaks, I am not going to go down that road.
Tim
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Old 06-16-2012, 09:17 AM   #89
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But Tim, you'll still have to track down and repair the leaks. And may create unforeseen problems. Aluminum mounted on steel is likely to corrode both metals. Leaks can result in mold on/within any surface. Plywood certainly can rot if wet long enough, but it is still a remarkable product when kept reasonably dry. It has been the standard for flooring in residential and RV use for decades. My sense is the effort should be on waterproofing the shell and openings, and monitoring and repairing leaks.

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Old 06-16-2012, 10:00 AM   #90
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Originally Posted by timzog View Post
1/8" aluminum sheet on top, .032" aluminum sheet on the bottom and an array of thin 3" aluminum c channels as well as the existing steel frame to provide the webs of the box. I'll fill all the spaces with 3" thick foam blocks to add rigidity. I'll use regular pop rivets on the bottom and countersunk pop rivets on the top. Where the top and bottom sheet meet the steel frame I'll use stainless rivets. Overall this should be lighter and stronger than the current system and be more resistant to water. I may beef it up a bit near the edges where it ties into the shell. I am trying to figure out the optimum spacing and where to get light c channel for the web. I may make the channel myself with really light weight sheet since the job of the web is only to keep the space of the skins at a fixed distance.
This sounds interesting but a bit hard for me to picture without a sketch. If you are sandwiching rigid foam between aluminum skins, you might think about a structural roofing panel to save some time and money.

Some can be bought bonded to fiberglass or .024 to .125 thickness aluminum

Foam can be laminated to aluminum roof panels.

They can also be found as SIPs with or without an extruded beam molded inside the panel.
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Old 06-16-2012, 01:01 PM   #91
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Quote:
Originally Posted by dkottum
But Tim, you'll still have to track down and repair the leaks. And may create unforeseen problems. Aluminum mounted on steel is likely to corrode both metals. Leaks can result in mold on/within any surface. Plywood certainly can rot if wet long enough, but it is still a remarkable product when kept reasonably dry. It has been the standard for flooring in residential and RV use for decades. My sense is the effort should be on waterproofing the shell and openings, and monitoring and repairing leaks.

doug k
Hi Doug,
I agree that this won't preclude the work of waterproofing and leak checking, but since there won't be any materials that absorb water, I am assuming that water will not stick around as long and if it did may be easier to spot? Dissimilar metals are a significant concern as well. I was thinking about a bead of vulkem on top of the frame before dropping on the top skin to provide some thermal and electrical barrier. To corrode dissimilar metals, water is required, but this doesn't seem to be as big of a problem as plywood rot. I'm going to shout out to the Argosy Minuet owners out there and see if they've observed any corrosion on their composite aluminum floor. It's a different system than what I am imagining, but the corrosion related issues may be similar.
Thanks for your input.
Tim
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Old 06-16-2012, 01:34 PM   #92
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Tim, you are replacing a subfloor of either 5/8" or 3/4" with 3.1575". This will require many modifications to partitions and cabinets and this compounds the labor necessary.

Secondly, why insulate the subfloor if you have heated tanks below it? If you don't have heated tanks, ignore. Insulation should be below the tanks, not above them.

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Old 06-16-2012, 01:59 PM   #93
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Tim, I like your plan. Does your 3" thick system stick down into the spaces between frame members? I assume it does and that you are not adding 3" to the height of the trailer. A sketch would be helpful.

I have been searching around for stock Stainless Steel U-channel for my 1968 window glass trim. There are many suppliers of a multitude of stock pre-made parts like the "C-channel" you are referring to:

Order Aluminum 6063 Channel in Small Quantities at OnlineMetals.com

If you are set on making c-channel and it is really just spacer, you could use perforated stock to lighten it up.

One could use a product like Grace Vycor Deck Protector to separate the steel from the aluminum and keep water from above off the steel frame. It is designed for use on exterior wood decks to separate copper based lumber treatments from galvanized fasteners to prevent dissimilar metal corrosion so it should work well in this application. Also, it heals itself around fasteners. Grace makes a bunch of products like this including their ice and water shield that would work well for isolation.
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Old 06-16-2012, 02:02 PM   #94
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Quote:
Originally Posted by CrawfordGene
Tim, you are replacing a subfloor of either 5/8" or 3/4" with 3.1575". This will require many modifications to partitions and cabinets and this compounds the labor necessary.

Secondly, why insulate the subfloor if you have heated tanks below it? If you don't have heated tanks, ignore. Insulation should be below the tanks, not above them.

Gene
Gene,
The top sheet of aluminum would rest on the frame and the bottom sheet would be beneath the frame so the frame itself become part of the web of the torsion box.
I would not insulate above the grey tank but will insulate below the grey tank and leave an airspace between the two. I'll make a sketch to explain better.
Tim
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Old 06-16-2012, 05:29 PM   #95
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But Tim, you'll still have to track down and repair the leaks. And may create unforeseen problems. Aluminum mounted on steel is likely to corrode both metals. Leaks can result in mold on/within any surface. Plywood certainly can rot if wet long enough, but it is still a remarkable product when kept reasonably dry. It has been the standard for flooring in residential and RV use for decades. My sense is the effort should be on waterproofing the shell and openings, and monitoring and repairing leaks.

doug k
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Old 06-16-2012, 08:47 PM   #96
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A sketch of my plan for an aluminum floor system.

Quote:
Originally Posted by Bunkroom View Post
Tim, I like your plan. Does your 3" thick system stick down into the spaces between frame members? I assume it does and that you are not adding 3" to the height of the trailer. A sketch would be helpful.
Here is a sketch of my plan to make something more like a torsion box as a floor system for my Caravelle. The darker C channel is the existing steel frame. THe little dark boxes are also part of the existing steel frame. The lighter C channel is the aluminum C channel I would add. I would think that 1/8" or 3/16" aluminum subfloor sheet would be rigid enough at less than 1' between members. The top sheet would be attached with countersunk blind pop rivets and the bottom would be attached with standard pop rivets with a larger head. Rigid foam blocks would fill all the cavities between C channels and would add to the torsional stability of the system. To eliminate any reliance on the foam for support, a few perpendicular aluminum web pieces could also be added.
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Thanks again for all the thoughtful input. This forum is an amazing source of knowledge and everyone is so respectful even with different opinions.
Tim
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Old 06-16-2012, 11:27 PM   #97
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Tim, good idea. So, you will actually lose floor thickness relative to the old floor but head height will be the same and all of your interior "walls", etc will fit the same? How will you re-attach the shell to your new floor?
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Old 06-17-2012, 12:46 AM   #98
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Ok, I'm still going with my bed liner and paint. It's done and almost down. So my floor is sealed against moister.

Now, say I had a big water leak and by chance some water did get in through a screw. (like mentioned in post #59) Not much would get in and yes it would be harder for it to get out. But if I didn't have a coating it would soak in everywhere.

Sure it would have a huge area to get out of the wood, but as we have all seen it doesn't. We have rotten floors. So I would rather have a tiny amount get in verses and ton. The floor rots a lot slower my way and only around the screw. (so with all the screw holes rotted out the shell flies off as I go down the road) CRAP maybe this isn't a good idea

Plus the edges are the first place to go, Thus I sealed them up. I'm betting my floor will last longer than the original one did. which was 44 years old when I took it off. Sure it had been patched and was rotten around most of the edge. But it was still hard to get up in the middle

Yep I don't see a perfect solution yet, but mine will surfice and is better than raw plywood with no treatment. At least in my little world it is
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