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Old 09-29-2006, 10:08 AM   #1
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floor repaired

I have repaired the plywood and wanted to post the pictures that were promissed.
The first thing was to make a repair to the Plywood where a leak got to small area near a rear access door. I simply repaired the area by laminating new wood with West Systems Epoxy. I then sealed the plywood with a thinned out West Systems Epoxy. You use Denatured Alcohol to thin out the Epoxy. The Plywood is now good for another 50 years--hard as a rock!
This repaired and sealed the Plywood so that I could to lay the Vinyl Squares under the Furniture. The Furniture is all still together so the original layout will be maintained.
Steve
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Old 09-29-2006, 10:17 AM   #2
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Fiberglass is the best way to fix these floors
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Old 09-29-2006, 10:40 AM   #3
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I respectfully disagree with you.
Fiberglass covered Plywood has some potential problems. I have inspected numerous Boats that were built with Plywood and then covered with FRP (Fiberglass Reinforced Resin).
Plywood and FRP do not expand and contract at the same rates. The FRP will shear and create voids. Imagine the Humidity being high and here you are happily going down the road with your Airstream flexing as it is being towed along. There are ways to limit this problem but even those are not as successfull as one would hope.
Another problem is that if you do decide to cover the Plywood with FRP and then drill a hole for a fastener you have defeated the purpose. You now have allowed a way for moisture to get into the Plywood and help create delamination.
The process that I explained is the same process used to repair boats and does a much better job over the long haul. While FRP is easier and faster it is not better.

Here is a link to the website; http://www.westsystem.com/

If you need to use the cloth say under a shower...then I would recommend to use monel staples to hold the Cloth to the Plywood to keep it from shearing and then use Epoxy Resin instead of Polyester Resin. But I would recommend that one would first seal the Plywood with a thinned out Epoxy Resin.
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Old 09-29-2006, 11:07 AM   #4
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Glass the way to go, do it one time and forget it!

I respectfully disagree with you.


<Fiberglass covered Plywood has some potential problems. I have inspected numerous Boats that were built with Plywood and then covered with FRP>


I have been building and working on boats with fiberglass all my life, the last boat I sold was 26 years old built by WD Schock out of CA. There was plenty of glass covered ply in the structure, never had a problem.
I now have a new Beneteau that also has glass covered ply.

So this method is currently being used.

<Plywood and FRP do not expand and contract at the same rates. The FRP will shear and create voids. >

What is this conclusion based upon? The 26 year old boat expanded and contracted thousands of time and took a worse beating in waves than a TT will going down the road IMHO.


<Another problem is that if you do decide to cover the Plywood with FRP and then drill a hole for a fastener you have defeated the purpose. You now have allowed a way for moisture to get into the Plywood and help create delamination.>


That may be a fact for balsa core not plywood is will only absorb so much of an area and stop. That is the lesser of the two evils now it can NOW absorb water at will, then rot with the wet pink insulation (that’s another story)

<While FRP is easier and faster it is not better. >

What is in your opinion?


<If you need to use the cloth say under a shower...then I would recommend to use monel staples to hold the Cloth to the Plywood to keep it from >


The staples will not stop shearing?,

<But I would recommend that one would first seal the Plywood with a thinned out Epoxy Resin to seal the Plywood.>

When you lay down say 6 OZ cloth and wet it out you are sealing the ply at the same time. You don’t need to do it twice?

I will be posting my pic’s up in a few days of a glassed floor, please take a look at that time and tell me if you still disagree.

ps: I will also be forming a shower floor pan to contain water on the floor of the bath.
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Old 09-29-2006, 11:31 AM   #5
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I am not jumping in the middle of this - nopers, nuh-uh, no-how.

Let us remember 35 or 45 year old exterior grade plywood is not the same as new-made marine grade plywood. Apples and Oranges. Don't start, wont be none.

If you have new wood, by all means use a vinyl ester resin (not epoxy) and encapsulate the edges etc with that nice rock hard resin. If you have ancient exterior grade plywood with the 'miracle water-proof glue" (HA!) use what works for you untill its new flooring time, which will be way too soon, looking at my 35 year old flooring.

Thank you, see? I didn't get in the middle of it.
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Old 09-29-2006, 11:39 AM   #6
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Just FYI the only difference between marine and exterior grade ply is that the intermediate layers of exterior has some voids where knots were.

In marine grade all those knots are cut and filled with a plug they kind of look like a eyebrow, on all layers.

The glue is the same, so exterior grade is fine for this application and less expensive.

Resin info

EPOXIES

Epoxies represent some of the most versatile resins available to the composite manufacturer. Generally, in all categories of work, the builder/repairer will realize the greatest degree of bond strength, waterproofing and toughness with well formulated epoxies. New generation MAS Epoxies are VOC free and have curing systems which are phenol free (representing a safe step forward for all resin users). Atmospheric moisture is of little concern, as blush-free MAS systems allow builders and repairers to laminate and bond with little or no surface preparation between applications as long as mix ratios are followed and mixing is adequate. Shrinkage of MAS epoxies is below .03% eliminating prerelease. In the case where a part, originally manufactured utilizing polyester or vinylester, has yielded to strain and cracked, a well-reinforced epoxy repair will tenaciously hold to the substrate with 2000 psi strrength (vinylester: 500 psi). Many high strain repair areas and lightweight parts must flex and strain without micro fracturing. MAS resins have the ability to flex with the fibers while maintaining permanence and adhesion. Whether a part or repair is made of wood, carbon, Kevlar, fiberglass, core material or hybrids of the above, MAS Epoxies will wet and permanently stick to the composite. Just a quick note: one composite manufacturer recently eliminated a peroxide cured and extremely pricey custom-formulated aerospace adhesive (fancy packaging and all) with a standard MAS product. The benefits included elimination of VOC's from the assembly area, reduced price, increased strength, and elimination of shrink problems from the bond line. When MAS Epoxies are used for a chemical resistant barrier (barrier coating) the finished coating system has excellent resistance to water uptake (below .5%) and the user can be confident that subsequent finishes will stick to the new epoxy and the epoxy will stick to the surface. New generation MAS epoxies feature many of the advantages of low viscosity and accurately tailored gel and cure times. Permanent repairs and the highest quality custom aerospace construction have been enjoying the advantages of epoxies since the sixties. MAS brings these advantages to the builder and repairer at room temperatures, and we're gearing up for more surprises in the 21st century.
VINYLESTER

Vinylesters represent a resin development step in the right direction. While still utilizing a polyester resin type of cross-linking (i.e. peroxide cured). These hybrid resins are toughened with epoxy molecules within the backbone. Shrinkage is less of a concern with vinylesters and prerelease of the part from the mold is reduced. The toughening effect of the resin modifications makes for a better resistance to micro fracturing and some of the secondary functionality of the backbone assists in adhesion to substrates. Vinylesters are capable of forming secondary bonds around 500 PSI (MAS Epoxies 2000 PSI). Resistance of vinylester resin to moisture is good and some commercial barrier coatings have been marketed utilizing this resin family. The down side of the vinylesters include sensitivity to mixing, handling, high VOC's (in the form of styrene), atmospheric moisture and temperature sensitivity (sometimes it just will not cure). Good tough vinylester is also quite pricey when compared to polyesters, in fact the dollars per pound approach that of epoxies. Vinylesters definitely represent an improvement over polyesters when considering standard peroxide curing, however adhesion to dissimilar and already cured substrates is still far below perfect and many vinylester hulls suffer similar massive delamination of the hull skins from core and bulkhead substrates. Additionally since almost all barrier-coating applications are after market it is essential that the coating system have maximal bonding strength to the original substrate. Vinylester resins only show good fiber adhesion to standard glass fiber, standard low adhesions to more exotic fibers (Kevlar/carbon fiber) and wood.
Open surface curing of both vinylesters and polyesters requires a surfacing agent. Subsequent applications require careful surface preparation if reasonable adhesion is to be achieved.
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Old 09-29-2006, 11:48 AM   #7
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I am only speaking from experience. My profession is a Marine Surveyor and I look at allot of boats every week. FRP covered Plywood has potential problems and I see Dry Rot under FRP all of the time. Insurance Companies do not want to insure a FRP covered Plywood Boat. I think that you may be confusing a Plywood cored FRP with a FRP covered Plywood.
It is OK to disagree, but please look at the West Systems Website, this has become the industry standard with Wooden Boat Construction. If you want to use Polyester resin go ahead, it is not my Airstream. PS you forgot to include resin info on Polyester Resin, commonly refered to as "Fiberglass".
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Old 09-29-2006, 11:51 AM   #8
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All we're doing here is exchanging ideas, that's why it's called a forum.

But frp covered ply in a boat is a bit different than in this application don't you agree?
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Old 09-29-2006, 12:03 PM   #9
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Not really, the Plywood is being used as a medium. I simply want to apply all of my knowlege in the repair of my Airstream and use the best materials I can. I am not rebuilding it to re-sell, I am rebuilding it to keep.
I looked at the pictures in this forum and all of the Plywood looks to have been damaged from water leakage problems. These smaller Airstreams have become very collectable and why not use the newest technology to repair them? vintageairstream.com has a link to West System Epoxy so this is not a new idea in the restoratioin process.
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Old 09-29-2006, 03:20 PM   #10
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Here's my problem:
since the critical structural element (in my mind) is the plywood under the exterior walls, which is attached to the bottom wall channel which is riveted to the skin and attached to the vertical studs/struts, then laminating plywood on top of the old plywood (unless you actually lifted the trailer off of the old plywood and slipped the new under) wouldn't help anything except add more weight to a failing structural system - maybe you did lift the trailer?
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Old 09-29-2006, 03:23 PM   #11
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. . . and if this was in a small area (I assumed you laminated a new layer on top of the whole floor) then ignore my previous post
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Old 09-29-2006, 08:56 PM   #12
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Mark,
Take a look at the first picture. I removed all of the soft wood, there wasn't that much so the repair was then easy. The completed repair area was very small about 8"X 12". I used epoxy to glue the new 1/16" laminates and scarfed them in using about a 12:1 ratio and staggering the joints. This type of scarf should be at least as strong as new wood.
In 1958 the 18 Footer did not get a shower, thankfully! I will not add one and so this trailer does not have the typical rot problems associated with freshwater intrusion. We are going to shower outside like GOD intended.
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