Fixing rotten wood under rear seat - Fiberglass RV

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Old 09-25-2006, 02:54 PM   #1
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Robert M's Avatar
Trailer: 1980 Trillium 13 ft
Posts: 5
Hi everyone,

I have a 1980 Trillium 1300. I discovered recently that the plywood underneath one of the rear seats (in the storage compartment, underneath the water tank) was rotten, so I cut out the top layer of fibreglass and scraped out the rotten wood. I haven't yet finished the repair - instead, I have a gaping area of exposed fibreglass inside the storage compartment (see pictures).

At this point, I'm wondering what would be the best kind of repair. One thought is to get some replacement 1/2" plywood, cut and fit to size, and then re-fibreglass it into place. This would be equivalent to how the trailer was made.

But to prevent further wood rot, I'm thinking about getting some 1/2" plastic, and simply bolting it in place with the trailer-to-frame bolts and with the eyebolts that were used to secure the water tank in place. That way, there would be no chance of further wood rot in that area, and I wouldn't have to mess around with fibreglassing.

Another option would be to use a strong fibreglass adhesive (e.g., Bulldog Grip) to secure the plastic in place. I'm not very keen on this option, because once that glue dries, man, it's in there for life.

All this is a long-winded way to ask: does anyone know what kind of role the plywood encased in fibreglass plays back there? Is it needed for structural support, especially given how much a full water tank weighs? Would using plastic weaken the trailer in any way, or cause the area to flex or sag?

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Old 09-25-2006, 04:42 PM   #2
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Name: Rob
Trailer: 1980 Bolar 1700
Posts: 92
Hey Rob,
Having replaced the entire floor on my Boler, the plywood is what gives the fiberglass shell structure on top of the frame. You could go with some other method but you have to remember that the piece of floor in question has lasted 26 years. If you splice in a piece of plywood and glass it in properly, you won't have to worry about it for another 20 years. Anything else and you'll always be wondering if it is strong enough or water tight, etc. The other thing you need to think about is how it came to rot in the first place. Is your water tank leaking? The water does not always come from a direct place either. In my case the majority of the water was coming from the door frame and the baggage door. There were a few other places like windows and such but the majors were putting enough water under the vinyl floor that the entire plywood deck was soaking wet in addition to the complete rot in several areas. My Boler is the model with the fiberglass shell pan on which the plywood is placed and glassed in around the edges. Once water gets in there, there it no place for it to go. I remedied that by adding a few drain holes with boat plugs to ensure no water ever gets trapped in the future. I did a few other things but that's another story.

Long an short even though it is a little more of a pain, do it the right way and you won't have to mess with it again.

Good luck, Rob

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Old 09-25-2006, 04:48 PM   #3
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Name: Byron
Trailer: 2006 Scamp 13' towed with a 2005 Dodge Dakota 4.7l Magnum W/full tow package (over kill)
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From the looks of the pictures my guess is that water got into the wood via the bolt holes. A little trick to prevent that. Drill the bolt holes oversize. Glass both sides filling in the holes then redrill the holes at the smaller correct size. This will glass in the edges of the wood where the bolts go through.
Byron & Anne enjoying the everyday Saturday thing.
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Old 09-25-2006, 09:25 PM   #4
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Trailer: 84 16 ft Scamp
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Those plastic decking planks at the Borg have intrigued me with the possibility of becoming a Scamp floor. You could even leave a small gap between each one, as they do on decks and any accumulation of dirt on the floor would be easily eliminated.

As for sealing up the coach, air and water wise, why would you want to, really. Just think, with that system, condensation would never be an issue. Spill coffee or whatever on the floor? No problem. Just hose it out. Rot? Never.

The big issue that discouraged me most was the weight.
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Old 09-25-2006, 11:04 PM   #5
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Name: Frederick
Trailer: Fiber Stream
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As for sealing up the coach, [b]air and water wise, why would you want to, really.
I admit, as a guy, housekeeping is not my strong suit.
I do not relish the thought of having to remove a 1/2 inch of dust from my bed before getting into it.
Better to keep it out in the first place than to have to remove it after it's gotten in.
Frederick - The Scaleman
1978 Fiber Stream 16 named "Eggstasy" & 1971 Compact Jr. named "Boomerang"
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Old 09-26-2006, 06:28 AM   #6
Trailer: Scamp 13 ft
Posts: 44
looks like you're off to a good start robert! its important to clean out the area until you reach good wood on all sides though, otherwise you are just creating a solid spot in a surrounding area of rot which will grow and you won't get a bond. its best to go an extra 3 inches or so into the good stuff. as to refilling; you have plenty of options: marine ply resin encased, plastic (do you mean starboard? its pretty ridgid/nonflex), or just fiberglass, which seems the easiest. since this area is concealed, i wouldn't be too concerned with appearance, meerly structure.
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Old 09-26-2006, 07:51 AM   #7
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Trailer: 1980 Trillium 13 ft
Posts: 5
Wow, thanks for all the replies! I'm always amazed at how helpful everyone is on this forum.

After pondering (read: obsessing) last night about what to do and after reading these responses this morning, I think re-fibreglassing would be the best approach. It didn't occur to me that the plywood gives the shell strength to sit on the frame (thanks to Rob S for that info), but that makes perfect sense - it's such a thin shell, after all.

I'm still undecided whether to use plywood or plastic. I'll be phoning a plastic shop later today to see what they have available and for what price. Plywood is likely to be much cheaper, lighter, and flexible - all plusses. The only advantage to plastic that I can come up with is that it won't rot.

As to where the water came from, I'd put my money on the four eyebolts that hold the water tank in place. This is based on the pattern of wood rot, which seemed centred on those four holes and then spread. After buying the trailer six years ago, I spent many hours trying to prevent water from getting into the storage area both during and after filling the tank. Based on the general state of the trailer when I got it, I'm sure that the previous owner just filled the tank and walked away.

OK, off now to read up on how to fibreglass!
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Old 10-07-2006, 04:09 PM   #8
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Name: Brian
Trailer: Boler (B1700RGH) 1979
Posts: 5,000
If the material choice has not yet been made, I'll add another reason to go with plywood over solid plastic: the plastic types used in building products typically are not stiff enough. Without reinforcing fibres, these solid plastics are not very stiff for their thickness or weight, and will sag. Those plastic deck boards often contain wood or glass fibres, and/or have internal holes to form a box-beam effect. Solid plastic "lumber" is sometimes used for things like park benches and picnic tables, but in very thick pieces under little load, and weight is not important.

1979 Boler B1700RGH, pulled by 2004 Toyota Sienna LE 2WD
Information is good. Lack of information is not so good, but misinformation is much worse. Check facts, and apply common sense liberally.
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