Soft Spot in Cabin Deck - 2000 260DA

[FishOn]

Roland, thanks for the connection to your post. Very helpful. Cool project you did. Many times I wished I had thrusters, and I'm man enough to admit it. Windage is high on these boats and sometimes you may also be short crewed.
I do have to say that that centerline wood piece shown in your photo has me somewhat concerned.. It does look a bit bad. As you know I'm dealing with the aft end of it in my project. I'm worried that it may serve as a moisture conduit that can transfer dampness through the bulkhead (between compartments) and under the galley floor. We'll see what I find as I get further into this. Have you poked around on your galley floor to check for soft spots? As you noted in your thread it seems the only point of this "stringer" is a midline support for the galley deck. Thankfully I think that is correct and it has no structural purpose. Not sure what it does in the box that holds up the table mount though.? Looks like there's a likelihood I'll need to continue this into that forward box..

 

[FishOn]

Also I believe that the rotten subflooring is likely what cause the fiberglass overlay of my galley deck to eventually fail, instead of the other way around. If my hypothesis about the moisture conduit is correct then I suspect that this is a much more common condition than many people think.

 

[Lazy Daze]

Also I believe that the rotten subflooring is likely what cause the fiberglass overlay of my galley deck to eventually fail, instead of the other way around. If my hypothesis about the moisture conduit is correct then I suspect that this is a much more common condition than many people think.

I think you mentioned that the only soft spot was the upper layer of plywood, though, right? That wouldn't jive with moisture from below. In your first picture, though, there are some dark spots that I would want to check out further. Next to the knife, for example.

FYI, if you don't already know this, the kickpanel below the head door is only held on with a few screws. You can feel for the heads that are buried in the carpet.

 

[FishOn]

Well, learning as I go here. Scratch the idea of the liquid conduit. The "midline stringer" as I dubbed it is nothing more than a non-treated 2x2 and it doesn't go through the forward bulkhead into that forward chamber. The bulkhead is fiberglass off. The forward end of the previously mentioned 2x2 was definitely rotten (though very dry). Also there's a piece of plywood layed perpendicular next to it that really rotted (also dry). Everything was encased in fiberglass to protect it. It is possible that the top layer fractured and let water in at some point in the past. And that's most likely what happened. That's all a mystery at this point. My hope is to compose a summary of what I'm finding to post here for future reference. Now I just need to decide if there's any value in refiberglassing..? Probably not but itll have to be sealed very well with something that hopefully won't fracture. Oh, yeh, had to remove that panel to remove the carpet. Those screws are HARD to find. There were 6 holding it on.

 

[FishOn]

I can envision some yahoo in the past catapulting themselves into the galley by swinging in holding onto the top of the door slide. Then landing hard enough to break the floor... Who knows? Back to the topic at hand there really wasn't THAT much decay fortunately. Should be a relatively easy repair. There is a lot of fiberglass layers. Not sure if I should refiberglass that portion for rigidity purposes? I suppose there may be some amount of lateral support offered by the fiberglass layers, but I really have no idea. Bottom line I dont know if the fiberglass is there for waterproofing, structural support by spanning/bonding either side, or both.?

 

[Lazy Daze]

Check back above about what I mentioned about glassing vs just resin, for reference. But, glass, by itself, unless really thick, doesn't add a whole lot of structural rigidty unless it's also on the bottom of the wood. Then it does add a lot of structure - even just a thin layer top and bottom will add meaningful structure. Since you're still wondering - and will probably continue to wonder in the future if you DON'T add glass... I think you know your answer... add some glass. Don't worry, a little project like this is super easy.

 

[FishOn]

Thanks Lazy Daze. Yeh you are likely right about that. The cabin floor is indeed constructed like you mentioned. There is fiberglass encased foam, a thin layer of fiberglass above, then the plywood. On top of this is a thicker layer of fiberglass, then carpet. I thought maybe there might be a quicker/easier way to go about this but I suppose it's true that sticking with the original design and materials is probably best. I hear what you are saying about the dark spots shown in the photo. There are several throughout the deck under the carpet. They all feel very solid with a screwdriver though. So now I'm deliberating on how much I want to take out. I have about 1/4 of the deck removed at this point and there isn't any additional rot beyond the forward end and the top plywood that I originally showed. A couple questions to you.
- is there any trick to bonding the new fiberglass to the old?
- Would it be better to use a synthetic material like starboard as opposed to plywood? Does the fiberglass bond to it like it does plywood? For a piece of starboard this small it may actually be cheaper than buying a full sheet of marine plywood.

To anyone doing this in the future the oscillating tool that was suggested (thanks Lazy Daze!) Is indeed a good tool to reduce dust. It's also pretty easy to control so you dont do something unfortunate. Correspondingly it is pretty slow going (which is both good and bad). Make sure to get several carbide cutting blades and go slow so they dont heat up too much. The unit I got and would recommend is:

https://www.homedepot.com/p/RIDGID-...lti-Tool-with-Tool-Free-Head-R28602/206824272

I think this is currently one of the best values for your money.

 

[FishOn]

Not sure if anyone is still following this thread. I'm still working on defining what needs to be done and hopefully some warmer and drier weather. Another question. Since this is a deck that supports us walking on it would I need to cut out the entire panel of plywood (from the forward bulkhead back to the stair? Or would it be possible to just remove the damaged area and replace a portion? In the latter case there would of course be a seam, but it is all encased in fiberglass (and i suppose i could also glue the adjoining sections). Also curious if polyester resin would be better to allow some flex or if epoxy is better in all situations? TIA

 

[Lazy Daze]

Fish, a "core" (glass/wood/glass) gets it strength not from the actual core being all one piece, but by the separation of the two glass layers and solid adhesion of all three pieces. That's what prevents flex - the separation of the glass layers. Take a look at my post above of my Grady floor. You can see the "shadows" of the hundred or so 8"x8" square pieces of plywood. Until that floor got saturated, it was just as strong as if the wood was a single piece. The key is getting good adhesion bewteen the 3 layers. You can use something like a lightweight, 1-1/2 oz chopped strand mat to help with adhesion. Thickened resin is another option. Fully wet out the new plywood first, though (including edges) - do it a couple times till the resin no longer soaks in (it'll still be shiny/wet after about 10 minutes)

No, starboard won't work. You could use Coosa or Divinycell. But you could also use regular plywood - that'll be just fine for this project, especially if you first fully encapsulate it.

Poly or epoxy - your choice - both work equally well for this project. Epoxy is more expensive, but a little easier (and definitely less smelly!) to work with. If you use epoxy and chopped strand mat, be sure you get mat that works with epoxy as otherwise the binder in the mat won't get broken down.

Roughly sand the old fiberglass and it will bond nicely with the new. The floor pieces I removed in my Grady were reused.

Since you'll be putting either carpet or some type of vinyl floor back down, you have the added benefit of not having to be pretty with your repair!

I think that was most of your questions?

 

[sbw1]

Rather than fly blind on this and listen to ideas based upon speculation, I would get on the horn with SR and see if they have the design drawing of your boat. Tell them what you are finding and pick their brains for a solution. I had an issue like this with limber holes on my 370. Called the company and was connected with the guy who supervised the build of my boat and had actually been on the boat several times. He sent me a copy of a blue print marked up with how to fix the issue. It was truly amazing service. I think it took me maybe two hours to connect with him and the advice was spot on.

 

[FishOn]

Thanks Lazy Daze for that detail! This is extremely helpful. I'm also beginning to understand what you are talking about. Getting this information from someone who has "been there" is priceless and very appreciated. Would you suggest regular plywood over treated?
SBW1, good suggestion. I do have the drawings you mentioned. Most of my recent inquiries have more to do with application of the repair. Certainly a big credit to searay to offer the support on their boats (as you mentioned). I see some things in the build that certainly should have been done better, but the support certainly seems to be there for owners. That is worth a lot. I think that in boat ownership you eventually know through and through every aspect of the vessel, or should. This results from inquiry, repair, and/or rebuild. It comes with the territory.