The Science of Soggy Decks

[Ocean Girl]

I've replaced rotten core and also done this drill and fill method, the OP asked for cheap and easy, so I gave him my cheap and easy fix experience.

Why is the dehumidifier not recommended more, I've dried out some big time wet hull and deck with a simple dehumidifier, never needed a vacuum system or heater. But I have only repaired 5 or 6 boats, so not a pro.
Erika

Ps
My trawler fix is still going strong,( she says without a hint of defensiveness ) though They did have to repair two areas near the stern a couple years later.

[unbusted67]

Originally Posted by minaret

I like to get my moisture meter out and take readings about one every square foot over the whole surface in question, with extra detail on areas in question. I use a sharpie and tape, or a greasepencil or chalk depending on the surface to write down each measurement. We call this mapping out a deck or hull. When you are done you can see where all the cored areas are, where the solid areas are, where bulkheads are, tanks, areas of saturation, etc. With some experience a good map will tell you everything you need to know, generally speaking. I hope you are doing this and not just taking a few readings here and there. If you can post some pics of your "map". Sometimes a builders plan can help you interpret what you are seeing.

Funny you should mention it but this is exactly what we have done. It is pretty evident that whatever moisture is in there has gotten in through the jib track. It is also obvious that this was never bedded properly ie no drilled out holes filled with epoxy.

The only strange thing to note is that the moisture readings seem to get higher the closer you get to the cabin top, in other words, up hill. There is no cracking around the joint of the cabin top and the cored deck so the only explanation is that the water wicked up there. On the downhill side you still get moisture readings that become less and less as you go down towards the rail. I have discovered some slightly discolored balsa core that is the hue of a nice pine mulch. Nothing black yet though. I haven't really found any delamination either. But don't have the ear to sound the deck. Thanks for your help.

Originally Posted by Ocean Girl

I've replaced rotten core and also done this drill and fill method, the OP asked for cheap and easy, so I gave him my cheap and easy fix experience.

Why is the dehumidifier not recommended more, I've dried out some big time wet hull and deck with a simple dehumidifier, never needed a vacuum system or heater. But I have only repaired 5 or 6 boats, so not a pro.
Erika

Ps
My trawler fix is still going strong,( she says without a hint of defensiveness ) though They did have to repair two areas near the stern a couple years later.

And thank you Erika, I am totally down with your quick n' dirty methodology, although I have to say it sounds like more work than just pulling up the deck!!!! I can envision you in a garden of syringes tending your little flock. It totally sounds like something I would do. I can guarantee there will probably be some git rot in our near future.

[David_Old_Jersey]

Have you tried the meter on places you know are not wet? - especially if you have any "solid" fibreglass areas......or even make up some test pieces to get a handle on what your meter reads for wet and dry.

Given that your eyes (and hands) are starting to tell you one thing and the Meter another my first step would not be to start cutting the deck open.

[unbusted67]

Originally Posted by David_Old_Jersey

Have you tried the meter on places you know are not wet? - especially if you have any "solid" fibreglass areas......or even make up some test pieces to get a handle on what your meter reads for wet and dry.

Given that your eyes (and hands) are starting to tell you one thing and the Meter another my first step would not be to start cutting the deck open.

Yes I have, the meter is working fine. As I said in the post above I am finding some slightly discolored coring around the jib track now.

[CharlieCobra]

We just got a Tayana 37 to pull the teak off of and re-core where needed. On the H-54 we did, I cut out a section of very mushy, wet balsa, let it dry for a day, saturated with smith's and tested it. It was solid as a rock afterwards. That was just for sh%$s and giggles, we did replace the core with new. On the SC-50 we have now, there was a piss poor repair of a collision puncture in the hull that, once I cut out the outer glass, was wet for about 6" around it. I re-cored and re-glassed that. Every instance is different.

[colemj]

Originally Posted by CharlieCobra

I cut out a section of very mushy, wet balsa, let it dry for a day, saturated with smith's and tested it. It was solid as a rock afterwards.

Did you apply the epoxy into the grain or across it? Balsa will readily take up epoxy from the endgrain, but epoxy will not penetrate very far across the grain. That is why trying to saturate balsa through holes in the deck does not work very well.

Mark

[hummingway]

How about a microwave drier: http://www.cruisersforum.com/forums/...ore-36006.html

I think a lead cup and helmet might be a good idea (don't fall overboard wearing them).

[Cheechako]

I think you will find that heating with a few holes will not work at all. The moisture just condensates and sticks around. If the deck is flexible then the bond i s gone. It may be possible to redo it from below. Cut out panels for access where you can, scrape out the muck, make tooles to dig deeper into the areas you cant cut out etc etc. Depends on where and how much furniture there is where your problems are. I did this on a whole V berth overhead and part of a hanging locker once. It's a mess but doable with enough ingenuity...

[unbusted67]

Originally Posted by Cheechako

I think you will find that heating with a few holes will not work at all. The moisture just condensates and sticks around. If the deck is flexible then the bond i s gone. It may be possible to redo it from below. Cut out panels for access where you can, scrape out the muck, make tooles to dig deeper into the areas you cant cut out etc etc. Depends on where and how much furniture there is where your problems are. I did this on a whole V berth overhead and part of a hanging locker once. It's a mess but doable with enough ingenuity...

I think you are right about heating a few holes. I am getting no better moisture reading after 24 hours of heating in one place. Imagine doing the hole 12 ft jib track?

I also want to amend my earlier statement and say that it isn't balsa cored, but rather, plywood.

I almost think I have better under deck access than above. But what of gravity? When you are shlopping epoxy in to replace your core isn't it falling down and hitting you in the face and getting all over everything?

[Cheechako]

But what of gravity? When you are shlopping epoxy in to replace your core isn't it falling down and hitting you in the face and getting all over everything?
Welcome to boating! Ha Ha... It's not that bad actually. Once everything is out and dry. Brush the overhead area you will be installing the core on with your mixed epoxy resin with a big brush or roller. Do only that area you can get done before it sets off. Then brush the sections of balsa or foam core on the top liberally with resin and put them in place. They are light enough I had no problem with needing to hold them up. Getting all the core up there and in place is likely a one day job... It's hard work so dont plan on doing everything in one day. The harder part is fiberglassing over the core, here gravity is your foe for sure. It's amazing how droopy a square foot of glass cloth with resin on it can be! I ended up doing 18" strips full width of the deck over head in the V and half width further aft. If you lay this cloth on large cardboard pieces cut to size, apply the resin and use the cardboard to get it up there. You need a resin roller (metal with grooves.. forget what it's actually called) and that and a sqeegee will wet the cloth to the over head... It's a good option if you dont want to have to paint your deck etc! cover everything prior to working with plastic sheeting taped in place!
I actually used regular laminating resin rather than epoxy... mostly because some areas that I couldnt cut open, I gouged the old mush out of there with a hook shaped long screwdriver like device. In those areas I carefully shoved in balsa squares and liberal amounts of automotive bondo... the bondo is compatible with normal resin....

[minaret]

Originally Posted by Cheechako

In those areas I carefully shoved in balsa squares and liberal amounts of automotive bondo... the bondo is compatible with normal resin....

I do most of my deck core replacement jobs in poly. Next time try Core Bond Core-Bond / Poly-Bond Instead of regular bondo. It has a very slow potential cure time, though you can mix it hot, and it weighs half as much as regular bondo and is more flexible without cracking. Cheap too. Specifically designed for this app.

[bazzer]

How about a organic approach, you drill a few holes and put some Gribble Worm lava down them, leave it wet for a while and the worms will make enough holes for resin to penetrate everywhere. Don't know of a good source of Gribble Worms though...They were common in the sixties with all the plywood boats being built then....

[CharlieCobra]

Originally Posted by colemj

Did you apply the epoxy into the grain or across it? Balsa will readily take up epoxy from the endgrain, but epoxy will not penetrate very far across the grain. That is why trying to saturate balsa through holes in the deck does not work very well.

Mark

Across the end grain.

[colemj]

Originally Posted by CharlieCobra

Across the end grain.

Really? You got that much epoxy penetration across the cell structure of the epoxy? That is unusual. Balsa readily soaks up epoxy (and water) from the endgrain, but generally not much from the sides of the "long grain" (I don't know the word for that).

In fact, it's resistance to soaking up things "sideways" is one of the reasons endgrain balsa is used and not, for example, quarter-sawn balsa.

Mark

[minaret]

I've cut open and properly repaired decks which were "scabbed" in that way. The job always ends up going south sooner or later, it is a temporary stopgap measure, not a permanent fix. When I peel a skin off a job which has been epoxy injected, it's immediately apparent how far the epoxy did or didn't penetrate. I'm never impressed. In fact, it's such a PITA for us to grind out all the crap which has been injected to make room for a nice clean, fair, core replacement, that we charge substantially more to fix the amateurs mess than we would to do a normal core replacement. A few times I've seen jobs where a great deal of injection was done, in one case thickened with cabosil, which is almost impossible to grind/chisel out without destroying the delicate inside skin. It was a serious issue and probably cost several times as much as a proper job would have. A deck needs to be lightweight, strong, flexible, and fair. Injection is exactly the wrong answer for all of those issues. Personally I think a deck core replacement job can be a boon in disguise; it is an opportunity to get all that organic rotting crap that never should have been in the layup in the first place out and replace it with something worthwhile, like a foam core or coosa board. Once done right the boat is good for at least the life of the owner in that regard, no more ticking timebomb in the deck. And injection will certainly not guarantee that you will pass survey, especially with a surveyor who clearly knows how to use a moisture meter. I guess this is the case, since his meter said it was wet and you didn't believe it, but now you are slowly being convinced he is right as you look more. The meter never lies, you just need to know how to spot false readings.