The Science of Soggy Decks

[colemj]

If you truly have wet decks, over large areas and delamination, the only way to fix this is to cut it out and recore it. I have tried just about every way to fix wet decks and the only one that works for good is recoring.

Not to belittle Oceangirl's work, but doing what she did only accomplishes (temporarily) the reconnection of the two skins through epoxy pillars she formed by pumping epoxy into drill holes. Thinned epoxy (penetrating epoxy) will not saturate balsa core more than a few millimeters. Any core material still left will no longer be structural and will still begin to rot. And this type of fix adds a lot of weight to the boat in the wrong place to add weight.

If you only have delamination without wet core, then Oceangirl's procedure can work well, because most of the epoxy will flow out between the skins and core and help to reattach the two.

If your core is wet, the first thing you should do is find out why and stop further water from coming in. If the core is not completely saturated and rotten (doesn't sound like it is), then I personally would just leave it alone after stopping further water ingress until it becomes either rotten or delaminated. You would be surprised at how well even wet rotten balsa stays laminated.

If your core is saturated or rotten and delaminated, then do yourself a big favor and cut off one skin, recore and reattach the skin. You would be surprised at how easy this procedure actually is. Even though it sounds like major surgery, it is much easier than all the other "tricks". And much stronger and longer lasting.

Mark

[David_Old_Jersey]

My experiance of "fixing" wet core is limited (current boat no have - part of the reason why I bought her ).....but have done similar (albeit on a far smaller scale!) as OceanGirl did........except with a lot less drying out .

We were tackling wet core that originated from around the Anchor winch, including the chain hole (I always forget what that is actually called ) - easy to tell that the core was wet - the deck under the winch had compressed .

What we did was seriously overdrill the existing fixing holes (well above finger size) scraped out the wet core as far as we could (an Allen key worked well) - and then not worried too much about what we couldn't reach (on an "Out of sight out of mind basis" ).

Then blanked off the underside and filled the gaps between the deck with thickened epoxy (thick enough so didn't run) - stuffed in using a finger (one of the reasons for overdrilling the holes above finger size!)...then we filled the bolt holes using the same technique ("technique" sounds a bit more than it was ).

Did the job over a few days - because of the lazy workforce.

We flattened off / filled the underside of the bolt holes and sanded down (up?!) the deck underside - and then drilled new bolt holes through (made a cardboard pattern from the winch)......coated the deck underside with thickened epoxy and bolted on a thick piece of plywood.....to be honest the surface prep was not exactly perfect (access was a pig ) but figured that as the new backing pad was bolted on that this did not really matter - Epoxy really only a filler, not the primary bond.

When the epoxy was dry the bolts were removed (and the plywood backing plate stayed put )......we then added a plinth on deck to sit under the anchor winch (we used a solid hardwood, of some sort) - this also sat on a bed of epoxy.....and had the plus of hiding the oversized and now epoxy filled bolt holes.....the boat was a strange colour, so no chance of selves ever matching the existing gelcoat. The bolts were covered with mastic before getting inserted for the final time.

Although I won't claim the above is a textbook fix - am pretty sure that the entire foredeck will come off long before that winch ever does .

The above a bit of a long winded way of suggesting that I would start with doing something similar on all your deck fixings. I would also check your moisture readings by removing a decent panel of deck from the underside so that you can get hands on with the core itself and by removing it for close inspection....easy enough to put a chunk of new core back and then glass up the underside (on the underside no need to be neat ).

If your inspection panel is in the worst place (according to the meter) and the core is dry then you have your answer......I would also take photos so can show to a prospective buyer in future years if their Surveyor says same thing.

Personally, if the deck was not flexing or soft (i.e. the only way to tell is the meter) then once the deck fitting holes have been rebedded via epoxy filled bolt holes and water did not pour out of the inspection panel I would call it a day....and then monitor the situation closely on an ongoing basis with a view to actively considering whether or not to effect additional works .

...........and for all (?!) those shaking head and tutting - remember that I am not alone ....your PO may have been a blood brother of mine . But as I said, I bought the current boat because it had no core .

[Rhapsody-NS27]

If/when rebedding the deck hardware could be a good time to inpect the immediate areas around the holes to see the condition of the core. Could be a good starting point to see any indicators of the condition.

[44'cruisingcat]

Instead of using heat, how about applying vacuum?

[minaret]

Originally Posted by 44'cruisingcat

Instead of using heat, how about applying vacuum?

Or both at the same time, as I already suggested? I've done all of these techniques for drying core, none of them really work except the hotvac. The key to this science is the fact that the boiling point of water is much lower in a vacuum. The better the vac, the lower the boiling point. You can get water to vaporize at 170 F or less with a decent setup, and the vac pulls out the vaporized water as soon as it appears. Works great, takes lots of the right equipment and knowledge.

[unbusted67]

Man I tell you I just pulled the jib track off (which is the culprit for letting moisture in to begin with) and I have chewed out some of the coring and it is bone dry, I mean really bone dry! So strange.

The deck seems to be in good shape in terms of squishiness, and I can't really tell if there is de-lamination, but my meter, and more importantly, the meter of the surveyor who wouldn't write me a favorable survey (thus preventing me from getting proper insurance) say it is wet. I tell you I don't know what to make of it.

[unbusted67]

Originally Posted by minaret

Or both at the same time, as I already suggested? I've done all of these techniques for drying core, none of them really work except the hotvac. The key to this science is the fact that the boiling point of water is much lower in a vacuum. The better the vac, the lower the boiling point. You can get water to vaporize at 170 F or less with a decent setup, and the vac pulls out the vaporized water as soon as it appears. Works great, takes lots of the right equipment and knowledge.

So lay it on us. I, for one, am interested and captivated by this method.

I will say this, water does not need to be at its boiling point to evaporate.

[colemj]

Originally Posted by unbusted67

Man I tell you I just pulled the jib track off (which is the culprit for letting moisture in to begin with) and I have chewed out some of the coring and it is bone dry, I mean really bone dry! So strange.

The deck seems to be in good shape in terms of squishiness, and I can't really tell if there is de-lamination, but my meter, and more importantly, the meter of the surveyor who wouldn't write me a favorable survey (thus preventing me from getting proper insurance) say it is wet. I tell you I don't know what to make of it.

Then I would suspect the meter or the person using it. Sounds like you might be good to go in this area. How much more is suspect? If the core is very wet or rotten, anybody with some experience can tap it out with a phenolic hammer and tell where and how much. You can do it yourself if you have adjacent good core - the sound difference is noticeable.

Mark

Mark

[tamicatana]

I think this is worth repeating. The below reflects my experience with wet balsa (at the chainplate and daggerboard, in my case). It's not rocket surgery, honestly. It seems scary to cut into your boat but it's not that bad. Take your time, don't whale at it. I was able to find some core foam bits from a local boat fabrication house, it was extras and bits they had in their bins - they gave it me (thanks Glenn Young boats, OS, MS)

Originally Posted by colemj

If your core is wet, the first thing you should do is find out why and stop further water from coming in. If the core is not completely saturated and rotten (doesn't sound like it is), then I personally would just leave it alone after stopping further water ingress until it becomes either rotten or delaminated. You would be surprised at how well even wet rotten balsa stays laminated.

If your core is saturated or rotten and delaminated, then do yourself a big favor and cut off one skin, recore and reattach the skin. You would be surprised at how easy this procedure actually is. Even though it sounds like major surgery, it is much easier than all the other "tricks". And much stronger and longer lasting.

Mark

[44'cruisingcat]

Originally Posted by unbusted67

So lay it on us. I, for one, am interested and captivated by this method.

I will say this, water does not need to be at its boiling point to evaporate.

Basic science experiment. Put some water in a flask, attach it to a vacuum pump and watch.

The water inside the flask will start to boil, and at the same time it will GET COLDER. Eventually there will be boiling water inside the flask and ICE forming on the outside.

At near zero pressure water will boil hundreds of degrees below zero.

[minaret]

Originally Posted by unbusted67

Man I tell you I just pulled the jib track off (which is the culprit for letting moisture in to begin with) and I have chewed out some of the coring and it is bone dry, I mean really bone dry! So strange.

The deck seems to be in good shape in terms of squishiness, and I can't really tell if there is de-lamination, but my meter, and more importantly, the meter of the surveyor who wouldn't write me a favorable survey (thus preventing me from getting proper insurance) say it is wet. I tell you I don't know what to make of it.

Sheet lead tracks are a classic culprit. But if the core you are sampling is truly bone dry, blonde and pretty, it could be a case of cobalt accelerant giving high readings. Couldn't say without seeing the readings. Is there a clear demarcation point where the readings change? Are these clear demarcation points at points where the deck transitions from core to solid layup? If not can you get a high reading on an area of solid glass? If you can it's cobalt. Try to peel the outer skin off of a holesaw sample if you have one and get a reading on it. If it reads high you can show it to your surveyor and explain. Can you get a large core sample and deskin it and see what just the core reads? Isolate the problem. And make sure you really squeeze a piece to see if moisture comes out, like I already said sometimes core that looks great is really saturated. I wouldn't be surprised if many surveyors aren't aware of the issue of cobalt and other metallic accelerants, certainly I've seen ones that weren't aware of it before.

[minaret]

Originally Posted by unbusted67

So lay it on us. I, for one, am interested and captivated by this method.

I will say this, water does not need to be at its boiling point to evaporate.

http://www.cruisersforum.com/forums/...tem-58007.html


http://www.cruisersforum.com/forums/...cks-69464.html


Some other threads on Hotvac here.

[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.

[minaret]

Originally Posted by 44'cruisingcat

Basic science experiment. Put some water in a flask, attach it to a vacuum pump and watch.

The water inside the flask will start to boil, and at the same time it will GET COLDER. Eventually there will be boiling water inside the flask and ICE forming on the outside.

At near zero pressure water will boil hundreds of degrees below zero.

Exactly, but it is almost impossible to acheive anything like a perfect vacuum in working conditions. First off, the whole problem is that the material itself is porous, backed up by the fact that no construction technique is perfect. If it's not water tight it's certainly not air tight. We usually drill holes from the top and install hotvac pads over them. This means any fastener holes or voids in a corner of laminate on the inside skin will cause an air leak, preventing you from acheiving a vacuum. A big part of a good hotvac setup is proper gauging so you know when you are pulling enough vac to allow water to evaporate at the temperature which you are also gauging.

[sailorboy1]

The surveyor for my boat at first said my HULL was wet! When I pushed him to look closer because where he said it was "wet" the hull was solid fiberglass, it turned out all he had been reading was the change from where the pan was to the non-pan section.

The survey on my ast boat said the deck was wet at the bow. Once I started to "fix" it, I found that it wasn't wet at all.

Guy I have sailed with who has an old C&C-36 got it cheap because they said it had a wet deck. It didn't once deeper digging was done!

Don't jump to the conclusion that the deck is wet just because of the meter.

Before doing anything look for where any water could have gotten in and check that! Even if you have a wet deck you have to fix that first. And there is good chance that you don't find any problem.

That the loner down from inside the boat in the "wet" areas and poke at the coring. If it isn't soft the deck probaby isn't wet.

Get a meter and recheck the deck from the inside. Does it still measure as wet?