The Science of Soggy Decks

[unbusted67]

We bought our boat very cheap because the surveyor found moisture in a couple of large swaths in the deck. We are committed to getting it fixed even if it means cutting out sections and replacing them...but I would like to try the cheap and easy way first and try to dry out sections using a heater.

We have very good under deck access to the affected areas and I have been thinking of drilling a few pilot holes to let the moisture out and just slamming it with heat to see if I can get the readings on the meter down. My thought is that if the moisture found its way in there it can probably find it's way out through evaporation.

I would love to hear from anyone who has successfully dried a section of cored deck with just a heater. I would also love to hear from anyone who has been unsuccessful.



On a bit of a side note, I am wondering about the structural integrity of these sections. They are not showing any signs of a moist deck. No thud when you tap it, no squishiness under foot, and when we drilled out a pilot hole with the a hole saw we found the core (I think it is balsa) to be dry to the touch. Still the meter doesn't like it.

[GordMay]

Try another meter & operator.
It takes a lot of skill to properly interpret moisture meter readings.

See:
➥ http://www.northcoveassociates.com/meter.html
➥ http://www.marinesurveyor.com/meters.html
➥ http://www.pcmarinesurveys.com/moist...0mythology.htm

[Sailmonkey]

I wouldn't worry about the decks unless they're actually soft.............Moisture meters are a sort of blackened voodoo magic. When properly observed they give good information, otherwise they always tell you something is wet somewhere!!

[keepondancin]

Go to the WEST Epoxy web site and download their manuals. Good place to start for deck repair.

[unbusted67]

Originally Posted by GordMay

Try another meter & operator.
It takes a lot of skill to properly interpret moisture meter readings.

Sorry Gord I am a little confused are you saying that maybe I misinterpreted the meter reading and that the decks are not moist? I am just going off of what our surveyor told us, and what my meter is telling me seems to agree with him.

[unbusted67]

Originally Posted by Sailmonkey

I wouldn't worry about the decks unless they're actually soft.............Moisture meters are a sort of blackened voodoo magic. When properly observed they give good information, otherwise they always tell you something is wet somewhere!!

Whoever came up with the idea of cored decks is bonkers any way! "Let's put something soft and susceptible to moisture between two sheets of a material that will crack and let moisture in and make it impossible to inspect of fix" Duh.

[capn_billl]

Originally Posted by unbusted67

Sorry Gord I am a little confused are you saying that maybe I misinterpreted the meter reading and that the decks are not moist? I am just going off of what our surveyor told us, and what my meter is telling me seems to agree with him.

Not to knock your technical skills, or even the meters calibration, but Gord may have a point.

There are several possibilities that I would pursue before ripping out what may be perfectly good decking.

1. Atmosperic conditions can give misleading moisture readings
2. Moisture in the gel coat, (what might have become blisters if under waterline)
3. Recent water intrusion that hasn't caused rot yet, (if the balsa you core drilled was dry this is the least likely).
4. Higher that normal humidity inside cabin throwing off meter. (IE condensation in headliner)

If this is a survey on a boat your buying it is a valid warning sign, but if you already own the boat, you may be borrowing trouble from the future to do anything too drastic.

I would start by like you said let everything dry out a much as possible, then rebed deck hardware, (a job that needs done periodically anyway).

I would do this on a hot dry day, (or if on the hard in a heated dehumidified enviroment), to reduce as much as possible trapped moisture. Good luck

[minaret]

Originally Posted by unbusted67

We bought our boat very cheap because the surveyor found moisture in a couple of large swaths in the deck. We are committed to getting it fixed even if it means cutting out sections and replacing them...but I would like to try the cheap and easy way first and try to dry out sections using a heater.

We have very good under deck access to the affected areas and I have been thinking of drilling a few pilot holes to let the moisture out and just slamming it with heat to see if I can get the readings on the meter down. My thought is that if the moisture found its way in there it can probably find it's way out through evaporation.

I would love to hear from anyone who has successfully dried a section of cored deck with just a heater. I would also love to hear from anyone who has been unsuccessful.



On a bit of a side note, I am wondering about the structural integrity of these sections. They are not showing any signs of a moist deck. No thud when you tap it, no squishiness under foot, and when we drilled out a pilot hole with the a hole saw we found the core (I think it is balsa) to be dry to the touch. Still the meter doesn't like it.

Properly reading a moisture meter is not such a black art as some would have you believe. There are a few simple facts that once understood help you to understand what you are seeing. Some pics of your readings "mapped out" would help. But the key thing to remember is that any metals will cause the meter to read saturated. So tanks, wiring, and any other metal content touching the inside of the surface you are reading on are a common cause of false high readings. These are easy to spot, as the edges are sharply delineated, ie it reads dry and then suddenly very wet in an area that has clearly defined edges. More difficult false readings include the common use of cobalt and other accelerators in some manufacterers resins. Cobalt poly resin accelerator will give false high readings every time, but how high depends on how much accelerator was used. This can be hard to spot, particularly if what you are seeing is a repair that was accelerated. That can lead to a false reading that looks very much like the real thing, ie high readings in the middle tapering off at the edges. And then we also have core that is just damp, resulting in a moderate reading on the meter, but it looks dry and blonde when you sample it. Get a good sized chunk out of a sample and squeeze it hard between thumb and finger. Do you detect any moisture being squeezed out? You'd be surprised at how nice damp balsa core can look. This will rot eventually, it just hasn't had time yet. Find the source of water entry and reapair, as well as recoring.
As far as drying core in place, it isn't really possible without serious equipment. I have dried cores several times with the use of a Hotvac; even then it's a load of work. It's only really worth doing on a foam core, IMHO. If that is an avenue you wish to pursue, ask questions and I'll tell you how to make a sort of homemade hotvac, but it's not cheap equipment even in the homemade version. For a one time use it's probably better to repair it the old fashioned way.

[MacG]

Very good Minaret

Quite often - when balsa cores are real wet - the bond is destroyed as well and therefore a good part of the strength of the sandwich construction.

I was checking some time ago on an Ohlson 38 when the surveyor who did the survey for the Broker (one of the 'rare' honest) warned me for a suspicious place. It turned out that the deck was balsa-cored and around all fittings the balsa was buttersoft.
I let this boat go.
The next Ohlson I was looking for had an identical problem and this time I was warned. I let this boat go too.
Point is that such repairs are difficult to carry out and have to be done in a closed site. Evenb if you dry it that will not say that the structural bond between the layers is still intact.
Keep in mind that all ortho-and Iso resins are not impermeable, they let water through by way of osmosis. This will take a very long time because it is a very slow process that will show its occurrence after some 20 years or more.

[rtbates]

Moisture readings aside, what do the decks feel like in those areas??

You may just end up drying the core out real good only to fall through a dry deck..

[MacG]

One word: flexible.

[Ocean Girl]

I did a 40 ft trawler, she had some pretty wet core. It looked like a type of plywood, so the worst stuff you can work on. What I did, and worked well for 90% of the soft areas, so not perfect but the better than replacing her core.

Drilled holes topside in a grid pattern, the grid changed as the soft core became apparent. So a drill hole every foot in dry areas and holes closer and closer as the core came up wet/soft. I did the entire boats deck, including flybridge.

I used a drill bit size that the syringe used for injecting epoxy tip would easily set into. I only drilled a few strategic hole down below, in areas that were the "wettest" and also that as I doused with epoxy I could keep track of what was dripping into the boat.

I then tented sections of the deck ( topside) and placed a dehumidifier inside this tent. the dehumidifier was the key the drying out the core. I also doused the area with denatured alcohol. I had a second dehumidifier going 24/7 down below.

After I got the core good and dry, I doused the area with denatured alcohol again and started pumping penetrating epoxy into the holes. I set the syringes in the drill holes after removing the plungers, I then ran a piece of tape around the base to keep it in place and then just used a 60 cc syringe to fill the 20 cc that were taped to the deck. It was slow back breaking work but only took two full days to get the deck good and solid.

Be careful!! Check down below regularly to make sure you are not dripping epoxy into your interior.

I saturated till the deck wouldn't absorb anymore. When cured, I filled the little dimples that remained of the holes. Sanded the deck. Painted the deck with topside paint and those great rubber grip nonskid beads.

It came out really well. I used Smiths penetrating epoxy, but maybe look into the epoxies that will cure in wet wood for the really bad problem areas( non structural ). My problem areas were in the middle of the boat because of her sheer. In hindsight I should of started in the middle and worked my way up, so the epoxy could work as a dam for the next batch up stream ( hope that made sense.

Here is amore coherent and detailed article, though they remove their topside.
Repacing Rotten Deck Core, Part I | Sail Feed



Hope that helps
Mrs. Rain Dog

[bazzer]

Some boats are easier to repair wet cores than others, Duh! But a google search will provide a lot of information as to how to go about it. Yes, West Epoxy has information on their site and is probably the way to go. Some boats are very prone to saturated deck cores, Hans Christians being one of them. Maine Sail also has information on wet core replacement. If the boat is the right price and you are handy with tools and glassing then don't let a high moisture reading put you off.

[GordMay]

Originally Posted by unbusted67

... They are not showing any signs of a moist deck. No thud when you tap it, no squishiness under foot, and when we drilled out a pilot hole with the a hole saw we found the core (I think it is balsa) to be dry to the touch. Still the meter doesn't like it.

Yes, given the direct evidence (no moisture detected), I am suggesting that the meter readings may have been misinterpreted.

[hellosailor]

As MacG said. Don't even try heating the boat (close cabin, add heaters, try not to set it on fire, wait a month...) until you've accessed the deck coring to see if it is still good or has become mushy or started to fail. If you can't access it by removing hardware, you'll need to drill some small holes and see what comes up.

AFAIK no one recommends just heating the boat up to drive out the moisture, all the usual suspects suggest drilling holes in a checkboard pattern, etc. to let the moisture out. Or adding solvents to try carrying it out. And unless you're very lucky--it has still degraded if there has been enough time to get extensive spreading.

In the long run it may be cheaper, faster, more reliable to cut large sections of the deck skin (from above) replace the coring, replace the skin, then cover the work with new anti-skid materials to hide the scars. Bonus, you get a nice anti-skid deck finish.