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Old 06-10-2011, 21:20   #1
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Blistering / Delamination on Decks

Hello,

A little back story...

We're on a 1985 Hans Christian 41, and we are currently in the process of redoing our decks. The boat originally had teak decks that were removed by the previous owner around 5 years ago and were replaced with Plasteak decking. When we bought the boat, the glue holding the Plasteak down had failed after less than 5 years. We decided to remove the failed Plasteak and go with nonskid. After removing the Plasteak and cleaning up the decks, we discovered some interesting issues:

1) The deck is not cored (a real plus in our minds as we were expecting potential issues with our core). The decks are 1/2" solid fiberglass, I know this as I have drilled holes in several areas of our decks specifically searching for core

2) Though the deck is not cored, we are finding high moisture meter readings, after 4 months of them baking in the hot sun.

3) The gel coat is severely crazed and mostly failed, flaking off, very easily

4) Large blisters have formed between the chopped strand mat and the woven glass. The entire layer of chopped strand mat in the areas where the original teak decking used to be, peel up very easily. As you move out along the edge, where the teak decking ended, the chopped strand mat is very strongly adhered. Some of these blisters even appear to contain osmotic fluid (very sour/vinegary smell, with a sticky, resinous quality). The areas of crazing in the gel coat correspond directly to the location of the failed seams of the original teak decking as you can see the crazing follows the same pattern as the original teak planking. As well, when removing the chopped strand mat, there appeared to be delamination that also corresponds to these same seams as there is obvious discoloration and lack of adhesion/long thin blisters that run in the same pattern.

From these observations, it is pretty clear that the seams of the original teak decking were neglected, and water became trapped along the failed seams for many years. This is what we are assuming to be the cause of all of this.
We have never seen anything like this on any forums related to the decks, we have only read about this happening on the underwater portion of the hulls. Being as the decks are not cored, our main concern is not the structural integrity, but rather wasting our efforta in repainting and non-skidding. I strongly believe, after what I have seen, that the reason that the glue for the Plasteak failed is due to the high moisture content of the fiberglass itself (Upon removal of the Plasteak, the glue seemed to have adhered strongest in areas where the decks had the lowest moisture readings). I don't want to spend tons of money and my time on a new barrier coat, non skid paint, and fairing material only to have it fail within a year or two due to a lack of proper prep work.

If anyone out there has had any experience dealing with this, please advise. Currently, we have most of the gel coat and the top layer of the chopped strand mat removed to try to speed up the drying process however the moisture meter readings seem to be decreasing very, very slowly (if at all).

I have attached some photos to help illustrate our conundrum, if anyone has seen this problem before and disagrees with our logic, please let us know as we are a little baffled, frustrated , and confused as to what the heck is wrong with our beloved old lady. Thanks in advance for you time.
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Old 06-10-2011, 22:41   #2
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Re: Blistering/Delamination on Decks

I've seen this before when peeling up old teak decks. Definitely trapped moisture causing osmotic blistering and delamination. How high are your moisture meter readings? I would peel or grind off all the gelcoat, make sure all delamination is ground out, and then dry it with the hotvac before relaminating and recoating. If you are going with nonskid instead of a new teak deck you shouldn't worry about barrier coating it. Find a yard with a hotvac setup and they'll dry it completely in a week.
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Old 06-10-2011, 23:39   #3
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Re: Blistering / Delamination on Decks

Welcome to the forum HansSolo.
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Old 07-10-2011, 06:18   #4
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Re: Blistering / Delamination on Decks

Greetings and welcome aboard the CF, HansSolo.
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Old 07-10-2011, 08:41   #5
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Re: Blistering / Delamination on Decks

Hello all!

Pleasure to be here. I've been reading a lot of posts on here and have found a lot of them to be really helpful. This is the first time I'm posting (and I don't think it will be my last), thank you all for the welcome.

Minaret--so you have seen this condition before? That's a relief because I was starting to think that my boat was a freak! Do you know of any other methods people have used to address this problem? I ask because I don't know of any places here that have a HotVac setup. I'm still doing the research for a yard that may have this here in Florida, but in the meantime, trying to find alternative solutions to dry out my decks.
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Old 07-10-2011, 08:50   #6
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Re: Blistering / Delamination on Decks

hanssolo--your boat is not a freak--is a leaky teaky. i have a formosa-- the decks were removed long time before i bought her. something about leaking decks.
you may want to share your findings with the leaky teaky yacht club group in yahoo groups. is an interesting situation and more folks seem to be finding it. doesnt make your boat any less good--is just another repair.....

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Old 07-10-2011, 09:00   #7
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Re: Blistering / Delamination on Decks

Nothing really wrong with your deck, i see a worst a scenenario time ago with a Formosa.
The repair procedure is not so diferent as fixing a osmotic bottom , sand, grind out gelcoat, probably grind out deep blisters and let dry for some time.

I dont know how is your inside liners configuration and if there is gelcoat or any kind of topcoat or whatever hiden the fiberglass inside, drying from inside and regular washing outside help .

I suspect the cabin top is ok, is just both sides??

If the first layer of mat is peeling off, better to keep peeling off until you find solid glass, if the deck is solid , and you dont find spongy spots, fine, if not maybe reglasing the whole deck .

After is the shity work of sand, epoxy, fairing, priming, painting or if you want to go original use polyester and regelcoat the whole deck .


Just a couple of tips, washing the deck with water presure and shoap help, when dry you can use some acetone and a rag to disperse moisture plus the heater from inside.
Cheers.
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Old 07-10-2011, 10:47   #8
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Re: Blistering / Delamination on Decks

Looking at your pics I see moisture readings of 25-30%. Thats really high, very saturated laminate. Once you pull all the hardware and grind off all the gelcoat, you'll be able to see better what's going on with the laminate (especially when you acetone wipe it). It'll be easier to find all the delam then.
If you can't find a hotvac setup, there are ways to make a sort of home version if you have access to a vacuum pump of any quality. The earliest versions of hotvac involved vacuum bagging an electric blanket to the saturated laminate. The science that makes it work is simple. In a vacuum, the boiling point of water is dramatically reduced. The better the vacuum, the lower the boiling point. A decent bag will bring the BP down to about 150-160F, a temperature it is easy and safe to acheive on laminate. Usually hotvac runs at 175F. So not only is the vacuum sucking moisture out of the laminate, it is also causing it to be vaporized and sucked out through the vacuum tube. A shopvac bag probably won't work for this because it will need to run for days at a time.
Failing that, grind it all out so theres no gelcoat or delam to inhibit drying, saturate it with acetone, and heat it well from beneath while keeping it dry and clean outside. It could take awhile. Good luck!
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Old 07-10-2011, 11:43   #9
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Re: Blistering / Delamination on Decks

HansSolo,

My problems were the same as yours.
My solutions were as Minaret describes.
No problems in 14 yrs.
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