What do to with my damaged gelcoat hull

[stormalong]

Don't use just plain old epoxy to seal the bottom. Use a barrier coat designed to block moisture from migrating through the coating. I have used Interprotect 2000E very successfully. For a 7 meter boat this should not be too expensive.

After removing all loose material and grinding out any sticky or weeping wet spots give it another few weeks to dry. Then fill and fair with thickened epoxy. Then 5 coats of Interprotect per instructions from Interlux. Per their instructions use the recommended time interval between coats. Then apply antifouling paint again at the appropriate interval. This is a perminant fix that will last for decades.

My experience: In October, 1990 I purchased a boat with about 400 blisters between the gelcoat and the laminate. It had already had a West system repair that had failed. Without special additives and sufficient time for the hull to dry no barrier coat will work. I trucked this boat to a cold climate, opened and ground out all the blisters. Most were smaller than a U.S. dime. A few were as large as a quarter. I let is all air dry over the winter. In the spring the entire hull was sanded to remove remaining bottom paint, blisters were filled and faired. Five coats of Interprotect 2000 were applied. Seventeen years later a few blisters started forming. These were ground out, faired and another five coats of Interprotect were applied to the entire hull. It is now another fifteen years since the second coating. No new blisters have appeared. I still own the boat.

I realize that in the Canaries material availability would be more difficult. There must be a source for these materials from mainland Spain. If you plan to keep the boat for a long time it is worth doing the job right. For a 7 meter boat the material cost would be far less than my 13 meter sailboat.

[rognvald]

"a hull that thick should dry fairly quickly, 2 or 3 weeks would probably do it" Greg K

And, this advice is based on what, Greg?
Rognvald

[Greg K]

Originally Posted by rognvald

"a hull that thick should dry fairly quickly, 2 or 3 weeks would probably do it" Greg K

And, this advice is based on what, Greg?
Rognvald

Observation

[rognvald]

Originally Posted by Greg K

Observation

Hi, Greg,
With no disrespect intended, your time period for drying is bad advice. A 3 month outdoor drying period with weekly fresh water scrubbing to help release any contaminants in the substrata is a minimum baseline based on 35 years of boatyard protocol both in Illinois and Florida. Time can be accelerated in a sealed drying tent with humidifiers 24 hours a day but if the bottom is still chemically contaminated and wet, the bottom job will never last and you'll be doing it over again. The honest answer here is that there is no shortcut to this job. Do it right or do it again.
Rognvald

[Greg K]

Originally Posted by rognvald

Hi, Greg,
With no disrespect intended, your time period for drying is bad advice. A 3 month outdoor drying period with weekly fresh water scrubbing to help release any contaminants in the substrata is a minimum baseline based on 35 years of boatyard protocol both in Illinois and Florida. Time can be accelerated in a sealed drying tent with humidifiers 24 hours a day but if the bottom is still chemically contaminated and wet, the bottom job will never last and you'll be doing it over again. The honest answer here is that there is no shortcut to this job. Do it right or do it again.
Rognvald

To be clear, it's opinion not advice. And opinions are like azzholes: everybody has one. Especially on the internet.

[canaryo]

So just a quick update on the boat:


Humidity of the hull dropped from around 28% to around 18% within 4 weeks.


I will definitely let it dry another 4 weeks and aim for 10% on all spots before doing the epoxy job.

[Greg K]

Originally Posted by canaryo

So just a quick update on the boat:


Humidity of the hull dropped from around 28% to around 18% within 4 weeks.


I will definitely let it dry another 4 weeks and aim for 10% on all spots before doing the epoxy job.

What readings are you getting on the topsides above the waterline? Those would be your datum level you should be aiming for.

[s/v Jedi]

Wash it with a pressure washer. Don’t worry about it getting wet, it will actually speed up the drying process.

Also, before filling those spots I would consider painting them with a brushed coat of Hullguard from Awlgrip, which is made for sealing raw fiberglass and brush application.

Any epoxy filler will work; I would use TotalFair but I don’t know if it’s available where you are.

[rognvald]

Originally Posted by s/v Jedi

Wash it with a pressure washer. Don’t worry about it getting wet, it will actually speed up the drying process.

Also, before filling those spots I would consider painting them with a brushed coat of Hullguard from Awlgrip, which is made for sealing raw fiberglass and brush application.

Any epoxy filler will work; I would use TotalFair but I don’t know if it’s available where you are.

Good advice, Jedi,
However, an option to Hullguard: wet out with West System Epoxy and fill with West Lo Density Filler(thickened epoxy)slightly above level to allow for shrinkage when curing(one step). Good luck canaryo. If you do it right, you'll never have to do it again.
Rognvald

[boatpoker]

Your boat appears to be suffering from hydrolysis. Polyester resins are ... believe it or not hygroscopic and can dissolve in extreme cases. I have a little bit about the issue on my website ... Osmosis testing in boats

[rognvald]

Originally Posted by boatpoker

Your boat appears to be suffering from hydrolysis. Polyester resins are ... believe it or not hygroscopic and can dissolve in extreme cases. I have a little bit about the issue on my website ... Osmosis testing in boats

Well-written article, Boatpoker!
Rognvald