Copper coating old GRP hull?

[STOL71]

- Long keel GRP boat with encapsulated led keel built in 1971
- Boat in good nick and planning to continue sailing the boat
- All antifoul paint removed down to the original gelcoat
- On close inspection when gliding with fingers over the hull, I detected osmosis blistering under the gelcoat
- Ground out approx 100 blisters half inch to an inch in size in October 2016
- Been pressure washing blisters since at least weekly
- Planning to fill ground out blisters and copper coat the hull in late March or mid April 2017
- Moisture reading under the water line in Feb 2017 mostly 10 - 15% or less
- Moisture reading in some parts around the keel area 15 - 25%
- Not expecting the boat to dry much further unless I remove the gel coat, which is not the plan
- Not adding additional epoxy barrier coat before applying copper coat to allow further drying when ashore
- Planning on monitoring the hull when lifting out in the future
Does anyone have experience with the above and what was the long term outcome?
Thank you for your input.

 

[PlankWalker]

Once you have found osmotic blisters, the chances of you finding a few more next year and the year after are prety high. Keeping on top of the problem by grinding them out drying and filling as you find them is no big deal, but copper coat is an expensive opperation even if DIY.
I would hate to have to grind through CC and make good every time I found a blister.

Plank

 

[Deleted member 36384]

There is an opinion that using an epoxy over an old hull that has osmosis will accelerate the appearance of blisters. I'll post a link later to the book where this is stated.

I have a 1973 built / 74 launched Rival and because of this book and elevated moisture readings I decided against copper coat. I would hate to go to all that trouble and expense just to see the treatment blister.

Spend the money on something else if you want my advise.

 

[jwilson]

How were the moisture readings taken - what meter and what scale. On some meters and scales 25 can mean pretty low, on others very high. Also how did they compare to readings taken on the hull well above the waterline?

 

[Rivers & creeks]

There is an opinion that using an epoxy over an old hull that has osmosis will accelerate the appearance of blisters. I'll post a link later to the book where this is stated.

I have a 1973 built / 74 launched Rival and because of this book and elevated moisture readings I decided against copper coat. I would hate to go to all that trouble and expense just to see the treatment blister.

Spend the money on something else if you want my advise.

Two yards I've been in said they won't epoxy coat old hulls because they've had too many then develop visible osmosis soon afterwards. CC even without an epoxy coat when you know you've got more blisters to come seems odd???

 

[Halo]

What do Coppercoat say ?
If it were me I would put several layers of epoxy on in alternating colours (e g grey and white). Then it's a decision whether to Coppercoat or Antifoul.
If the blistering does not return then Coppercoat may have been a sensible option. I can see why yards won't risk it. But it's your call if you are doing the job. You will need a spell of reasonably warm dry weather for each treatment and need to prepare the surface properly for Coppercoat.

 

[Daydream believer]

Just put the coppercoat on. Osmosis will not sink the boat. Coppercoat will act as an additional gel coat, which is only a cosmetic coating anyway, according to the coppercoat company when i asked.
Doing it yourself is just the cost of the material & when i did it on a 31 ft fin keel that cost about £ 650-00 plus rollers etc & included primer for the keel. If you have all the old paint off then you are most of the way there but the surface must be very clean ( looking like a sheet of A4 paper) Half of the cost is getting the old stuff off & yard costs etc
Considering I was applying 2 coats of antifoul paint every year at £190-00 a pop coppercoat is not so dear- except it does not work very well & i always need a mid season jet wash as well as end of season layup & wash

 

[STOL71]

The hull is dry above the water line.
Cannot remember make of moisture meter, will check when back at the boat.

How were the moisture readings taken - what meter and what scale. On some meters and scales 25 can mean pretty low, on others very high. Also how did they compare to readings taken on the hull well above the waterline?

 

[STOL71]

That was the rationale: the old layers of anti foul and primers are off anyway, might as well copper coat as this will safe me the annual anti foul. I don't expect visible blisters to develop for another couple of years and then I was planning to grind them out and patch up the copper coating.
I did read that the copper coat has to be abraded before first launch and then once in a while for it to work.

Just put the coppercoat on. Osmosis will not sink the boat. Coppercoat will act as an additional gel coat, which is only a cosmetic coating anyway, according to the coppercoat company when i asked.
Doing it yourself is just the cost of the material & when i did it on a 31 ft fin keel that cost about £ 650-00 plus rollers etc & included primer for the keel. If you have all the old paint off then you are most of the way there but the surface must be very clean ( looking like a sheet of A4 paper) Half of the cost is getting the old stuff off & yard costs etc
Considering I was applying 2 coats of antifoul paint every year at £190-00 a pop coppercoat is not so dear- except it does not work very well & i always need a mid season jet wash as well as end of season layup & wash

 

[STOL71]

I also happen to read that epoxying a wet hull only makes the situation worse as the boat wont dry out when laid up ashore, hence I wasn't planning on epoxy coating before copper coating. Copper coat is also epoxy based but more permeable than a traditional epoxy coating (gel shield).

There is an opinion that using an epoxy over an old hull that has osmosis will accelerate the appearance of blisters. I'll post a link later to the book where this is stated.

I have a 1973 built / 74 launched Rival and because of this book and elevated moisture readings I decided against copper coat. I would hate to go to all that trouble and expense just to see the treatment blister.

Spend the money on something else if you want my advise.

 

[STOL71]

Yes, I agree. but as I have stripped off all old anti foul and primer, I thought copper coating might be a good idea. Further blisters I'll grind out and then just simply patch up the copper coat.

Once you have found osmotic blisters, the chances of you finding a few more next year and the year after are prety high. Keeping on top of the problem by grinding them out drying and filling as you find them is no big deal, but copper coat is an expensive opperation even if DIY.
I would hate to have to grind through CC and make good every time I found a blister.

Plank

 

[Deleted member 36384]

It's not about Osmosis sinking the yacht it's about applying a coating that has an increase probability of being damaged from an osmotic hull. It's a crazy idea in my opinion.

 

[Deleted member 36384]

Before you make the decision, read the link when I post it. On my way home, so will post this morning the link.

 

[PCUK]

Have you considered other makes of Copper antifouling? I was thinking of using Synergie as an alternative but would be interested in your thoughts.

 

[STOL71]

I haven't considered other makes, because copper coating seems to be tried and tested.

Have you considered other makes of Copper antifouling? I was thinking of using Synergie as an alternative but would be interested in your thoughts.

 

[Puggy]

I really would not advise putting what is essentially an expensive epoxy coat over a hull that might need ongoing attention. It will blister and be an expensive mistake. Personally I had a bad experience with Coppercoat and ended up removing it all, so my view is somewhat skewed. Do look at Synergie if you really want to go that way. Next generation system and you get to speak to the people who are actually formulating and applying it. I was very impressed but choose to go with conventional antifoul whilst things settled down and I could decide at leisure.

P

 

[Deleted member 36384]

Before you make the decision, read the link when I post it. On my way home, so will post this morning the link.

This is the link to the book, Osmosis Myth and Reality About Hydrolyse Blistering and Delamination in FRP Boat Hulls, Bengt Blomberg.

http://www.osmosisinfo.com/handb9a.pdf
http://www.osmosisinfo.com/index2.html

The second link is the website with the download link and the option to buy a CD of the book and a statement that the book can be down loaded for free.

If you do nothing else read the first few pages and the chapter entitled 'Important results in short', Page VII. In my own internet based research, as an amateur, I thought that this book was worth taking at face value and it formed the basis of my decision not too copper coat or apply any other barrier.

Maybe your case and conditions are sufficiently different from my own. Food for thought at least.

 

[STOL71]

Thanks for the link, will have a look at it.

 

[STOL71]

Thanks for your message.
May I ask why painting epoxy in alternating colours?

What do Coppercoat say ?
If it were me I would put several layers of epoxy on in alternating colours (e g grey and white). Then it's a decision whether to Coppercoat or Antifoul.
If the blistering does not return then Coppercoat may have been a sensible option. I can see why yards won't risk it. But it's your call if you are doing the job. You will need a spell of reasonably warm dry weather for each treatment and need to prepare the surface properly for Coppercoat.

 

[Quandary]

Thanks for your message.
May I ask why painting epoxy in alternating colours?

Normal procedure, makers like Awlgrip offer two shades, it just makes it so much easier to see what you are doing when you intend applying multiple coats.