Successful Osmosis Repair

[Olddave]

Hi all,
I have launched into repairing the blisters on my '87 Swarbrick S&S34 and would like to hear from anyone who has knowledge of similar repairs that have withstood the test of time!

I have a lot of blisters but no delamination. The boat has clear gel coat and has been coated with epoxy paint. We drilled all the bubbles with a countersink drill bit and then sanded all paint off the bottom. The blisters are about 5mm. Typically they have white glass fibres that spread out around the blister to some extent. Certainly not bad osmosis but needs fixing. Sanding the hull revealed pin prick size holes in the resin that I presume would be from the Styrene escaping as the resin set during construction of the hull.
There seems to be many boats having repairs that are unsatisfactory. My research to date suggests that the acids created by the breakdown of polyester resin may be causing problems with the epoxy resins used in the repair.
It has been suggested to me that Vinylester resin lasts better in contact with the old polyester. I would love to here about any good experiences people have had with repairs. All my previous experience is with Epoxy resin as I have built a trimaran some years ago.
Thanks in advance for your stories.
Dave

[Cheechako]

Sometimes it depends on how invasive and how many blisters there are. Loaded? Probably best to peel and resurface the bottom. But that's a big job, and an old boat may be best served by digging them out, letting them dry, fill, sand and coat with epoxy.

[Olddave]

Originally Posted by Cheechako

Sometimes it depends on how invasive and how many blisters there are. Loaded? Probably best to peel and resurface the bottom. But that's a big job, and an old boat may be best served by digging them out, letting them dry, fill, sand and coat with epoxy.

Hi Cheechako,
I will probably re-glass the whole bottom even though the port side is pretty good.
My main concern is finding a resin that will stay stuck to old polyester.
Dave

[bletso]

We shaved the bottom gel coat off Vigah using Marine Paint Removal | Marineshaverâ„¢ Pro Paintshaver.com | Paint Removal Tools | PaintShaver.com Amazing tool. With a shop vac sucking up the debris we had no environmental contamination. We then faired the bottom with A high tech aerospace epoxy made by Magnolia. Then we put six coats West 105/206 with barrier coat additive.

[minaret]

It's unfortunate when people begin to educate themselves on a complicated process like this after having already dove in. Can't peel it now that it's been ground. Best bet is blast it bare, dry it out, and start the process of repair. Spot repair is guaranteed to fail, as it doesn't address the cause of the problem.

[Crealock37]

This won't help with the repair, but for anyone who plans to buy a boat and wants to avoid this, you might go for a Pacific Seacraft. No blisters on these boats ever because they use vinylester resin (if that's the right term for the stuff). The reason it's not used universally is the usual reason: it costs more.

Crealock37
--
Pacific Seacraft 37 f o r s a l e in Hong Kong.
Information here: pacificseacraft37 . com

[Olddave]

Originally Posted by bletso

We shaved the bottom gel coat off Vigah using Marine Paint Removal | Marineshaverâ„¢ Pro Paintshaver.com | Paint Removal Tools | PaintShaver.com Amazing tool. With a shop vac sucking up the debris we had no environmental contamination. We then faired the bottom with A high tech aerospace epoxy made by Magnolia. Then we put six coats West 105/206 with barrier coat additive.

Thanks Bletso
That's the sort of feedback I was looking for. How long ago did you do it? I built my previous boat exclusively with West System products and have great respect for them. I was planning to use them for this project, however, some very knowledgable friends have been having success with Vinylester resin. I am interested to see what other people are using.
Dave

[Olddave]

Originally Posted by minaret

It's unfortunate when people begin to educate themselves on a complicated process like this after having already dove in. Can't peel it now that it's been ground. Best bet is blast it bare, dry it out, and start the process of repair. Spot repair is guaranteed to fail, as it doesn't address the cause of the problem.

Hi Minaret
Thanks for the reply. I am not really just beginning to educate myself with these repairs. I have been around boats and boat building all my life. I just got some advice from a respected friend who has supervised many osmosis repairs. He has been using vinyl ester resin with more success than epoxy, so I am putting the question out there to see what others have had success with.

[bletso]

It was in 95 and to be honest Vigah has been on the hard most of the time since. I am finishing up a refit and should get her back in the water this year. In theory Vinylester resin should be the resin of choice due to it be more impervious to water absorption but I don't know its compatibility to either epoxy or polyester resins. Good luck with your project

[HappyMdRSailor]

Originally Posted by bletso

We shaved the bottom gel coat off Vigah using Marine Paint Removal | Marineshaverâ„¢ Pro Paintshaver.com | Paint Removal Tools | PaintShaver.com Amazing tool. With a shop vac sucking up the debris we had no environmental contamination. We then faired the bottom with A high tech aerospace epoxy made by Magnolia. Then we put six coats West 105/206 with barrier coat additive.

Originally Posted by Olddave

Thanks Bletso
That's the sort of feedback I was looking for. How long ago did you do it? I built my previous boat exclusively with West System products and have great respect for them. I was planning to use them for this project, however, some very knowledgable friends have been having success with Vinylester resin. I am interested to see what other people are using.
Dave

Originally Posted by minaret

It's unfortunate when people begin to educate themselves on a complicated process like this after having already dove in. Can't peel it now that it's been ground. Best bet is blast it bare, dry it out, and start the process of repair. Spot repair is guaranteed to fail, as it doesn't address the cause of the problem.

Originally Posted by Olddave

Hi Minaret
Thanks for the reply. I am not really just beginning to educate myself with these repairs. I have been around boats and boat building all my life. I just got some advice from a respected friend who has supervised many osmosis repairs. He has been using vinyl ester resin with more success than epoxy, so I am putting the question out there to see what others have had success with.

Olddave...

UNFORTUNATELY... I have a few experiences with blister repair, one severe... In that case I went with the good old grind out until all laminate damage was gone... x1000... Then cabo/epoxy fill + glass for a few...

Fortunately I have far LESS experience than minaret... who has more knowledge about this in his big toe than the total sum of CF posters combined... His advice should be carefully considered...

[Olddave]

Hi Happy MdR Sailor,
Thanks for the tip, Much appreciated. Minaret's comment that a spot repair is guaranteed to fail makes sense. It is my intension to do a complete treatment, and prepare the boat for another 30 years in the water. Today the hull was checked with a moisture meter and found to be pretty much bone dry except for some water in the rudder skeg. When I finish sanding, I will probably seal the original polyester/glass with vinylester resin and csm, followed by several layers of epoxy resin and paint. Its a beautiful boat and well worth the effort involved in keeping water away from the polyester.
Thanks for your advice, Dave

[El Pinguino]

My boat had a full peel and then vinyl ester and three layers of glass.... job done by Brin Wilson/Osmosis Solutions NZ.

Owner of the boat in the last photo baulked at the price of a proper job and paid $NZ15k for this....

[Olddave]

Hi El Pinguino,
Very good to hear that Brin Wilson is using vinylester. I have had two very experienced osmosis repairers look at the boat today and both were impressed by the condition of the hull. At this stage I am planning to coat the hull with glass and vinylester followed by epoxy resin/paint. Thanks for your help.
Dave

[minaret]

Originally Posted by Olddave

Hi Minaret
Thanks for the reply. I am not really just beginning to educate myself with these repairs. I have been around boats and boat building all my life. I just got some advice from a respected friend who has supervised many osmosis repairs. He has been using vinyl ester resin with more success than epoxy, so I am putting the question out there to see what others have had success with.

I've done lots of both. I prefer an epoxy bottom, for numerous reasons. Not that vinylester doesn't work, it does. It's just more time consuming and expensive.

The issue I was trying to bring up was blister removal/peeling. One of the key causes of osmosis and blistering is the chopper gun skin they sprayed in the mold for most boats. This surface laminate is generally porous, full of voids, and was sprayed from an external mix chopper gun, therefore full of incompletely mixed catalyst and resin as well. Best bet for full cure of an osmosis boat is to remove this layer completely, down to good solid glass. This requires a peeler, as any other method will cause a fairing nightmare. Especially blasting. However, a peeler is no longer an option, as the blisters have been ground out and there is no longer a fair surface for the peeler guide to run on. This has created a great deal more work to do this job correctly. It's much faster and easier to remove all bad glass and then apply a couple layers to the whole bottom to replace it than it is to glass hundreds of spot repairs all over the bottom. If you grind out blisters and just fill them, with any filler, it's sure to fail at some point.

[Olddave]

Originally Posted by minaret

I've done lots of both. I prefer an epoxy bottom, for numerous reasons. Not that vinylester doesn't work, it does. It's just more time consuming and expensive.

The issue I was trying to bring up was blister removal/peeling. One of the key causes of osmosis and blistering is the chopper gun skin they sprayed in the mold for most boats. This surface laminate is generally porous, full of voids, and was sprayed from an external mix chopper gun, therefore full of incompletely mixed catalyst and resin as well. Best bet for full cure of an osmosis boat is to remove this layer completely, down to good solid glass. This requires a peeler, as any other method will cause a fairing nightmare. Especially blasting. However, a peeler is no longer an option, as the blisters have been ground out and there is no longer a fair surface for the peeler guide to run on. This has created a great deal more work to do this job correctly. It's much faster and easier to remove all bad glass and then apply a couple layers to the whole bottom to replace it than it is to glass hundreds of spot repairs all over the bottom. If you grind out blisters and just fill them, with any filler, it's sure to fail at some point.

Minaret, yes I would have been better off with a peeler, the Festo orbital and vac is doing the job, slowly. The Swarbrick S&S34's didn't get the chopper gun treatment. They used CSM and I can see the overlaps, in fact that is where some of the small voids are hiding, I guess from a lack of rolling when laid up. My hull is in very good condition for its age. I like epoxy too,however, I will probably glass it with vinyl ester then paint with epoxy.
Thanks for your input, it is valued.
Dave