Blisters! Is it Osmosis?

[David_Old_Jersey]

Originally Posted by sepeteus

Good news Nick! I am certainly glad to get some closure for this story. As we all know who followed this thred, there was some experts who jumped into conclusions with not much knowledge or far too much knowledge. Its kind of funny how people complicate things taking 'know it all attitude' instead trying to solve it as a puzzle together with the wealth of knowledge of the members of this forum. Nick, thank you so much for the last piece to complete this! I certainly felt lost with my 'osmosis' problem.

Glad that once you got the angle grinder in action that things didn't turn out as feared / possible .

Given that you never needed to use all the information offered, maybe ask for your money back? .

[psneeld]

Originally Posted by mitiempo

Here's an interesting article on blisters from Jan de Groot, a very experienced surveyor that makes interesting reading.
Sea Lake Yacht Sales (Kemah, TX)

Seems like he doesn't agree with all the resin chemists in the composite piping and tank business concerning hydrolysis...but why should he...he's an experienced surveyor......

[sabray]

Originally Posted by mitiempo

Here's an interesting article on blisters from Jan de Groot, a very experienced surveyor that makes interesting reading.
Sea Lake Yacht Sales (Kemah, TX)

Interesting but uhhh wow I'm speechless . Worst description I have read of blisters and what is occurring. Older boats did not blister because the gelcoat was so porous the resin and the new formed molecules could wash through. To blister you need pressure on the back side of the gel. I have seen boats that had structural issues do to this.

[bugmon]

Originally Posted by sabray

Interesting but uhhh wow I'm speechless . Worst description I have read of blisters and what is occurring. Older boats did not blister because the gelcoat was so porous the resin and the new formed molecules could wash through. To blister you need pressure on the back side of the gel. I have seen boats that had structural issues do to this.

I think his main point was that blisters are a cosmetic problem NOT a structural one .... that they only can occur in the chopmat and not in the layup of the vessel.

.... and to his request Sabray , can you post an example of blisters that caused a structural failure?

[sarafina]

I am going to pitch in a question here that I have always had in the back of my mind.

Has a boat ever sunk just from blisters?

When we bought our Cal a few years ago it was the first fiberglass hull I had ever dealt with. At the time I did some reading and at the end of the day I pretty much dismissed blisters as a nit. As in: most old boats have them, but they are laid up so heavily they are just not a "real" issue.

I have steadfastly refused to discuss blister repair since then having never read or seen anything to demonstrate to me that they are a real threat. But I occasionally wonder if I am missing the proverbial AND literal boat here...

Opinions?

[ShaunJ]

Sara
I think you are on the right track as long as the blisters are small. One boat I looked at had very large blisters, 6 to 12" and I was told to run away and don't look back. I would assume large and numerous blisters are bad.

[psneeld]

Originally Posted by sarafina

I am going to pitch in a question here that I have always had in the back of my mind.

Has a boat ever sunk just from blisters?

When we bought our Cal a few years ago it was the first fiberglass hull I had ever dealt with. At the time I did some reading and at the end of the day I pretty much dismissed blisters as a nit. As in: most old boats have them, but they are laid up so heavily they are just not a "real" issue.

I have steadfastly refused to discuss blister repair since then having never read or seen anything to demonstrate to me that they are a real threat. But I occasionally wonder if I am missing the proverbial AND literal boat here...

Opinions?

I am in the process of redoing my entire hull.

Blisters aren't the problem (they are just a part of the problem)...hydrolysis is.

In one section I had to grind down 6-7 layers of roving/matt (an area 3 feet by 5 feet with the deepest 3 feet by 3 feet). It accounted for about 1/4 inch through of the 1/2 inch hull thickness.

So would have my boat sunk eventually? Don't know...didn't want to take the chance. But a good thump in that area might have cracked it enough to breach it. Then again a good thump may do that to a sound hull.

Is hydrolysis a widespread problem? According to people OUTSIDE the "head up their butt" marine expert community seems to think so. The fiberglass storage tank and piping industry seen to talk about it a lot and how to monitor, slow it's effects.

If you have a fibeglass boat that doesn't have vinylester resin or a good barrier coat and lives year round in tropical waters...your boat could be just like mine. And don't expect the average surveyor to find the problem or even a moisture meter....though I thought they would have.

Till you core your hull or grind down through the gel coat...you don't know what you have.

[minaret]

Originally Posted by sarafina

I am going to pitch in a question here that I have always had in the back of my mind.

Has a boat ever sunk just from blisters?

When we bought our Cal a few years ago it was the first fiberglass hull I had ever dealt with. At the time I did some reading and at the end of the day I pretty much dismissed blisters as a nit. As in: most old boats have them, but they are laid up so heavily they are just not a "real" issue.

I have steadfastly refused to discuss blister repair since then having never read or seen anything to demonstrate to me that they are a real threat. But I occasionally wonder if I am missing the proverbial AND literal boat here...

Opinions?

I have seen truly severe cases of blistering that ended in the boat being totalled. The worst case I have ever seen was a 54' powerboat that had blisters the size of dinner plates. You had to grind down about 3/8" to open the blisters, which is halfway through the laminate. There were hundreds of them. When grinding out one of these giant blisters you would chase the delam until you hit solid glass as usual, but in this case you never would chase it out all the way, instead you'd find the blister you're working on is connected to those around it by delam. Eventually we discovered that when building the boat the factory had lost the chemical bond over a weekend and instead of grinding the whole mold for prep they just kept glassing, with very little bond at all. We ended up running a skilsaw set at 3/8" depth of cut around the whole waterline and then removing the entire outer 3/8" of laminate on a solid glass hull and re glassing and fairing it one section at a time. In the end it cost about 150k and was not covered in any way, the owner took the hit. This is an extreme example, but it goes to show that there can be many different factors at play in blistering and osmosis. Some boats will saturate due to osmosis and never blister, just weigh a lot. Others will blister severely and delaminate, which is obviously structurally dangerous. I doubt a boat has ever sunk as a result of blisters, but I have seen cases where the owner clearly WISHED the boat had sunk instead of having to deal with the massive expense of a severe blistering problem. The thing to remember is that blisters are just a symptom of osmosis and saturation, which is not good. If you have blisters, you have saturation and it needs to be dealt with. Big blisters and delam form from small blisters.

[sabray]

Originally Posted by bugmon

I think his main point was that blisters are a cosmetic problem NOT a structural one .... that they only can occur in the chopmat and not in the layup of the vessel.

.... and to his request Sabray , can you post an example of blisters that caused a structural failure?

I can attest that hydrolysis has structural implications. Sometimes it is cosmetic. I was in the business for years and peeled a lot of hulls. Sone boats had near complete delam a layer 1/4 inch in. Lighter layups had so little glass that that they could not afford the loss of resin.they were mushy. The problem is really in light layup polyester boats. Especially those that were done using minimal resin or fire retardant resins. I have seen boats with delam and blisters that were beyond the skin or finish layup. As suggested there were probably other issues. Left that business long ago so no pictures.

[psneeld]

Originally Posted by minaret

I have seen truly severe cases of blistering that ended in the boat being totalled. The worst case I have ever seen was a 54' powerboat that had blisters the size of dinner plates. You had to grind down about 3/8" to open the blisters, which is halfway through the laminate. There were hundreds of them. When grinding out one of these giant blisters you would chase the delam until you hit solid glass as usual, but in this case you never would chase it out all the way, instead you'd find the blister you're working on is connected to those around it by delam. Eventually we discovered that when building the boat the factory had lost the chemical bond over a weekend and instead of grinding the whole mold for prep they just kept glassing, with very little bond at all. We ended up running a skilsaw set at 3/8" depth of cut around the whole waterline and then removing the entire outer 3/8" of laminate on a solid glass hull and re glassing and fairing it one section at a time. In the end it cost about 150k and was not covered in any way, the owner took the hit. This is an extreme example, but it goes to show that there can be many different factors at play in blistering and osmosis. Some boats will saturate due to osmosis and never blister, just weigh a lot. Others will blister severely and delaminate, which is obviously structurally dangerous. I doubt a boat has ever sunk as a result of blisters, but I have seen cases where the owner clearly WISHED the boat had sunk instead of having to deal with the massive expense of a severe blistering problem. The thing to remember is that blisters are just a symptom of osmosis and saturation, which is not good. If you have blisters, you have saturation and it needs to be dealt with. Big blisters and delam form from small blisters.

Good post...nice that some of the big yards have the experience of seeing it first hand and knowing how to deal with it. There's not too many in the marine field unless there's more out there that aren't writing about it.

Most articles written about blisters are just the tip of the iceberg for hydrolysis.

[sabray]

Thanks minaret I was trying to say that but you summed it better. Nicely written

[bugmon]

"Some boats will saturate due to osmosis and never blister, just weigh a lot "

I dont get this, can someone please explain ... what material in the hull is saturating? Are you talking about a cored hull where the core is soaking water? ....or a poorly laidup hull that has voids and unbonded cloth?

Are you telling me that polyester resin is porus ?

[mitiempo]

Gelcoat, which is tinted resin basically, is porous. So is epoxy, although a lot less so.

A hull that is not cored can (and will) absorb water over time. But the weight increase will be small.

[Rakuflames]

Originally Posted by bugmon

I think his main point was that blisters are a cosmetic problem NOT a structural one .... that they only can occur in the chopmat and not in the layup of the vessel.

.... and to his request Sabray , can you post an example of blisters that caused a structural failure?

I have never heard of blisters being structural. Does he maybe mean moisture that got into cored fiberglass? that's not blistering but I can see where someone might think it was.

[Rakuflames]

Originally Posted by sarafina

I am going to pitch in a question here that I have always had in the back of my mind.

Has a boat ever sunk just from blisters?

When we bought our Cal a few years ago it was the first fiberglass hull I had ever dealt with. At the time I did some reading and at the end of the day I pretty much dismissed blisters as a nit. As in: most old boats have them, but they are laid up so heavily they are just not a "real" issue.

I have steadfastly refused to discuss blister repair since then having never read or seen anything to demonstrate to me that they are a real threat. But I occasionally wonder if I am missing the proverbial AND literal boat here...

Opinions?

I have heard two very respected marine surveyors (and one former surveyor) categorically state that a boat will not sink from blisters. However, if they're really bad, they can really slow the boat down.