Dry Blisters

[TommyB]

Hauled the boat out last weds to get ready for trip to the islands in may.
Found a bunch of what I guess you call blisters, but they are not really blisters in the sense they they hold no water/styrene?
They are all dry, and there is dry fiberglass stands showing

Should I worry?
I ground a few down to good glass, but what is causing?
Thanks!!

 

[TommyB]

Few more.
Don't mind the helper
Florida Weather is great right now

 

[lumina]

Hi All,

Tommy, when we purchased our boat it had many many of what I call "acne" which you call dry blisters. It presented as poc marks on the hull covered by bottom paint but completely dry ie no bubble (blister) no drainage. Initially I was going to pass on this boat but I had been looking for this exact model in original condition for 3 years. The surveyor did an extensive exam and explained to me that someone had done a "florida" bottom job which he defined as opening the blisters, cleaning them out, drying them, applying a barrier coat then ablative (the missing steps being grinding and filling).

8 years later they are much the same as when we bought her.

In 2014 I had the entire hull surveyed by Jamestown Boatyard out of RI. They did what they called a destructive survey where they not only tapped and took moisture readings of the entire bottom, but they chose several areas and ground into the hull as much as 3/4 of an inch 4, 6, 8 inches around. The survey came back fine. No delamination, no structural impact, and a dry hull. Surveyor said he is always amazed at the solid robust build of our hulls.

This may not apply to everyone with your symptoms, but my guess is your hull is fine.

Every spring I grind a couple spots down ever so slightly, prep it, fill it with thickened epoxy, sand, barrier coat it, and then paint the bottom. I'm doing this only for cosmetic and drag reasons.

 

[Tim Powell]

Maybee scott will chime but you might like to put some barier coat on thse spots.

 

[saltshaker]

Hard to say just from the pictures but if that was my boat she wouldn't go back in the water until that bottom was fixed. Looks like you had blisters that someone opened up. Blisters on a Hatt aren't usually a problem until they are opened up. Exposed mat is not a good thing. Once you ground them out you made them more vulnerable. If your whole bottom looks like that then I'd strip it repair it then barrier coat it. Gene I'm surprised a surveyor didn't recommend sealing your up. Hatts have a strong bottom and blisters are typically a non issue until someone decides to open them up. Now the glass is exposed and water will penetrate the glass. It may take a while to see the damage but I'd bet good money it will deteriorate over time.

 

[jim rosenthal]

I think Jack is right. You can fix this piecemeal, which isn't really fixing it, or you can thoroughly dry the hull (weeks in the sun), soda blast all the bottom paint off, grind them all out, and fill and fair them, and then barrier-coat the entire hull. When my Hatteras was done, they used Interprotect, but there are other products available now, too. They also wet-blasted the entire hull to get a good tooth for the VC Watertite and barrier coat to bond to. I think you are better off having the job done right, on the entire underwater surface right up to the boot stripe.

 

[lumina]

Hi All,

Jack, that's what I expected to hear, but it was a suggestion for the future when time out of the water and $$ permit. The Jamestown folks attributed the condition to the multi layer barrier coat applied after the blisters were opened. You could see it in the areas they ground out. 3 distinct layers, off white/black/off white all covered by tons of ablative.

I must say i was happy to see the moisture readings come back so low, and the thickness of the hull is amazing. Beneth the transome he ground to a depth of an inch and a half, amidships about an inch and a quarter and an inch at the bow.

I've talked to my yard about blasting it at the beginning of March, then letting it dry (protected and with drying assistance) until the first week of June then and Brendan and I will grind, repair, barrier coat and paint it.

Still waiting on the yard.

I have images from the survey somewhere. Let me look.

 

[saltshaker]

Hi All,

Jack, that's what I expected to hear, but it was a suggestion for the future when time out of the water and $$ permit. The Jamestown folks attributed the condition to the multi layer barrier coat applied after the blisters were opened. You could see it in the areas they ground out. 3 distinct layers, off white/black/off white all covered by tons of ablative.

I must say i was happy to see the moisture readings come back so low, and the thickness of the hull is amazing. Beneth the transome he ground to a depth of an inch and a half, amidships about an inch and a quarter and an inch at the bow.

I've talked to my yard about blasting it at the beginning of March, then letting it dry (protected and with drying assistance) until the first week of June then and Brendan and I will grind, repair, barrier coat and paint it.

Still waiting on the yard.

I have images from the survey somewhere. Let me look.

That's the difference, yours weren't filled and faired but they were sealed with the barrier coat. What you are seeing now is most likely the barrier coat comming off due to poor prep.

 

[MikeP]

Hatt blisters are extensively reported/documented. They are a cosmetic issue only. I understand the concern re the appearance but since the appearance only matters when the boat is out of the water, spending a lot of money to "correct" the problem seems a waste of money. However, we all decide what is important to us as owners so if the appearance of the blisters is important to the owner, then they must be addressed. If not, then no action is necessary. It is well documented that on Hatts there is no issue to worry about.

 

[rsmith]

Hatt blisters are extensively reported/documented. They are a cosmetic issue only. I understand the concern re the appearance but since the appearance only matters when the boat is out of the water, spending a lot of money to "correct" the problem seems a waste of money. However, we all decide what is important to us as owners so if the appearance of the blisters is important to the owner, then they must be addressed. If not, then no action is necessary. It is well documented that on Hatts there is no issue to worry about.

A lot of people are very concerned about what the fish are saying about them.

 

[saltshaker]

Hatt blisters are extensively reported/documented. They are a cosmetic issue only. I understand the concern re the appearance but since the appearance only matters when the boat is out of the water, spending a lot of money to "correct" the problem seems a waste of money. However, we all decide what is important to us as owners so if the appearance of the blisters is important to the owner, then they must be addressed. If not, then no action is necessary. It is well documented that on Hatts there is no issue to worry about.

Not true once the blisters are opened up. Leave them alone and they are fine. Open them up and don't fix them and you'll end up with a wet bottom.

 

[TommyB]

Not true once the blisters are opened up. Leave them alone and they are fine. Open them up and don't fix them and you'll end up with a wet bottom.

Confused. If they open on their own then it's ok? But if you mess with them they should be fixed?

Kinda of a stupid question next
What;s the different of fixing / re-glassing a replaced through-hull vs blister. Both require some grinding on the hull and adding new glass.
You bevel out an area to close off a no longer needed through-hull and same with a crack / blister.
what's the difference? The amount of glass you add ?

 

[saltshaker]

Confused. If they open on their own then it's ok? But if you mess with them they should be fixed?

Kinda of a stupid question next
What;s the different of fixing / re-glassing a replaced through-hull vs blister. Both require some grinding on the hull and adding new glass.
You bevel out an area to close off a no longer needed through-hull and same with a crack / blister.
what's the difference? The amount of glass you add ?

What I was trying to say is they are fine if they aren't opened up. They don't open on their own.

 

[Boatsb]

What I was trying to say is they are fine if they aren't opened up. They don't open on their own.

There's a big difference between a repair and a blister. A repair done right will not only be spread over a large area but barrier coated.

 

[TommyB]

What I was trying to say is they are fine if they aren't opened up. They don't open on their own.

ahhh, understand. These on this boat are all cracked open with dry fiberglass broken stands showing. I did not open them.

But guessing they need to be fixed either way

 

[jim rosenthal]

Didn't Hatteras alternate the colors used in the gelcoat layers when they laid up the bottom- one layer is black and one is white?

 

[Cricket]

Yep, they used alternating black and white gelcoat.

 

[Vincentc]

So time ago I undertook to fix the blisters on a 1976 Gulfstar 43 MY. Nothing had been done to the blisters before that. There were hundreds of blisters ranging from dime size to the size of half grapefruit . There were several areas where the FG had delaminated and had to be cut out and restored. I can see how it could be a serious issue if water can get between layers of cloth/mat. IMO, Any ground out areas should at the least, be thoroughly dried, sealed, filled and sealed with appropriate epoxy. If you apply coats of epoxy within say 12 hours of each other you will get a better bond.

 

[lumina]

Yep, they used alternating black and white gelcoat.

Hi All,

My triple coating was confirmed as a barrier coat. It's actually pastel yellow, black, pastel yellow.

 

[TommyB]

Here's a few pics of the progression. Took awhile. But splashed may 10. Headed out
the Abacos on May 12th for a month