Blisters

After 15 years in mostly warm seawater Calliste had developed only a
few small blisters, and a greater gel coat failure. The gel coat was
removed with an electric peeler, then the hull was sanded with 36
grit random orbit sander to remove the peeler marks. After 2 weeks
the exposed hull area was steam cleaned. Now a year later, the
moisture meter shows the hull to be dry and ready for some filling in
spots and to apply a barrier coating.

I thought I was going to use epoxy filler and an epoxy barrier coat,
until I read the “Blister Repairs Part II” report at website
www.yachtsurvey.com and also read here, Geary Smith’s coments of
blistering on his Foss Foam rudder, and his repairs.

Does anyone have a product success story with gel coat and blister
repairs on an older boat, that they would share with us ?

Douglas

Douglas, I’ve already written about my recent “experience” with blister
repairs, but it might be helpful if I give some details and explain why I
chose the repair approach I did.

“Caylin” was delivered to me new from the factory in June of 1991. Because
preventing blistering was very important to me, I decided to apply an epoxy
barrier coat before her first launch. At the time there were several epoxy
products available, but I decided to go with West Systems primarily due to
their reputation and helpfulness. Nine coats of epoxy resin with the
recommended filler were applied. Much to my dismay, the manager of the yard
told me that they were already seeing boats that had blisters showing up
despite the epoxy barrier coat. I crossed my fingers, said a few prayers
and hoped for the best. Three years later during a quick haul, I discovered
numerous dime sized or smaller blisters on the rudder. A friend of mine who
worked at yard suggested that I don’t worry about it. I took his advice and
over the years it never got worse although I did worry that there might be
water in the rudder.

Early this Spring I hauled the boat, and the dreaded blisters were there.
There were numerous small blisters mainly just below the waterline on the
starboard side with a few below the waterline on the port side. I
immediately began gathering as much information as I could. I read
everything I could find on the Internet, talked to the yard owner, consulted
with a surveyor friend, and talked extensively with the repairperson who was
recommended to me. All of these people told me of experiences with boats in
which the epoxy barrier coat had failed. The man who repaired “Caylin” has
had over twenty years experience with blister repairs in our area. My gut
feeling was to go with the advice of these people because they have had
first hand experience with what works and doesn’t in our area. Because it
had failed on my boat, I did not have confidence in epoxy. My dilemma was
that I did not want to apply a different product over the epoxy I had on my
boat. I did not want to create a hodgepodge of different materials. I
therefore opted for removal of the entire gel coat below the waterline. The
positives for me were that the blisters were very small, there was no
structural damage to the laminates, and the moisture readings on my hull
were surprisingly very low (including the rudder). All of the people I
consulted with pointed me to a repair that involved vinyl ester resin. The
repairperson told me that he had been using vinyl ester resin to repair
blisters for over seven years and has yet to have one of these boats have a
recurrence of blistering. He was able to show me the first boat he had ever
repaired using the Dura Tech vinyl ester resin. His repair involved peeling
away the mat where the blistering occurred. The hull was then allowed to
dry for two months. At this point the moisture readings were well below
what was required before repairs could begin. Next, after some grinding; he
began filling and fairing with 3M vinyl ester structural filler. He then
sprayed on several coats of the Dura Tech vinyl ester resin with more
sanding, filling, and fairing between spray coats. (One thing I learned
during this process is that most vinyl ester resin is made by Dow Chemical
and then marketed under different names by other companies.) This was a
lengthy process, but I was lucky because my repairman was a perfectionist.
By the time he was finished, you couldn’t tell the difference between my
hull and a new one in terms of fairness. This was not an inexpensive
repair. The total cost of the labor, materials, and yard bill came to just
under $8000. However, because these are such well-built boats, I felt he
was worth the cost to maintain the integrity and value of the boat.

Please don’t interpret this as a recommendation that you use the vinyl ester
on your boat. You have to do what you feel is best. My investigations on
the Internet showed me that most builders of quality boats are now using
vinyl ester resin below the waterline. More importantly to me, was the
advice of the people who work with the materials and boats on a daily basis.
I hope this helps.

Sincerely, Geary Smith

Satori Hull #94 was pulled out for a routine bottom job. To my serious dismay, it
became apparent the I had a blister problem. With just light sanding to knock the
loose antifouling paint off many many small high spots presented themselves. When
punctured these were fluid filled. There are a few large blisters several inches across.

I began to try and get some information about what to do. What a quagmire of
different approaches. I am looking for help in making a final decision about what to
do. The options ranged from-- ignore them slap a coat of bottom paint on and go
about your business–to peel the hull, dry the hull, apply another layer of glass and
then barrier coat to the tune of $350 a foot-- ouch!!

I can’t see ignoring them-- there are thousands of small fluid filled blisters- they can
only get worse. No way in hell I can individualy pop each one and treat as isolated
blister. There is some good news-- the blisters are largly contained in the gel coat
layer except for a few spots the laminate appears intact.

I can’t see subjecting my baby to peeling when the first glass layer appears ok. So
here is my plan- grind all the gel coat off - use the hot vac system to dry the hull and
then use The interprotect system to barrier coat the hull. Technical Bulletin #900E
from interlux gives the procedure- which is complex with many steps- but I can’t
come up with an alternative. This is going to cost major bucks. Any comments-
Help! Pat- High and dry on Satori

Try getting blister info at www.osmosisinfo.com this system was
used on my BCC 3 years ago, and not had any more blisters.

I had the same situation on Ho'okahiko #97.  I ground off the gel coat, allowed 2 months passive drying then faired the hull and coated with 9 coats of West System epoxy. With the gelcoat off I found the hull to have alot of moisture just beneath the first layer of laminate. In a few areas it had gone a little deeper so caused some delamination. Now 5 years later during a recent haul out I had to treat 13 blisters. I attribute that to somewhat inadaquate drying before applying the barrier coat. It sounds to me like you are on the right track.
Ron Thompson  
----- Original Message -----
Sent: Wednesday, September 29, 2004 7:48 AM
Subject: [bcc] Blisters

Satori Hull #94 was pulled out for a routine bottom job. To my serious dismay, it
became apparent the I had a blister problem.  With just light sanding to knock the
loose antifouling paint off many many small high spots presented themselves.  When
punctured these were fluid filled.  There are a few large blisters several inches across.

I began to try and get some information about what to do.  What a quagmire of
different approaches.  I am looking for help in making a final decision about what to
do.  The options ranged from-- ignore them slap a coat of bottom paint on and go
about your business--to peel the hull, dry the hull, apply another layer of glass and
then barrier coat to the tune of $350 a foot-- ouch!!

I can't see ignoring them-- there are thousands of small fluid filled blisters- they can
only get worse.  No way in hell I can individualy pop each one and treat as isolated
blister.  There is some good news-- the blisters are largly contained in the gel coat
layer except for a few spots the laminate appears intact.

I can't see subjecting my baby to peeling when the first glass layer appears ok.  So
here is my plan- grind all the gel coat off - use the hot vac system to dry the hull and
then use The interprotect system to barrier coat the hull.  Technical Bulletin #900E
from interlux gives the procedure- which is complex with many steps- but I can't
come up with an alternative.  This is going to cost major bucks.  Any comments-
Help!  Pat- High and dry on Satori




Satori hull #94 presented with hundreds if not thousands of small blisters
upon haul out. For the most part the laminate appears sound, although there
are some quarter size blisters that extend into the laminate. I have been
trying to convince myself that I do not need to reglass at this point. My plan
whether flawed or not is to remove the gel coat down to laminate. Treat with
the hot vac system and then recoat with a vinal ester risen. I have been
removing the gel coat with a large variable speed disc sander with padded
backing and the stick on 24 grit disks. Its hard dirty work- maybe thats why no
one wants to do it. If there is plenty of thickness of laminate why reglass- if
there is moisture in the hull and the hydrolysis process continues of course
blisters will reoccur-- perhaps that is why some boat yards like to reglass- they
cover up the potential for reblistering, hence they can give a guarantee. Your
thoughts appreciated–Pat