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??

Shamrock also has gelcoat blisters, we have a letter on file from Sam Morse regarding the problem; it seams back then, they figured if one coat of gelcoat was good, two should be better, not as the case turn out.We did extensive research regarding the subject of gelcoat blister and laminate blisters over the years and promise not to bore you with the details.
Repair in the past has consisted of grinding off the gelcoat and subsequent layers of affected glass and?re-glassing the hull and barrier coat.The current tooling consists of a modified hand operated wood plainer, called what else, a peeler. The positive result is a more uniform cut in skilled hands. The key point here is skilled hands, the best tools in the wrong hand can make a mess of things. I have found two of these tools on the market,?the?best one on the market is call a?Gelplane out of Europe at $3000, the other out of Canada runs around $1300 lacks the?safeguards of dead man switch and handles to keep your little fingers out of the way, can’t remember the name of their product.There are two approaches to peeling, the single or double cut, in the single cut?they make a shallow pass with the peeler removing the gelcoat only and see if there is?delamination under the gelcoat. If delamination is present, a second pass is required. Obviously, the double pass technique is more expensive as there is twice the time and effort involved. On the other hand, a deep single pass takes off gelcoat and 2 layers of glass, ensures the usually affected layers are taken with a single pass; positive effect is lower peeling costs and faster drying times.We priced the peeling cost for Shamrock at $3000, total cost for peeling, re-glass with two layer of angle hair glass, epoxy and bottom coat is $12,000.
This is where the critical choice comes in, most boats are built with angel hair glass mat (very fine random directional fiber mat cloth) near the gelcoat to prevent glass cloth print through effect, the checkerboard affect you see on some boats that apply bi-directional woven cloth against the gelcoat in the mold. Most critics of blister contend that the difficulty of saturating angle hair mat leaves voids, air pockets and uncured resins which lead to blisters; subsequently suggest re-glassing after peeling with glass cloth. Our local yard uses two layers of angel hair cloth bathed in epoxy and has no history of reoccurring of blisters. The choice is yours.
In either case, if you have the yard do the work, check the fine print of the warranty, longer the warranty the better. Go to a well established yard with a sound financial background, make sure they will be around for awhile. Generally, but not always, yards that give a longer warranty period usually have a good record of repair. Baring the case of the business idiot, most business know a repair will only last so long and provide a warranty that extends up to a point short of when the repair needs to be repeated. Ever have something that broke the day after the warranty expired?
In the early days of blister repair, when barrier coating was the panacea, many yards gave outrages warranties, 10 years in some cases, are subsequently taking it in the shorts so to speak as blisters are reappearing every couple of years.
Marty Chin, BCC Shamrock.

We are still shopping around and looking at boats at various yards checking quality and processes being used before we commit Shamrock to the gelcoat peeler.

Equally distressing is the letter from Roger Olson received 4 years ago but dated, believe it or not, “May 30, 2005 2:05 PM” looks like Rogers computer clock was a little screwed up; for that matter so was his account of the history of Shamrock.

Back then Sam Morse had Crystalliner add a second coat of gelcoat to the bottom and the trapped resin did not cure; it also appear the original owner John Perbaugh, the first buyer, asked for additional gelcoat, so does this make 3 coats?

Roger goes on to suggest, not sure because it was before his watch, the gelcoat may have been stripped and a barrier coat may have been applied. In short, this throws all the estimates we have out the window… I looks like we will have to haul and cut a window to make an assessment of the situation and go from there.
I took a look at some boats being gelcoat peeled only, no deep peeling including glass layers, Smith saturation epoxy, epoxy fared and 4 coats of barrier coat, at Napa Valley Marina today.

They did a 40+ power boat with speed rails molded in, nice work, good faring job. They also had a 50’ catamaran gelcoat peeled and same process in the works, looks to be more of a fair job than I’m seeing elsewhere. Only down side seems to be the long trek north up the Napa River every year to haul and verify integrity of work and repair any new blisters if found (covered by warranty), If found, this will probably mean another 3 months on the hard waiting for the hull to dry pending repairs. If all goes well, it comes with a 5 year warranty at $5,880.00 for the job, this is half the cost of a deep peel and 2 layers of glass.

Dear Marty,
I’m certainly empathetic to your problem.
I do have a suggestion. Before you commit to anything: call Rich Worstell at Valiant Yachts. He is a dear old friend and probably has more experience with
blistering than anyone anywhere. Valiant as you recall had the biggest blister problem in the industry until he purchased the company and reformed the building
He is still repairing first generation boats, still. Peel, drying and vinylester or epoxy coating is pretty standard these days with a layer of vinylester soaked
mat if problem is deeper. Some anecdotal evidence suggest vinylester is better than epoxy for staving off future problems
Personally, I wouldn’t get too cranked up over the problem because with the exception of a few boats with fire-resistant resins and woven only layups the problem is limited to cosmetics. A good dry-out and recoating works fine.
Don’t forget about the possibility of water migrating from the inside as well. Bilge should be dry and evencoated if possible
If you want to contact me directly feel free to do so.

Hi Marty,I am familiar with your boat and knew John Perbaugh.

I was there when the boat was hauled and the decision was made to do?the blister job. I think the gel coat was completely removed by grinder. A barrier coat was applied and boat was back in the water in a week.

Ala Wai?Marine did the work. This was around 1994 but I’m not exactly sure.

The blistering it had was primarily very small blisters but?there were hundreds of them. Also there were a handful of quarter sized ones. So that’s about all I can tell you about the blister repair.

Ron Thompson
Ho’okahiko #97???

We just spent the last two days In Svendsen’s Marine Yard wet
sanding the bottom with 25 grit green disks, a random orbit air
sander and a water hose.

In the process of discovery, we found bottom paint over faring
compound, epoxy barrier coat, yellowed epoxy and finally glass mat.
We were instructed to try Interlux Interstrip (pinoff) to take the
paint off (20 minutes to 2 hours wait time recommended on the can)
at $26 per quart, temperature has a large effect on removal time (60
deg), we did manage to loosen the paint in 1 hour and scraped a
test patch off with a carbide scraper, did not affect the epoxy
barrier coat.

We later tired a test patch of Jesco paint and epoxy remover,
dangerous stuff concerning fiberglass hull, possibility of damaging
the fiberglass they say. We applied it over the bottom paint, paint
started running down the hull in as little as 10 minutes, still no
affect on softening the epoxy barrier coat. We stopped testing for
fear of penetrating the beyond the epoxy barrier coat and attacking
the fiberglass.

For removing the paint only, we found a sharp carbide blade in a
Sandvik scraper with only modest pressure out performed the chemical
strippers, non-toxic, smooth cut and much easier on the wallet.

Best course of action, most painful, if not tiring, seemed to be 25
grit green disks on the random orbit sander, with water to wash away
the sludge left behind while sanding. The paint came off quickly,
barrier coat took more effort to slowly grind away down to bare

We sanded down both sides of the hull from the bow back 6 feet, the
barrier coat blister were 1/4" in size and tightly spaced on both
sides, failure probably due to inadequate hull drying time prior to
application. We found laminate blister under the matt cloth, quarter
sized and widely spaced on the port side; 2" sized blister under the
matt closely spaced on the starboard side, all seem to be shallow at
present limited to the matt.

The current plan is to have Svendsen’s do a peel down to the first
layer of cloth and see what this reveals, we are hopeful from
present visual evidence that only the mat is affected. Planning on
peeling this Thursday or Friday.

Research and conversations with hull builders suggest a times there
is no rime or reason for blisters in some boats, two boats built at
the same time from the same materials, one could develop blister
and the other did not, who knows.

I don’t think the development of blisters in our boat in anyway
negatively reflects on the BCC as a whole, I’m quite sure from a
structural strength standpoint, she could shed a few layers of glass
and still survive a hurricane, a sound beaching and still come out
of it intact. It’s actually more of a cosmetic issue at this stage.

In any event, I think it is important to discuss what we find, what
products work an to what degree, costs etc, simply for the sake of
education of the group.

The plan thus far is to peel, dry to 5% moisture content, add two
layers of glass with West Epoxy, fare, epoxy barrier coat, bottom
paint and get back to sailing.

Best wishes to all.

Marty Chin, BCC Shamrock.

I noticed you mentioned an epoxy barrier coat. I thought this was
supposed to insulate against blisters? I have an epoxy barrier
coat on Godspeed. Should I be looking for blisters as well? Thanks,

Mark Gearhart
s/v Godspeed


Any thought to using Vinylester resin instead of epoxy for your barrier coat?

CoREZYN VE resin is the hot ticket these days. (and not as temperature sensitive)

A recent study:

The vinyl ester used in the low HAP series is part of the same resin formula evaluated in the Interplastic Corporation 15-year immersion study. Laboratory analysis concluded that after 15 years of immersion in water at ambient temperatures, laminate panels constructed with 100% CoREZYN vinyl ester resin or a vinyl ester skin coat showed no signs of blistering. The CoREZYN vinyl ester resin created a barrier impervious to water and therefore prevented osmotic blistering.

Fair winds

Frequently the epoxy coat becomes the barrier that traps the inchoate
moisture and allows it to percolate. Many differing opinions abound on
the efficacy of epoxy. Some say vinylester is a better barrier coat.
Normally the once repaired laminate is spared from structural problems
and the damage is limited to the layer immediately following the epoxy.
The blister issue is very complicated and other than using Isothalic
resins or vinylester resins for skin coats or the first few layers
coupled with careful layups without voids and done with powder bound
mats there are no guarantees.

I speced all vinylester resin for Cyrano but that only lessens the
likelihood of blistering it doesn’t eliminate it

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 vinylester resin.

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 that’s 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


You are of course correct. That’s why all my boats are Vinylester.

On the Nor’Sea’s and Montgomery sailboats with the Vinylester resins
NO blisters have occurred. (some as old as 20 years in the water full time)

Vinylester costs about 70% more per drum but the added cost (about
$1100 for three laminations on the Nor’Sea) is well worth the money.

On any boat it is sound advice to specify Vinylester Resin to prevent future
problems. ( I saw your hull after lay up; didn’t you have some KEVLAR
installed as well?)

Probably the strongest hull around.

Fair winds

Day one of Shamrocks fiberglass peeling went well, starboard side done and 1/3 of the port side as well. Svendsen’s Marine deep cut to remove all the mat, some cloth and in one area down to the woven roving, remaining glass has some voids/dry spots which will be ground out, but for the most part the remaining glass looks great, clean, dry and blister free.
Most of the problem with current blistering in the epoxy barrier coat and mat can be traced to inadequate drying time back when the gelcoat was peeled in 1994, they peeled, epoxied, barrier coated, bottom painted and splashed in one week, no drying time. The moisture trapped in the hull, mostly in the mat, caused blisters to form in the mat and under the epoxy. It’s sort of like getting a deck leak and sealing it from inside the boat, water has no where to go but into the core material, temperature caused the core and water to expand and contract, delamination occurs.?
I have been studying osmosis reports and finding for 10 years and will never consider myself and expert in the field, conflicting information and proclaimed cures seem to be the norm. Most proclaimed successful test reports I read with a grain of salt, some I find suspect. In particular, the product test panels I find interesting, but find it difficult to support as conclusive proof of one product viability over another, or testament of proof of survivability in a real world environment.
Case in point, to calculate the viability of a material for permeability in relation to the displacement of the BCC 14,000 pounds, the entire hull is displacing 14,000 pound of water, 8.345404 pound per gallon, a 1 square foot section of the hull is carrying only a fraction of the total displacement, water pressure is greater near the keel than on the surface. I don’t know what the actual pressure exerted on the hull is at either section of the hull, but I have to believe it is greater than a test panel suspended/submerged in a test tank of water. In addition, what chemical pollutants are introduced into the test tank to simulate marina environment, diesel fuel, oil, paint thinner, acetone etc? As I said earlier, I find the test panels interesting, but not conclusive.
As stated earlier, I’m a diesel mechanic who has taken a keen interest in boat design and construction, built boats and performed all facets of boat repair successfully over the last 20 years, by no mean do I consider myself a osmosis expert,?every day I?learning something new.
Osmosis prevention starts with quality products, mixed carefully and applied to avoid excess resin, air, and?to ensure through wetting of the fiberglass products. Hand lay up of fiberglass products (FRP) provides better product control and distribution through the glass. The best fiberglass applicators I’ve seen of late, seem to be high-end FRP kayak builders of ultra-light kayaks, turn boat hull builders; not an once of excess resin, all resin and hardeners mixed to perfection, every ounce of glass saturated and squeeged to perfection, they make some of the lightest and strongest?hulls you will ever see.
Polyester resin is still a good product, popular opinion suggests vinylester?and epoxy are?reasonably good at “reducing” formation of blisters, vinylester costs forming a mid point between?between polyester and epoxy. Prevailing opinion suggest epoxy is only slightly more effective than vinylester in preventing osmosis, while others contend the additional cost of epoxy may not be justified.
Material costs and labor are significantly higher with epoxy, it is a little more challenging to work with, as many builder find polyester and vinylester more easy to control in a production setting.
Our choice of epoxy for Shamrock new lay up had nothing to do with weather vinylester or epoxy is any better than the other; We chose epoxy as it is a familiar product that we have been using for years with excellent results. Our yard and its applicators have an excellent 10 year track record using epoxy in osmosis repair with the West System products.
I believe both products will work just fine in reducing osmosis.?The key to success will depend more?on adequate drying of the hull, surface preparation, experienced product applicators and a decent warranty. We learned a long?ago, never ask someone to do something they are not either thoroughly experienced?or comfortable in performing. Our yard has extensive background in epoxy repair, and lay up, a good track record, is very comfortable and confident in backing their work and so are we.
Best wishes to all,
Marty Chin, BCC Shamrock

As the former owner of Dilkara, hull number 14, I was absolutely flabbergasted and dismayed when on one particular hauling after about five continuous years in the water to find my beautiful boat covered with hundreds, if not thousands, of tiny blisters.

This was back in the eighties and blisters were still a fairly shocking phenomenon other than the ill fated Valiants of those days.

Before Dilkara was ever launched she was coated with several layers of epoxy so my belief is certainly that the moisture was already between the hull and gel coat.

Once when hauling the pressure washing removed literally sheets of bottom paint down to this incredibly slick coat of epoxy. There were absolutely no blisters evident at that time.

When I found the blisters I stripped the hull and ground out every single blister that I could find until there was absolutely no moisture to be found. I waited several days and if any moisture had appeared ground out more. My beloved Dilkara looked as if she had the worst case of measles ever.

I then filled every single hole with some sort of epoxy, I can’t remember exactly what, and tried to fair them as best as I could. By this time I was so exhausted that the finished product was somewhat lumpy but I thought, what the hell, nobody is going to see it, slapped some bottom paint on and headed for Venezuela.

After another two or three years I spotted a few more small blisters but quit worrying about them. I don’t know how Dilkara fared after I sold her but that hull was so thick that I figured it would be years before there was any really serious problem.

When I would haul every year to paint the bottom I sort had a fondness for every one of those little lumps that I had helped create. I always intended to do a proper job later but somehow ran out of time. Too busy sailing and having a good time. Incidentally, I used only 14 gallons of fuel between the Bahamas and Venezuela.
Ray Walton

Yes, I had Ray Richards design a new BCC layup that used all vinylester resin and added 8 layers of kevlar in the bow, down the center and in areas where ice
abrasion might be possible.

He used ice class standards because of my desire to sail to Spitzbergen at Lat 80n.

We also added a watertight bulkhead at the bow. Also took a bit of weight and balance work to keep her floating on her lines. Worked out fine though.

LPS did go from 130 deg to 124 deg dry though. Wet it was about 131 deg vs 134 deg standard.


Well, here we are waiting for the hull to dry out on Shamrock hull 92. Svendsen’s Marine in Alameda,CA. is doing an excellent job. Svendsens peeled down past the 7.5 oz. mat to remove all the blisters and the bulk of the moisture. We had a multitude of voids, air pockets and lay-up contaminates in the mat and first few layers of cloth, even found a few small chunks of wood in the cloth. Don’t panic, this is typical of production boats, even the multi-million dollar boats.

The peeler they are using is called a Gelplane, incredible tool, makes quick work of the peel process, 1.5 days to peel, 2 days to trim, sand, pry off any loose layer of glass and fare the hull for glass lay-up.

We are down to green, clear glass, plenty of hull thickness left, still 3/4" at the head discharge thru-hull near the keel, 3/8-1/2" at the thru-hull fittings higher up the hull; after laying up 3 layers of glass and epoxy, we should be back up to the original hull thickness.

Moisture readings over the entire hull bottom prior to peeling were over 30%, we only have one area at the keel, center of the hull which is at 25%, remainder of the hull is around 12-15%, moisture levels dropping like a rock, down 5% since last night.

In retrospect, we feel we made a good decision to peel and not screw around with grinding and patching. We had a lot of pressure from friends and others to patch and sail or sell, passing the problem on to the next party, not something we are acustomed to doing. The guys at Svendsen’s Marine are some of the best in the industry at glass work, have see may examples of their work over the years, when our hull is complete, I suspect Shamrock will be as strong as, if not stronger than the day she was built.

In researching osmosis, I did not find one boat manufacturer that didn’t experience osmotic blister in one form or another through their entire production run, I seen hulls built before and after a hull which had blister, have no blisters at all; have seen two hulls built side by side with the same crews and materials, one got blisters and the other did not. In other words, no manufacturer is exempt, popular opinion regarding osmosis is, it not a matter of if a hull will get blisters, it’s a matter of degree of severity and when it will occur. No product, polyester, vinylester or epoxy will totaly elimate osmotic blister in FRP boats, better products like vinylester and epoxy will definately slow the process. Nothing lasts for ever; I think our Mr. Cofee machine is #50 in the line-up.

Fiberglass hull building is a nasty, filthy, toxic environment to work in; I can remember when we worked in blue jeans, t-shirts and sneakers, no respirators-protective clothing, sticky from head to toe with resin and glass particles stuck everywhere. Back then, we didn’t know removing resin from our skin with acetone was a stupid thing to do, draws the resin directly into the skin, use white vinegar. We worked in a shed with a rock floor often still damp from the last rain, air, wind, dust and rain coming through the cracks in the wall; slapped together plywood tables for laying out glass, bare plywood holds moisture, leave a piece of cloth on the table overnight and it picks up moisture, can’t feel it, but it’s there. Still make me itch just thinking about it, it wasn’t until years later that we learned how toxic epoxy was to work with, suprised our son didn’t come out with two heads in stead of one…

Work place hygene, clean lay-up areas, protective clothing, respirators, all contribute to safer and healthy working environment;, better construction material products, tools and techniques are helping to produce more durable products.

We are still very much in love with Shamrock, the SLM folks did a heck of a job building her.
If we didn’t own a BCC, we would still be out there looking to buy one.


Marty & Linda Chin
BCC Shamrock