Blister Question

[SoWhat]

I would never try to use a belt sander to remove bottom paint. Bottom paint is a haz material and a belt sander will throw it all over even with a shop vac hooked up to it. Besides it will be very difficult to sand the bottom evenly working upside down. Much better to have the bottom professionally soda blasted.

Soda blasting is banned in Boston. EPA won't let anyone do it.
Sanding bottom paint requires ground tarps and plastic sheeting around hull to keep dust contained. Holding a belt sander over your head for hours is exhausting, but a DOA sander would take forever to remove 9 or 10 coats. I wore a full face mask. Paint is very hazardous but risk is manageable. I used 40g with belt, then 60 with DOA, then 80 before west barrier coats.

 

[SoWhat]

Was curious about SoWhat's name and whether or not it had anything to do with the Miles track of the same name on "Kind of Blue" ... one of my faves

our last boat was named TakeFive.

 

[Comodave]

Soda blasting is banned in Boston. EPA won't let anyone do it.
Sanding bottom paint requires ground tarps and plastic sheeting around hull to keep dust contained. Holding a belt sander over your head for hours is exhausting, but a DOA sander would take forever to remove 9 or 10 coats. I wore a full face mask. Paint is very hazardous but risk is manageable. I used 40g with belt, then 60 with DOA, then 80 before west barrier coats.

Before I would do that I would cruise outside of Boston and have it soda blasted.

 

[JohnO]

our last boat was named TakeFive.

Ha - I like the way you roll! Another great, although I'm partial to Bill Evans and Keith Jarrett myself. Love the naming idea.

 

[BruceK]

Soda blasting is banned in Boston. EPA won't let anyone do it.
Sanding bottom paint requires ground tarps and plastic sheeting around hull to keep dust contained. Holding a belt sander over your head for hours is exhausting, but a DOA sander would take forever to remove 9 or 10 coats. I wore a full face mask. Paint is very hazardous but risk is manageable. I used 40g with belt, then 60 with DOA, then 80 before west barrier coats.

What about Peel Plane? Banned at a nearby marina due to the noise aspect, but otherwise it might be ok. I considered it for one boat I was looking at.
As to boat names, I planned renaming one "Incognito" but bought another with an acceptable neutral name 'Sojourn".
We did a complete hard dry machine sand of my IG36 post osmosis work. Hard dirty work,even masked we were coughing muck for days. Nice smooth bottom, but never again.

 

[CaptBud]

Been there - done that........some of the large blisters, elongated usually 2" X 4", when ground out actually went right through the hull........won the lawsuit but had to pay the attorney 1/3. Keeping a boat in warm water for extended periods exazerbates the problem. 40' Willard made from fire retardant resin as required by military specs. for their fast attack boats made by Willard. Hull always showes WET with moisture meter. Same product used by Uniflight

 

[PMF1984]

Soda blasting is banned in Boston. EPA won't let anyone do.

Not sure that is correct. I saw some soda blasting this last season in Fairhaven, Mass. at the shipyard there.

They do have to encapsulate the hull to collect all the stuff that comes off, a big part of the cost.

Could be the yard just didn’t want to be troubled by it. Which is strange as this is something that is farmed out because of the specialized equipment.

There is not better way to get the old paint off. Using a belt sander is not a realistic option. (Not that it can’t be done, but it would be like building a house without power tools, possible, but why?)

 

[Group9]

I would never try to use a belt sander to remove bottom paint. Bottom paint is a haz material and a belt sander will throw it all over even with a shop vac hooked up to it. Besides it will be very difficult to sand the bottom evenly working upside down. Much better to have the bottom professionally soda blasted. It isn’t that expensive in the scheme of things and your health is more important. Then you can do the blister repairs yourself. It isn’t that difficult except it also is upside down. After all the repairs you need to put on an epoxy barrier coat, that is a must not optional. Do not just do 2 coats. Do what the manufacturer specifies. The last boat I did they said to use 5 gallons of epoxy so I did 6 gallons. You just keep doing coats until you have used all the specified amount of paint. In my case it was 6 coats. Then do the bottom paint. You have to recoat at the proper time so that you don’t have to sand between coats, usually thumb print time. When you can leave a thumbprint in the paint but the paint doesn’t transfer to your thumb. It is definitely a bugger of a job to do it right but then you shouldn’t have any more blister problems. Good luck and take some Advil.

I've sanded bottom paint off, and I've had it soda blasted off. The soda blasting, with a new barrier coat follow up, is definitely the way to go. I'll never sand bottom paint again.

 

[mvweebles]

HERE is a 1987 USCG report on cause/remediation of boat blisters. It's dry and difficult reading. Below is the summary section. Buried in #11 is likely the root of the issue - I could not find enough brain cells to read the entire report to see if this was adequately addressed.

=================================

Listed below are the major findings of the American Boat Builders and
Repairers Association/University of Rhode Island research project. The reader
is urged to consider the implications only after a thoughtful reading of the
text.

1. Currently used glass reinforced polyester laminates are excellent
materials for boat building, but under some circumstances, can
exhibit blisters.

2. All resins contain some water soluble material (WSM). Only if
that material is concentrated at a point in the hull will it cause
blistering.

3. All blisters are caused by water diffusing into the hull and reacting
with water soluble material to form a droplet of solution which,
because of osmotic pressure, grows in volume and creates a force
which results in a blister.

4. Three types of blisters are discussed. Water soluble material concentration blisters are formed from clusters of materials present
in the hull when the boat is built. Stress induced blisters form
because water soluble material is concentrated by water diffusion
and stresses. Long term blisters form because of ester hydrolysis
of the polyester molecules.

5. Other factors being equal, gel coat thickness determines when
blisters will begin to form.

6. Laminate lay-up and post-cure temperatures did not have a major
effect on initiation time or severity for temperatures between
50°F and 90 0F. Higher temperature post cure should improve
laminate stability. The degree of cross-linking is a critical parameter
in determining the properties of a resin.

7. Design of the resin-rich region between the gel coat and laminate
is important in minimizing blisters.

8. Control -of air inhibition during lay-up can improve blister resistance.

9. Microscopic examination of blisters indicated presence of sawdust, disk cracks, promoter and internal stresses in the blister region.
Without such examination it is impossible to pin point the exact
cause of blistering in a particular boat.

10. Leaching of material from gel coats will cause surface crazing
of the material.

11. The blister initiation time and the severity of the blisters formed
during this study was a function of both the laminating resin and
the gel coat used. However, the area affected by the blisters was
similar in all cases. The size of the blisters depended on the laminating resin used. The chemistry of the materials are complex and
variations were seen among generic types from different
manufacturers.

12. It is recommended that boat manufacturers institute programs
of quality control and quality assurance, with specification for
their supplies, to minimize the blister problem.

 

[CaptBud]

To comply with pollution standards yards are using chemical plasters on bottom painted areas to remove the paint rather than mechanical grinding or sanding. Tenting and face masks are still required for worker safety. The chemical plaster is removed in sheets and properly disposed of. A electric peeling tool is used to remove glass layers without creating clouds of dust.

 

[CaptBud]

Something else that deserves consideration is infusion of water from " inside the boat" i.e. good reason to keep your bilge DRY, water will wick into glass from the inside out as well as outside in. Epoxy barrier coating is an extremely good method of preventing intrusion from outside the hull. We must also remember bottom paint is designed to prevent marine growth not to prevent water intrusion into the hull. Gell coat is porous thus the need to wax.

 

[SoWhat]

Not sure that is correct. I saw some soda blasting this last season in Fairhaven, Mass. at the shipyard there.
They do have to encapsulate the hull to collect all the stuff that comes off, a big part of the cost.
Could be the yard just didn’t want to be troubled by it. Which is strange as this is something that is farmed out because of the specialized equipment.
There is not better way to get the old paint off. Using a belt sander is not a realistic option. (Not that it can’t be done, but it would be like building a house without power tools, possible, but why?)

Boston used to have a soda blast location years ago but EPA requirements shut it down. financially unfeasable. Belt sander was the only realistic option. Not something I would ever do again.

There are several outfits that have mobile blasting setups, and knowing what I know now, I would bring the boat to them.

 

[FoxtrotCharlie]

Yep I've sanded our bottom once - looked like a Smurf for quite a while. At the same time, I did repair about two dozen blisters (30 yr old boat). Marked them at haulout, then ground them out, packed them with baking powder (dries so much faster), and about a month later filled them filler, painted them with barrier coat, then two coats of Miron CSC. None were very deep. That was two yrs ago - still look great.

 

[Group9]

Soda blasting costs will vary by location. I paid $35 per foot about 6 years ago here. I would use the Interlux system. Use all their products, don’t mix and match. Follow their directions to the letter. No shortcuts, they have much more experience than any of us. So when someone says that you don’t need to do a step or do it differently, don’t listen. Interlux has a great support unit and has worked diligently with me in the past. When I had that boat soda blasted I had about an hour ot two of hand sanding to touch it up and get it ready for the epoxy barrier coat, or in your case the blister repair work.

It added $800 to our yard bill for our 42 footer to have it soda blasted last time.

Also a fan of Interlux barrier coats. The 2000e is a great product in my experience with it. I've used it on three different boats.

 

[Slider70]

I had 60 plus blisters on my boat on first pre-purchase inspection, all below the waterline. I got a discount on the already fair asking price. Sanded them by hand, let dry for five weeks or so. Epoxied.

Next haul had far less and all new. Did same as above. Next haul, each at least a year apart, had less than five. Did same. Last haul had zero.

Far as I am concerned it is not a problem to throw too much money at.

 

[wrm95]

To me, blisters the size your talking about are no real problem. Great for a price reduction, but I never fix.

 

[ProMaritime]

If below the waterline on a solid glass layup bottom they are easy to fix, especially small ones.

 

[Steve DAntonio]

The bottom line is it's impossible to give you an objective, and meaningful response without more information about the vessel, and hull laminate, anything more is simply a guess, and you don't want to proceed on a purchase based on multiple guesses of those who have not seen or evaluated the hull, or aren't in a position to do so, albeit with good intentions. Some destructive testing of the laminate, a little grinding and a moisture meter patch test, would yield a trove of useful data. Alas, the seller is unlikely to do that, but it depends on how motivated he or she is to sell.

I've spent much of my 33 year career studying, writing and lecturing about, repairing and preventing osmotic blisters.

There are blisters and there are blisters, if these are in the paint, it's a non-issue (although it probably means the paint needs to be stripped, the bottom epoxy primed, and then re anti-fouled, not a small expense), if they are in the gelcoat, it's a cosmetic but not structural issue (and again not inexpensive to repair), if they are in the laminate it may be a structural issue depending on the number, size and depth and hull thickness, in most cases this is repairable, with a warranty, but it is costly. I've encountered blisters that were the diameter of a grapefruit, and while they may not have sunk the boat, it's impossible to say that level of delamination does not have an effect on laminate stiffness and strength. How much is difficult to say. There's no doubt blisters have an effect on resale value, so even if deemed harmless by an expert, this needs to be taken into account.

With more accurate information, it may very well be worth proceeding.


More on osmosis and blisters here https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Blistology-Pt-1-PMM-Jul_Aug-06.pdf

 

[Jimintheair3]

Considerations

Sorry, I meant to give boat details in initial post, but apparently forgot ... Its a 1980 43' Ocean Alexander Tri-Cabin.

From the feedback so far, and given that the boat otherwise looks like she's been really well maintained, I'm kind of inclined to make an offer, and get a haul-out/survey done and see what we're really dealing with ... still plan to see if I can get more color from Seller / prior surveyor.

A survey without pictures, probably not Nams or Sams. Get a bid for strip at haul out, get a survey consideration for that amount. You will pay for the amount of repair, epoxy, type of paint, how many coats, waterline strip.

I might be more concerned about the 5000 hours on the Perkins.

Color from the seller? In the end, buyers responsibility.

Rocky Point would be my choice and not till next winter.

Good Luck!

 

[Bryant]

blisters

I know blisters have been discussed at length on TF, but wanted to get a gut check. We found a boat we really like and have viewed it 2x. Had a chance to review some prior survey results (from about 2 years ago). Noted a few entries related to the haul-out that have me concerned.

Surveyor noted "many paint blisters" and "several osmotic blisters less than 1/2" in size" (no pics unfortunately). Final note was that the bottom paint should be heavily sanded next renewal.

I'm following up with the seller and also going to see if I can talk to the surveyor that did the survey to get some more color.

So here's the question - assuming this has not been addressed by the Seller and I don't get any more color on the issue, would you proceed forward with an offer and have it inspected and then make a decision based on its current condition, or just keep looking? The boat looks to be in good condition otherwise, but blisters and the "heavy sanding" don't sound good. My more conservative side tells me I may be better off to just keep looking, but would appreciate thoughts on the matter.

Every old boat has blisters. I've had my boat hauled and bottom painted twice in the last 4 years. Both times I had the blisters ground out and repaired before bottom painting. Unless the boat you are looking at is a total train wreck, I wouldn't worry about it. Blister repair isn't very expensive. Do it every time you have the bottom painted and it won't be that big of a deal and you can keep on top of it.

 

[psneeld]

Stick to Steve D's advice, everyone else's is debatable in my book...some just plain ignorant of the subject but I won't point each one out as it isn't necessary if you stick to listening to people in the business...not owners with extremely limited experience.

 

[Sieben]

I know blisters have been discussed at length on TF, but wanted to get a gut check. We found a boat we really like and have viewed it 2x. Had a chance to review some prior survey results (from about 2 years ago). Noted a few entries related to the haul-out that have me concerned.

Surveyor noted "many paint blisters" and "several osmotic blisters less than 1/2" in size" (no pics unfortunately). Final note was that the bottom paint should be heavily sanded next renewal.

I'm following up with the seller and also going to see if I can talk to the surveyor that did the survey to get some more color.

So here's the question - assuming this has not been addressed by the Seller and I don't get any more color on the issue, would you proceed forward with an offer and have it inspected and then make a decision based on its current condition, or just keep looking? The boat looks to be in good condition otherwise, but blisters and the "heavy sanding" don't sound good. My more conservative side tells me I may be better off to just keep looking, but would appreciate thoughts on the matter.

John,

Read up on some of the lastest surveyors in the know who don't care about cosmetic blisters. Resins used in the 80-90's boats get blisters. They are usually the size of a dime to a silver dollar. Some are the size of a pencil eraser. If smaller than a silver dollar ignore them. I had a full peel, all through hulls removed, dried the boat for months. Then had the Interlux epoxy bottom put on something like 12 coats to get the Mill thickness. After $15K, this was 2 decades ago, I still get blisters. If larger than a silver dollar I grind them, fill with epoxy then splash. 10-20 years ago surveyors freaked out over them, as did buyers. Now surveyors have have concluded that they are cosmetic and non structural in the size I'm talking about. There is so much misinformation on blisters that it is crazy. I'm sure I'll get a novel from those who are still in the 1980 to 1990's belief that the hull is going to flake apart. Now if there were blisters and or delamination of a large scale that would be something to look at. My sailboat is 42' 1985. John

 

[RickyD]

Ha - I already need Advil and some whiskey to wash it down. Comodave - you beat me to my question about soda vs. belt sanding. Given my inexperience, I'd probably hire this out first time around and ask the seller for 1/2 as a credit as SoWhat suggests (and SoWhat, great outline of what to do - thx). But to psneeld's point, I'd just fix whatever blisters were there regardless of size.

Follow up question - what's considered the best epoxy barrier?

... And SoWhat - just curious ... you a Miles Davis or Bill Evans fan?

I bought a sail boat with severe bottom osmotic blisters. Like there was not one square foot that did not have a blister. We had the old bottom paint blasted off. We ground off the old gel coat. We ground out the blisters. We bagged it and tagged it, no I mean we put in the dehumidifiers and let it marinate for three months. Then we faired out the blister divits with West System thickend epoxy and sanded smooth. That took a couple tries. Then 8 coats of West System Epoxy. We could apply two coats a day then we would have to sand to roughen it up then two more coats. Ten years later a couple blisters showed up and we treated them locally. Then every time we would haul out we would get a couple. Never a big problem. We had the boat 20 years and it passed survey when I sold her. Paint blisters are no problem.

 

[psneeld]

John,

Read up on some of the lastest surveyors in the know who don't care about cosmetic blisters. Resins used in the 80-90's boats get blisters. They are usually the size of a dime to a silver dollar. Some are the size of a pencil eraser. If smaller than a silver dollar ignore them. I had a full peel, all through hulls removed, dried the boat for months. Then had the Interlux epoxy bottom put on something like 12 coats to get the Mill thickness. After $15K, this was 2 decades ago, I still get blisters. If larger than a silver dollar I grind them, fill with epoxy then splash. 10-20 years ago surveyors freaked out over them, as did buyers. Now surveyors have have concluded that they are cosmetic and non structural in the size I'm talking about. There is so much misinformation on blisters that it is crazy. I'm sure I'll get a novel from those who are still in the 1980 to 1990's belief that the hull is going to flake apart. Now if there were blisters and or delamination of a large scale that would be something to look at. My sailboat is 42' 1985. John

Have any links to studies or names of these latest surveyors (being experts the probably publish)?

I would be very interested in reading new material. I get that newer boats may be a whole new category...but boats pretty 2000 or so I seem to think still suffer old issues.

Before anyone just accepts that blisters are BS...I would go a lot further in my research.

 

[FF]

"Every old boat has blisters."

Nope the resin only got crappy after the" 6 days war " ( 1967 Arab–Israeli War, ) when the price of oil , and therefore products from oil went thru the roof.

GRP boats built before that might have defects from poor workmanship , but seldom from crap resin.

 

[catalinajack]

Ah, a subject to get us all wondering about our boats, again. Steve D's article is quite informative, as usual. I have no idea what type of resin was used to build our boat, ortho or iso. DeFevers do not have cored hulls. I do know that, in seven years of ownership with the boat always in the water, I have never seen a blister. Having been built in 1983, I guess I should not worry.

 

[psneeld]

When buying older designs, one has to be aware that from model to model, year to year, even month to month sometimes boats can differ quite a bit from who built them, how they were built and what materials were used.

https://www.defevercruisers.com/def...st by Miracle Marine,Tania yard, Kaohsuing,%2

In the 1970s, fiberglass became the preferred hull material for boat building. In many of Art's designs, single diesel power gave way to twin engines. He made appropriate modifications, but the characteristic swept sheer, high prow, and displacement hull form were retained. The popular designs of the past quarter century share a distinctive profile, which is a source of pride for owners. The DeFever Passagemaker 34, 40 and 43, the 44 Offshore Cruiser, 49 Raised Pilothouse, 52 Offshore Cruiser, and 60 Offshore Cruiser reflect this DeFever profile that yields excellent sea-keeping capability, interior room and comfort. The Passagemaker 34 and 40 were manufactured at Jensen Marine in California, while the others were built by CTF in Kaohsiung, Taiwan, and more recently, by POCTA in mainland China.

During the mid-80s, the customer’s desire for increased speed led Art to design the 51 POC (Performance Offshore Cruiser). This was followed by the 47 POC, 53 POC and 57 Cockpit POC. All of these boats have simi-displacement hulls for increased speed using larger engines. These were built in the Sen Koh yard, Kaohsiung, Taiwan.

Numerous other DeFever designs continue to grace the waterways of the world. One very popular model among DeFever Cruisers members is the DeFever 41. These were built in the 1980s, first by Miracle Marine Corporation (MMC), and later by Bluewater Yachts, both of Taiwan.

One of his most recent designs is the Grand Alaskan 60, which can be extended to 64 feeet, and is manufactured at the Tania yard, Kaohsuing, Taiwan. These are capable of planing speeds when equipped with larger engines yet cruise comfortably and efficiently at 10 knots.

 

[slowgoesit]

When buying older designs, one has to be aware that from model to model, year to year, even month to month sometimes boats can differ quite a bit from who built them, how they were built and what materials were used.

https://www.defevercruisers.com/def...st by Miracle Marine,Tania yard, Kaohsuing,%2

In the 1970s, fiberglass became the preferred hull material for boat building. In many of Art's designs, single diesel power gave way to twin engines. He made appropriate modifications, but the characteristic swept sheer, high prow, and displacement hull form were retained. The popular designs of the past quarter century share a distinctive profile, which is a source of pride for owners. The DeFever Passagemaker 34, 40 and 43, the 44 Offshore Cruiser, 49 Raised Pilothouse, 52 Offshore Cruiser, and 60 Offshore Cruiser reflect this DeFever profile that yields excellent sea-keeping capability, interior room and comfort. The Passagemaker 34 and 40 were manufactured at Jensen Marine in California, while the others were built by CTF in Kaohsiung, Taiwan, and more recently, by POCTA in mainland China.

During the mid-80s, the customer’s desire for increased speed led Art to design the 51 POC (Performance Offshore Cruiser). This was followed by the 47 POC, 53 POC and 57 Cockpit POC. All of these boats have simi-displacement hulls for increased speed using larger engines. These were built in the Sen Koh yard, Kaohsiung, Taiwan.

Numerous other DeFever designs continue to grace the waterways of the world. One very popular model among DeFever Cruisers members is the DeFever 41. These were built in the 1980s, first by Miracle Marine Corporation (MMC), and later by Bluewater Yachts, both of Taiwan.

One of his most recent designs is the Grand Alaskan 60, which can be extended to 64 feeet, and is manufactured at the Tania yard, Kaohsuing, Taiwan. These are capable of planing speeds when equipped with larger engines yet cruise comfortably and efficiently at 10 knots.

You neglected to mention the Defever 48's!

 

[Capn James Brett]

Art Defever made several with cored hulls, I owned one of them, a Defever 53 POC, great boat and zero blisters. Cored hulls can be great, less weight and just as strong according to Art, one of the legends in boat builiding. So IMO, don't be scared of a cored hull.

 

[psneeld]

You neglected to mention the Defever 48's!

I didn't neglect anything....

The link was from some Defever club or some other maybe reliable source.

I was just pointing out the variations in boats with the same designer, not necessarily the same builder or possible materials.