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Old 01-10-2021, 03:26 PM   #21
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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.
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Old 01-10-2021, 04:09 PM   #22
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OA do not have a blister reputation. 1980 boat with several 1/2” blisters is a total non issue to me and I wouldn’t even touch them. Paint blisters is probably a non issue but a boat that age might have so many coats of bottom paint that it’s starting to have a cottage cheese appearance. If this is the case then let a yard strip it for you. They may choose to grind it or chemically remove but let them deal with all the haz-mat issues.
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Old 01-10-2021, 04:39 PM   #23
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If you really like the boat otherwise, make an offer subject to survey/unfettered insurability, approaching survey willing to walk if you don`t like what is revealed, willing to burn the survey and associated expenses. I did this with my present boat, regarding the purchase as a 50/50 prospect based on the knowledge it had small widespread blisters, and it was interstate as well. None of the blisters were found to be osmosis.
While it`s better to have both the mechanical and general surveyors present together, maybe get the general survey first and hope he does a good job of the things you can only check out of the water, like running gear, rudders, etc.
Miles Davis and Bill Evans have different styles but liking one doesn`t exclude liking the other.
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Old 01-10-2021, 05:24 PM   #24
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I had my 47 done for 200/ft in Louisiana. Haul wash sand blast patch, and 3 coats paint.
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Old 01-10-2021, 05:51 PM   #25
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You should not concern your self about the paint blisters as just heavy sanding or soda blasting then fresh paint would do the trick. the other blisters that are less 1/2 inches are fixable and is not a big deal either. If you really like the boat then concentrate on structural issues or any engine major work.
Good luck
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Old 01-10-2021, 06:11 PM   #26
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At the risk of getting into a spirited debate...
If there are random 15-30 relatively small blisters I would just treat and NOT do a full epoxy job. I did just this on my recently purchase 1976 Hatteras. As pointed out the epoxy vendor is not going to guarantee nor claim this is a cure all. $15-$20k for an epoxy job will pay for periodic blister repairs each time you haul for bottom paint probably for longer than you will own the boat. Getting a seller to cover half or more of an epoxy job for a limited qty of blisters on a 40 year old boat is going to be challenging.
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Old 01-10-2021, 06:27 PM   #27
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Ready,



How many blisters is "Many".

I had Star done 3 years ago, 83 of them ranging from 1/2 to 4"x6". Some of the bigger ones were leaking through the hull. The bill was an unexpected $3800.

My suggestion is to find out how many blisters there are and how big they are. Repairs can be spendy.
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Old 01-10-2021, 06:30 PM   #28
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Thanks again guys - this is truly helpful. I have to say having been a part of many forums (not boating specific), this community is one of the best ... everyone has been so knowledgeable willing to lend a hand. Can't thank everyone enough ... and Bruce, I agree. 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
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Old 01-10-2021, 07:03 PM   #29
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At the risk of getting into a spirited debate...
If there are random 15-30 relatively small blisters I would just treat and NOT do a full epoxy job. I did just this on my recently purchase 1976 Hatteras. As pointed out the epoxy vendor is not going to guarantee nor claim this is a cure all. $15-$20k for an epoxy job will pay for periodic blister repairs each time you haul for bottom paint probably for longer than you will own the boat. Getting a seller to cover half or more of an epoxy job for a limited qty of blisters on a 40 year old boat is going to be challenging.
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Agree
Current boat had about a dozen quarter size blisters when hauled for survey. Negotiated a reasonable allowance from seller (don't remember exactly but <$1000) scraped & left open during winter storage, ground out, rinsed, dried, proxy filled, spot barrier coat in areas of blisters only. No additional issues over 8 yrs of ownership.
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Old 01-10-2021, 08:17 PM   #30
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Thanks again to everyone for giving me some great perspective on the issue. Pleased to say we've got a deal on the boat. Moving to survey and hopefully will go well. Will keep everyone posted! Hoping I can pay it forward soon, but much to learn about this exciting new hobby.

- John
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Old 01-10-2021, 09:31 PM   #31
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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.
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Old 01-10-2021, 09:38 PM   #32
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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.
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Old 01-10-2021, 10:28 PM   #33
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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.
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Old 01-10-2021, 10:38 PM   #34
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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.
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Old 01-10-2021, 11:35 PM   #35
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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.
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Old 01-11-2021, 12:23 AM   #36
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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
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Old 01-11-2021, 09:22 AM   #37
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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?)
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Old 01-11-2021, 09:37 AM   #38
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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.
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Old 01-11-2021, 09:40 AM   #39
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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.
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Old 01-11-2021, 09:42 AM   #40
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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.
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