Author Topic: Osmotic Blisters  (Read 7038 times)

0 Members and 1 Guest are viewing this topic.

Offline Plugcheck

  • Donate members
  • Hero Member
  • *****
  • Posts: 3267
Osmotic Blisters
« on: March 15, 2018, 08:47:09 AM »
      Sometimes called "Hull Pox" by some when the issue becomes more advanced.   I had a few on the last two Glastrons I owned, but those were rather miniscule compared to this project.   I decided to break this topic away from the thread "Timi Time" which documents the rebuild of my 1985 Intimidator as it deserves a bit of light all on its own.   First off, a disclaimer, I'm not a professional boat restorer, just a DIY'r that isn't afraid to get my hands dirty.   Not having a business, customers, and schedule deadlines allows me to give a bit extra care and to take my time.   This boat had a black ablative coating on its hull, it likely spent the boating season in the water instead of being trailered primarily.   Once thought that fiberglass and gel coat finishes were impervious and nearly bulletproof, later gave way to the fact that gel coat is rather porous.   The hull when stored in water eventually allowed water to pass through the gel and into voids left by the manufacturing process.  Once there, it reacted with the resin to break it down and convert it to a more viscous goo.   This modified glycol/acid mixture is now molecularly larger, and therefore cannot follow the path out that the water came in through. The result is pressure which creates the blister.  Pressure builds until the gel coat "pops"   This now allows the cell respiration with the outside water and the process continues.   In some cases, the process will actually delaminate the layers and create a hull leak.   Here is what I'm doing, and most of what I'm doing comes straight from research on the internet.   There is a wealth of info to be found there, but take some of it with a grain of salt.  From the research, and actually working on the issue, I've come to the plan that follows.   To start, the boat is upside down, I suppose it could be done from the bottom as well, its just easier this way since I'm in the midst of a full restoration.  I washed, then used a wax degreaser product on the hull to remove any grease or wax.  I then sanded the entire hull with 80 grit to remove the ablative coating and some of the light scuffing/scratches.  Now the hull was clean and bare white gel coat exposed, I went around with a permanent marker and visually circled all the defects, cracks, splits, etc.     The blisters had drained out their water long ago since this boat hasn't been in water for at least three years.  With sanding they were now smooth, possibly making identification a bit more difficult, maybe next time I'll clean and grind first but only if an ablative coating is present that hides the issue.   You can use a sharp point like an awl or screwdriver and press on the crack, it will likely flex a little indicating a void underneath.  Once identified, I started attacking with a 4" angle grinder.  It works, but not ideal by any means, takes more material than it needs to, and make a fine aerosol dust that lands everywhere in the shop.  Instead I grabbed my angle die grinder and chucked up a bull nose carbide cutter.   Turn the air pressure down a bit, really doesn't need to turn real fast.  I found it did an excellent job, make larger particles that were easily swept up, and allowed for grinding out only the area with the damage. You could do the same with a dremel or drill with a similar bit.  As you grind, you can see the void that the water once occupied.  In most cases a yellowish to brown residue is present.   This needs to be ground out until solid laminate is reached.   Once all the blisters are opened, a good hot water bath, just plain water, is used along with a mild scrubbing with a brush.  The residue left in the blisters will actually pull moisture from the air.  This bathing allows the water to bring the residues out so they can be safely washed away.  I washed it twice just to be sure.  Really wanted to hotsey the bottom, but that is rather difficult when its below freezing outside, so 5 gallon pails will suffice.     Allow a day to fully dry and you can then go about filling and finishing the hull.   Some folks may opt for plastic filler, duraglass, peanut butter, or equivalent, but I decided to use an epoxy fairing compound instead given the magnitude of the blister issue.  The critical decision is whether the product you use is waterproof, structurally compatible, and will bond well to the original components of the hull.  A fourth consideration is will it be compatible with what you coat it with.  Epoxy fairing is the only material I found that would fit all this criteria.  After filling and sanding, a barrier coating will then be applied.  I selected Interlux 2000e interprotect for this task.   4-5 coats, then followed by Interlux VC performance Epoxy.   Timing is critical for proper bonding, so I may finish the barrier coat on a Saturday, then add the final layer Interprotect on a Sunday followed by the hull paint.
1st picture is the identified blister which appears like a fine hair line on the surface of the gel coat.  2nd photo is just beginning to grind at the crack.  It shows the void area below the crack.  3rd photo is further grinding, and it shows that I have not opened up the entire void yet.  4th pic is the blister fully ground out.   The gel coat is bonded well at the edges, and the scallops left by the carbide will really help the epoxy get a good bite.
       You'll likely notice the concentration of the blisters occurs on the lifting strakes or chines if you will.   I believe this is because when the original fiberglass materials make a corner is where many of the voids in construction occur.   On the big flat areas, its possible, and easier, for the cloth, biax, roving, to lay down and prevent trapped pockets. Water can get into a scratch or gouge in the hull on the flat areas, but if it cannot spread out it doesn't appear to cause much harm.   Long term will show if this is the best method of blister repair, but I'm confidant that it will be a permanent repair given the boat will rarely see more than several days in the water at a time, spending most of its time being trailered.  Hopefully I've not missed too much, feel free to comment on your experiences if you have encountered this issue before.
« Last Edit: March 15, 2018, 09:01:17 AM by Plugcheck »
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline Plugcheck

  • Donate members
  • Hero Member
  • *****
  • Posts: 3267
Re: Osmotic Blisters
« Reply #1 on: March 15, 2018, 08:54:59 AM »
A few more pictures related to the hull pox.  The first picture is a crack that had been opened by grinding and shows the discolored residue left behind.   This will have to be ground further and washed before filling.   2nd picture is the Starboard side showing the extent of the issue and the hull hook present near the outer strake. The last two are just more pictures of the hull bottom showing all the blisters opened up, and cleaned out.
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline RedOctober89

  • Sr. Member
  • ****
  • Posts: 154
Re: Osmotic Blisters
« Reply #2 on: March 15, 2018, 09:17:56 AM »
Great write up! Very good information and documentation!
Andrew C.
1989 Glastron Carlson 23 CSS 350 Mag - Red October
Follow the project on Instagram: redoctober89

Online Hyperacme

  • Administrator
  • Hero Member
  • *****
  • Posts: 13462
Re: Osmotic Blisters
« Reply #3 on: March 15, 2018, 09:51:13 AM »
You've done some research Mike !

Edit ...
Just read your Timi time post ...
You had bottom paint.
« Last Edit: March 15, 2018, 09:55:07 AM by Hyperacme »

Offline Plugcheck

  • Donate members
  • Hero Member
  • *****
  • Posts: 3267
Re: Osmotic Blisters
« Reply #4 on: March 15, 2018, 09:58:46 AM »
       Nope, the ablative coating is the antifouling paint applied to keep the "Barnacles" off the hull when stored in water.   It sheds itself releasing an agent that keeps the hull clean.  Of little use on trailered boats, they benefit with harder coatings and regular cleaning.   If you look closely in the pictures, you can see the haze of the former black antifouling paint on the flaked area of the hull.   Otherwise, the thread titled "Timi Time" has a picture of the hull with only one side stripped, the other remains with the ablative coating. 
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Online Hyperacme

  • Administrator
  • Hero Member
  • *****
  • Posts: 13462
Re: Osmotic Blisters
« Reply #5 on: March 21, 2018, 08:59:31 AM »
Mike
Could you put this in the "Vendor and Repair Resources " section ?
I can do it if you want.
Great info that will get lost in this section.

Offline Plugcheck

  • Donate members
  • Hero Member
  • *****
  • Posts: 3267
Re: Osmotic Blisters
« Reply #6 on: March 21, 2018, 10:26:28 AM »
I'm not sure how to move the topic, but ok with it being moved.  I'm a bit surprised this wasn't commented on more, but I suppose it's a problem that is more prevalent in boats that spend substantial time in water, whereas most of our boats are day trippers.  Have not seen many Glastrons with ablative bottom paint either.
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline dorelse

  • Administrator
  • Hero Member
  • *****
  • Posts: 5987
Re: Osmotic Blisters
« Reply #7 on: March 21, 2018, 11:24:48 AM »
Mike
Could you put this in the "Vendor and Repair Resources " section ?
I can do it if you want.
Great info that will get lost in this section.

Non-Admin's can't move topics...
1990 Sierra 1700

Offline carlsoncvx18

  • Donate members
  • Hero Member
  • *****
  • Posts: 1588
Re: Osmotic Blisters
« Reply #8 on: March 21, 2018, 12:06:40 PM »
Looks like it was a boat built on Friday and everybody was ready to go home.

If I remember correctly from the workshop we went to a shipwreck they indicated the first coat that was put down was not rolled all the way in and air pockets like you said.

The also said that there could be areas the harder was not correct and the area never cured when the next layer was put down. Resulting in a none cured area of resin.
1987 CVX18.     1968 Glastron alpha sail boat
1977 GT150
1986 CV23
1984 Intimiadator
1981 CV27
1969 V-180 fundeck

Online Hyperacme

  • Administrator
  • Hero Member
  • *****
  • Posts: 13462
Re: Osmotic Blisters
« Reply #9 on: March 21, 2018, 01:04:17 PM »
OK .. I'll just copy and paste it.

Offline Plugcheck

  • Donate members
  • Hero Member
  • *****
  • Posts: 3267
Re: Osmotic Blisters
« Reply #10 on: March 21, 2018, 03:15:36 PM »
Looks like it was a boat built on Friday and everybody was ready to go home.

If I remember correctly from the workshop we went to a shipwreck they indicated the first coat that was put down was not rolled all the way in and air pockets like you said.

The also said that there could be areas the harder was not correct and the area never cured when the next layer was put down. Resulting in a none cured area of resin.
        Could be a Friday boat as you suggested.  Since very few anomolies occurred in the flat areas, but rather accumulated at the sharp bends of the strakes, it may be simply  the fabric doesn't contour well in corners.  Regardless of the possible construction issues that may be present, when a fiberglass boat is left in water for extended periods, some form of blisters will likely appear.  Bottom line, gel coats and polyester laminating resins are not water proof as was once considered. 
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline fireman24mn

  • Hero Member
  • *****
  • Posts: 2060
Re: Osmotic Blisters
« Reply #11 on: March 21, 2018, 07:11:51 PM »
I just learned all about this topic today for 2 hours in class.

Let me know if you have other question. Looks like you have a pretty good idea what needs to be done already.
I think this has become an addiction.


1977 CV-23 I/O Full Resto complete
1976 CV-16 V8 Resto in progress
1985 Pearson MotorYacht 43ft

Offline Plugcheck

  • Donate members
  • Hero Member
  • *****
  • Posts: 3267
Re: Osmotic Blisters
« Reply #12 on: March 22, 2018, 07:42:03 AM »
     I read quite a number of articles that seemed to indicate a review by a marine surveyor would be necessary.   So it comes as no surprise that your education in this field would include a study on hull blisters.  If you have any further info or product knowledge feel free to post your advice.  The Interlux products I selected to cure the issue are effective, but rather expensive.   The fairing compound, barrier coat, and performance coating ate the better part of $500.00.    Most of this cost may be because they are designed for watercraft that spend their lives in water.  Given that I spend only a small amount of time in water, its likely I'll never see a blister again on the Timi. 
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline Rich_V174SS

  • Hero Member
  • *****
  • Posts: 2074
  • 1967 V174 Crestflite SuperSport Modified
Re: Osmotic Blisters
« Reply #13 on: March 22, 2018, 10:08:50 AM »
When I worked for a Larson dealer 10 years we sold a new 18 foot runabout and within just a couple weeks the whole bottom of the hull was blistered. The customer trailered the boat so the bottom was unpainted but I'm not sure if they left the boat in for any great length of time. Still, for a new boat to become blistered in such a short amount of time from new was unusual. The boat was replaced by Larson because it would have required too much work to repair.
1967 V174 Crestflite SuperSport Modified
1987 Mercruiser 190 3.7LX/Alpha One

1970 V176 Swinger
1983 Mercury 115

Offline Plugcheck

  • Donate members
  • Hero Member
  • *****
  • Posts: 3267
Re: Osmotic Blisters
« Reply #14 on: March 22, 2018, 01:31:51 PM »
     That does seem like a very short period of time for the blisters to occur, poor resin and gelcoat layup possibly?    As for the labor to correct, it is a lot of work, more than most would sign up for, but its a classic Glastron and I'm too far in to give up now.
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Online Hyperacme

  • Administrator
  • Hero Member
  • *****
  • Posts: 13462
Re: Osmotic Blisters
« Reply #15 on: March 22, 2018, 01:39:12 PM »
Rich ... That wasn't a VEC hull was it ?

Say's something about our cool old boats ...
Throw away a new $30000 boat because it not worth fixing.
Put about $10000 worth of time and money into a boat worth fixing ...
« Last Edit: March 23, 2018, 08:27:37 AM by Hyperacme »

Offline Rich_V174SS

  • Hero Member
  • *****
  • Posts: 2074
  • 1967 V174 Crestflite SuperSport Modified
Re: Osmotic Blisters
« Reply #16 on: March 22, 2018, 02:34:26 PM »
Rich ... That wasn't a VEC hull was it ?

I think it was. It was the early 2000's before Larson stopped production in 2005.
1967 V174 Crestflite SuperSport Modified
1987 Mercruiser 190 3.7LX/Alpha One

1970 V176 Swinger
1983 Mercury 115

Offline fireman24mn

  • Hero Member
  • *****
  • Posts: 2060
Re: Osmotic Blisters
« Reply #17 on: March 26, 2018, 09:14:48 PM »
Here is the docs that I received in class the other day about blisters. More pics then any thing.
I think this has become an addiction.


1977 CV-23 I/O Full Resto complete
1976 CV-16 V8 Resto in progress
1985 Pearson MotorYacht 43ft

Offline Plugcheck

  • Donate members
  • Hero Member
  • *****
  • Posts: 3267
Re: Osmotic Blisters
« Reply #18 on: March 26, 2018, 09:57:22 PM »
Maybe Greg or Doran can put that doc in the vendor resouces area as well.  Thanks for sharing.
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Online Hyperacme

  • Administrator
  • Hero Member
  • *****
  • Posts: 13462
Re: Osmotic Blisters
« Reply #19 on: March 27, 2018, 10:06:19 AM »
Done ...
Also added link to this thread.

« Last Edit: March 27, 2018, 10:08:00 AM by Hyperacme »