SailNet Community banner
1 - 17 of 17 Posts

·
Registered
Joined
·
50 Posts
Discussion Starter · #1 ·
Hey guys, my 1979 Ontario 28 has developed some quarter sized blisters on her port underbelly. I have found that most of my leaks and standing water problems on the boat have been on this side, is that where the problem lies? Or is in the cheaping out with resins in the late 70's on these boats? I have fixed most of the scupper and through hul problems, now to the hull, how do you decide when to fix the blistering ? How do you fix it ? take the gelcoats off, interprotect then bottom paint ?

Any help is appreciated.

NB there are only 20-30 blisters at present....

Mike
 

·
Registered
Joined
·
3,184 Posts
The first thing to check is the nature of the blisters, by grinding one or two down. Sometimes you get blisters in the paint, caused by poor adhesion at one of the layers - these are not true blisters, and nothing to worry about. Usually caused by the yard applying paint in less-than-ideal conditions (too damp, not enough/too much time between coats, etc).

For 20-30 true blisters, I woudn't be taking all the gel coat off. Grind them down, epoxy, then interprotect the whole bottom, then bottom paint. Will probably have to repeat this every few years.
 

·
Registered
Joined
·
145 Posts
I stopped counting at 300 blisters on a previous 1981 Catalina 25. I wouldn't remove the gel coat. I used a carbon steel counter sink drill bit to open all the blisters.

West System has excellent and inexpensive literature on this very topic. Followed their instructions and used their products and achieved professional results. Make sure you have "peanut butter" consistency with the filler. I applied "mayonnaise" consistency and the filler sagged :(.

Applied 5 coats of Interlux System 2000 water barrier + VC17.

If I had to do it again I would do the exact same thing (except for the sagging filler!) ;)

Good luck and post some pix!
 

·
One of None
Hunter 34
Joined
·
8,630 Posts
Use their colloidal silica additive. I use it wherever I want epoxy to stay put while it's setting.
BUT! it's like grinding IRON .. a softer mix for the final fairing is suggested. I like to use silica for the filling.. and fairing filler (tan color) on top of the silica
 

·
Registered
Joined
·
129 Posts
I just ground out the blisters. Mostly in the gelcoat and outer layer of mat. I think I want to pre-seal each ground blister site with epoxy before applying the epoxy filler to better seal the glass. Has anyone done this? What are your thoughts about the need to do this? Has anyone compared the West and Mas systems to see which is better, i.e. ease of use, pot life, sagging potential, ease of sanding, etc?
 

·
Registered
Joined
·
7,864 Posts
I would grind out the blisters and fill with thickened epoxy as posted. I would use silica and if you are careful there will not be much to sand.

I would not barrier coat the entire hull unless it is proven to be dry. Use a moisture meter with a base line from the topsides. A good drying takes many months.
 

·
Registered
Joined
·
129 Posts
Shinook and Mitiempo, thank you for the quick responses. I liked how
Watertite sounded, but was put off by manufacturer's statement that it must be covered with Interprotect. Doesn't make sense to me, but that is what they said. I don't think I am going to barrier coat this time. Boat is new to me and have no idea what the blistering history is. Prior owner said it had been in fresh water for 7-10 years without hauling out. There are many blisters but not big.

Either of you pre-treat the ground-out blister with thin epoxy before filling? If this is a good idea, I want to use an epoxy that doesn't require washing or sanding to save some effort. Any ideas on brands?

I am good on drying time. Boat will be out of water for 6 months before filling, etc.
 

·
One of None
Hunter 34
Joined
·
8,630 Posts
Shinook and Mitiempo, thank you for the quick responses. I liked how
Watertite sounded, but was put off by manufacturer's statement that it must be covered with Interprotect. Doesn't make sense to me, but that is what they said. I don't think I am going to barrier coat this time. Boat is new to me and have no idea what the blistering history is. Prior owner said it had been in fresh water for 7-10 years without hauling out. There are many blisters but not big.

Either of you pre-treat the ground-out blister with thin epoxy before filling? If this is a good idea, I want to use an epoxy that doesn't require washing or sanding to save some effort. Any ideas on brands?

I am good on drying time. Boat will be out of water for 6 months before filling, etc.
All epoxy makes a "blush" only way to not get it is to add the next layer or coat before it's totally cured. No you don't have to coat the whole bottom but the parts you fix witll be more water proof then the rest of the bottom.

West sytem is the best IMHO they wrote the "book"

Make your putty only when you are ready to use it. the coating in the hole should be at least tacky but not dry and hard to the touch.

Mix the putty in small batches too. less waste that way. Don't try to fill in one shot and then grind off.. fill low then add.. just like doing drywall.
 

·
Registered
Joined
·
129 Posts
DeniseO30, thank you for the input. I was wondering about the blush. Mas Epoxy says their's doesn't but...

If I apply the filler in layers, will I have to sand in between or can I apply when the first layer is tacky? I think that is what you are saying but not sure.
 

·
Registered
Joined
·
5,072 Posts
Go here for a COMPREHENSIVE intro & remediation on 'blisters'. Hull Blisters on Boats and Yachts - by David Pascoe, Marine Surveyor

The salient facts are that most blisters and their repair is usually nothing but expensive 'hype' and that more boats have been totally destroyed / rendered unsaleable through BAD blister repair.
If these are only down into the Gelcoat - consider to ignore them until you have the available time and $$$ to do the job 'right'; only when blisters penetrate down into the structural FRG 'roving' are blister a 'problem'.
 

·
One of None
Hunter 34
Joined
·
8,630 Posts
DeniseO30, thank you for the input. I was wondering about the blush. Mas Epoxy says their's doesn't but...

If I apply the filler in layers, will I have to sand in between or can I apply when the first layer is tacky? I think that is what you are saying but not sure.
you have to wash and sand only when it's completely cured. while tacky is best. in hot weather though.. you need to plan and move fast to very quick even with slow hardeners. Remember, if you use only silica as filler it will be very very hard to sand off.
 

·
Registered
Joined
·
129 Posts
RichH, I have read Pascoe's stuff. However, thanks for the lead.

I have the time and money to do the work now. The boat is blocked in a yard and can stay there as long as needed. Since I have already ground out the blisters, I am pretty much committed at this point to filling them. Accordingly, I am trying to to ascertain just how to do it "right" as you and Pascoe emphasize.

SVVelocir's you tube videos seem to point to three good potential products. As I will invest a fair amount of time on this, I would like to maximize the benefit. Do you have experience with the products Velocir discusses (Watertite, Vinyl Ester, West Epoxy) and which do you prefer?
 

·
Registered
Joined
·
129 Posts
DeniseO30, thanks for responding again with the clarification. I will just have to plan on taking the time to wash and sand as I am not a fast worker.

I like your idea about mixing fillers. I know what you mean about how hard the epoxy can get. I assume, but am not sure, that the Watertite product (which is epoxy) has been formulated to do exactly what you are suggesting, as it is reported to be easily sandable.

Thanks again.
 

·
Registered
Joined
·
5,072 Posts
Good, one of the pro's secrets of blister repair is to do this as a single continuous process so that various 'layers' of repair do not cure totally before the next 'layer' of laminate or barrier remediation is applied. Thats the way modern high quality hulls and high quality technical/industrial/chemical service FRG laminates are seemingly now being built, including 'refrigeration' of the hull, etc. during hand lay-up - continuous process to produce a 'single cure'.
 
1 - 17 of 17 Posts
Top