Blister Repair Options

[bristol24]

Hi all

I’m seeking advise and pro’s/con’s on a couple on blister repair options (or suggestions for other repairs).

I have a 1968 Bristol 24. It’s been in the water for about the last 8-10 years. Pulled it out in December, been drying since.

After 6 weeks, had high moisture readings, then and had an intrusive test done. Results of the test are here, along with some pics of the area tested:









So far I have these options I’ve been considering
1-have the bottom soda blasted (have quote of ~$1300), then me sand/fill/prep and put on an epoxy barrier coat and bottom paint
2-soda blast, clean/fill bottom, sand & prep for epoxy barrier application (~$2500), then me put on an epoxy barrier coat and bottom paint
3-peel, dry, sand, fair/fill, vinyl ester laminate, barrier coat and paint. ~$7500. me doing none of the work.

This boat probably has more sentimental value than actual value, it was my dads boat.

I’m pretty handy at doing things, but I think doing a relamination job myself would be a bit aggressive, and would take some time to do.

So, I’m looking for opinions. I like the sound of option 3 as far as actually repairing damage and having a hull perhaps better than new. But $7500 is a lot of money.

On top of this, I’m replacing the seacocks (3) as well (pretty corroded), I have the cost of that as well (doing most of that work myself).

My goals are
-back in the water May or early June
-best tradeoff point of benefit vs cost

Thanks!

[kenJ]

Your time or your money, your choice. The prep work is the hard/dirty part, painting is easy, waiting for it to dry can get tedious. I'd go with option 2. If you will need new thru hulls with the new seacocks, get them out before the soda blast, so any damage can be repaired at the same time.

[Pericles]

Search these sites for advice.

http://www.yachtsurvey.com/blisters.htm

http://www.hotvac.com/

http://www.yachtsurveys.co.uk/faq_osmosis.htm

Good luck,

Pericles

[MrYan]

I would have it blasted but wait a while to enure proper drying then refinish with epoxy etc and bottom paint

[Landlubber]

bristol 24,

Firstly, if money is a problem, do the following, if not just pay for the work

May I suggest that you strip the bottom off with a 16 grit 8" orbital sander and a soft pad attached, hold the disc flat to the hull at all times, it will rip off the gelcoat at a rapid rate of knots. Be gentle doing this and do not remove all the gelcoat, leave a wisker of colour on there. This last bit is to help the fairing process. After the gelcoat is removed, then go over it once more to fair the bottom back in, this time removing the last wiskers of gelcoat.

Pull all skin fittings before doing any of this work and replace them with new ones later.

If there are bubble type blisters, as in hard boiled eggs shape, then grind them out individually, about twice the size of the bubble and then reglass these hollows with csm and poly resin. sand smooth with the disc sander again.

Next you put on two or three layers of solventless epoxy clear resin, done with a roller. This will achieve about 250 to 300 microns of good clear substrate. Do not oversand this, but lightly abrade, with say 120 paper, use frecut aluminium oxide, then apply two or three coats of epoxy primer, such as interprotect. The first coat is white followed by two grey. Do not go past the white layer, it is going to be your guide. Sand fair then apply another two coats, you may be finished now if the job was sanded well in the first place.

Apply two coats of antifouling, three around the leading and trailing edges and the weatherline, and sit back and enjoy her for many more years to come.

[MrYan]

This is a complete and proper resolution to the job in hand.I totally agree it can be done this way.As you say Landlubber if money is not a problem though...just pay to have the job done.Incidently I actually use sand for the blasting as opposed to soda.I have done this repair many times in NZ on Cavalier yachts that seemed to have problems with gelcoat blisters.I vaguely remember doing a Westsail 42 the same way.Used Hitech 9000 when it first became available.

[captword]

blisterd bottom,
how we repair a moderate to severe blistered bottom.
1.) blast the bottom, get the person blasting to try n open all blisters.
2.) after blasting is done. take a four inch grinder open any unopened blisters and clean all the edges of the blisters.
3.) let boat sit to dry to four to 12 weeks depending the moisture content.
4.) deep blisters depending on depth get filled with epoxy n cloth or epoxy and mat. Rule of thumb on that is wider than halh inch or deeper than an eigth get some form of clothe. Fill the rest of the shallow blisters n pin holes with thickened epoxy.
5.) light sand on whole bottom, nessecary sand of blister patched areas, to fairness. put more thickened epoxy to any areas required, sand.
6.) we roll two coats of epoxy with barrier coat additive to fill in any unseen pinholes and cracks. sanding any bubbles or grit in epoxy between coats.
7.) the epoxy barrier cote primer that your desired botom paint requires.

if you peel the gelcote off you need to put a layer of mat on the bottom of the boat to maitain hull thickness and and integrity b4 you begin the fairng process. Peeling the gel off cuts into the clothe in some places more than others and also will find any posibble bobbles during the the layup process on your hull. Are the blisters bad enough and in a quantity that requires peeling? Has the yard owner given any indication that he thinks you should peel?


this is how i was taught to repair a blistered bottom, keep asking around and get other oppinions. some may disagree with how i do it.

Captword

ps i had a boat that stayed in a covered shed for four months after sand blasting. the five unopened blisters that i didnt see still had water in them

[Landlubber]

One more thing, to help the boat to "dry out", after the bottom is ground off, wash it with fresh water for a few days, evert time it dries out wash it again. This will help remove undesirable salts that are still holding hands there. You can cook the hull quite easily by drapping a plastic sheet from the boot topping and placing heaters underneath the gage of plastic, it works well. It will not be possible to remove all the moisture from the laminate mate, so do not loose sleep over it.

[bntii]

......

[Landlubber]

bntii,

I almost could not be bothered replying to your comments, however in the interestes of users to the forum, I feel that i need to express some concerns regarding your post.

My comments were my comments, what I believed to be a reasonable solution to a problem. It is surely not the only way the problem could be attacked, but it was a reasonable solution. To state that we must :

"What you don't want to hear:

-Forget site repairs to the 'blisters'
-Forget 'drying' the laminate
-Forget grinding/blasting"

I find this entirely unreasonable.

Many of your comments are quite correct, it may just have been the manner in which it is written, but many repairs on boats are done to keep them alive for as long as possible for as little as possible. I have used the technique described above for over 30 years on frp blister repairs, and it has proven to be successful. It is very economical, relatively fast to achieve, the end result looks quite acceptable and the boat is back into service again for many years to come.

[bntii]

Fair enough.

......

[Landlubber]

Thanks bntii, no worries, as I stated, I do agree with what you are saying, if a job is worth doing, it is worth doing properly.

[Herman]

One smalll remark to be made:

Normal CSM has binders on them. Either emulsion, or powder binders. It is these binders that sometimes create problems. (although the main problem is the polyester, containing salts)

Combination mats (1708 etc) use binderless mats, only using stitching to keep the fibres together.

On the other hand, when combination mats are needed to beef up the structure, a lot of material has been peeled away in the beginning...

Second, the stitching in the combination mats are not completely to be trusted as well.

So if possible, only use woven roving or fabric when beefing up the structure. Use a good quality resin (either vinylester or epoxy) after peeling away the bad layers.

some yards have a robotic peeler. results are nice, and there is no worker complaining about a sore back, and "white finger syndrome" due to the vibration.

[dcstrng]

Hi Bristol – I’ve been wrestling with a similar situation although with a lot less technical analysis so I’m kinda watching over your shoulder to see how you tackle this… My B24 sat at an unattended mooring for around 4 years, and when we pulled her last fall we spotted several blisters – along with all sorts of stuff, from wasps to you name it…

We let it dry over the winter, and then ground out as many blisters as we could find or anything that looked/sounded fishy… but all told only about 9-10 actual blisters (and all pretty small, localized…). Did find one area of delamination about 18 inches forward from of the rudder near the bottom of the keel and had to grind out all the way, and about 4” across, to get to sound glass (had delaminated all the way to the ballast – ours is one of the later, iron -- and whatever -- ballasted ones), and I think an open sump had formed down behind the ballast…

So far all I’ve used is epoxy/silica paste (WEST) except for the delaminated area where I’ve reglassed to (I think) seven thicknesses in three applications… but am going to watch very closely at haul-out next fall and may have to strip and apply some sort of barrier coat if there is a more systemic problem than what I’ve seen so far…

I don’t mind the sweat equity, sorta fun on this little rascal and a piece of cake compared to larger previous boats, but don’t want to over-improve the neighborhood too badly either… so I’m watching…

Larry