Tiny Blisters

[Jack Sparrow]

We purchased our in 06 and had read about blistering on this forum so we decided not to take the risk as we had had a stink boat many years before that blistered . We epoxy painted the bottom up to the black water line mark then anti fouled over it no more worrying

Jack Sparrow

[DaveB]

Jack, good move...tho if you want to sell your boat one may question the epoxy. Any person that has experance with leaving boats on a Mooring or slip knows a epoxy barrier coat is needed with Polyester Gelcoat, exception is with Boats that use epoxy final coat, and those boats are at the very high end construction.
Salt water is more pron to blistering the further you go in souther Latitude, fresh water lakes can also produce blistering but at a lower rate than salt water.
I have done many repairs both major and minor in repairing Osmosis blistering, a CP16 I cut large holes in the hull to take out concrete ballast and reglassed the intire hull with Layup cloth and epoxy and refilled ballest with 3/8 stone and resin . Concrete was saturated with water crumbling to pieces and causeing the osmosis from inside of hull.
Just one example of saturation and detearation of fiberglass laminites.
My new to me 1997 Max. I bought with hull original (no bottom coat) and noticed 2 areas of stress cracks that are minor and easy to repair but if bottom painted I would have never known, why when looking for a boat I wanted no bottom paint.
Dave

We purchased our in 06 and had read about blistering on this forum so we decided not to take the risk as we had had a stink boat many years before that blistered . We epoxy painted the bottom up to the black water line mark then anti fouled over it no more worrying

Jack Sparrow

[magnetic]

DaveB - I'm sorry to appear openly confrontational, but other than your spot-on observation about the inverse relationship between Latitude and the probability of osmosis, I think that most of what you are saying is ill-informed and in some cases just plain wrong.

The fundamental point is that osmosis is not caused by - and does not require - immersion in liquid water; it takes place at the molecular level within the structure of the fibreglass, where it doesn't produce "wet" or saturated patches, but causes the leaching out and gradual breakdown of chemical substances (e.g. styrenes and residual mould release agents) within the substrate. The result is a blister typically filled with liquid containing an acetic acid solution; this is not the cause of the problem, it is the result of it, and it weakens the hull more because of an increased brittleness than due any observable soggyness. Decayed GRP looks like bone material, not like cooked pasta.

Quite separately from the chemical processes going on within the GRP, there are a variety of mechanical factors which can either start or accelerate osmosis. These include star cracking and physical breaches in the gelcoat, or more frequently wicking or poor wetting out of the laminate during the layup. The fundamental point is that it's not just the rovings which are potentially hygroscopic as the gelcoat is itself to some extent porous. The only real question is whether this is a gradually operating process or a more aggressive situation caused either by poor production techniques, or by the physical degradation of the outer hull due to age or abrasion leading to the emergence of pinhole air inclusions and cracks which expose the underlying laminate.

[bastonjock]

whan i bought my boat last year,it came with antifouling and it had been epoxied,as im new to boats,i often wondered what the epoxy managed to achieve.

i have a few light scratches on the hull,so it would be wise to pollish/repair these asap?

i did not think that having the boat on a trailer sitting in my garden,would allow any osmosis to happen.

so therefore,is it a good idea to reapply the epoxy?

i have all the paint spraying equipment at my disposal

[Moe]

Epoxy barrier paint is applied to the bottom in several very thin coats and the anti-fouling paint is applied over it. The epoxy barrier paint stops, or at least significantly slows, osmosis of water through the gel coat into the fiberglass. Anti-fouling paint doesn't do that.

[magnetic]

Absolutely right - interestingly, if you come to fill any holes etc in the gelcoat, you put the first coat of epoxy primer on BEFORE you fill the cavity, rather than after - take a look at

http://www.yachtpaint.com/superyacht/sy ... 202004.pdf

for a really thorough review of how to apply epoxy coatings:

3. Apply the first coat of Gelshield 200 by the chosen method.

4. After an appropriate drying period (refer to the datasheet), apply any filler that is required. For small areas Watertite epoxy filler can be used. This is a faster curing filler suited to small repair areas. Interfill 830 is most appropriate for larger areas as it has a longer working time and is easier to sand once it is cured.

5. After any filler application, wipe down with solvent and a clean cloth as before.

6. Apply subsequent coats of Gelshield 200 by the chosen method

[DaveB]

40 yrs experance in gelcoat osmosis and restructing osmosis repair from my 1963 built Alberg 35 thru 1997 Mac. (personal experance)
My guess is you should research the area for the past 60 yrs in polyester resin and how products have changed over the years and then do a search especially during the mid 1970's and early 80's how the product was changed because of oil prices .
I have repaired many boats from blistering in many diffrent years and Know fully well how they develop, how long it's been doing it and how much it has penitrated the layup.
I don't need your advice since I have first hand experance thruout the years.
Dave.
PS, I am also a FL. State and most other States Certified Structural Inspector amoung many other have to have Lic.
I am guessing your either a retired Politician or a Civel Engineer with no practical experance.

DaveB - I'm sorry to appear openly confrontational, but other than your spot-on observation about the inverse relationship between Latitude and the probability of osmosis, I think that most of what you are saying is ill-informed and in some cases just plain wrong.

The fundamental point is that osmosis is not caused by - and does not require - immersion in liquid water; it takes place at the molecular level within the structure of the fibreglass, where it doesn't produce "wet" or saturated patches, but causes the leaching out and gradual breakdown of chemical substances (e.g. styrenes and residual mould release agents) within the substrate. The result is a blister typically filled with liquid containing an acetic acid solution; this is not the cause of the problem, it is the result of it, and it weakens the hull more because of an increased brittleness than due any observable soggyness. Decayed GRP looks like bone material, not like cooked pasta.

Quite separately from the chemical processes going on within the GRP, there are a variety of mechanical factors which can either start or accelerate osmosis. These include star cracking and physical breaches in the gelcoat, or more frequently wicking or poor wetting out of the laminate during the layup. The fundamental point is that it's not just the rovings which are potentially hygroscopic as the gelcoat is itself to some extent porous. The only real question is whether this is a gradually operating process or a more aggressive situation caused either by poor production techniques, or by the physical degradation of the outer hull due to age or abrasion leading to the emergence of pinhole air inclusions and cracks which expose the underlying laminate.

[richandlori]

Unless the purchaser is intent on selling, there is no loss, methinks.

When you guys who bought used bought your boats, did you ever wonder what was under the bottom paint? What if you had known the boat had blistered - would that have impacted your offering price?

Good question Sps..

Here's a photo of the Bottom of THIRD DAY when we bought a little over two years ago now.

[I'm looking for it....hold on a minute]

There were about 45 blisters the size of a dime to a quarter. For $1500 they were grinded out (took the yard all of 20 minutes with a grinder), filled in with epoxy, sanded and then the entire old bottom was sanded to remove the ablative paint and apply new paint. When I hauled the boat last august, there wasn't a single sign of a blister and I just sanded the old ablative paint off and applied 4 new coasts.

The seller of the boat deducted 1/2 the cost of blister repair and that was that, but a surveyor did tell me the hull was in good shape. Many people overpanic about blisters IMHO.

[Catigale]

I think so too Rich

Especially true for the trailer sailor, light duty boats that are not slipped.

The tendency for sailors to think that everything has to be built for a Fastnet race is rampant, I find. There is an awful lot of enemy fire of the flavour "Better is the enemy of good enough" in the sailing world.

[magnetic]

Well, DaveB, I am neither a politician nor without experience - and neither for that matter can I rival your standards of illiteracy and ignorance. I am also sure that your dog is much bigger than mine and that you can pee much further up the wall than I can.

But surely, friend, the point is this - I wasn't trying to give you advice - why would I bother, as you clearly already know it all; I was simply trying to point the original poster (Bill Earnhardt) in the right direction, and whilst the grandees of southern Florida might bow to your superior wisdom, the rest of us can generally learn a thing or two by following the links to International Paint etc which I posted in my messages.

Be a good boy, go get a life, k?

[bastonjock]

so then guys,to repair the one tiny little stone chip on my hull,i should use epoxy filler?

[kmclemore]

so then guys,to repair the one tiny little stone chip on my hull,i should use epoxy filler?

Yep, that will work great.

[Jimnkathy]

I am in the middle of openeing up many blisters in my hull mostly at the waterline. I am using a countersink bit to open them up it works perfect it keeps you from drilling to deep and gives plenty of surface area for the epoxy to adhere to.I am planning on using west system epoxy to fill the blisters after they dry. I am not sure if I should use the barrier coat additive in the west sys epoxy and coat my complete hull or should I use Intereprotect 2000? My other question is do I need to put bottom paint over the epoxy or interprotect 2000? I trailer my boat and I dont keep it in the water for more than 1.5 days at a time.

If I need bottom paint what is a good paint for a trailered boat? I am on a budget keep that in mind.

Thanks
Jim

[richandlori]

If I need bottom paint what is a good paint for a trailered boat? I am on a budget keep that in mind.

Thanks
Jim

Jim...if you only plan on leaving your boat in the water for 1-2 days at a time, I'm not sure you even need bottom paint in the first place, because you are allowing it to dry out often. If you do go with a bottom paint, the two choices are:
1. Hard 2. Ablative

The hard will need to be sanded off between coats while the ablative is designed to slowly come off as you use the boat. The question then becomes how will the ablative paint hold up sitting on the trailer. Also, some bottom paints are made to get wet and STAY wet, so taking the boat out of the water and letting it dry out will negatively affect the paints life and affectiveness. Hmmm....lots of issues to figure out, my first choice would be to not aply bottom paint and save the headache!

[bastonjock]

i managed to pick up an araldite epoxy kit at the weekend,its got the resin,the hardener and some white powder called silica?

i have the tinyest of chips but i can see the fiberglass,the rest of the hull below the water line has been antifouled and epoxied since new,so i want to keep the hulls integrity

dont know what materials macgregor uk use for antifouling but my hull has no signs of either hard or soft fouling