To soda blast or not?

[Sofa King Fishy]

I’m literally in the same boat! Although a sailboat. I also work in the Marine Industry…here’s what I know: Nothing beats a Soda/Walnut blast to remove old paint. If it’s built up to the point of peeling off, sanding will take forever, the cost of pads will be very high, the chances of hull damage are great, and most yards prohibit open air sanding, so, that’s out.

My local yard does soda on sight- it’s a very nice, full service Marina. Most marinas utilize a mobile blasting service. The cost is $40-70 per foot. More for larger vessels, as they have great surface area to cover.

If you’re not interested in maintaining the vessel for the long term, you can continue to coat with paint & go cruise. It’s not going to hurt anything, it’ll just be less efficient- you’ll go slower, burn more fuel & your engine will work harder.

It’s not a question of an equal alternative - there isn’t one- it’s a question of how much money yiu want to spend, and how long you foresee using the boat.

 

[EngNate]

Well, tomorrow I am painting my bottom which I have just freed of 20 or so years of buildup with 1" and 1-3/4" scrapers. It was a mountain. Adjusting for a start with the wrong tool, it was easily 7 full days of work, plus another sanding and washing. Good part, though, scraping doesn't hurt the gel cote. It's something to consider if the only reason for the new barrier coat is because of the stripping process. The hard parts were where I had previously scraped over the years where it had been falling off. Heavily built up paint will come off faster with a scraper than a sander, and the chips are much less messy than dust. I used the 'Richard' brand hooked blade scrapers - and a half dozen or more replacement blades. It was tough work but for 2 or 3K I would do it again. It's very important for speed to keep the blade ground sharp, straight and square. I kept a mini bench grinder right at hand, with a nice new wheel on it.

 

[yarradeen]

Greetings

Doing the same thing 14 years of bottom paint removed. Ready for 4x barrier coat, tie coat then new antifoul.

PPG Sigmacover 280 and 555 for barrier. Ecofleet 290 antifowl.

Costs about $100 a foot for blasting.

Y

 

[ronobrien]

Would love to get some advice for the group. We have adhesion issues according to the yard and they are recommending soda blast then epoxy primer and paint. I trust his recommendations but not sure if it makes sense to spend the money (a little over 4K for 30ft) now, or just sand and paint (1800) and have the bottom cleaned as needed. Oh, yard requires we buy paint from them if we decide to paint it ourselves, so we may just have them do all the work.

Our plan is to cruise this winter for 5 or 6 months, then either haul out for a couple of years on dry storage, or sell. Thoughts?

I just had the bottom of my GB36 glass bead blasted last week. It is my intention to epoxy coat it for protection against water intrusion. The surprise was that a PO had epoxy coated it sometime in the past. The last owner had the boat for 20 years, and the epoxy was done before him. (I bought it last November). 99% of the epoxy stayed on despite the blasting, so it is tenacious stuff. The hull was dry and in remarkable condition. I plan to touch up and re-coat the epoxy. It was recommended that I then apply a hard coat and finally ablative coat(s). It was also recommended to allow the hull to remain exposed to the air for as long as possible to ensure that as much moisture (if any) comes out before resealing it. I went through the boat yard for the sub contracting, it was $3600 for a 36' boat.

 

[psneeld]

One thing I discovered both through my own boat and research....hulls rarely dry out on their own by just sitting. Especially if the gel or any epoxy is not removed.

Most boaters, surveyors and yards don't believe this, but it is there if you research enough from the most experienced sources I could find.

 

[Gdavid]

One thing I discovered both through my own boat and research....hulls rarely dry out on their own by just sitting. Especially if the gel or any epoxy is not removed.

Most boaters, surveyors and yards don't believe this, but it is there if you research enough from the most experienced sources I could find.

I think the topic of drying a hull out with regard to this original post is mostly mute as FF's advice is really sound for a boat the owner is considering selling soon. I was also assuming $4k to be the cost of the blasting alone, which is not the case, as the OP clarified.

I agree that moisture will not escape through epoxy but it can escape though gelcoat which is quite porous, basically as porous as the polyester resin that is is comprised of. I don't think a boat with blisters that have already formed will dry out on their own, that they really need to be ground out and repaired, but prior to blisters forming, moisture does accumulate and you want to give this a chance to leave the hull before sealing it in with epoxy. I like to help it along by periodically wiping it down with acetone.

In addition to working in a boat yard, I've talked extensively with various subcontractors who come in and do the removal. Techniques have changed over the years, everything from using planers and various media blasting methods. I've seen successful repairs and unsuccessful jobs too and my personal conclusion is that you need to remove all moisture you can see mechanically and allow time for the moisture you can't see to evaporate which takes time and a dry environment.

I will also admit that if a 20-30 year old boat has not experienced blisters by this point, it is highly unlikely to start now but you don't always know how a boat was used in the past, a boat hauled and stored on the hard annually is less likely to experience blisters.

 

[Steve DAntonio]

Isn't a barrier coat depending on the resin that was used to build the boat? To my knowledge polyester/vinylester resins are permeable to water, epoxy is not so the later one does not require a barrier coat. Am I out of my mind?

L

Vinylester (VE) resins are non-permeable if a minimum of three coats/laminates, or 1/10" is used. Polyester is permeable and prone to blisters.

A epoxy barrier coat, in order to be a barrier, requires a minimum thickness, which depends on the manufacturer, in order to work effectively as a moisture barrier (assuming the laminate isn't already wet too). If it's being used only as a primer, because the bottom is already VE, then it doesn't require that thickness to work as a primer and thus fewer coats can be used. Again, all dependent on manufacturer. Don't rely on the yard, you should read the application instructions, especially the part about anti-foulant application windows. More here https://www.proboat.com/2015/08/antifouling-tactics/ and here https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Blisters-and-Osmosis.pdf

Soda, slurry or other media (but not sand or black beauty it's too aggressive) blasting are effective, preferred and relatively gentle ways of removing anti-fouling paint.

 

[Mako]

It was recommended that I then apply a hard coat and finally ablative coat(s).

Interesting idea.

 

[rslifkin]

Interesting idea.

In my mind, if you're going to do the different color indicator coat thing, it makes sense to use a hard paint for that first coat, then go ablative on top of it. That way you add more ablative as needed, but in spots where you wear down to the indicator coat, you won't start to wear through that.

 

[Steve DAntonio]

I think the topic of drying a hull out with regard to this original post is mostly mute as FF's advice is really sound for a boat the owner is considering selling soon. I was also assuming $4k to be the cost of the blasting alone, which is not the case, as the OP clarified.

I agree that moisture will not escape through epoxy but it can escape though gelcoat which is quite porous, basically as porous as the polyester resin that is is comprised of. I don't think a boat with blisters that have already formed will dry out on their own, that they really need to be ground out and repaired, but prior to blisters forming, moisture does accumulate and you want to give this a chance to leave the hull before sealing it in with epoxy. I like to help it along by periodically wiping it down with acetone.

In addition to working in a boat yard, I've talked extensively with various subcontractors who come in and do the removal. Techniques have changed over the years, everything from using planers and various media blasting methods. I've seen successful repairs and unsuccessful jobs too and my personal conclusion is that you need to remove all moisture you can see mechanically and allow time for the moisture you can't see to evaporate which takes time and a dry environment.

I will also admit that if a 20-30 year old boat has not experienced blisters by this point, it is highly unlikely to start now but you don't always know how a boat was used in the past, a boat hauled and stored on the hard annually is less likely to experience blisters.

While it is a frustratingly common, and long-held belief, among boat owners and industry professionals alike, there is no scientific evidence to support the practice of drying a wet laminate as a long term solution to osmotic blistering. In my 30+ year professional experience, including 11 of which that managing a yard that specialized in osmosis repair, and for which we provided a 10 year warranty, I have never seen a hull that was dried out and blisters spot repaired, remain blister free for years. That's not to say that less costly approach can't be used, it's just not one that offers a long-term solution. The only guaranteed long term solution is peeling and relaminating. For those who question this, find a reputable osmosis repair contractor who offers a long term warranty on hull drying.

More detail here https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Blistology-Pt-1-PMM-Jul_Aug-06.pdf

 

[psneeld]

While it is a frustratingly common, and long-held belief, among boat owners and industry professionals alike, there is no scientific evidence to support the practice of drying a wet laminate as a long term solution to osmotic blistering. In my 30+ year professional experience, including 11 of which that managing a yard that specialized in osmosis repair, and for which we provided a 10 year warranty, I have never seen a hull that was dried out and blisters spot repaired, remain blister free for years. That's not to say that less costly approach can't be used, it's just not one that offers a long-term solution. The only guaranteed long term solution is peeling and relaminating. For those who question this, find a reputable osmosis repair contractor who offers a long term warranty on hull drying.

More detail here https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Blistology-Pt-1-PMM-Jul_Aug-06.pdf

Thank you... after nearly a year of research and having one of those "almost terminal hulls"...would have been had I not done the repair myself...... finding out what the tiny core of people who really understood the whole wet hull, hydrolysis, blistering, and possible repair routes was eye opening how little I knew and seemingly the industry knew.


I found gobs of info on the underground tank and pipe industry problems with underground glass tanks and piping who have a host of similar concerns. They matched up to the tiny core of boating industry people who worked extensively with wet hulls, not the typical yard, boat owner or magazine writer.

 

[PaintMeRetired]

Hard to beat soda blasting. If you decide to keep the boat have it blasted when you block it for storage and the hull will have 2 years to dry out. Polyester and vinyl-ester resins do absorb a measurable amount of water and allowing them to dry will enhance the adhesion of epoxy barrier coats when you get ready to launch again.

 

[GingerMd]

As a new to me owner of a 97 Camano 31, there were more layers of old paint that I could count. I figured I’d save weight from removing it all ! Lol jk. I had it soda blasted out of pure laziness. Just to much work in my old age *50s. I find myself writing more checks and enjoying other things lol. Plan to have it barrier coated in the spring, so I will be starting fresh and know where I am.

 

[Steve DAntonio]

Fiberglass does not "dry out". It has been proven time and again, allowing a bottom to "dry" will not prevent formation of new blisters. This was proven by USCG sponsored University of Rhode Island study in the 90s. And yet, the myth of bottom drying has permeated so deeply into the marine industry that it persists to this day, much to my frustration.

Does any yard that "dries" bottoms and then barrier coats offer a warranty against blister reformation? Not to my knowledge. Peeling and relaminating a bottom is the only way to ensure blisters do not reform. I took that approach and offered a 10 year warranty.

No harm in allowing a bottom to "dry", just don't expect it to be a long-lasting solution to osmotic blisters.

More details here https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Blistology-Pt-1-PMM-Jul_Aug-06.pdf

 

[ronobrien]

Fiberglass does not "dry out". It has been proven time and again, allowing a bottom to "dry" will not prevent formation of new blisters. This was proven by USCG sponsored University of Rhode Island study in the 90s. And yet, the myth of bottom drying has permeated so deeply into the marine industry that it persists to this day, much to my frustration.

Does any yard that "dries" bottoms and then barrier coats offer a warranty against blister reformation? Not to my knowledge. Peeling and relaminating a bottom is the only way to ensure blisters do not reform. I took that approach and offered a 10 year warranty.

No harm in allowing a bottom to "dry", just don't expect it to be a long-lasting solution to osmotic blisters.

More details here https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Blistology-Pt-1-PMM-Jul_Aug-06.pdf

It is my understanding that the blisters do not come from moisture but from improperly cured resins. Polyester resins are hydro-scopic and can absorb moisture, The guy who glass bead blasted my hull a couple months ago stated that he has seen water running from the hull of some boats, but again that is not the cause of the blisters. My hull was in excellent condition, probably because it was epoxy coated some time in it's early life. There are many conflicting information sources.

 

[Steve DAntonio]

It is my understanding that the blisters do not come from moisture but from improperly cured resins. Polyester resins are hydro-scopic and can absorb moisture, The guy who glass bead blasted my hull a couple months ago stated that he has seen water running from the hull of some boats, but again that is not the cause of the blisters. My hull was in excellent condition, probably because it was epoxy coated some time in it's early life. There are many conflicting information sources.

I don't doubt you heard this, but this is just more dockside lore and myth on a subject that is immersed in it.

Most blisters are formed when water that enters the resin matrix encounters and interacts with water soluble materials or WSMs. WSM's are often binding agents that are used to hold glass fabric together until it is impregnated with resin. Through osmosis, the interaction attracts more water, which causes pressure, which in turn causes the blister to form. The liquid in the blister (what your blaster may have seen running from hulls) is not water, it is glycol and acetic acid (it smells like vinegar), which do not evaporate at room temperature and normal atmospheric pressure, and this is why "drying" does not work. These chemicals are also not readily registered by a moisture meter, which is calibrated for water. This is all explained in the article I shared.

Water can penetrate polyester resin, it is hygroscopic (it's hygro not hydro btw, a common misspelling), which is why nearly all osmotic blisters occur on poly hulled vessels. Vinylester and epoxy are far more resistant to water penetration, and thus nearly blister-proof. However, if that's true, then why don't all poly bottom vessels get blisters, one might ask? It's a function of the presence of WSMs, if they aren't present, there's no reaction. I've measured high moisture on poly bottoms, but no blisters. Moisture does not necessarily lead to osmotic blisters, however, when blisters are present water nearly also is as well.

Yes, you can get non-osmotic blisters, particularly above the waterline, that are the result of over catalyzation (a chopper gun dripping MEKP catalyst as its being used), contamination from dust and other causes. Below the WL blisters are nearly always osmotic in nature.

You are right, there are many conflicting information sources where osmotic blisters are concerned, and most are misinformation.

 

[ronobrien]

I don't doubt you heard this, but this is just more dockside lore and myth on a subject that is immersed in it.

Most blisters are formed when water that enters the resin matrix encounters and interacts with water soluble materials or WSMs. WSM's are often binding agents that are used to hold glass fabric together until it is impregnated with resin. Through osmosis, the interaction attracts more water, which causes pressure, which in turn causes the blister to form. The liquid in the blister (what your blaster may have seen running from hulls) is not water, it is glycol and acetic acid (it smells like vinegar), which do not evaporate at room temperature and normal atmospheric pressure, and this is why "drying" does not work. These chemicals are also not readily registered by a moisture meter, which is calibrated for water. This is all explained in the article I shared.

Water can penetrate polyester resin, it is hygroscopic (it's hygro not hydro btw, a common misspelling), which is why nearly all osmotic blisters occur on poly hulled vessels. Vinylester and epoxy are far more resistant to water penetration, and thus nearly blister-proof. However, if that's true, then why don't all poly bottom vessels get blisters, one might ask? It's a function of the presence of WSMs, if they aren't present, there's no reaction. I've measured high moisture on poly bottoms, but no blisters. Moisture does not necessarily lead to osmotic blisters, however, when blisters are present water nearly also is as well.

Yes, you can get non-osmotic blisters, particularly above the waterline, that are the result of over catalyzation (a chopper gun dripping MEKP catalyst as its being used), contamination from dust and other causes. Below the WL blisters are nearly always osmotic in nature.

You are right, there are many conflicting information sources where osmotic blisters are concerned, and most are misinformation.

Thanks for the clarification. I love good technical information.

 

[Bill V]

I bought my present boat in 2005 and had 27 years of bottom paint soda blasted off. They then applied a barrier coat, then a primer coat followed by a coat of red hard bottom paint and finally 3 coats of dark blue ablative paint. Cost back then was $4200, a lot of "boat bucks" at the time. The purpose of the red hard bottom paint was to act as a "flag" to show that the blue ablative had "worn" through and needed to be repainted. This past winter I had 2 coats of ablative applied after having the bottom sanded to clean it well. Going 15+ years on the original ablative seems money well spent now.

 

[Mako]

@Bill if you can figure out how to get 15 years out of bottom paint here in Florida, then I'll be your best friend!

BTW, what you did is exactly what I learned during my days as a contractor - to tint the primer a different color from the top coat for exterior paint (usually trim) so you can see when it is fading or printing through.

 

[PaintMeRetired]

Steve gave an excellent technical description for blisters caused by water-soluble materials and he’s dead-on as it being the cause of some of the blistering in a hull. It happens with numerous resin families, not just polyester/vinylester. Often, improper mix ratios or insufficient mixing of materials create localized areas of WSM’s. In these cases, some of the residue will not evaporate at ambient temperatures and needs to be removed by other methods once the blister has been opened. I’ve seen osmotic blisters in all common resins (PE, VE, epoxy, aromatic polyurethane, phenolic, etc) whether they are filament reinforced or not. For true osmosis to take place it is essential to have a semi-permeable membrane, a solvent (water, etc) on one side and a soluble compound on the opposite side. The osmotic pressure gradient across (through) the membrane is proportional to the difference in molecular polarity of the solvent and the soluble material. Water is a powerful and plentiful solvent that is attracted to a multitude of chemicals used in resins with unreacted styrene, glycol and several weak acids being a few of them with sufficient polarity to establish an osmotic cell. It’s a real problem but fortunately there are simple solutions.

However, I have to add something to this discussion. A sub-surface “void” within a composite like PE or VE reinforced with filaments of glass, aramid, carbon or other materials will also give rise to a blister. On boat hulls being laid up by hand in a mold there are prolific opportunities for reinforcing materials to be missed during the rolling and “wet-out” work. These dry voids provide a location for water vapor to condense after it permeates the outer resin surface. These blisters are not purely osmotic but are rooted in the brute force of condensation. Formation of these blisters is accelerated by temperature change and seasonal differences are more than adequate to set up the needed imbalance inside the void and outside of it. The appearance of a condensation blister will differ from a chemically-driven osmotic one. Osmotic blisters are fairly symmetrical with a height approaching the diameter and mostly round. They will contain a liquid that is only partially water (or other solvent) and the soluble material. Condensation blisters are typically flatter, larger and often irregular in shape and profile. They will often appear dry but do have small amounts of exceptionally pure water in them because the overlying resin film acts as a molecular-level filter. It requires a disciplined procedure to collect the condensate without contamination followed by some basic laboratory analysis. In other cases where temperature cycling is more extreme they can be completely filled with pure solvent (usually water). I had several dozen of these on my previous boat and they are easily opened and filled with an epoxy fairing material. I especially like Pettit’s Splash Zone putty for this work because it’s moisture tolerant.

Modern boat manufacturing is using vacuum infusion because it reduces resin use, results in a better resin/glass ratio - and - virtually eliminates dry fibers being trapped within the composite. Hand layup is essential for some stages or steps of hull and deck construction but vacuum infusion of the primary hull will radically reduce the severity and scope of blistering.

 

[Steve DAntonio]

Steve gave an excellent technical description for blisters caused by water-soluble materials and he’s dead-on as it being the cause of some of the blistering in a hull. It happens with numerous resin families, not just polyester/vinylester. Often, improper mix ratios or insufficient mixing of materials create localized areas of WSM’s. In these cases, some of the residue will not evaporate at ambient temperatures and needs to be removed by other methods once the blister has been opened. I’ve seen osmotic blisters in all common resins (PE, VE, epoxy, aromatic polyurethane, phenolic, etc) whether they are filament reinforced or not. For true osmosis to take place it is essential to have a semi-permeable membrane, a solvent (water, etc) on one side and a soluble compound on the opposite side. The osmotic pressure gradient across (through) the membrane is proportional to the difference in molecular polarity of the solvent and the soluble material. Water is a powerful and plentiful solvent that is attracted to a multitude of chemicals used in resins with unreacted styrene, glycol and several weak acids being a few of them with sufficient polarity to establish an osmotic cell. It’s a real problem but fortunately there are simple solutions.

However, I have to add something to this discussion. A sub-surface “void” within a composite like PE or VE reinforced with filaments of glass, aramid, carbon or other materials will also give rise to a blister. On boat hulls being laid up by hand in a mold there are prolific opportunities for reinforcing materials to be missed during the rolling and “wet-out” work. These dry voids provide a location for water vapor to condense after it permeates the outer resin surface. These blisters are not purely osmotic but are rooted in the brute force of condensation. Formation of these blisters is accelerated by temperature change and seasonal differences are more than adequate to set up the needed imbalance inside the void and outside of it. The appearance of a condensation blister will differ from a chemically-driven osmotic one. Osmotic blisters are fairly symmetrical with a height approaching the diameter and mostly round. They will contain a liquid that is only partially water (or other solvent) and the soluble material. Condensation blisters are typically flatter, larger and often irregular in shape and profile. They will often appear dry but do have small amounts of exceptionally pure water in them because the overlying resin film acts as a molecular-level filter. It requires a disciplined procedure to collect the condensate without contamination followed by some basic laboratory analysis. In other cases where temperature cycling is more extreme they can be completely filled with pure solvent (usually water). I had several dozen of these on my previous boat and they are easily opened and filled with an epoxy fairing material. I especially like Pettit’s Splash Zone putty for this work because it’s moisture tolerant.

Modern boat manufacturing is using vacuum infusion because it reduces resin use, results in a better resin/glass ratio - and - virtually eliminates dry fibers being trapped within the composite. Hand layup is essential for some stages or steps of hull and deck construction but vacuum infusion of the primary hull will radically reduce the severity and scope of blistering.

Well-said and agreed on all counts. Topside blisters are not uncommon, I have three clients with them right now on vessels that are a year or less old, all hand laid by a very high end builder.

Resin infusion is very slick, has all of the advantages you offered and then some, and it can avoid many of these issues, however, it too is not fool proof. I have encountered infused hulls with dry fabric where air leaked into the membrane, and other cases where resin pooled, leading to incorrect resin to glass ratios. It's also expensive, and so most builders are still relying on hand lay up, which if done correctly can be very good. For lighter, planing vessels, resin infusion is especially worthwhile.

Grand Banks/Palm Beach infuse, using vinylester resin, hulls, decks and other large parts, and then post cure, they are light, strong and stiff and the factory is among the cleanest I've ever worked in, with very little styrene odor. Again, costly but in that case worth it for a light, fast vessel.

 

[ronobrien]

Steve, I am restoring my new to me 1973 GB36 Classic. Part of the project is to seal off all the thru-hulls and install a single sea-cock. Do you think polyester/mat/cloth is appropriate for this repair? Or should I use epoxy, or another material? If you are in a position to answer that would be great, if you are not I understand.
Thanks,
Ron O'Brien

 

[Steve DAntonio]

Steve gave an excellent technical description for blisters caused by water-soluble materials and he’s dead-on as it being the cause of some of the blistering in a hull. It happens with numerous resin families, not just polyester/vinylester. Often, improper mix ratios or insufficient mixing of materials create localized areas of WSM’s. In these cases, some of the residue will not evaporate at ambient temperatures and needs to be removed by other methods once the blister has been opened. I’ve seen osmotic blisters in all common resins (PE, VE, epoxy, aromatic polyurethane, phenolic, etc) whether they are filament reinforced or not. For true osmosis to take place it is essential to have a semi-permeable membrane, a solvent (water, etc) on one side and a soluble compound on the opposite side. The osmotic pressure gradient across (through) the membrane is proportional to the difference in molecular polarity of the solvent and the soluble material. Water is a powerful and plentiful solvent that is attracted to a multitude of chemicals used in resins with unreacted styrene, glycol and several weak acids being a few of them with sufficient polarity to establish an osmotic cell. It’s a real problem but fortunately there are simple solutions.

However, I have to add something to this discussion. A sub-surface “void” within a composite like PE or VE reinforced with filaments of glass, aramid, carbon or other materials will also give rise to a blister. On boat hulls being laid up by hand in a mold there are prolific opportunities for reinforcing materials to be missed during the rolling and “wet-out” work. These dry voids provide a location for water vapor to condense after it permeates the outer resin surface. These blisters are not purely osmotic but are rooted in the brute force of condensation. Formation of these blisters is accelerated by temperature change and seasonal differences are more than adequate to set up the needed imbalance inside the void and outside of it. The appearance of a condensation blister will differ from a chemically-driven osmotic one. Osmotic blisters are fairly symmetrical with a height approaching the diameter and mostly round. They will contain a liquid that is only partially water (or other solvent) and the soluble material. Condensation blisters are typically flatter, larger and often irregular in shape and profile. They will often appear dry but do have small amounts of exceptionally pure water in them because the overlying resin film acts as a molecular-level filter. It requires a disciplined procedure to collect the condensate without contamination followed by some basic laboratory analysis. In other cases where temperature cycling is more extreme they can be completely filled with pure solvent (usually water). I had several dozen of these on my previous boat and they are easily opened and filled with an epoxy fairing material. I especially like Pettit’s Splash Zone putty for this work because it’s moisture tolerant.

Modern boat manufacturing is using vacuum infusion because it reduces resin use, results in a better resin/glass ratio - and - virtually eliminates dry fibers being trapped within the composite. Hand layup is essential for some stages or steps of hull and deck construction but vacuum infusion of the primary hull will radically reduce the severity and scope of blistering.

I'm in full agreement, and well-said. I know of three vessels, 50+ feet, all less than 2 years old, built by a well-respected high end manufacturer, all of which have above the WL blisters numbering a few dozen. I had a case a year ago of a year old 70+ foot vessel, also built by a well-respected manufacturer, which ultimately developed hundreds of above the WL blisters. It does happen.

Resin infusion has all the benefits you mentioned and then some. It remains the exception, however. It's expensive and mistakes are even more expensive. I've encountered "dry" laminates, fabric that was not wet out with resin where air leaked into the membrane, on infused vessels. Generally, however, for those who know how to do it, it makes for a strong, light, stiff structure with ideal resin to glass ratios; it's especially valuable on light, planing vessels. Grand Banks/Palm Beach is one example, they use vinyl ester resin throughout and infuse hulls and decks, and post cure, and do a good job of it, the factory is among the cleanest I've ever worked in, with little styrene odor. Because it is in a tropical environment, resin, glass and core is stored in climate controlled conditions until it's ready to be used, many builders in tropical regions do not take this step. It's also a dust free shop. Contamination from dust and moisture is, in my experience, a significant cause of laminate failures.

Some of my images from the Grand Banks yard...

 

[Steve DAntonio]

Steve, I am restoring my new to me 1973 GB36 Classic. Part of the project is to seal off all the thru-hulls and install a single sea-cock. Do you think polyester/mat/cloth is appropriate for this repair? Or should I use epoxy, or another material? If you are in a position to answer that would be great, if you are not I understand.
Thanks,
Ron O'Brien

In short, I would never dream of doing this. The magnitude of properly glassing over holes like this, taking into account the required scarf ratio, should not be underestimated, and these will be secondary bonds, which are not as reliable as a primary bond, and not as reliable as a proper, high quality seacock. More on secondary bonds here https://www.cruisingworld.com/story/how-to/fiberglass-repairs/
See attached as well.

Failures of well-maintained seacocks are very rare,, and failures of well-maintained, capped, disused seacocks are even more rare.

Switching to a single intake has benefits and drawbacks. Benefits include one rather than many holes in the bottom, drawbacks include...one hole in the bottom, if it clogs you lose water to everything. Also, with a single intake hose runs to various components requiring seawater become much longer, which is a liability.

 

[mvweebles]

.....Switching to a single intake has benefits and drawbacks. Benefits include one rather than many holes in the bottom, drawbacks include...one hole in the bottom, if it clogs you lose water to everything. Also, with a single intake hose runs to various components requiring seawater become much longer, which is a liability.

I have considered going to a large single intake thru-hull to replace multiple small thru-hulls, though not to reduce the number of holes in the bottom. As Steve D states, failure of a properly installed seacock is rare. What I do like about an oversized manifold approach is it allows a single large sea strainer in an accessible location to replace the various small seacocks (often with no sea strainer) hidden in cabinets throughout the boat. As Mark Twain famously said "Put all your eggs in one basket.....but watch the basket." In a perfect world, my preference would be a nice sea chest such as those built into many Defever trawlers.

As a note, I believe most engine manufacturers require a dedicated intake so running off a manifold would likely void any warranty.

Groco makes a slick manifold fitting to be placed on a sea strainer. If you read carefully, they actually do not recommend using it, but built it anyway ("We do not recommend the practice of supplying raw or filtered water to multiple “consumers” from a single inlet source" ).

https://www.groco.net/products/fittings/manifolds/raw-water-manifold

Peter

 

[ronobrien]

In short, I would never dream of doing this. The magnitude of properly glassing over holes like this, taking into account the required scarf ratio, should not be underestimated, and these will be secondary bonds, which are not as reliable as a primary bond, and not as reliable as a proper, high quality seacock. More on secondary bonds here https://www.cruisingworld.com/story/how-to/fiberglass-repairs/
See attached as well.

Failures of well-maintained seacocks are very rare,, and failures of well-maintained, capped, disused seacocks are even more rare.

Switching to a single intake has benefits and drawbacks. Benefits include one rather than many holes in the bottom, drawbacks include...one hole in the bottom, if it clogs you lose water to everything. Also, with a single intake hose runs to various components requiring seawater become much longer, which is a liability.

OK Thanks. My bigger question is the type of resin i intended to use. As that was my bigger question I didn't bother to mention that my intention is have (2) 1"1/2 seacocks in the bilge bay, for the very reason you note, that being if one is clogged I would still have intake through the other. They would both feed a common manifold. My concern with multiple seacocks is not the seacock itself, but the associated hoses and clamps failing. I have a seacock the services the forward day head which I still have not gotten to from the interior of the boat. I feel that two that are readily available in one location would help me sleep better at night.

 

[Steve DAntonio]

"We do not recommend the practice of supplying raw or filtered water to multiple “consumers” from a single inlet source"

Doing so would mean they sell fewer seacocks, but I agree;-)

Seriously, this device would add leverage to the seacock, likely leading it down a path of ABYC non-compliance re. the 500 lb 30 second rule.

Once again, getting the necessary scarf ratio required for a safe secondary bond means a lot of grinding, so be prepared. I still strongly recommend against it, it would be easier to close those seacocks when not in use if your concern is a failed hose. If you use SAEJ2006 hose and sold band all stainless clamps, a failure would be very unlikely. Put the effort and $ into that, and perhaps adding a texting high water alarm like a Siren.

 

[Comodave]

I have glassed old through hull fittings. I do a 12 to 1 scarf and only use epoxy resin. I have done 7 or 8 and never had a problem yet. But I am very careful to get the scarf correctly done and am very careful with the glassing.

 

[Steve DAntonio]

Just to be clear, this is a secondary bond, and these are used for repairs on a regular basis. But repairs are necessary, glassing unused seacocks isn't.

A scarf ratio of 12:1 means if the hull is 1/2" thick you need to grind a bevel that is 6" wide all around the hole, so essentially 12" across plus the diameter of the hole, so maybe 13-14" across in some cases. Then you are laying pre-cut fabric into this depression in successively larger diameters to fill it, and wetting out. It's no small task.

The time when secondary bonds are tested are when they are stressed, rather than in every day use, this includes groundings, striking an object, and when being hauled and blocked.

 

[rslifkin]

Personally, I'd consider glassing over and moving any seacocks that aren't readily accessible. But for any that are, I'd keep them in place rather than adding more hose on the inside to manifold everything.