How often should you paint your bottom? I understand that boats in warmer temperatures need painging more often than those in cooler waters. I am in warm waters in Biloxi, how often should I paint my bottom? What does this have to do with blistering? ajp
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Check with the Locals
This issue is highly localized both in terms of how often and what type of paint works best. You should check with other owners in your location. It is also highly dependent on how you use your boat and how often you have your bottom clean (or clean it yourself). If you're going to race,you will most likely want to do it annually.
This issue is highly localized both in terms of how often and what type of paint works best. You should check with other owners in your location. It is also highly dependent on how you use your boat and how often you have your bottom clean (or clean it yourself). If you're going to race,you will most likely want to do it annually.
Bottom coatings
Bottom Coatings: Anti-Fouling Paints are intended to prevent or reduce the growth of biological fouling organisms (barnacles, seaweed, slime, etc.); and do little to protect the bottom from long-term damage (blistering). Barrier-Coats are (nearly) impermeable coatings, often epoxy, that are intended to protect the bottom from the water intrusion. Gelcoat surfaces are somewhat permeable, and will, over time, allow water to enter the laminate (if not barrier-coated), resulting in eventual blistering. There is no universal “magic” formula for determining how often to re-paint your anti-fouling; but 1.5 to 2 years is the often cited frequency for sub-tropical waters (presumes propper preparation & application). Although I prefer annual bottom painting, I’ve gone as long as 2.5 years in S. Florida & Bahamas. As with any painted surface, your eye will tell you when it’s time to repaint.
Bottom Coatings: Anti-Fouling Paints are intended to prevent or reduce the growth of biological fouling organisms (barnacles, seaweed, slime, etc.); and do little to protect the bottom from long-term damage (blistering). Barrier-Coats are (nearly) impermeable coatings, often epoxy, that are intended to protect the bottom from the water intrusion. Gelcoat surfaces are somewhat permeable, and will, over time, allow water to enter the laminate (if not barrier-coated), resulting in eventual blistering. There is no universal “magic” formula for determining how often to re-paint your anti-fouling; but 1.5 to 2 years is the often cited frequency for sub-tropical waters (presumes propper preparation & application). Although I prefer annual bottom painting, I’ve gone as long as 2.5 years in S. Florida & Bahamas. As with any painted surface, your eye will tell you when it’s time to repaint.
Painting your bottom . . .
I would recommend painting the boat's bottom, and not your own. If you are in warmer waters use a better paint (Trinidad Pettit SR), and scrub the hull every couple of months. If you are in the water year-round, I would haul-out and paint after 6 months or so.
I would recommend painting the boat's bottom, and not your own. If you are in warmer waters use a better paint (Trinidad Pettit SR), and scrub the hull every couple of months. If you are in the water year-round, I would haul-out and paint after 6 months or so.
I agree with Gord May
I used Trinidad SR for my last bottom job. I have an Oday 23 and a gallon was enough for two coats. If you can use your boat several times a week you might be able to use paint with less copper. Serious racers will paint more often, but if your cruising two years is about right. If your worried about blisters, barrier coat before painting and keep your bilge dry. I think I will barrier coat when it's time for another bottom job in a couple of years.
I used Trinidad SR for my last bottom job. I have an Oday 23 and a gallon was enough for two coats. If you can use your boat several times a week you might be able to use paint with less copper. Serious racers will paint more often, but if your cruising two years is about right. If your worried about blisters, barrier coat before painting and keep your bilge dry. I think I will barrier coat when it's time for another bottom job in a couple of years.
A question for Gord May...
I've read a lot of your posts and you always seem to have good info, so....Do you think it would be worthwhile for me to barrier coat a boat that is used in fresh water to help prevent blistering?
I've read a lot of your posts and you always seem to have good info, so....Do you think it would be worthwhile for me to barrier coat a boat that is used in fresh water to help prevent blistering?
Preventaive Barrier-Coating
The efficacy of preventative barrier-coating is a highly technical, and somewhat contentious issue, encompassing a number of specifics, to which I have no simple, universal answers. Applying a proper barrier-coat, to a used hull (ie: not brand new & clean & dry) is a difficult, time consuming, and somewhat expensive project. As with any finishing enterprise (ie: painting), flawless preparation is paramount. Here’s the rub: After mechanically stripping the hull down to bare, clean gelcoat (a nasty job), you’ve got to let the laminate dry out. Depending upon the current laminate moisture content, and the ambient temperatures & relative humidity; this could take from at least a fortnight to a year or more (unless mechanical dehumidification-ventilation techniques are utilized). Barrier-coating a wet hull is, at best useless, and perhaps counter-productive. I’ve had numerous customers request barrier-coats (during refit projects), most of whom I’ve “talked” out of it. A “proper” job nearly always turns out to require more than they chose to invest (time out of use, and cost). Notwithstanding than numerous negatives, I’ve epoxy (tho’ Vinylester is a potential alternative) barrier-coated MY OWN last two (used) boats, as well as three (out of dozens of potential) customers’ boats. A few considerations: 1. Water permeation can occur from INSIDE the hull, as well as from outside. I almost always barrier-coat the bilges against standing water. 2. Although using a chemical paint stripper can make the removal of the bottom paint easier, these paint strippers can also affect fairing compound, gelcoat, and even the polyester resin in the laminate. The use of chemical strippers may create "paths" through which moisture can penetrate into the laminate and initiate hydrolysis or blister formation. In addition, by-products of the chemical paint stripper, including dissolved paint and resin, form a mold release-like film. This film can result in widespread adhesive failure of any coating applied over it. To insure that your surface is properly prepared, simply sand the surface with 80-grit paper, then remove dust and other contaminants using water and plain white paper towels. 3. The hull laminate must be DRY, prior to barrier-coating [just in case anyone missed it the first time
]. 4. Apply at least 12 mils, and preferable 20 mils thickness (0.002" - 0.020"). 5. Apply underwater barrier-coating to at least 6" above loaded waterline (under bootstripe. 6. Boats in warm water are more susceptible to water penetration and eventual blistering. 7. Cruisers, and others who leave their boats in the water for longer periods (without a good dry-out) are more prone to anti-fouling failure, water penetration & blistering. These boats also don’t get good frequent bottom inspections. Conversely dry-sailed boats, or those hauled out for winter, are less likely to suffer, and are more often inspected for early-stage damage. 8. In the case of a new boat, a barrier coat is highly recommended before the first immersion. It won't last forever, but it will forestall hydrolysis and blister formation. 9. The foregoing applies to un-blistered hulls. If there is ANY evidence of blistering, I'd apply an overall barrier-coat, after a complete blister repair is effected. Some background study on “Blistering” (what we want to prevent /w our barrier-coat) will help you to determine if prophylactic barrier-coating is worthwhile in your case: “THE CAUSES OF BOAT HULL BLISTERS” By Thomas J. Rockett, Ph.D. and Vincent Rose, Ph.D. University of Rhode Island; Kingston, Rhode Island http://www.daviscoltd.com/nams/Documents/Blister_Report.html “IN SERVICE FAILURES FROM THE MARINE SURVEYORS POINT OF VIEW” by Gregory T. Davis, NAMS-CM http://www.daviscoltd.com/public/Engineering/documents/macmrp.htm "Fiberglass Blisters - Effective prevention and treatment " by Chris Caswell http://www.boats.com/content/default_detail.jsp?contentid=1899 “Blister Repair Developments” By C. Joe Parker, Michael D. Arndt and Timothy J. Atkinson (Gougeon Brothers, Inc. West System Epoxy) http://www.mooremarine.com/blisrpdv.htm “BLISTERS & LAMINATE HYDROLYSIS” by Craig Bumgarner http://www.zahnisers.com/repair/blister/blister1.htm “Hull Blisters” (a collection) by David Pascoe, Marine Surveyor http://www.yachtsurvey.com/blisters.htm Gougeon Bros - WEST System website http://www.westsystem.com/ Sorry, I couldn’t be more definite, but as I began - the question requires a very technical analysis, and subjective evaluation. I just don’t have the time and energy to do the subject justice. Regards, Gord BTW: Jef M - Thanks for the kind words.
The efficacy of preventative barrier-coating is a highly technical, and somewhat contentious issue, encompassing a number of specifics, to which I have no simple, universal answers. Applying a proper barrier-coat, to a used hull (ie: not brand new & clean & dry) is a difficult, time consuming, and somewhat expensive project. As with any finishing enterprise (ie: painting), flawless preparation is paramount. Here’s the rub: After mechanically stripping the hull down to bare, clean gelcoat (a nasty job), you’ve got to let the laminate dry out. Depending upon the current laminate moisture content, and the ambient temperatures & relative humidity; this could take from at least a fortnight to a year or more (unless mechanical dehumidification-ventilation techniques are utilized). Barrier-coating a wet hull is, at best useless, and perhaps counter-productive. I’ve had numerous customers request barrier-coats (during refit projects), most of whom I’ve “talked” out of it. A “proper” job nearly always turns out to require more than they chose to invest (time out of use, and cost). Notwithstanding than numerous negatives, I’ve epoxy (tho’ Vinylester is a potential alternative) barrier-coated MY OWN last two (used) boats, as well as three (out of dozens of potential) customers’ boats. A few considerations: 1. Water permeation can occur from INSIDE the hull, as well as from outside. I almost always barrier-coat the bilges against standing water. 2. Although using a chemical paint stripper can make the removal of the bottom paint easier, these paint strippers can also affect fairing compound, gelcoat, and even the polyester resin in the laminate. The use of chemical strippers may create "paths" through which moisture can penetrate into the laminate and initiate hydrolysis or blister formation. In addition, by-products of the chemical paint stripper, including dissolved paint and resin, form a mold release-like film. This film can result in widespread adhesive failure of any coating applied over it. To insure that your surface is properly prepared, simply sand the surface with 80-grit paper, then remove dust and other contaminants using water and plain white paper towels. 3. The hull laminate must be DRY, prior to barrier-coating [just in case anyone missed it the first time
]. 4. Apply at least 12 mils, and preferable 20 mils thickness (0.002" - 0.020"). 5. Apply underwater barrier-coating to at least 6" above loaded waterline (under bootstripe. 6. Boats in warm water are more susceptible to water penetration and eventual blistering. 7. Cruisers, and others who leave their boats in the water for longer periods (without a good dry-out) are more prone to anti-fouling failure, water penetration & blistering. These boats also don’t get good frequent bottom inspections. Conversely dry-sailed boats, or those hauled out for winter, are less likely to suffer, and are more often inspected for early-stage damage. 8. In the case of a new boat, a barrier coat is highly recommended before the first immersion. It won't last forever, but it will forestall hydrolysis and blister formation. 9. The foregoing applies to un-blistered hulls. If there is ANY evidence of blistering, I'd apply an overall barrier-coat, after a complete blister repair is effected. Some background study on “Blistering” (what we want to prevent /w our barrier-coat) will help you to determine if prophylactic barrier-coating is worthwhile in your case: “THE CAUSES OF BOAT HULL BLISTERS” By Thomas J. Rockett, Ph.D. and Vincent Rose, Ph.D. University of Rhode Island; Kingston, Rhode Island http://www.daviscoltd.com/nams/Documents/Blister_Report.html “IN SERVICE FAILURES FROM THE MARINE SURVEYORS POINT OF VIEW” by Gregory T. Davis, NAMS-CM http://www.daviscoltd.com/public/Engineering/documents/macmrp.htm "Fiberglass Blisters - Effective prevention and treatment " by Chris Caswell http://www.boats.com/content/default_detail.jsp?contentid=1899 “Blister Repair Developments” By C. Joe Parker, Michael D. Arndt and Timothy J. Atkinson (Gougeon Brothers, Inc. West System Epoxy) http://www.mooremarine.com/blisrpdv.htm “BLISTERS & LAMINATE HYDROLYSIS” by Craig Bumgarner http://www.zahnisers.com/repair/blister/blister1.htm “Hull Blisters” (a collection) by David Pascoe, Marine Surveyor http://www.yachtsurvey.com/blisters.htm Gougeon Bros - WEST System website http://www.westsystem.com/ Sorry, I couldn’t be more definite, but as I began - the question requires a very technical analysis, and subjective evaluation. I just don’t have the time and energy to do the subject justice. Regards, Gord BTW: Jef M - Thanks for the kind words.Estimating Costs
Although I am presenting some of the “negative” aspects of preventative Barrier-Coating, please remember that I HAVE DONE MY OWN boats. Previously, I indicated that Stripping, Cleaning, Drying, and then Barrier-Coating a hull is a nasty, time consuming, and fairly EXPENSIVE job. Assuming an undamaged (mostly “Dry”)and fairly clean hull, I’d charge something on the order of $100 to $110 per foot (LOA) to Sand (basic), Clean, and Epoxy Barrier-Coat to (the MINIMUM) 10 Mils thickness. BUDGET For a 30 Foot Sailboat: I’d expect to use about 2 Gallons of Epoxy (@$200/Gal.), plus some consumables (sand paper, solvents, etc); totaling something like $600 Materials. I’d estimate my labour at about 40 to 48 Hours (@ $55/Hour for “Painting”); for a total of about $2,200 - $2,640. Materials (@ $600) + Labour (@ $2,600) = $3,200 Total PLUS any Yard Charges (Which may be considerable - Haulout, Daily Storage, Blocking, etc). Now, having applied the barrier-coat, you’re still faced with the Anti-Fouling job (about $15/Ft?). The above budget did not include the cost of any repairs (nicks, gouges, or BLISTERS), or extraordinary stripping/cleaning. As you can see, even a Do-It-Yourselfer is looking at considerable expense (perhaps $35/Foot), and time (a week’s holidays working, PLUS dry-out time out of use). Some Basic Instructions from “ Barrier Coating - New or Repaired Hulls” (Gougeon Brothers - WEST System Epoxy) 1. If the bottom has not yet been painted, wipe the entire surface with a cloth dampened with a silicone remover or solvent to remove remaining mold release agents or waxes. If the bottom has been painted, the paint must be completely removed with chemical strippers (*1) and/or sanding prior to coating. 2. Abrade the gelcoat surface below the waterline with 30-grit sandpaper. When completed, there should be no glossy areas. Mask freeboard at the waterline(*2) with masking tape. 3. For optimum moisture exclusion, we recommend a total in excess of 600 microns (23 Mils) of epoxy, which is easily achieved with six coats (about 4 Mils/Coat). Note: For best results, apply at 21Deg.C to 27 C, @ 40-60% relative humidity. The first coat should be applied with no additives. Each successive coat should include 20 to 25% WEST SYSTEM 422 filler (an aluminium-based barrier coat additive, which increases the epoxy’s resistance to moisture permeability) blended with the resin/hardener. All coats may be applied in one day. Apply the next coat as soon as the first coat will support its weight. If epoxy is allowed to cure overnight, wash with water and 855 Cleaning Solution, then sand before re-coating. If an impression can be left in the coating with your fingernail then the epoxy can be over-coated without washing and sanding. Do not thin WEST SYSTEM epoxy; doing so will seriously diminish the epoxy's moisture barrier effectiveness. 4. Thoroughly sand with 220-grit sandpaper before application of the antifouling paint. Follow the paint manufacturer's instructions for final surface preparation and application For further information on osmosis in GRP boats see: "Gelcoat Blisters: Diagnosis Repair and Prevention” (*1) I DO NOT recommend the use of “Chemical Strippers”! (*2) I Recommend Barrier-Coating above the waterline (at least 4 - 6"). Some further notes: THICKNESS: There are two standard measurements used to describe the film thickness of a coating, Mils and Microns. Microns are from the metric system and are equal to 0.001 millimetres, while Mils are from the imperial system and are equal to 0.001 inches. Since 25.4 millimetres equals one inch then 25.4 Microns is equivalent to a Mil; hence 254 Microns equal 10 Mils. APPROXIMATE COVERAGE: Assuming a barrier-coating thickness of about 10 mils (0.010"), a gallon of Solvent-Free Epoxy will cover about 160 Square Feet. Some “typical” approximate wetted surface areas (Area below the water line = Length x Beam x .85): 28 racer/cruiser = 250 sf 30 racer/cruiser = 270 sf 36 cruiser = 330 sf 41 cruiser = 435 sf 53 cruiser = 590 sf The 30 Ft. sailboat might require about 1.69 Gallons (270 ÷ 160) of epoxy, to achieve a 10 mil coating. Two gallons would provide a 10 mil overall thickness, with an additional coating at the waterline/bootstripe. Applied at 4 to 6 mils per coat, you’ll require a minimum of 2 to 3 coats. Remember, thicker (to about 25 to 30 mil) is better. And an other opinion on the efficacy of Barrier-Coating: <i>” ... Drying will lower the moisture content of the hull and may also remove some water content from the "osmosis" residues. However, as it is the remaining acid residue that causes the chemical process - and removing water only make the acid stronger - the long term effect will be devastating ...<i> AND <i> ... A water barrier coat is often claimed to effectively prevent outside water from re-entering the laminate. This is supposed to slow down the re-start of "osmosis" after a "conventional" repair. First, there is no such thing as an effective water barrier coating. Second, even a dried laminate still contains sufficient amounts of moisture to feed the process, especially in laminates which contain woven roving ...”<i> http://www.hotvac.com/what/default.asp and http://www.hyab-osmocure.com/osmocure_frame4.htm
Although I am presenting some of the “negative” aspects of preventative Barrier-Coating, please remember that I HAVE DONE MY OWN boats. Previously, I indicated that Stripping, Cleaning, Drying, and then Barrier-Coating a hull is a nasty, time consuming, and fairly EXPENSIVE job. Assuming an undamaged (mostly “Dry”)and fairly clean hull, I’d charge something on the order of $100 to $110 per foot (LOA) to Sand (basic), Clean, and Epoxy Barrier-Coat to (the MINIMUM) 10 Mils thickness. BUDGET For a 30 Foot Sailboat: I’d expect to use about 2 Gallons of Epoxy (@$200/Gal.), plus some consumables (sand paper, solvents, etc); totaling something like $600 Materials. I’d estimate my labour at about 40 to 48 Hours (@ $55/Hour for “Painting”); for a total of about $2,200 - $2,640. Materials (@ $600) + Labour (@ $2,600) = $3,200 Total PLUS any Yard Charges (Which may be considerable - Haulout, Daily Storage, Blocking, etc). Now, having applied the barrier-coat, you’re still faced with the Anti-Fouling job (about $15/Ft?). The above budget did not include the cost of any repairs (nicks, gouges, or BLISTERS), or extraordinary stripping/cleaning. As you can see, even a Do-It-Yourselfer is looking at considerable expense (perhaps $35/Foot), and time (a week’s holidays working, PLUS dry-out time out of use). Some Basic Instructions from “ Barrier Coating - New or Repaired Hulls” (Gougeon Brothers - WEST System Epoxy) 1. If the bottom has not yet been painted, wipe the entire surface with a cloth dampened with a silicone remover or solvent to remove remaining mold release agents or waxes. If the bottom has been painted, the paint must be completely removed with chemical strippers (*1) and/or sanding prior to coating. 2. Abrade the gelcoat surface below the waterline with 30-grit sandpaper. When completed, there should be no glossy areas. Mask freeboard at the waterline(*2) with masking tape. 3. For optimum moisture exclusion, we recommend a total in excess of 600 microns (23 Mils) of epoxy, which is easily achieved with six coats (about 4 Mils/Coat). Note: For best results, apply at 21Deg.C to 27 C, @ 40-60% relative humidity. The first coat should be applied with no additives. Each successive coat should include 20 to 25% WEST SYSTEM 422 filler (an aluminium-based barrier coat additive, which increases the epoxy’s resistance to moisture permeability) blended with the resin/hardener. All coats may be applied in one day. Apply the next coat as soon as the first coat will support its weight. If epoxy is allowed to cure overnight, wash with water and 855 Cleaning Solution, then sand before re-coating. If an impression can be left in the coating with your fingernail then the epoxy can be over-coated without washing and sanding. Do not thin WEST SYSTEM epoxy; doing so will seriously diminish the epoxy's moisture barrier effectiveness. 4. Thoroughly sand with 220-grit sandpaper before application of the antifouling paint. Follow the paint manufacturer's instructions for final surface preparation and application For further information on osmosis in GRP boats see: "Gelcoat Blisters: Diagnosis Repair and Prevention” (*1) I DO NOT recommend the use of “Chemical Strippers”! (*2) I Recommend Barrier-Coating above the waterline (at least 4 - 6"). Some further notes: THICKNESS: There are two standard measurements used to describe the film thickness of a coating, Mils and Microns. Microns are from the metric system and are equal to 0.001 millimetres, while Mils are from the imperial system and are equal to 0.001 inches. Since 25.4 millimetres equals one inch then 25.4 Microns is equivalent to a Mil; hence 254 Microns equal 10 Mils. APPROXIMATE COVERAGE: Assuming a barrier-coating thickness of about 10 mils (0.010"), a gallon of Solvent-Free Epoxy will cover about 160 Square Feet. Some “typical” approximate wetted surface areas (Area below the water line = Length x Beam x .85): 28 racer/cruiser = 250 sf 30 racer/cruiser = 270 sf 36 cruiser = 330 sf 41 cruiser = 435 sf 53 cruiser = 590 sf The 30 Ft. sailboat might require about 1.69 Gallons (270 ÷ 160) of epoxy, to achieve a 10 mil coating. Two gallons would provide a 10 mil overall thickness, with an additional coating at the waterline/bootstripe. Applied at 4 to 6 mils per coat, you’ll require a minimum of 2 to 3 coats. Remember, thicker (to about 25 to 30 mil) is better. And an other opinion on the efficacy of Barrier-Coating: <i>” ... Drying will lower the moisture content of the hull and may also remove some water content from the "osmosis" residues. However, as it is the remaining acid residue that causes the chemical process - and removing water only make the acid stronger - the long term effect will be devastating ...<i> AND <i> ... A water barrier coat is often claimed to effectively prevent outside water from re-entering the laminate. This is supposed to slow down the re-start of "osmosis" after a "conventional" repair. First, there is no such thing as an effective water barrier coating. Second, even a dried laminate still contains sufficient amounts of moisture to feed the process, especially in laminates which contain woven roving ...”<i> http://www.hotvac.com/what/default.asp and http://www.hyab-osmocure.com/osmocure_frame4.htm
Making it last
I have been using VC-17. This stuff is priced like liquid gold! when applying VC-17, it evaporates right before your eyes, really. One quart would barely do my 25 ft C&C until I got a tip from my local marina. Mix the supplied copper powder with the liquid coating and put it immeadiatly into a water bottle and screw the cap back on. Poke a hole the cap with a sharp object and squirt the VC-17 onto a 4" sponge roller and apply to the bottom of your boat as needed. I tried it and completed 2 full coats and had some left over! If applied from a paint tray you will see your liquid gold vanish before you can complete one coat.
I have been using VC-17. This stuff is priced like liquid gold! when applying VC-17, it evaporates right before your eyes, really. One quart would barely do my 25 ft C&C until I got a tip from my local marina. Mix the supplied copper powder with the liquid coating and put it immeadiatly into a water bottle and screw the cap back on. Poke a hole the cap with a sharp object and squirt the VC-17 onto a 4" sponge roller and apply to the bottom of your boat as needed. I tried it and completed 2 full coats and had some left over! If applied from a paint tray you will see your liquid gold vanish before you can complete one coat.
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