Freedom Finishes

Yacht Maintenance and Care-101 Part #2-Bottom Painting

Antifouling and Bottom Painting

 Optimal cruising performance is often a reflection of your vessels underside. Your boats bottom coat is the first line of defense against some harsh elements trying to consume it. Staying on top of this preventative maintenance chore is one of the most important ones you face. The smallest amount of growth underneath your boat will affect speed and performance and if not sealed properly will penetrate your hull's gel-coat creating core rot (blisters).

Let's find the right paint for you!

Favorable bottom coatings for your vessel should depend on what type of boating you do, where you boat and the type of bottom paint applied to your boat in the past. Fresh water boating doesn't necessarily require the same strength and durability of bottom paint as say a fishing boat in the Florida Keys.

"Bottom paints act as a barrier to reduce marine growth and barnacles by releasing toxic biocides at a carefully controlled rate" Back in the day of old the bellies of boats were nailed tight with copper platting, now copper compounds (cuprous oxide) are laden in the bottom paint itself to combat growth some contain "slimacides" which greatly reduce the sun's deterioration of paint along the water line by filtering out UV and blocking photosynthesis.

2 Types of Anti-fouling Bottom Paint

It's important to remember the pros and cons of each type of bottom paint. Compatibility of one paint on top of another is critical. Generally speaking softer paints can be applied over harder paints but not visa versa

Modified Epoxies

Modified Epoxies deliver a hard durable finish but require yearly repainting. The higher the cooper content the more resistant it is to algae and growth. Keep in mind "the cheaper paint, the less copper and protection" I don't recommend short changing price for durability and protection. The warmer the water and longer the boating season the higher the bottom growth and better protection you'll need. Modified epoxies are popular because they are typically cheaper and can be painted over each other if the bottom has been sanded properly for a nice firm lock.

Ablatives

Ablative paints are softer semi-hard paints that flake off over time much like a bar of soap. Multiple coats the 1st time applied is recommended and is well worth it. Ablatives with boosted copolymers are very popular because they allow a vessel's bottom to go 2 or 3 years sometimes with out needing to be repainted.

TIP: When applying multi coats of Ablative paint make the base coat a different color of paint than the successive layers. Perhaps RED and other layers Blue or Black. This will allow you to see when you are down to your base level.

WARNING: Do not paint a modified epoxy paint over an ablative paint with out removing it completely first by sanding! It will simply flake off and your money and protection will be lost.

Preperation is Critical! Let's do it!

1. Pressure Washing-Should the hull have growth remove thoroughly with a pressure washer using a mold release agent
2. Sanding and Prep-Should older paint exist remove using a DA and 100 grit sandpaper taking the underside of your vessel down to fresh gel-coat. If any blisters exist (bubbles caused from water penetration) remove them using the interlux repair guide to achieve a perfect underside substrate for an impermeable layer called the Barrier Coat.
3. Applying a Barrier Coat-A barrier coat is an impermeable layer of epoxy that you will apply between paint and hull so that water cannot be absorbed and blisters cannot form-much like a primer. After applying and dry time has exceeded lightly sand with 120 sandpaper to give a perfect texture for bottom paint to adhere.

Applying Bottom Paint

 

• Safety first-Make sure you have the proper safety gear to protect yourself completely i.e gloves, respirator and body suit.
• Make sure you have the right amount of product. (see chart below)
• Make sure that you have a good weather window (2-3 days) to apply.
• Remember to work in conditions above 50 Fahrenheit and take in consideration if your recoating,  most paints have a window of time to over coat. If you wait to long you'll have to sand and re-apply.

    IMPORTANT! The care and effort you put into preparing the surface for each coat will greatly impact how well and how long the paint keeps your hull free of marine growth and fouling. So use the right material-plenty of solvent wash products, clean cotton rags and 80-grit sandpaper will help guarantee success.

• Tape off the vessels bottom as close to the boot stripe as possible. Many times the scum line on a boat with full water and fuel tanks is a good  place to start the tape line. Also tape around the transducers, prop shaft struts, thru-hulls and other metals.

•  If painting over existing bottom paint where heavy fouling exist; pressure wash and use a strong acid; be sure to use a respirator and full suit to protect you from caustic chemicals. Make sure any loose paint is removed with a scrapper, using a 80 grit sandpaper on high or uneven areas. You want the boat's bottom to be as smooth as possible to minimize drag. Wipe down with a tack rag and denatured alcohol after sanding.

• If painting a new hull-sand with 120 sand paper and clean well with a mold release solvent before applying barrier coat, let dry then sand with 120 grit before applying bottom paint.
• Rolling the paint is the most common method of application using a 3/8 nap solvent-resistant roller cover
• Stir the paint thoroughly , pour into a paint tray and begin rolling the paint below the tape line from one end of the boat to the other.
• Re coating Make sure the dry time on the 1st coat has expired before recoating.

• When finished remove paint and properly dispose of canisters and used brushes in a trash bin designated for hazardous materials.
• Read manufacturers recommendations for application procedure and drying times before you launch the boat.

Tip! A good way to determine paint quantity is to estimate the surface area needing paint below the water line: Most paints have a theoretical coverage area and require 2 coats, so expect actual coverage to be no greater than half of the theoretical value.

Length x Beam x .75=Approximate Underwater Surface Area in sq.ft

 

Vessel Size                    Amount of Paint Needed-gal (2 coats)

32'                                 2 gallons

 

36'                                 2 gallons

 

40'                                 2.5 gallons

 

45'                                 3.5 gallons

 

50'                                 4 gallons

 

60'                                 5 gallons

 

70'                                 6 gallons

 

80'                                 6.5 gallons

 

90'                                 8 gallons

 

100'                               9.5 gallons

 

Should you have any suggestions or questions please don't hesitate to ask or make a comment. With products and application techniques quickly advancing we are always searching for the very best methods of approach to all vessel needs.-Josh Cunningham