Today’s spars are usually made of composite carbon fiber or aluminum extrusions. Both of these mast materials, just like old wooden masts, require a finish. Whereas wooden masts were typically coated with a clear varnish, they could also be found painted. These more traditional finishes were typically brush applied or rolled and tipped. Spray finishes became more popular towards the end of the wooden spar era. The paints and varnishes of old were also oil-based instead of being polyester-based, like many of the high end finishes found today in the marine or aeronautical industries.
Today, Carbon fiber spars use either a clear urethane or one with a pigment, typically black or white, and are applied via spray-gun. Aluminum masts are also typically finished using the same pigmented polyester-based polyurethane and applied through spray application. Aluminum however, always requires an epoxy-based primer before applying the top-coat to the aluminum spar. The epoxy primer provides a superior moisture barrier as-well-as, a surface to improve the adherence of the urethane, which is crucial for UV resistance. Although it can’t hurt, a carbon spar does not require an epoxy primer as the epoxy used to laminate the carbon fibers (along with a good etching) ensures quality adhesion by default. Using a clear urethane on a carbon fiber or wooden spar gives the mast a really unique and glossy look that magnifies the patterns within the laminate or the grain. However, this type of finish is more tedious to execute, requires more maintenance and has a shorter life span than its pigmented counterpart.
Aluminum masts can also be found in a black or clear-anodized finish, which is preferred due to its durability, but may not always be available. Aluminum spars are also most often painted, typically in either black, or some shade of white/cream. Although rare, aluminum spars can be powder-coated, which has also proven to be a very durable finish.
So why does one need to have a finish on these various types of spar materials? Wood will deteriorate from moisture and sunlight. Carbon fiber by itself, does extremely well in a high U.V. environment. However, the epoxy used to laminate the fibers is very sensitive to sunlight and will break down. Unfinished aluminum can be highly corrosive. Carbons, salts, and electrolytic activity in combination with dissimilar metals are some of the factors that can help accelerate this corrosion process.
Some of the preparation methods to ensure a finish is properly applied are as follows:
- All types of spars (PRE-PAINT-PREP) should have the hardware removed, cleaned, inspected, and replaced if necessary (don’t cheat yourself in leaving on any hardware). Note: remember that the purpose of a refinish is to refurbish and preserve the spar material and the associated hardware.
- Carbon-fiber spars (PAINT-PREP) will simply require a good etching with a medium-fine grit paper, such as a 220 or 320. Follow that with a good rinse (with a de-greasing soap) along with a chemical wipe just before painting.
- Wooden spars (PAINT-PREP)should also be finish-sanded to a medium-fine grit, such as a 220. You can then use wood bleach or oxalic acid to brighten and clean the wood if applying a clear finish. Be sure to rinse the this acid with vinegar to neutralize it and remove any residue that may conflict with the finish adhering properly. A tack cloth should be used just prior to applying the finish to remove any remaining unwanted dust and/or particles.
- Wooden and carbon-fiber spars (CLEAR COATS), when applying a clear finish to either, you should take extra care to remove all of the old finish, otherwise this could lead to a “spotty” finish.
- Aluminum spars (PAINT-PREP)should be sanded to a rougher, medium grit of 120 to give the metal a well-etched surface for the primer to ‘bite’ into. Any highly corroded areas should be spot treated via media blasting. The metal should then be washed with an acid solution to combat the basic nature of the corrosive process. This process will also remove any grease, oil and dirt from the surface, for the primer and the topcoat to adhere properly. A good chemical wipe or tack cloth is also a good idea right before applying the primer.
After the spars have been painted properly, you should take extra care to ensure that all of the hardware gets installed using new fasteners and sealant. This step will provide a seal and a barrier between the hardware and the spars.
Maintaining these finishes will ensure longevity and is achieved by re-coating the spars within the time period recommended, as per the paint manufacturer’s requirements. When re-coating you should also remove, re-bed and refasten the hardware associated with the spar. If the existing base coat is intact and meets the manufacturers adhesion requirements, these finishes can typically be dulled with a medium-fine grit like 320 and red Scotch-Brite. Then follow the aforementioned rinsing methods (for Carbon Fiber) and apply another series of coats, as needed.
In conclusion, typically (at least in the middle-Atlantic type regions), one can expect pigmented polyurethane finishes to last 7-10 years or longer; non-pigmented polyurethanes may last up to 5 – 7 years. In most cases, these finishes could be re-coated within those time frames. Granted, these are generalizations and are dependent upon the product used, the geographical location and use, as well as the method in which they were applied. As always, please seek the help of your local rigger or marine painter for specific instructions on dealing with your spars particularly.