Our Old Boat - #6 - Keels
by Pam and Dennis Slaton
(Article Appeared in August 1998 TellTales Publication)

Since, we last discussed rudders, it is appropriate to move into keels, and their maintenance problems. No matter the type of the keel, the cast iron composition and resulting rust is the most time consuming factor in the maintenance equation. We have refinished a number of keels, and the approach to refinishing is determined by the current condition of the surface. Many times if the keel has a good basic overall shape and the rust deposits are not deep or numerous, we would not opt to expose the entire keel, but simply grind out the problem area and do a patch. But if a complete restoration is required, the best approach is sandblasting the surface to reveal all bare metal. Note that rust begins immediately, thus the need to apply a rust inhibiting paint prior to leaving the blasting booth, if not sooner!! A good inhibitor paint is Petit Rust-lock. Whatever paint you are using check for compatibility with the epoxy and filler that you will be applying next.

We have always suspended a swing keel from the cable eye and the keel pin hole. This makes for easier handling, (with a fixed keel you must endure working under the boat). The next step is to key or rough sand the inhibitor paint and clean the surface with acetone for a properly prepared surface to accept the epoxy. Seal the entire keel with a coat of pure epoxy rolled and then tipped with a brush to remove any bubbles. Make sure the epoxy penetrates all the holes in the metal. Once the first coat of epoxy is at the green cure stage, (note the appropriate time windows for recoating or you may have to sand prior to preceding) you can begin the fairing process.

We skim the entire keel with a thick coat of epoxy filler (we use the West Systems epoxy, 410 microlight and a small amount of silica to prevent the mixture from running). The consistency should be that of peanut butter. Upon curing we begin the tedious process of sanding and shaping using 80 grit sandpaper. This skim and sand process will have to be repeated until the imperfections are corrected and the shape is restored. In restoring the shape, remember that you are looking for symmetry with the draft about 40% to 45% aft of the leading edge, but remember that thinner keels equal less drag and better performance. Also a squared trailing edge is more desirable and the performance is enhanced over a knife blade edge. Our class rules allows for the refinishing of our keels, and given the crude imperfections found there is no problem in correcting the shape to achieve a symmetric form, however, you can not drastically change the shape or cord dimension measurements of the keel.

After the process of restoring the keel shape you are ready to address the usual barrier and anit-fouling paint issues. A high level of barrier paint protection helps to prevent future moisture penetration and the resulting rust. We have heard of the fiberglass wrap approach to refinishing the keel, but have never attempted it. Next month we will discuss the maintenance of the keel hangers, pin, etc.