Rudder Repair and refinish Montgomery 23 Dauntless The before photograph A receipt found inside the boat showed a previous owner had enlisted a boat yard to perform maintenance on the rudder by shortening it two inches and reshaping the tip of the blade. The rudder was glassed over below the water line and had several layers of anti-fouling paint. In various areas fiberglass had delaminated from the mahogany. The fiberglass was removed by ripping it off the wood in large strips. It came off easy and below it was raw, wet mahogany that had not seen daylight or dry air for many years. This project is in the state of Arizona and the dessert air with its ambient humidity of less than 10 percent worked its magic to dry out the wood while plans were formulated to recover the lost 2 inches of the rudder. If this is attempted in humid areas, a dehumidifier in a closed area may be useful. Page 1 of 11
Once the wood was dry, cutting off the worn and tattered bottom of the rudder blade gave a clean, true surface to mate a new piece of mahogany. A table saw worked perfect for this. There were visible splits in the bottom of the rudder making it necessary to move up another 2 inches for the cut. With this added material removed it required replacing four inches of rudder. Page 2 of 11
A jig was designed to drill the holes for dowels into both pieces. The outline of the bottom of the blade was traced onto a piece of thick scrap hardwood. The centerline was marked and two points were made where the dowels would be located, one forward and one aft. Two alignment marks crossed from the piece of scrap wood onto the rudder so that positioning could be repeated after the jig was removed. A drill press was used to make the holes in the positions marked on the hardwood. The alignment holes guide the handheld drill bit into the rudder and the added piece of mahogany, creating holes for the dowels. It is necessary the holes be perfectly straight and perpendicular to the surface. With the jig made it is now possible to make the dowel holes in both the rudder bottom and the 4 inch piece to be added. Page 3 of 11
Holding the jig in place against the trimmed bottom of the rudder, the two alignment marks are transferred that were made when positioning the jig, from the rudder to the piece of wood to be added. This made it possible to position the jig onto the added piece of wood for drilling by aligning the marks with those already on the jig. Drywall screws were used to hold the jig temporarily in place and two holes were drilled 3 inches into both the rudder and the new piece. A simple piece of tape on the drill bit would serve to indicate depth. Page 4 of 11
A quick test fit will show perfect alignment. The dowels are ½ inch in diameter and six inches long made of stainless steel. This insures a durable long lasting fix. Page 5 of 11
The rudder is too long for most bar clamps to reach from top to bottom. Two pieces of 1x2 scrap lumber are clamped to the sides of the rudder to create a lip for the bar clamps to grip. Two drywall screws are put through the 1x2, into the rudder to keep it from slipping. Most of the holding power comes from the friction induced by clamping the ends of the 1 X 2. The holes made by the screws are filled during fairing in another step. West system 105 epoxy with #406 Colloidal Silica filler is used for the bond. The dowels are degreased with acetone and surface sanded with 80 grit sandpaper to give the epoxy something to bite onto. The epoxy resin is mixed without any filler first and the entire area (flat surfaces, dowels, and holes) painted thoroughly. The un-thickened resin penetrates the wood better than after the filler is added. Once painted with the un-thickened resin, the filler is added to the mixture and then applied to both surfaces, prior to clamping. Page 6 of 11
With the epoxy cured the clamps were removed and the new piece is belt sanded to the rough shape and then finish block sanded and faired to match the profile of the existing rudder. The damaged original rudder tip may be utilizes to design the profile on the bottom of the added piece of mahogany. If the profile is not perfect, patches of fiberglass cloth will bring up low areas while in other minor areas resin thickened with #407 low density filler is used. Low density filler is useful as it is easy to sand and fair. An invaluable tool for the fairing is a straight edge ruler or bar. Laying it on edge along the rudder blade will show areas that are low. After the filler is dry a long sanding board is used to sand the rudder fair. It may require several attempts of sanding followed by filling to properly fair the section of the rudder that is below the water line. Page 7 of 11
The Montgomery rudder employs a manual lifting mechanism, consisting of a rather large hole in the blade. A three sixteenths inch line then runs from an eye-strap on the transom on the port side of the rudder at the gunwale, down through a hole in the blade and back up to the transom gunwale on the starboard side where it is made fast to a cleat. Shorten the line and the rudder rises. Years of repeatedly use had cut a groove in the wood. A solution is to completely fill the existing hole with thickened epoxy. After cured re-drilled the hole and insert bronze bushings in both sides (bushings available at Ace Hardware). Page 8 of 11
For extra strength and to waterproof the entire blade; begin at six inches above the water line working towards the bottom, fiberglass the blade with 2 layers of 6oz fiber-glass cloth and an additional 2 layers of 6oz fiber-glass tape on the leading and trailing edges. The bottom of the blade receives 5 layers of 6oz tape to guard against impact damage. The tape is easier to work than the cloth. The edges of the tape are hemmed, preventing the fibers from pulling apart like they do on a cut edge of cloth. Page 9 of 11
Once the glasswork is completed wait a week to allow the resin to fully cure. Then barrier coat the bottom of the blade with 5 coats of Interlux 2000E. 2000E is a product that effectively seals the water out. Depending on the air temperature you can re-coat in 3-5 hours (read the directions). Lightly sand the barrier coat just before the bottom paint is applied as the final coat. If bottom paint is put on within the time interval specified it is possible to apply without resanding of the barrier coat. Read the directions; it is a two part system (epoxy) and needs to be mixed in the right ratio and needs to sit for 20 minutes after it s mixed (induction time) before applied. Page 10 of 11
For the topsides bright work the rudder is sanded smooth and 4 layers of West System Epoxy with 207 Clear-Coat hardener is applied. This product is not UV stable and requires a finish of UV blocking varnish after the one week curing time. Read the directions completely on all chemicals before a project like this is begun and the results will be outstanding. Onto the next project! Sean Mulligan The End