We are restoring a 1947 Gar Wood Commodore. The first step in the restoration process is going to be the replacement of the bottom. Sierra Boat will use a method we call a "Urethane Membrane Bottom". It is our variation on the well known 5200 bottom and is essentially a traditional bottom done with more modern materials. The advantage of the urethane system over a 5200 bottom is repairability. Since the outer planking is bedded to the membrane with low adhesive compound, (Boat Life), the repair cost to any future damage is greatly reduced. This advantage is achieved without any compromise to strength or durability. We have been using this system for over a decade and our first bottoms are performing as they did when new. Follow Danny Salvador as he goes through the process. The first step in the process will be to remove the old fiberglass bottom. Fiberglass bottoms are not necessarily a bad thing. We have done a lot of them over a 40 year time span and most are still holding up. This bottom, however, was not a quality job. We were able to peel it off with little trouble. The surprise, after the glass was off, was to find a bottom in excellent condition. Original planking was carefully removed so it could serve as a pattern for the new planking. Note the original canvas inner layer.This layer originally provided a waterproof layer, but did so for only the first few years of the boat's life. Key to our new bottom will be to replace this layer with something more modern and durable.
After the outer planking and inner planking was removed, we inspected and repaired framing as needed. Most of the framing was in excellent condition and no dry rot was found anywhere.We replaced all of the intermediate ribs as well as a few bottom frames. The keel was removed and repaired as well. Gar Wood used plywood gussets or knees forjoining the side frames to the bottom frames as well as the stringers to the bottom frames. The plywood from the 40's isn't what it is today and much of it had de-laminated. New, marine grade plywood was installed. All of the framing was given a generous coating of Smiths penetrating epoxy. Lastly, all structural fasteners, including keel, stem and chine bolts, were replaced.
Once the framing was repaired, we were ready for a new inner bottom. Inner bottom planks were cut from 6mm BS 1088 marine ply in the same widths and orientation as the original planking. The plywood inner planking will look like the original planking to any concours judge, but is much stronger and more stable. The planking was coated with penetrating epoxy and adhered to the framing with Boat Life and plastic staples. We also seal between the plank seams so our urethane will not leak through.( Note: the staples are just for assembly purposes, screws run through the outer planking will eventually be added)
Now for the fabric and urethane. Instead of using 3M 5200, we use a chemically similar, but vastly superior product for this application. First, a polyester cloth is laid down. This cloth is then saturated with an industrial urethane applied by roller. The urethane is specifically designed for waterproofing and rot prevention. Once cured, it will be akin to the material a Zodiac is made from. it is strong, flexible, waterproof and pretty much indestructible. This fabric and urethane replaces the old canvas. At this point, the boat would float even without the outer planking.
New planks were patterned from the old ones. The planks were coated on their inner surface with penetrating epoxy. The new planking is screwed down and bedded in Boat Life, leaving a 1/6" gap between the planks. This gap is necessary because even with epoxy sealing, the planks will swell some. The the screw holes were filled with putty and the entire bottom is faired.
Once the fairing was complete, the bottom received three coats of penetrating epoxy followed by an epoxy primer and copper bottom paint. Note, bottom side planks will also be sealed with penetrating epoxy and bedded in Boat Life.
Last Updated ( Thursday, 15 December 2011 21:04 )