Why a Chainsaw is a one of the BEST Boatbuilding Tools Around

RRRRRAAAAAGGGG!!! There is nothing like the sound of a chainsaw cutting through fiberglass to arouse the interest of the curious in a boatyard. I was a chainsaw amateur, but my friend Mark wielded it with gusto and a certain sick glee.

It started innocently enough. We were searching for a cruising catamaran, with a big bridgedeck cabin, for future offshore cruises. I'd been watching a certain one in the local boating publications. At $129,000 (all prices in Canadian $) it was way too pricey. But when they dropped the price to $105,000, I began to become interested. When it hit $89,000 I decided a day long ferry ride to Vancouver Island and back was required to view the boat.

My wife, my 3 year old daughter, and I were taken to the boat by the broker, and left to view it in peace. We looked through it all quickly and then sat down for a family conference - o.k. perhaps my daughter was more interested in nursing or a nap. I grabbed a piece of paper from the chart table and started sketching and roughing out some cost figures. What we had here was a pair of good hulls (we hoped), a rig and sails, a couple of outboard engines - one of which was of questionable vintage, and a bit in the middle of the boat that we were not too interested in. We left Vancouver Island and decided to have a good think about this boat.

After much deliberation, a bit more cost estimation, and some more sketches, we made another visit to Vancouver Island, this time with my father in tow. His job - mind the kid while we deliberated. My dad was rather doubtful I recall; this was a big project to consider. Our tentative plan was to remove the old little pilothouse with seating for 4 seated close friends, and replace it with a bridgedeck cabin with standing headroom and a big saloon for dining. And add a diesel in one hull. And replace the main mast beam.

I had always sworn to my wife that I'd never build a boat bigger than a dinghy, but what we were contemplating was a few orders of magnitude bigger. We finally bought the boat for $57,500 + taxes, and began to plan our changes. For the first summer, we sailed her "as-is". She was very fast, hitting 10-12 knots in moderate winds, and 15 knots one memorable day when we should have reefed a bit sooner... But we realized that the somewhat cranky outboards would have to go, and walking from one hull to other in the rain wasn't much fun. Clearly the big bridgedeck cabin was also going to be required to make this boat a liveable home.

I'm a naval architect and mechanical engineer, so planning and designing the proposed modifications weren't too challenging for me. The hardest part was trying to avoid a boxy cabin look on a boat with relatively low hulls. More modern cats avoid the boxy look of a high cabin by having high freeboard hulls; the cabin is not so tall. But to give ourself enough bridgedeck clearance (about 27" fully loaded) and have standing headroom (I'm 6'2"), we had to make the cabin taller than I would have liked. There were a lot of iterations before we had a shape I liked.

Construction Begins

In the spring of 2005, progress commenced on prefabricating the fiberglass/foam panels that would form the new cabin and cockpit sole, the new carbon fiber mast beam, and the bridgedeck cabin panels. I worked mostly alone, sometimes with helpers, in a friend's single car garage. Work took place on weekends and some evenings. Raw materials included a 55 gallon drum of epoxy resin, 15 gallons of hardener, 3 rolls of triaxial and biaxial fiberglass, and a few large sacks of colloidal silica and microballons.

The panels were all shaped to be fully developable. That meant that they were flat or could be formed out of sheet goods with single curvature. An egg is an example of compound curvature or something that couldn't be developable. A cylinder or part of a cone can be made with a piece of paper and is thus developable. I used formica covered plywood for mold surfaces, both flat and curved. This ensured that the final panels would all have a glossy finish.

All the panels were cored with 3/4" thick Corecell SAN foam, probably the best foam available for boatbuilding, though it is the most costly. Curved panels had sections cut into 1' wide strips and these were heat formed over a propane heater and placed against the mold surface until they cooled, locking the shape into the foam. All the foam panels were drilled through with a 1/8" drill, at about 3" centers. This allows excess resin to be drawn through the core during vacuum bagging operations.

A word about vacuum bagging - if you're working with anything but a very small cored part, it's nearly essential. Almost all my panels were done in one operation, with inside skin, outside skin, and core combined in one operation. For this to work, I used a resin with a very long working time; about 5-6 hours for a 150 gm mass at room temperature. In a cool garage, I could use a 5 kg bucket for a few hours before it started to kick. Otherwise, you need to mix smaller batches of resin. Only a few of largest curved panels were done with outside skin + core in one operation, and the inner skin laminated on later.

A almost new 6 CFM vacuum pump was picked up on Ebay, some other vacuum bagging supplies from local stores, and I was in business. After a busy 3 months building parts, we spent a final few weekends sailing during July before boat surgery commenced.

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