Cabin Framing
The cabin structure consists of side panels and cabin roof panel built using cheap ¼-inch thick lauan flooring plywood. The material was “new old stock” that had been purchased about 20 years ago when lauan was still pretty good stuff. I cut off a small sample and subjected to a “boiling water” test to see if it would delaminate. After a few days of immersion, I was satisfied that it would be “good enough” for above-the-waterline use.
On my design sketches each of the cabin-cockpit dodger sides were cut from a 4x8 sheet of plywood, with significant wastage. In the interest of economy, I decided to make both cabin side panels from a single sheet of plywood, and then add the dodger as a separate element (and this would turn out to be a fortuitous decision). After much head scratching (and after making a cheap pattern), I made a strategic diagonal cut along the length of the plywood sheet, and then cut out reliefs for the Cutter’s dashboard moldings. Before I did anything else I epoxied two stiffening cleats, ripped from a 2x4, to the top edge of each side. These cleats -- similar to what Bolger and Michalak would call “outer chine logs” -- would eventually be used to capture and “bed” the edges of the cabin top panel.
Then I coated both sides of each panel with two layers of neat epoxy (Raka’s 127 resin and 606 slow hardener), leaving the gluing surfaces uncoated. Even though the temperature was in the 80s, the Raka epoxy worked well and gave me enough working time to brush it on using cheap brushes. The cleats along the top edges made it easy to manhandle the sides around the shop, and into and out of the Cutter cockpit -- for the multiple times that I needed to adjust the deck cutouts.
Once I was satisfied that I had the sides aligned properly -- a critical step -- I epoxied them to the roughed-up fiberglass cockpit sides. I only glued the vertical surfaces inside the cockpit and did not epoxy the panels to the front deck at this point so that I would be able to pull the sides in -- if necessary -- to fit the cabin top.
The first cross support that I attached was the aft cabin bulkhead. It was epoxied to the front edge of one of the original rear seat supports (photo below). Since much of the athwart stiffness of the original Cutter hull was in the supports tabbed to the hull bottom, the idea was to add the bulkhead and cabin top before removing the rest of the seat supports. I used several pieces of used plywood (from the electric catamaran's cockpit bottom) to save material and to recycle some thick, double-thickness plywood that will support the steering wheel. Once the bulkhead was installed, the shape of the side panels began to be locked in; you can see the epoxy fillet along the cabin sides. Skipping forward a bit, once the bulkhead and the top were completed, the rest of the seat support was cut off. However I did leave about two inches of the rear of the support to act as a “rib”.
I used information from the “The Gougeon Brothers on Boat Construction” on designing deck and cabin tops (https://www.westsystem.com/wp-content/uploads/GougeonBook-061205-1.pdf, page 339) to fabricate a nicely bowed pattern to make the cabin top supports. I used the pattern and one of the seat supports to align the front end of the side panels. As mentioned previously, I did not epoxy the forward ends of the sides so that this could be accomplished without putting much of a compound curve into the lauan ply. Once everything was aligned I could finished up epoxying the side joints along the front deck. Using the pattern this way worked out well, and it gave very nicely shaped panels and joints. I will add this pattern/align technique to my building process in the future.
Sticking with the Raka epoxy, I used an epoxy/colloidal silica paste -- no glass cloth -- to strengthen all of the cabin side joints. Once that was cured, all I had to do was use some filler and sandpaper to smooth out the fillet joints. You’ll notice throughout my building process that I was not too concerned about the original fiberglass surface of the Cutter’s deck. Although the hull was in pretty good shape, the red gelcoat on the top deck was burned up years ago and was in very poor shape. Many holes that had been drilled into the panels for various purposes would need to be filled and faired, and it was clear from the start that the boat would need to be repainted. Therefore I did not do much to protect the deck and I used it as my workbench until I reached the fairing and painting steps.
With the sides now firmly attached to the foredeck, I then fitted and attached the cabin’s front panel, a piece of lauan ply ripped from the sheet that I used for cabin top, which had been precoated with epoxy on the side that would end up inside the cabin (I wanted to reduce my exposure to epoxy in closed spaces as much as possible, and I do most of my work involving epoxy outside of my shop on the gravel tarmac).
Using the pattern, I cut out two more cabin top supports and temporarily screwed them them to the sides so that the span across the top was almost exactly 48 inches. This pulled in the top edges a bit, and the slight curve stiffened the sides up even more. In the photo below, looking aft, you can see the rear bulkhead and the roughed out cabin door. The bulkhead was fabricated from two pieces of repurposed marine plywood. It had been sealed with epoxy and painted grey on one side and white on the other. The grey side had been exposed to the weather and had checked. Before I installed it I roughed up the checked side and recoated it with epoxy.
Next up: gluing the top down.
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