My Merlin Rocket: October, 2013

The Bow Tank Top Reinforcements

The Merlin Rocket Owners Association website has a great reference library and photographs on boat repair, renovation and self build. I do a bit of research in the site, looking for tips and advise.

In one of those libraries I found an interesting photograph. I wondered, what would happen if I had to go under the deck to do upgrades, maintenance or repairs? The bow tank top would fail and collapse under my weight. It is made of 4 mm thick marine plywood supported by the bulkhead, the bow tank beam and top of plank land #4.

I decided to add Red Western Cedar strips next to the top of plank land #4 and a center beam from the bulkhead to the stem. Additionally, I added two vertical supports from the hog to the beam.

The Shroud Knee

There are 2 shroud knees made of 12 mm marine plywood, half-lapped on to the bow tank bulkheads. I secured the starboard shroud knee to the bow tank bulkhead with a clamp and used an angle finder to determine the bevel angle between the shroud knee and the planks. Notice I position the angle finder perpendicular to the shroud knee and not in parallel with the plank.

I then positioned my angle finder against the band saw miter fence and read the angle on the scale. This step can avoided by using an angle finder with a built in scale.

Then, I set the band saw table at the same angle and proceeded to cut along the edge of the shroud knee. Before cutting, I made sure to mark the area to be removed. Given that my band saw table only inclines to one side, I started the cut on the port side shroud knee from the opposite side.

Before bonding the shroud knee I set it in place and clamped it on both ends. Then, I inspected the fit for gaps.

Looking at the shroud knee fit from the other side... not bad.

Another view of the starboard shroud knee.

A photograph of the shroud knees from the transom. I laid the bow tank tops to ensure the fit was right.

Filleting, Sanding & Epoxying

All these fittings inevitably come with their fair share of bonding and filleting, followed by painstaking sanding, sanding and more sanding. Afterwards, I coated the inside of the hull with epoxy. A couple of times over the fiberglass reinforcements until smooth.

A view from the bow.

Another view from the bow, this one up a bit higher.

Middle Gunwhale Lamination

The middle gunwhale lamination is 15mm wide x 25mm tall, and made of Western Red Cedar. It tapers out between station #1 & #2. Detailed dimensions at each station can be found in the GUNWHALE / RUBBING STRAKE CONSTRUCTION drawing provided by designer Keith Callaghan.

To fit the middle lamination over the inner lamination, I had to use small wood screws to hold them together while bonding. Once dry, I removed the screws. The angle and curvature of plank #8 makes it almost impossible to clamp the middle lamination securely over the inner lamination.

First, I held the middle lamination flush (at the bottom) against the inner lamination. Then I used a small drill bit to drill a screw pilot hole every 18 inches and avoid splitting the stock. For bonding, I applied West System epoxy resin with Colloidal Silica to both surfaces. Then I hand-tightened the screw. One at a time.