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Posts Tagged ‘Penobscot 13’

Inevitably, I’ve been distracted. Before getting down to business, allow me to illustrate why, and perhaps justify in part why I have been so tardy in sharing any progress on the Shearwater.

Back in early April, I became the lead instructor for the Wind and Oar Boat School. With that increase in responsibility came a decrease in personal boat building time. Check out a brief glimpse at what some of my classes have involved:

Building models with a group of middle school students at Cascade Heights Public Charter School. Don’t worry, it wasn’t all fun and games. Among other things I had them do a displacement estimate on an existing design for a sail and oar boat. I thought that was fun.20140704-185705-68225749.jpg

I had the pleasure of helping my high school students from Merlo High School finish an Arch Davis designed Penobscot 13:

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Fitting the oarlock sockets. 20140704-185837-68317437.jpg

Shaping the tiller.

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Post launch.
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Somewhere in there a lovely Bevin’s Skiff was built by a group of students from Southwest Charter School:20140704-185704-68224940.jpg

Currently I am working with a group of students at Jackson Middle School building another Bevin’s Skiff, and below are a few glimpses of the Arch Davis designed Sand Dollar being built by SEI students at ADX.
20140704-185839-68319817.jpg 20140721-225011-82211934.jpgSomehow, after teaching boat building to my students each day, I still enjoy going home to work on my own boat. At times, there has been less time left over than I would like, but considerable progress has certainly been made since my last update.

After the last update, the next pair of planks were patterned, scarfed and mounted. I got most of a final plank out of the 16 foot sheet previously scarfed, but the rest of the planks were scarfed together out of three pieces each to conserve plywood.

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After another round of beveling, the sheer strakes were finally patterned, scarfed, cut and mounted.

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With planking completed, my short-lived tiny plywood cathedral was complete.20140704-183733-67053449.jpg20140704-183734-67054309.jpgBefore the boat could be flipped over, the external keel,stem and sternpost were pieced together, fitted, shaped and mounted.20140704-183604-66964473.jpg20140704-183605-66965272.jpg

Finally, after many months of waiting, the boat was flipped over. The stem and sternpost were left quite long. They continue to be quite flamboyant in a viking-esque sort of way.

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With the boat upright, a variety of projects were started. Among the first was a complete redesign of the centerboard.

[Warning: the next section may be best reserved for only the nerdiest among you.] From my first look at the plans, I didn’t like the shape of the centerboard. It was a low aspect ratio wedge, and looked impossibly difficult to put a good foil shape on. Perhaps I should have kept in mind the thought another Shearwater builder shared with me, suggesting that the boat is quite tender and a sail rig would only be reasonable as a downwind rig. This idea would suggest I should have left well enough alone and not worried about upwind efficiency or doing my best to shape the board into a NACA 0012 foil shape. I suppose I must be stubborn or something, because I ignored those ideas. I embarked on a geometric journey far beyond what I ever expected. Who knew the geometry of a centerboard was so complicated? The brief explanation of the process is that I estimated the location of the center of lateral effort of the current centerboard (just the board, not the whole boat), and used this boat as the starting point of a new board. The length of the new board was limited by the location of the central frame, and the length limitations on the board helped dictate the width of the board, as my goal was to design the new board to have a similar area to the old design (theoretically, since it has a higher aspect ratio than the old design, it could be a bit smaller. I might have ended up making it a bit smaller, but not by more than 10%).

The board is built up of several long pieces of clear fir epoxied together. I worked to achieve a NACA 0012 foil section, and have subsequently fiberglassed it and filled the weave with epoxy thickened with graphite powder. In addition to being efficient it should be nearly bomb proof.

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20140704-184252-67372361.jpgAt some point work began on the spruce oars. Though I have picked at this project and they are a bit further along now than is shown below, they have not been a top priority. Their design is a combination of the design provided on the plans for the Shearwater and the shape of the Pete Culler oars described in Wooden Boat Magazine, issue 71.20140704-184249-67369981.jpg

Ah yes, back to the boat itself. The gunwales. The lower edge is cut to rise at a 20 degree bevel instead of being cut to a rectangular cross section. They also taper down in both their height and width as they reach the bow and stern. Gluing them on was an all clamps on deck sort of occasion.

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To further stabilize the shape and departing from the plans, I decided to add breasthooks in each end. The pieces were glued together with 10 degrees of camber. The centerboard trunk and also 20140704-184750-67670958.jpg

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The light used to highlight gaps between the breasthooks and sheer planks also create wonderfully dramatic ambiance to work in. I highly recomend it.20140704-185156-67916139.jpg

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The mast step goes together in an example of “how many clamps can you fit in a small space?” The mast step also supports the sides and back of a mast trunk because the mast will be stepped through the deck of the forward watertight compartment.20140704-185157-67917041.jpg

Oh look, my trailer is here! 4 boxes, with one more to come. Some assembly required. I decided to bite the bullet and get a brand new SUT-250-S from Trailex. Included in this decision were the fact that the lightweight trailer would put less stress on my car, it would be better suited to carrying a lightweight boat, and whenever I end up selling the boat it may increase resale value. I thought about trying to get a used trailer, but the thought of dealing with repacking bearings or perhaps dealing with old wiring seemed like concerns I didn’t want the hassle of dealing with.20140704-185157-67917901.jpg

The bulkheads getting fitted along with deck framing. I decided to go with fairly large rectangular hatches to improve access to the compartments under the decks.20140704-185304-67984848.jpg

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Oh yes, and somewhere in there I had the pleasure of being able to assist a former professional sailmaker, as he assembled my lovely little sail. It looks awesome, and I can’t wait to see it hauled up my mast (which isn’t built yet)!20140704-183235-66755003.jpg20140704-183235-66755787.jpg20140704-185707-68227289.jpgAt this point things are looking slightly different almost every single day. The framing for the decks is nearly all fitted. As soon as those pieces are glued, I’ll be ready to fillet the joints, coat the interior of the compartments, and to paint the inside of the compartments before the decks go on. The slot for the centerboard is cut and the centerboard trunk is nearly ready to install. I’m getting ready to put the supports for the thwarts in. I’ll try to post updates more regularly as things progress. With summer progressing entirely too quickly, my current goal is to get it ready for rowing as soon as possible, with the sail rig soon to follow. Wish me luck!

Oh, one last thing: If you have any super nerdy questions, feel free to ask away. I skipped over many details of the process, but would be glad to share more information if anyone is interested.

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