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Extreme Caulking by Paul Coster

Hello readers! We’ve decided to start posting regular updates on what we’ve been up to at the workshop and beyond. We are looking forward to sharing the excitement and activity with you. Community Boat Building is volunteer-powered, and so is this blog. Look for posts from a bunch of us volunteers, once a month.


The workshop is full of boats and busy at the moment with eight student boats being finished for Launch Day. Thankfully we've finished milling most of the parts for the rest of the boats, so we can focus on painting.


When we get the boats back into the Seaport shop from the schools, they are almost complete, but they still need a few little jobs done like sanding, installing seat beams, and adding oarpads before painting and, ultimately, getting them out on the water. The volunteers in charge of this process have these steps down to a fine art, but some tricky building conditions posed a few extra challenges that we have had to accommodate.


This year for the first time at one of our host schools, Harvard Kent, the students are building outdoors in a tent. This means not only that boat building comes to a halt as the weather gets colder, but also, as we recently discovered, especially humid weather can lead to unusually high water content in the wood used to build the boats. When the boats are brought back into the workshop at the Seaport, the planks dry out and contract. Accommodation of the wood's expansion and contraction is built into the design, but for two of the boats that are currently in the shop the contraction of the planks is more than expected and it's left quite a wide gap running the length of the boat. Normally the small gap that runs the length of the boat between the sheer and chine planks is beveled to be open on the outside but tight at the back, and this is filled in with a strip of cotton called caulk. The process of caulking is a rich part of the shipbuilding industry, and as we like to tell our students, Frederick Douglass was once a caulker in Baltimore. On bigger boats they would use hemp, but we use cotton string or batting. This still allows movement as the boat expands and contracts with humidity and with use, but in this case there was nothing to anchor the caulk on the interior side of the joint.


Our skilled volunteers Michael and Nicole solved the problem by cutting what turned out to be probably the world’s narrowest plank, a tiny slither of pine to run the length of the boat. They squeezed this spline into the gap between the two much larger planks. Once slotted in with wedges and glue, we planed the edge of this “micro-plank" flush with the surrounding boards and caulked as usual--a kind of hybrid planking and caulking that seems to tick all the boxes.


It’s one of the most interesting things about volunteering at Community Boat Building. Fifth graders aren’t necessarily always perfect boat builders, the lumber we are working with isn’t always perfect lumber, and in this case, building a boat in a tent in fall in Boston isn’t always going to go perfectly either. But it always inspires adaptability and creativity, and that’s part of what makes it such an exciting, fun and interesting project to be a part of. Come on out one night and join us!

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