Caulking the tween deck

Jamie and Matt have been working the tween decks lately. The caulking needed to be replaced and many of the seams were so open that they needed feathers. We’ll start with Jamie working out the widths they’d need to feather the seams.


He uses wood scraps of different measured thicknesses to measure the gap width along each seam.


The nail set crosswise in the scrap keeps the scrap from falling through the gap.

With these measurements in hand, they make up a whole bunch of feathers to fill the gaps. The feathers are snug at the bottom of the deck planking but have a bevel along the top two thirds to allow for caulking.

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After the feathers are installed, it’s lots of caulking. We use oakum (hemp fiber treated with pine tar) to caulk.

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You can see the feathers alongside the caulking.


Roger and Rob, both master caulkers, came down to help.


Driving the caulking into the seam is a two step process. First the caulking is set into the seam using a series of short tucks that are driven lightly with the mallet and iron.


Then the caulker goes back over the area he just tucked and drives the caulking hard down into the seam.


Once your supply of oakum runs out, it’s back to the shop to spin some more. The oakum comes from the supplier in thick cords, and the crew pulls and rolls these cords between their palm and thigh to create a consistent, thinner rope.


It’s not a bad place to be on a cold day with the heater and radio…

Once the caulking is driven, we want to protect it from dirt, water, and any other contamination as quickly as possible. This is particularly important in the areas where museum guests will be walking. The final step in caulking the decks is to seal the seam with hot (really, really hot!) tar. We start by paring the feathers down to the level of the driven caulking.

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Rob got the tar good and hot (outside the boat of course), and Jamie and Matt loaded up their tar funnels.

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Pouring the tar into the seam is tricky work. When it first comes out of the pot, it’s as thin and runny as water.


Matt and Jamie move along the seam, trying to get just enough tar to completely fill the seam, but not so much as to puddle out around it. It’s tricky work. As the pour progresses, the tar cools and they get a brief sweet spot of time where the flow is steady and controllable, like a thin milkshake.


Soon, the tar cools enough to stop flowing easily, and it’s back to the pot for a refill.

After all the seams are filled we let the tar cool overnight. Given the frigid temps, we could have probably gotten away with just an hour or so.


The next day, we scrape off the excess tar, leaving a nice straight seam.


The seams to the right have been scraped.

Once the primary traffic areas have been addressed, it’s back to work on the perimeter of the tween deck.

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Next up, more new masts!