Grapeview Point Boat Works

81 E Grapeview Point Rd + Allyn, WA 98524 + 360-277-9015 + boat_works@yahoo.com

Building a Glued Lapstrake Tirrik

Page 2: Lofting and setting up the molds

Lofting looking aft
Lofting looking aft

We lofted the boat last week. Lofting is drawing the boat full size in profile, plan view, and cross-sections. Iain Oughtred, the designer, provides paper patterns to make lofting unnecessary, but there are several advantages to lofting anyway. It allows the builder to better visualize how the boat is to be built, and anticipate problems.

As designed, the aft compartment is not large enough for storing the outboard motor the customer wants to use. If we raise the deck slightly (about 2") it should fit fine. That's good to know early in the construction process.

Lofting looking forward
Lofting looking forward

The lofting also gives us a chance to see how the centerboard fits into the trunk, and ensure the centerboard can rotate to the correct angles. It also allows us to determine how far the beaching rudder needs to pivot, and where to install the hardware.

Best of all, lofting ensures that if the parts are made to fit the lofting, they will all fit together on the boat. Parts made from paper patterns sometimes don't fit quite right, and without lofting the boat is is impossible to determine which of the parts is off.

The set of station molds
The set of station molds

Based on the lofting, we made the station molds that will determine the boat's shape. We like to build the molds out of pine, instead of plywood. The pine is nicer to work with, and the large openings in the molds make interior access easier. Plywood tends to warp, and doesn't hold up as well if the molds will be used to build other boats.

The station molds set up on the ladder frame
The station molds set up on the ladder frame

We set up the ladder frame that was used to build the Caledonia Yawl, this time with shorter cross members, since the Tirrik is about a foot narrower than the Caledonia. After aligning the molds to a string tightly stretched down the center of the ladder frame, the molds are screwed into place, and braces are installed to hold them perpendicular to the rails.

Centerboard pattern
Centerboard pattern

Yesterday we scarphed together two sheets of 9.5mm Shelmarine Okuome ply for the garboards. We also cut out the sections of the fwd and aft inner stems from African mahogany. These parts were epoxied together, and allowed to cure overnight. We also milled the keelson, and cut out the slot for the centerboard.

Today we assembled the keelson and inner stems onto the station molds, and beveled them to accept the garboards. This requires careful work with planes and spokeshaves, and usually takes a few hours to complete.

We also laminated the centerboard from two layers of 9.5mm and one layer of 6mm Okuome, epoxied together.




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