Tern was designed for this project by Tad Roberts (www.tadroberts.ca), a designer who lives and works on Gabriola Island in British Columbia. The "Exploration Ketch", as Roberts has dubbed the design, is meant to be suitable for long range expeditioning under power of oar and sail with a crew size of up to seven adults, although five is probably ideal. She is closely related to Roberts's earlier design, Ratty, a 20' daysailor and able camping cruiser. Our design was stretched to an overall length of 23'9''with a beam of 6'8'' and like Ratty, is based on the Drascombe designs of John Watkinson, of which the Lugger is the most widely known.
To accommodate our interests in traditional boat building and our need for a durable, relatively lightweight expedition craft, Steven Brouwer, our construction mentor suggested the Exploration Ketch be built with a mix of modern and traditional materials and building techniques. The frames and much of the interior layout are sawn yellow cedar, the stem is sawn fir, the dead wood is laminated fir, the centerboard, centerboard trunk, rudder and planking are all plywood. The foils, centerboard trunk and bottom two planks are reinforced with fiberglass and epoxy. But despite the occasional use of fiberglass and epoxy, we are essentially building a boat that is mechanically fastened and sealed with flexible adhesive marine bedding compound. The plywood planks are all fastened together with silicone-bronze machine screws, which allowed us to use relatively fast-setting Sikaflex in the seams.
We considered using sprit-rigged cat ketch, sliding gunter, or balanced lug (all good options) but ended up rigging the boat as a high-peaked gaff-rigged ketch with a high aspect jib. This option allowed relatively short spars, low center of effort and the ability to sail as high as 50 degrees off the wind. Six single-oar rowing stations power the boat when the breeze dies or the tide runs the wrong direction. Under full sail we occaisionally hit 7-8 knots and rowing with 4 or 5 oars in the water and one crew member on the helm we were able to sustain 2-3 knots in calm water. We frequently "motor-sailed" using several oars in addition to our sails. A small engine would probably move this boat along quite nicely but it's an option that has never been seriously considered; from the beginning we envisioned carrying ourselves to Alaska and back with only the wind and our own bodies to move our vessel.
You can find archives with pictures and descriptions of our building process on the "Construction Progress" blog.