BOAT DESIGN QUARTERLY - NO. 19
ANNAPOLIS WHERRY™: QUICK IN THE SHOP, FAST ON THE WATER by Mike O'Brien
On a cold day last Spring, Chris Kulczycki, of Chesapeake Light Craft, arrived at the WoodenBoat waterfront with a new lapstrake wherry. The 17'9" x 3'2" hull showed striking lines and a clean, virtually frameless, interior that suggested glued plywood-lapstrake construction. We launched the boat into the tail end of a passing cold front, which still had enough punch to kick up a sharp 15" harbor chop.
Despite its modest inertia, the 65 lb Annapolis Wherry™ cut easily through the steep waves with little loss of momentum during recovery. Stability seemed all we might expect from a boat of this purpose. She's steadier than a Bangor Packet but not in a league with a working Whitehall. (Of course, the Whitehall on its best day couldn't keep pace with this wherry.)
We can row this boat from a fixed seat, or we can drop in a sliding-seat unit. The specified Piantedosi RoWing is elegant in concept and execution.
As its appearance suggests, this hull is a glued plywood-lapstrake structure -- but there is a difference in assembly, a big difference. CLC's CNC machine not only cuts the expanded planks to shape, but it works a constant 90-degree rabbet into the inside lower edge of each plank. The square outside upper edge of the adjoining plank fits into the rabbet, and all is held together by wire ties in stitch-and-glue fashion. Ah, but you say there is no rolling bevel; therefore, the planks cannot mate perfectly. You are right.
Using a plastic syringe containing epoxy mixed with silica, we'll fill the voids at the plank laps. Working from the outside of the inverted hull, we'll inject the epoxy along the length of each lap. Gravity will prove a capable assistant. As do all glued-lapstrake hulls, this one absolutely depends upon the gap-filling adhesive strength of epoxy and the uniform cross-grain strength of a high-quality plywood sheet. If we plank this sparsely framed hull with cedar (or any solid timber), it will split along the laps -- perhaps not today or next week, but soon and catastrophically.
How does this new LapStitch™ building technique compare to common stitch-and-glue construction? The LapStitch™ boats, in kit form, require less time to build -- particularly if we're after achieving a yacht finish. Considerable fillet fairing and sanding are eliminated. And many of us prefer the appearance of a lapstrake boat. The shadow lines cast at the laps accentuate sweet hull lines.
Is a LapStitch™ hull ultimately as strong as a similar multichine stitch-and-glue hull? Perhaps not. After all, we're comparing simple glue joints to well-radiused epoxy fillets covered with fiberglass. Yet we've had year's of experience with Joel White's Nutshells, Shellbacks, and Shearwaters (all glued plywood-lapstrake boats); and they have aged well. The point is that these glued-lap hulls seem plenty strong enough. Belt-and-suspender types among us might be inclined to run fiberglass tape along the inside surface of each seam. If we do, Kulczycki will think us foolish.