|LUNA's Hull on Launch Day|
|T32x8 LUNA.. Note the eaves (mid-deck overhangs) and larger windows.|
Phil Bolger developed the Advanced Sharpie hull type, a descendant of traditional East Coast sharpies. It's distinguished from them by rectangular sections, bottom raised well clear of the water at the ends, and matched side and bottom curves (seen in profile and plan view, respectively).
Matching curves equalizes pressure on both sides of the right angle chine, reducing drag from turbulent cross-flow along its length. To match the curves without a long overhang at the bow (whose exposed bottom is prone to pound, it is clipped to the distinctive bow transom.
The high ends mean a short waterline, when upright, for nimble tacking. Heeled, the sailing waterline lengthens to almost full length, raising hull-speed accordingly.
Rectangular sections maximize form stability and reserve buoyancy, and simplify construction greatly. Chine logs are bent in gentle curves (no steaming or beveling), and all vertical lines are straight (no curves). Longitudinal components must be lofted or spiled (their curve transferred from the hull), but only once for any given area. Thus, a set of shelves in the salon, say, all have the same, longitudinal curve against the hull, rather than a different curve at each height.
We followed Phil's lead and designed LUNA for ply dimensions (vs. the trailer and slip constraints the AS29 was designed for). We used a simplified interior inspired by British Pilot Cutter layouts, blaspheming by adding a dinette. Junk Rig, outboard rudder, off-centerboards (leeboards prevented from winging on the windward tack). Went together relatively fast and cheap, and we lived happily aboard for 13 years.
Alas, we didn't insulate and overballasted (and/or under displaced). Probably would have lived with it, but wanted to check out TriloBoats. SLACKTIDE (our current T26x7) proved the concept to our satisfaction. On the drawing board, now, is LUNA, recast along TriloBoat lines.
TriloBoats carry AS construction savings to the bitter end. Rectilinear as possible, excepting only the ends, to let the hull slide forward. The cabins, especially, are designed to be fully rectilinear, so interiors may be installed square and true.
Where a sharpie (or any curved boat) carves displacement and volume with every curve, box barges stubbornly hang on to every cubic centimeter. Thus, on the same overall dimensions, a TriLOBOaTomized LUNA has half again the displacement (13500lbs vs 8300lbs).
I expect we'll lose some speed... rockered bottoms are said to be easier to drive, and I believe it. The long, barge dead-flat combined with right angle chines makes them slower turning. But SLACKTIDE has met our sailing needs with room to spare, so these are compromises we accept.
One could build an AB (Advanced Barge), by pinching in at the bow and stern to match bottom, end-curves. This would help keep transoms clear of the water when heeled, and eliminate that pesky cross-flow. I'm sure that it would improve performance. But each time, we talk ourselves out of it... the construction savings, bountiful deck-space and interior volume advantages make our cost/benefit analyses favor the simpler approach.
If we ever get to the point of building again, it'll likely be this design - LUNA's more ample sister.
SIP construction, lumber framed with selective tape 'n' glue, copper plated, Dynel/resin decks... maybe even resin saturated ply walls for easy maintenance in our golden years.
In the sweet bye 'm bye...
|LUNA's Rig and Layout... will repeat in T32x8 LUNA with more elbow room.|