Ply: Sides, bulkheads 12mm, decks 2x6mm, furniture 6-12mm.
Dory hull bottom-soles, daggerboards 25mm Hardwood or marine ply.
Total ply is 1 cubic metre or 640kg.
Dry weight one ton without crew, cruising two.
Dimensions (ft) 28/28 x 5/18 x 0.8 @ 2tons.
HR max 53 in.
Suggested fractional rig with 100% FT on 30ft woodwing rotating mast with
swept back shrouds to outer of hulls and forestay to front beam. Roachy fully battened
main. Total 500 sq ft.
Cut and assemble main 4 bulkheads and transom from 12mm ply and 50 x 12mm HW.
These are flat bottom. Sides 25mm flare in (no 1), straight (#2), curve out 25mm(3,4) and
the transom is a rectangle 3ft wide and one 9.9HP long-shaft OB leg high. Deck profiles
are circle sections curved on various radii very close to 3ft 6in (see station dwgs) and
easily lofted with pencil and string. Highest is 15ins above sheer @ Saloon/Cockpit
interface (NB no companionway to "Galley" Saloon, maybe to "Nav"
Saloon. This is not a design you want full of water, as slatted floor is the only bilge in
saloons.
Scarf and cut 25mm bottoms 28ft long triangle, stern 3ft triangle base. Plane
edges from vertical stem (12mm wide tip) and stern using bulkhead angles.
Scarf 12mm sides, cut just over 28 ft long. No other cuts. Tack temporary chine
logs on sides to position rocker, which is flat under saloon rising 10in. to bow/stern.
Clamp and glue 75x12 stem-piece between sides leaving a 28ft long 4ft high
plywood Vee shape (viewed from above) self-standing upside down on the floor.
Fit the bottom into this, positioning down onto temporary chine logs, and
minimally tack sides to bottom planed edges (2x28ft of join).
Fit transom. Remember we are building sailing way-up.
Fit bulkheads, checking that this will true up any twist. If not brace the
twist out. Here high quality ply will pay for itself.
When satisfied with true run thin epoxy into all joins. Repeat when dry.
Fit permanent chine logs between bulkheads.
Measure cut and fit extra bulkheads 9inches from 1,2 and 4. Fix by sandwiching
9 inches of straight (Xbeam) lumber running sheer to sheer with the fixed companion
bulkhead. You now have your 3 crossbeam slots.
Fit beam-lashing cleats (with backing plates), even if you think you are going
to bolt crossbeams (see below). You’ll use them (tie up dinghy, tie up boat, raft up,
tow log, jury rig, tie down/craning point for demounting.
Fit furniture - seats, tanks, battery rack under berth, & berth base(38 x
96in). Put in cockpit floor/seats with slope to boat CL and 40mm drain..
Roll over hull with ceiling beam block and tackle. NB max girth < 16ft.
Trim excess sides to bottom , sand and fair, glass bottom & sides, paint,
roll back. Glass carefully around cleats to strengthen. Glass cockpits.
Deck it all (except 5 x 5ft cockpit & the 9in crossbeam slots) Stringers, 2
layers of 6mm ply will take the curve. Crossbeams will break up your eye if deck is less
than perfect and you can even throw extra height in the saloon, which is
isolated visually at deck level (between beam & cockpit).
Build crossbeams. Note their size is a bit arbitrary, the main one is 18 in
deep and you may want it 12in wide instead of nine.
Carefully glass beam slots, it’s a rot point. Glue hard rubber mats in
bottom.
Crossbeams can be bolted through hull bulkheads with one big SS bolt (flex) or
2 smaller (rigid). Use ply washers to spread the load, lots of epoxy, and wall the holes
with SS or plastic pipe. Reckon this will leak slightly. If you cant live with that
don’t do it, lash the beams (semi-rigid) to either side of each hull using multiple
loops of 6mm high quality nylon round cleats mentioned above.
Bolt 24ft long 12"x 1" plank in position up centreline. This is for
tramp fixing, walking forr’d, and is your mast-step, enabling you to rig the boat any
way within reason including 2 masts. The mast-step plank provides the flexibility to use a
much cheaper 2nd hand rig. Fitting this plank will have to be incorporated in design as
the crossbeams vary in depth, the main one tall enoghto provide some safety and shelter
for the bridgedeck.
To gain the additional foot of length in the stateroom(s) you
can
1/ move the beam/ bed forward (this narrows berth 1.3 inches
unless one increases the main b/head beam, which also widens seats.)
2/ move the cockpit back
3/ lengthen the boat to 29ft without needing more ply for sides.
4/ Slope the rear cabin bilkhead to the rear at the top. This creates both a
backrest angle for the cross-seating in the saloon, and a foot-space so one can stand up
to the windscreen in the cockpit-in effect it gives an extra 6 inches in both cockpit and
saloon.
Option 1 appeals as it is best structurally, plus simplest.
Option 4 would also definitely be adopted by the author.
Design C105 is a good result against Dick Newick’s well known
Designer’s aim of comfort & high performance at low cost.
It should be remembered in the assessment of intangibles that the
folk this design are intended for are satisfied with the basics of food,
warmth and shelter rather than a glut of fashionable rubbish.
Though comfort is relative, performance and low cost are absolute
and this boat delivers both, especially with labour evaluated as a cost.
C
Jeff Gilbert Design
July, 2000
