By Robert Ditterich - Geelong, Victoria - Australia

To Part One
To Part Two
To Part Three

A Pictorial Essay of a Navigator Build

The cockpit bulkheads are formed from the seat base, with a 9mm plywood arm overlapping it to form the stringer supports and the seat backs and side deck supports. Because the bulkheads are drawn at 1:5 scale and in two overlapping parts, I found it helpful to loft full sized sections to check measurements and enable accurate assembly.
Here the 20mm doubler has been glued (oversize to allow for fairing the hull into the transom) onto the 6mm transom.
20mm doublers added oversized, to allow for the flair of the stringers as they come away from the transom.
This bulkhead has double hatches to go either side of the mast. The workshop floor has gone back to bomb-site status after just a few bulkheads.
B2 having blocks attached to increase the gluing area behind the stringers- which are very curved at this point.
Because John has given bulkhead details as dimensioned 1:5 drawings, I found it helpful to loft the full sized outlines onto paper. This was particularly useful in fitting the two part cockpit bulkheads, enabling accuracy in fitting them together.
Trying out a good Polyurethane glue to reduce the amount of exposure to epoxy. It foams a little when going off, filling voids. You can see it around the edges.
Allowed myself the luxury of cutting the inspection hatch holes freehand this time, knowing that they'll be covered by the molding.
Here the symmetry and widths are being tested with a full width batten before the glue sets.
The two outer laminations have been roughly cut using the more finished centre strip as a template. The little piece of ply laying there will become a template to make the centreboard later. It is a half male template at the top and a half female template at the bottom.
Using the main stem piece as a template to shape the 2 doublers. A pattern routing bit (with a bearing) is used.
Never underestimate the potential of a spokeshave. My old friend in the background lies ready to help when machines are too clumsy.
Rather than using a template to rout the whole shape, I used the template to cut regular profiles across both sides of the board, and then used power and hand planes to take the surface down to the bottom of the profiles; less noise. The router is kept at a constant distance from the board, in the shape of the foil section, by moving over the 'bars'.
The shape was developed from a full sized section template, and the height was projected at many perpendicular points to the surface, and at a height sufficient to clear the bit at maximum depth
2 full sheets of 9mm ply are scarfed together for joining. The garboard (bottom) panel will be drawn...
John's design for hatch covers seems very good, but I couldn't bear to waste the cut outs from the hatch holes. Cut them neatly with a thin blade and it saves the work of making new infills. I have backed the holes with some thin ply.
These will help make a large volume of reserve buoyancy forward of the mast, while also allowing the stowage of gear.
This stringer becomes the support for the cockpit seat front panel, but also has the role of placing and supporting many of the bulkheads during assembly.
The keelson is 100 x 20. The dimension is cleverly incorporated into the CB design, so make it accurate.
Because this had a chip on the edge from striking a submerged screw in the previous boat build, I've used a coarse carborundum water stone to cut back the secondary bevel, removing the damage. This could have been done with a grinder, but for such a lovely blade, I prefer to grind by hand, with grit and water.
Several nice jobs grouped together help concentrate the mind onto the joys of sharpening.
Coarse carborundum stone used to remove chip on the secondary bevel. I will produce a straight, grey flat area which will become shinier as finer stones are used.
1200 Japanese water stone and honing guide removing the scratches from the bevel caused by the coarse stone used previously
Despite the camera distortion, that centre board (keelson) has parallel sides. This shot is in just because I liked the shapes and colours.
I include this because it illustrates the designer's method for creating 'x-y' co-ordinates for locating a fair curve on a grid. It works very well indeed, but because the horizontal axis starts with a value of 157 instead of 0, a builder using the edge of the ply to mark out the panel would waste almost enough to make the second panel. Expensive stuff, marine ply! I recommend either reducing all the relevant numbers by 157, or locate the ply on a backing board in such a way as to allow the bottom curve to start near the edge.
At bottom left, the slot for the stem is nominated and shown as 10mm, with 20 x 20 packers each side. The stem diagram, by contrast shows the stem width to be 27mm at this position. I chose to believe the stem diagram rather than this one. Note also that on another diagram the king plank width is shown wider for the yawl rig.
If the rebates that you cut in the bottom of the transom are snug and accurate, the transom will stand up by itself and reassure you that your careful placement of the stringers and keelson will have been worth the care and effort.
The old heavyweight is used to plunge cut along the 2 lines. The ends are cut carefully with a jigsaw, because there is framework under there and a blade hitting it end-on can give you a scare. Plunge cutting is worth practising on scrap if it intimidates you. A circular saw gives a much straighter cut than a jig saw can.

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