Classic_Boat_2016-06

Left: Begin sawing with the teeth pointing down.

Above: Saw with a two-handed grip and teeth

pointing forward after establishing the kerf

Boatbuilder’s Notes

CRAFTSMANSHIP

Overhand ripping

Contraction rule

The development of foundries in British shipyards brought with it the

trades of founder and pattern-maker. The founder’s job was to make an

accurate sand mould into which the molten metal could be poured. This

mould was made by placing a wooden pattern of the required metal

part in a box and filling the space around it with sand. Then the metal

poured in. But because different molten metals contract by different

amounts as they cool and solidify, the pattern-maker had to make the

pattern slightly oversize in proportion. This was done by applying an

allowance using a contraction rule with graduations engraved. On this

rule, for iron and steel made by Chesterman, Sheffield, the 12in

contraction scale marked 1 in 96 is intended for casting iron and is

actually 12^1 / 8 in long, while that marked 1 in 48 is for casting steel and

is 12¼in long – since iron and steel contract by^1 / 8 in and ¼in,

respectively, on cooling. Robin Gates

TEXT AND PHOTO ROBIN GATES

The boatbuilder of a certain age whose back protests at the prospect of ripping a

long or tough piece of timber by hand could benefit from the overhand ripping

technique once favoured by cabinet makers.

Instead of bending over the timber with a knee and a hand to stabilize it on the

sawing horse, and sawing with the teeth pointing back towards the worker, overhand

ripping is accomplished standing upright at the bench with saw teeth pointing forwards.

The work piece is clamped securely overhanging the edge of the bench. The kerf is

then established with teeth pointing downwards, and the toe of the saw tipped slightly

above horizontal, before the saw is turned around and used with a two-handed grip

cutting away from the worker. Some experimentation is required to find a comfortable

grip and the most efficient angle and degree of pressure for the saw and timber.

Since it is more difficult to develop downforce the

saw needs to be sharp and not too coarse. This is a

1950s Spear & Jackson Sovereign with six teeth per

inch ripping^3 / 4 inch mahogany. Aside from being

easier on the back and the knee, the overhand

ripping technique may offer better control and

accuracy through its improved sighting of the line.

Clamping the timber to the long edge of a work

bench also removes the need to constantly readjust

its position as the kerf progresses, as the worker

simply moves forward with the saw.

Veneer hammer

Veneering yacht furniture has been common practice since

Victorian times. An attractively figured timber in short supply will go

further if used in thin veneers over a core of less expensive timber.

The core timber might be selected for stability, since the rare timber

cut primarily to display its grain might warp or split if used alone

inside a yacht subject to wide fluctuations in temperature and

humidity. Or the core may be chosen for lightness on a racing yacht

or flexibility to accommodate a designer’s flighty curves. When

veneering was done by hand the veneer was brushed with hide glue

then positioned on the core timber and the veneer hammer was used

like a squeegee, pushed back and forth across the veneer. This typical

user-made example has a heavy brass plate. Note how the brass edge

is tapered to maximise pressure.

ROBIN GATES ROBIN GATES