Obtaining Profile dimensions for a Gaff
(this page)
When making a new spar, after deciding on the general dimensions, it is necessary to obtain detailed measurements of the profile and shape. These dimensions are then drawn on to the square or rectangular wooden blank from which the spar will be made. The shaping of the spar can then proceed.
This page describes how the detailed profile measurements for a replacement gaff yard were obtained using the 'Projection Method'.
See also Obtaining/Making a New Gaff describing how the gaff was constructed using the measurements obtained by the method described on this page.
Knowing the general dimensions of the gaff, the next problem was to obtain a series of measurements to achieve the 'double-taper' flattened profile.
The animated diagram (above) illustrates how the dimensions of the gaff were plotted. The notes that follow give additional information for anyone wishing to undertake a similar exercise in constructing a spar with a curved profile.
Each of the vertical lines defining the ten equal divisions ( 0 - 10 ) has a value where it intersects the curve of the circle. The ten divisions can now be elongated and projected to represent the half length of the gaff. Instead of a circle, the values define a new flattened curve shown in the diagram below.
Finally, this projection can be extended to the other half of the gaff to give all the measurements required for the full length. This is shown in the sketch below.
We now have all the detailed measurements required to construct the gaff. See also Obtaining/Making a New Gaff describing how the gaff was constructed using the measurements obtained by the method described on this page.