Twist measurement (part 2)

Main twist gauge

I've improved the twist gauges by putting the lollipop sticks onto a single length of wood. The idea is that the boat can be waved around at the side of the pond and the twist readings taken conveniently all at once, rather than having to clip and unclip a whole series of gauges. Alternatively, the boat can be positioned on its stand, and the settings photographed or video'ed.

For the main, the length of wood runs along the backstay, secured by a clothespeg at the backstay crane, and held at the transom by sliding the backstay's adjustment bowsie into a slot. The first picture shows the lower part of the main with a twist of zero; the twist measurement scales used start by assuming a 'normal' main sheeting angle of 5 degrees. If you squint hard, the middle batten shows a twist of around 13 degrees, and the top batten around 25 degrees.

There are two lollipop sticks for each main batten, joined at 90 degrees. They allow the twist to be read from either sighting along the backstay from the transom to the mast head while holding the fin, or sighting from the stern of the boat while it is on its stand.
Lollipop sticks on wood
For the jib, the length of wood runs along the forward face of the mast, secured at the base of the mast with a clip, and at the hounds by slotting the end of the length of wood and sliding it around the jibstay. The second picture shows the two lengths of wood involved, with sample lollipop sticks attached. The jib gauge has longer lollipop sticks, since the jib twist is measured relative to the topping lift with a 'normal' jib sheeting angle of 15 degrees. The jib lollipop sticks have their twist scales on both front and back, so that jib twist can be read off from the stern or the stem.

The lollipop stick scales are shown in more detail on the first page on twist measurement, which also gives two spreadsheets to make your own if you wish. The sticks are screwed, not very tightly, to the length of wood with one screw and a cup washer, to allow them to be rotated out of the way for storage and transportation.

2005-12-18