Mister Seldon uses this method
The folding rule
The following materials are required:
1. A 2 metre long measuring rod
(a folding rule
3. Vernier callipers
• Start with the cap shrouds only hand-tight. The rig is stayed
with the lower shrouds and the forestay and backstay.
• Tape the upper end of the folding rule to the starboard
. The lower end of the folding rule must be
approximately 5 mm above the upper end of the wire
terminal. Measure the distance between terminal and
folding rule exactly. This is index 0, let’s call it point A.
• Tension the starboard cap shroud
until the distance is
A + 1.5 mm between the terminal and the folding rule.
Measure using the vernier callipers.
• Leave the folding rule attached to the starboard shroud,
and move across to the port side and tension the shroud
rigging screw the equivalent amount.
• At intervals, check the starboard side to see how much
the folding rule has moved from the end terminal. When
there is a gap of A + 3 mm, the cap shrouds are tensioned
to 15% of the breaking load of the wire (3 x 5% = 15%).
If the mast
is not straight, adjust the lower shrouds, intermediate
shrouds etc. There is more information on this in
the chapter dealing with your rig type.
The folding rule method can be used on other stays, such
as the backstay and forestay (without jib furling
It can also be used for Dyform- or rod rigging, but please
take the difference in stretch into account compared to
1 x 19 wire.
Hint! Count how many turns on
the rigging screw corresponds to
1 mm elongation (5% of the
breaking load). Make a note of it.
This is useful to know if you ever
need to tension “another 5%”.
A+ 3 mm
1 x 19 wire Dyform Rod
5% of breaking load 1 mm 0.95 mm 0.7 mm
Stretch per 2 meter
More than one way to skin a cat.