Merlin Rocket Tuning Guide
Some time should be spent in setting up the Merlin to ensure the rig is correctly calibrated and every
thing clearly marked. Doing this will make sailing the boat fast through the changing wind strengths a
much easier task. Speed Sails have put together this tuning guide to help you ensure you have your
boat set up correctly to get the best performance from your new sails.
Spreader Settings
A = 370mm
B = 135mm
The two measurements for the spreader are Spreader Length (A) and Spreader Deflection (B). Spreader
length controls the sideways stiffness of the mast and is taken by measuring the side wall of the mast to
the shroud. The deflection is measured by putting a straight edge from shroud to shroud and then
measuring to the mast from this edge.
Pre-bend
This setting is the most important and so time should be spent getting this correct. Pre-bend is
controlled by angling the spreader tips forward or aft. Angling the tips aft increases the pre-bend by
pushing the middle of the mast forwards. The spreader deflection gives a good starting point but may
need to be changed slightly to get the pre-bend exactly right.
We recommend sailing with a pre-bend of
25mm
. To measure this, set the mast rake on setting 0 (see
below) with rig tension of 250lbs. The pre-bend is then measured by pulling the main halyard tight
against the top of the gooseneck. The distance between the halyard and the mast at spreader height is
the pre-bend
Mast rake
For the rest of this guide we will refer to settings 0 as fully upright and setting 8 as fully raked. Below
is an idea of the conditions that fit each setting.
•
Setting 0
– Drifting conditions up to Helm & Crew sitting on the side deck.
•
Setting 1
– Helm & Crew sitting on the side up to both sitting out hard with mainsail still on
the centre line.
•
Setting 2-5
– Full power up to constantly over powered. (i.e. spilling the main to de-power).
•
Setting 6-8
– Constantly over powered to racing abandoned.
Initial set up:
1) Lowers and puller should be slack at all times
2) Rig tension on shrouds should read 27 on a Loos professional gauge
3) Top of mast to black band at the gooseneck should read 5720mm
4) Rake is measured from top of the mast to the top of the transom along the centre line
5) Throughout range rig tension remained unaltered
