By Mitch Booth - Hobie Cat 18 User Manual

Mast Set Up
Mast set up is critically important to the performance of the boat.
Firstly set the spreader rake to suit your crew weight. Spreader Rake is measured between a line between the tips of the
spreaders and the back edge of the mast (as shown diagram 1).
Spreader rake that is perfectly suited to you can only be determined by practice and experiencing different conditions
however this is what I go by as a rough guide:
40- 54mm Spreader Rake For Medium Heavy Crews (340 – 375 lbs)
55 -64mm Spreader Rake for Moderate Crews ( 310 – 340 lbs)
Over 65mm Spreader rake for light crews (under 310 lbs)
The principle is to increase spreader rake for lighter crews and reduce for heavier crews between this basic range.
Once deciding upon a suitable spreader rake tension the diamond wires. The diamond wires can be adjusted to suit the
conditions. The method I use to measure the tension is using a Wire Tension Gauge, which you can obtain from a local
yacht shop. Measuring the prebend is preferred by some people, but if you adjust the tension between races it is
impossible to measure the prebend. This is where the tension gauge comes in handy. The settings I usually follow are:
Under 36 for light wind (under 8 knots)
36- 40 for medium wind (8- 18 knots)
41 -45 for strong wind (over 18 knots)
Basically I wind the diamond wires up to depower (increases mast bend) and reduce diamond wire tension to power up
(reducing mast bend)
To test whether I have the correct mast set up I go sailing against another boat or boats and go testing. I look for height,
speed and power against the other boat. I find if I am slower than the other boat, possibly struggling to hold the boat flat
and having to point very high (assuming the other variables are eliminated) the sail is too full. Increasing Cunningham
and reducing rotation comes to a limit and if I reach the limit before reaching the same speed I increase the diamond
tension to further bend the mast. If still we are slow after reaching maximum diamond wire tension I then adjust the
spreader rake, which of course can only be done on the beach.
This then works in reverse also. If I find the boat is underpowered, maybe not flying a hull when the other boats are, or
feels sluggish and does not accelerate when even without Cunningham and maximum rotation, reducing the diamond wire
tension will help. But this also can only go so far and if the diamond wires become too loose you risk damaging your mast
so then reducing spreader rake is the go. This will straighten the mast and increase sail depth and therefore power.
Battens
I recommend using the battens supplied with the sail. The top two really should only need to be adjusted through inserting
slightly lighter or heavier battens depending on crew weight and conditions. Again it is the same, more power needed −
insert softer battens, too much power − insert harder battens.
The batten tension although not super critical should be done with some care.
I simply start at the top and basically pull the wrinkles out and then pull some more tension. Pulling the batten tension too
tight is not necessary.
Jib
Hobie University, NAHCA
Hobie Tiger - Tuning Guide

by Mitch Booth

Page 25
31 Mar 02