Today’s video is what I called a case study. I’ll analyze some sail shapes I
recorded from one of our recent sailings. If you watched the first video of this season,
you know the primary goal I want to achieve is to improve the skills of sail trimming,
specifically how to set up the proper sail shape according to the circumstance.
This case study is about how to point higher in waves. Wind was 20 to 25 knot with the gust of 30
knot. Choppy sea. The target was upwind across the the Golden Gate Bridge with the max flood current
into the Gate, a little over 2 knots, against the sailing direction. We were sailing Beneteau 38.1
with in-mast furling main and furling jib. With 25 knot wind, the boat accelerated to
8 knots with heavily reefed main and jib in just a few seconds, however
it had trouble pointing in the waves with lots of leeways. This video is a little bit long,
so I split it into two parts. Part 1 covers the basics including what’s the proper sail shape
for both pointing and speed in strong wind, Part 2 is about why this sail shape failed to point high
in waves with wind around 25 knots and what kind of adjustments could be done to fix the problem.
Sailing across the Golden Gate Bridge is a classic upwind sailing.
We foot first, reach the max speed, then point. The higher the average VMG,
Velocity Made Good, the faster we could reach the bridge with less tacks.
As a new sailor, I find I am facing three challenges to achieve the better sail trimming.
Number one is the theoretical knowledge. First I need to familiarize myself with what sail shapes
are good for what conditions. In this particular case with wind 20+ knot, I put on the 2nd reef
and furled the jib to a small size. By the way, I am always on the safe side in terms of
reefing. Generally flatter sails with less draft, more twist on the upper leech in stronger wind.
As the wind strength increases, wind pressure moves the draft position further aft,
so luff tension needs to be increased to bring the draft position back forward.
In general, to accelerate, the boat needs a rounder luff entry, draft well forward,
fuller sail and open leech. On the other hand, a flat sail with flat luff entry and draft aft with
closed leech can maintain high speed and point high. When the waves are thrown into the equation,
a slightly fuller sail is needed to power through the waves. Easing the sheet a little
makes the bottom part of sail slightly fuller and bear off a couple of degrees.
When the sail ages like this one, its draft moves aft, making the aft part fuller
and hooked leech. A higher luff tension is needed to pull the draft forward.
Last but not least, both Katie and I are not very accurate helmsmen, especially in waves,
we need a wider groove or rounder luff entry to maintain the proper sail trim.
The second challenge is how I could achieve the proper sail shape on any particular boat.
Different boats have different sail plans, riggings, et cetera, et cetera. For example,
two of the boats I’v sailed have no traveler. One has in-mast furling main. None of them have
Cunningham. Only one boat has adjustable backstay, but I don’t know how to use it.
Unless the boat is full blown racing boat, there is always a limitation what can be done.
The last challenge is how would I know my sail shape is proper and the sail trim is correct.
The simplest way is using luff and leech telltales preferred on both jib and main,
from bottom to top. However, the reality as usual throws the curve ball. A furled jib loses its
telltales and in-mast furling main has neither telltales nor batons. Granted, a furled jib or
genoa has already lost its most efficient sail shape. In the future, I’ll try sail with the jib
or the main alone from time to time to see what they can do individually in various conditions,
then I may get a better understanding of how they can improve when working together. Basically it
takes lots of try and error to find out what’s the best to your own boat in different conditions.
OK, This is the end for the part 1. In the part 2, I’ll discuss
what adjustments we can do to fix this sail shape and make the boat point higher. Stay tuned,
I’ll see you in the part 2. In the mean time, enjoy the pacific sunset.