FEBRUARY11, 2025
CHALLENGING CHILLY
CONDITIONS
The final prediction was for winds up to 17 knots but with
an ominous warning about “chilly conditions”.
The biggest question was about entrance conditions. I called the harbor
on Monday and the person that takes the soundings said he was not able to get
readings because of the heavy anchovy
presence in the harbor. I was
disappointed but got a call from the same person on Tuesday that a reading was
taken and posted which was a huge boost in confidence. We could at least get some smaller boats out.
Whether the entrance
was too risky or the chilly conditions were the cause, we had only four boats
that came out with one retiring before the start. We established a start line in an area close
to Blacks and called for a course to round Mile to port and finish with
southern end of the start line to port. Finish line being an extension of the
line from lighthouse through the end of the line. Some boats were slow getting to the start
line area so we blew the horn at 3:35 for a 3:40 start.
The conditions for the beginning of the race saw winds over
20 knots which intensified the “chill factor”.
As the race started, we saw the wind drop to15 to 17 knots but we kept
the reef in anticipating more wind outside which played out as
anticipated. Pair A Dice was first
around Mile followed by Big Mac and Kicks.
On the way back to the finish line it was difficult trying to find the marks
we had set. At the finish it was Pair a
Dice first 34:14 followed by Big Mac
34:42 and Kicks 47:37. Times are elapsed and the course distance
was 2.59 NM.
Despite the chill in the air which we all had dressed for,
it was great to see three boats finish in such challenging chilly conditions.
PHRF CORRECTED RESULTS
PLACE BOAT PHRF CORRECTED TIME
1 BIG MAC 222 25:06
2 SAILING
PAIR A DICE 180 26:28
3 KICKS 180 39:48
RACE QS:
The track for this evening can be reviewed at:
TIDES AND THE RULE OF TWELFTHS:
Because of our shoaling harbor entrance tides play a large
factor in our ability to get out of the harbor.
But tides affect many factors for different reasons in different
areas. Tides play a huge factor in
anticipating currents in the San Francisco bay or currents in reef passages in
the tropics, it’s good to know about the rule of twelfths to anticipate how
strong currents will be at a certain time or to estimate accurately the water
height at a certain time. I believe Ernie Ridout was the first to inform me
about this over dinner years ago and I used it extensively when I had to
tabernacle to get out of the upper harbor.
In essence, high tides and low tides are about 6 hours
apart. The difference between High and
low tide varies according to the alignment of heavenly bodies. Using the rule of twelfths, you take the
difference between high and low tide. As
an example we will use a difference of 6
feet which is about what we may get in Monterey bay. We divide this distance by 12 which gives
increments of 6 inches. The progression
of the rule of twelfths is that the first hour after high or low tide will give
a 6-inch difference (for this example) in water height. The second hour will
give 2/12ths (1 foot difference). The
progression for each hour using the rule is:
1/12, 2/12, 3/12, 3/12, 2/12, 1/12.
This means that the most rapid change is halfway between high and low
tide with the change being 3/12 (1.5 feet in this example) for each of the two hours encompassing the time in the
middle of high and low tide.
Below is what it looks like if there was a 6 METER
difference between high and low tide.
I hope this helps us all in dealing with our harbor
shoaling.
Barry Keeler
Sailing Pair A Dice
