Don,
I think you meant this for Bob, who is trying to find a clever way
of determining the layline bearing.
Cheers,
Jeff Nelson
Muir Caileag
C&C 30 - 549
Armdale Yacht Club
On 2021-10-12 12:11 p.m., Don Kern via CnC-List wrote:
Jeff,
Let me assume that your boat is similar in performance to my 35 Mk2
and the wind / currents are similar to what we have in New England.
That said I hardly ever worry about sailing to the laylines. First,
hardly ever is the leeward mark set dead downwind and there should be
a preferred side of the course to sail which may be modified due to
tidal currents. You figure that out before you start and set the
pole and guy/sheet appropriately. Then you watch to see what lead
class of boats due upon rounding windward mark to confirm the downwide
course settings, if you are not in he fist class to start. When you
round that mark your fist imperative is to clear your wind either
reaching , bearing off or jibing. Next, if you are in the lead, is
cover your most threatening competitors, if not in the lead keeping
your wind clear and if wind is light to moderate sail to the favorable
current (max or min depending on current direction). Because of my
boat's older design I sail deeper downwind for max VMG then the newer
boats which sail closer to a reach (wider down wind angles). Strategy
and tactics usually will keep me away from the layline which limit my
options. If I am the lead boat I try set up so rounding is just get
the chute down and harden up without sailing into the lee of the
competitors. Normally because I have sailed deeper and have avoided
the laylines, the newer competitors are approaching from wider outside
angle and my tactic is to protect from being overlapped to the inside
as I get to the 3 boat circle.
From the above you can see I hardly ever sail off into the wild blue
yonders of the laylines, Strategy and then tactics predominate my down
wind sailing.
Don Ken
Fireball, C&C35 Mk2
Bristol, RI
On 10/12/2021 8:33 AM, Jeff Nelson via CnC-List wrote:
I'm really not following your math here.
Perhaps some clarification:
TWA = True Wind Angle (I think you refer to that as TWD True Wind
Direction below) ie 270?
Course = 230 deg
Tacking Angle = 80 deg
New Course = 310 deg
Course to Leeward Mark = ?
This statement is confusing to me:
"So, when the windward mark is at a bearing of 80* I'm on the leeward
layline"
In this example we are going to the Leeward Mark (downwind mark). I
believe you are heading to the port layline,
The windward mark would be the one you previously rounded.
With all of the above...It seems like an aweful lot of math to do in
the heat of the battle. Since you likely know the
course to the mark, and you've already determined your gybing range
(80 deg). Isn't it easier to add or subtract 80 to
your course to see if it matches the bearing to the mark? This can
be achieved from your chart plotter BTW (Bearing to
waypoint) or via handheld compass if you can see the mark. Maybe
that's what the math below does, if I plugged in
the right numbers, but the closest I could get was 180 - course (230)
= 310 but if I multiply that by 2 I get a course of
260 which wouldn't be your layline, as you need a course of 310.
Also, if I use any of those course numbers, they will
remain constant, whereas the bearing to the mark will constantly
change as you get further from the rhumbline (dead down wind).
Cheers,
Jeff Nelson
Muir Caileag
C&C30 - 549
Armdale Yacht Club
On 2021-10-11 10:07 p.m., Bob Mann via CnC-List wrote:
My geometry for calculating leeward layline:
If my ideal heading for the current conditions is 230* and TWD is
270*, that means my stern has to swing 40* to become dead downwind,
and another 40* to get to the reciprocal course after the jibe. In
a perfect scenario, this means an 80* swing. So, when the windward
mark is at a bearing of 80* I'm on the leeward layline. Bearing to
the mark can thus be calculated as 2 x (180-TWA).
Bob
On 10/08/2021 11:15 AM Bob Mann <sailrm...@comcast.net> wrote:
I still need to review the geometry, but I believe that when the
bearing to the mark is equal to 180-TWA, one has reached the
downwind layline. I also found that when the masthead is pointing
at the mark, that also indicates the layline has been reached.
Bob
On 10/06/2021 11:17 AM Jeff Nelson via CnC-List
<cnc-list@cnc-list.com> wrote:
Hmmm...Interesting question.
So, Ed's answer was pretty good, I'll add a few thoughts here:
AW isn't an ideal guide, True wind is what is needed so that you
can keep the angle to true wind to be constant on
either Gybe, assuming you know what the best angle is.
If you can find polar's for your boat, they will give you an idea
of ideal.
As Ed mentioned, VMG is your friend in determining what the best
angle is (especially if no polars are available).
You can experiment in different wind speeds to find a reasonably
good angle for windspeed and VMG.
Here's a good article to get you thinking:
http://www.oceansail.co.uk/Articles/VMGArticle.php
Hope this helps.
Jeff Nelson
Muir Caileag
C&C 30 549
Armdale Yacht Club
On 2021-10-06 12:02 p.m., Bob Mann via CnC-List wrote:
I'm fairly new to flying a spinnaker. I did it last weekend in a
race and I believe I overstood the mark as we were sailing 110 AW
before the gybe and 85 AW heading directly to the mark.
How does one determine when to gybe?
Bob
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