I'll be interested in your geometry review. Seems to me both of those
(certainly the latter) would put you directly
upwind of the mark. Which in most cases would not be the layline,
unless you are going dead down wind.
I would think that if your course was 10 deg and TWA was 180, Then the
layline would be when the mark bearing
was (170-TWA) Mod(360) or 190 - TWA as you're able to sail 10 deg off
dead down wind and therefore gybing through 20 deg.
Food for thought.
I'm assuming when you say masthead is pointing at the mark, you mean the
back end of the pointer, as I would
imagine the arrow is pointing somewhere aft indicating your apparent
wind which should be forward of your stern
a bit....
Cheers,
Jeff Nelson
Muir Caileag
C&C 30 - 549
Armdale Yacht club
On 2021-10-08 12:15 p.m., Bob Mann via CnC-List 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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