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  1. #1
    Join Date
    May 2012
    Location
    Second Coast, Ross-shire, overlooking Gruinard Bay.
    Posts
    7,380

    Default Have I been fooling myself all theses years - assuming tacking at 45° to the wind

    My Plotter showed a track of tacking at about 85°; sailing at 47°- 48°off the wind, even though my Windex indicated very close to 45°.
    I am aware of apparent wind affecting the pointing of the Windex.

    I accept wind/tide/hull performance will affect the true direction when beating, to some small/greater degree, but have I been fooling myself all these years when planning a course that I would tack at 90° and beat at c. 45°, or even closer in perfect conditions?

    Last evening I had a very enjoyable sail in F3/F4, slight sea and not healing very much (nowhere near lee-rail under). Speed for the two hours was between 4kts and 6.5kts over the ground with little tide in the Bay.
    Beating back to my mooring my plotter track was noticeably "off" 90°at each tack. Speed over the ground circa 4kts
    I can't say I have noticed this before in such good conditions.

    Boat is a 9m sloop, 3 tons displacement with fin keel and skeg/rudder. 6.7m waterline, 2.7m beam.

    Has something changed with the boat, or have I had this principle wrong for decades?
    Kay Sarah Sarah
    57°51.42' N 5°29.44' W

  2. #2
    Join Date
    Nov 2006
    Location
    Ardfern and Malvern
    Posts
    213

    Default Re: Have I been fooling myself all theses years - assuming tacking at 45° to the wind

    That does not seem surprising to me.
    It doesn’t take much deviation from “perfect conditions” to lose you a degree or two on what you hope for when you tack.
    You were heeling and every degree off the vertical will increase your leeway a little. Some tide and some waves also will have had an effect. The end of season may mean more fouling on the yacht’s bottom too.
    If your basic assumptions had been far out you would have noticed long since that you were not laying points you hoped to round, so they are probably sound so long as the countervailing factors are always borne in mind.

  3. #3
    Join Date
    Jul 2018
    Location
    Bewdley, Worcs
    Posts
    511

    Default Re: Have I been fooling myself all theses years - assuming tacking at 45° to the wind

    Windex indicating 45degrees off wind? That would be close to a beam reach with apparrent wind.

    Tacking 45 degrees to windward in "normal" conditions, I would expect my windex to indicate roughly 30 degrees. My windex is (roughly) set at 30 degrees each side (60 degrees total) and works pretty much spot on in most conditions to give a close hauled 45ish degree beat to windward.

    If my windex was indicating 45 degrees I would expect to be a long way short of close hauled ... possibly as far as a beam reach.

  4. #4
    Join Date
    Nov 2015
    Location
    Portsmouth
    Posts
    232

    Default Re: Have I been fooling myself all theses years - assuming tacking at 45° to the wind

    45 degrees pointing to the wind plus 3 degrees leeway gives you the 48 degrees of your plotter track. spot on.

  5. #5
    Join Date
    Jun 2015
    Posts
    1,726

    Default Re: Have I been fooling myself all theses years - assuming tacking at 45° to the wind

    What was the tide doing at the time of your plots? You can only trust the compass (or fully correcting instruments) to give you your tack angle. My Windex sits at about 25/30 degrees, and on a good day my tacking angle is about 80/85 degrees.

  6. #6
    Join Date
    Dec 2003
    Posts
    5,546

    Default Re: Have I been fooling myself all theses years - assuming tacking at 45° to the wind

    Quote Originally Posted by Robert Wilson View Post
    My Plotter showed a track of tacking at about 85°; sailing at 47°- 48°off the wind, even though my Windex indicated very close to 45°.
    I am aware of apparent wind affecting the pointing of the Windex.

    I accept wind/tide/hull performance will affect the true direction when beating, to some small/greater degree, but have I been fooling myself all these years when planning a course that I would tack at 90° and beat at c. 45°, or even closer in perfect conditions?

    Last evening I had a very enjoyable sail in F3/F4, slight sea and not healing very much (nowhere near lee-rail under). Speed for the two hours was between 4kts and 6.5kts over the ground with little tide in the Bay.
    Beating back to my mooring my plotter track was noticeably "off" 90°at each tack. Speed over the ground circa 4kts
    I can't say I have noticed this before in such good conditions.

    Boat is a 9m sloop, 3 tons displacement with fin keel and skeg/rudder. 6.7m waterline, 2.7m beam.

    Has something changed with the boat, or have I had this principle wrong for decades?
    Makes sense with a little bit of tide running with you.

    It works like this: without STW data I'm assuming 5kts boatspeed, 11kts TWS, and an AWA of 40 degrees close hauled. I'm guessing that is reasonably close to your boat.

    Close-hauled, that would translate to an AWS of 14kts, a TWA of about 58 degrees, and a tacking angle of 115 degrees. A foul tide would open that further.

    Perhaps when you turned to beat back to your mooring you simply lost that small favourable tide and the tacking angle opened quite a bit? If so, nothing untoward going on there.

  7. #7
    Join Date
    Feb 2007
    Location
    Essex
    Posts
    22,866

    Default Re: Have I been fooling myself all theses years - assuming tacking at 45° to the wind

    45 degrees is a sort of rule of thumb for a well set up boat in good conditions but many boats fail to achieve this for a variety of reasons, such as poor sail shape, poor helming and an awkward sea. Modern racing boats will do considerably better though, and my impression is that larger boats generally do better than small ones.

    A windex is useful, even essential, but sailing to it too exactly can be inefficient. The only way to find out if one's upwind sailing is up to scratch is to race. That, of course, is the road to perdition.
    Far away is near at hand in images of elsewhere

  8. #8
    Join Date
    Dec 2003
    Posts
    5,546

    Default Re: Have I been fooling myself all theses years - assuming tacking at 45° to the wind

    Quote Originally Posted by johnalison View Post
    45 degrees is a sort of rule of thumb for a well set up boat in good conditions but many boats fail to achieve this for a variety of reasons, such as poor sail shape, poor helming and an awkward sea. Modern racing boats will do considerably better though, and my impression is that larger boats generally do better than small ones.
    Racing boats will better 35 deg AWA, but then they go faster which kind of backfires in the tacking angle sense.

    Imagine a TWS of 10kts, sailing at 7kts STW, at an AWA of 35 deg. That translates into an AWS of 15kts (boat fully powered up), a TWA of almost 60 degrees, and a tacking angle still at 120 deg!

  9. #9
    Join Date
    May 2012
    Location
    Second Coast, Ross-shire, overlooking Gruinard Bay.
    Posts
    7,380

    Default Re: Have I been fooling myself all theses years - assuming tacking at 45° to the wind

    Thank you one and all.
    Just about to start supper, so I'll read through again, digest and then comment.
    One point; my mainsail has too much "bag" in it because I have difficulty keeping the luff tight. My Cunningham improves it greatly.
    I may have to get a new Dyneema type halyard or revert to my previous wire halyard.
    Kay Sarah Sarah
    57°51.42' N 5°29.44' W

  10. #10
    Join Date
    Apr 2007
    Location
    West Coast
    Posts
    2,405

    Default Re: Have I been fooling myself all theses years - assuming tacking at 45° to the wind

    Maybe your new crew is not tweaking the sails right, more training?
    Chris
    Out west.... (or in the office)

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