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Old 25-07-2021, 19:14   #1
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Why is my tack angle so wide?

See attached GPS trace. We were trying to beat 25 knots wind (normal for San Francisco bay) to go out of the Golden gate bridge.

On the way out, we had to do a total of 14 tacks to reach the gate. My main issue is that the angle between our 2 tack directions is very large, at about 120 to 145 degrees. As a result we did not gain much distance westward between tacks. But we already were sailing upwind as much as possible , close hauled, the wind needle pointing right on the edge of the no-go zone wedge on top of mast.

I think normally I see the tack angle to be about 90 degrees. Why is it so wide today? Is it due to the flood (tide water running into the bay)
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Old 25-07-2021, 19:23   #2
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Re: Why is my tack angle so wide?

You are leaving out a lot of information. Were your sails reefed? What was the setting of the genoa track cars?

More, please.
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Old 25-07-2021, 19:27   #3
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Re: Why is my tack angle so wide?

An opposing current will have a dramatic effect on your tack angle.
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Old 25-07-2021, 19:40   #4
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Re: Why is my tack angle so wide?

It seems from you post that in lighter airs you have a smaller tacking angle. That is common to many boats, so one of the things we need to know is just exactly what boat you sail.

The first thought that occurs to me is that you were trying too hard. You were probably over canvassed and over trimmed. One indicator of the former is angle of heel, so perhaps you can tell us, once you've told us what the boat is, how hard you made her heel, nd what amount of canvas you carried. As far as over-trimming goes, just ease sheets till you get a suggestion of 'loosing your luff" while you are holding your heading. Then harden sheets JUST enuff to kill the luff.

The trick is to keep 'er footing. Once you lose speed you will also loose tacking angle.

So tell us what boat it is.

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Old 25-07-2021, 19:46   #5
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Re: Why is my tack angle so wide?

Knowing the area, I am sure it was just the current. It can reach 6 knots under the Golden Gate. If your VMG isn't at least equal to the current, you aren't going anywhere. And there is plenty of current elsewhere on the Bay. You do have the tide tables, I assume? The prediction of the currents is in there, too. Let us know.
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Old 25-07-2021, 20:00   #6
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Re: Why is my tack angle so wide?

Ah, yes, forgive me OP was talking about his TRACE!

Well, to me "tack angle" is the difference in HEADING when you are sailing properly on one tack and then go about to the other tack and sail properly on this new tack.

That has nothing to do with TRACE whatever since trace must necessarily be influenced by tidal current.

Best not to get too fixated on the Garmin :-)

TP
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Old 25-07-2021, 20:07   #7
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Re: Why is my tack angle so wide?

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Originally Posted by Dr. D View Post
You are leaving out a lot of information. Were your sails reefed? What was the setting of the genoa track cars?

More, please.

Thanks, my boat is a Beneteau First 36.7. Don't know the model of the main. Jib is a small jib. No reefing. Trimmed pretty tight
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Old 25-07-2021, 20:12   #8
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Re: Why is my tack angle so wide?

Yeah max flood is 12pm we reached the gate at about 1:30
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Old 26-07-2021, 00:57   #9
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Re: Why is my tack angle so wide?

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Yeah max flood is 12pm we reached the gate at about 1:30
So (loosely) you would have had 1 hour of slack water and by 1:30pm, you were on the beginning of the ebb (falling/outgoing) tide.

I don't know what the tidal curve looks like for your area (the strength of a falling tide can sometimes be at the beginning of the change in direction), but if you were tacking into it, each time you presented the beam of your boat to the tidal stream (as in tacking), it naturally incurred tidal leeway - which, as you discovered, made your tacking angles turn to merde!

One of the ways to minimize tidal effect is get out of the deep water to something shallower. For instance, often there can be back-eddies along the shoreline that will assist in running opposite to the tide - but that's really a local-knowledge thing.

Something like you describe will also happen if you ask a helmsman to steer towards a fixed item on shore. With tidal leeway acting on the keel, suddenly the helmsman can't figure out why they can't hold that course/angle anymore. This is why seamanship dictates providing a compass course heading...

Anyway, we all learn this one the hard way - once. Ignore tides at your peril!

Fair winds,
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Old 26-07-2021, 01:22   #10
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Re: Why is my tack angle so wide?

Quote:
but if you were tacking into it, each time you presented the beam of your boat to the tidal stream (as in tacking), it naturally incurred tidal leeway - which, as you discovered, made your tacking angles turn to merde!
Actually, the attitude of the boat (as in "beam to the tidal stream") doesn't affect the tidal drift. The whole body of water is moving, and one is swept "down stream" equally, no matter what your heading might be.

But I agree t hat his poor progress up tide was surely due to the effects of the flood entering the gate. Something one learns about early on if racing in SF Bay!

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Old 26-07-2021, 01:28   #11
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Re: Why is my tack angle so wide?

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Actually, the attitude of the boat (as in "beam to the tidal stream") doesn't affect the tidal drift. The whole body of water is moving, and one is swept "down stream" equally, no matter what your heading might be.

But I agree that his poor progress up tide was surely due to the effects of the flood entering the gate. Something one learns about early on if racing in SF Bay!
They were going opposite to the tide, Jim.

"Max flood was 12pm"; they hit tidal gate at 1:30pm.

Yes - whole body of water was moving - in the opposite direction, while they were effectively trying to tack "up" it.
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Old 26-07-2021, 02:06   #12
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Re: Why is my tack angle so wide?

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They were going opposite to the tide, Jim.

"Max flood was 12pm"; they hit tidal gate at 1:30pm.

Yes - whole body of water was moving - in the opposite direction, while they were effectively trying to tack "up" it.
Yep, they were goin' up tide, but what I was talking about was the statement that it was only when going about that the tidal effect was to be noted. This is a common belief, associated with thoughts about "lee bowing".

Having done a lot of races starting at the St Francis and going out the gate, I'm pretty aware of tidal effects in those waters.

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Old 26-07-2021, 02:18   #13
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Re: Why is my tack angle so wide?

...the main reason is:
boat is a fin-keeled, spade-ruddered Bendytoys Bermudan sloop.
If it were a seakindly, full-keeled gaff ketch otoh...
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Old 26-07-2021, 03:05   #14
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Re: Why is my tack angle so wide?

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...the main reason is:
boat is a fin-keeled, spade-ruddered Bendytoys Bermudan sloop.
If it were a seakindly, full-keeled gaff ketch otoh...

Hahaha, only if the full keeled started it's donk.
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Old 26-07-2021, 04:18   #15
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Re: Why is my tack angle so wide?

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Originally Posted by Yangyangyyy View Post
Thanks, my boat is a Beneteau First 36.7. Don't know the model of the main. Jib is a small jib. No reefing. Trimmed pretty tight


I’m thinking you were losing ground to the current.

But….were your sail trimmed correctly?

You’ve described the no go zone on the indicator (toss it out) and you’ve described the small jib being trimmed really tight.

Were your telltales all streaming? Was the Genoa car set to keep the leech of the headsail consistent and the belly of the sail flat?

Was the leech of your main cupping? Outhaul tight?
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