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Old 25-11-2020, 18:44   #1
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Best time to mark: using AP or by hand?

Say I want to go 20mi to a mark. I want to make it there in the least time. I don't need to tack.

Would you:
a. Put the mark in as a waypoint, then use the AP in nav mode (so it takes into account set/drift) and just trim the sails as the boat steers itself

or

b. Hand steer it using AP while following xtrack error and minimizing it yourself

c. Just hand steer the course making minor corrections for sail trim.

I would think C least efficient, A is probably the best, but my AP wanders quite a bit. My B&G has nav/sail mode as well.

This is for friendly weekend racing, to buoy and back.

Thanks.
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Old 25-11-2020, 20:05   #2
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Re: Best time to mark: using AP or by hand?

If a dedicated helmsman (no other tasks) can't beat a a B&G H5000 (nav mode under sail not possible on the NAC units) over 20 miles then you need a better helmsman.

Over 200 miles I'd bet on the H5000 if the racing rules permitted use of stored energy.
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Old 25-11-2020, 20:46   #3
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Re: Best time to mark: using AP or by hand?

If your boat is sensitive to waves and heel then likely a human will do better than an autopilot, but only for the first 90 minutes or so.

In my big boat racing career (‘big’ meaning not trailerable) with 8 or more crew and dedicated navigator and/or tactician roles, during short races one or two helms people would take the entire race or swap upwind/downwind legs. Offshore, we would swap drivers every 30-60 minutes. You could definitely tell the difference between tired and fresh drivers.

But that’s racing where we cared about 0.01 boat speed changes and maximum surfing speeds, whereas your race may not be quite so competitive.
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Old 25-11-2020, 21:19   #4
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Re: Best time to mark: using AP or by hand?

Prefer to set the waypoint then set the AP to heading with a guesstimate for leeway then correct heading by degrees as true leeway becomes apparent. Set to a waypoint seems to make the AP oversteer a lot more than just maintaining a heading.
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Old 25-11-2020, 21:19   #5
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Re: Best time to mark: using AP or by hand?

Thanks. Fairly competitive. Next race is 80 mi. 8 J boats of various sizes are probably the most competitive boat, with a Bene first as well. So for 20, steer by hand, for 80, go with the ap ? 3 25 mi legs.
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Old 25-11-2020, 21:35   #6
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Re: Best time to mark: using AP or by hand?

First, a racer would probably NOT steer for the mark. The wind direction and strength will change both with time and position on the course. It is almost certain you will want to be above or below the straight line.


Second, clear air matters. You certainly don't want to get in a single file or crowded situation. You have to react to others, but slightly to weather is safer.


Finally, if I were running autopilot, it would be on WIND not COURSE. Particularly to windward, it will be faster. Then make minor AP and trim adjustments to stay where you want on the course. COURSE is for motoring or cruising.
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Old 25-11-2020, 23:04   #7
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Re: Best time to mark: using AP or by hand?

Quote:
Originally Posted by jbinbi View Post
Would you:
a. Put the mark in as a waypoint, then use the AP ...
This is for friendly weekend racing, to buoy and back.
.

"AP" and "racing" should not appear in the same post


RROS. Rule 52: A boat’s standing rigging, running rigging, spars and movable hull appendages shall be adjusted and operated only by the power provided by the crew.



The rudder is a "movable hull appendage"
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Old 26-11-2020, 06:47   #8
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Re: Best time to mark: using AP or by hand?

Quote:
Originally Posted by thinwater View Post
First, a racer would probably NOT steer for the mark. The wind direction and strength will change both with time and position on the course. It is almost certain you will want to be above or below the straight line.


Second, clear air matters. You certainly don't want to get in a single file or crowded situation. You have to react to others, but slightly to weather is safer.


Finally, if I were running autopilot, it would be on WIND not COURSE. Particularly to windward, it will be faster. Then make minor AP and trim adjustments to stay where you want on the course. COURSE is for motoring or cruising.


Ap would be on nav/sail. Nav gets you to a specific point taking into account current etc, sail mode takes wind info in.
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Old 26-11-2020, 08:30   #9
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Re: Best time to mark: using AP or by hand?

Quote:
Originally Posted by StuM View Post
"AP" and "racing" should not appear in the same post


RROS. Rule 52: A boat’s standing rigging, running rigging, spars and movable hull appendages shall be adjusted and operated only by the power provided by the crew.



The rudder is a "movable hull appendage"

This rule is often modified by the sailing instructions for short handed or long distance races. The OP should check the SIs if they have not already.

For 25 mile legs the current and wind changes will be important. A ruler straight line can be very slow compared to following the shifts appropriately.
Or it can be the fastest course. Berry condition dependent.
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Old 26-11-2020, 09:57   #10
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Re: Best time to mark: using AP or by hand?

I would ask the OP to consider some additional factors that must be considered to arrive with best time to the mark. The answers are not so simple as he poses.

You specified that this is a race, not a cruise. I don't know why you would ask this question unless you are singlehanding, and even then the answer is that a competent helmsman should stay on the helm at all times unless you need to leave to trim or set sails.

Unless you are singlehanding, its always best to have a good helmsman full time, when racing. The feel of the boat is very important, not just the instruments. A change in wind, waves, current, etc. will be felt much sooner by a good helmsman, than they will show up on instruments and to be interpreted, and action decided on. A good helmsman responds instantly to these changes.

Fine course changes are continually needed when racing. You always want to steer a little high of the mark at the beginning, to allow for a possible wind shift.

You also want clear air, so the helmsman must make changes to course if you get in the lee of another boat.

After sure you can make the mark on the same tack, lay off to the mark but keep the helmsman on duty if possible. You never know what traffic you may have to quickly avoid, including other boats who have already rounded the mark and are returning on reciprocal course.


In short, an autopilot is a very poor substitute for a helmsman in a buoys race.
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Old 26-11-2020, 12:29   #11
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Re: Best time to mark: using AP or by hand?

It sounds like this race might be a great way for you to learn what works best for you and your crew. I'm quoting Waterman because he's mentioned the main points I can think of for racing.

For distance racing, you'll want enough crew so that you can drive and trim the boat constantly if necessary, while additional crew rests/sleeps until it is their turn. That's the way to make sure the boat is always at full speed.

Navigation, tactics, wind, current, waves will define where your crew points the boat and when. Staying close to the rhumb line makes sense unless you have good reason to think you can get to the mark faster by sailing a longer route.

If your AP is permitted (In my area, they're only race legal for single and doublehanded boats), and you don't have enough crew to drive 100% of the time, you want to be setting it to maintain a wind angle that points you where you want to go, and make sure the boat is trimmed for full speed on that given angle. The work is then having competent crew who can trim and navigate and be aware enough to notice a wind shift and change the AP wind angle accordingly.
Also, if you were to set your AP on nav mode and expect your crew to constantly trim to its course changes, this is hard to do unless your AP can mimic a driver who calls out when they are going lower or higher and need a retrim on the sails.

Other than speed, a major downside of an AP is that when a new driver steps in, the AP can't update them on the wind trends and driving techniques that have been proven most effective over the past hour. Having a human driver means that someone is always in tune with the boat and the wind and can pass that experience on when the new driver comes on watch.

All of that said, if you want to reduce the workload on the crew, are planning on a fun fast cruise, or want to reduce the number of crew for Covid safety considerations, AP will always be there ready to help for hours without complaining.

Have a blast!

Quote:
Originally Posted by waterman46 View Post
I would ask the OP to consider some additional factors that must be considered to arrive with best time to the mark. The answers are not so simple as he poses.

You specified that this is a race, not a cruise. I don't know why you would ask this question unless you are singlehanding, and even then the answer is that a competent helmsman should stay on the helm at all times unless you need to leave to trim or set sails.

Unless you are singlehanding, its always best to have a good helmsman full time, when racing. The feel of the boat is very important, not just the instruments. A change in wind, waves, current, etc. will be felt much sooner by a good helmsman, than they will show up on instruments and to be interpreted, and action decided on. A good helmsman responds instantly to these changes.

Fine course changes are continually needed when racing. You always want to steer a little high of the mark at the beginning, to allow for a possible wind shift.

You also want clear air, so the helmsman must make changes to course if you get in the lee of another boat.

After sure you can make the mark on the same tack, lay off to the mark but keep the helmsman on duty if possible. You never know what traffic you may have to quickly avoid, including other boats who have already rounded the mark and are returning on reciprocal course.


In short, an autopilot is a very poor substitute for a helmsman in a buoys race.
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Old 26-11-2020, 12:34   #12
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Re: Best time to mark: using AP or by hand?

racing downwind.. steer down in the puffs up in lulls. opposite upwind. surfing waves, playing the sails...heavy air, keep the boat under the rig... light air?? a good navigator can find wind from clouds... an AP is not going to be doing any of that.
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Old 26-11-2020, 13:09   #13
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Re: Best time to mark: using AP or by hand?

Option C should be significantly faster, as long as you have good helmsmen (helms-persons ?) and you have enough good helmsmen to rotate every 60-90 minutes (the more challenging the conditions, the shorter the period), so whoever is steering does so at the best of their ability. Typically, even the best helmsman starts to show signs of fatigue after an hour, 90 minutes top, of intense steering.
Having a crew that keeps the sails perfectly trimmed at all times and works in harmony with the helmsman also makes a huge difference, of course.
For longer distances, the AP catches up because hand steering cannot sustain the same intensity forever.
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Old 26-11-2020, 14:03   #14
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Re: Best time to mark: using AP or by hand?

I've never heard of an autopilot being legal to use in a race. Albeit our longest offshore race is 150 nm. But that one clearly doesn't allow use of an AP, as per Rule 52. Neither is motoring allowed.

That said, some AP's are very much better than a human in steering a course or wind angle. The one situation otherwise, is steering with quartering seas and wind, when surfing is better done by feel. IMO.
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Old 26-11-2020, 17:21   #15
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Re: Best time to mark: using AP or by hand?

Raced lasers 45 years ago. Good enough to place in top 20% consistently as a teen in the Eastern seaboard division. So I know about racing.

Going to be double handling 45' cat on a 3 leg 80 mi race. Probably 10 to 14 hours, so having AP Do a good job certainly helps.
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