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Sailing in tide..quiz.

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iGRF View Drop Down
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 1:16pm
This race officer? The one that takes all that into account, love to meet her.


Edit, so the next thing we need to use your magic tool for is that, say it's a lay line approach with the adverse tide just a degree to weather of it. Then Boat A sails a normal course, but Boat B squeezes two degrees up to nose into or slightly present the leeside of the nose into it.

What happens then?

There lyeth the crux to earlier discussion

Edited by iGRF - 03 Oct 17 at 1:21pm
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Post Options Post Options   Quote mozzy Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 1:42pm
By 'normal course' do you mean the fastest angle of sail for making good VMG? 

If pinching was faster you'd do it all the time, and it would become the normal course. So, by pinching, I take it to mean a higher and slower course which produces an overall slower VMG. 

The only time pinching for a mark is quicker than sailing your normal (fastest) course is if the gain from not having to double tack outweighs the gain of sailing you faster normal VMG angle. 

Basically, if you are on a layline with a weather tide and are struggling to make the mark, then you have understood. It is no different to underlaying a mark on a lake. So the decision making process is the same. 

How much will I loose by pinching (slower VMG mode) versus how much will I loose by double tacking. 

If you are far out from the mark, a two tacks is usually better. You will have plenty of time to complete the tacks (and could even do them on a little shift, or to get out of dirty air) and pinching from a long way out will mean sailing an inefficient mode for a long time. 

If you are very close to the mark, a double tack in such a short distance will usually be worse than just pinching "or 'shooting the mark". You'll also be on sticky ground rules wise if within 3 boat lengths. 

A classic  mistake, and it gets worse in big fleets is trying to pinch to lay a mark you have underlain from far out. You see it often in junior fleets in the very situation you describe. The sailors would do better if they accepted they had understood and sailed their normal mode and complete the extra tacks. 

Usually it is better in a fleet scenario to complete the first tack early, then you're not sat in the procession of pinching boats getting dirty air as well. 

If you are not in a fleet (or clear ahead Wink) I would do the extra tacks nearer the mark to make judging the true layline easier. 

I can draw out the vectors, but it will require knowing the speed penalty for pinching versus normal mode and the speed penalty of tacking; both will be class specific.  


Edited by mozzy - 03 Oct 17 at 1:55pm
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 1:55pm
Well what normally happens, you make the mark and the boat/board that doesn't react has to double tack and if as it so often happens, it's a starboard layline then he's screwed. Double screwed because he continues to get knocked and you get lifted but then it doesn't work so could never happen according to your logic.
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Post Options Post Options   Quote mozzy Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 2:04pm
It would be silly to double tack late if you are under pressure from starboard boats behind. Like I said in my post, if you are in a big fleet tack out early then sail your normal faster VMG angles.

But, you're point above is nothing to do with lee bow. It's just someone who's under stood a mark, was slow to react and got himself pinned out by a procession of starboard tackers on the layline.

Tell me this, if pinching is faster VMG than the normal mode, why do you ever sail the normal mode? If that high mode was best, then surely it would become your normal mode, because you'd always want the best VMG?

Makes no sense. And you see it in fleets all the time; if I just squeeze the bow up a bit further I'll make this mark. And they rack up from 100ms out. Then finally a boat doesn't make it, they've not left enough time to tack out, or even gybe out and the pile up starts. 

You're faster angle is your fastest angle. The only time I'd sail a slower mode is to avoid a late double tack. In a reasonably good tacking boat I'd never sail a pinching mode for more than 10-15 seconds. 

Same goes for gybing in to a leeward mark. Sometime I will sail low and slow for the last 10-15 seconds to avoid the dreaded double-gybe drop. Any longer than that and I'll just sail my fastest mode as I always would; because it's faster!  


Edited by mozzy - 03 Oct 17 at 2:19pm
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 2:22pm
Originally posted by mozzy

Almost, but you've called the wrong end of the line. 

Maybe you're accounting for the inevitable pile up at the committee boat; but I didn't actually say there were any other boats, just simply which end was favoured. 

Got that, and correction accepted  Smile
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Post Options Post Options   Quote mozzy Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 2:24pm
Originally posted by iGRF


one of the other reasons for choosing the port end, is the liability that going right will cause possible overstand scenarios at the windward mark.
Just seen this. So your answer to over standing the windward mark is to start further left? 

How would starting on the left possibly make calling the layline easier? 

The answer to that may be, that if you start port end you won't be first to the layline, so you can use the leading boats to judge when you should tack. Not going to win many races that way though!


Edited by mozzy - 03 Oct 17 at 2:28pm
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 2:36pm
Originally posted by mozzy



Originally posted by iGRF

one of the other reasons for choosing the port end, is the liability that going right will cause possible overstand scenarios at the windward mark.

Just seen this. So your answer to over standing the windward mark is to start further left? 
How would starting on the left possibly make calling the layline easier? 
The answer to that may be, that if you start port end you won't be first to the layline, so you can use the leading boats to judge when you should tack. Not going to win many races that way though!



As I said, it's not a complete scenario, you haven't quantified the line length, nor length of the beat, but assuming it's a big fleet with a long line and say half mile beat, then the left has more options than the right unless you somehow manage to blast clean from the pack off the line which would be very unlikely from the starboard end for all the reasons you cite.

Mainly because the left will over the course of the race become the middle.
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Post Options Post Options   Quote mozzy Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 3:00pm
Knowing no information about an upwind leg, you are able to decide that starting at the unfavourable end would give you more options? Interesting Thumbs Up

I agree, you'd have to be weary of being swept past the starboard lay. If the race officer laid the course to true wind the beat would be feel offset and you'd have to spend more time on starboard than port. But starting on the left doesn't help you judge either of those factors any better.

The fact is, when a boat starting at the starboard end and a boat starting at port cross, the starboard boat will be clear ahead. 

The most likely fate of the port end starters is that, starting down wind of the starboard end they are more likely to be rolled by the boat to windward of them (as they will have started slightly ahead). The option for the port end boats is then to sail over to left in dirty air, or tack out right. 

Boats starting at the starboard end are more likely to have a clear lane and a choice of where they position themselves on the course. Starboard end starters have more options as they are ahead.

I would only start at the pin if there was a massive gain feature out left that would outweigh the 10 degree bias and I could get there before the starboard end boats rolled over me. But I deliberately didn't mention any gain features in my example, as it over complicates things. 


 


Edited by mozzy - 03 Oct 17 at 3:01pm
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 4:55pm
OK I've now given this considerable thought,

First I'm going to concede in your circumstance (If I'm right you're quite a handy RS200 jockey with at least one championship win to your tally and you're a Hayling man, so not entirely without tidal credentials) which in that particular boat (In which I've only had very limited experience, but enough to tell me that going too high would slow the boat significantly more than any tidal gain would exacerbate, which isn't the case with an 18 kilo board, or even a 50 kilo single hander, so forget the pinching it's irrelevant to you and you'd never have experienced it.

But,

Second I'm going to call you on your assumptions regarding the tidal lift off that line and in this instance I'm going to quote back at you the conveyor belt assumption which will lift all the boats on starboard off the line, but not in the same way an actual wind shift would, i.e the relation of the boat sailing angles will not alter. They'll still point as they would in relation to the true wind angle but the inter boat relationship angle would not change as it would in a wind shift, so a faster boat off the Port end could still make enough ground to tack across slower starboard boats from the starboard end. The vector they all make good however would follow your assumptions.

Edited by iGRF - 03 Oct 17 at 4:57pm
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Post Options Post Options   Quote Cirrus Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 5:07pm
Whatever next .. a 'Brexit' debate ?   But it might be a tad easier to shift the opinions held on 'the other side' mind you ..... LOL   
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