Coastal Navigation question.

[AntarcticPilot]

One of my favourite quotations (from some Ancient Greek) is "The only constant is change". Except he said it in Greek I assume.

Πάντα ρει (Heraclitus) is what you're looking for! But your translation is a little free; it means "Everything flows".

 

[Ubergeekian]

And as my 'owner' used to say. "Sail well offwind and you save minutes. Sail well upwind and you save hours."

"Wait till the wind changes and save your sanity"

 

[Twister_Ken]

Πάντα ρει (Heraclitus) is what you're looking for! But your translation is a little free; it means "Everything flows".

Not my translation - as if - but from some dictionary of quotations. I first used it in the eighties, when writing for a long-gone mainframe manufacturer.

He also said something like "No man ever steps in the same river twice."

 

[boatmike]

set-up a "Cone". 2 lines say 60deg apart radiating from the waypoint & "tack down the cone" tack each time your course intersects a line. each tack will get shorter as you travel down the cone

On the other hand just hoist the bloody cone up the forestay and start the engine. Gentlemen don't beat to windward don't you know?

 

[Ubergeekian]

On the other hand just hoist the bloody cone up the forestay and start the engine. Gentlemen don't beat to windward don't you know?

We don't have engines either. An auxiliary may be permissible in some circumstances, but anything which can make progress into a headwind is a little, well, vulgar, old boy. Not quite the done thing.

 

[bbg]

I have to say I really don't get what you're getting at. In a perfect world, the quickest way to get there would be to take one long tack in one direction, and one long tack in the other direction. Tacks are slow, so minimising them (i.e. only one tack) will get you there quickest. (As an aside, the Americas Cup boats this time round are so quick, and tacking is so slow, that there will be a huge incentive not to tack, and we could see the boats tacking only two or three times in the 20 mile beat).

However - the world isn't perfect (and very few people can judge a perfect lay line from even 2 miles away, let alone 20). As others have said, tide and windshifts will impact. Passage planning will help you use tides to your advantage.

The idea of tacking up a cone that is narrower than your tacking angle will ensure you don't overstand whatever it is you are sailing towards, and will allow you to take advantage of any windshifts that might come through even late in beat.

I can't think of a formula that will get you there quicker. But you can learn from the racers. Tack on a header in oscillating shifts; sail deep into a header and take late on a persistent shift. The skill is in knowing which is which

 

[dunedin]

Always aim to tack on the point of a headland, never in the bay (unless other tidal factors over-ride). This will give the best wind bend advantages. Regularly take miles off other boats by using this technique.

 

[mcframe]

The key as mentioned above is to use your ships head when close hauled. If you are getting lifted towards the upwind objective keep going, if getting headed tack.

A GPS plotter is of course very good at visualising the VMG calculation. At a glance you can see how effective each tack is at making ground to your objective. If you don't have a plotter you can work this up on your chart.

Tide plays a big part in VMG the classic case being on your lee bow. Sailing close hauled with a strong tide on your lee bow could help your ground track towards the objective.

Cross-track error can be handy if you're on the lay-line and already doing best course to windward (minus a small bit to avoid pinching).

A glance every couple of minutes can 'damp out' any small headers or lifts and indicate any more significant shifts - and it will allow for tide.

 

[Searush]

Ok, I'm definitely one of the "put the engine on" brigade. But why is no-one looking at their GPS/ plotter to see VMG? I know it is only showing history, but you can assess the trend & judge the coming weather/ tides etc.

I love a good sail, but with the cockpit full of family "passengers", or with just myself aboard, short tacking is not a sensible option unless the conditions are just so good I can't resist it!

 

[lw395]

Ok, I'm definitely one of the "put the engine on" brigade. But why is no-one looking at their GPS/ plotter to see VMG? I know it is only showing history, but you can assess the trend & judge the coming weather/ tides etc.

I love a good sail, but with the cockpit full of family "passengers", or with just myself aboard, short tacking is not a sensible option unless the conditions are just so good I can't resist it!

I don't often use an actual VMG read out, (do you mean VMG toward goal or VMG upwind BTW), but I often use a GPS repeater showing COG SOG BTW DTW, and compare the angles mentally. I also use bearing to waypoint as a limit, e.g. not that if BTW becomes less than 260deg, you're going to hit the headland/rocks on the way to the waypoint, unless you tack off.