Brain hurts - Working out course to steer

[Dockhead]

Originally Posted by Andy Todd

To Dockhead from the OP, Thanks for clarifying the problem domain for everyone. And, more specifically for me I'm looking for a simple digital solution.



BTW I'm a pilot (air type) where we 'fly the air mass', so I fully understand the problem.


It amazes me the number of sailors I've spoken to that don't get CTS. The advent of the 'tear along the dotted line' plotters has a lot to answer for.



I note that SailGrib Free (and in common with many other products) doesn't have tidal atlases for European coasts which makes its weather routing pointless and maybe dangerous for the ab initio navigator. It works for US waters 'cause the authorities make them free issue.

Cheers.



The "simple digital solution" for UK waters (and Brittany and perhaps Iberia as well now) is this:


Passage Planning Software


It's not cheap, alas, but it does the business. You can plug wind data and boat performance into it as well and it will do basic weather routing integrated with tide planning, which is really awesome -- something impossible, I think, to do by hand.


It would be great if someone would do a plug-in for OpenCPN which does this. I actually have an electronic tidal atlas for all of Western Europe -- a gift from a ship captain friend. So I know that it is absolutely possible to develop a program with functionality of Neptune Planner Plus, which covers at least all European waters.


Note however that the NEED for this program mostly concerns CROSSING something -- like the Channel or the North Sea. Sailing ALONG coasts you don't really have this problem -- you will speed up and slow down in relation to land, but CTS is rarely any big deal. That being said, however -- we have rolling tides in some of these areas where the timing of departure can be critical -- with a reasonably fast boat, you can either ride the wave of fair tide, or fight it for hundreds of miles.

[boatman61]

Originally Posted by Dockhead

Traditional navigation skills are extremely useful, even if you don't do hourly plots and do most of your work on a plotter. At least to understand what the computer is doing for you.


But tidal vector calculations is something which no plotter and no general navigation program I have ever seen will do for you. And you are basically screwed trying to cross a rapidly moving body of water like the English Channel, or the North Sea, or the Gulf Stream, without understand how to do this. I think it's an essential skill. I don't think you can pass any of the RYA Yachtmaster exams without it.

It used to be essential for Coastal Skipper and the old much higher qualified International Helmsman Certificate back in the 70's/80's.. as opposed to the vastly dumbed down ICC of today.. but hey.. it boosts RYA revenue for what is basically the old Competent Crew of yesteryear.

[Dockhead]

Originally Posted by valhalla360

If you current is running for or against you, SOG is what will tell you when you will arrive...plus I have a pretty good feel for STW for normal cruising RPM.

It gets you the correct CTS in real time.

Sure, but only valid if the current doesn't change.



The tide changes, and there is the rub.

[boatman61]

Originally Posted by Dockhead

Sure, but only valid if the current doesn't change.



The tide changes, and there is the rub.

An example of what has to be dealt with after the relatively easy crossing of the English Channel and want to visit Gurnsey and Jersey..
Bear in mind in places like the Alderney Race for example the tides can run upto 7kts in Springs so planning and reading the data is crucial if you dont want to join the thousands who've wrecked on the Minkies and many other reefs and ledges scattering this area..
Should give your programs some fun..

[goeasy123]

Dockhead (and all), What do you think of the attached, courtesy of the nice people at the Penzance Sailing Club website.


If you expand the hidden columns and rows you can see the calcs.


It's set up for only 6 tides. It wouldn't take much to adapt it for n tides.

[boatman61]

Originally Posted by Andy Todd

Dockhead (and all), What do you think of the attached, courtesy of the nice people at the Penzance Sailing Club website.


If you expand the hidden columns and rows you can see the calcs.


It's set up for only 6 tides. It wouldn't take much to adapt it for n tides.

No program/link/whatever.. Mind theres strong tides down Falmouth/Penzance...

[goeasy123]

Umm... seems like I can only attached videos. Try this link on your browser...



https://pzsc.org.uk/wp-content/uploa...calculator.xls

[Dockhead]

Originally Posted by boatman61

An example of what has to be dealt with after the relatively easy crossing of the English Channel and want to visit Gurnsey and Jersey..
Bear in mind in places like the Alderney Race for example the tides can run upto 7kts in Springs so planning and reading the data is crucial if you dont want to join the thousands who've wrecked on the Minkies and many other reefs and ledges scattering this area..
Should give your programs some fun..

Indeed -- the rotary tides in the Bay of St. Malo are crazy. But the planning is somewhat easier since the distances are shorter so you don't normally have to deal with more than one tide.





You have greatly understated the power of the Alderney Race -- up to 14 KNOTS at springs (!!!). I've never transitted the Race at max flow springs, but I have seen 18 knots SOG there before


Catch the ebb in the Alderney Race running against a SW gale, and you're dead.

[boatman61]

Originally Posted by Dockhead

Indeed -- the rotary tides in the Bay of St. Malo are crazy. But the planning is somewhat easier since the distances are shorter so you don't normally have to deal with more than one tide.





You have greatly understated the power of the Alderney Race -- up to 14 KNOTS at springs (!!!). I've never transitted the Race at max flow springs, but I have seen 18 knots SOG there before


Catch the ebb in the Alderney Race running against a SW gale, and you're dead.

Was not sure I'd be believed so kept it conservative..
Have seen 16kts SOG heading N from St Peters Port though on a Magyar 7..

[Pete17C]

I completely understand how to adjust a heading enroute to compensate for my planning not being 100%. I don't plan for leeway so I expect to have to make adjustments

also a pilot, so nav planning in a current was tested by the FAA, but winds aloft are usually pretty constant (direction and speed) for the 5-6 hrs I could fly on full tanks

the constant heading thru changing tides I was taught in US Sailing basic cruising

the idea of the boat making it's own wind as it moves in a current I never heard of (kinda why I lurk here, much knowledge can be gained) and after thinking about it, it makes complete sense

cheers 🍻

[Pete17C]

Hells gate between the Hudson and the LI Sound is hectic, but I had a day sailor out of the nonesuch river in Maine, absolutely could not get out to the ocean with the incoming current, then decided if I did manage it, I wouldn't be able to get back in

/9ft tide thru about an 800ft wide channel
//had a lovely day in the bay

[oldersalt1944]

My Navionics does it automatically, over short distances at least. I point the boat toward the destination and the Navionics s/w keeps the boat on the correct course. I first discovered this when I noticed that the chart showed the boat crabbing. Course and heading were not the same. The boat symbol on the chart was definitely pointing up-current while the course was taking us toward the target. I rejoiced! No more screwing around with vector diagrams! (as long as the electronics keep working, of course).
Oldersalt

[Stu Jackson]

Originally Posted by oldersalt1944

My Navionics does it automatically, over short distances at least. I point the boat toward the destination and the Navionics s/w keeps the boat on the correct course. I first discovered this when I noticed that the chart showed the boat crabbing. Course and heading were not the same. The boat symbol on the chart was definitely pointing up-current while the course was taking us toward the target. I rejoiced! No more screwing around with vector diagrams! (as long as the electronics keep working, of course).
Oldersalt

Perhaps.


But were you shown CTE or just heading (boat) or bearing (course to WP).

[belizesailor]

Originally Posted by Andy Todd

To Dockhead from the OP, Thanks for clarifying the problem domain for everyone. And, more specifically for me I'm looking for a simple digital solution.



BTW I'm a pilot (air type) where we 'fly the air mass', so I fully understand the problem.


It amazes me the number of sailors I've spoken to that don't get CTS. The advent of the 'tear along the dotted line' plotters has a lot to answer for.



I note that SailGrib Free (and in common with many other products) doesn't have tidal atlases for European coasts which makes its weather routing pointless and maybe dangerous for the ab initio navigator. It works for US waters 'cause the authorities make them free issue.

You should be able to download Copernicus current GRIBs which have global coverage.

[Gruz]

You can try this one....

https://www.youtube.com/watch?v=Ur78ftR3_fA