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06-02-2019, 07:13
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#61
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Moderator
Join Date: Mar 2009
Location: Denmark (Winter), Cruising North Sea and Baltic (Summer)
Boat: Cutter-Rigged Moody 54
Posts: 35,024
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Re: Brain hurts - Working out course to steer
Quote:
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.
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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.
__________________
"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
Walt Whitman
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06-02-2019, 07:23
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#62
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Senior Cruiser
Join Date: Jan 2010
Location: PORTUGAL
Posts: 31,081
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Re: Brain hurts - Working out course to steer
Quote:
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.
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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.
__________________
You can't oppress a people for over 75 years and have them say.. "I Love You.. ".
"It is better to die standing proud, than to live a lifetime on ones knees.."
Self Defence is no excuse for Genocide...
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06-02-2019, 07:41
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#63
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Moderator
Join Date: Mar 2009
Location: Denmark (Winter), Cruising North Sea and Baltic (Summer)
Boat: Cutter-Rigged Moody 54
Posts: 35,024
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Re: Brain hurts - Working out course to steer
Quote:
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.
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Sure, but only valid if the current doesn't change.
The tide changes, and there is the rub.
__________________
"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
Walt Whitman
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06-02-2019, 08:06
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#64
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Senior Cruiser
Join Date: Jan 2010
Location: PORTUGAL
Posts: 31,081
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Re: Brain hurts - Working out course to steer
Quote:
Originally Posted by Dockhead
Sure, but only valid if the current doesn't change.
The tide changes, and there is the rub.
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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..
__________________
You can't oppress a people for over 75 years and have them say.. "I Love You.. ".
"It is better to die standing proud, than to live a lifetime on ones knees.."
Self Defence is no excuse for Genocide...
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06-02-2019, 08:17
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#65
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Registered User
Join Date: Dec 2018
Location: Currently Northern Spain
Boat: Najad 400
Posts: 265
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Re: Brain hurts - Working out course to steer
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.
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06-02-2019, 08:20
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#66
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Senior Cruiser
Join Date: Jan 2010
Location: PORTUGAL
Posts: 31,081
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Re: Brain hurts - Working out course to steer
Quote:
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.
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No program/link/whatever.. Mind theres strong tides down Falmouth/Penzance...
__________________
You can't oppress a people for over 75 years and have them say.. "I Love You.. ".
"It is better to die standing proud, than to live a lifetime on ones knees.."
Self Defence is no excuse for Genocide...
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06-02-2019, 09:06
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#67
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Registered User
Join Date: Dec 2018
Location: Currently Northern Spain
Boat: Najad 400
Posts: 265
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Re: Brain hurts - Working out course to steer
Umm... seems like I can only attached videos. Try this link on your browser...
https://pzsc.org.uk/wp-content/uploa...calculator.xls
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06-02-2019, 09:10
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#68
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Moderator
Join Date: Mar 2009
Location: Denmark (Winter), Cruising North Sea and Baltic (Summer)
Boat: Cutter-Rigged Moody 54
Posts: 35,024
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Re: Brain hurts - Working out course to steer
Quote:
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..
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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.
__________________
"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
Walt Whitman
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06-02-2019, 11:16
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#69
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Senior Cruiser
Join Date: Jan 2010
Location: PORTUGAL
Posts: 31,081
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Re: Brain hurts - Working out course to steer
Quote:
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.
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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..
__________________
You can't oppress a people for over 75 years and have them say.. "I Love You.. ".
"It is better to die standing proud, than to live a lifetime on ones knees.."
Self Defence is no excuse for Genocide...
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07-02-2019, 16:09
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#70
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Registered User
Join Date: Aug 2018
Location: Hudson Valley, NY
Posts: 365
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Re: Brain hurts - Working out course to steer
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 🍻
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07-02-2019, 19:25
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#71
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Registered User
Join Date: Aug 2018
Location: Hudson Valley, NY
Posts: 365
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Re: Brain hurts - Working out course to steer
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
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07-02-2019, 21:35
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#72
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Registered User
Join Date: Jan 2014
Location: S.F. Bay Area
Boat: Grand Banks 32
Posts: 39
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Re: Brain hurts - Working out course to steer
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
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07-02-2019, 22:41
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#73
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Registered User
Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 9,758
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Re: Brain hurts - Working out course to steer
Quote:
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
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Perhaps.
But were you shown CTE or just heading (boat) or bearing (course to WP).
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Mill Bay, BC, SR/FK, M25, Rocna 10 (22#) (NZ model)
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08-02-2019, 04:56
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#74
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Registered User
Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 13,493
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Re: Brain hurts - Working out course to steer
Quote:
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.
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You should be able to download Copernicus current GRIBs which have global coverage.
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08-02-2019, 07:16
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#75
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cruiser
Join Date: Dec 2018
Posts: 106
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Re: Brain hurts - Working out course to steer
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