Which Charts for Greenland, Electronic or Paper?
posted by John & Phyllis
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Question: [edited for brevity] I’m planning a cruise of the west coast of Greenland. For charts I have the choice between C-MAP electronic charts running on Furuno Navnet with Maxsea on a PC and Danish paper charts. Which would you recommend?
Answer: In a perfect world, both. Let me explain why: Although the C-MAP electronic charts are pretty much exact copies of the Danish paper charts and are the standard for commercial vessels in Greenland, the datums on both are often, in fact usually, inaccurate.
This means that you can’t rely on the position of the boat icon on a plotter to keep you off the rocks and instead must navigate traditionally by using ranges and bearings on land features.
During my trip to Greenland in 2005 as guide/navigator on the 88’ Jongert “Vivid” I had both paper charts and C-MAP on Maxsea available (it’s so nice when someone else is paying). I found that, although Maxsea has the capability to plot ranges and bearings, I was much faster and more accurate plotting on paper. Also, the larger area that I could see on the paper chart, without zooming in and out, helped me to stay oriented to my surroundings and position, which is vital in Greenland. I should say that I was relatively new to Maxsea at the time, compared to 40 years of navigating on paper, so this could be more my failure than a systemic one.
The two commercial vessels I visited that relied exclusively on Maxsea/C-MAP both had two very large screens allowing them to keep both an overview and detail view available at all times without zooming. In addition, I suspect most of their voyages are between the larger ports in Greenland where the datums are usually, although by no means always, more accurate than places off the beaten path where we like to go.
On the plus side for Maxsea/C-MAP, most of the charts have a datum correction amount that can be applied in the software. I chose not to do this since the correction is different for every chart and I was worried that I would either forget or not have time to change it each time we moved to a new chart. I was also not totally confident that all the corrections provided would be accurate.
In summary, I can only tell you that I would not rely solely on electronic charts in Greenland and if forced to choose only one system, would opt for paper. However, if you are totally comfortable with your electronic navigation system and your ability to navigate safely with it in a place where the datums can’t be trusted, you may decide that my belt and suspenders approach is overkill.
Labels: Passage Planning
Picking a Route Across the North Atlantic
posted by John & Phyllis
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Question: [edited for brevity] We're planning to sail from New York to Falmouth (UK) leaving around May 18th.
Our plan is to sail WSW out from New York till we hit the Gulf Stream and then attempt to sail the great circle to Falmouth. We're debating whether to consider a more southerly route to stay clear of weather systems? Any views?
Answer: This type of question (asking for a suggested route for a trans-Atlantic passage) has come up several times lately so I’m going to deal with it in some detail. Route planning, particularly in the North Atlantic, is a dynamic process that starts before departure and continues throughout the passage since the best route is continuously changing depending on the state of several factors.
The goal is to come up with a route that, as far as practical, keeps the sailboat: south of low pressure systems, so that the wind is fair; north of the Bermuda/Azores high, so there is wind; and clear of the ice to the east of Newfoundland. Also, if it does not require too large a course alteration and does not conflict with the first criteria, it would be good if the route took advantage of the Gulf Stream and any attendant eddies but without risking getting into a wind-against-current situation.
I’m going to explain the process by using real data from today (click on maps to enlarge) and write about how I would react to it. All of this data can be accessed at sea using weather fax and some method of receiving data files like an Iridium phone or Sailmail over SSB radio. None of this needs to be horribly expensive: Equipment costs are in the range of US$1000 to US$4000 and data costs from zero to less than five dollars a day—almost certainly less than that of the wear and tear on your boat that getting hammered several times would probably cause.
But before I start, a couple of cautions:
- Because this is a relatively short article, I will be radically oversimplifying. This article will not make you a competent voyaging sailboat router. It is only intended to illustrate the process. If you want to learn to do this properly, we recommend the Starpath Weather Trainer and Weather Predicting Simplified by Michael Carr.
- As the second chart shows, the North Atlantic, even in late spring and summer, can be a rough place. No amount of weather routing will save you from every gale and storm. If you and your boat are not prepared to withstand a multi-day gale or even a storm, you should not cross the North Atlantic by any route.
Monitor the path of lows
Using weather fax you can monitor the position of the Jet Stream (top map) and particularly the 564mb contour (in bold). As you can see by comparing the two maps, lows and particularly gales generally follow about the same path as this contour. The Jet Stream is a long way south at the moment so I would stay well south too.
As the lows rumble up on my port (hopefully) quarter I would then use GRIB wind field and pressure files (not shown) to refine my course to try, as far as possible, to stay close enough to the lows to have good fair winds but far enough away to avoid gale or storm force winds. As I got further east I would watch the position of the Bermuda/Azores high to make sure I did not get too far into it and lose the wind.
Look out for the Gulf Stream
Since we are cruising and not racing, I would deemphasize the Gulf Stream except to make sure that I did not inadvertently get into a wind-against-current situation. I can tell you from my ocean racing navigator days that given the choice of sailing toward a fair current or a fair wind, the fair wind wins every time. Of course both at once are nice.
I would be careful of the Gulf Stream. As you can see on the chart, it is not just a nice simple river of water heading the way we want to go. There are plenty of eddies and meanders that can deliver a foul current and even 30 knots of wind apposing the current will quickly generate truly dangerous breaking seas. There is also a higher chance of thunder storms and other violent weather in the Stream due to temperature differentials.
Stay out of ice
As you can see, the ice is a long way south at the moment. In fact, this is one of the worst ice seasons in years.
I would stay south of the ice line. Even if the ice was further north, I would stay well south of the Grand Banks, to avoid excessive fog. Though I am experienced in both ice and fog, life is too short to go looking for trouble just to save a few miles.
So in summary and going back to your original question, your basic strategy is a good one and yes, given all the factors above, I would stay well south of the great circle. In fact I would not even think about the great circle. Getting stuck in one gale on the nose for several days will more than wipe out any gains to be had from a shorter distance.
Labels: Passage Planning
Atlantic Crossing, Picking a Go Date
posted by John & Phyllis
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Question: [edited for brevity] I’m planning an Atlantic Crossing from Boston to Scotland. How can I recognize the best moment weather wise to leave for the safest crossing?
Answer: Since weather forecasts are only accurate for about four days, at best, there is no way to manage the weather for an entire crossing of that length by picking a given day to leave. This means that you and your boat should be capable of withstanding at least one multi-day gale and on that route there is the possibility, albeit small, of a full blown North Atlantic storm, even in summer. (For more details on the best months to leave, see this post.)
Having said that, you do want to try and pick a leaving date that will give you several days of good weather and fair winds so that the crew can settle down and get their sea legs. (See this article for more on our thinking about managing crew comfort.)
Generally the best departure days from the US east coast are immediately, and I do mean immediately, after a cold front goes through. This will normally give you clear weather and northwest winds as the following high pressure moves in. Of course this is based on averages and should not be taken as gospel.
You can also get a feel for how the systems are moving by analyzing the 500mb (jet steam) reports for several weeks before you leave, but to do this you will require an in-depth knowledge of weather theory and forecasting. A good idea anyway since you will have a much more comfortable, and probably safer, trip if someone on the boat has this level of knowledge and you install the necessary equipment to receive GRIB files and weather maps.
To gain a good grounding in weather theory, we recommend the Starpath Weather Trainer, an excellent computer based program learning package.
Labels: Passage Planning
Best Time for West to East Atlantic Crossing
posted by John & Phyllis
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Question: [edited for brevity] I will be sailing to Gibraltar from the Chesapeake via the Azores. When would be the best time to leave and when would be the earliest I could/should leave?
Answer: This is a pretty standard west to east Atlantic crossing. The best time to leave the east coast of North America is late May to mid-June. The earliest is probably mid-May, although leaving that early will increase your chances of a gale.
The latest date to go is dictated by the onset of the hurricane season. Ten years ago I would have said that mid-July or even late July was the latest time to leave, but we are definitely seeing more frequent and more intense hurricanes in June and July than we did then, so now I would say the end of June is the latest prudent date.
For more information you should consult the excellent Atlantic Crossing Guide, published by the RCC Pilotage Foundation.
Labels: Passage Planning
Norway to the Chesapeake Bay
posted by John & Phyllis
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This post has been archived to our main site. Please see Sailing routes.
Labels: Passage Planning
Timing, Caribbean to Europe
posted by John & Phyllis
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This post has been archived on our main site. Please see Sailing routes.
Labels: Passage Planning
North Atlantic Crossing, East to West
posted by John & Phyllis
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This post has been archived on our main site. Please see Sailing routes.
Labels: Passage Planning
