The 'Virtual' Crewman - Plotting the Mary Rose's Voyage North in DR Mode

(8:30 a.m., April 27, 2011)

Well, I couldn’t go along on this trip – I wasn’t asked – so I decided to go anyway, but as a ‘virtual’ crewman. I am plotting the Mary Rose’s journey north using Dead Reckoning with my ‘Cap’n’ software program and wind and seas information for the Caribbean and North Atlantic provided by passageweather.com. This information, plus my personal knowledge of Mary Roses’s speed under known wind and sea conditions (I did sail around 1500 miles on her last November) gives me what I think is a pretty accurate DR position and progress estimate for her.

Her current position (and I would put her ‘in the vicinity of’) is estimated to be 26° 20.5N, 066°.55.9W, at 8:30 a.m. EDT on Wednesday, April 27, 2011. This puts her at the same latitude, for the moment, as Boynton Beach, Florida.

She departed Soper’s Hole in light airs on Sunday morning (Easter) and probably motored for a while until the wind picked up. Mid-day I heard from Linda Knowles (yacht anchored in Soper’s) that a breeze had come up and it was the first decent breeze they’d had in a couple of days – it had been hot and fairly calm.

Winds are currently 20 – 22 kts out of the SE, wave heights approximately 8 – 9ft. Mary Rose is most likely on a broad reach, running at more than 7 knots (I suspect 7.5) and making good time with a quartering sea. Seas are out of the SE.

I’ve plotted Mary Rose at various speeds since she left, assuming that at first, in rather light airs, she would be motoring or motorsailing the first 24 hrs., then would put up more sail as wind speeds increased, and her speed over the ground would also increase.

At 7.3 knots, she would cover 43nm per 6-hour watch, which was similar to the performance I saw on the passage down. Her hull speed is around 7 kts but under press of sail in winds exceeding 20 knots, she will do better – in 25-30 knots of wind she will do 9 knots or so and cover nearly 50nm per 6-hour watch, but that is unusual and she doesn’t have that kind of wind out there right now.

Long-term forecasts are for winds along her path to lighten up considerably in the next couple of days as she makes more northing, so they may end up motorsailing once again. Right now they have been given a 2-day ‘push’ by a disorganized low that is dissipating. According to the models, they can actually expect diminishing winds somewhat a couple of days from now. There are no storms or severe weather in the forecast for the MR track at this time.

I estimate their course at 346 degrees True, assuming that they have no intention of stopping off in Bermuda (and I doubt that they will), so my rough estimate right now is that they are at 8:30 a.m. EDT, Wednesday, about 490 nm NW of the Windward Passage entrance near Soper’s Hole on Tortola, and making good time with steady good winds and tolerable seas.

This gives them another 935nm to go to reach the entrance to Newport. At 7 knots, average, that’s 5.5 days, or roughly, getting in around midnight next Monday, May 2, or even slowing down to come in Tuesday morning after first light with a mid-morning or mid-day arrival Tuesday May 3^rd. This would coincide with Tom’s need to be off to NY on Wednesday, the next day, to run his tug boats on Thursday May 5.

Capt. Mike Martel