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Old 26-01-2010, 18:39   #391
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Thats amazing!
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Old 26-01-2010, 20:00   #392
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Originally Posted by Hud3 View Post
At least one poster suggested the knockdowns could have been caused by breaking following waves forcing the boat into a broach, which resulted in the knockdowns.
Today, when looking for drogue solutions for our use I came across the following:

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A second optical illusion is that a dangerous breaking wave comes from a direction different from the prevailing wind and sea. The report of the Investigating Comm. for the Hobart Sydney disaster states "Exceptional waves were responsible for inflicting the damage or causing severe knockdown to yachts. These waves were 20 to 100% larger than the prevailing seas and came from a direction other than the prevailing wave pattern".

From physical considerations it is virtually impossible for a breaking storm wave to approach from a significantly different direction. Breaking waves are formed by the wind and by the addition of the energy of the smaller waves that they overtake. If a wave moved across a series of smaller waves it would lose all its energy in turbulence. We have many aerial views of the sea surface in the Sydney Hobart storm. If a large wave had moved across the smaller waves we would see a white streak running across all the other streaks. There is no such a streak. What actually happens is that if the boat is lying at some angle to the prevailing sea as the breaking wave approaches, the action of this wave yaws the boat until it is abeam. This yawing motion is not observed by the skipper and he thinks the wave direction has changed, whereas it is the boat that has moved. It is true, however, that the waves that caused the damage were "exceptional"
That is from the inventor of the JSD, Don Jordan. The quote was taken from Jordan Series Drogue - Storm Waves .



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Old 26-01-2010, 21:04   #393
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Yes, the Storm Tactics Handbooks (Google Books) definitely suggest a rogue breaking following wave can cause the boat to broach suddenly, so that the wave breaks beam on.

Also the BBC program I linked to earlier shows that there is a class of rogue wave that travels parallel with the rest but sucks up energy from the wave in front and behind, creating a huge steep wave with deep leading and trailing troughs. Proven mathematically by Scrodinger's Wave Equation no less. Most probably the sort encountered by Jessica et al.

The program also describes waves around regions of strong currents, east coast of South Africa for example, where rogue waves from different directions pop up, and cause amazing damage. Ships know to avoid these areas.
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Old 26-01-2010, 21:36   #394
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Jessica has averaged 4.6 knots since leaving Sydney. How does that stack up for the hull, anyone have any thoughts?
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Old 26-01-2010, 21:39   #395
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Sounds about average for a cruiser.
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Old 26-01-2010, 21:41   #396
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I think she has been moving right along. She is a dinghy racer/instructor.

Here is a cool link I found posted by some cruisers who talked to her by radio near Norfolk Island

Meeting a Pink Lady | Around the World

Richard W
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Old 26-01-2010, 22:58   #397
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Also the BBC program I linked to earlier
Too much hype and not enough substance for my taste.



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Old 26-01-2010, 23:15   #398
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Too much hype and not enough substance for my taste.



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Yes there was a bit of hype, but it was very watchable and the science is there. Google Rogue Waves Schrodinger, for example this article is very readable

Physics - Exciting rogue waves

Intriguingly, the same physics that predicts rogue waves also can be used to get create extreme high intensity light pulses in optical fibre systems (and carry even more information).
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Old 27-01-2010, 07:46   #399
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Jessica has averaged 4.6 knots since leaving Sydney. How does that stack up for the hull, anyone have any thoughts?
Right smack in the 4ksb range
Steve.
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Old 28-01-2010, 03:32   #400
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http://www.news.com.au/couriermail/e...s/pdfs/181.pdf

This is a hell of a good read......
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Old 28-01-2010, 04:43   #401
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Kiwi Guy,

Thanks for the great link! I posted it in chronological order at
Whitehall Bay along with other obscure links.
Very cool family. No Telly.

Richard in MD
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Old 28-01-2010, 16:40   #402
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Quote:
Originally Posted by SvenG View Post
Today, when looking for drogue solutions for our use I came across the following:

That is from the inventor of the JSD, Don Jordan. The quote was taken from Jordan Series Drogue - Storm Waves .



-Sven
With all respect....I think Mr. Jordan needs to take a good look at that fishing boat Video I posted...
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Old 28-01-2010, 17:15   #403
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Sailrite has numerous drogue kits for sale.
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Old 28-01-2010, 18:09   #404
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Hey, Stillraining where is that video?
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Old 28-01-2010, 18:21   #405
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Just a reminder, folks, about staying on topic. In this thread, that means Jessica Watson, who is now on the inbound half of her epic voyage. There are plenty of other threads here that deal with Jordan Series Drogues.

Thank you for your cooperation.

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