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post #8 of Old 01-17-2007
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Location: Annapolis, Md
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I am a big fan of plumb, or nearly plumb stems. I have not seen the discussion on the comfort of plumb bows but my experience with them, (as does the motion comfort testing that I have seen) suggests that they have a much more comfortable motion (particularly in a chop) since they do not collide as hard with waves and since the buoyancy transistion as the bow enters a wave is more linear and less sudden. They offer much better pitch dampening. Properly modeled plumb bows result in a more easily driven hull form for their given displacement therefore requiring less sail area for a given wind condition. They allow a slightly narrower waterline beam resulting in a slightly gentler roll motion for a given displacement. Properly modeled a plumb bow results in a longer and narrower waterplane, which improves tracking and so partially offsets the loss in tracking associated with the short chord fin keels typically being used with these hull forms. They offer more speed, and allow the center of buoyancy to be moved aft (with all of the advantages that affords) without the penalty of going bow down when heeled.

My only criticism is that I do prefer more flare to the bow than is typical with the current crop of racing plumb stems.

I got a kick out of Giuletta's (What's his name anyway?) post. Giulietta appears to be a really neat boat. I have been admiring Giulietta from what I have been able to see of her.

A quick comment on the angled daggerboard, it was a compromise that I made in the late 1990's when I first sketched this design. I went with the angled daggerboard because I had some structural design ideas that suggested that the angled board might have some positive structural implications when engineering around the loads of a hard grounding. I also thought that the angled board might allow the boat to hove to more effectively by spreading its area over a larger percentage of the boat's waterline length. Annecdotally I have come to suspect that the new vertical keels do not hove to very well as compared to similar area but raked keels.

SD, Thanks for the kind words.

I did want to comment on the design brief presented above. As I read it again this morning, not having actually read it in many years, I was a little surprised by its tone and by the things that were missing from it relatyive to my current thinking. The design brief was written nearly a decade ago, and for multiple purposes partially related to the book that they were intended for. My friend Tony Dias, who is a yacht designer, artist and author (and, like Giulietta's owner is of Portuguese decent), has an intellect and breadth of interest that dwarfs my own, making for very lively and thought provoking exchanges on a range of topics.

He and I had spent many years in a lively dialogue about the virtues of traditional water craft vs more modern designs. Tony is a yacht designer of extraordinary talent and his yacht designs are truly creatures of breathtaking beauty. Tony's natural inclinations leans towards the traditional. I grew up with traditional watercraft and I still am a very big fan of their inherent virtues, but have also spent much of my recent sailing career on more modern designs and have come to love their sailing abilities and ease of handling. To one degree or another, my design brief was intended to provide a forum for that discussion within Tony's book.


Last edited by Jeff_H; 01-17-2007 at 09:27 AM.
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