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 SailNet Community I have a new blog entry about YONI, one of my more interesting projects
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#21
12-10-2011
 Geoff54 Senior Member Join Date: Oct 2011 Posts: 711 Thanks: 4 Thanked 8 Times in 8 Posts Rep Power: 4
Nice looking Yacht and really interesting to read the story behind it.

I hope I’m not asking too much - I have a simple question which may be require too long or complicated an answer for here - I won’t be offended if you tell me to go and read up on design principles (would you mind pointing me in the right direction?). Also, I believe that “Limit of Positive Stability” is exactly the same as “Angle of Vanishing Stability” i.e. the zero axis when the Center of Gravity is directly above the Center of Buoyancy, before which (in the absence of any other forces), a boat will right and beyond which it will continue to invert. If I’m wrong, that might explain things, otherwise…

I was surprised to read that that achieving a Limit of Positive Stability of 135 degrees “can be a challenge for some cruising boats”. I always assumed that, within some reasonable limit, achieving a higher AVS was mostly a matter of lowering the C of G by using a deeper and/or heavier keel. I took a quick look at the R.Y.A. Stability List and while there are many boats with numbers under 135, there are quite a few respected cruising yachts with numbers significantly above that (examples include Nordship 40DS – 140, Island Packet 485 – 143, Swan 602 – 153, Sweden Yachts 42 – 156, Vancouver 34 – 166). There are even a few with an AVS of 180, which I didn’t realize was possible – a cork ball with a six inch nail stuck in it, maybe.

I always thought that lower AVS was a compromise because of some combination of cost, desire to keep the overall displacement down or sacrificed because of form stability (cue – wide butt discussion).

I assume I’m missing something but I’m not quite sure what.

Thanks

Geoff
#22
12-10-2011
 bobperry grumpy old man Join Date: Apr 2011 Posts: 3,929 Thanks: 1 Thanked 91 Times in 87 Posts Rep Power: 5
tdw:
Knee is much better thanks.
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