FW: Volvo 70 stability and safety at sea (Mike K et al) (was Lapworth predicted ,etc.)

Hi, Mike - As promised, here are Stan's comments. For those who don't know, Stan has done many Transpacs and has been navigator or skipper on many of the newer canting keel boats including Roy Disney's (now Orange Coast College Sailing Center's) Pyewacket and Volvo 70 ABN AMRO One. \Rog Cal 29+ #1 Swiss Navy Cal 2-30 #77 St. Lori's Comet _____ From: Stan Honey Sent: Tuesday, November 28, 2006 11:27 PM To: ro… [at] nvsailing.org Subject: RE: Volvo 70 stability and safety at sea Rog, I'm sure that canting keels will soon be reliable, just as carbon rudder-shafts and masts became reliable when the designers got enough real-world experience with them. The more interesting question is whether the owners of sailboats want highly complex, high-performance monohulls or whether they are happy with simpler boats. The TP52 proves that you don't need a canting keel to have a fast, stiff, fun, safe monohull. In terms of stability regarding "safety at sea", there are some advantages to canting keels. When a canting keel boat has its keel canted, it typically has 0 degrees of inverted stability. I suspect that fatigue was the culprit in many recent failures of canting keels. In conventional monohulls, the routine working load is such a small percentage of the worst case load that fatigue doesn't really play a factor. In canting keel boats, the routine load is a reasonably high percentage of the worst case load, and so my impression is that the designers overlooked the fatigue in the structures that were routinely cycled at a reasonable percentage of their breaking strength. As you know, a corrosive environment like salt water makes fatigue even worse. Cheers, Stan _____ From: Rog Jones [mailto:ro… [at] nvsailing.org] Sent: Friday, November 24, 2006 19:36 To: 'Stan Honey' Subject: Volvo 70 stability and safety at sea Hiya, Stan - Would you give me a few comments on this subject, particularly as to the safety and functionality of the canting keel on these boats? Hope all is well. I look forward to hearing from you. When are you going to come up to Reno and talk to our fund raiser? All the best. \Rog

Rog Jones wrote: > > > > > Rog, > > > > > > > I suspect that fatigue was the culprit in many recent failures of > canting keels. In conventional monohulls, the routine working load is > such a small percentage of the worst case load that fatigue doesn't > really play a factor. In canting keel boats, the routine load is a > reasonably high percentage of the worst case load, and so my > impression is that the designers overlooked the fatigue in the > structures that were routinely cycled at a reasonable percentage of > their breaking strength. As you know, a corrosive environment like > salt water makes fatigue even worse. > OK, Rog, here's another question. Are the keel fins on those canting-keel boats made of steel or of carbon fiber? Does carbon fiber fatigue in the same general way that metal structures do? And do they corrode in a salt-water environment? If the keel fins are metal structures, I assume that corrosion accelerates fatigue, but is it an additive effect (working life shortened by ____ hours) or a multiplying effect (life shortened by X percent)? Are these boats in the water long enough for corrosion-accelerated fatigue to be significant? Just curious. Chris Campbell > > >

--- In Ca… [at] yahoogroups.com, Chris Campbell <clcampbell@...> wrote: > > Rog Jones wrote: > > > > > > I suspect that fatigue was the culprit in many recent failures of > > canting keels. In conventional monohulls, the routine working load is > > such a small percentage of the worst case load that fatigue doesn't > > really play a factor. In canting keel boats, the routine load is a > > reasonably high percentage of the worst case load, and so my > > impression is that the designers overlooked the fatigue in the > > structures that were routinely cycled at a reasonable percentage of > > their breaking strength. As you know, a corrosive environment like > > salt water makes fatigue even worse. > > > OK, Rog, here's another question. > > Are the keel fins on those canting-keel boats made of steel or of carbon > fiber? Does carbon fiber fatigue in the same general way that metal > structures do? And do they corrode in a salt-water environment? Here is an interesting report from Robin Knox-Johnson, who's been sailing around the world for a long time. http://www.sail-world.com/nz/index.cfm?nid=29187 He has a "fire hose" sized leak and attributes it to the measurer pushing his canting keel too far over during measurement. Those boats are pretty delicate to be doing what they are doing. Stan sure knows more about this than I do but I wouldn't take a boat that can be damaged by pushing on the keel into the Roaring 40s. Mike Kennedy Conquest Cal 40 # 96