At 07:07 PM 5/18/98 -0700, you wrote: >Larry Edwards wrote: > >> ...SNIP... >> Sure, it's fun to have a kayak that will let you cover lots of >> miles in a day, but for most folks I recommend kayaks that have a >> wider margin of safety than those like the Nordkapp. (Of >> course this also depends on the size, torso length and shoulder >> mass of the person -- skinny kayaks can be quite stable for smaller >> people.) > >If a boat has too much stability is is difficult to heel and feels >awkward in steep waves. If a boat has too little stability it is >difficult to keep upright in breaking waves or chaotic seas. The >optimal degree of stability lies somewhere in between. The case for >moderation in stability is put forward quite eloquently in the most >recent issue of Kanawa (in an article written by John Winters). > >Dan Hagen There's a fundamental distinction between "primary" and "secondary" stability. . . (also known as "initial and secondary stability"). I'm a big fan of the secondary stability boats. . . the ones that are tippy ("tender") like you don't know but which don't get rocked in the waves. I've a Current Designs Solstice GTS which is very tender on the flat water, but just PERSISTS in staying upright and level in heavy seas. On flat water the boat is tippy and tender. On heavy seas the boat stays upright because it's designed to sit on edge and level in water that's rolling in a 45 degree angle wave. Necky has an article in its sales brochure that explains all this. In sum: Initial stability keeps the boat parallel with the water. . . Secondary stability keeps the boat from tipping over (capsize) in heavy seas . . . The boat becomes more stable as it is leaned on it's side. These stability characteristics are essential to understanding boat design. And the reason the "tippy" boat may be the best choice for the nasty waters. Somebody help me out here. . . John Winters understands this stuff! Geo. *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
George wrote; (SNIP on stability) > > Necky has an article in its sales brochure that explains all this. >In sum: Initial stability keeps the boat parallel with the water. . . >Secondary stability keeps the boat from tipping over (capsize) in heavy seas >. . . The boat becomes more stable as it is leaned on it's side. > > These stability characteristics are essential to understanding boat >design. And the reason the "tippy" boat may be the best choice for the nasty >waters. > > Somebody help me out here. . . John Winters understands this stuff! I think you guys are just trying to change the subject because you are sick of me harping on the risk thing. :-) Fair enough, I get the message. Stability is an extraordinarily complicated topic. There are books written about it. It is, as Dan mentioned, possible to have a boat that is too stable and one that is too tender. I like Nick's comment (I think it was Nick) that every use has an ideal stability profile. Problems usually arise when we make absolute statements like wide boats are better than narrow boats or whatever. There are plenty of examples of people making hairy passages in Nordkapps to support the positive comments about them as good sea boats. There are also plenty of horror stories too. Keep in mind that, by naval architecture standards, sea kayaks are not seaworthy craft in that they are not self righting. This means that the sea worthiness of the boat is inextricably linked to the sea worthiness of the paddler. Skilled paddlers have navigated open ocean in open canoes while less skilled paddlers have drowned in kayaks bedecked with safety gear on inland waters. One should not draw any conclusions from this other than the band width involved. The ideal kayak (from a stability standpoint) is the one with the greatest area under the righting moment curve, the greatest range of stability, yet still having a low metacentric height. Sounds impressive don't it. The fact of the matter is that many kayaks are pretty good in this respect but no matter how good they still need a paddler that matches the boat (or vice versa). The casual paddler who only paddles in protected waters is happier and probably better off in a wide flattish boat. The experienced paddler who takes on gnarly conditions will probably be happier in a much more tippy boat. The long distance open water traveller will be best off in a boat with lots of secondary stability, a slow roll, and plenty of displacement (see ideal boat above). And so on. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
At 7:52 AM -0400 5/19/98, John Winters wrote: > >I like Nick's comment (I think it was Nick) that every use has an ideal >stability profile. <Snip> I don't remember saying this, but it is a good comment so I will take credit. I would have said it had I thought of it, and maybe I did. Good performance is whatever you define it to be. A swim-platform is a high performance boat if what you want to do is dive off it. It is not much good if you want to practice your roll. Nick Schade Guillemot Kayaks c/o Newfound Woodworks, RFD 2 Box 850, Bristol, NH 03222 (603) 744-6872 Schade_at_guillemot-kayaks.com http://www.guillemot-kayaks.com/ >>>>"It's not just Art, It's a Craft!"<<<< *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Nick Schade wrote: >Every use has an ideal stability profile > Good performance is whatever you define it to be. A swim-platform is a high > performance boat if what you want to do is dive off it. It is not much good if you want to > practice your roll. Good thought. Seems like the same principle works in the discussion on safety. Every use -- every desire -- every recreationist has its/his/her own safety/risk profile. It is easy to talk absolutes in safety: Wear a life jacket; Learn to roll; Buy a sponson -- or don't; Practice in certain conditions; Take courses in this or that from certified instructors; Buy this boat or that boat; Don't go out in this condition or that. But it's all pretty arrogant unless one knows the individual person. Not just the individual's skills and activity, but also the direction they choose to take risk in. Some may enjoy risking hypothermia and experience the freedom of not bundling up (not me!). If that is their sport -- their enjoyment -- their profile will differ from mine. Some may enjoy the risk of night paddling. If their whole reason for kayaking is to experience the sights and sounds of night, it does little good to say that night paddling is not safe. And learning styles will affect a safety/risk profile. Some people learn best in courses. Others learn best by slow assimilation with with a bit more risk (in some direction) each time they do something. Some learn best by listening. Some learn best by writing. Some learn best by trying and failing. Some learn best while sitting -- others while standing. In either choosing a boat or advocating a safety principle, absolutes don't make much sense. Just a long way to say: "Well said, Nick. I agree." *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
>The casual paddler who only paddles in protected waters is happier and >probably better off in a wide flattish boat. The experienced paddler who >takes on gnarly conditions will probably be happier in a much more tippy >boat. The long distance open water traveller will be best off in a boat >with lots of secondary stability, a slow roll, and plenty of displacement >(see ideal boat above). And so on. > > Cheers, >John Winters Yes, but this begs the question. Is an experienced, competent, but perhaps tired, paddler less likely to be knocked over in rough conditions in a relatively stable narrow boat like a Solstice GTS or Mariner II than in a relatively tender narrow boat like a Looksha II or Nordkapp? Maybe not at the ultimate expert level of skill but I think yes at the moderately expert level of skill. Jerry *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
George wrote > There's a fundamental distinction between "primary" and "secondary" >stability. . . (also known as "initial and secondary stability"). I'm a big >fan of the secondary stability boats. . . the ones that are tippy ("tender") >like you don't know but which don't get rocked in the waves. I've a Current >Designs Solstice GTS which is very tender on the flat water, but just >PERSISTS in staying upright and level in heavy seas. On flat water the boat >is tippy and tender. On heavy seas the boat stays upright because it's >designed to sit on edge and level in water that's rolling in a 45 degree >angle wave. > I also have a Solstice GTS. IMHO it is extremely stable on flat water for a 22" beam boat. Not tender at all. For tender compare it to an Arluk 1.8 or Nordkapp or Looksha II. However, I agree that it is also extremely forgiving in heavy seas. Jerry *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
.Jerry wrote; (SNIP) > > >Yes, but this begs the question. Is an experienced, competent, but perhaps >tired, paddler less likely to be knocked over in rough conditions in a >relatively stable narrow boat like a Solstice GTS or Mariner II than in a >relatively tender narrow boat like a Looksha II or Nordkapp? Maybe not at >the ultimate expert level of skill but I think yes at the moderately expert >level of skill. Whether he will be capsized or not depends upon the shape of the stability curve, the paddler's experience with the boat, and his overall ability. That is why the nature of the boat relative to the paddler and the paddler's objectives is so important. It is always possible to postulate some condition where one or the other is inadequate to the objective and that is the direct result of using boats that are not self righting and rely upon the occupant for power, control, and stability. For instance, a boat with high form stability is always at greater risk of capsizing in breaking beam seas until the paddlers are tired and then it probably doesn't make much difference what boat you have. A tired paddler might well be better off in a more stable boat but when he isn't tired he may be better off in a less stable boat. A boat with higher form stability may actually cause an increased chance of sea sickness due to its quicker motion so even though the boat might seem safer it may contribute to creating an unsafe situation. Postulating that one or another boat is best for any given set of environmental circumstances is always full of risk because the boat and paddler are a system not separate and discreet entities. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
John wrote > >Whether he will be capsized or not depends upon the shape of the stability >curve, (snip.) I have tried to understand the "stability curve" charts in Sea Kayaker that they print in the reviews. But maybe John or someone could explain them in simple terms. Jim Champoux & Son -------------- jim_at_sigall.com *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Jim wrote; >I have tried to understand the "stability curve" charts in Sea Kayaker that >they print in the reviews. But maybe John or someone could explain them in >simple terms. I wrote an article on this topic for Sea Kayaker that they published some time back. Cannot recall exactly when but the file says I wrote it in June 1996. If anyone wants I will try to dig up all the graphs and put it up on a web page. With the graphs it would be a large file and not really suitable for sending as an attachment. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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