Ken Rasmussen kayakfit_at_fidalgo.net Several weeks ago I started a thread on the paddlefloat rescue which elicited a lot of comment. Rex Roberton took an excellent photo of the homemade float which I've posted on our website. (Thanks Rex!) You can see the photo, and also see a description, with photos, of the method I use to do a 30 second rescue. (And no, that doesn't include pumping--I carry the boatfull of water with me as a reminder to be more careful in the future!) The web address is www.kayakfit.com . Scroll down the menu until you find the link to the Paddlefloat Rescue, and click on it. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
At 06:52 PM 12/18/01 -0800, Kathea and Ken wrote: >Ken Rasmussen > > >kayakfit_at_fidalgo.net > > > > > >Several weeks ago I started a thread on the paddlefloat rescue which elicited >a lot of comment. Rex Roberton took an excellent photo of the homemade float >which I've posted on our website. (Thanks Rex!) You can see the photo, and >also see a description, with photos, of the method I use to do a 30 second >rescue. (And no, that doesn't include pumping--I carry the boatfull of water >with me as a reminder to be more careful in the future!) The web address is >www.kayakfit.com . Scroll down the menu until you find the link to the >Paddlefloat Rescue, and click on it. That's a good sequence of pictures showing a paddlefloat rescues but I have two comments. In the 3rd and 2nd from the end pictures it shows the paddler with his hand extended out onto the paddle shaft quite a bit. While that does keep the paddler in a stable position it is opening up his shoulder to a point where if a large wave hit it could potentially cause a shoulder dislocation. It probably isn't likely, but the photos show a vulnerable position that probably should not go without comment. Secondly, where is his PFD? I realize that it's a photo session in a pool but from my experience one of the difficult things people encounter when doing a paddlefloat reentry is having their pfd hook onto decklines, paddleshaft, cockpit combing, etc. While a PFD really might not be necessary for safety reasons in a pool, I think it is a very good idea to practice rescue techniques using all the equipment that you would be using when paddling. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Michael Daly wrote: > > From: "Robert Livingston & Pam Martin" <bearboat2_at_attbi.com> > > The second is that the rear bulkhead wraps around the paddler so that the > > kayak retains an air pocket on each side of his/her thighs (a continuation > > of the rear compartment) - Dare we say built-in "sponson"? > > This can provide additional bouyancy to prevent sinking, but it will not contribute > to stability. The water on the outside of the hull doesn't know what's inside the > hull. Adding a sponson to the _outside_ of a hull can make a difference. > Having water on the inside of the hull can decrease stability since this water is free to slosh around from side to side and affect the balance of the boat. Interior sponsons can markedly decrease the ability of this water to move from side to side and therefore they can aid in the boat's stability when the cockpit is flooded. Imagine a boat that just has a narrow channel down the centerline that can flood with water with the rest of the space fully occupied by the paddler and interior air-filled sponsons. In that case, the water in the cockpit is constrained to stay in that channel and will actually aid the boat's stability by acting as a weighted keel (albeit not as effective as that on a sailboat since it has a much shorter lever arm). OTOH, without the sponsons on the sides, the water is free to flow to the low side of the boat. Any initial tip to port then results in the water shifting to the port side and helping to tip the boat further in that direction - clearly reducing the boat's stability. It's impractical to make a boat with interior sponsons that are as effective at controlling water movement as in this hypothetical case, but to the extent that they keep interior water from sloshing to the sides of the boat they will certainly aid the stability relative to a boat of the same shape that lacks internal sponsons. > > I thought we've been over this before? And the conclusion every time is the same: > flooding a kayak is a bad thing. I didn't think that was the topic of conversation. Matt proposed that boats with high initial stability are most affected by flooding while those with low initial stability are least affected. I agree with Robert/Pam that there can be designs that have high initial stability but are also affected relatively little by flooding. One such design is a rather wide boat that still has a narrow cockpit with the remaining space on the sides occupied by air-filled internal sponsons. This doesn't mean they aren't affected at all and certainly doesn't disagree with the premise that flooding the cockpit 'is a bad thing.' Nor BTW, am I suggesting that such a design is superior to others - only that it does not follow the hypothesis proposed by Matt. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
From: "Peter Rathmann" <prathman_at_attbi.com> > It's impractical to make a boat with interior sponsons that are as > effective at controlling water movement as in this hypothetical case, > but to the extent that they keep interior water from sloshing to the > sides of the boat they will certainly aid the stability relative to a > boat of the same shape that lacks internal sponsons. True, but the effect may be small and only kick in a higher angles of heel. I'm not sure that the effect would be enough to brag about. Having deliberately flooded a couple of kayak in a pool, I know that the reduction of stability is tremendous and I don't think a sponson's several liters of volume (compared to the, say 150+ liter cockpit volume) is going to make a big enough difference. A snug sea sock may be the alternative. There the volume is constrained and if the sock can't slide sideways, the water is better constrained. I've never used a sea sock, so I can't say for sure. Mike *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
From: "Mike McNally" <mmcnally3_at_prodigy.net> > but now that we are adding more air and particulary adding it in a > manner in which the dist dx is set (superior to what a seasock does), we > are increasing these previously insignificant forces of stability > provided by the hull. I don't think I understand how it's superior to a sea sock. But then, I'm envisioning an "ideal" sea sock that is barely bigger than your body and held in place near the centerline of the kayak, thus leaving a large amount of air elsewhere. (I don't make any claims about how practical such a sea sock is.) Are you thinking about a sea sock that's a very large loose bag? > change in stability, in that particular design. But, with a more > significant interior sponson it would provide the flooded state > stability we are looking for. I think in the future we will see this > design incorporated in many boats. I'll agree with you, but then ask "Where are these significant sponsons going to go?" My Ellesmere hasn't enough room on the side of my hips for a 2" diameter hand pump. With my big feet and long legs, cockpit room forward is awkward to cut down. If you enlarge the kayak so you can fit such internal sponsons, I think you're losing something in the bargain. Mike (Who has sponsonman as a fellow member of my kayak club and a built-in allergy to things that smack of ideal solutions to a kayaking problem I don't have) *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
On Sun 23 Dec 2001, Michael Daly wrote: > > I don't think I understand how it's superior to a sea sock. But then, I'm > envisioning an "ideal" sea sock that is barely bigger than your body > and held in place near the centerline of the kayak, thus leaving a large > amount of air elsewhere. (I don't make any claims about how practical > such a sea sock is.) Are you thinking about a sea sock that's a very large > loose bag? Sort of. You may need to enlighten me about seasocks. I'm envisioning dozens of gallons of water in the seasock. When tipped to the right the dozens of gallons of water moves to occupy the right side and the air moves to the left. If the air is captive on the right side then it will have a stabalizing affect, F * dx. Are seasocks so tight that there would only be a few gallons? > I'll agree with you, but then ask "Where are these significant sponsons > going to go?" Probably nowhere in a skinny boat, but for 23in+ beam boats, ...think mummy bag (ie mostly from the knees on down). -- Mike McNally mmcnally3_at_prodigy.net Nonsense and beauty have close connections. -- E.M. Forster *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Michael Daly wrote: > > From: "Peter Rathmann" <prathman_at_attbi.com> > > > water movement, but that is also a question of design details. If you > > believe that a properly fitted sea sock could add to stability in a > > flooded boat, then similarly fitted internal > > sponsons/bulkheads/'whatever you want to call them' can certainly do the > > same thing. As you said before, the water can't tell the difference. > > I wouldn't say that it adds to stability. It minimizes the reduction of stability. I agree and that's why I said earlier that "there can be designs that have high initial stability but are also affected relatively little by flooding". I never said they would not be affected at all - just affected less than a similar boat without the internal flotation spaces. In the above statement I said it 'adds to stability in a flooded boat.' In that case the stability has already been greatly reduced by the flooding and adding in the flotation space can restore some of that lost stability. > > In general, what you say is true, however, I've been thinking in terms of the > sponsons that I've been seeing in real kayaks. These tend to be small. > > I think there's been a difference in perspective between me and others, including > yourself. I've been taking a sort-of pragmatic, "is it good enough?" view considering > kayaks I've seen or paddled, whereas others have been saying "does it happen at > all?" with atypical or theoretical kayaks. ... > I can't imagine taking my Ellesmere and adding internal flotation that would > have a great effect. There's little room between the seat and the hull on the > sides. I could take up volume around my legs, but it would have to be > planned with ease of entry and exit in mind. In the end I doubt that a > significant improvement in flooded stability would be there. An improvement, > but not significant enough for me to bother. If you're talking about a kayak > with a 28 inch beam, that would be different, but that's not a typical kayak. Since one of my kayaks has a 37" beam and another is 31", there is plenty of space to fit substantial amounts of flotation space although the manufacturers have not seen fit to do this. So for those boats I am considering this both from a theoretical and practical perspective. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
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