I'm looking to move up from my SOTs to a decked kayak. I've been looking at a lot of boats and keep running into the same problem. That is that kayaks are small and I'm big...6'-3", 240lbs with size 13 feet. One of the first things I look at is the weight of paddler the kayak was designed for. I know about buoyancy and displacement and why a boat floats but don't understand some kayak capacity specs. Take the Northwest Synergy RM or others like it...a 16'+ boat with a load capacity of 340lbs but their specs say it's ideal for a 120-200lb paddler. I would assume a good kayak would have the paddler sitting at or very near it's CG. So except for all the effects that any weight would have on it...like riding lower in the water and maybe handling sluggishly...why would the boat care if the weight is the paddler or 100lbs extra pounds of gear?...assuming it's distributed evenly. Should I not even consider a boat like this and look only at those rated to carry a 240lb paddler? There are not many that do...I don't want to paddle a 20' double by myself. dave *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
At 08:10 PM 3/30/00 -0500, David Seales wrote: >I'm looking to move up from my SOTs to a decked kayak. I've been looking at >a lot of boats and keep running into the same problem. That is that kayaks >are small and I'm big...6'-3", 240lbs with size 13 feet. I'm close to 300 pounds, and only a touch shorter. It is tough to find an adequate boat for guys our size range, but there are some out there. >One of the first >things I look at is the weight of paddler the kayak was designed for. I >know about buoyancy and displacement and why a boat floats but don't >understand some kayak capacity specs. Join the club. At the risk of setting off a long lecture from some of the techie types, I have to say that no one else really understands capacity specs either, or at least that's the impression I get from looking at them. Take my Old Town Heron. Up until this year, the capacity was given by the manufacturer as 275 lbs. (It's now 325, I think.) I frequently paddle it at about 325 lbs, and have had it as full as 375. I will admit, it gets a little sluggish at that weight. OK, the Heron is 16'5" by my tape measure, and about 24" wide. You look at the Eddyline Wind Dancer -- one of the best boats for big guys -- and at 17'1" and 24 inches, with a freeboard an inch deeper than the Heron, it's listed at 450 lb. capacity by the manufacturer. I fail to see where a boat that's only slightly larger than the Heron can have that much more capacity differential. So, from that alone we can see that capacity figures can be full of gas and wishful thinking. Many manufacturers don't give capacity specs at all, because of the amount of gas in so many of them. So, what determines manufacturer capacities? Probably not the designers, who know how much load the boat can handle, but the marketing and legal people. The WS Sealoution II XL is considered one of the better big guy boats by some, yet WS only lists it at 250 pounds capacity -- there's a lot of reserve there, but probably they want to leave themselves some liability leeway, I say cynically. >Take the Northwest Synergy RM or >others like it...a 16'+ boat with a load capacity of 340lbs but their specs >say it's ideal for a 120-200lb paddler. I would assume a good kayak would >have the paddler sitting at or very near it's CG. So except for all the >effects that any weight would have on it...like riding lower in the water >and maybe handling sluggishly...why would the boat care if the weight is >the paddler or 100lbs extra pounds of gear?...assuming it's distributed >evenly. Again, we run the risk of bringing out the slide rule types, but in general boats do handle better if their weight is spread out, rather than concentrated. A small difference in balance can make a big difference in handling. In the case of my boat, I keep a drybag full of spare clothes much of the year, just in case I need something dry. I can notice a considerable difference in tracking in windy conditions by moving that bag from the front hatch to the rear. But, in general, having the weight concentrated won't make that much difference. >Should I not even consider a boat like this and look only at those >rated to carry a 240lb paddler? There are not many that do...I don't want >to paddle a 20' double by myself. Most important is fit, if the boat appears to have adequate capacity. There are a few rotomolds out there that have enough capacity for guys like us and still have a cockpit that's adequately comfortable. I like my Heron -- there isn't much better, in my opinion, in rotomolds, and the more I look at the plastic competition the less thrilled with them I am. I was really unimpressed with a CD Storm I tried on recently; my possible replacement list in plastic is now down to two boats that I haven't tried, an OT Millenium and a Necky Narpa. I'm not familiar with the NW Synergy. But, I don't think my next boat is going to be plastic. There are several more big guy boats available in fiberglass. I have to suggest that you should take a look at the bigger Neckys -- Looksha IV HV, Tesla NM, etc. Mike Neckar is another one of us big guys, and he has boats that are friendly to us. If all else fails, there's the Necky Pinta, which certianly has capacity and then some, without being a 20' double -- but that boat is probably on the big side for either you or me. There are others. You might like to look at the comparisons of boats for big guys on my web page: http://www2.dmci.net/users/wesboyd/bigguy.htm I should probably note that the list of boats on that page needs some updating. Prices have changed, at least one no longer appears to be available, and there are a couple of new ones out there. Rest assured that there are a few of us big kayakers around. We have to stick together. -- Wes *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Dave wrote; (SNIP) >One of the first > things I look at is the weight of paddler the kayak was designed for. I > know about buoyancy and displacement and why a boat floats but don't > understand some kayak capacity specs. Take the Northwest Synergy RM or > others like it...a 16'+ boat with a load capacity of 340lbs but their specs > say it's ideal for a 120-200lb paddler. I would assume a good kayak would > have the paddler sitting at or very near it's CG. So except for all the > effects that any weight would have on it...like riding lower in the water > and maybe handling sluggishly...why would the boat care if the weight is > the paddler or 100lbs extra pounds of gear?...assuming it's distributed > evenly. Should I not even consider a boat like this and look only at those > rated to carry a 240lb paddler? There are not many that do...I don't want > to paddle a 20' double by myself. I won't discuss that part of boat buying that involves fitting the boat to your frame. It should be fairly obvious that you should look elsewhere if you can't get in the boat. First a definition. Displacement = the total weight of the boat, gear and paddler. In a better world every boat would be designed to a specific displacement range and would perform best at that displacement range. My research shows that some paddlers can detect differences in performance within a range of +10 / - 20% of the designed displacement (nice round numbers for simplicity so do not claim that I said they were absolute. Testing human perceptions is not science it is statistics). In other words, overload a boat by 10% and you might begin to notice that it performs more sluggishly (turns slowly and feels "slow", etc.) . Under load by 20% and you might notice that it handles differently (blows around too much. has marginal stability etc. ) Why? Because the form factors (Prismatic coefficient, block coefficient, waterline length, waterline beam, etc. etc.) that affect performance change with increased or decreased immersion. I have not yet seen a sea kayak that had consistent form factors and immersed dimensions regardless of load. Unfortunately we do not have a better world. Some designers do not design to a specific displacement. Most salespeople (and a lot of builders) don't even understand the concept. Dave recognizes an important the point that the boat doesn't care if the weight comes in the form of gear or paddler. Displacement includes everything. A fifty pound boat with a 200 pound paddler has the same displacement as a 200 pound boat with a fifty pound paddler. Remember the old trick question from school, "Which is heavier, fifty pounds of lead or fifty pounds of feathers?" It really doesn't matter how you distribute it from a resistance standpoint (it does matter from a stability and pitching moment standpoint). In the absence of designer information how do you select a boat that has suitable displacement for you? Given a normal configuration (no extreme or unusual hollows or bumps in the hull) most recreational kayaks will perform reasonably well if their fatness ratio falls between 0.95 and 1.6. The fatness ratio = Volume/ (0.1 * Waterline Length) ^3 This does not mean that a boat instantly becomes a water pig above or below the figures given, it just means some people might begin to notice a difference. Noticing the varies between people. Some psychokineticists (easy for you to say :-)) claim a "just noticeable difference" is +/- 10% of effort 50% of the time. For the typical recreational paddler that seems fair to me. I know that some paddlers claim the ability to detect very subtle differences in performance (usually much smaller and with greater accuracy than a test tank) but I remain unconvinced. Cheers, John Winters Redwing Designs Web site address, http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Winters wrote: > In the absence of designer information how do you select a boat that has > suitable displacement for you? Given a normal configuration (no extreme or > unusual hollows or bumps in the hull) most recreational kayaks will perform > reasonably well if their fatness ratio falls between 0.95 and 1.6. > > The fatness ratio = Volume/ (0.1 * Waterline Length) ^3 > > This does not mean that a boat instantly becomes a water pig above or below > the figures given, it just means some people might begin to notice a > difference. [snip] Some psychokineticists (easy for you to say :-)) claim a > "just noticeable difference" is +/- 10% of effort > 50% of the time. For the typical recreational paddler that seems fair to me. [snip] John, I assume the formula is designed for use with cubic feet for volume and feet for waterline length (or, cubic meters and meters), rather than gallons and feet, yes? Also, I assume the volume in the formula is total enclosed volume of the kayak, and not just the volume below the waterline, yes? (Seems that if it is total enclosed volume, the shape of the cross-section might influence the "feel" of the boat, also, but perhaps it is assumed the kayak has an "average" cross-sectional form.) -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
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