Jeez, Doug don't start T-H-I-N-K-ing on us. I for one love your shoot-from-the-hip, tell-it-like it-is style. I find it refreshingly honest. Sure some are going to be offended by your truths but if they don't like it they can write back (like I am going to do later in this post) and give their own take on the truth. Message: Deal with it! Please, lets not stifle Doug's freedom to say whatever crosses his mind uncensored. Doug, I really enjoyed your description of the kayak you own and love while also describing all its warts. If all paddlers were as forthcoming as you, I 'd say Sea Kayaker should get their kayak reviews from owner/experts (as well as expert paddlers using the kayak for the first time as they often do now. No paddler using a kayak for a few times can know about all the warts but an owner who paddles a lot and in all conditions often does. Doug, I think you are wrong about the veil between layers of Kevlar or Graphite but would like to hear the arguments (and if possible test results) for laminating that way before making up my mind. Why not do it that way between glass fabrics too if it really is advantageous? I certainly don't think it is a good idea to mix materials as different as Kevlar and Graphite cloth in layers because of differences in their modulus of elasticity (which will make them prone to sheer between the layers). Maybe a glass veil between different materials might help prevent this sheer failure (and this may be what your source was actually talking about--this often surrounds graphite reinforcements to Kevlar kayaks). I always thought it was just to hold the unidirectional fine strands of graphite (that are easily spread apart) in place during the laminating. I suspect that the veil between layers of the same material may actually make a weaker layer and encourage delaminating. I like Kevlar and Graphite mixed in the weave of the same hybrid fabric. That way the differing materials can't delaminate and allows you to gain the best qualities of both materials (they work together rather than fighting each other and shearing apart at the boundary). Maybe this is the time to talk about Graphite as a kayak building material. For sea kayaks I like it better than Kevlar because the most likely damage to a sea kayak is going to come from folding it rather than from a blow. Graphite is very stiff for a given thickness. Its downside is that it will fail catastrophically if it gets bent enough (it doesn't have as much tensile strength as Kevlar but is much stiffer and harder to bend--so more brittle). Like Kevlar if you make it the same weight as fiberglass it will be tougher than glass but normally it is used to hold the kayak into shape with a thin lightweight laminate. Then it will be more vulnerable than glass to blows but a lot less likely to fold up than a Kevlar kayak of the same weight. By mixing them together in the weave of a fabric you can use that hybrid to make a laminate that doesn't fold easily (due to the graphite) but will take a tremendous blow without serious damage (due to the Kevlar). I believe that Kevlar and Graphite that are sold for laminating with resin have surface treatments that make them bond well with the resin (not necessarily slippery on each other once in a laminate). I for one would rather not add a veil layer between them that would both add weight and a potential sheering layer between the woven fabrics (although it would build thickness more cheaply). I am open to more feedback on this issue from an expert on these fabrics though. I haven't done any scientific destruction testing myself with veil in various laminates. The experimentation I have done aren't very scientific either, they consists mostly of hitting it (usually the cut-outs for rear hatches) as hard as I can with a hammer and folding them as far as I can to see how easy they are to bend pound for pound and how they fail (when you can get them to fail at all). Duane, glad to hear they were really 8 to 12 footers. I thought they must have been bigger (or there are some really mean 5 to 7 footers down there in California) from your description of what happened to you when you bailed. Matt Broze http://www.marinerkayaks.com *************************************************************************** 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/ ***************************************************************************
Matt Broze wrote: > > ... > I like Kevlar and Graphite mixed in the weave of the same hybrid fabric. > That way the differing materials can't delaminate and allows you to gain the > best qualities of both materials (they work together rather than fighting > each other and shearing apart at the boundary). > ... I have seen the results of Matt's hammer and folding tests, and laminates with a carbon-kevlar weave seem to be very resistant to abuse of this type. However some time ago John Winters expressed serious reservations about this material (the details of which I have forgotten). What are the potential drawbacks of a carbon-kevlar weave? Has anyone subjected a kayak made with this material to long-term abuse? Enquiring minds want to know... Dan Hagen Bellingham, Washington *************************************************************************** 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/ ***************************************************************************
Dan wrote; > > I have seen the results of Matt's hammer and folding tests, and > laminates with a carbon-kevlar weave seem to be very resistant to abuse > of this type. However some time ago John Winters expressed serious > reservations about this material (the details of which I have > forgotten). What are the potential drawbacks of a carbon-kevlar weave? > Has anyone subjected a kayak made with this material to long-term abuse? > Enquiring minds want to know... > The Swift Canoe Company tested boats built using these types of materials in their rental fleets. The results disappointed them. The boats sometimes lasted less than a few months where their normal Kevlar boats last as much a five years in their fleet. Their "mixed" laminate boats ("S" Glass/carbon/Kevlar) last two to three years. Impacts usually resulted in visible delamination running along the carbon fibers and extending well beyond the impact point. Since the company provides a lifetime guarantee you can appreciate that they would not continue using the materials even though the data from lab tests looked promising. Admittedly the use (and abuse) probably exceeds that which most sea kayaks will get. Now, before anyone goes rushing off in all directions recognize that fabrics come in an extraordinary range of weaves etc. What Matt tested may not have much resemblance to what Swift tested nor did the test methods have a lot of similarity. I recall Darryl Lideigh beating on his mat canoes with a hammer and saying they were just as strong as anyone's else's Kevlar canoes and even challenging other builders to duplicate his hammer test. There are tests and there are tests. While the rental fleet test hardly qualifies as a controlled and repeatable test procedure it does have the merit of having some similarity to "real life". I recall how, in the yacht business, a lot of things that worked well in the lab just "couldn't be done" on the shop floor and simply did not work out in the "real world". It tends to humble one to have some old fart with forty years experience show you (the snotty nosed kid) that your brilliant idea that has lots of science behind it just won't cut it. Maybe I am saying that because I am closing in on forty years of experience :-) So, yes, I have reservations about these mixed weave fabrics and at least one of the weavers strongly recommends against them in canoes. That does not mean they don't "work" or won't work. It just means that one has to exercise caution with construction techniques that do not have a long term proven track record. They may serve quite well for some uses but not others just a mat serves quite well for some uses but not others. As I have mentioned before, we really don't know how strong "strong enough" is. Paddlers and builders seem to have a lot of opinions though. You can take 'em or leave 'em. 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/ ***************************************************************************
I am suspicious about the structural efficience of a mixed weave. If the fabric is on the surface of a deformed laminate, all of the fibers will have the same strain. The stiffest fibers will carry most of the load. (stress = strain x stiffness). Thus, the stiffer carbon fibers in the weave will have the highest stress and carry most of the load. The kevlar won't get involved in carrying the load until the carbon fibers break. >From this assessment, it appears that, to make best use of the carbon fiber, the outer surface should be all carbon fiber. Using the more elastic kevlar in the weave could prevent catastrophic failure of the structure, but the stiff carbon fibers will fail at smaller deflections --before the kevlar is called upon to take its share of the load. On the other hand, if the kevlar were laminated between skins of carbon fiber, the majority of the composite stiffness would come from the stiff outer skins. This would be sort of a thin sandwich structure, one with a core of kevlar instead of foam or honeycomb paper. bob phillips SE MI *************************************************************************** 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/ ***************************************************************************
Dan Hagen wrote: > What are the potential drawbacks of a carbon-kevlar weave? > Has anyone subjected a kayak made with this material to long-term abuse? Not a kayak, but... In the latest Banff Festival of Mountain Films, (the "Best of" is currently touring) there's a film about four Yugoslav adventurers who cross the Arctic from Russia to Canada through the North Pole. They started with ten sleds made of carbon- Kevlar weave. They ended with three. A couple or three were lost through open leads in the ice. The others disintegrated from the pounding of being hauled across the ice by the men on skis. Other than for the material chosen, they were pretty much standard gear pulks. They hauled the gear for 12-16 hours a day, then stopped to repair them, eat and sleep. The men were 51, 47, 42 and 31 years of age - so there's hope for some of us (the 51 year old got most of the film time and was tough as nails). Watch for the films and catch them if you can. You'll never look at carbon-Kevlar weave the same way again <G>. Mike *************************************************************************** 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/ ***************************************************************************
In a message dated 2/8/00 7:02:24 PM Pacific Standard Time, michaeldaly_at_home.com writes: << They started with ten sleds made of carbon- Kevlar weave. They ended with three. A couple or three were lost through open leads in the ice. The others disintegrated from the pounding of being hauled across the ice by the men on skis. >> Paddlewisers, I hate to refer to things I saw on TV, but I can't resist here. I saw a special about 3 guys who crossed Greenland. Two of them towed plastic white water kayaks full of gear over the ice and snow all the way across the country. These kayaks were later used to descend a river at the end of their journey. The third guy in this group had an expedition sled that was made of fiberglass. The sled was shattered to pieces, while the kayaks held up fine. In another special, native porters hired for a white water expedition in some exotic country got mad and quit. The white water guys ended up dragging their plastic white water kayaks full of gear miles on a dirt and rock trail. Afterwards, they paddled down class V white water in those kayaks. Sometimes the best material is the simplest. Duane Strosaker <A HREF="http://members.aol.com/pirateseakayaker/index.html">Pirate Sea Kayaker</A> *************************************************************************** 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/ ***************************************************************************
Strosaker_at_aol.com wrote: > In a message dated 2/8/00 7:02:24 PM Pacific Standard Time, > michaeldaly_at_home.com writes: > > << They started with ten sleds made of carbon- Kevlar weave. They ended with > three. A couple or three were lost through open leads in the ice. The others > disintegrated from the pounding of being hauled across the ice by the men on skis. >> > > I saw a special about 3 guys who crossed Greenland. Two of them towed > plastic white water kayaks full of gear over the ice and snow all the way > across the country. These kayaks were later used to descend a river at the > end of their journey. The third guy in this group had an expedition sled > that was made of fiberglass. The sled was shattered to pieces, while the > kayaks held up fine. > [...] > Sometimes the best material is the simplest. A plastic sled would almost be right for the Yugoslavs, but I doubt I would trust it at the lowest temperatures they faced. Even tupperwave would become brittle at those temperatures. The warmest (above 0C) would have been ok. I don't know what the paddlers were hauling across Greenland, but the Yugoslavs had a couple of hundred pounds of gear in each sled! Mike *************************************************************************** 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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