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Fiberglass vs plastic
I'm still looking to purchase my first kayak. I'm kinda partial to
the CD Scirocco. I'll no doubt not have enough experience before I make a purchase to reasonalby tell the difference between a fiberglass craft and a plastic one as far as performance goes. To me, the price difference is not that geat. I kinda like the weight difference for loading and unloading off the truck. I'm told the plastic is much better at taking the abuse of rocks and oyster bars. So, I'd like to pose a couple of questions to those more experience kayakers: Just how much difference is there in performance between plastic and fiberglass? How fragile are the fiberglass kayaks to abrasion that I'm likely to encounter kayaking in Florida estuaries? Thanks for any opinions. bb |
Fiberglass vs plastic
Fiberglass is usually stiffer than the plastic, and this usually equates
into better performance. Most paddling will do little more than an occasional scratch on a glass boat. The light weight is a bonus. Unless you plan to surf frequently on a boulderey beach, choose the glass. |
Fiberglass vs plastic
On Fri, 07 May 2004 15:13:26 GMT, bb wrote:
I'm still looking to purchase my first kayak. I'm kinda partial to the CD Scirocco. I'll no doubt not have enough experience before I make a purchase to reasonalby tell the difference between a fiberglass craft and a plastic one as far as performance goes. To me, the price difference is not that geat. I kinda like the weight difference for loading and unloading off the truck. I'm told the plastic is much better at taking the abuse of rocks and oyster bars. So, I'd like to pose a couple of questions to those more experience kayakers: Just how much difference is there in performance between plastic and fiberglass? How fragile are the fiberglass kayaks to abrasion that I'm likely to encounter kayaking in Florida estuaries? Thanks for any opinions. bb Huge performance difference. If money is no object than go glass no question. |
Fiberglass vs plastic
Where I paddle (Hudson, Mohawk rivers, Northeast lakes, etc) I often have to
launch from concrete boat ramps or rocky shores, so for me plastic is a better choice. My Pungo is mightily scarred, but I don't really worry about it the way I would if I had an expensive glass boat. ****************************** Got wood? Check out my exotic hardwood pennywhistles at fair prices...http://www.Busmanwhistles.com |
Fiberglass vs plastic
bb wrote in message . ..
I'm still looking to purchase my first kayak. I'm kinda partial to the CD Scirocco. I'll no doubt not have enough experience before I make a purchase to reasonalby tell the difference between a fiberglass craft and a plastic one as far as performance goes. To me, the price difference is not that geat. I kinda like the weight difference for loading and unloading off the truck. I'm told the plastic is much better at taking the abuse of rocks and oyster bars. So, I'd like to pose a couple of questions to those more experience kayakers: Just how much difference is there in performance between plastic and fiberglass? How fragile are the fiberglass kayaks to abrasion that I'm likely to encounter kayaking in Florida estuaries? Thanks for any opinions. bb Scirroco is a fine boat, The Gulf stream is a beauty too. Like one poster said the performance difference in similar boats between glass and plastic is quite noticeable. Plastic scratches much more easily but glass does not like bumps. Glass can be repaired with reasonable ease, Though my patches are noticeable. I own some of each flavour ( Glass and Plastic ) I use them all . I paddle the plastic Capella most but when I am off on my own I like the NDK . For speed the NDK has it but the Explorer is a foot and 2 inches longer so that skews things. The NDK Romany is very similar to the Capella and has comparable rocker; it too is a faster boat than the Plastic P & H Capella ; but not much. We have lots of rocky beaches here in Newfoundland. I would start with a plastic boat if you intend to do a lot of paddling here. If I could count on a beach or slip most of the time I would go glass. The only time you will see a speed difference is when you are paddling with seasoned paddlers that are fast. When I drop my plastic Capella from the roof rack I hardly swear at all. I dropped the NDK last week , Glad Mom was not there. The boat was not hurt. Eddy Line seames to have come up with a boat that is the best of both worlds and light as a feather. A friend of mine bought a Night Hauk , Now if they made a nice Greenland type craft I would look at it. Good luck. If they are close to the same price and you are carefull the glass boat may do you a lifetime. But plastic can take the odd bang. |
Fiberglass vs plastic
Alex Horvath wrote:
I have paddled a glass boat and where I had no choice but to land on a steep rocky beach (with minimal surf), I would get out while the boat is in the water (you get good at this after a while) and I tie the boat to a large rock preferably in the water. This way the kayak is in the water while I unload it. Of course, there is a risk that the rope slips off the rock while I am not looking and floats away or that I drop my gear into the water as I'm unloading it. I have heard of people carrying small anchors but this is a significant amount of weight. Anyone else do something similar? This may seem somewhat extreme but a loaded glass boat on rocks in the surf zone will take quite a beating. That sounds like an awful lot of gyrations to go through, plus you risk soaking or losing gear and possibly losing your boat. More importantly, you also risk personal injury by making trips back and forth in rocky water. Just land the thing and drag it up on the rocks. It takes a lot longer for your body to heal than it does to repair a few gelcoat scratches. Gelcoat is also a lot cheaper than medical bills. |
Fiberglass vs plastic
Alex Horvath ) writes:
Anyone else do something similar? This may seem somewhat extreme but a loaded glass boat on rocks in the surf zone will take quite a beating. Yes. It's always better to load and unload the boat in the water. It's also better if you can get in and out of a small boat with the hull afloat parallel to the shore. I've been to a couple of used boat sales, beat up rentals being sold by a canoe manufacturer. The hulls are badly scratched up. That may not be a problem for knocking about on your own but if you are on a trip with a group and their hulls are smooth you are easily paddling 10% more to keep up. That's like paddling 11 hours to their 10. BW the boat rental business looks like quite a racket. The boats are rented and get really beat up, then they are sold for half the original purchase price. It's not just the renters who beat the boats up. I've seen employees tossing them about like fire wood. The bottoms of the hulls I've seen at the sales are criss-crossed with deep gouges - more than a 10% difference in paddling effort there. :( -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
William R. Watt wrote:
That may not be a problem for knocking about on your own but if you are on a trip with a group and their hulls are smooth you are easily paddling 10% more to keep up. Exactly where did that figure come from? The tests I've seen indicate that scratched hulls have ~2-5% more drag smooth hulls, with badly scarred plastic hulls with lots of "hairies" being at the high end. The difference with fiberglass boats is minuscule. That's like paddling 11 hours to their 10. No, it's not like that at all. Even if your 10% figure is correct, it pertains only to surface friction on the hull. That's only one component of the total drag that must be overcome by the paddler. Wind resistance and especially wave making resistance can be very substantial components of total drag, depending on boat speed and weather conditions. Realistically, a scratched hull will require you to paddle ~1-2% harder than a smooth one. Unless you're racing, you'll never notice the difference. |
Fiberglass vs plastic
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Fiberglass vs plastic
Brian Nystrom ) writes:
William R. Watt wrote: That may not be a problem for knocking about on your own but if you are on a trip with a group and their hulls are smooth you are easily paddling 10% more to keep up. Exactly where did that figure come from? The tests I've seen indicate that scratched hulls have ~2-5% more drag smooth hulls, with badly scarred plastic hulls with lots of "hairies" being at the high end. The difference with fiberglass boats is minuscule. the reference is long gone. it said one season's scratches add 5% to hull resistance. That's like paddling 11 hours to their 10. No, it's not like that at all. Even if your 10% figure is correct, it pertains only to surface friction on the hull. That's only one component of the total drag that must be overcome by the paddler. Wind resistance and especially wave making resistance can be very substantial components of total drag, depending on boat speed and weather conditions. Realistically, a scratched hull will require you to paddle ~1-2% harder than a smooth one. Unless you're racing, you'll never notice the difference. where does that 1-2% figure come from? at sustained (cruising) paddling speeds hull resistance is still the biggest component of total hull drag when comparing identical boats. there are some numbers in a file on my website under "Boats" on average hull, wind, and wave resistance, and energy consumption. a paddler can't put out the power needed to maintain high wave making resistance speeds for any length of time. it's a concern for racers. your point about wind and wave resistance is well taken. however, considering the money spent on paddles to reduce effort, the scratches on the hull matter. I don't think 10% is out of order in anything less than rough conditions. I was trying to be conservative. I don't have figures for paddlers but cruising sailors experince moderate conditions most of the time. Rough conditions most of the time would pretty well eliminate such passtimes as paddling and sailing. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
Alex McGruer ) writes:
There remains the ugly fact , you are going to have to bring that boat ashore and sometimes a host of issues will make you follow the wave ashore and land on a beach. Most rocks will be rounded but it is still a bump. Got me there. All my paddling is on lakes and rivers with no swells or surf, and in open boats which are easier to get in and out of. I can see where Kayaks would present special problems. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
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Fiberglass vs plastic
"Michael Daly" ) writes:
On 28-May-2004, (William R. Watt) wrote: at sustained (cruising) paddling speeds hull resistance is still the biggest component of total hull drag when comparing identical boats. there are some numbers in a file on my website under "Boats" on average hull, wind, and wave resistance, and energy consumption. a paddler can't put out the power needed to maintain high wave making resistance speeds for any length of time. Nowhere on your website could I find info to support this. look under Boats, Paddling, first item (Speed, Resistance, Energy). I'd appreciate seeing more specific data. You simply claim that wave making resistance is not significant at paddling speeds. For a kayak designed for optimal length at its cruising speed, skin resistance and wave resistance are roughly equal. I think you mean "wave making resistance". If you have a source for speed and hull resistance numbers I'd appreciate seeing it. Wind and wave resistance would be even better. If a paddler is routinely using a kayak under conditions where skin friction dominates, they'd be better off using a shorter kayak. If they are routinely pushing against wave-making resistance, they should get a longer kayak. Sorry it's not an inverse relation. I don't think 10% is out of order in anything less than rough conditions. You're still talking thru your hat, Willy. Unless you can cough up a valid reference, I'll go with Brian's numbers. Brian didn't provide any data. You can work it out from the data on my website. I'd be interested in seeing more precise data than what I have. I could only find generalizations at the time. You should get out more. Rough conditions are when kayaking gets interesting. The fact is that kayaks are used in rough conditions (as would be defined by marine architects) _most_ of the time. And where do you get that data, in your dreams? -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
William R. Watt wrote: Brian Nystrom ) writes: William R. Watt wrote: That may not be a problem for knocking about on your own but if you are on a trip with a group and their hulls are smooth you are easily paddling 10% more to keep up. Exactly where did that figure come from? The tests I've seen indicate that scratched hulls have ~2-5% more drag smooth hulls, with badly scarred plastic hulls with lots of "hairies" being at the high end. The difference with fiberglass boats is minuscule. the reference is long gone. it said one season's scratches add 5% to hull resistance. And how was that determined? What exactly constitutes "one season's scratches"? Though I don't doubt that you have a source for this information, I have to wonder about the accuracy of such generalities. It sounds a lot more like opinion than fact. That's like paddling 11 hours to their 10. No, it's not like that at all. Even if your 10% figure is correct, it pertains only to surface friction on the hull. That's only one component of the total drag that must be overcome by the paddler. Wind resistance and especially wave making resistance can be very substantial components of total drag, depending on boat speed and weather conditions. Realistically, a scratched hull will require you to paddle ~1-2% harder than a smooth one. Unless you're racing, you'll never notice the difference. where does that 1-2% figure come from? It's roughly half of what the test I saw indicated for hull drag. Wavemaking resistance is no small factor, even at cruising speed. Add wind resistance and the effect of scratches becomes even less significant. at sustained (cruising) paddling speeds hull resistance is still the biggest component of total hull drag when comparing identical boats. That's simply not true. For a kayak, suface drag is relatively small. Kayaks are typically paddled pretty close to their theoretical hull speed. A typical 17' kayak will have a theoretical hull speed of ~5-5.25 knots and will probably be paddled at ~3.5-4 knots regularly. At least that's true of my boats. At that speed, wavemaking drag is the major drag component. One can readily feel the exponential increase in output necessary to incrementally increase speed. there are some numbers in a file on my website under "Boats" on average hull, wind, and wave resistance, and energy consumption. a paddler can't put out the power needed to maintain high wave making resistance speeds for any length of time. I realize that, but it doesn't mean that wave making resistance isn't the major component of the total drag. it's a concern for racers. your point about wind and wave resistance is well taken. however, considering the money spent on paddles to reduce effort, the scratches on the hull matter. IMO, the emphasis on ultralight paddles is misplaced. I get less fatigued from paddling with a 30 oz. Greenland stick than with 24 oz. Euro. I don't think 10% is out of order in anything less than rough conditions. I was trying to be conservative. I don't have figures for paddlers but cruising sailors experince moderate conditions most of the time. Rough conditions most of the time would pretty well eliminate such passtimes as paddling and sailing. Are you kidding? Fla****er paddling is boring, unless the point is just to relax and take in the view. My boats come into their own when the conditions get a bit rough. Rough water is exhilarating! Wind and waves are where it's at! Perhaps that's the difference between kayakers and a canoeists? We apparently have very different perspectives based on what we do on the water. |
Fiberglass vs plastic
William R. Watt ) writes:
"Michael Daly" ) writes: On 28-May-2004, (William R. Watt) wrote: at sustained (cruising) paddling speeds hull resistance is still the biggest component of total hull drag when comparing identical boats. there are some numbers in a file on my website under "Boats" on average hull, wind, and wave resistance, and energy consumption. a paddler can't put out the power needed to maintain high wave making resistance speeds for any length of time. Nowhere on your website could I find info to support this. look under Boats, Paddling, first item (Speed, Resistance, Energy). I'd appreciate seeing more specific data. An average person can sustain 1/20 horsepower. When a canoe or kayak is powered by 1/20 hp in a dead calm the power is overcomimg 4 pounds of hull friction resistance and 0.05 pounds of hull wave making resistance. If 10% of the friction resistance is due to scratches, that's 0.4 lb compared to the 0.05 lb wave making resistance. Mike wrote he thinks the friction and wave making resistance would be equal. For that to happen the paddler would have to be sustaining 1/5 horsepower, or 4 times as much. The boat would be going almost twice as fast. Athletes can do that. In short bursts athletes can produce 1/2 hp. In "Sea Kayaking" J Dowd's data assumes the paddler sustains 0.03 hp. The discrepency likely is due to a different boat being used at the same speed. In a 10 knot headwind the wind and resulting waves are producing 0.01 hp. If hull scratches increase friction resistance by 10%, the paddler has to produce 10% more hp to overcome it and keep the boat moving at the same speed in a dead calm. In a 10 knot headwind the extra power drops to about 7% of the total paddler output. More precise data than what I have available could affect the result. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
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Fiberglass vs plastic
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Fiberglass vs plastic
"Michael Daly" ) writes:
On 28-May-2004, (William R. Watt) wrote: Sorry it's not an inverse relation. ??? The more you say about small craft hydrodynamics, the more I realize how little you understand. Skin friction increases with length, while wave-making resistance decreases with length. Minimum total resistance is where the sum of the two is minimum. Skin friction does not increase monotonically with length. It does increase monotonically with the product of surface smoothness and wetted surface area. Wetted surface area in a dead calm is a function of displacement and hull shape but not a well-defined mathematical function, and it is complicated by waves. There are quite a few indicators of hull shape such as length-to-beam ratio, block coefficient, prismatic coefficient, and girth. Brian didn't provide any data. He said 2% or so. A percentage is not data. A percentage is a calculated number. You have no such data that I've seen. Where do you have the data that indicates how much resistance is due to scratches? And where do you get that data, in your dreams? "The Shape of the Canoe" by John Winters. the hull resistance data on my website is from Winters' website. where he got the data I do not know. at one time he was collaborating with a university in Australia. the fellow at the university has posted in this newsgroup. Its been a few years and I can't recall the university. the "Winters" data is very general. I would like to see data specific to sea kayaks. the wind and wave resistance data is from a book on sea kayak cruising. it also appears to me to be pretty general. you are not basing your arugment on data, but on your impressions. I am basing my argument on actual data which I admit is pretty general. I know what you are trying to express, that within a narrow range there is a local optimum. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
"Michael Daly" ) writes:
On 28-May-2004, (William R. Watt) wrote: An average person can sustain 1/20 horsepower. When a canoe or kayak is powered by 1/20 hp in a dead calm the power is overcomimg 4 pounds of hull friction resistance and 0.05 pounds of hull wave making resistance. Where on earth do you get that breakdown? Friction resistance 80 times wave resistance? "Winter's" data at hull speed and total resitance equal to 1/20 hp. ie the data graphed on Winter's web site. How can you make such a claim without any reference to the dimensions of the kayak or canoe? Are you trying to suggest that my WW kayak has the same resistance as my sea kayak? as I have pointe out a number of times in this discussion that is precisely the weakness in the data on Winters'w web site I would like to see refined. DO YOU HAVE THAT DATA? Mike wrote he thinks the friction and wave making resistance would be equal. For that to happen the paddler would have to be sustaining 1/5 horsepower, or 4 times as much. Why? where do you get that number? the data on Winters' webiste. Athletes can do that. In short bursts athletes can produce 1/2 hp. Cyclists can put out those kinds of power levels. However, if you're not using your legs, horsepower is harder to generate. Elite paddlers can put out about 0.3 hp. A fit recreational paddler can put out about 0.08 to 0.1 hp. according to teh data on Winters' webiste you you have just destroyed your earlier argument. at less than 1/20 hp the "boat" (canmoe or kayak or whatever Winters' data represents) is harldy moving at all. sorry, numbers don't lie. provided the numbers measure what we want and I'm sure the numbers on Winters' website measure speed and hull resistance of a paddled boat, although we don't know exaclty which paddled boat. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
Here are the data from the graph on the John Winters website. "knots" is speed through the water in a dead calm, a knot is 15% more than a mph "friction" is hull surface friction resistance "wave" is hull wave making resistance "total" is the sum of the two kinds of hull resistance "hp" is the horsepower needed to sustain that speed at that total resistance knots: 2 2.6 3 3.5 4 4.6 5 5.5 6 lb friction: 2 2.5 2.75 4 4.75 5 7 8 9 lb wave: 0 0 0 .05 0.75 3 7 15 20 lb total: 2 2.5 2.75 4.5 5.5 8 14 23 29 ================================================== ========= hp: .01 .02 .03 .05 .07 .10 .20 .40 .53 -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
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Fiberglass vs plastic
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Fiberglass vs plastic
"Michael Daly" ) writes:
..For a constant displacement, wetted surface area changes directly with length. Why complicate things? because it's not true In his book, he specifically states that there is no significant difference in the behavior of canoe and kayak hulls. They come in the same range of lengths and vary only in width. Most of the other parameters, such as block and prismatic coefficients are in the same ballpark as well. yes, compared to oil tankers, canoes and kayaks are in the same ballpark. but compared to each other and relative to the low power source, canoes and kayaks differ in performance. in my experience kayaks are faster than canoes, their main attraction as far as I can tell. a lot of money goes into advertising the differences among canoes and kayaks. I would like to see more precise data. I suspect the subject has been studied by, say, Soviet sports scientists, but they are not sharing their data. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
"Michael Daly" ) writes:
Also, this data is suspect - most kayaks in the Sea Kayaker reviews are not in this range. For a recent review of the Solstice GT: Speed 2.0 3.0 4.0 4.5 5.0 6.0 (kt) Solstice GT 0.96 2.01 3.66 5.31 8.06 14.23 (lb) As you can see, the data you provide is quite a bit higher than what the Solstice shows. Here's some mo http://www.greatlakeskayaker.ca/speedVsResistanceGraphs.htm (I make no promises whether this web page will show in anything other than Internet Explorer - sorry, it's an exported Excel spreadsheet page). thanks. I'll take a look. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
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Fiberglass vs plastic
Winters' current website is www.greenval.com. The graph of resistance vs
speed is gone. He now has resistance vs speed-to-length ratio which is a way to include length in the graph. From a quick look today it's still not clear whether the data is for canoes or kayaks. I'll try to get back to the library and copy some data points, also see if I can copy the greatlakeskayaker data. It may be a while before I get around to redoing the calculations with this data. In the meantime the best we have is a 7% increase in effort due to hull scratches. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
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Fiberglass vs plastic
William R. Watt wrote:
in my experience kayaks are faster than canoes, their main attraction as far as I can tell. While this is certainly what attracts some kayakers, I'd say the main attractions vs. canoes are the kayaks inherent seaworthiness and it's ability to handle a broad rain of weather and water conditions with aplomb. Kayaks make paddling in rough condition not only possible, but fun. I don't see many canoeists paddling in 3'-4'+ seas or 15-20+ knot winds (actually, I've never seen any), but it's a blast in a kayak. The same boat can be used for a quiet, relaxing cruise around an estuary to snap a few nature photos. Although I've seen photos of canoeists playing in surf, I've never seen anyone do it, but we do it all the time in kayaks. Of course, I'm talking about sea kayaks, rather than recreational or whitewater boats. I'm also leaving out the class of boats like the Kruger "canoes", which are canoes in name only and have more in common with kayaks. |
Fiberglass vs plastic
I found what I was looking for at www.greenval.com/winters.html. Writing about canoe design for frictional resistance John Winter says ... "A 5% decrese in wetted surface is worth bragging about, but a single year's scratches and banging can easily double coefficient of friction from 0.004 on a new fibreglass canoe to 0.008. This more than offsets the designer's efforts. The cavalier attitude of most canoeists towards their boats is evidence that a 50% resistance increase is not often noticed if only because the onset of its effect is so gradual." Earlier I wrote in this online discussion that paddling in a group would require extra effort to keep up with other members who were in similar boats with smooth hulls. I only assumed a 10% increase in frictional resistance. Winters implies a 50% increase is not unusual. I used performance data from Winters' former website. All Winters data applies to canoes (at one point he mentions a "typical" 16 foot canoe) and is provided to illustrate the principles he is writing about. Its not specific to any boat, particularly not kayaks. I was kicked off the computer at the public library after an hour, but not before taking a look at the kayak data provided by Mike Daly at http://www.greatlakeskayaker.ca/spee...anceGraphs.htm. I found the graph very interesting. I've copied down the numbers and would like to replace the resistance in pounds by the effort in horsepower when I get a free moment. Of the 5 kayaks, the Endurance 18 and the Arctic Hawk are equivalent and fastest. I don't know if they are the same length. However the Nordkapp H20 and the Solstice GT are equivalent and second fastest even though the Nordkapp is 2 ft longer than the Endurance (if I'm interpreting the names correctly). Up to a speed of 4 knots all four of these kayaks are equivalent. The two pairs only begin to diverge at speeds over 4 knots. The remaining kayak, Sonoma, is the slowest. Its length is unknown. There is an error in the data for the Sonoma at the fastest speed, revealed by a sudden change in its graph. The slowest boat is one for which John Winters suppled the data and I'm sure it is for a canoe, not a kayak, as all the Winters data I've seen is for canoes. Even though the boats I currently paddle are only cheap home made experimental plywood boats I'm careful not to treat them roughly and get the hulls scratched and gouged. That is why I was so disgusted to see the condition of the used rental boats offered at a recent sale here. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
Brian Nystrom ) writes:
While this is certainly what attracts some kayakers, I'd say the main attractions vs. canoes are the kayaks inherent seaworthiness and it's ability to handle a broad rain of weather and water conditions with aplomb. I'd have to agree that the watertightness of a kayak is its second major attraction, second only because all kayaks are faster than canoes while not all kayaks are acquired for watertightness. It would be interesting to know what proportion of kayak paddlers use spray skirts. Of course, I'm talking about sea kayaks, rather than recreational or whitewater boats. I'm also leaving out the class of boats like the Kruger "canoes", which are canoes in name only and have more in common with kayaks. I'm of the opinion that if its paddled with a double bladed paddle, kayak stlye, then it's a kayak. That includes undecked open "canoes" like the Rushton Wee Lassie and excludes decked white water and sailing canoes. It's the paddle, not the deck. One canoe club that TF Jones mentions has that as a rule in their club races. You can't enter a canoe race with a kayak paddle. If you want to use a kayak paddle you race with the kayaks. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
Speed VS Horsepower Here is the data on Mike Daly's website converted into horsepower using a conversion factor I worked out which gives hp = kt x lb x 0.003072. I also added the speed in mph using mph = kt x 1.15 for people who are not used to speed in knots. Speed kt mph Endurance Nordcapp Solstice A. Hawk Sonoma Winters 2 2.3 0.006 0.006 0.006 0.006 0.005 0.012 3 3.45 0.019 0.017 0.019 0.018 0.017 0.025 4 4.6 0.044 0.044 0.045 0.044 0.047 0.066 4.5 5.18 0.065 0.073 0.073 0.065 0.096 0.111 5 5.75 0.099 0.124 0.124 0.095 0.179 0.215 6 6.9 0.208 0.265 0.262 0.208 0.266 0.535 comments: 1. 1/20 hp = 0.05 hp which puts an average canoeist (Winters) at about 3.5 mph and a kayaker at 4.5 mph in a dead calm. 2. an athlete can sustain 1/4 hp = 0.25 hp which puts the athlete at about 6 mph in a canoe and 7 mph or more in a kayak. 3. a solo paddler can't go 7 mph in a canoe but a canoe can have 2 paddlers and that means more surface friction. 4. to go 7 mph the paddlers in the second fastest pair of kayaks have to work about 30% harder than the paddlers in the fastest pair of kayaks. 5. it's a shame we don't have the resistance broken down into friction and wave-making. That would be interesting to examine. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
wait just a darned minute, are you saying the data you presented is not
test data but is calculated from dimensions using Winter's KAPER model? that's not data. sorry, it doesn't count as data. it doesn't support your case. I've used Winters' KAEPER model on one of my own boats for fun btu it's nto measured data, just calculated numbers. I also calculate numbers with two hull design programs but they are not the same as measurements from actual in the water tests. Michael Daly" ) writes: That's my website and the data was taken from Sea Kayaker magazine (Kaper results) or from: http://www.unold.dk/paddling/articles/kayakvelocity.html which appears to be from SK's Broze/Taylor results. Kaper is John Winter's old resistance program and has a factor for plastic kayaks among other things. It's now a public domain algorithm and John told me he no longer uses it, since a commercial product (can't remember the name) is more useful for him. BTW, the following figure shows what I explained in a previous post but which you claimed was not correct. http://www.greenval.com/fig3_1.gif I've seen it. I'm familiar with it. It does not. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
The H20 after the Nordkapps name means "Hatches Two Oval" meaning that both
the front and rear hatches are oval instead of the configuration of the Nordkapp Jubalee, which had only one (the rear one) hatch oval. Pre 1992 or 93 Nordkapps had only the 7 1/2 inch round hatches Depending on the year , the Nordkapp ranges from 17 foot 8 inches to about 18 feet "William R. Watt" wrote in message ... I found what I was looking for at www.greenval.com/winters.html. Writing about canoe design for frictional resistance John Winter says ... "A 5% decrese in wetted surface is worth bragging about, but a single year's scratches and banging can easily double coefficient of friction from 0.004 on a new fibreglass canoe to 0.008. This more than offsets the designer's efforts. The cavalier attitude of most canoeists towards their boats is evidence that a 50% resistance increase is not often noticed if only because the onset of its effect is so gradual." Earlier I wrote in this online discussion that paddling in a group would require extra effort to keep up with other members who were in similar boats with smooth hulls. I only assumed a 10% increase in frictional resistance. Winters implies a 50% increase is not unusual. I used performance data from Winters' former website. All Winters data applies to canoes (at one point he mentions a "typical" 16 foot canoe) and is provided to illustrate the principles he is writing about. Its not specific to any boat, particularly not kayaks. I was kicked off the computer at the public library after an hour, but not before taking a look at the kayak data provided by Mike Daly at http://www.greatlakeskayaker.ca/spee...anceGraphs.htm. I found the graph very interesting. I've copied down the numbers and would like to replace the resistance in pounds by the effort in horsepower when I get a free moment. Of the 5 kayaks, the Endurance 18 and the Arctic Hawk are equivalent and fastest. I don't know if they are the same length. However the Nordkapp H20 and the Solstice GT are equivalent and second fastest even though the Nordkapp is 2 ft longer than the Endurance (if I'm interpreting the names correctly). Up to a speed of 4 knots all four of these kayaks are equivalent. The two pairs only begin to diverge at speeds over 4 knots. The remaining kayak, Sonoma, is the slowest. Its length is unknown. There is an error in the data for the Sonoma at the fastest speed, revealed by a sudden change in its graph. The slowest boat is one for which John Winters suppled the data and I'm sure it is for a canoe, not a kayak, as all the Winters data I've seen is for canoes. Even though the boats I currently paddle are only cheap home made experimental plywood boats I'm careful not to treat them roughly and get the hulls scratched and gouged. That is why I was so disgusted to see the condition of the used rental boats offered at a recent sale here. -- -------------------------------------------------------------------------- ---- William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
expanding on what I typed in haste yesterday ...
William R. Watt ) writes: ...I also calculate numbers with two hull design programs but they are not the same as measurements from actual in the water tests. I wrote a computer program which, like KAPER, accepts dimensions and calauclates areas, volumes, and other numbers. Unlike KAEPER this program uses analystical geometry to do its calcuations. My program is only for flat bottom skiffs. It was inspired by a clever geomertical analysis of teh dory hull by Barend Migchelsen of Dorval, Quebec who developed an simple, elegant method of designing and buidling dories based on geometry. This appreoach is pretty accurate. The program I wrote produces a tabel of offsets which is the usual way boat hulls are described for computer analysis and for boatbuiling. However, whe I input a table of offsets from my program into the two hull design program I use there is quite a variation in the areas (wetted surface) and volumes (displacement) displayed by all three programs. The bigger the boat the more they diverge. From 7% on a 12 ft skiff to 17% on a 20 footer. the discrepenciews arise from the different assumtions and formuale used by the different programs, adn by the way the two hull design programs accept teh data. they both interpolate between stations and the both produce different numbers depending on which order you type in the stations. The program I wrote is on my website under Boats and Design. It is not in the public domain but it is open source. Anybody can use it an modify it so long as they don't attempt to sell the result. So what I'm saying is design numbers are only a guide to boatbuilding. To verify the numbers you have to test the boat and collect data. I've always assumed that Winters' numbers were test data. I've also assumed his KAEPER program was verified against test data. Often a scaled down model is tested in a tank but even then there are assumptions made in the scaling and testing apparatus. I've seen them explained in wind tunnel tests for sails as well. Failures result when the design, despite teh best efforts, is not good, and there are failures in real life, some quite expensive. I'm sure some canoe and kayak designs are not very good despite the use of computers. BTW, the following figure shows what I explained in a previous post but which you claimed was not correct. http://www.greenval.com/fig3_1.gif I've seen it. I'm familiar with it. It does not. in your previous post you claimed minimal total hull resistance occurs when the frictional and wave-making resistance are equal. if you'll notice on the graph the minimal total resistance occurs when the frictional resistance is about 1.5 lb and the wave-making resistance is 4.5 lb. There is a local minimum but it's not the simple intuitive tradeoff you've claimed. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
Kayaks should be designed around people instead of designing for isolated boat performance. I don't know of any kayak designers who do this. Instead of concentrating on hull resistance, designers could concentrate on paddler horsepower requirement. A low cost, mass marketed kayak should be designed to suit a range of horsepowers, paddler weights, and paddler dimensions. A kayak produced for a more limited market can be designed to suit a smaller range of horespowers, paddler weights, and paddler dimensions. An expensive one off kayak can be custom designed to suit the power, weight, and dimensions of an individual paddler. It would cost no more to custom design a plywood kayak built with computer cut panels than to design a mass produced plywood kayak built with computer cut panels. The design ranges should be listed in the sales information for each model of kayak. Design performance graphs could be included, and for some boats actual test data plotted. Such an approach to designing would answer the buyer's perrenial question "which kayak is right for me?". The approach is particulary appropriate for kayaks because they are are primarily transporters of people using the person's own power resources for propulsion. The cost of the design is small compared to the cost of materials, labour, distribution, marketing, and sales. It would not cos much to do a more complete job of the design and provide better information for the buyer. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
William R. Watt wrote:
Kayaks should be designed around people instead of designing for isolated boat performance. I don't know of any kayak designers who do this. Instead of concentrating on hull resistance, designers could concentrate on paddler horsepower requirement. A low cost, mass marketed kayak should be designed to suit a range of horsepowers, paddler weights, and paddler dimensions. A kayak produced for a more limited market can be designed to suit a smaller range of horespowers, paddler weights, and paddler dimensions. That's exactly what the boats currently on the market do, it's just not expressed in terms of horsepower, since the average paddler wouldn't have a clue as to what that means. An expensive one off kayak can be custom designed to suit the power, weight, and dimensions of an individual paddler. OK. One can build a custom boat and there are companies that will do so. It would cost no more to custom design a plywood kayak built with computer cut panels than to design a mass produced plywood kayak built with computer cut panels. How do you figure that? The most efficient hulls (least wetted surface for a given displacement) are rounded in shape, which cannot be built from flat panels. The cost to produce a mold for a one-off design is prohibitive. One could have a boat custom designed and strip built, but how many people are going to pay in excess of $5000 for a kayak? The design ranges should be listed in the sales information for each model of kayak. Design performance graphs could be included, and for some boats actual test data plotted. To what end? This information is often available for racing boats - where the paddler actually cares about such things - but do you honestly think that the average recreational or touring paddler would have any interest in this whatsoever? I'll bet most of them don't even read the owner's manual, let alone a bunch of technical data that they don't understand. Such an approach to designing would answer the buyer's perrenial question "which kayak is right for me?". Not if they don't understand the information. Most won't and they're not going to be willing to learn about hydrodynamics in order to do so. The approach is particulary appropriate for kayaks because they are are primarily transporters of people using the person's own power resources for propulsion. The cost of the design is small compared to the cost of materials, labour, distribution, marketing, and sales. It would not cos much to do a more complete job of the design and provide better information for the buyer. Perhaps so, but whatever money it did cost would be largely wasted, since most paddlers are more interested in the color of their boat than performance graphs. I think it's safe to say that the vast majority of kayaks are purchased based on: - Impulse. One sees a cheap rec boat at one of the Marts or wholesale clubs and buys it - Recommendations of a salesman. One goes to a sporting goods store or a local kayak dealer and buys what they suggest. - Recommendations of friends. One speaks with friends who are paddlers and takes their advice. - What's available in the area. Not all boats have dealers in every area. Locally made products or those carried by local dealers will predominate, regardless of whether they're the best boats for specific paddlers. Few people will special order a boat and pay to have it shipped to them. While there are a few niche manufacturers that cater to this market, I'll wager that their combined annual output is less than 2000 boats out of a market of over 300,000. While you and I and some others here may care about performance data, it's pretty obvious that most kayak owners don't and never will. |
Fiberglass vs plastic
Brian Nystrom ) writes:
It would cost no more to custom design a plywood kayak built with computer cut panels than to design a mass produced plywood kayak built with computer cut panels. How do you figure that? companies like Chesapeke(?) Light Craft and Pygmy Boats sell plywood boats and kits make from computer cut panels. people buy the boats or they can assemble the kits themselves and save a lot of money. ... The most efficient hulls (least wetted surface for a given displacement) are rounded in shape, which cannot be built from flat panels. The cost to produce a mold for a one-off design is prohibitive. One could have a boat custom designed and strip built, but how many people are going to pay in excess of $5000 for a kayak? yes, avoiding moulds for building resin boats one off was my point. you can custom design and build a plywood or a "stripper" boat cheaper. as for the preformance of flat panel (hard chine) hulls its actually the turbulence at the chines which creates more drag at higher speeds compared to smooth chined hulls. the wetted surface vs wave-making again. some places you read about wetted surface vs wave-making. other places its wetted surface vs residual resistance, where residual resistance is any kind of drag that's not surface friction and includes drag due to wave-making, poor tracking, hard chines, etc. Such an approach to designing would answer the buyer's perrenial question "which kayak is right for me?". Not if they don't understand the information. Most won't and they're not going to be willing to learn about hydrodynamics in order to do so. all part of the education of the paddling public. I agree with everything you wrote below about the motivation to buy a kayak but when it comes to the actual purchase people do ask about which kayak is best for them, likely because they will be spending so much money on the boat and accessories. I think people can relate to how much power it should take a person of a given weight to get the boat to go a certain speed than to how many pounds of resitance the boat should have at a that speed, especially when you tell them how much power an average person can sustain paddling. I also think people could relate better to how tall they should be or how much they should weigh for a given kayak than just to say "for light people" as the brochures usually do. The data could be on a website rather than print a more costly booklet to replace the brochure. All of thse numbers should be avialable from desingers now, just restate and pass along to buyers. While you and I and some others here may care about performance data, it's pretty obvious that most kayak owners don't and never will. I've actually seen a lot of queries about "what kayak is right for me" and I suspect its because of the high cost of the boats which makes people stop and think. Kayaks and canoes cost more than bikes, skis, and skateboards. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Fiberglass vs plastic
Hi Brian
you forgot about the seat thing. After the sales talk ends, the final purchase many times is determined (for the first time buyer) by the way the seat fits. I see tons of boats bought and sold , not so much by the way they handle, as by the way the seat fits. Seems like only a small amount of people will plunk down their money, take the boat home, rip out an uncomfortable seat and replace it with something that works for them (then drill a hole for the bilge water exit fitting/ mount a foot pump or a C50 or an electric of some sort such as a waterbuster) best wishes Roy "Brian Nystrom" wrote in message ... William R. Watt wrote: Kayaks should be designed around people instead of designing for isolated boat performance. I don't know of any kayak designers who do this. Instead of concentrating on hull resistance, designers could concentrate on paddler horsepower requirement. A low cost, mass marketed kayak should be designed to suit a range of horsepowers, paddler weights, and paddler dimensions. A kayak produced for a more limited market can be designed to suit a smaller range of horespowers, paddler weights, and paddler dimensions. That's exactly what the boats currently on the market do, it's just not expressed in terms of horsepower, since the average paddler wouldn't have a clue as to what that means. An expensive one off kayak can be custom designed to suit the power, weight, and dimensions of an individual paddler. OK. One can build a custom boat and there are companies that will do so. It would cost no more to custom design a plywood kayak built with computer cut panels than to design a mass produced plywood kayak built with computer cut panels. How do you figure that? The most efficient hulls (least wetted surface for a given displacement) are rounded in shape, which cannot be built from flat panels. The cost to produce a mold for a one-off design is prohibitive. One could have a boat custom designed and strip built, but how many people are going to pay in excess of $5000 for a kayak? The design ranges should be listed in the sales information for each model of kayak. Design performance graphs could be included, and for some boats actual test data plotted. To what end? This information is often available for racing boats - where the paddler actually cares about such things - but do you honestly think that the average recreational or touring paddler would have any interest in this whatsoever? I'll bet most of them don't even read the owner's manual, let alone a bunch of technical data that they don't understand. Such an approach to designing would answer the buyer's perrenial question "which kayak is right for me?". Not if they don't understand the information. Most won't and they're not going to be willing to learn about hydrodynamics in order to do so. The approach is particulary appropriate for kayaks because they are are primarily transporters of people using the person's own power resources for propulsion. The cost of the design is small compared to the cost of materials, labour, distribution, marketing, and sales. It would not cos much to do a more complete job of the design and provide better information for the buyer. Perhaps so, but whatever money it did cost would be largely wasted, since most paddlers are more interested in the color of their boat than performance graphs. I think it's safe to say that the vast majority of kayaks are purchased based on: - Impulse. One sees a cheap rec boat at one of the Marts or wholesale clubs and buys it - Recommendations of a salesman. One goes to a sporting goods store or a local kayak dealer and buys what they suggest. - Recommendations of friends. One speaks with friends who are paddlers and takes their advice. - What's available in the area. Not all boats have dealers in every area. Locally made products or those carried by local dealers will predominate, regardless of whether they're the best boats for specific paddlers. Few people will special order a boat and pay to have it shipped to them. While there are a few niche manufacturers that cater to this market, I'll wager that their combined annual output is less than 2000 boats out of a market of over 300,000. While you and I and some others here may care about performance data, it's pretty obvious that most kayak owners don't and never will. |
Fiberglass vs plastic
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