from the NC kayak website
This quote is from the NC Kayak website FAQ. I was checking out the site as they are one of the prizes in the current contest. They claim a kevlar kayak will “gain weight drastically”
Yes, we offer a carbon/Kevlar blend at the upgrade price of $599.00. However, we don’t recommend that you choose this option. We believe carbon and Kevlar are not the best materials for kayak construction. Carbon is generally recommended because it is very stiff, and stiffness translates into speed. Yet, carbon is brittle and does not handle impacts very well. Kevlar can take impacts, but it does not have a long life-expectancy. The sun’s ultraviolet rays weaken Kevlar. Also, Kevlar does not make a molecular bond with other materials, and with its unique properties, it will begin to separate from the rest of the kayak over time. Because of this, a kayak made from Kevlar will begin to absorb water, and will gain weight drastically. A carbon/Kevlar blend does compensate slightly for their respective weaknesses, but does not solve them. Our LT fiberglass kayaks are within a pound of our carbon/Kevlar kayaks. You get more bang for your buck with a considerably longer lifespan.
I’m dubious
Drastically sounds unlikely. I’d like to see actual data.
question
do sailboats and submarines flex as much as the a kayak does when it lands on shore?
The comparisons you asked for
There is much more flexing in sailboats, submarines and airplanes than most people realize.
I’ve been on a submarine test hull after it was out for depth charge testing. I was shocked by the deformation, yet it maitained its integrity. This was awe inspiring nobody-would-have-survived waviness to a full sale test vehicle. Never mind that, compared to a kayak being run aground, a submarine experiences far greater loads while in normal operataion at depths. Sailors will tie a string tight across the inside of the hull between the frames. Then when they dive, the string will sag down to the deck. I don’t see why you could not do the same string test with your kayak.
Airplanes are just submarines in reverse. They hold pressure in rather than out, but do so with the exact same structurul design, shell with frames. On your next flight if you pay attention, you should be able to visually see a commercial jet flex significantly to dynamic loads. Look down the passenger cabin during take off and landing. You will easily see flexing and twisting well beyond what you see in your kayak. If you did not understand that all this flexing is intended, you would be freaked out. I suspect this is why most people do not notice it. Also look at the wings during flight compared to on the ground, lots of deflection.
Actually modern jets do use Kevlar or one of the better variants, Technora or Twaron. A high percentage of aramid fiber is used in the engine housings, nacelles. These are designed to contain a turbine blade that breaks free while the engine is turning at full speed. This is an excellent application for aramid fibers, like Kevlar. I’ve seen slow motion test footage of the engine housings expanding like a snake eating a rabiit as a turbine blade lets go. This is an application not different from bullet proof vests.
While subs and jets do not compare as well to kayaks, I do think sailboat hulls are a better comparison. They have similar compund curved hulls bonded to a flattish compound curved deck. The overall goal is stiffness, light weight and resiliency to repeated cycle loads. The primary cargo load is located in the middle down low and must be transferred to rest of the structure (Paddler in kayak, ballast keel in sailboat). Both use composites and adhesives as their primary construction materials. At the high performance segment, both industries are pushing for the highest stiffness, lightest weight possible, while at the recreational level there are more practical every day use considerations where more flexibility may make sense.
The Volvo 70 racing boat that recently won the Volvo Ocean race did so partly because it bucked the stiffness trend and was designed to flex a lot to absorb the incredible dynamic loads from pounding through 20 foot waves at 30 knots with a canting lead bulb keel swung out to one side some 15ft. Believe me the loads on these craft far exceed your sea kayak being run aground. And as the Volvo 70 winner proved there are many ways to solve the structural challenge, flexing to spread and reduce dynamic loads being one just like in airplanes.
Bottom line is that it would be foolish not to look at other industries for insight and ideas, especially an industry as similar as sailboats.
Sea kayaks are very simple boats, both in hydrodynamics and construction. This is why just about anybody can go into business building kayaks. Ultimately it comes down to having great marketing skills. This is the primary difference between the companies that survive and don’t.
Kevlar is a powerful marketing concept with its cool brand name (begins with the letter “K,” kayakers will eat it up) and its perception from bullet proof vest use. A certain sailboat manufacturer uses just enough Kevlar in their hulls to legally be allowed to use the word Kevlar in their marketing. Its got the marketing X factor going for it. But it is just alright as a primary material for sea kayak construction and rarely to never seen in other structures designed for similar types of loads and environments.
We can continue to live in happy land to justify all the money we have spent on Kevlar kayaks, or we can call it out and stop being suckers. I doubt the few of us who have spoken out against Kevlar here on P.Net will have much impact on the kayak marketing machine.
Carbon/kevlar
Bell Canoe has produced thousands of Carbon kevlar hulls since 1994. Their Black/Gold laminate has been pretty universally acknowledged as the best in the industry.
From the outside in, which is how composites go in a mold, it is a layer of gel for abrasion protection, a carbon blanket, carbon bottom and carbon diamond at each seat position.
A layer of kevlar, a kevlar bottom and diamond, covered by another layer of kevlar. Note Bell’s kevlar includes 25% kevlar 29 in black which yields a tweed look.
It is pricy, but the combination of carbon’s stiffness backed by Kevlar’s tensile strength yields a light hull capable of taking trememdous abuse. They do not seem to gain weight; certainly not “drastically”. My significant other’s FlashFire weighed 31 lbs last summer - which is exactly what it weighed in 1996.
Smart money replaces outer gel when cracked or gouged. Inside the hull, Swift and Blackhawk spray[ed] gel to protect the kevlar. Curtis/Hemlock paint[ed] a center gel patch.
Maybe Lotus’ Mike Galt had the best idea - a deck and porch scuff patch that could easily be updated with a pint of paint and a $2 brush from the hardware store. Wearing through a kevlar layer with ones heels is abuse - willful neglect of a watercraft in need of maintenance.
Quotes From Recent Article on Fibers
Here is a short section form an article discussing new structural fibers, Dyneema and SK78. The author starts the article with a brief history of synthetic fibers. The author’s name is Dobbs Davis and this article is in the February 2007 issue of Seahorse International Sailing magazine.
After introducing Nylon, Polyester, and polypropylene, the author writes:
“Aramid was the first high-modulus fibre, introduced as Kevlar-29 by Du Pont in the 1970s, and improved on in the 1980s with variants such as Kevlar-49. Aramid fibres are lyotropic and are produced by solvent spinning, and thus have high tensile strength, but do not melt at high temperatures. Their great strength is compromised however, by susceptibility to weakness from exposure to UV rays (in sunlight), and a rather large molecular structure makes the aramid rather dense and hydrophilic (ie water can be absorbed into the fibres)…
…There are two other principal aramid fibres: Twaron, made by Teijin, is very similar to Kevlar, and Technora, also made by Teijin, is similar though less prone to fatigue through axial compression loading and UV light exposure.”
So why are kayaks still built out of Kevlar? If there is a good application for aramid fibers in kayak construction it would seem prudent to use Technora instead. The brand name Kevlar is a powerful marketing tool. That is all.
I remember Kevlar being the hot material in sailboat racing in the 80s and then I remember Technora coming along and replacing it, Now it is Dyneema and the next up and comer is SK78. Carbon has always been the premier material, but cost prohibitive. Carbon prices have come down greatly and I expect that trend will continue. Sailboat construction is about 2 decades ahead kayaks. Saiboat hydrodyanics are about 200 years ahead of many kayaks. Why? The kayak marketing teams sell more boats more profitably by selling style than pushing for advancements in materials and hydrodyanics. Every elf-shoe shaped sea kayak built out of Kevlar is proof.
I would urge any of you interested in naval architecture, hydrodynamics, composite construction, CFD programs to check out Seahorse magazine. It would be awesome if some paddling magazine would rise to the level of Seahorse. I would not expect it though because the advertisers would frown upon real knowledge being transferred to the readers.
happy land
I don’t doubt the loads are tremendous on subs and sailboats. It was the relative amount of deformation in relation to the thickness of the hull I was thinking of. You are comparing other designs and glossing over some important distinctions.
Carbon is pricey stuff. S-glass costs a bit less than Kevlar but as you say marketing moves things. I doubt we’d see Necky or Wilderness Systems marketing an S-glass kayak. It looks the same as an e-glass one.
carbon prices have come down greatly?
since when?
Don’t sailboat racers have more money
on average than kayakers? Maybe that's why that sailboat industry can afford to use the best materials. I may be completely wrong in my supposition, my impression is that the sailing community - especially sail racers - are in a higher economic class (or have sponsers) than the average kayaker and are therefore more readily able to finance development and application of new materials and techniques.
Would using the cutting edge materials and technology used in racing sailboats in kayaks make the price of the kayaks out of reach of any but the elite racers or wealthy paddlers? Actually, the $2500 to $4000 for currently available top line kayaks already does that so, nevermind.
Great post envyabul
I’m with you on most of that. Carbon will be coming back down as new supply chains open.
You’re only saying what I said already.
Kevlar is not for stiff structures like airplane wings, boat masts, fly rods. For boats, Kevlar ONLY has application as the INNER layer of hulls that are expected to have to take big hits that produce some distortion. Builders that use Kevlar outside, or for all layers, simply do not know what they are doing.
If anyone else knows of a better fabric (Spectra didn’t work out) for the inside of boats subject to hard, distorting blows, please let the rest of us in on it.
And Salty, of COURSE Kevlar WW
boats get soft with time, for two reasons. One is that the outer layer is S-glass, and the owner neglects to fix the little compression checks that occur in the S-glass when a hard blow occurs. The other is that if a really hard blow occurs, there may be hidden delamination, and damage to the resin matrix surrounding the interior Kevlar layers as well as the exterior S-glass layers.
Now, if the inner layers had been carbon rather than Kevlar, then the carbon probably would have split under severe blows. An outright leak would be more likely, and admittedly a leak is likely to induce the boat owner to fix it, though usually not properly. And carbon is much worse than Kevlar when one is trying to see the extent of the damage to make an effective inside repair.
The worst thing about your latest point is that you are tacitly allowing the inference that the softening of S-glass/Kevlar slalom boats is due to Kevlar soaking up water, or to some other special defect of Kevlar. Put any other fiber on the inside of slalom boats, and you have boats more likely to tear inward under a blow, to sink in the middle of difficult whitewater, to pin on rocks, and be destroyed beyond repair. That Kevlar innards tempt a lot of owners to skip or skimp on repairs, resulting in “softening,” is not a fault of Kevlar as an inside boat material.
Stop talking as if I am a Kevlar “fan.” You and others are Kevlar detractors, and you have not produced evidence to the ONE rational Kevlar use under discussion: use for the inner layers of a small craft expected to have to sustain hard, very distorting hits.
Since the 70s and 80s
Carbon has slowly and steadily come down in cost quite a bit since the 70s, 80s, & 90s. The cost is not coming down as fast as many would like because the demand has increased at almost the same rate as the supply. More and more things are being made from carbon. You can even order a hood for your Subaru made out of carbon. If there were ever an ideal candidate for carbon construction it is the sea kayak.
An 18 ft seakayak in carbon should cost only about 15 - 20% more than a Kevlar boat. A QCC700 in carbon is like $3,600 - $3,700 with a Sealine rudder. For the occasional paddler, bird watcher, rock basher, carbon may not be worth the extra cost. That is who the inexpensive plastic boats are for. But I think anyone who paddles seriously 2 or 3 times/week minimum could justify the cost. Also anyone who wants/needs to put a kayak on their roof with much less effort, will find the cost of carbon cheap compared to a blown shoulder or hernia operation.
And everyone should simply stop running their composite kayaks up onto the shore, except in emegencies. That is totally unnecessary, strikes me as poor seamanship, and shows no respect for your equipment or paddling skills. If running a perfectly good kayak onto the rocks is a priority then you do not have the right mindset to own a carbon kayak.
envyabull
when you worked on ssn’s and the like what yard where you at?
Too True
You are right. The top high tech sailboats are paid for by the wealthy and sponsored. However the advancements they have subsidized can be realized for the rest of us at far more reasonable prices. Actually, many of the materials advancements are/were subsidized by government funding of defense and space programs.
Plastic or a used composite boat are inexpensive alternatives for those who want to paddle, yet can not justify the expense of a composite boat.
Since this discussion is about the pros and cons of Kevlar, I think we need to look at the cost of Kevlar kayaks as the cost baseline. I think many who can afford a Kevlar boat could also spend a little more for carbon if they understood its beneifts. Problem is that the local shops do not have much carbon to offer and Kevlar is pitched as the best lightweight material for sea kayaks. I do not think it is.
General Dynamics Elecric Boat
Groton, CT. I still own a rental property a stones throw away from that yard. I am currently sitting directly across the Thames River from the Groton Sub Base.
Subs may be the most complex machines on the planet today. Despite their internal complexity, they are relatively simple hydrodynamically. Surface craft including sea kayaks have more complex hydrodynamic issues to contend with.
you might have known
my grandfather, dick moll, retired in 85 from eb, lives in old lyme now
That’s right. Only rock bashers.
Careful sea kayakers may be better off without interior Kevlar. Same for lake canoeists and paddlers of clear, smooth rivers.
I’m a rock basher. That’s why I like Kevlar on the inside, or maybe CAP if the resin is vinylester.
I suspect that builders like Wenonah, who use Kevlar in their lighter boats, believe that some boaters are rock-bashers without knowing it. However, I would grant that substituting some carbon and some CAP with the appropriate resin might achieve the same result, except in serious whitewater.
Before my time
I was there from like '89 - '96.
Old Lyme is a beautiful town. Housing prices there have skyrocketed. Sceneic paddling around Great Island and up the Lieutenenat & CT Rivers
Internet communication
We are not so far apart…I have owned Kevlar boats and they were OK. I like Gala stuff. It’s a material that has good attributes, and is applicable where weight is paramount. If used wisely and laminated well, it’s fine.
My experience, and that of my friends has been that the carbon, glass boats have stayed stiffer and been plenty durable. I think there’s a disconnect here in communication for which I’ll take some responsibility. As I’ve said many times the material has it’s place, but I prefer s-glass and Carbon. I would not shy away from a boat I liked if it had Kevalr in it. I would not spec the material in my boat of choice, if I had a choice. Companies like Epic, and others do nice applications with Kevlar. Speaking with my friend the other day about this discussion, his response was that he too used to buy into a lot of the Kevlar marketing, but his strong preference anymore is with Carbon glass which he believes has been miss-represented as brittle and touchy…not his, or my experience. It’s OK to have different opinions. Good day