ya I’ve always loved the area
Done a bit of paddling round the area. I’m actually buidling a foam core racing kayak of my own design at school right now that I was thinking of doing the outside of the hull in kev and the rest of the boat in s-glass, peel ply it as I can’t afford vacummed bagging gear.
accident
Sorry to report that the vessel Eathrace ran into a fishing vessel off of Guatemals in the Pacific.
This boat was going to try and break the speed record for a round the world record.
Just a side note the boat was built of kevlar with a carbon layer.
This vessel was designed to do 56 mph in all ocean conditions, you can’t even begin to imagine the stress on this boat.
Who says kevlar is not being used in racing boats any more.
Dennis
An additional note on boats that bend
without breaking. Esquif has a new open WW boat, the Zephyr, made by combining a “poly” resin (I’m not clear if it is polyethelene or polypropelene) and polypropelene cloth. That particular cloth has zero water absorption. This 11+ foot boat weighs a little over 30 pounds. Zephyrs are >extremely< hard to break, but one of the first owners got right on the project and hammered one mercilessly on creeks in the Pacific NW. He reported that one of the ends started to get rather soft. This shows that “softening” can be the sole result of hammering a composite that refuses to tear, even when we know that water has not played a role at all.
This, however, must be admitted. Since all composite fabrics in use, except for glass, carbon, and polypropelene, are known to absorb water, to varying degrees, if YOU the boat owner allow your boat to be cracked and battered, the fibers will lose some of the protection of the resin, and water will get into the fibers. What happens then is still the subject of controversy. CE Wilson pointed out that even when water gets into glass fibers, particularly woven roving, freezing temperatures can cause further damage.
0% weight gain
0% weight gain doesn’t sound too drastic.
Showed this thread to a tech rep
– Last Updated: Mar-20-07 5:23 AM EST –
from a major composite supplier today. He distributes material and resin to Aerospace, yachting, and kayak industry, including carbon and Kevlar. He read through most of it and agreed with the notion that Kevlar is NOT the best material for kayak or boat construction in general. Not terrible, just not ideal. He said it IS susceptable to interlaminar breakdown more so than other materials, and DOES indeed absorb water. To envyabulls posts, he agrees that the kayak industry is a bit behind, and rather "touchy". He'll sell them Kevlar cuz that's what they say sells kayaks. It's NOT what he would use.
That only means that he doesn’t build
canoes and kayaks. Kevlar has no marked difference from any other organic chain fiber with regard to water or delamination. The only way to top it is to use CAP with vinylester. Actual observation, as with my Millbrook boat (now about ten years old and hammered by the previous owner) is that Kevlar is not soaking up water in normal use, and is not delaminating. Not at all. You’re welcome to get a plane ticket. We’ll take it out in the yard and you can look for yourself. You can check my 20 year old Noah while you’re at it.
You keep trucking in opinions from outsiders to support doubts about Kevlar. Or you note that older WW boats with Kevlar have “softened,” when of course this is actually due to hard use without proper repair, not Kevlar. Some builders may use it inappropriately, out of ignorance, but some builders have used it where performance, not market appeal, counts, and they have made it work in ways that pure glass and carbon can’t suffice.
I do think that CAP and S-glass can match Kevlar for taking a beating, but only if one accepts a modest weight penalty. Kevlar is sometimes eschewed in top slalom boats, not because it is weak or soaky, but because (as with my Dagger C-1) the boat owner had to have the last measure of stiffness and had quick access to replacement boats. I have to be extra careful of that Dagger, because (as the owner-designer told me), it will break catastrophically if it takes a really big hit. The S-glass over Carbon just is not willing to bend far at all. I cannot see why someone would want a layup like that for general river handling.
Dude, come out of the defensive crouch
This is an interesting discussion and exchange of ideas. No one is putting you, or your boats, or your opinions down. Rather, sharing their own findings over the years and contrasting their experiences with experts in the composite industry. I’m a paddler. I know many in the industry, as do you. I live near, drink coffee and beer with Aerospace composite engineers, one of which built a world record holding sailboat, and worked on the Space Shuttle. Others have tons of experience with Mega yachts all the way to kayaks. These guys have had full careers in composite engineering. I gave you the number to one of them already! They have processed tons of aramid fiber, carbon, and crap I can’t pronounce. Infused, Pre-preg, blah blah. When expert after expert tell you the same thing, and it correlates with your experience, you start to modify your thinking. As I have said, and they have said, Kevlar CAN make a good kayak, and may have some application for short term impact resistance, it would not be their choice. No one is arguing that the material has produced some good kayaks!! Interestingly my friend who was an Olymic paddler and Coach agrees totally with them. Our thinking has changed. Recent surf kayaks of Carbon and glass have withstood far more abuse than previous kevlar carbon versions. They stay stiffer far longer.
So, I recognise that I’m saying things that disturb you because you disagree with them. Disagreement is OK, and I certainly don’t feel I’ve shown disrespect to you. We just see things differently. Good day.
I disagree with them because you are
wrong. If you want to know about problems with Kevlar in composite canoes and kayaks, you talk to builders of canoes and kayaks, not builders of airplanes and yachts. I have conceded every point to you for which I have evidence. Otherwise, it is up to you to go to the TRUE sources if you want to argue that there is a problem with Kevlar, whether “soaking” or delamination.
Read again
All expets listed above have BUILT KAYAKS AND CONSULTED TO THE KAKAK INDUSTRY! Space Shuttle guy consulted to the kayak industry regarding resin infusion. Yacht guy is building custom infused race boats and surf ski’s on the side. Hint…Oracles latest race yacht was built in my backyard with these resources.
I’m wondering why you are so black and white. Right wrong, good bad. etc. Pretty simplistic.
This is a discussion about material properties and best application of said materials with pro’s and con’s.
Relax guy…do what you believe is right and be happy. No one cares. Good night
black and white
when a thread starts with a black and white statement that kevlar soaks up too much weight and another blurb “from someone in the industry” says a kevlar kayak will drastically gain weight there’s something not quite right.
You’ve not heard me say either
I’m bored with this.
That’s what you haven’t established.
There is no indication from experience in kayaks and canoes that Kevlar sticks less well to resin or is more inclined to interlaminar shearing.
One must be careful about interpreting a smashed bow. An S-glass/carbon bow will break at a certain point, without a lot of apparent delamination.
An S-glass/Kevlar bow may yield at a similar level of force, but may or may not break completely. If it does not break, the reluctance of Kevlar (or any other fiber used for inner layers to reduce the risk of complete breaking through… Nylon, Polyester/CAP, polypropelene) to tear may result in the Kevlar being pulled away from the S-glass and from itself. Thus an informal assessment of damage to a boat which is all Kevlar or has Kevlar for the inner layers may result in an impression that Kevlar is “prone” to delaminating.
I don’t know where you get the basis for your repeated insinuations that Kevlar in epoxy (or even Kevlar in vinylester) manages to absorb significant amounts of water. This is likely to occur only if the laminate has been smashed up almost like a buffalo pelt being chewed for softness. Kevlar by itself absorbs about half as much as Nylon, a little under 5% by weight. Long experience with both fibers in canoe and kayak construction has not shown big water weight gains.
You may want to rely more on S-glass, with only as much carbon as needed to cut weight while maintaining stiffness. One “yacht” source, Allison, claims that primarily carbon boats are inclined to catastrophic failure, and advocates S-glass for its superior ability to flex without failing.
what a bunch of hooey
This is worse than the REI…err, outlet store thread (darn, I was sufficiently embarrassed already).
If you don’t think kevlar is a good material to build kayaks out of then start a thread.
If you want to speculate about water absorption or divining rods or whether hot water freezes faster than cold we always know we can come to this forum.
Dynel can be confused with Diolen.
Diolen is a European term for polyester fabric, sometimes called “CAP” or chemically activated polyester for the tenacious bond it makes with vinylester resin.
Your fabric, Dynel, is a Union Carbide product. You can expect it to bond normally to laminates, though Walbridge reported that it tended to absorb a lot of resin. It DOES resist frictional wear, and wears smooth, but it is NOT strong, so it may be more susceptible to cracking than other cloths you could apply to a boat for wear areas, such as S-glass, which wears smooth and has good strength. I have put Dynel sleeves on some paddle shafts, and they do wear well, without the risk of fuzzing or glass fiber irritation one might expect with alternatives.
If you had read my posts, you would
know that I am not “black and white” about Kevlar, but have frequently criticized its applications on this board. My points remain as follows.
- No one has to accept uncritically the views of yacht or aerospace designers who do not make large numbers of kayaks and canoes for a living over long periods of time.
- There is no evidence that boats with Kevlar in them are slowly degenerating from water absorption (though I suspect they may be from lack of proper repair).
- There is no evidence that boats made with Kevlar are more more inclined to delaminate than boats made with other hydrocarbon fibers, except where it is due to the greater reluctance of Kevlar to tear rather than break.
- Using Kevlar for the inner layers of canoes and kayaks (with S-glass for the outer layers) is as good a way as any to get a composite boat that is tolerably stiff, resists breakage under hard use, and gets back off the water still in repairable condition.
You have said that I am “defensive,” but I think it is really my >offensive< refusal to put up with your “damning with faint praise” of Kevlar, and your insinuations about water-logging and delamination which bothers you. These do not appear to be supported by actual experience in the world of canoeing and kayaking.
comparing kayaks with submarines
and cored racing sail boats is what gets me.
I had a kevlar Necky Swallow that could flex 3" (1.5"in/out) without gel coat cracks. A Mariner Express made of roven woving that could flex with no problems. A QCC400 with a flexible mis section.
I don’t think a carbon/core racing sailboat or titanium/aluminum sailboat are flexing 20-30times hull thickness.
Sure it’s possible to put in core material to make a hull absolutely rigid but there’s going to be a corresponding increase in weight for it to have impact strength or an increase in cost to make it out of material that can sustain point loading.
That said I was surprised to look at a recent Epic kayak. The interior glass on the cored deck appeared to be one layer of fine 4oz glass. It looks sufficient.
so if it was such a great idea
then why did they drop it? Or were you talking about aircraft?
Maybe you could teach them a thing or three about poly construction, they sure could use it.
seakak, don’t you know about the
secret prize for the person who pushes a thread above 100? I missed it this time, but I’m still trying!
The prize is 100 pounds each of Kevlar and carbon cloth remnants.
excellent!
…but is that weighed before all the water absorption, or after?