Mouse Pads
I’ve heard of people gluing down those rubber, possibly neoprene, computer mouse pads as heel pads inside their kayaks.
Impact Strength Only
Adding a couple layers of Kevlar will improve the impact strength of a kayak, but it is not as stiff as an all-glass boat.
Probably the best compromise for non-cored construction is glass outer layer for abrasion resistance and water sealing, Kevlar in the middle for impact resistance and Carbon on the inside for lightweight stiffness.
Some could argue that Kevlar is slightly better than carbon structurally as the inside layer, but becase of its poor abrasion resistance and the fact that it will wick water once the fabric is exposed, I would prefer carbon as the inside later. Plus carbon is a lot sexier to look at than Kevlar.
But Kevlar WON’T wick water when
exposed inside. Nor will Nylon, CAP, or other hydrocarbon based fibers. I thought you were clear on that.
Incidentally, Millbrook makes VERY
stiff and light boats using S-glass outside, Kevlar inside. I own one. It is almost as stiff as my slalom c-1, made with S-glass outside and carbon inside.
I have not broken the c-1 hull in ten years of desultory paddling, but I would not order a boat like that. Kevlar inside has a long, proven record in whitewater use.
Interesting test results
Last year a company in Anacortes Wa. with years of composite experience experimented with an infused lay-up of Kevlar, Glass, and a Carbon / Polyester co-weave. Test panels were subjected to all sorts of abuse. The glass AND Kevlar tore quite easily, but the Carbon / Polyester co-weave never did! That was one tough layer, and those results stuck in my head. I have torn noses completely off Kevlar kayaks and punched chunks right through them, split them etc., so I have never experienced the phenomenon of the fabric holding together while everything else chips away. I subsequently do not buy that sales pitch, and these results confirmed that. I’m mass impressed with that polyester carbon.
I still believe that Kevlar can be a great material for lightweight lay-ups if layed-up properly. For impact I’d WAY take that Carbon Polyester co-weave over it anyday. Couldn’t tear that stuff!!
I would not believe that the Kevlar
layup tore “easily,” but if they used vinylester rather than epoxy as the resin, that would explain their results with polyester fiber. CAP or Chemically Activated Polyester has long been known to form an unusually tenacious bond with polyester or (superior) vinylester resin. Epoxy does not have any special bonding advantage to polyester cloth.
So, if they used vinylester, I can believe SOME of their results. But, just TRY to tear a Kevlar layup.
I’ll email you privately the contact.
what weight/weave?
are the carbon and poly threads together or interlaced?
thanks - I’ve got some
on hand - it’s System 3, which I really like working with, by the way. I also have some Dynel on hand - it’s supposed to be really wear resistant. Do you think it will adhere as well as regular glass?
cor material often outgass
or lose flexability.
Exposed Nylon and Kevlar do absorb water
As long as the Kevlar is sealed in resin it will not abosrb water. Once your heels wear through the resin and expose the fibers it will absorb water.
I just read an article in SeaHorse magazine about the latest high tech fibers, Dyneema & SK88, used in the sailboat racing industry. It starts with a brief history of high tech fibers including Kevlar. It states that one of Kevlar’s weaknesses is absorption of water. It also speaks of Kevlars weakness to some types of loads.
There is hardly any Kevlar used on today’s racing sailboats. We used to see a lot used in sails about 20 years ago, but other fibers have replaced Kevlar quite a while ago. Its just not that great for boat construction, except in targeted areas for impact resistance.
Nylon absorbs water even more than Kevlar. It also swells when it absorbs water. Nylon bearings are a very bad idea if there is a chance they will be exposed to moisture. Delrin is better material for wet bearings.
so that kayak made out of nylon
and no resin was a bad idea.
Facts from industries other than
kayak manufacturing will only confuse the followers. Please do not introduce such nonsense into this cult…OK
But Kevlar, Nylon, will not wick when
laid up in resin and “exposed” inside. Nor will Nylon, CAP, or other hydrocarbon based fibers. I thought you were clear on that.
Chris Craft and sailboat builders do NOT deal with composite layups that must withstand high distortion and pounding the way whitewater boats do. Composites kayak and canoe builders, at least a couple of whom post REGULARLY on this board, KNOW what they are doing, and would never risk the ire of customers if Kevlar really wicked water after being properly laid up in epoxy or vinylester. And I have never seen ANYONE on this board say, “MY composite Kevlar boat has gained 10% in weight after being knocked around a little in water.” Not even 5%, or 2%. All this bull just gets Kevlar boat owners without adequate knowledge to feel neurotic and start weighing their boats monthly on bathroom scales.
So I say, it is time to cease being interested in mysterious waterpockets in jet plane wings, or in what yacht builders use as a justification when customers ask about Kevlar. Actually, I think Kevlar is a rotten cloth to use either in jet planes or big, stiff yachts. But it is great for personal watercraft that take a pounding.
It really is kind of contemptible how little respect is being shown for canoe and kayak builders in this matter. For example, I have a Bluewater Chippewa tandem, 48 pounds, made with Kevlar, Nylon, and glass. It was built by Gary Barton, who has been making Kevlar, S-glass, and carbon kayaks and c-1s for our Olympic representatives for decades. And some people on this board want to contend that Barton, and a dozen other whitewater boat builders, are somehow so ignorant that they use fabrics that will wick water in use. Get real.
Not saying that
I know you love Kevlar…that’s all good. A smart builder/engineer chooses materials that best suit the requirements. There IS a reason you don’t see Kevlar in paddles much or sailboat masts, bike frames, fly rods etc. I am very close friends with ex-Olympic paddlers and they tell tales of Kevlar boats getting soft over time. So, is it bad material…NO…it’s a lightweight material that is super weak in compression and is susceptible to interlaminar shearing amd matrix breakdown. If done well is that a factor…maybe not. Kayaks do not experience the stress of planing hulled powerboats, aircraft, etc., and they are NOT in the water that much actually.
envy’s first post…
– Last Updated: Mar-18-07 12:58 AM EST –
...nails it. Kevlar is a poor idea in kayak construction. Don't care what the marketeering folks say. In aircraft, we use carbon fiber. For a reason. As an engineer, only Necky appears to have known what they were doing with their carbon layups (no longer being made, BTW).
I think
Necky went all glass due to Carbon’s huge cost upswing, secondary to Aerospace demand vs supply. Last I spoke to the folks there, they were discussing bringing it back, albeit at a higher cost option.
Agreed.
Spoke with Necky last week, and when asked, they didn’t indicate any plans to bring back the carbon boats. Wish they would.
Comparisons to Related Industries
I think it is very relevant to compare construction methods and materials across industries. Loads are loads. While the degrees of loads may vary, the appropriateness of various materials to withstand various types of loads is absolutely translatable across applications.
Certainly sailboat construction has many similarities to kayak construction. Sailboat hulls and sea kayak hulls share many of the same dynamic loads.
Actually cutting edge sailboat construction has recently surpassed the aerospace industry in some of the more refined construction techniques.
Besides kayaks, I have designed nuclear submarines in steel and commercial aircraft in aluminum. Then I went onto buried plastic structures, which was far more more copmplex and interesting than the other stuff. Yet there were many principles and concepts that could be transferred between the different disciplines.
I will continue to make comparisons across industries when I think it contributes something to the discussion. I know some of it may be over the head of some and many just won’t give a damn. But you have no right to tell me to stop or to speak for the others who just might be interested.
If you don’t like what you read here, you can read the advertisments in you favorite paddling magazine for engineering and design information.
Thank You.
If Carbon & Kevlar Cost the Same…
If Carbon and Kevlar kayaks cost the same, only the rock bashers would ever want any Kevlar in their kayak.
A carbon sea kayak costs 15 - 20% more than a Kevlar sea kayak. The weight, stiffness and longevity advantages of carbon makes the choice a no-brainer.
Unfortunately I was a sucker for the Kevlar maketing about 6 years ago. I still have that Kevlar kayak and it has served me well, but it has gone soft and whippy over time. The Kevlar has completely worn through in the heels area. There are stress cracks in the gel coat in a number of places from the Kevlar flexing beyond the yield strength of the gel coat.
I learned my lesson and only hope to pass on my experience with others. I still love that ol’ Kevlar dog, but in the future it will only be carbon or carbon/glass hybrids for me. Your priorities may be different than mine, but for me the benefits of carbon more than exceed the added cost.