Graphite vs Kevlar UltraLight
Posted by: duckhunter on Jan-30-13 4:59 PM (EST) Category: Canoes
I have a Wenonah Prism in Kevlar flex core layup which serves my canoeing needs very well. Unfortunately this 44 pound canoe is harder for me to lift than it was when I purchased it 9 years ago. The graphite Prism weights 32 lbs. and the ultra light layup weighs 34 lbs. Any thoughts on the advantages or disadvantages of these two layups?
The initial cost is not a major factor.
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- Graphite vs Kevlar UltraLight - duckhunter - Jan-30-13 4:59 PM
If it was me I would get the ultralight|
Posted by: Jackl on Jan-30-13 6:55 PM (EST)
layout. The graphite will be a lot more delicate.
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Whether it is more delicate depends on |
Posted by: g2d on Feb-01-13 2:46 PM (EST)
what Wenonah does with the carbon. With proper use of carbon cloth, the canoe should be stiffer and stronger than their ultralite, at the same or less weight.
The one way that carbon is vulnerable, in replacing other "outside" cloth layers, is that it wears through faster than other cloths. On that note, Wenonah has been resolutely irrational in using Kevlar as an outside layer. I don't know if they've ever corrected that practice.
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We have three J boats, and three tandems|
Posted by: Jackl on Feb-01-13 4:37 PM (EST)
Wenonahs and Dillers.
Some of are ultralight Kevlar and some are carbon, and as far as I am concerned the carbon is more delicate.
I can only assume that the solos are similar.
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It must depend on what layup Wenonah|
Posted by: g2d on Feb-02-13 12:33 AM (EST)
uses. I will state categorically that if they keep the same reinforcement inside the hull, using Kevlar, and only replace some outside Kevlar with layers of carbon of equivalent weight, you will get a stiffer canoe that is harder to break and easier to repair. That has always been the experience of whitewater boat builders.
Now, certain kinds of blows to the outside of a CC/KK hull may cause local compression cracks, just as they do on my SS/KK whitewater boats. But such cracks are easily and quickly repaired. I hate to repair local damage to the outside of an all Kevlar hull. The Kevlar often scrunches and delaminates rather than breaking, so it has to be laboriously cut out. Sanding is more difficult. Then one has to decide what repair cloth to use.
Kevlar is an outstanding cloth for the inside of hulls, but always a disappointment for the outside layers. Back in the 80s, the Boatbuilders Manual presented clear data showing that an SS/KK layup was the best at withstanding damage. KKKK was far behind. I've never seen test data that contradicted that result.
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And I will state "Categorically"|
Posted by: Jackl on Feb-02-13 9:46 AM (EST)
that of the boats I have: the carbon are more delicate !
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So, they could have done the "carbon" |
Posted by: g2d on Feb-02-13 11:58 AM (EST)
boats correctly, but they didn't.
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Posted by: CEWilson on Feb-02-13 1:44 PM (EST)
I think WeNoNah intends their carbon boats for marathon competition, which uses sprint kayak/Canoeing, Italian based construction guidelines;"If you aren't in first place, why finish?" Those boats use minimal fabris to contain weight.
Hulls for recreational use tend to have more fabric in the laminate, the Germanic construction concept "Can't win if you don't finish."
Savage River offers another inner blanket for those intending a long life for their canoes.
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Yeah, the first guy to run the marathon |
Posted by: g2d on Feb-02-13 5:27 PM (EST)
died at the finish.
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And he was slightly...|
Posted by: canoeswithduckheads on Feb-04-13 9:20 AM (EST)
...closer to Italian than Germanic.
But he was mostly carbon.
As soon as my personal economy allows it (as well as the Misses), I intend to replace my Wenonah Flexcore Rendezvous with a Savage River Blackwater in their carbon/Kevlar layup. Light, lithe, but sturdy being my hoped-for goal. Here's hoping it never has to face one-twentieth of the schisty abuse my 1991 S-glass Mad River Explorer's been subjected to. (Must be the German in me?) Now there's a composite riparian warrior! (Maybe it's the Irish in Jim Henry?)
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Posted by: CEWilson on Feb-05-13 4:54 PM (EST)
Sorry, I'm having a bad day concerning belief verse data based systems.
Common Kevlar, taffeta or crows foot weave, weighs 5oz per square yard. Carbon commonly available weighs between 5.7 and 6.3 oz per sq. yd.
Infused, we would assume ~45% resin content and more for the wet bagging system WeNoNah uses, so lets double fabric weight to arrive at approximate and comparable weights for the Minnesota firm's laminations. Carbon is 5.7X2= 11.4oz/sq yd, Kevlar is 5X2= 10oz/sq yard. A Prism blanket layer will have about 5 sq yards of fabric, so the Kevlar outer skin weighs ~4lbs, the Carbon outer 4lbs 12oz. Yet the carbon boat is lighter. How can that be?
That is because while Kevlar is has great tensile strength it has poor compression resistance. It takes more Kevlar layers to build aqequate thichness to stiffen a hull. Carbon has marginal tensile strength but great compressive strength. Combining the two positive characteristics allows fewer and/or smaller partial inner pieces or layers to construct the boat. So, the half carbon boat weighs less because adequate stiffness is achieved by combining fabrics.
We can design a lamination schedule to any weight or strength we desire, but we cannot max strength and minimize weight at the same time. It is useful to remember that laminate thickness increases stiffness, just like increasing web on an I beam. Cores do this; the lightest being honeycomb, with foams, balsa and various poly mats following in ascending-weight order.
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Posted by: BPD on Feb-05-13 9:14 PM (EST)
-- Last Updated: Feb-05-13 9:35 PM EST --
Without a doubt.
My comments about the difference between the two layups were based on what the Wenonah boys told me back in the day. I talked to those guys a fair bit back when I worked at Rutabaga, and had a friend who built boats for them and worked in the repair shop. That's how they described the layup to me at the time. But they may have glossed over some technical aspects of the construction when they were explaining it to me. Which would explain my confusion on particulars.
Maybe they leave out two layers of Kevlar cloth and replace it with a single layer of carbon. Certainly plausible. I haven't seen the cutting schedule, so I don't know.
One way or the other, as you said, they are putting less material in the boat--either by using a lighter weight carbon cloth or by replacing multiple layers of Kevlar and selective reinforcement with a single outer carbon skin.
So the carbon boats are less durable, as you suggested and Jack observed.
My point, which maybe I didn't make very eloquently, is that it is pretty hard for people to tell the difference between these two particular layups on the the water because the stiffness in the Wenonah ultralight hulls comes primarily from the PVC core.
Given the thickness of the core, and the minimal amount of cloth used in the boats, the materials used outside the core don't have as much impact on the overall stiffness or paddling "feel" of the boat as they might otherwise.
Its hard to perceive much difference between the two hulls on the water. I certainly haven't when I have paddled them. So the decision of which to buy has to come down to other factors, like weight, cosmetics, cost and durability.
Which is why I was thinking it makes sense to go for the Kevlar. Unless you really want the graphite look. Or you really want to save those two pounds.
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Posted by: CEWilson on Feb-06-13 11:22 AM (EST)
-- Last Updated: Feb-06-13 6:37 PM EST --
Don't think I claimed the Carbon/Kevlar hull is less durable; you're putting your beliefs on my keyboard, and old, anecdotal, beliefs at that!
The combi, dual material layup may be more durable than the all Kevlar layup, maybe not, but it no doubt performs better in the context it was designed for; citizen racing.
Certainly Wenonah is not replacing two Kevlar layers with one carbon. Yes, Wenonah could special order atypical fabric weights, but chances are they do not. We'd need the lamination schedules, which are probably closely guarded, to guess at differential durability and fairly exhaustive testing to determine if any guess, even one based on real information, was correct.
OP should get what he likes, I do not consider either laminate a particularly rugged tripping choice.
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Posted by: BPD on Feb-06-13 3:29 PM (EST)
Apologies, I think I misunderstood your earlier post. Certainly not trying to put words into your keyboard.
Let me see if I follow correctly.
As I understand it you are saying that we can't really tell if the carbon or Kevlar version of the ultralight Wenonah layup in the Prism is more or less durable unless we know exactly what goes in it.
And we shouldn't assume that one is more or less durable than the other because one has carbon and the other has more Kevlar.
Have I got it straight?
Considering the potential difficulties of finding out the exact laminating schedule for the boat, do you think there is a reasonable way for a person to choose between these two layups if he is set on buying a Prism?
What would be your advice to Duckhunter in response to his initial question?
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Anectodal UL experience|
Posted by: kayamedic on Feb-06-13 7:30 PM (EST)
I do a lot of Canadian Shield tripping and one of the facets of UL boats is the foam core added for stiffness.
I managed to wreck a UL boat as it folded around a rock in Temagami. There was some foam core damage..rather difficult to fix.
My understanding is that foam is added to stiffen the bottom. Since that miserable experience in which I owed my life to a roll of duct tape to get the 100 km to nearest town, I have gone with CF/Kevlar boats without a foam core. The CF adds enough stiffness to make the core unnecessary.
Just wrapped up another two weeks of paddling with such a boat in Florida which has surprise surprise, limestone laden rapids and oyster bars... each of which will literally slice a skin covered boat.
I am pretty hard on boats. Never again any UL all kev layup for me.
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Posted by: beaverjack on Jan-30-13 7:06 PM (EST)
I haven't had the Graphite, but for the money, the UL is dandy. I've taken a UL boat all over the BWCA, and it's plenty tough and light enough.
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which other brands other then swift ?|
Posted by: lennart on Jan-31-13 12:50 AM (EST)
If you like the prism, the solo boats of swift are different is their paddling.
the shadow of placid. can be the look of it get close. not sure never seen one over here. Not sure how fast they can start producing that model after the fire. hopefully soon.
any others that do a fast tripper sub 30 pouds?
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thanks for the info|
Posted by: lennart on Jan-31-13 12:08 PM (EST)
To bad that only placid and swift make it sometimes to Europe. So I did not know the other brands.
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Posted by: jhb8426 on Jan-31-13 12:48 AM (EST)
How these boats get heavier over time. :)
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Posted by: duckhunter on Jan-31-13 8:26 AM (EST)
Are synthetic rails on lightweight solo canoes as durable as aluminum rails? I know one person who had synthetic rails crack shortly after they bought their canoe. The manufacturer replaced the rails but they went most of one summer without their canoe while this was being done.
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Posted by: magooch on Feb-02-13 10:10 AM (EST)
Have you weighed your canoe lately. It just might be that the kevlar has been exposed to and wicked water into the fabric.
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g2d must be busy this weekend.|
Posted by: guideboatguy on Feb-03-13 12:20 AM (EST)
According to him, the idea that exposed Kevlar absorbs water is a myth, and I believe him. The idea is, in a properly made boat the fabric is fully saturated with resin, and thus, there is no unoccupied volume within it. In fact, other stuff I've heard would suggest that in a poorly made boat, there is far too much resin, so that not only is the fabric saturated, but there is excess material serving no purpose. It doesn't make sense to me that there'd be an opposite extreme, where the weave of the fabric has available space within it. The whole idea is to squish resin into the weave during construction, right?
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Composites and Water Absorbtion|
Posted by: BPD on Feb-05-13 10:05 AM (EST)
On water absorption:
Composite boats do absorb water, but it is the resin, not the cloth that does the absorbing. This is a particular problem with polyester resin in thicker laminates--much less of a problem with the vinyl-ester resin that Wenonah uses in it's ultralight Kevlar boats.
In the sailboat industry people are aware of the problem of osmosis blisters in fiberglass hulls. These are formed when water is absorbed into the fiberglass laminate and undergoes a chemical reaction with polyester resin.
Here is a link to osmosis blister information: http://www.nauticalweb.com/info/maint/osmosi_e.htm
This is not a problem with any canoe, since the boats are stored out of the water and have a chance to dry between use. But composite canoes and kayaks can theoretically absorb water.
Usually it is composite kayaks that will show a slight increase in weight with a little bit of water absorption. The enclosed hull of the kayak allows water to be trapped and absorbed in a high-humidity environment. And almost all kayaks are made with polyester resin. Storing kayaks with hatches removed allows air to circulate inside the boats and keeps water absorption to a minimum.
But--the effect is pretty minimal overall one way or the other. Certainly not something that people have to worry about.
For all practical purposes it's probably safe to say that Kevlar boats don't absorb water and gain weight over time.
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Posted by: CEWilson on Feb-05-13 11:59 AM (EST)
Osmosis is a documented fact as opposed to a belief; air inclusions in Poly Ester resin allowing water in by osmosis over time.
That said, most builders now use VE resin, minimizing water transfer. Better builders also infuse, which completely eliminates air voids or wet bag which, when everything goes right, should also eliminate voids.
Lastly, Kevlar/Twaron is minimally hydrophylic, and, even when skin coated, as per the exterior on some, mostly race, boats and on the interior of just about every bagged canoe, is completely resin filled.
We've all seen skin coated boats in their second decade with resin flexed out of the fiber. Time for a new boat. Designs and construction have probably improved anyway!
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BPD, I think you'll find that there are |
Posted by: g2d on Feb-07-13 12:00 AM (EST)
no longer any makers of quality canoes or kayaks who are still using plain ol' polyester. I think vinylester is getting to be near universal. There are just a few builders using epoxy, which is even more resistant to hydrolysis, but more expensive and apparently not amenable to the new infusion process.
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Think about how many high end canoe |
Posted by: g2d on Feb-04-13 2:41 PM (EST)
makers use Kevlar as the inside layer, where after vacuum bagging or infusion, the sides of many Kevlar fibers are right there at the surface of the layup. If Kevlar in a resin matrix actually absorbed water, don't you imagine those manufacturers would paint the insides of their boats?
Maybe they know something about what Kevlar does, and doesn't, do.
I guess a policeman or soldier caught wearing Kevlar armor in a tropical rainstorm would be really screwed, no?
What about the sailing industry? Kevlar sails? Rain-soaked, would they turn a sailboat over?
Aren't suburban myths wonderful One or two in every garage.
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Posted by: rblturtle on Feb-07-13 7:47 AM (EST)
When I had my Savage River-carbon/kevlar with an extra layer of kevlar with intrigal gunnels, It once fell off the top of my pack frame onto solid rock bounced and fell another 10' onto another round rock-no damage. I also once collided with a rock head on in fact current-a little chip.Also ran a lot of beaver dams loaded. I was very pleasantly surprised both times!
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