Dilema - Diolen or Kevlar Layup^

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GordB
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Dilema - Diolen or Kevlar Layup^

Post by GordB » Wed Mar 21, 2007 8:33 am

Hello All.

I'm having a difficult time deciding which of the two layups to order.

I am considering very seriously a Valley Nordkapp, but I am unable to compare the differences in layup side by side. There is only one in town and it's of a Diolen construction.

Are there any benefits/drawbacks to kevlar other than weight?

Will there be a durability penalty to pay for the weight savings in ordering a Kevlar boat?

Thank you

Gord

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Jim
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Post by Jim » Wed Mar 21, 2007 1:04 pm

As far as I know Diolen does not have quite the same tensile strength as Aramid (Kevlar), but is in the same league and considerably cheaper. The result is that a builder can use a bit less kevlar for the same strength or the same amount for a bit more strength or somewhere in the middle. I don't think you will find a durability issue with either, but obviously if the kevlar is lighter, it is probably a little thinner (assuming they have similar density), which sort of equates to less material available to wear away but since few people wear through the gel coat in ordinary use this is really not a concern. People who wear through specific areas tend to fid kevlar rubbing stips (keel strips on sea kayaks, skid plates on canoes) because kevlar is good at resisting this sort of thing....

Jim

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GordB
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Post by GordB » Wed Mar 21, 2007 8:55 pm

Jim wrote:As far as I know Diolen does not have quite the same tensile strength as Aramid (Kevlar), but is in the same league and considerably cheaper. The result is that a builder can use a bit less kevlar for the same strength or the same amount for a bit more strength or somewhere in the middle. I don't think you will find a durability issue with either, but obviously if the kevlar is lighter, it is probably a little thinner (assuming they have similar density), which sort of equates to less material available to wear away but since few people wear through the gel coat in ordinary use this is really not a concern. People who wear through specific areas tend to fid kevlar rubbing stips (keel strips on sea kayaks, skid plates on canoes) because kevlar is good at resisting this sort of thing....

Jim
Hi Jim

Thanks for the comments.
I had planned to add a rub strip no matter which way I decided to go.
From some PM's I've received on the matter, I've decided on the standard Diolen layup.
Only two things left to do prior to ordering. Track down a colour chart and convince the better half that I really need one.

Gord

Chris Bolton
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Post by Chris Bolton » Wed Mar 21, 2007 8:56 pm

As Jim says, but in general kevlar boats are made lighter but still at least as durable (against shock and impact) compared to diolen. The kevlar fabric is very difficult to break, even if the resin matrix is cracked - I've seen kelvar boats folded and then straightened out, and paddled the next day with a dab of resin on the fold. I've also seen diolen boats which delaminated when subject to severe shock. That's not to say diolen isn't a good material; my main expedition boat is diolen and is in good nick after 17 years use. Durability against scratching and wear is more a matter of gelcoat type and thickness; if I wore any boat down to the fibres I'd be worried - apply gelcoat, patch or keelstrip before it gets that far.

If you can afford the kevlar, and are likely to carry the boat on land, I'd go for that. It will be useful if you're doing a long carry to the water, or up a beach on a solo trip, and I think it will be more robust. In the water, you won't notice the weight difference as much, unless you're paddling it empty.

Chris

marykerry
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kelvar vs diolen

Post by marykerry » Wed Mar 21, 2007 9:05 pm

I had a kelvar sirius until one awful day it came flying off my car on the A55 when the footplate of my roofrack snapped.
I replaced it with an ex demo diolen one.
I actually prefer the diolen one as it is more controlable in windy conditions as it grips the water better. I am fairly light and that combined with a light boat meant wind had better grip on direction than me. I find my new boat responds well to a using the right edge for the conditions. ..only once I had the seat/backrest and footrests adjusted to suit me.


all the best with your boat
Mary

Chris Bolton
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Post by Chris Bolton » Wed Mar 21, 2007 9:34 pm

I nearly added that an empty kevlar boat will be blown about more; my boat, although diolen, is quite high out of the water, and I find it blows about when empty. I thought of Mary's kevlar Sirius and wondered if she found the same - now I know!

I notice Gord posted to say he'd decided on diolen at the same time as I was writing my thoughts. I'm sure you'll be pleased with it, Gord.

Chris

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GordB
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Post by GordB » Thu Mar 22, 2007 2:29 am

I have noticed the " lightness" of kevlar tends to allow the boat to be blown about when empty. And I am not a lightweight.

I'm on my second kevlar boat now. The first rode very high in the water when empty and tended to weathercock quite a bit. Loaded of course it was another matter.

My current boat ( with a very light kevlar layup ) rides fairly low, though that might be due my added mass. Empty, or loaded for a day or two, it handles well. More than that and I may as well have a submarine.

The anticipated purchase of the Nordkapp, when She who rules my world grants me leave, will be my main touring boat while the other will be relegated to play. Any carrying I may have to do will be of relatively short distances but I will have an added reason to try to convert some recently added mass to something useful.

Thanks for your comments

Gord

Westview
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Post by Westview » Thu Mar 22, 2007 4:13 am

What is the weight difference between a diolene vs kevlar layup ?

Owen
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Post by Owen » Thu Mar 22, 2007 9:13 am

From the Knoydart catalogue,
Standard layup = 25kg.
Pro-kevlar = 22kg.
Ultra-kevlar = 20kg.

Pro-kevlar uses kevlar cloth and polyester resin.
Ultra-kevlar uses kevlar cloth and vinylester resin both use a vacuum-resin-infusion prosses. The standard is hand layup.

p.s. This is for Valley boats.

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Jim
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Post by Jim » Thu Mar 22, 2007 3:29 pm

Interesting to hear that you all find lightweight kevlar boats really do float higher and blow around more than heavier models - obviously from my profession I understand this but I've never heard anyone say it is actually noticeable in real life. I might need to build a new Kevlar boat before Easter (re: the damn photo) - when is that by the way?

Jim

Chris Bolton
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Post by Chris Bolton » Thu Mar 22, 2007 8:01 pm

Jim,

The weight of the boat is irrelevant if it is small in comparison to the weight of the gear piled onto it!

(as I'm sure you know but I had to say it ! )

Chris

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Geoff Seddon
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Post by Geoff Seddon » Fri Mar 23, 2007 1:04 am

Good Friday is the sixth Jim. I think that's the travelling day.
Geoff

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Jim
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Post by Jim » Fri Mar 23, 2007 10:39 am

So, Today is the 23rd, 30 days in September, April, June and November, 28 or 29 in Feb and the current month is none of them so must be 31 days. 31-23=8
8+6 = 14 days.

So 2 weeks to borrow a mould, prep it, buy materials, laminate and outfit a new boat in my spare time which I have virtually none of at the moment?

Looks like I'm using my current boat then!

Jim

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Pelagic
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Post by Pelagic » Fri Mar 23, 2007 10:54 pm

Looks like I'm using my current boat then!
You can always borrow one of my boats Jim, How about the Greenlander?
It's chined (I Know you like that), has acres of deck space (very useful and mainly flat) and it's kinda pretty.
Usual caveats regarding NDK boats, cockpit is not actually guaranteed to stay attached to the boat and the skeg only works when it feels like it (never when you need it) and it probably leaks a bit.
It does track beautifully and surfs better though...........
It's yours if you need it.

Phil

Hey I've just discovered the Firefox spell checker works here, strangely enough it's just underlined Firefox......................that's odd!

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Jim
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Post by Jim » Mon Mar 26, 2007 12:37 pm

Since I added ~5 kg of "waterproofing" to my boat last year I think I should stick with it and see if it actually worked at all...... I seem to recall the keel was worn through/cracked in more than 10 locations and required extensive filling and a colour matched keel strip. I also added a lot of material inside under the seat where the worst of the damage was and attempted to sikaflex the bulkheads, except that the 'winder' for squeezing the tube backfired spurting the stuff all over me so I had to apply it as best I could with a finger from the pile it ended up in......

It's had a couple of short trips since then but hasn't been properly evaluated for dryness under full load, given how little shipped through all the old cracks (forthe number I found) it should be fine :D

Quite tempted by the Greenlander Pro, but I really should avoid doing anything that may lead to me wanting to buy a new boat, at least until I have storage sorted.

Jim

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Pelagic
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Post by Pelagic » Mon Mar 26, 2007 2:58 pm

Quite tempted by the Greenlander Pro, but I really should avoid doing anything that may lead to me wanting to buy a new boat, at least until I have storage sorted.
Grab a chance, then you will never be sorry for a "might have been"

Arthur Ransome

Or............be quick, or Chris gets it..................

Phil

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