Carbon helmet layers

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Swampthing
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Re: Carbon helmet layers

Post by Swampthing » Sun Feb 21, 2010 8:08 pm

If you want to see the carbon/kevlar yellow black chequer weave which is fantastic, then it must be sprayed with UV proof clear laquer as epoxy is destroyed by sunlight.
Lost your job? Wife ran off with your best mate? Bailiffs coming for the Audi? Thinking of topping yourself? Dont call the Samaritans, come for a paddle.
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drking
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Re: Carbon helmet layers

Post by drking » Mon Feb 22, 2010 9:02 pm

Ok, so I released the lid today. I came out alright. Its very strong and super light. As it has gel coat on it i'm gonna use it as a tester. Do the Jonny style video and drop rocks on it. I shall take some video / photos. Then i'm going to order some more fabric and make a proper one to actually use. I'll let you know how I get on.

Thanks again. If you have anymore wisdom to send this way, feel free.

Dan.

BigMike
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Re: Carbon helmet layers

Post by BigMike » Mon Feb 22, 2010 9:43 pm

Swampthing wrote:If you want to see the carbon/kevlar yellow black chequer weave which is fantastic, then it must be sprayed with UV proof clear laquer as epoxy is destroyed by sunlight.
From memory west 105 epoxy is "UV proof"

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Swampthing
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Re: Carbon helmet layers

Post by Swampthing » Mon Feb 22, 2010 9:50 pm

Nice one, would be interested to see that vid. Good luck with the project
Lost your job? Wife ran off with your best mate? Bailiffs coming for the Audi? Thinking of topping yourself? Dont call the Samaritans, come for a paddle.
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Swampthing
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Re: Carbon helmet layers

Post by Swampthing » Mon Feb 22, 2010 9:53 pm

BigMike wrote:
Swampthing wrote:If you want to see the carbon/kevlar yellow black chequer weave which is fantastic, then it must be sprayed with UV proof clear laquer as epoxy is destroyed by sunlight.
From memory west 105 epoxy is "UV proof"

No it isnt
Lost your job? Wife ran off with your best mate? Bailiffs coming for the Audi? Thinking of topping yourself? Dont call the Samaritans, come for a paddle.
3 cheers for rap music.........Hip hop.................

anthony
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Re: Carbon helmet layers

Post by anthony » Mon Feb 22, 2010 9:57 pm

Hi, whilst developing some composite techniques in a former life, i actually developed a way of popping vacuum infused parts ready primered, thus saving weight over using gel-coat, it also means that once the part is popped, you just neaten off the flash/edges, scotch the surface and paint.

This is what i do now....

http://www.autostyl.co.uk

and specialise in House of Kolor kustom paint, like on my latest creation

Image

This roof is actually clear coated with a marine clear coat - and gives fantastic Distinctness Of Image as you can see, and is made for the job - i just happen to like the way it flows, and use it on some automotive jobs too.

Image

Where abouts in Cornwall are you? I live in Newquay, but my workshop is in Truro... let me know if you want any more info on how to produce primered parts out of the mold, or if you want some kustom paint shot on one of your lids! Would be good to also meet more folks who might be up for lift sharing etc from here up to Dartmoor, Hurley etc. from Cornwall.

Ant.
http://www.autostyl.co.uk Custom Automobiles

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Swampthing
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Re: Carbon helmet layers

Post by Swampthing » Mon Feb 22, 2010 10:06 pm

For Bigmike---------------

http://westsystem.com/ss/adding-pigments-to-epoxy/

second to last paragraph
Lost your job? Wife ran off with your best mate? Bailiffs coming for the Audi? Thinking of topping yourself? Dont call the Samaritans, come for a paddle.
3 cheers for rap music.........Hip hop.................

BigMike
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Re: Carbon helmet layers

Post by BigMike » Mon Feb 22, 2010 10:06 pm

Swampthing wrote:
BigMike wrote:
Swampthing wrote:If you want to see the carbon/kevlar yellow black chequer weave which is fantastic, then it must be sprayed with UV proof clear laquer as epoxy is destroyed by sunlight.
From memory west 105 epoxy is "UV proof"

No it isnt
Just had a google. West website says the 105/207 system has UV "inhibitors" which I guess doesn't mean "proof", but does mean it's not totally naked if you see what I mean?

BigMike
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Re: Carbon helmet layers

Post by BigMike » Mon Feb 22, 2010 10:07 pm

Post crossed. Thanks for that, Swamp.

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Re: Carbon helmet layers

Post by Gwynfor » Tue Feb 23, 2010 3:26 am

Interesting discussion going on here! I am just going to throw some of my experiences into the mix;

1. Canoeing helmets are intended for relatively massive low speed blunt impacts (person hitting smooth rock at the speed of the water), as opposed to climbing helmets (small sharp rock hitting head very fast). To do their job properly, the energy of the impact needs to be partially absorbed and partially dissipated in time. One of the indicators used to determine likelihood of head injury (and measured during CE testing) is maximum instantaneous acceleration of the head. Driving a car over it, while impressive doesn't make it a good canoeing helmet!
2. Having a very hard, rigid shell means that all of the important work of the helmet (dissipating the impact) needs to be done with the foam liner, and so needs lots of foam. From memory, 12mm of closed cell foam in a very rigid helmet failed to reduce the maximum acceleration to acceptable levels.
3. A thinner shell will deform more, thereby absorbing some energy. Obviously having the shell too thin will mean that impacts can puncture it.
4. A resin failure (cracking or crazing) will absorb more energy. Good polyester resins have a higher capacity to absorb energy this way than epoxies.
5. Using reinforcements that undergo plastic deformation before failure will absorb yet more energy. Things like kevlar, dynel, diolen, spectra. Carbon fibre, while very strong in tension is brittle and not a good choice. Most reinforcements other than glass are sized (treated) to bond to epoxy though - check before you use them with polyester.
6. Fill as much of the inside of the helmet as you can with good quality, thick closed cell foam - this is what will protect you most!
7. West system 207 hardener has UV inhibitors added, and is clear so will show the fabric nicely if you still want to use epoxy.
8. Kevlar is also not very UV stable!
9. You are in the UK - how much canoeing do you do in the sunshine anyway? Just don't store your helmet on the windowsill!
10. I feel that there hasn't been nearly enough discussion of the merits of glitter. Store bought glitter is nowadays just coated plastic and will melt into a gooey mess in the resin. Proper metalflake can be bought from all self- respecting composite supply firms....

Have fun out there

Gwyn
www.shaggydesigns.com

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Re: Carbon helmet layers

Post by davebrads » Tue Feb 23, 2010 2:46 pm

Gwynfor wrote:Carbon fibre, while very strong in tension is brittle and not a good choice.
Interesting Gwyn, when so many top helmets use carbon fibre. I agree with you by the way.

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Re: Carbon helmet layers

Post by TheKrikkitWars » Tue Feb 23, 2010 4:18 pm

davebrads wrote:
Gwynfor wrote:Carbon fibre, while very strong in tension is brittle and not a good choice.
Interesting Gwyn, when so many top helmets use carbon fibre. I agree with you by the way.
I think this is why Sweet Composites have moved towards using Tepex, which has a rather more flexible matrix material [Poly(Propene) I believe] to counteract the brittleness of a stiff reinforcement in a stiff matrix material.
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BigMike
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Re: Carbon helmet layers

Post by BigMike » Tue Feb 23, 2010 5:24 pm

This is total bar room science admittedly, but surely with carbon being brittle, a heavy impact will crack it, and that process helps energy absorbtion? Do you actually want the ability to bend/deform without cracking in a helmet?

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Re: Carbon helmet layers

Post by Rdscott » Tue Feb 23, 2010 5:32 pm

Bigmike the facts are that carbon is expensive and you are right on how it would work.

However in a world where money is a large part of life, would you be willing to shell out for a helmet at £140 everytime you hit it on a rock.
kayak helmets are suposed to be mulitple impact, or have the ability it stay together after an impact, it would be highly inconvinient if you cracked your helmet and had to finish the run with nothing on your head, I truly belive something is better than nothing even if it is a helmet that needs replacing when i get off the river.

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Re: Carbon helmet layers

Post by TheKrikkitWars » Tue Feb 23, 2010 5:42 pm

Rdscott wrote:it would be highly inconvinient if you cracked your helmet and had to finish the run with nothing on your head
It is extremely scary; I wouldn't want to experience that ever again.
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Jonny Briggs
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Re: Carbon helmet layers

Post by Jonny Briggs » Tue Feb 23, 2010 5:56 pm

Its a long shot, but.

Does anybody have a copy of the CE1385? Its £55 and I don't really want to pay for it.

My rock dropping/ test was done as a piss take really, just wanted to see the physical strength of the glass fiber.

So what would be the ultimate layup/ laminate for a kayaking helmet then? Money is no option.

Jonny

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Re: Carbon helmet layers

Post by Rdscott » Tue Feb 23, 2010 6:11 pm

A aerospace engineered helmet with a high impact absorbing iinterior.

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Re: Carbon helmet layers

Post by Jonny Briggs » Tue Feb 23, 2010 6:41 pm

Whats aerospace engineering then? And how will it be used for helmets.

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Re: Carbon helmet layers

Post by Rdscott » Tue Feb 23, 2010 6:46 pm

I duno (but it sounds good) i guess it would be the engineering processes which are used in arospace stuff, the kind of thing BAE deal with.

It chasis used in bowler and tomcat race 4x4's use this kind of thing, you can crash them jump them and genraly hit things at high speeds and it doesnt break, this kind of stuff fitted with high impact foam (replaceble) molded to indavidual heads would PROBABLY be indistructable, light, but very very expensive.

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Re: Carbon helmet layers

Post by Swampthing » Tue Feb 23, 2010 6:50 pm

I dont think you can class the posible impacts as "relatively massive" Were taliking 5mph on a good day. Just spreading that load over as large an area of cranium is probably going to be enough with a little foam also. But agreed , its mostly hype and bling factor and a padded yellow builders helmet would do the job admirably if you didnt mind looking an ar$e :-}
Lost your job? Wife ran off with your best mate? Bailiffs coming for the Audi? Thinking of topping yourself? Dont call the Samaritans, come for a paddle.
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Re: Carbon helmet layers

Post by Gwynfor » Tue Feb 23, 2010 10:15 pm

Hi Swampthing,
Sorry, I was being a bit unclear by what I meant. By relatively massive, I meant that the impact is effectively of a lot of mass (a person, plus kayak usually) against an immovable object - the rock. This is compared against climbing helmets designed to protect against rocks of a few kilograms at most moving at high speed.

From experience, carbon is not the best material for most kayaking related uses. Anyone remember the carbon projects that broke on contact with rocks? Lots of carbon fibre so very rigid, but unable to withstand impacts. Whereas a Kevlar boat, while not being so rigid would be much more able to withstand repeated impact. A kevlar boat can be made rigid by suitable engineering of internal pillars and supports - much like plastic boats.

Gwyn

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Re: Carbon helmet layers

Post by BigMike » Tue Feb 23, 2010 10:56 pm

Or by using....carbon!

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Re: Carbon helmet layers

Post by Swampthing » Tue Feb 23, 2010 11:47 pm

Hi Gwyn, exactly what I said about 20 posts back (carbon brittle and needs some kevlar in there too)
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Re: Carbon helmet layers

Post by davebrads » Wed Feb 24, 2010 7:27 am

A friend of mine had an ex Bala Worlds (1981) Kevlar C1 which would have been laid up with Polyester Resin. By the time he got it it was so flexible that you could see it bending as he paddled over the waves at Matlock. Impossible to break though....

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drking
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Re: Carbon helmet layers

Post by drking » Wed Feb 24, 2010 8:18 am

Right,

So my best lay up options for my project helmet would be Carbon/Kevlar weave? Carbon layer/ Kevlar layer repeat? All Kevlar? Definately Epoxy over Polyester resin?
I have decided not to chuck rocks at my first carbon/kevlar attempt and have decided to get a friend to test some painting on it. He's a car sprayer and has recommended a few layers of 2-pack paint and doesn't think it would need lacquer. We will see how it turns out.

Lots of good information coming out in this post, Great.

Dan.

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Re: Carbon helmet layers

Post by guy » Wed Feb 24, 2010 1:18 pm

Carbon/Kevlar weave? Carbon layer/ Kevlar layer repeat? All Kevlar? Definately Epoxy over Polyester resin?
Yep Carbon Kevlar weave because it looks good. Epoxy because it sticks woven cloth better than Polyester.

But as Swampthing says anything will do ( you have a mould and can make a new one it it cracks)
It is getting the foam right that will be tricky.

You need to decelerate your head as slowly as possible when your helmet hits a rock

iPhones have an accelerometer perhaps there an app for testing foam!

there you go
http://www.switchonthecode.com/tutorial ... elerometer

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Swampthing
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Re: Carbon helmet layers

Post by Swampthing » Wed Feb 24, 2010 6:22 pm

drking. Thats right, you will not need UV proof clear laquer if you are colour painting the lid. You only need the laquer if you want to see the carbo/kev weave as a style feature. Also ,do not discount biaxial or triaxial glass cloth, bit more shock absorbtion than carbon and cheaper, not a huge weight disadvantage on a small item like a skidlid, good drape so wont need to snip it. Available from Matrix Mouldings bristol. Definately no polyester resin, use epoxy, much more working time, better mechanical properties and for the small amounts youre using extra cost wont be huge. Hope I havent confused you even more.Good luck with the project.
Lost your job? Wife ran off with your best mate? Bailiffs coming for the Audi? Thinking of topping yourself? Dont call the Samaritans, come for a paddle.
3 cheers for rap music.........Hip hop.................

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drking
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Re: Carbon helmet layers

Post by drking » Thu Feb 25, 2010 8:04 am

Cheers Swamp. I'll check out the tri and bi axial cloth. I think i know where i'm heading with this now.

Thanks,

Dan.

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Re: Carbon helmet layers

Post by blitz66 » Tue Mar 02, 2010 1:55 pm

i've always wondered about the carbon helmets... i mean surely for something like kayaking when you hit your head, you don't want something that stiff? because it'll still transfer all of it's energy straight through to your head, because there's no flex in it? so the foam does all the work.... as such, a helmet with a slightly more flexible construction, i.e. HDP, Kevlar etc etc whatever, will dissapate impacts better? blunt force impacts that is..

then there's the problem of the helmet deforming with your head in it, which isn't all that good... so maybe something like a carbon skeleton, i.e. band around the head, and another (one or two) over the head, to stop any major deformation, under a more flexible shell which can deform at the site of impact, but not just crush your head would be an idea?

finally, foam, if you have a foam that'll return to it's origional shape, blocks/bands of foam would be better than a solid foam layer surely? as the gaps in the foam allow your the foam to expand and compress a little more/ to a greater amplitude, which means your head slows down over a longer distance, i.e. less G.

just my thoughts =D

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