CARBON VS. VACUUM GLASS

I am currently paddling a carbon Fenn Elite and am looking to upgrade to the Elite SL. When I bought my Elite there was a choice of a standard glass layup at 17kg vs. carbon at 11kg, so the decision to go for carbon wasn't too difficult.

With the introduction of vacuum glass at 14kg things get more complicated, especially considering that the carbon ski is 80% more expensive (in SA) than the vacuum glass.

The question is whether the carbon is worth the additional cost in terms of speed, stiffness and strength? Also, I don't want to buy a glass vacuum Elite SL only to find that its no faster than my carbon Elite i.e. the faster SL design is offset by the change from carbon to vacuum glass.

Comments?

I'll be interested to see other feedback on this topic but...
With my less-than-perfect balance, I've found carbon boats to be appreciably tippier, partly I suspect because of the weight (perhaps making them more prone to being thrown around by the chop) and almost definitely because of the stiffness.

So the vacuum glass boat might be a little less stiff, but if you're like me, you might find it more stable and therefore faster because you're not losing efficiency to efforts to stay upright. (And it doesn't take much to disrupt your stroke.)

I have two Mako Elites - and perhaps it's just in my mind, but I feel that the newer (lighter and stiffer) one is slightly more tippy. So I've been paddling my battered old one - the new one is wrapped in a cover in my carport!

I also found that for me (mid-packer, less than perfect balance) the slightly increased tippiness of the SL wasn't offset by speed to any appreciable extent. So I wouldn't go for an SL anyway.

Hi Robin, I'm fortunate in that tippiness isn't an issue for me. I'm very stable in my carbon Elite (can't remember when last I fell out of it) and I've tried a carbon SL, and while it is a bit more lively I was also comfortable in it. So stability doesn't really come into the equation, its a pure speed / stiffness / strength question.

Nigel

Must say that speed vs stability issues aside ( I know these are the main concerns usually) that all the skis i have seen with cracked seams and other similar issues have been carbon , I know Iknow , we all know it is stiff and brittle , with the vacum bagging =less weight and the slightly greater flexibility I reckon the glass is a more durable , seaworthy choice. NOT to say carbon ain't nice , glass is more practical for an "everyday" boat (disclaimer here IMHO). Really intrigued with seeing more trend to the "multi" material layups (ie epic/stellar , and let's not run down that road again) and also curious as to the fade of kevlar boats. The Soric core glass vacum infused Think composite seems quite a nice balance(speaking to the layup only ! )

Sandy as you say, the multi material boats make a lot of sense, while my Hybrid Vault is around 12.7kg it a combination of Glass and Carbon, giving it stiffness and everyday robustness, the full carbon is obviously more light but I would be scared to own one for fear of damaging it, I'm bad enough mothering my carbon road bike

As you say Epic (to my knowledge) have been pioneers in this multi material idea and our local Think Rep is selling ski's that are no longer made in lay-ups they used, so there is more being done by manufacturers to get the mix right.

What would be exciting is to see multi material fabric being used where they weave different material strands together in the one cloth, I have seen this available but perhaps it is too expensive for the ski application just now.

Vacuum infused Soric or equivelent cored fibreglass with strategic carbon or similar re-enforcement is the backbone of the industry now.
With most manufacturers claiming in the 14 to 15kg weight for a complete ski.
How many actually are that weight would be interesting, not many are ever weighed.

Changing the fibreglass to carbon and using the same basic layup only gives you a stiffer boat, it won't be much lighter.

The only way to go significantly lighter is to change to a nomex honeycomb type core and doing this requires a wet layup with vacuum bagging.
Carbon and kevlar both seem popular choices for the layers either side of the core.
With a much larger production cost.

A full carbon, kevlar or combination, boat, again a wet layup uses the dearest fibre and the dearest production costs.

Interesting is the Vajda kevlar model, it obviously has a honeycomb core of some sort, it's quite visible, and comes in lighter than anything else on the market, it also feels to the touch to be very impact forgiving.

I don't agree that carbon boats are the ones I see cracked.
All of the cracked ones I have seen have been fibreglass types, except for one carbon type.
This was a Fenn which is still a heavy layup for a carbon model.
Certainly heavier than other carbon competitors.

For me, I don't find lighter boats more tippy, as tippy to me refers to the stability curve offered by the hull and has nothing to do with the weight, they are in my book, more reactive, in that they pass on information from the water quicker than a heavier layup, and this I like, as it gives my body more warning to react to something if need be.

It doesn't matter what it is I drive/ride, I have always liked things on the side of being twitchy over stable.
But in this I am not referring to it's basic hull stability just the weight type thing.

I have never felt a ski to be blown around, probably because I am a bigger type. I doesn't even figure in my consideration of a ski.

So I like the light ones, the lighter the better in my book as long as it doesn't break or cost more than I value a ski.

I think that a lighter layup simply doesn't mask the real hull design and lets you feel the real stability offered by the design without the weight smudging the feeling.

Right now, I am suspecting that a light hull is more important than the ultimate in slipperiness, as in I think that possibly a slightly more stable slower hull shape, but lighter, is possibly quicker than a heavier slippery one.

I would really love to see a back to back with something like an Elite in the lightest layup verses the SL in a heavier one.

Once in the waves, I think two boats as different in flat water speed as a V10 and a V10 sport, may even reverse their speeds if the sport were to be carbon and the V10 to be the basic layup.

There are a lot of 'too light' carbon spec skis getting around down here, and they always impress.

Interesting you should mention stiffness Rob, as when Epic did their impromptu stiffness tests, they seemed to come up with higher stiffness for the basic layups, and less for the carbon?

I honestly think a stiffer boat would be more predictable than a wobbly boat, and that is more important to me than the weight induced movement.

I so wish I had access to some boats for testing to determine this.

Maybe I can arrange this now I have some more time on my hands as I am keen to know before I purchase my new ski.

What sort of conditions do you paddle in RAB. I suspect that the wind on your side of the country is a trifle more gentle than in the west. There is no doubt a lighter boat is better in small to moderate conditions but in any sort of wind and chop they are a lot more difficult to paddle. Do you tend to paddle in lighter winds or 20 knots plus. Are you in sheltered water away from sidechop or 2km out to sea, cos I think it's important to consider these things when choosing a boat. If you fall in on the Gold Coast, you go for a pleasant swim in warm water. If you fall off in some places you risk hypothermia. I think most folks would find a lighter stiffer boat more difficult to paddle, but if you paddle in moderate conditions a lighter ski is a better option.

We are perhaps making too much about weight here. The primary factor with respect to stability is width / beam. If you don't want to risk hypothermia in WA (which isn't really all that wild in any event and has relatively warm water anyway), buy a fat boat - V10 Sport, Swordfish, Evo 2, etc. After that decision, the question is what layup. As a guide, anything that you want to go fast efficiently should be as light as possible (bicycles, boats, cars, airplanes). This is especially critical if it is human powered. Once you have settled on a boat, I would buy as light as you can afford. Yes a light boat will be more twitchy than a heavy boat, but twitchy isn't bad and the difference in stabiity based on layup only will be minimal. Light boats are better in the flat (obviously) and better in the runs because they accelerate better.

You will not find any forum discussions on whether a heavy bicycle is better than a light bicycle.

A different question is the value proposition. The Fenn vacuum glass skis are incredible value for weight.

Unfortunately Metro you have over simplified the issue of stability. Width and beam do add stability, as does hull shape.
Where you and RAB state that lightweight boats are twitchy in fact they are more unstable. Fibreglass boats/heavier boats flex in the middle. This has the effect of lowering your centre of gravity by a couple of centimetres, just like lowering the bucket in your ski.
Carbon boats don't have the same degree of flex, hence you sit higher, hence the boat is more unstable. Flex also creates drag, so do lighter boats accelerate faster because they are lighter or because they create less drag.
The same effect is caused by rocker. Boats with less rocker should by rights be more unstable. I have a nack of buying boats with bugger all rocker, which are fantastic where I paddle, but cause me to struggle when I race in conditions I'm not used to.
The big question with vacuum bagging is, does the lighter boat actually flex more. The answer will be probably be yes. So therefore it will probably be intinsically more stable but won't accelerate as fast as a carbon boat because of the drag caused by the flex in the middle of the boat.

I don't believe that the most significant factor is beam.
If a boat puts more boat under you on the side you are leaning to, then it will feel stable.
This is a hull shape factor, not a beam width.

The V10 and V12 are the same width, but have completely different stability profiles.

A very wide hull just has the ability to keep adding boat under you for longer, so therefore you can add more self correcting earlier and not run out of hull.

The cross sectional hull shape decides the stability profile and importantly, if that profile matches what you expect to happen, it will feel great.

If the self correction of the hull comes on too slowly or too fast for your body dimensions, then it will not feel as good as a profile that just seems to have the right amount of support applied as you lean it.

Skinnier boats must give you less initial stability so as to have stability in reserve for when you lean it.


Now here is what I think may be important.
Most midpackers paddle too slow, as in their stroke rate is too slow.
This leaves them with a long time between paddles on either side.

A short paddle and a higher stroke rate gives a much more stable feeling as the paddle is never far away from where it is needed to make minor corrections.

One of the reasons why aggressive paddling feels more stable.

In general, most people paddle too bloody slow, much slower turnover rates than running or cycling.

The long paddles that paddle slow are also much more wind effected as well as leaving the boat more wind effected.

Since I have gone to a super short paddle, I simply do not notice the wind apart from extreme sudden gusts.
I am also much more comfortable in all over the place mush.
So not only do I get to run higher HR with more power, but I gain several points in stability.

If correction strokes are required, they are much smaller and are simply incorporated into the normal stroke as they occur before it gets out of hand.

I often give people a go at my shorter paddle and they always look more comfortable, but because it is out of the norm, they always have the suspicion that a longer paddle is faster because that is what the local guru has recommended.

Mid packers are running 213 to 217cm paddles, yet when you find out what the pro's are using, they are in the 210cm range.
Yet the pros are paddling much faster, their cadence is much faster.

So there is my number one tip for greater stability, get a paddle that allows a good high speed cadence to be used.

A lighter boat also feels to gel with a faster cadence to me as well, because the boat responds with the same sort of speed as you are moving your own body.

As to flex, I don't believe that there is any appreciable sag in the middle of the boat when on the water.
The largest volume is right near the cockpit, so there is little overall bending stress on the boat.

There is also quite a lot of extra strength built in around the cockpit area to cope with the high bending loads that occur when heading out in shore break conditions.

If there really was a large amount of bend, coming down off the back of a wave would not be nearly as violent as it is.


I think the biggest effect of varying amounts stiffness will be a twisting of the hull shape that distorts it's true running and generally makes the boat mis-track.

Rob and Dale showed fairly conclusively the varying degrees of flex between different layups somewhere in the past. RAB when you state the largest volume is at the cockpit so it doesn't flex, I think you forget that water is not a static base, it displaces.
If your nose is in a wave and the tail is in a wave, the cockpit will flex....not if your boat is carbon, but if it is glass.
Conversely any downward pressure ie, sitting in the boat, will cause the water under the cockpit to displace. This alters the hull shape of the boat. It may be slight, but it may be enough to cause us to spend money to buy a carbon boat. By your reckoning a good dose of gastro that sees me lose 2.5 kilos would see me accelerate my current boat like a carbon boat next time I paddle it.
This doesn't happen.The rougher the conditions you paddle in the more noticable the effect.

Pass the popcorn I'm really enjoying this thread.

Width of a ski can be an indicator of stability but depends on how it's used. When I got my Vault I was cheeky enough to put in down next to quite a few other ski's before and after training and races to study the hull shape differences.

From the top of the ski it looks fat behind the seat but that width only comes into play as the hull nears the deck, to put it in simple terms it's more of a V shape where the width only comes into play as either the ski rolls or the waterline comes up the sides. This differs from say the V10 sport where the width is acting on the waterline much sooner, so it is more of a U shape. This hull shape question is fascinating as this area behind the bucket seems to be the sweet spot for stability, especially in downwind conditions, the way this area transitions away from a flat surface to the typical cylinder shape of the bow and stern must do designers heads in taking into account wetted surface area (drag), boat lift (downwind) and water line length, rocker etc etc, learning about this stuff gives you an appreciation of why certain boats love some conditions and hate others. When Rob has reviewed skis in the past he has run string lines over the hull and placed the ski beside other skis, at first this didnt mean anything to me, but as you pick up on how hull shape effects the ride these pics do tell the paddler more about how a ski should perform.

Rightarmbad wrote:
Now here is what I think may be important.
Most midpackers paddle too slow, as in their stroke rate is too slow.
This leaves them with a long time between paddles on either side.

A short paddle and a higher stroke rate gives a much more stable feeling as the paddle is never far away from where it is needed to make minor corrections.

One of the reasons why aggressive paddling feels more stable.

In general, most people paddle too bloody slow, much slower turnover rates than running or cycling.

The long paddles that paddle slow are also much more wind effected as well as leaving the boat more wind effected.

Since I have gone to a super short paddle, I simply do not notice the wind apart from extreme sudden gusts.
I am also much more comfortable in all over the place mush.
So not only do I get to run higher HR with more power, but I gain several points in stability.

If correction strokes are required, they are much smaller and are simply incorporated into the normal stroke as they occur before it gets out of hand.

I often give people a go at my shorter paddle and they always look more comfortable, but because it is out of the norm, they always have the suspicion that a longer paddle is faster because that is what the local guru has recommended.

Mid packers are running 213 to 217cm paddles, yet when you find out what the pro's are using, they are in the 210cm range.
Yet the pros are paddling much faster, their cadence is much faster.

So there is my number one tip for greater stability, get a paddle that allows a good high speed cadence to be used.

.

Amen brother! Wish I had got my split paddle done in a 208-218 or less. Currently using the minimum 210 downwind and find that 213 on the flat it as much as my shoulders will turn over at race pace. I would think I would better going down to around 208 downwind. What I do now is reduce my stroke length to increase cadence thus improve stability in the rough stuff.

As for the question of vacuum bagged glass, I must admit it makes my nervous hearing how light the latest bunch of glass only ski's are. A couple of years ago I was told by many long time ocean paddlers than Fenn made bullet proof boats, while generally heavier they would last, I'm not going to pass judgement on the new light ski's, perhaps their boat engineering has found a way to make them light and robust but I'd be wary of a really light glass only ski. Perhaps with the competition in the marketplace now the manufacturers have felt the pressure to get lighter and lighter....perhaps at the expense of longevity.

One often overlooked aspect is the core material being used, I don't know a lot about the Soric or nomex etc but perhaps LATS or someone else with boat building experience can weigh in here (pardon the pun)

There's a couple of articles in the archives on this issue, one which looks to an EPIC marketing excercise on how stiff their skis are and this one about some Red7 testing which makes for a good read www.surfski.info/reviews/item/300-stiffness-and-stability.html

I run 205 to 207cm depending on conditions.

The really interesting thing is that I can now paddle at high speeds when before I was too bloody scared to even put it in the water.

As in surfing in front of a wave and watching the bastard kick up to scary size, I can now start paddling at insane speeds and go off the front of it before it mashes me.

I simply cannot do that with a longer paddle, I just cannot get the thing back in the water at those speeds without it threatening to turf me out of the boat.

With the short paddle it is easy to do.

I don't think anybody should be buying 210 - 220cm for surfski, 205 - 215cm is the way to go.

Most mid level glass boats you will find are infused not bagged.
Infused for a dry layup with an infusion core like Soric, bagged for a wet layup and using things like a nomex core which cannot be infused.

Lats uses infused fibreglass with a soric core.
Layed up dry.

AR, a V shape hull is inherently a more stable hull than a rounded or slightly flat bottomed one.
At the expense of a greater wetted area.

The easy rule of thumb for stability, is the more it looks like a cylinder, the tippier it is, the less, the more stable it is.
A V shape is quite a departure from a pure cylinder.

The Stellar SES is a way skinny boat, skinnier than any other ski I have seen, yet it is not unstable.

Something that the followers of 'carbon is stiffer rule' forget, is that, yes it is, when you use the same amount of material, but don't forget, the carbon boats weigh only 1/2 to 2/3 of a glass one.

Pound for pound it is stiffer, but there just isn't as many pounds used, so the stiffness is not necessarily higher and may more often than not be lower.

The main concern of the designer is, 'is it strong enough'.

Have a look at the V10 showing the internal stringers:

www.surfski.info/reviews/manufacturers/i...5-the-v10-story.html

I wonder if maybe they have a larger part to play in the overall bend of the boat compared to the layup.

And Epic's cobbled together flex test:

www.surfski.info/reviews/manufacturers/i...nt-of-stiffness.html

Thanks for those pages RAB, there is truly a wealth of good info on this site if you can be bothered searching.

While I had an idea of what a stringer may be, the set-up around buckets (seats) had me scratching me head, and while this pic of the epic set-up may not be true for all ski's it helps me to understand it better.



Getting back to the Carbon V Vacuum glass, reflecting on the conversation so far, while I have been reluctant to get a carbon ski for fear of not having the presence of wind to pay proper attention to it's care, I can see no reason why you wouldn't buy a vacuum bagged glass ski if you think you are capable of protecting it from bumps and knocks away from the waters edge.