Carbon vs Fibre - when is it faster or slower?

This is a very interesting thread.

So, a f/g ski may very well be faster than a carbon ski in conditions (call it big downwind or triangular course with/into the wind and swell).

Wesley of surfski-racing fame has an impressive comparative chart. On this chart I think that each carbon (or kevlar) ski is faster than its f/g sibling. Then again almost all this data comes from flat water paddling.

If Rob had a similar chart and does the comparisons on Millers runs (good down winds) does this imply that the ugly sister may wear the slipper to the ball (the f/g be faster than the carbon sibling)?

S.S.

Personal experience only, by no means scientific - a light ski (regardless of construction material) will always be quicker to reach speed X compared to a heavier ski. In choppy, messy conditions a lighter ski will be faster due to the fact that it has faster acceleration after each time that it is slowed by oncoming waves. The extra weight a fibreglass ski has may have a minor positive effect into chop, (newton's first law?) but more energy is required to regain speed X. What the paddler may feel in a heavier ski is the deceleration is slower giving the impression of better ski run.

Downwind, the difference is less (depending on the paddler of course) as long as you can maintain speed by good swell / wave selection. That said, if you are constantly trying to accelerate the ski onto runs then a light ski would be faster.

It is important to note too that identical shaped skis of different weights will sit lower or higher in the water. The wetted surface will change and therefore the friction will change. Also the ski will have been designed to sit in the water a certain depth with paddler of X weight. If a ski is designed initially to be 8kg with a 80kg paddler it will perform differently when constructed to 15kg with a 85kg paddler. It might be a rocket at its designed weight but a dog any other time.

Is 5kg going to make a difference to the performance of elite paddlers? They are still going to win. Here is a tip, always when training, put a couple of milk containers filled with water in the hull, about 4 litres. When it comes to race day, take out the bottles and there you have your super light weight ski at no extra cost.

I don't know how much transfers to ski's, but when I swim in the ocean I get thrashed by little guys that cannot keep up to me in the pool.
And it always seems like an acceleration thing.

There still seems to be some confusing regarding stifness verses weight...well to me anyway

As mentioned earlier a SA paddler has a carbon ski that weighs around 14kg, would this ski have the benefits of stifness for transfer of power yet ride better is sloppy conditions? and also have better long term robustness?

Speaking to a kayak builder on the weekend (K1,K2, river racers, etc), he suggested that sometimes a heavy boat can be that way from too much resign used and in fact end up being less robust than one that is vacuum infused properly?

(this site suggests that)

www.bladeoceancraft.com.au/html/infusion.html

I guess it's hard to know whether as in the case of this spec ski maker they have added more material to improve strength, stifness etc or whether it is just a dodgy build with too much resign, or are all the boat builders these days using this technology well so a heavier boat is indeed the result of more material?

In regards to weight, sometimes it has amazing effects and sometimes it means jack shitt.
In running shoes, the effect is quite incredible.

I conducted a series of trials with a woman I was coaching.
The trials consisted of 4 laps of a 400m track in trainers, then switching to racing flats, then back to trainers and repeat a few of times.
All laps were held at a very consistent 185bpm, which was close to her 10k race pace.

The laps run with racing flats were fully 13 seconds per lap faster.
This is over a normal trainer time of 1m:35s (?? bad memory, getting old, but somewhere in that ballpark.
But the 13s sticks in my memory.)

The difference in shoe weights were;

Trainer 310 grams
Racer 175 grams

The trainer also had quite a bit of motion control as she rolled in quite badly.
The racers were pretty much track shoes without metal spikes.
Track was grass.

This was running on a flat track, no hills, no accelerations except for the initial take off.

This for me, was a startling result at the time.

Please excuse my ignorance but I fail to see any connection between the different weight of running shoes and the different weights of materials used in surfski construction. Absolutely none of the variables are the same so you might as well compare materials used in aircraft design vs those used in submarines.

Excused.

Just saying that without getting out there and really finding the difference, there may be surprises lurking.

It may be very relevant to paddle weights for example.
Or it may not.

Everything in this thread so far has been conjecture.
Nobody has got out there and put numbers on it.

Thinking outside of the box and cross referencing many fields, leads to a better understanding, no matter what the subject.

Sometimes the greatest breakthroughs come from somebody that has a cross connection with another field that those in their own little world of reference simply never thought of.

It's a bit of a brainstorming type thing.
Take on whatever suggestion, no matter how non relevant it seems at the time and run with it and see where it goes.

All thought experiments cost nothing, but sometimes produce good results.

I seem to remember somewhere on this site, a news story or link where Oscar was comparing stiffness of different builds of skis, at the factory, by placing them between two stands and placing a weight and measuring deflection.

They didn't show the glass version, but said that they expected it to have less deflection......

Here's one of the articles:

Stiffness and Stability

Beat me too it Robin while I was messin around trying to cut & paste on my iPhone ! In that article you mentioned repeating that test for other boats.

Would be good to standardize things such as this in reviews for those that are listening. Would also be very keen to see how the mid priced and probably larger selling Kevlar hybrid boats compare for us mid packers.

As stated the stiffness can make a big difference to stability, but perhaps the stiffness/stability equation could be altered with a heavier carbon boat, as some SA boats I'm led to believe are built?

Would be good to see numbers on what lay-ups are sold by the manufacturers each year. I see a lot of composites and kevlars here in Western Australia amongst the midpackers, not so many glass or carbon.

Here's another mention - from Epic a while ago. No-one has taken this further.
Epic introduces measure of stiffness

I think the proportions of glass v carbon vary around the world - many more glass skis are sold here than overseas I believe.

From the article

"The ski in the photographs is an "Ultra" lay-up example i.e. the lightest in the range and therefore the ski that you'd expect to have the most flexible hull. The measurements were done with supports "about 5.5m apart" and with a 20kg weight in the cockpit. The deflection on this ski was 7mm. (The ski looks like a V10L; perhaps the V10 would flex less given the greater height of the foredeck?)

Oscar says that the Standard lay-up ski flexed 6.3mm and they expect the Economy ski to flex still less.



Isn't this the opposite to what is being assumed in this thread???

That's the article I remembered.

Like I said, most of this thread has been conjecture and speculation.
Lets put some real numbers on it!

Anyone care to put up a method that us at home can comparably measure flex in their boats and get some baselines established?

It can be simply done with a known distance between strong supports and something as simple cheap and common as a slide vernier.

jumping in late I have a differnt view as I paddled both recently and now have carbon - I call it the kick factor as I can kick my carbon ski down a lip but I couldnt do that on my fibre - is that to do with the tightness of the package ?

Red wrote:

Here is a tip, always when training, put a couple of milk containers filled with water in the hull, about 4 litres. When it comes to race day, take out the bottles and there you have your super light weight ski at no extra cost.

Love it, in my area I used to clear the weed from my rudder, now I just leave it too accumulate for some added drag(unless I'm trying to keep up with the big guns at training)

Could be onto something there as a training aid, a plastic cup towed behind a ski, much like a sea anchor!?

Or put a strap around the hull to stop the glide factor.

You can use a bungee cord (the ones with the hooks on either end you used to use to keep your school bag on your bicycle carrier) or for additional drag thread a tennis ball onto it.