At the considerable risk of getting serious for a moment
:
Being a born sceptic, I have always been wondering if sooooo much twist in some of the race sails is really an advantage, and why it seems to work in some situations, for all the reasons mentioned here and more. Just because something gets popular doesn't not mean it is 'truth'. and there is often no ONE 'truth' anyhow. (This applies to a lot of things that are not a well studied and well defined science - and windsurfing sails certainly fall into that bucket).
First problem is to define' advantage'.
The core of that problem is that there are an abundance of use cases - legitimate uses that are very
different. Was is the advantage to YOU?
Be careful what you choose. How do you want to fly?
I will just give one example that has always kept the above scepticism ticking over for me.
In the early 80's, I saw a little old man wandering down the spit at Sandy Point holding a a very tall pole. Every now and than he would stop and hold it vertically and consult some gauge in his other hand. He would drop the pole down and write down some numbers.
My curiosity naturally fully aroused, I asked him what he was studying. He replied that we was designing a sail, and was trying to determine the twist (washout) required tomatchwith the wind velocity gradient. (or words to that effect).
The man turned out to be Lindsay Cunningham, one of my childhood idols, on account of him designing many of the sailing cats that I grew up lusting after (and later in my teens, had the privilege to sail some
). He was of course, designing Yellow Pages, Endevour, which went of to hold the Outright World Speed Sailing 500m World Record, for many, many years.
That wing sail didn't have a great deal of twist! neither did the later, lower aspect wing he later designed for Macquarrie Innovation, which I also had the privilege of watchingdoingmany runs (and have a few interesting incidents!
) on the Sandy Point Speed Strip.
So when people say, "Oh, we have twist in the windsurfing race sails to compensate for the wind gradient" I say BS! There is no way that stacks up. It's not just this example that shows this, just look at all the high speed watercraft like the AC and sailGP foilers! None have more than low teens degrees twist, many have less.
It must be for different reasons.
And therein lies the conundrum. There are
lots of theories (I have a few myself ) for so much twist in some windsurfing sails, but I still have not seen any really compelling explanation of any of those theories backed up with any
actual hard data. There is
no doubt that many sails with a great deal of twist
do 'work' in th e situation's they are specifically designed and tested for. But there is not of lot of clear explanations about
how and why they work, and what situations exactly that applies too. No really well backed up data to explain and define what degree of twist works where, and for who, in what situations. Most of us recreational sailors are flying blind in that respect. It's back to trail and error, to find out what works for us in our situations. Sure, we can see what is working for our peers, and especially
champions in various aspects of our sport in what situations and disciplines, but do we mere mortals
really sail in the same situations and in the same way as those
champions? (check your ego here!
)
Ludwig Prandtl's Theories and studies come closest to what I have found. Papers on the subject abound on the WWW, but very, very few directly mention, or seem to directly apply to windsurfing Slalom/Race sails.
If you find any, please share them.
All I can suggest, is to keep experimenting with sail models, shapes and settings to see what actually works for you in your particular situation. Seek advice and wisdom, and respect it, but don't abandon scepticism, and certainly not curiosity.
Oh, and sail to put a smile on your dial. Thats the only really meaningful measure of things.
