Quite interesting sails on the foiling 18foot skiff in Switzerland. Mainsail have a top raked upwards and the spi have a very straight luff. For a boat building a lot of virtual wind and not going too deep, the spi seems like a very good design to me. The mainsail is a somewhat different beast. I dont think they get too much draft in the top with the heavy battens needed to support the top and leech, but drag might be less than with a conventional square top. Probably not something dramatic, but a small incremental gain perhaps. I have not studied the sail measurement rules yet. Would you gain "free" area by doing such a design, or will the measurement rules catch this?
Cool to see "new" developments! Who will do the first F-16 trials <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
I don't think it would take much to adapt their dagger board(s) and rudder(s) to a cat (move the pintles?) and that sail might even slide up our mast, then have a go at it.
I wish my neighbor had one of these, I'd be at his house begging him to try it on my boat!
It was actually a major mistake. I was currently leading the first race of last years F16 Nations Cup. I had quite a good lead maybe 6 boat lengths with Scooby in second place. This photo was taken on what should have been the last downwind leg. I had just completed a gybe but in the process accidentally released the tackline cleat and as you can see the kite just took off. When I tried to pull the kite down the boat started to gybe and the next second I was swimming. As I stood on the hull preparing to get the boat back up Scooby sailed past with a huge grin on his face, he should have sailed for the finish but was probably so happy to see me go over that he went around the leeward mark and back up the beat. I sailed off towards the finish line and missed the pin end, If I hadn't I would have won the race. If you're wondering why I missed the pin end the Committee boat had forgotten to put up the finishing flag!! Needless to say I subsequently checked the rules and apparently the finishing flag is put up out of courtesy and only means that the Committee boat is on station at the finish area. It's the number of laps which determines the duration and finishing of a race. It is quite common for the F16 Circus to get the number of laps wrong during the Nations Cup, the previous year we all sailed 5 laps instead of 4 during the Medal Race <img src="http://www.catsailor.com/forums/images/graemlins/confused.gif" alt="" />
MP*MULTIHULLS
Re: Development sailshapes
[Re: Mark P]
#128725 01/14/0809:49 AM01/14/0809:49 AM
I just thought I'd post this picture of my high flying kite experiment again!! For some reason it has never taken off.
How many other masts could have taken that abuse ?
Mainsail is almost out as far as it can go, Kite is flying and the mast did not break!
Quote
It was actually a major mistake. I was currently leading the first race of last years F16 Nations Cup. I had quite a good lead maybe 6 boat lengths with Scooby in second place. This photo was taken on what should have been the last downwind leg. I had just completed a gybe but in the process accidentally released the tackline cleat and as you can see the kite just took off. When I tried to pull the kite down the boat started to gybe and the next second I was swimming. As I stood on the hull preparing to get the boat back up Scooby sailed past with a huge grin on his face, he should have sailed for the finish but was probably so happy to see me go over that he went around the leeward mark and back up the beat. I sailed off towards the finish line and missed the pin end, If I hadn't I would have won the race. If you're wondering why I missed the pin end the Committee boat had forgotten to put up the finishing flag!! Needless to say I subsequently checked the rules and apparently the finishing flag is put up out of courtesy and only means that the Committee boat is on station at the finish area. It's the number of laps which determines the duration and finishing of a race. It is quite common for the F16 Circus to get the number of laps wrong during the Nations Cup, the previous year we all sailed 5 laps instead of 4 during the Medal Race <img src="http://www.catsailor.com/forums/images/graemlins/confused.gif" alt="" />
I've always had a crew to count the laps for me!
It was a mad days sailing. I myself, did not go swimming, but I did manage to sail over the Spi Sheets twice, Put the bows in as far as the gooseneck taking the kite down and one other "full poswer" nose dive then I got the front of the pole in the water.
The windurfers have lead the way here. They went to the extreme a while a go and most of the latest shapes have gone back to just a mild undercut in the leach.
For us currently, I was informed by some of the sail measurers, that there is a penalty in measured sail area vs. actual when measuring a sail with a reverse leach.
Windurfers for all intensive purposes do not adjust downhaul, outhaul, or "sheet" tension. While I am sure it is very debatable, I was told that when this style top was experiment with on the A class sails, there was signifcant added drag and they were not nearly as fast. An interesting note would be also to see that even with 0 or positive roach the trend to have realy large heads on cats has moderated.
M
Re: Development sailshapes
[Re: Matt M]
#128729 01/15/0804:10 AM01/15/0804:10 AM
Yes the windsurfers have gone away from big heads on there sails but they also have the advantage of having a number of sail sizes to pick from, rather than have a great big draggy head on the sail, it far easier to fit a smaller more efficient sail.
We then are at a disadvantage as we generally only have one sail to pick from, in my view a slightly too big a sail for the solo sailors and about right for the two handers.
Now speaking as a single hander it would be great to have some sort of automatic feathering in the top of the sail to compensate the gusts, has it been sucessfully done, I'm not sure yet but it would be nice to think that it could be done as it would certainly make things easier.
Yes the windsurfers have gone away from big heads on there sails but they also have the advantage of having a number of sail sizes to pick from, rather than have a great big draggy head on the sail, it far easier to fit a smaller more efficient sail.
We then are at a disadvantage as we generally only have one sail to pick from, in my view a slightly too big a sail for the solo sailors and about right for the two handers.
Now speaking as a single hander it would be great to have some sort of automatic feathering in the top of the sail to compensate the gusts, has it been sucessfully done, I'm not sure yet but it would be nice to think that it could be done as it would certainly make things easier.
Tapered and / or carefully constructed masts can do this.
Problem is that you then have a mast tuned to your crew weight as if it has the right flex for a 10 stone bloke, it will not have enough power for a 15 stone bloke.
Fathead sails can also have a measure of gust response depending on how stiff the battens are.
“Windsurfers for all intensive purposes do not adjust downhaul, outhaul, or "sheet" tension.”
That statement without “conditions” is totally false…granted the typical experienced windsurfer does not adjust downhaul, outhaul, or “sheet tension on the fly” (some racers do) …but downhaul/outhaul/batten/camber tension is very finely tuned “on the beach”
We accentually pick a sail size and fix the sail shape to be optimized for a given range of wind conditions. If the sustained conditions change radically (say10 mph+ over optimal, for example the wind increases from 20 mph to 30 mph) and the sail starts to get uncomfortable, we sail into the beach, or drop the rig (while still out on the water) and make the necessary small adjustments (a ½” of change on downhaul or outhaul makes a huge difference in a high end windsurfer sail..
A windsurfing rig is much more like a fixed wing than a catamaran rig.
Regards, Bob
Last edited by Seeker; 01/15/0801:32 PM.
Re: Development sailshapes
[Re: Seeker]
#128732 01/16/0810:56 AM01/16/0810:56 AM
OK then its acknowledged by some that windsurfing sails maybe better aerodynamically than Cat sails, has anybody built and tested a windsurfing style sail for a cat, ie mast within the luff and the classic wishbone boom with a portion of the sail below the boom ? or perhaps classic windsurfing shape with standard baulk rope to rotating mast. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />
And how about a mast that leans into the wind for lift, like a windsurfer, we could jump waves! There were some monohulls that were playing with that idea, the big 60-70 foot, round the world boats.
Blade F16 #777
Re: Development sailshapes
[Re: Timbo]
#128734 01/16/0804:19 PM01/16/0804:19 PM
I think the misconception that windsurfers don`t adjust their sails while sailing is similar to observing a weekend Hobie 16 /Dart 18 sailor who is not racing, and claim the same thing. He will set downhaul etc on the beach and just go sailing, if conditions change, he`ll come into the beach, add downhaul and go out again. When racing windsurfers such as the Formula class or Longboard class, which are both raced windward/leeward courses, the sailors adjust outhaul while sailing, and in the Mistral class (the previous Olympic board) the sailors had 36:1 downhaul adjustable from the boom. Most modern windsurf rigs don`t require adjustable downhauls as the manufacturers have optimised the twist in the sail set at the optimal downhaul setting, which is printed on the sail. By dropping the outhaul at the weather mark, the sailor gets more power low down where it`s needed, and increases the twist in the leech, also good for downwind speed. Anyone who does not acknowledge that windsurfer sails are far more aerodynamically superior to cat sails has clearly not seen the sails developed for racing, with wide luff sleeves and camber inducers. But that`s not saying these types of sails would work on a catamaran - they probably wouldn`t you would need to build a lot less twist into the sail for starters. Check out the attached pic if you disagree..
Anyone who does not acknowledge that windsurfer sails are far more aerodynamically superior to cat sails has clearly not seen the sails developed for racing
I'm just as sceptical about anybody who claims that surf rigs are far superior to cat rigs.
I don't believe you can make such a judgement either way.
Wouter
Wouter Hijink Formula 16 NED 243 (one-off; homebuild) The Netherlands
Windurfer's & their rigs are a completely different scenario to a catamaran & its rig.
1. Massive power to weight differences
2. Massive wetted surface area differences
A windsurfer rig relies on the rigg & sail "springing" with every gust, but the catamarans ( even the lighter designs) need leech pressure & stiff mast sections to harness the energy.
Rolf,
That spinnaker design on the skiff may not work for F16 as the ISAF half measurement still needs to be 75% of the foot & hence you would have a rather large roach on the leech of the kite.?
Marcus
Marcus Towell
Formula Catamarans Aust Pty Ltd
Re: Development sailshapes
[Re: Marcus F16]
#128738 01/17/0809:34 AM01/17/0809:34 AM
Hi Marcus, I agree with you, which is why I said that windsurf type rigs wouldn`t work on a cat. My real point was to clear up the misconception that windsurfers don`t adjust sails while sailing, for sure the majority of recreational windsurfers don`t but at a racing level things are different. I think a compromise beween the two would be ideal, we see squaretop sails and tapered masts in cats, the aim of which is to let the top twist off and reduce power high up in gusts, resulting in an icrease in speed with a reduction in power where you don`t want it.
Wouter, what I meant is that windsurf racing sails have a much better aerodynamic profile than a standard catamaran sail, in section. Similar to the difference between a modern paraglider wing (double surface) vs. an older single-skin hang-glider wing section. Have a look at the new Neil Pryde RS Racing sails, or Naish Stealth sails - they have camber inducers and very wide luff sleeves which increase the aerodynamic efficiency of the sail considerably vs. a non-cambered sail with narrow luff sleeve. Of course the modern wing-profile mast you have on the Taipan rig goes a long way to narrowing out the difference and is probably not much less efficient than a windsurf race sail profile.
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