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      Abbreviated rules   07/28/2017

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teamvmg

nacra17 upwind with kite!

16 posts in this topic

I could do that 40 odd years ago on a monohull that had a tiny triangular pole kite - that's completely triangular - it was sailed with tension on the luff. However tacking was a bit more of a problem than it is in the video.

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It was done on the Tornados and I've done it on the F18! Does it pay? Very rarely as the angle is usually 5 degrees lower if not more and if you do get hit with a puff you end up having to drive deep so gains are minimal. I did have one spinnaker that was particularly flat and worked very well for this, where I suffered 0-5 degrees in heading in 5 kts or less of pressure but picked up a good bit in velocity. Trouble is the kite was too flat for good downwind work. That issue is mitigated when foiling. its certainly going to be an interesting tactical game as I suspect the crossover velocity is going to see some flying kites upwind while others don't.

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That's why the original code zero spins were developed in monohulls...they were a cheaters sail (funny how that fact doesn't keep lots of folks from wanting one).  The rules then allowed any number of spins but limited headsail count.  So someone decided to carry a flat spin (the rules then was the SMG must be 80% of foot to be called a spin).  So they just made a spin with a "flap" that would fold over heading upwind...voila, another light air genoa. 

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4 hours ago, samc99us said:

It was done on the Tornados and I've done it on the F18! Does it pay? Very rarely as the angle is usually 5 degrees lower if not more and if you do get hit with a puff you end up having to drive deep so gains are minimal. I did have one spinnaker that was particularly flat and worked very well for this, where I suffered 0-5 degrees in heading in 5 kts or less of pressure but picked up a good bit in velocity. Trouble is the kite was too flat for good downwind work. That issue is mitigated when foiling. its certainly going to be an interesting tactical game as I suspect the crossover velocity is going to see some flying kites upwind while others don't.

It pays up until 6-7 knots. Watching the racing and an interview with Darren Bundock, it seems everybody has to do it in those light conditions and that you can point as high with these kites as without. Maybe this shouldn't be surprising, because if the kites were any fuller, they wouldn't work downwind at some of the speeds that will be achieved when foiling. The interesting comment from Bundy was that everything gets super loaded. He seemed to suggest this is going to push crews to the limit and I wonder whether we will see more male crew and female helms because of the strength issue. He also seemed a bit concerned about the loads it was putting on the boat and whether the kites will last. He said the basic technique is to strap the kite in as tight as possible and steer to it. I wonder how many light wind races you can do that before the kite is shot.

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I watched the Bundy interview, very good take on the situation. Me personally, I'm not nearly as concerned as Bundy appeared with the loads. Why? Because I've double trap reached with the kite up for thousands of miles on Nacra built beach cats, everything fully whaled on in 15 kts+ of breeze. The beams on the 17's are stronger because of the foiling loads than anything Nacra has built in the past. The mast is plenty tough and can take it. The hulls have been substantially beefed up to take the foiling loads so again they can handle carrying the kite upwind. Only issue may be the competitive life of the hulls carrying that much tension load upwind, but since they switched to an all carbon build on the new boats I don't think that is a major issue.

The kites, well they are surprisingly resilient. I typically sail with a kite that is 4 years old at club level races and it has rarely been the source of speed deficits (I have new kites I use at major events). Nacra are using polyester kites on the 17 Mk. 2's. The downside with these is that they hold their shape until they don't and then just pop, supposedly anyway. There are also a bit harder to trim and since the sail is stiffer the loads are higher. I've always thought it makes more sense for the women to be driving and the men crewing as all the hard work is at the front of the boat. The women proved us wrong last go around but now with the upwind spinnaker work that may change the situation.

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Sam

I am not so concerned about the boats being able to take the loads as i am about the kites and crew taking the load. Bundy has been sailing with one of the strongest girls in the fleet (Lisa is awesome) and he still thinks there might be a load issue. As you point out, this could see a switch in who does what. As for the kite, I have been repeatedly told by coaches and sailmakers alike that a kite is never faster than the day you put it up for the first time and that from there the performance drops. It might only be a small amount to start with, but you will always be better with a new kite than a used one. One reason that the degradation of kites isn't as noticeable as, say, jibs is because you sail with them in an eased, fuller state If they are pulling the hell out of the kite to get it flat enough upwind, that changes. the kite might still be good downwind but a little change will probably have a more noticeable impact upwind. I would be very surprised if a light wind regatta doesn't have a significant impact on kite life. I should add that I am not complaining about that. It is just a fact but in the overall cost of a campaign, it might not be such a big item. How much does a proper full time  campaign cost per year? Boat, travel, living expenses, coaching etc? A few more kites isn't going to make a big dent.

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The reality is that they are not really spinnakers... They are light weather genoas. So no surprises. And compared to the small jib, the area is at least triple with more fullness, so using the same mechanical (dis)advantage as for a jib, the loads have to be pretty high for a crew.

Many "indigenous" Australian skiff/ dinghy classes long ago had absolutely flat triangular spinnakers with wire luffs, including Gwen 12s and Lightweight Sharpies. And the Gwen 12 (designed by Charlie Cunningham BTW) when gybing and tacking involved throwing the mast end of the pole up and forward whilst you turned the boat under it and picked up the pole on the other side. Been there and done it......

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anyone has any questions, lemme know.  Pertinent interviews: 1 with Jason, 1 with Bundy, 1 with 2nd place and first girl Lin Cenholt (OMG) who talks about the kite upwind, 1 swimming video, more at facebook.com/nacra17sailing

 

 

 

 

 

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58 minutes ago, Legion of Modernrate Jack said:

Lin had already figured sheet loads may be a factor!

Lin-5-225x300.jpg

She's a helm though!

 

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ACS, nothing to argue with there, kites are a fresh item before every major regatta. Campaign costs are well into the 6 figure range per year for the top teams-at least 2 boats, splitting time between Europe and home, full time coach, all the travel time.

1) Whats the foil repair/replacement plan since the first batch has some issues (per your interview)?

2) What do the sailors estimate for a competitive life of the platform at this stage?

3) How many boats are on order, when can the ordinary person buy one, and what does the event schedule look like?

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SMG The foiling Nacra 17 is not the first cat using their particular flat looking "spinnaker" for upwind sailing in light air. So do the M27 and D35 on the swiss lakes, the GC32 and the AC45. I believe the Xtreme 40s tried but dropped it as not working too well. Difference to the Nacra spi is that those are all some kind of 3DI and on a furler. And they are all one design so don't care about how they fit into rating systems. That applies also for the Nacra 17 as an olympic class, yet we might see those boats/crews outside the olympic circle compete in open class events under texelrating (TR). I am not up to date with the latest iterations but in the past TR referred to ISAF regulations and required 75% SMG to count as a spinnaker. I am really curious what the SMG is on the Nacra 17 or GC32? Or in general what SMG is required to be able to use a sail as such for sailing upwind in light airs? And what damage would it do to your rating under TR or OMR (offshore multihull rule)? Obviously those sails seem to make sense on foiling boats, yet the non foiling M27 and D35 (which again just won the Bol d'Or) seem to use those large sails as their only downwind wardrobe as well... Is it time for ISAF/world sailing to rethink their definitions?

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SCHRS handles this to some extent: http://www.schrs.com/rules.php

They are saying if the sail can be used upwind it is to be treated as a jib. Not sure how TR stacks up, I know SCHRS and Texel have been doing some work together.

The issue is within class rules there are also area limits. When stuck with a max area, I don't think the super flat kites pay off across the range of conditions! Certainly if you had the option to carry two kites, I could see a very large code zero esque kite and then a smaller, more conventional but possibly even a bit under sized kite for breeze on work paying off in distance races, depending again on the rating hit and the ease of sail handling.

What is going to be fun on the N17 is the crossover points...

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If you download the latest SCHR calculator, you now have to fill in what percentage of the mid girth is, if its less than 75%. Up to about 70% its not too punitive, beyond that it gets into a real world of handicap pain as it treats it as a jib.

The mono boys eventually ended up with a flap of sail at the mid point which measured in at 75% but simply folded back when in use.

I've often wondered whether a double flap that self fills creating a wing shape on the leading edge such as the latest kite canopies, may just measure in, but once inflated would stop this whole front edge collapse we all seem to be getting as soon as the speed build up.

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