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Some thoughts on Fantail's next sail...

  • 30 Sep 2016 07:41
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    Reply # 4283067 on 4282597
    Deleted user
    Arne Kverneland wrote:

    Camber to the People!

    Annie,

    I see the point that it can be a challenge for a beamy 26-footer to beat against an awkward head sea. Still, from the numbers I read about the Raven 26, that vessel should be able to stand up to  -  and would also need  - a quite powerful rig. Since Bryan is stuck with the short mast, I suggest he gives the lower panels a serious camber of at least 8% (better 10...) in the lower half of the sail, and also some in the upper section (almost flat in the top panel).

    The powerful sail will ask for a reef earlier than before, but that is just fine. As a panel is dropped, the CP of the sail moves downwards. That means the rig can produce more drive for less heeling moment.


    Having sailed a number of Owen Wooley designed Raven yachts, including an 8 day passage from Auckland to northern Tonga in a Raven 38 I do know that the Ravens are good sailing boats and will stand up to sail area, or drive. I don't know that having too much drive in a junk rig boat is a problem because one can get rid of sail very quickly. 
    Last modified: 30 Sep 2016 07:42 | Deleted user
  • 29 Sep 2016 22:48
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    Reply # 4282628 on 4278178
    Deleted user
    Split personality: L brain - Annie is right, more camber has disadvantages too, current sail is a good compromise, I should focus more on getting the sheets out of the cockpit on long gybes... R brain - itchy thumbs, must tinker!
  • 29 Sep 2016 22:27
    Quote
    Reply # 4282597 on 4278178
    Anonymous member (Administrator)

    Camber to the People!

    Annie,

    I see the point that it can be a challenge for a beamy 26-footer to beat against an awkward head sea. Still, from the numbers I read about the Raven 26, that vessel should be able to stand up to  -  and would also need  - a quite powerful rig. Since Bryan is stuck with the short mast, I suggest he gives the lower panels a serious camber of at least 8% (better 10...) in the lower half of the sail, and also some in the upper section (almost flat in the top panel).

    The powerful sail will ask for a reef earlier than before, but that is just fine. As a panel is dropped, the CP of the sail moves downwards. That means the rig can produce more drive for less heeling moment.

    My hunch is that my boats have shown the highest topspeed to windward when sailing under full steam, and with one panel reefed away.

    Arne

    PS: Sooo, I guess I am in the same “more camber league” as Paul, in his La Chica. In Stavanger there is, as you know, another heavy-weight schooner; the 23ton Samson. Despite having a SA/disp of just 13.4, she has proven to perform very well, with 10% camber in the foresail and 8 in the main. Many JRA visitors from abroad can verify her performance.
    Conclusion: Camber = Power!


    Last modified: 29 Sep 2016 22:32 | Anonymous member (Administrator)
  • 29 Sep 2016 21:38
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    Reply # 4282530 on 4278178
    Anonymous member
    I might add that it's a big ask to expect a boat that displaces less than 3 tons, to shove herself through a chop that has several hundred miles of fetch.  The E winds we've been getting in the summer in recent years, make it very difficult for small boats heading up and down the coast.  The shallow water, in some cases, extends well offshore; in other places there is considerable back wash from the cliffs.  Between the Hen and Chickens and the mainland coast there must be tidal eddies, because there are times when the sea state bears no resemblance to the wind that's blowing.

    I could be wrong, but I don't think making a more powerful sail is going to do anything apart from forcing Fantail to heel over further in these conditions.

    Last modified: 29 Sep 2016 21:39 | Anonymous member
  • 29 Sep 2016 21:00
    Quote
    Reply # 4282442 on 4278178
    Deleted user
    Most things (camber, yard angle, fanned vs. HM) seem to come down to a blue cheese argument: for some, there's no such thing as too much; for others, the smell resembles my son's week-old socks; others enjoy a slice on crackers with their beer.

    The classic arguments for and against having maximum camber aft are usually pitched in terms of magnitude and direction of vectors, duration of pressure recovery etc. etc. When I look at how well Fantail performs in light airs on port tack, with the foil shape distorted grotesquely by the mast, I can't help wonder if it makes any real difference. High AR, when suitable, seems to be the exception that provides both performance and handling improvements, provided there are no other constraints.

    I'm heading into the Alps for a few days and I'll chew it over (with my blue cheese).
  • 29 Sep 2016 20:40
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    Reply # 4282415 on 4281646
    Deleted user
    Eric Andlauer wrote:
    An other (new...) way to get more windward power could be to experiment some form of junkwing.

    Eric


    Eric, while I don't think a wingsail of some kind is practical for Fantail, if I had a daysailor I don't think I could resist having a dabble.
  • 29 Sep 2016 10:52
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    Reply # 4281646 on 4280833
    Anonymous member
    Bryan Tuffnell wrote:Thanks Arne and David 

    In a previous life I worked in aerodynamics and computational fluid dynamics; I had a well equipped, 400 square metre workshop to play in and I am a compulsive tinkerer. I'm waiting for issues to be resolved around the rebuild of my house post-earthquake and have time on my hands, and there's something compelling about trying something new... but I am very aware that experience counts for more than theory.

    An other (new...) way to get more windward power could be to experiment some form of junkwing.

    Eric


    Last modified: 29 Sep 2016 10:54 | Anonymous member
  • 29 Sep 2016 09:37
    Quote
    Reply # 4281571 on 4280833
    Anonymous member
    Bryan Tuffnell wrote:Thanks Arne and David

    I wonder what you both think of shortening the yard and truncating the top panel, leaving the upper edge of the top panel horizontal or nearly so. While the peak of the sail may provide some roll damping on a Bermudan rig I can't see much value in the cloth in the peak of the sail in our case, and retaining Fantail's current yard is appealing. 

    David, the foil shape is a something I'm not confident about at all, although it would be a good moot point over a beer and chips. I wrote a long reply as to why I was considering changing it, but deleted the response as both the explanation and justification was poor. In essence I was considering doing something about what I perceive to be Fantail 's greatest weakness - windward ability in chop, slop and swell. In writing it all down I feel less certain that I want to go down that path.    

    Shortening the yard? Yes!! I'm a total convert. I've never liked a long, heavy yard thrashing around aloft. I agree completely that the cloth in the peak of the sail is doing nothing useful, upwind, and can be put elsewhere in the sail with equal effect, downwind. With all the bermudan hotshot catamaran sailors going for "flat-top" mainsails, I have a feeling that having the upper edge of the top panel near-horizontal is how it ought to be.
    The only disadvantage with a short yard is getting trapped behind the topping lifts while hoisting, and that's very easily fixed with a lightweight extension - I'm using a 10mm diameter GRP rod to make the yard length up to the same length as the battens.

    Some possible ways to get more windward power:

    1. Higher AR - means a longer mast, and very likely not possible to design a sailplan with the CE in the right place with Fantail's current mast placement.
    2. Wider sail panels to be able to add more camber - moving away from the fanned shape, and towards the HM shape.
    3. Add batten hinges, to get more camber without having to have wide panels that are deeply cambered in themselves - my currently favoured solution, and compatible with the fantail sail shape. 
    Half a century ago, when I was racing an OK Dinghy, some of the guys reckoned that the maximum  camber should be at 50%. I don't think I agreed then, and I don't agree now, though hinges articulate more reliably the further aft of the mast they are. I do like to have the after half of the sail flat, as it keeps the weather helm more reasonable; but if I were trying to tweak Fantail's current sail for more windward performance, I'd be trying hinges in the lower battens placed at 30% and 60% of chord, so that the maximum camber was at 40- 45%.
  • 29 Sep 2016 09:03
    Quote
    Reply # 4281555 on 4280846
    Anonymous member
    Bryan Tuffnell wrote:
    David Tyler wrote:

    For some reason, which I have forgotten now, back in January I drew up a modified Fantail sail. It has a less aggressive yard angle, which should make it easier to set, with less loadings on the LHP and on the cloth in the throat area. It also has a straight leech in the sheeted panels, which should make for less snagging when reefed.

    Odyssey is basically polyester cloth, like "Dacron" sailcloth, but is very much more loosely woven and depends on its impregnation to keep it stable. Thus, it is still suitable for sails in which the bias stresses are low, but as we now know, not so suitable when the sail design is such that there are larger, cyclical/reversing bias stresses. I don't think I could recommend it for the above sail, even though those stresses would be less than in Fantail's current sail. I'd be looking around for a polyester cloth with as little filler as possible.

    Fantail's yard is now 'quite easy' to set - the forces are now much lower, and the sail hangs considerably more freely. Would you still prefer the lower yard angle?
    Higher yard angle: higher performance. Lower yard angle: easier handling. I think we each have to decide where on the spectrum we want to be.
  • 29 Sep 2016 01:21
    Quote
    Reply # 4281220 on 4280833
    Anonymous member
    Bryan Tuffnell wrote:Thanks Arne and DavidIn essence I was considering doing something about what I perceive to be Fantail 's greatest weakness - windward ability in chop, slop and swell. 
    You can only solve that issue with more power. So you can either increase the sail area or give the sail more camber. Fantails current sail only has 6% designed camber (how do I know? I designed the panels & made the drawings from which Annie assembled the sail).

    While some here may dispute it, I'm firmly of the opinion that that is not enough camber for a boat of Fantails type. I think 8% is the minimum and I'd prefer 9 or 10%

    A decent amount of camber is undoubtedly one of the reasons that LC sails so well and for the time being, she still is the boat to beat (here in NZ) when sailing to the windward in 5 to 15 kts.
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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