Flat, hinged or cambered?

  • 15 Mar 2015 02:30
    Reply # 3252606 on 461931
    Deleted user

    I'm wondering, what kind of keel does Zebedee have?

    Merged topic from TECHNICAL FORUM: 15 Aug 2018 20:49
  • 15 Mar 2015 01:55
    Reply # 3252584 on 3246820
    Paul Thompson wrote:

    Arne has pretty much spelt it out. LC has 12% in her foresail and 10% in her main. She is a heavy boat and needs all the drive that she can get.
    As for Annie's Fantail, if anything, she needs more camber not less.

    I'm not quite sure why you say she needs more camber.  Usually when we sail in company, Fantail keeps up pretty well considering her lack of waterline and the fact that she won't push through the waves like "LC" .  However else you would describe Fantail, she is not a heavy boat that needs all the drive she can get.  I wrote my comment in some haste as I had other things to do that day, and was not trying to convince Chris.  But as you have chosen to pick me up on it, I will enlarge on why I said it.  Fantail is designed to displace 2.5 tons, but when I've scraped back the antifouling I can see that she has probably never floated on her marks, so would reckon she is more like 2.75.  She has 1.25 tons of lead in a low ballast keel (she draws 5ft) and is very stiff.  (Indeed, it would be hard to find a more different boat from "LC".)  The main reason that I believe that there is too much camber in the sail, is from the way it behaves when I'm sailing on anything from a close reach to just about a beam reach, offshore.  Now you may say that my sailing could hardly be described as offshore, but once one is N of the Hauraki Gulf, there is nothing at all to the E apart from South America and when we have had continuous E winds, as we have this summer, quite a ground swell settles in.  In these conditions with the wind, as I say, somewhat forward of the beam (and over about F3) there is no way I can trim the sail so that it stays full.  As Fantail rolls back up the sail luffs, as she rolls away it fills.  If I over sheet in order to eliminate this, the boat then starts complaining with weather helm and is not happy.  I feel that a flatter sail would eliminate or at least reduce the problem. Most of the time, I am not sailing in this very narrow range of wind angle and strength with a specific sea condition and it's taken me well over three thousand miles of sailing to realise that this isn't because I'm doing something wrong.


    Chris's boat is much more like mine than either of the two full-keeled boats mentioned by Paul so I felt the comment was relevant.  I have a huge amount of respect for Arne, his abilities and his sails and would never dispute his findings or denigrate the sort of sailing he does.  It could well simply be a characteristic of my boat, but sailing in these conditions becomes frustrating and stressful with the sail constantly luffing and flattening.

    Zebedee and LC sail hard against each other every time they meet (which has been a few times this summer). Zebedee is faster downwind (which is as it should be as her LWL is longer

    Don't think so Paul ;-) The 30ft Tahiti ketch has a 27ft waterline and "LC" is two feet longer.  The 34ft dory has a 38ft waterline.  You must be pretty much the same!
    Last modified: 16 Mar 2015 00:23 | Anonymous member
  • 12 Mar 2015 23:18
    Reply # 3250685 on 461931

    I've given up on making new wingsail battens. To make such a big single wingsail was too much for me to do, with limited time, with limited facilities, and above all, with limited mental energy and waning physical powers, as I approach my eighth decade. I'm going to have to leave the topic to younger men. I want to go cruising again. If I try to make a wingsail again, it will be on a smaller boat.

    I've made new straight forward battens, and these will be hinged to the after battens in the way that I'd planned with the wingsail. Then I only have to cut off the starboard side of the sail at the luff line and refinish the luff. So I'll have put the clock back to the days before we all started playing with cambered panels. We didn't know how to make hinges with a large angle of articulation then. We do, now. My hinges will have an angle of articulation of 20 degrees each way, resulting in a camber of 8.5%.

    Ideally, I would add a small amount of camber to the part of the sail that is forward of the hinge, so as to get good curvature forward, while keeping the after part of the sail dead flat. Which is the way I prefer it; it's so much nicer to live with a flat sail. A flat sail doesn't go well to windward, so we need camber. Put that camber in the forward part of the sail, and we have the best of both worlds.


    Merged topic from TECHNICAL FORUM: 15 Aug 2018 20:49
  • 12 Mar 2015 21:55
    Reply # 3250595 on 3247321
    Asmat Khan wrote:

    Hi Arne,

    You are quite right: excessive heel can easily be reefed away. All the same, David Tyler has sailed under a variety of rigs and varying depths of camber, and has given his opinion that less is desirable in an offshore cruising boat. I lack his breadth of experience, so am reduced to dumbly following his advice. Perhaps he will come in and state his reasons for this belief.

    The reason I say this is not to do with making good speed to windward. Or rather, it is to do with the lack of necessity to make good speed to windward, when well offshore. Other things become more important. I dislike the way the after part of a well-cambered panel will empty, then fill with a bang, in a sloppy sea, for example. 

    In my fantail sail, I only put 6% camber into the lower panels. Yet I made the trip from NZ up to Alaska, which involves many windward miles, and is a trip that bermudan boats don't care to do very often. I had absolutely no difficulty, and never felt I was lacking in windward ability. 

    But if I had entered Tystie alongside La Chica and Zebedee in the Russell Tall Ships race, she would have been struggling to stay with them. Inshore, and when racing, throw in all the camber you want. Offshore, I'll stick to my belief that it's better to stay at the middle of the spectrum - not too flat, not too full. Moderation in all things.

    Certainly Zebedee has sailed offshore with his cambered sails. La Chica has not, yet. Anthony Swanston, Wild Fox, and Paul Fay, Ti Gitu, both had trouble in getting cambered sails tame enough for relaxed offshore sailing.

  • 11 Mar 2015 20:48
    Reply # 3247807 on 461931
    Anonymous member (Administrator)

    Good, Asmat

    I bet the rise in performance when going from flat sail to 6% camber is bigger than ‘the next jump’ would be  -  from 6% camber to 8 or 10% camber. I think the 2-sail junk will perform better than a 4-5sail gaff cutter or ketch will do.

    You mention Hong Kong parrels. They have nothing to do with batten stagger when the sail is being reefed, only with the set of each panel when hoisted. The parrels you plan to use  -  maybe combined with Slieve’s very clever combined battenparrel/downhaul will probably make the Hong Kong parrels redundant.

    Chers,
    Arne

     

     

    Merged topic from TECHNICAL FORUM: 15 Aug 2018 20:49
  • 11 Mar 2015 17:32
    Reply # 3247321 on 461931

    Hi Arne,

    You are quite right: excessive heel can easily be reefed away. All the same, David Tyler has sailed under a variety of rigs and varying depths of camber, and has given his opinion that less is desirable in an offshore cruising boat. I lack his breadth of experience, so am reduced to dumbly following his advice. Perhaps he will come in and state his reasons for this belief.

    With 6% camber, I do not expect to be exempt from the curse of positive batten stagger, although I am hoping to be able to do away with Hong Kong parrels. I plan to achieve this by use of the yard hauling and throat hauling parrels, perhaps with a Columbie egg thrown into the mix: (the combined downhaul/batten parrels Slieve is using in Poppy).

    My Branwen is a Wylo 32, steel hulled gaff cutter designed by Nick Skeates. If you don't know the design, think Land Rover, not Jaguar. 9.7m LOA, 8.5m LWL. Designed displacement is 6.25t, although mine is rather overweight and probably displaces 8.5t in cruising trim. My junk sails will have the same area as her present rig, 61.5 sq m with everything set - main, staysail, jib, main topsail and jib topsail. Without the party frocks, she is badly under canvassed below F4. 

    Cheers, Asmat

    PS My sails were designed by you, based on the master sail drawings in your excellent   Public Domain files.Thank you.

    Last modified: 11 Mar 2015 17:35 | Anonymous member
    Merged topic from TECHNICAL FORUM: 15 Aug 2018 20:49
  • 11 Mar 2015 11:56
    Reply # 3247071 on 461931
    Anonymous member (Administrator)

    Asmat,

    I can see the point in keeping your boat reasonably upright, but remember two things:

    • 1.      The photos you have seen of La Chica have most probably been taken when she was racing. Who worries about the cook’s wellbeing while racing?

    • 2.      The point with using sufficient camber is to avoid being underpowered when the wind drops to F4 and below. This means you will be sailing more and motoring less. You may still decide for a maximum heel of, say 20°, but that can easily be achieved by reefing.

    Arne

    PS: What it the displacement and length of your boat

     

    Merged topic from TECHNICAL FORUM: 15 Aug 2018 20:49
  • 11 Mar 2015 10:23
    Reply # 3247022 on 461931

    I have briefly owned a junk rigged Tahitiana, (Irena), that had circumnavigated under her flat sails designed by the late Jock McLeod. She was a fine sea boat: very stiff, I never came near to putting her rail under, but woefully lacking in power to windward. Had she not succumbed to rust, I would certainly have given her a cambered rig.

    Looking at photos of La Chica and other boats that have been given deeply cambered sails, it is striking that they seem to sail fast, at angles of heel that would bring forth dark mutterings from my cook. My Branwen is a shoal draught centreboarder, admirably stiff, but I still feel that 6% might be as much camber as she wants. I am not interested in making speed to windward; all I ask is that she will tack confidently and bring us home safely and in comfort.

    Cheers, Asmat

    Merged topic from TECHNICAL FORUM: 15 Aug 2018 20:49
  • 11 Mar 2015 00:50
    Reply # 3246820 on 461931

    Arne has pretty much spelt it out. LC has 12% in her foresail and 10% in her main. She is a heavy boat and needs all the drive that she can get. I don't think she has to much camber at all. Indeed I suspect that I could go to 14% in the foresail but unless I could somehow increase the separation between the two sails, 10% is as much as the main can handle (foresail back winds the main).

    Zebedee and LC sail hard against each other every time they meet (which has been a few times this summer). Zebedee is faster downwind (which is as it should be as her LWL is longer and she is lighter) but LC is faster to the windward. We have not really worked out why that is but we are coming to the conclusion that it could be that LC's in sails the shape is much more controlled. She has a carefully profiled entry that gives the desired 8 deg entry angle and by using the shelf foot method of construction the sail shape is more controlled. Also her sails are built using traditional sail making techniques and so distort less than those built using Arne's simple methods. That is not to degenerate Arne's methods which are great (I use method 'B' to join the panels and create the batten pockets) but they are lightly built and there is a price to pay. Of cause there is a price to pay when you build sails my way as well... that is time. Instead of just taking a week or so, LC's sails took three weeks of 8 hour days.

    As for Annie's Fantail, if anything, she needs more camber not less.

    Merged topic from TECHNICAL FORUM: 15 Aug 2018 20:49
  • 10 Mar 2015 17:46
    Reply # 3246490 on 461931

    I must confess I am blown this way and that by all the conflicting advice on camber that has appeared here. Little wonder that I have timidly chosen a moderate approach for my Wylo, in which I hope to venture far offshore. I am almost persuaded by Kurt Ulmer's argument in favour of flat sails, but had 8% camber on my last conversion, a kingfisher 26 and was very pleased with her performance, which was equal to that under her old Bermudan rig.

    It was David Tyler who suggested here a while back, that 6% would be the right depth of camber for an offshore cruiser. He has sailed more miles than most of us, so I listen carefully to his views. I also find your argument in favour of more depth of camber convincing, Arne; if you go to the trouble of putting camber in your sails, you may as well go all the way and have as much camber as is necessary for a heavy boat.

    I hope to be stepping masts next month, so we shall see how things turn out this season.

    Cheers, Asmat

    Merged topic from TECHNICAL FORUM: 15 Aug 2018 20:49
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