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Cambered panel sails on Ti Gitu

  • 30 Aug 2012 23:24
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    Reply # 1061021 on 1057117
    Deleted user
    Brian Kerslake wrote:Just a note to say that Paul Fay has written a long, detailed, illustrated article about his further experiences with his cambered panel sails, and that this will appear in the next Magazine (October). Paul ends the article by saying, "It has taken us 12000 miles and two Atlantic crossings to really begin to understand these sails....."
    Members can now find Paul's new article (see above) in Technical Articles as a plain text file and as low and medium resolution PDFs. His original article describing his ideas on and research for Ti Gitu's new cambered panel sails can be found there too. (Non-members will need to join in order to be able to access this.)

    And yes, David Thatcher's final sentence in the post above this one is worth keeping in mind - flat or cambered, both a vast improvement on other cruising rigs.
    Last modified: 30 Aug 2012 23:27 | Deleted user
  • 27 Aug 2012 07:05
    Quote
    Reply # 1057407 on 766440
    Deleted user

    An interesting discussion and one that has motivated me to make comment. I feel that I am still some way from really being finished with the sail conversion on Footprints from a flat sail to a cambered sail. Certainly the new cambered sail has added some complication over the previous flat sail but I feel that there have certainly been some performance gains. I have noticed too that Footprints is a much more responsive boat and tacks a lot more readily. It has been a big job this conversion because not only have we built the new sail but I have a complete set of new battens and a new yard. The sail is a lot lighter than the previous sail but that is a result of sail cloth and considerably lighter battens and yard. But I have now often gone out sailing by myself which is a thing that I hardly ever did with the old sail. In short Footprints now has a modernised rig complete with carbon battens and updated bearing blocks.

    The next job is to rake the mast forward by about 2 degrees which will give gains in sail setting and get the center of effort further forward. Although the mast on Footprints should be vertical it does in fact lean slightly aft which may be to do with the trim of the boat. I agree with David Tylers comments that 6 percent camber my be a little too much for offshore work but that is what we have got and I think the fact that David has successfully made a single handed winter passage from New Zealand to Tahiti with his 59 sq m sail is a good testament to the success of the rig.

    I am looking forward to our coming summer when we plan on doing a lot of sailing so I will have a better idea of the success of the rig after that. And we are planning an offshore trip next year so there is a lot to look forward to. Yes the old flat sail was easy, I could basically hoist it and then forget about it, the new sail is more twitchy but if it provides am nmore satisfying sailing experience then I am all for it. Being a past bermudan sailor let us not forget that any kind of junk rig is going to be a lot easier to deal with than the complication of headsails and spinnakers and all that other stuff on a bermudan rigged boat. 
  • 27 Aug 2012 04:40
    Quote
    Reply # 1057348 on 766440
    Anonymous member
    Having sailed Arion with both a flat sail and a 4% cambered one, I am of the opinion that the cambered sail offers my vessel significant advantages in only one scenario, light windward work in smooth seas.  In those conditions the flat sail was inefficient, I could only sail about 70 degrees to the wind and tacking was slow.  The cambered sail allows Arion to sail in these conditions as well as the bermudian main and jib did.  Once the wind freshens to 12 - 15 knots, the performance of the flat sail in sheltered waters is acceptable if not scintillating.  Once the wind is above 15 knots the flat sail is as lively a performer as needed.  In the open sea in fresh conditions, where tubby little Arion needs to sail a bit free, the cambered sail holds no advantages.  For the inshore and coastal work I am currently doing, I think the cambered sail is worth persevering with, once I have sorted out structural and furling issues, since I tend to do a lot of close manouvering in light weather and sheltered water.  I will need to sail Arion for a season or two before forming an opinion as to whether I'd use a cambered sail for offshore work but I must admit to some nostalgia for the simplicity and ruggedness of flat sails.
  • 27 Aug 2012 02:34
    Quote
    Reply # 1057261 on 766440
    Anonymous member
    Thanks to Paul and Mo.

    I'm very glad we'll hear more from Ti Gitu's experience, especially since there are now quite a few boats who've expressed frustrations with aspects of their cambered sails.

    I've been a bit vocal about the innate advantages of flat-cut sails, but even I will rejoice while people solve their wrinkles and worse, and get the best possible benefit from their rigs.

    For anyone who would just as soon sail both as well and as poorly as mehitabel does, I promised David Tyler I'd write a little article on the why and how of sails without added camber. Soon. (In actual fact, I don't think we've gotten the best out of mehitabel's rig yet.)

    On the same topic, with regard to the enthusiasm to re-create 'Practical Junk Rig' for modern times, I think it could wait a while. Until Hasler & McLeod's rigor and proven scantlings can be matched - for the new sail patterns, in the open ocean.

    Cheers,
    Kurt
  • 26 Aug 2012 23:11
    Quote
    Reply # 1057117 on 766440
    Deleted user
    Just a note to say that Paul Fay has written a long, detailed, illustrated article about his further experiences with his cambered panel sails, and that this will appear in the next Magazine (October). Paul ends the article by saying, "It has taken us 12000 miles and two Atlantic crossings to really begin to understand these sails, and had we known what we were letting ourselves in for then we would certainly have stayed with flat sails. Now that we have begun to overcome the disadvantages we are having second thoughts, and perhaps in another few thousand miles we may even begin to like them!" (The exclamation mark is mine.) I hope to upload the article to the website soon.
    Last modified: 26 Aug 2012 23:13 | Deleted user
  • 17 Dec 2011 08:30
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    Reply # 775978 on 766440
    Anonymous member
    I applaud all efforts to get better performance from the junk rig.

    But flat junk sails are innately tougher, and never flog. Ti Gitu's experience doesn't inspire me to want camber in our panels, just for a little better climb into a 10-knot breeze.

    When we were beating home in such a breeze the other day, I didn't feel a need for better anything. Hove-to in a gale with a few flat panels up, same. Close-reaching, as close as I'd ever want to go, in good strong tradewinds, likewise. 

    About schooners, (and ketches) I'd add that since the centres of effort of two sails are further inboard than that of a single sail that would drive the same boat, and the masts and sheets are twisting the boat at different points far apart, she balances better. Less tendency to yaw. Besides that, it's so easy to take in reefs for balance. I like our schooner.

    Cheers,
    Kurt
    Last modified: 17 Dec 2011 08:50 | Anonymous member
  • 14 Dec 2011 16:48
    Quote
    Reply # 773267 on 766440
    Deleted user
    Regarding the previous posting, give me a two-masted rig any time. At my age I wouldn't like to be messing around with a single sail on a 39 foot boat. Regret I didn't really understand the comment about the 'shape' being better on a two-master. The point about a two masted rig is surely that the boat can be kept balanced by reefing each sail differently if you need to?

    As to cambered sails tending to bend things more than flat panels, I can vouch for that. On our previous flat-panelled junk schooner (Sunbird 32 'Matanie'  for sale again I see at: junk schooner for sale, nothing to do with me, but would like to see her go to a good home) we bent nothing in 30 years. Though we weren't adventurous ocean-crossing types we did have our fair share of rough stuff and the rig always handled superbly. Having this year converted our subsequent boat 'Paradox' to a cambered panel schooner junk we managed to bend the main boom and yard in our first sail in F4-5 gusting 6, so it looks as if with cambered sails the moral is go for the next size up...

    David, not having even the world's worst engineering brain, it was taking me a while to figure out why you gave Annie's sail a convex luff. Your last post explaining that the aim is to increase the effect of the LHPs is beginning to make sense, and is something I'll keep in mind as a way of attacking creasing (though I think your idea of two LHPs in the appropriate places may well do the trick, perhaps with the odd light HK parrel or two).

    Has anyone tried hauling a cambered foresail in tight to help reduce rolling etc, eg when motor sailing? Worked well with a flat sail but I imagine ca,mbered will flap around a bit when at or almost head to wind.

    And finally, er, has anyone tried double 'HK' parrels per panel, i.e. one crossing the sail conventionally, fore-aft, and the other running aft-fore, thus giving a 'cross' pattern per panel? (OK, I just had a large glass of Sangria. Chin chin)


    Last modified: 14 Dec 2011 16:56 | Deleted user
  • 13 Dec 2011 13:55
    Quote
    Reply # 772435 on 766440
    Anonymous member

    I may be wrong, but it always seemed to me that a schooner rig with flat sails works a lot better than a single sail.  Perhaps due to the the aft sail being sheeted in harder, therefore the whole having some shape?

    Could be why Ti Gitu sees less improvement than expected.

    regards

    Mark
  • 06 Dec 2011 23:14
    Quote
    Reply # 767436 on 767237
    Anonymous member
    Arne Kverneland wrote:

    Paul and Edward.

    Now I'll try to past in my letter above once more, after it has bee changed to .txt format.

    I fix a bit on it in this editor:

    *************************************

    Stavanger Tuesday
    This is most interesting!
    Ti Gitus problems: ......................
    Tbattens. There seems to be may thin battens out there...
    Cheers,
    Arne

    **********************************************

    That was it. Does this too get outside the frame??

    Arne

     

    All good Arne :-)
  • 06 Dec 2011 19:31
    Quote
    Reply # 767264 on 766440
    Anonymous member
    My experience with my 10% cambered wingsails is that the after sail must be sheeted to windward, if I am to point high. The forward sail might be better sheeted to windward as far as pointing angle goes, but I took off the double sheets that I used to do that, as an experiment, during my crossing of the Tasman Sea. I found that I got less troubles with fouling up, and a good enough vertical sheet angle to sheet in close enough, and suffered no great loss of control due to not being able to triangulate the sheets (particularly when hove-to in big confused seas). So I'd confine my first trials of windward sheeting to the after sail of a two-masted rig. The forward sail, and a single sail, are unlikely to benefit much.

    Hong Kong parrels are one solution to the problem of diagonal creases - but I continue to think that they are not as good a solution as luff hauling parrels, either one or two, applied in the right place, to the right shape of sail. Arne says that his HKs go slack when the LHP is properly set up, but go taut when on the wind, ie when there is more sheet loading tending to distort the sail. IMHO, this is where the convex luff of Fantail's sail scores, by making the upper LHP more effective. I thought we were going to have to fit a middle LHP, but in fact Fantail does very well without it, and doesn't need that extra line and its associated hardware.
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
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