Loading ...
Sorry, an error occurred while loading the content.

Re: van Loan cambered sail

Expand Messages
  • lself100
    The question I have is, will the camber be lost at the leading edge? Will the sail be flattened by the mast or bulge out? Take Slieve s sail shape and balance
    Message 1 of 36 , Apr 1, 2010
    • 0 Attachment
      The question I have is, will the camber be lost at the leading edge? Will the sail be flattened by the mast or bulge out?

      Take Slieve's sail shape and balance (30%) for example and assume the chord is 5 meters, max chamber is 10% of chord (0.5m, 20 inches) located at 30% of chord. So the mast lines up with max camber. If the chord is 5 meters then there is 1.5 m (5ft) between mast and luff. His aluminum mast is 0.15m (6 inches) diameter at the base. Less diameter furthur up. When the sail with a 0.5m camber, on the "wrong" tack, lies aganist the mast which is only 0.15m diamter will the 1.5m area forward of the mast be flat or bulge out? In theory the mast might not have much effect and the sail area in front of the mast bulges out, perhaps "hiding" the mast. I just can't see how a 6 inch diameter mast set 5ft back from the luff will flatten a sail that would bulge out 20 inches if the mast was not there.

      But, it is only theory on my part.

      rself

      --- In junkrig@yahoogroups.com, "Arne Kverneland, Norway" <arkverne@...> wrote:
      >
      > Stavanger, Wed
      >
      > No, I have no hard evidence on this. However I have plenty of hard evidence that the cambered panel sail works a lot better than a flat one to windward. By shifting the sail more and more forward I am afraid that this will rob most of that hard-won camber, and then I'll be back on square 1 (flat sail performance). I see no way to avoid this except making a slotted junk sail as Slieve has done.
      >
      > I agree with you on all the 4 points you mention.
      >
      > And yes, I can make a test on Broremann.
      > • except that the mast will be then be too short (but I can reef a panel),
      > • the batten parrels must be made longer (so I must burn holes in the batten pockets)
      > • and the boat will get a bad lee helm.
      >
      > Arne
      >
      > PS:
      > Frankly I haven't seen any photos of van Loan sails with cambered panels.
      >
      >
      >
      >
      > --- In junkrig@yahoogroups.com, "lself100" <abarenicola@> wrote:
      > >
      > >
      > >
      > >
      > >
      > >
      > > Hi Arne,
      > > Is there any hard evidence that a Van Loan shaped sail with large balance, if cambered, will have lower performance to windward on the "wrong" tack compared to a cambered sail with less balance?
      > > The reason I ask is because there are worthwhile advantages to a sail with 20-25% balance (like Slieve's sail without the split).
      > > 1) Mast can be set furthur aft closer too boat's axis of pitch.
      > > 2) Less weather helm on off-wind courses.
      > > 3) CE of sail is closer to mast which means lower sheet loads and therefore lower sheet power required. Total length of sheet is shorter (less spaghetti) and less sheet friction means lighter lifting loads at the halyard.
      > > 4) S-shaping can be overcome with stiffer battens.
      > >
      > > Your junk rigged Broreman(spelling?) skiff would be the perfect vehicle to provide "hard evidence", perhaps, by moving the sling point aft and giving your sail more balance than it has now.
      > >
      > >
      >
    • Arne Kverneland, Norway
      Thanks Jeff for the kind words. Gracious - I had to look it up :-) ! Cheers, Arne
      Message 36 of 36 , May 22, 2010
      • 0 Attachment
        Thanks Jeff
        for the kind words.
        Gracious - I had to look it up :-) !

        Cheers,
        Arne




        --- In junkrig@yahoogroups.com, "junkrigsailor" <junkrigsailor@...> wrote:
        >
        > Arne-
        > Mostly I just lurk here because pretty near everyone knows more and does more than me so I don't have a lot to add. There is one thing I know for sure, though. This group is amazingly fortunate to have you as a member. Your design work and generosity are only topped by your gracious nature. Thank you
        > ~Jeff
        >
      Your message has been successfully submitted and would be delivered to recipients shortly.