Ingeborg and Jester - comparisions between sail area and cambered or flat panels.

  • 23 Aug 2016 09:16
    Reply # 4205188 on 4205114
    Anonymous member (Administrator)
    David Tyler wrote:
    Chris Gallienne wrote:

    Often thought Jester would suit a split rig - same planform, just cambered and split:

    Same planform, cambered and split - OK. But please, scaled up to at least 30 sq m!


    I agree with David  -  that is I  -  would like to see two versions:

    For the sake of science, one should first make a 22sqm split junk version, just to demonstrate what the split and camber did to the sail.

    Then, for the sake of fun, one should make one at 30sqm  -  at least!

    Arne

    Last modified: 23 Aug 2016 09:57 | Anonymous member (Administrator)
  • 23 Aug 2016 08:51
    Reply # 4205114 on 4204562
    Chris Gallienne wrote:

    Often thought Jester would suit a split rig - same planform, just cambered and split:

    Same planform, cambered and split - OK. But please, scaled up to at least 30 sq m!
  • 23 Aug 2016 08:47
    Reply # 4205104 on 4204857
    David Thatcher wrote:
      I don't think camber makes any difference in speed once the wind is 70 degrees off the bow, so added sail area might help there, although I see that as less important since the rig is very powerful when the wind is free. 



    I can say without any doubt that the camber in the sail on Footprints adds a tremendous amount of power in reaching conditions. The boat is significantly faster than with the flat sail. This might also have something to do with the low aspect ratio of the sail as opposed to a higher aspect rig (?) 
    I agree, on both counts, David. While the air is still flowing across the sail, ie, the sail is not stalled, a cambered sail will be more powerful. This ought to be true until the apparent wind is at least on the beam, so the true wind is somewhat aft of the beam.

    C A Marchaj showed many years ago that low AR sails are better than high AR sails, downwind.

  • 23 Aug 2016 07:40
    Reply # 4204925 on 4204857
    David Thatcher wrote:
      I don't think camber makes any difference in speed once the wind is 70 degrees off the bow, so added sail area might help there, although I see that as less important since the rig is very powerful when the wind is free. 



    I can say without any doubt that the camber in the sail on Footprints adds a tremendous amount of power in reaching conditions. The boat is significantly faster than with the flat sail. This might also have something to do with the low aspect ratio of the sail as opposed to a higher aspect rig (?) 

    That's very interesting, David.  My flat sail has the same planform as the cambered one did and it seems to me that the boat is just as fast from a reach to a run.  I could be wrong though.  Only way to be sure would be to have two identical hulls and trial different rigs.  It is always interesting to consider other opinions.
  • 23 Aug 2016 06:53
    Reply # 4204857 on 4204559
      I don't think camber makes any difference in speed once the wind is 70 degrees off the bow, so added sail area might help there, although I see that as less important since the rig is very powerful when the wind is free. 



    I can say without any doubt that the camber in the sail on Footprints adds a tremendous amount of power in reaching conditions. The boat is significantly faster than with the flat sail. This might also have something to do with the low aspect ratio of the sail as opposed to a higher aspect rig (?) 
  • 23 Aug 2016 00:03
    Reply # 4204562 on 4175442
    Deleted user

    Often thought Jester would suit a split rig - same planform, just cambered and split:

  • 22 Aug 2016 23:47
    Reply # 4204559 on 4204494
    Annie Hill wrote:Wouldn't it be great if Trevor Leek put either an Ingerborg rig, or David's improved sail on Jester, to see what a difference it would make?  If Jester would perform anything like Arne's and David's boats, it would do a lot to make people realise what a realistic alternative junk is to bermudan rigs.

    Wouldn't it be great if Trevor, and therefore Jester, were in the JRA?



    Even if Trevor just put camber into Jester's existing rig it would make a lot of difference to windward.  I don't think camber makes any difference in speed once the wind is 70 degrees off the bow, so added sail area might help there, although I see that as less important since the rig is very powerful when the wind is free. 

    Mast position may be another issue.  I have come to the conclusion after sailing Arion 2000 miles at sea with my new flat sail that I have more weatherhelm now when broad reaching and running.  The centre of area is the same as it was for my cambered sail but I suspect that the centre of pressure of a cambered sail is further forward.  On the flat sail it is in the same place as the centre of area but on a cambered sail I think it may trend towards the point of deepest camber, which on Arion would put it about 500mm further forward.  Unfortunately, my sail is already as far forward as I can get it so I just have to reef earlier downwind.  That's ok, as, like Roger Taylor, I like to keep things soft and gentle, reducing stress on rig and crew.

    Still, it would be fun to see Jester screaming around with a big rig, although Trevor might disagree!



    Last modified: 22 Aug 2016 23:49 | Anonymous member
  • 22 Aug 2016 21:50
    Reply # 4204494 on 4175442
    Wouldn't it be great if Trevor Leek put either an Ingerborg rig, or David's improved sail on Jester, to see what a difference it would make?  If Jester would perform anything like Arne's and David's boats, it would do a lot to make people realise what a realistic alternative junk is to bermudan rigs.

    Wouldn't it be great if Trevor, and therefore Jester, were in the JRA?


    Last modified: 22 Aug 2016 21:51 | Anonymous member
  • 22 Aug 2016 11:22
    Reply # 4203799 on 4175442

    Iain, that's the length that I've used.

  • 22 Aug 2016 11:19
    Reply # 4203796 on 4175442

    A quick query on canting the sail.  How long do the batten parrels have to be?


    My only guidance is PJR, Fig. 7.4 (pg. 117).  This seems to suggest that the parrels should be about half the length of the battens.


    Is that about right?

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