"Aphrodite" - new rig

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  • 04 Apr 2011 14:43
    Reply # 563788 on 522888
    Deleted user
    Paul,

    I always get confused about which direction of stagger is "positive" and which way is "negative".  You are correctly answering the question I meant to ask :)

    Barry
  • 03 Apr 2011 19:47
    Reply # 562302 on 562246
    Barry & Meps / Stellrecht & Schulte wrote:
    Paul Thompson wrote:However, when you go to shaped panels, the the standard rules are only a guide as because the panel has no diagonal stiffness, the panels is not contained by the cloth to the same extent.

    However it would still be wise to check before hand using the PJR method to make sure that the stagger produced by your sail shape will be negative. Then you are unlikely to have problems.

    Exactly the problem I'm thinking about.  I did start with boom angles based on the PJR 1% stagger calculation, but when I realized that the cambered panels wouldn't have appreciable diagonal stiffness, I felt a bit lost on how it would end up working out.

    In my case, my mizzen PJR would tell me to make my mizzen at 11 degrees.  I've drawn both booms at 10 degrees, so PJR would give me a bit less negative stagger (near zero, but I've not calculated exactly).  I was thinking that PJR would put my main at 9 degrees.  Now I'm thinking about it again, and I realize that the calculation didn't consider that my main is a split sail, so I'm doing the calculation based on the wrong batten length.  Better go back and re-check that calc, especially since I haven't cut the main out yet.

    Thanks for the report!

    Barry

    Barry, I should have said positive batten stagger But my fingers and I were apparently thinking of different things :-(. I have corrected my original post to reflect this.

    I think however that you also meant positive stagger when you replied. If not, sorry to have mislead you.

    Positive stagger is when the battens stager aft when furled or reefed. If you have single sheeting, this is what you want. If you have double sheeting it does not matter so much.

    One of the key reasons for checking stagger (apart from sheeting) is to make sure that the yard remains on the mast.  This is something you need to be sure of with your mizzen as you have very little balance on that sail.

    The key thing to take home is that while you should check and design for a positive (battens stagger aft) stagger, when you put camber in those rules do not hold so well. The more camber you have, the looser the fit of the rule becomes.

    But generally the parallelogram type sails like HM and van Loan tend to have positive stager. Fanned sails are another story.
    Last modified: 03 Apr 2011 19:47 | Anonymous member
  • 03 Apr 2011 17:29
    Reply # 562246 on 561977
    Deleted user
    Paul Thompson wrote:However, when you go to shaped panels, the the standard rules are only a guide as because the panel has no diagonal stiffness, the panels is not contained by the cloth to the same extent.

    However it would still be wise to check before hand using the PJR method to make sure that the stagger produced by your sail shape will be negative. Then you are unlikely to have problems.

    Exactly the problem I'm thinking about.  I did start with boom angles based on the PJR 1% stagger calculation, but when I realized that the cambered panels wouldn't have appreciable diagonal stiffness, I felt a bit lost on how it would end up working out.

    In my case, my mizzen PJR would tell me to make my mizzen at 11 degrees.  I've drawn both booms at 10 degrees, so PJR would give me a bit less negative stagger (near zero, but I've not calculated exactly).  I was thinking that PJR would put my main at 9 degrees.  Now I'm thinking about it again, and I realize that the calculation didn't consider that my main is a split sail, so I'm doing the calculation based on the wrong batten length.  Better go back and re-check that calc, especially since I haven't cut the main out yet.

    Thanks for the report!

    Barry
  • 03 Apr 2011 02:04
    Reply # 561977 on 559422
    Barry & Meps / Stellrecht & Schulte wrote: Does anybody know how this rig reefs?  I'm wondering if there is a batten stagger problem where the boom sticks out aft of the rest of the sail bundle as you reef?

    I see that Aphrodite has double sheets, so this sort of stagger isn't going to foul much of anything, but I would prefer to do otherwise, so it will matter to me.

    Thanks!

    Barry

    Aphrodite has normal (ie. positive) batten stagger just like the HM rigs have. You can checkout what your batten stagger will be on the drawing board before hand. PJR tells you how.

    However, when you go to shaped panels, the the standard rules are only a guide as because the panel has no diagonal stiffness, the panels is not contained by the cloth to the same extent.

    However it would still be wise to check before hand using the PJR method to make sure that the stagger produced by your sail shape will be positive. Then you are unlikely to have problems.
    Last modified: 03 Apr 2011 02:04 | Anonymous member
  • 02 Apr 2011 14:22
    Reply # 560720 on 559422
    Deleted user
    Barry & Meps / Stellrecht & Schulte wrote: Does anybody know how this rig reefs?  I'm wondering if there is a batten stagger problem where the boom sticks out aft of the rest of the sail bundle as you reef?

    I see that Aphrodite has double sheets, so this sort of stagger isn't going to foul much of anything, but I would prefer to do otherwise, so it will matter to me.

    Thanks!

    Barry
    Our first sea trial was in semi-nasty weather and we did have to put in a couple of reefs.  As I recall the battens came down evenly and presented no problems.  Unfortunately I was down below dealing with an errant refrigerator when Paul, Kurt and Annie put in the reefs so I hope one of them will be able to answer your question in sufficient detail.  
  • 01 Apr 2011 19:02
    Reply # 559422 on 522888
    Deleted user
    Does anybody know how this rig reefs?  I'm wondering if there is a batten stagger problem where the boom sticks out aft of the rest of the sail bundle as you reef?

    I see that Aphrodite has double sheets, so this sort of stagger isn't going to foul much of anything, but I would prefer to do otherwise, so it will matter to me.

    Thanks!

    Barry
  • 21 Mar 2011 18:57
    Reply # 550449 on 550393
    Arne Kverneland wrote:                  The performance of the fanned top section.

    Kurt.

    It is easy to think that a fanned top section of a cambered panel junk sail may produce more drag than lift with the wind having to climb over the battens. However, practical experience with sailing my Johanna with only 3 panels set has proven that the fanned top indeed is efficient both when it comes to driving force and pointing. I guess she points roughly 5 -7° worse than with full sail, but then one must remember that the windage of boat and mast has risen compared to the reduced sail area.

    Arne

    Arne,

    I choice the van Loan shape as I found that it enabled me to get the maxim sail area that I could achieve for a given mast hight and LOA. That is an issue with heavy boats and one that you do not have on Johanna. Efficiency of the triangular top section did not come into it.

    Whether the triangle shape head adds to efficiency or not could only be proved by trying the two different sail shapes on the same hull and in similar conditions. I suspect that there will not be to much in it.

    What I can say, is that while the boat has only been sailed in light airs to date, she has performed as expected. What more could I want?
  • 21 Mar 2011 17:31
    Reply # 550393 on 523006
    Anonymous member (Administrator)
    Kurt Jon Ulmer wrote:
    .
    .
    .
    My gut feeling after a couple of good sails on Aphrodite is that the Van Loan pattern Paul chose, with roughly parallel battens, is a very good choice for that approach to camber. High-peaked yards might extend the effective luff, but any camber in peaked-up panels could be ruffling the air more than deriving forward lift from it. 
    .
    .

    Cheers,
    Kurt

    Stavanger, Mon

                      The performance of the fanned top section.

    Kurt.

    It is easy to think that a fanned top section of a cambered panel junk sail may produce more drag than lift with the wind having to climb over the battens. However, practical experience with sailing my Johanna with only 3 panels set has proven that the fanned top indeed is efficient both when it comes to driving force and pointing. I guess she points roughly 5 -7° worse than with full sail, but then one must remember that the windage of boat and mast has risen compared to the reduced sail area.

    Arne

  • 21 Mar 2011 04:21
    Reply # 550063 on 522888
    Carl Bostek, Aphrodite's owner has posted a short article on his Facebook page.

    Anyone interested can see it here Aphrodite First Cruise but do be aware that you need a Facebook account to view it. I do not have one, so have never seen it :-(


    I will be doing a full write up one of these days but right now the priority is getting La Chica back in the water.
    Last modified: 21 Mar 2011 04:21 | Anonymous member
  • 16 Feb 2011 06:05
    Reply # 523006 on 522888
    Aphrodite's rig deserves a full write-up, which I hope Paul will do. I was involved as an extra hand to help finalise the setup Paul and Annie had started.

    I do have thoughts! No performance figures, but certainly thoughts about the concept of Camber and how to create it.

    The Van Loan sailplan with shelf foot camber in all panels and Hong Kong parrels, sets up smooth and sensible-looking camber, all fairly in line with the airflow - which the battens would help guide across the sail. 

    My gut feeling after a couple of good sails on Aphrodite is that the Van Loan pattern Paul chose, with roughly parallel battens, is a very good choice for that approach to camber. High-peaked yards might extend the effective luff, but any camber in peaked-up panels could be ruffling the air more than deriving forward lift from it. 

    I've been quietly pursuing a little education, camber included, from old JRA newsletters. I reckon some of the wheels one could invent, may have had a few tyres changed by now... My respect for our experimenters grows.

    Cheers,
    Kurt
    Last modified: 16 Feb 2011 06:05 | Anonymous member
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