Cambered panel sails on Wild Fox

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  • 11 Dec 2011 15:33
    Reply # 771002 on 770677
    Anonymous member (Administrator)

    Stavanger, Sunday

    I was about to write a bit more about the upper luff hauling parrel, but I see now that Jonathan has explained it better than I ever could, so I only let you have the sketch I just made:

    (..if this photo will not open automatically, it can be found under my Member Photo Album...)

    The whole idea with the upper LHP is to force the top section aft into correct position. The sail will then hang nicely down from there without trying to fall forward. The tack parrel should be almost slack. With this LHP set up, the yard hauling parrel can be set up to take the sheet forces. Together these two parrels both fix the yard in the right fore-aft position and also keep it peaked up under load.

    Needless to say, I find it a lot easier to set up the sail with the sheet flying than with wind in the sail.

    Arne

    PS: I hope this little photo doesn't corrupt the text. Click on it to make it bigger.

    Last modified: 29 Dec 2015 15:28 | Anonymous member (Administrator)
  • 11 Dec 2011 14:34
    Reply # 770987 on 770677
    I don't claim to understand these things, but I can confirm that what Arne has written about the upper luff hauling parrel is consistent with what has been done by Robin Blain to Lexia, with the result described by Arne.  The upper luff hauling parrel does the work and sets the camber in the panels without significant creasing and, surprisingly to me, sets the lower panels all the way down the sail.  Robin rigged the upper parrel forewards and then straight backwards rather than zig zagged down, if that makes sense.  The lower luff hauling parrel, which is still in place, seems to be redundant and may be re-rigged as a downhaul or removed.  We have not since experimented with Hong Kong parrels, not yet feeling the need to make any further improvement.  The battens are very substantial stiff aluminium alloy tubes (dimensions not available immediately, the boat being 300 miles away, but hopefully to follow) which show no sign of bending.  Whether the performance is better than it was with the previous flat sails and flexible grp battens I cannot say because we changed to cambered panels and stiff battens soon after purchasing the boat.  However, I can confirm that on return from the Azores the 32 foot boat beam reached at 140 miles per day with minimal attention to the sails.  I don't know  how that compares with a flat sail Sunbird 32 but others may comment.  I hope this may help.  jds
  • 11 Dec 2011 12:16
    Reply # 770947 on 770677
    Anonymous member (Administrator)

    It was not told what sort of luff hauling parrel that was used on Fire Fox. If an ordinary LHP was used, i.e. acting on several battens down the luff, this will just make matters worse and increase the load on the Hong Kong parrels and battens.

    The trick is to fit just an upper LHP which acts on the yard and batten no 1 or 2  -  in effect being a throat hauling parrel. With this one set up (and the yard hauling parrel against it) the lower panels will hardly need an extra LHP or just one that is lightly set up. It is here the Hong Kong parrels now come in  -  as light trimming lines with low load on them.

    Fire Fox's rig otherwise loks good in my eyes, so with these easy fixes, I think things will improve.

    Arne

    PS: Like Gary K, I too would like to hear about the scantlings of the battens

    PPS: BTW, the thinking behind moving the LHP up to the throat has been described in my little write-up, "Junk Rig for Beginners" found in my folder under the public pages. I think this throat hauling parrel is an important detail since, unlike the flat sails, the cambered panels have no built-in diagonal stiffness.

    Last modified: 11 Dec 2011 13:16 | Anonymous member (Administrator)
  • 11 Dec 2011 11:18
    Reply # 770930 on 770677
    Deleted user
    I wonder what kind of battens on Wild Fox. Great looking boat btw.

    We will still go for cambered sails, (our boat is definitely going offshore). Probably 50mm diameter aluminium battens on the 30sqm & 22sqm sails.

    edit added:
    Appears that with flat panels, the sail fabric takes much of the load to maintain shape. Cambered panels move all the load to the battens, so maybe the battens need a doubling in strength in such a case (?).
    Last modified: 11 Dec 2011 11:29 | Deleted user
  • 10 Dec 2011 21:57
    Message # 770677

    Here is an excerpt from correspondence between Annie Hill and Anthony Swanston, owner of Wild Fox, a Benford 37ft dory, which they have agreed may be published. It makes interesting reading.

    (I've put a photo of Wild Fox in the Photo Gallery).

    Hi Anthony,

    I see you have cambered panels.  You definitely need to do something about the diagonal creases and I suggest fitting running luff parrels - a lot kinder than Hong Kong parrels.  It may make an appreciable difference to Wild Fox's performance.

    Annie


    Annie

    We had correspondence about this when I was in Madeira in about October 2009.  The cambered sails were a mistake.  I do have a running luff parrel.  It did not take the creases out.  I fitted Hong Kong parrels and the tension on them broke the battens. I then put a slightly slack line from the luff end of the batten to the centre of the batten and attached the HK parrel to this - effectively spreading the load.  The batten still broke.

    Story over.  Next time traditional flat sails...

    You seem to have quite a bit more sail forward of the the mast than I have and perhaps that gives the running luff parrel more leverage to remove creases.  I told Alan Martienssen I was against cambers.  Even with the HK parrels the camber effect disappears as soon as you put a reefs in as the tension is progressively lost.  Your 2009 view that cambers are OK for inshore sailing would seem to be correct.

    Until I am happy with the rig and the balance issue I am on the fence about crossing the Pacific - the boat is a hard mouthed pig downwind in 20 plus knots... 

    Anthony

    That's two ocean going schooners that have been disappointed with cambered panel sails. I think the common factor is schooner rig with high aspect ratio sails, and little balance area forward of the masts. 


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