Wanted: mast +/- sail for Corribee/Coromandel, am planning to junk my Corribee (UK)

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  • 20 Oct 2024 15:25
    Message # 13421143

    Preferrably a tapered aliminium mast, Old sail will serve as a pattern for a new one

    Last modified: 21 Oct 2024 14:08 | Anonymous member (Administrator)
  • 20 Oct 2024 20:08
    Reply # 13421182 on 13421143
    Anonymous member (Administrator)

    Jes,

    can you tell us which mark number of the Corribee you have?
    Moreover, what sort of sailing are you planning to do?


    Arne

    Last modified: 20 Oct 2024 20:21 | Anonymous member (Administrator)
  • 21 Oct 2024 05:59
    Reply # 13421295 on 13421143

    Hi, she's  an early MkII Corribee, 1978, ie no anchor locker at the bow.  Possible sailing plans include Jester Challenges, more West Coast of Scotland exploration, Shetland, Faroes...last year I sailed round Britain

  • 21 Oct 2024 08:18
    Reply # 13421307 on 13421143
    Anonymous member (Administrator)

    Good, Jes.
    Have you figured out where to put the mast?

    Arne

  • 22 Oct 2024 08:03
    Reply # 13421814 on 13421143

    As I understand it, the mast partners is pretty much centred on the existing forehatch apperture which will have to be covered and strengthed.  I think there should also be a few degrees of forward rake to decrease weather helm. Correct me if I'm wrong

    Last modified: 22 Oct 2024 08:08 | Anonymous member
  • 22 Oct 2024 10:41
    Reply # 13421842 on 13421143
    Anonymous member (Administrator)

    This summer JRA member Paul Schnabel has successfully cruised his Maxi 77 with his junkrig set with up to 27% mast balance.
    I have therefore made use of his findings and drawn a hi-balance sail for the Corribee, shown below.

    The mast was put through the hatch, with its centre about 200mm aft of its forward edge.

    I don’t think the sail will ever need to be moved forward of the shown position. If anything, it rather needs to be shifted aft a little to trim away any lee helm. There will be plenty of room for that.

    The Corribee has a smallish rudder. This hi-balance JR brings its CE quite close to the JR mast, which again means that the CE will sit close to the boat’s centreline when sailing downwind. This should help the rudder to cope.

    Just an idea.

    Arne

    PS:
    It looks to me that the superstructure of the Mk 2 and 3 are very similar, so I used a Mk 3 version here.

    (Hi-res diagram in Arne's sketches, section 8, photo11)


  • 22 Oct 2024 16:16
    Reply # 13421950 on 13421143

    Thanks for this, all very helpful.  Please explain what mast balance is, is it to do with % of sail forward of the mast?  In terms of making a mast I may be looking at the hybrid option, aluminium tube and a wooden top section.    If my aluminium part is 6m long and around 5" (using your formulae) does that not look rather clumsy? Maybe that's all part of the junk look?

  • 22 Oct 2024 16:27
    Reply # 13421964 on 13421143
    Anonymous member (Administrator)

    Jes,

    since my sails generally have a lower section with parallel battens and with the luff and leech parallel to the mast, I define the mast balance of my sails to be the number of percent (of batten length B) that the lower battens protrude forward of the mast.


    Arne


    PS: The lower mast of my Frøken Sørensen had a section of Ø100 x 4mm. I bet that is enough for your boat as well.


    (EDIT: Now I'm not so sure: Jester Challenge  -  see later posting...)

    Last modified: 22 Oct 2024 21:58 | Anonymous member (Administrator)
  • 22 Oct 2024 17:48
    Reply # 13422032 on 13421143

    Using you formulae in 'The Hybrid Mast' I get a Mr max 396, so Mb max of 792 needed for the boat


    A 100x5mm aluminium tube should have an M b yield of 826, and 100x4mm gives only 681kpm whihc is not enough.  So  I'd probably go for 100x5mm tube.


    NB I haven't included my working which usually means you fail the exam!!



  • 22 Oct 2024 19:24
    Reply # 13422101 on 13421143

    May I come in on the mast size, Jes?

    My preference for offshore sailing was to go for a larger, thinner wall section, so as to get more stiffness for a given strength. Particularly in tidal overfalls, a mast that whips around is most unpleasant. My last boat before I quit sailing, a 22ft 6in Hunter Duette, Weaverbird, has a 177m dia x 3mm tapered aluminium mast, which didn't look too large, and I was glad of its stiffness in rough going. These tapered sections are a little softer than the 6061T6 of a hybrid mast's tube, so for sufficient strength and stiffness for offshore sailing, you can certainly come down to 152mm dia x 3mm, possibly to 127mm dia x 3mm, but as you mentioned The Jester Challenge, I really wouldn't want 100mm dia of any wall thickness. Dirty weather in mid-ocean causes one to have enough to worry about without the mast behaving like a fishing rod!

    I know that Mingming II, a larger boat, has a 200mm mast, but can't find the size of the original Mingming's mast (Eric A will know).

    Last modified: 22 Oct 2024 19:29 | Anonymous member
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