Are Batten Pockets Necessary?

  • 13 Jul 2020 14:51
    Reply # 9098699 on 9094823

    I've wondered about the aerodynamics of Roger Taylor's hinged panels.... a rather ingenious method for building the sail panels on a JR so that you don't have to manhandle the entire sail during the construction process.   Do the gaps have a negative or positive effect....on lift and on drag.... logic would suggest turbulence would be generated on the lee side of the sail, but that's not always a bad thing.  Aircraft sometimes use vortex generators to prevent stalling, and on a vehicle, vortex generators in the proper places ... such as the aft edge of any sharp break in contour such as the back of a station wagon have been shown to reduce aerodynamic drag.   Everything is speculative unless there is a like for like comparative test done.  


                                           H.W.

  • 13 Jul 2020 10:43
    Reply # 9098219 on 9094823

    Pango has aluminium battens but no batten pockets, just a row of single grommets and a single length of lacing, for each batten, with a clever lacing system. )(Through, around, back through the same hole and on to the next.)


    Zane can explain it, or Paul who made the sail. I thought it looked pretty neat and simple, but if I recall correctly, Paul said it would have been just as easy to make batten pockets.

    Last modified: 13 Jul 2020 10:52 | Anonymous member
  • 13 Jul 2020 07:48
    Reply # 9097937 on 9094823

    On my previous junk rigged sailboat, the sail had grommets fitted into strips of webbing sewn across the sail. I fitted douglas fir battens, approx 2" x 1", one each side of the sail and then bolted through the battens and grommets.

    We cruised for a few years with this set up, never broke a batten and it all worked rather well. Having said that, I'm seriously considering going for aluminium tube battens and pockets for the sails on my new boat...

    Last modified: 13 Jul 2020 07:48 | Anonymous member
  • 11 Jul 2020 15:31
    Reply # 9094946 on 9094823
    Anonymous member (Administrator)

    Hi, Jim.

    The short answer:
    Because batten pockets distribute strain better than grommets.

    The long answer:
    I guess it depends on several factors:

    • ·         Batten material
    • ·         DIY or by sailmaker
    • ·         Distance and area of sailing.

    Wooden battens, which break instead of bending, favours either tied on battens or a layout with several shorter lengths of batten pockets. This lets one push out broken stubs, or putting on splints, tied on where the pocket gaps are.
    Personally I would never want to own wooden battens  -  they clearly break too often and weigh too much. With bamboo and CFRE unavailable here, I prefer ‘Norway bamboo’  -  thin-walled aluminium tubes. These work well with batten pockets.

    A sailmaker may possibly make a quicker job of it by banging in grommets on strengthened patches than by sewing on pockets, I dunno, but I, as an amateur have lost confidence in grommets, so all my junksails have been totally free of metal. When using my Amateur Method B of assembling batten panels and adding batten pockets, I bet one would have a hard time making a quicker job with grommets instead.

    For short distance sailing, I certainly would only use simple batten pockets. For long distance sails, I guess I would recommend making 5-10 stubs of batten pockets. This, as said, lets one add splints to a damaged batten, and also reef away a damaged panel quite easily. This last problem will not be serious as long as the sail has been given a strong boltrope around it.
    The hinge type which Roger Taylor and Jami Jokinen make use of, appears to be very good and reliable, but the method is probably slower to make than any other method (More measuring, checking and double-checking...).

    Arne

    PS:
    I have removed my sails from my boats a few times. Apart from the tiny sail of ‘Broremann’, I untie the sail bundle from the boom before lifting it ashore with the battens still in place. This makes re-rigging the sail easier, as I can rig the boom first, with mastlift and topping lifts plus TP and TL before bringing the sail bundle back on board.

    PPS:
    Have you launched Hobbit yet?


  • 11 Jul 2020 13:07
    Message # 9094823

    This may have been asked before but I haven't found anything yet.

    Why have batten pockets? Could our battens just be tied on through grommets. (Hobbit II has this arrangement.) Would it make the sails significantly cheaper?

    A broken batten could be fitted with splints without removing it. 

    It would be easier to set up, especially in windy conditions.

    I suggest, rather than small line that exterior grade wire ties be used. For looks, the joint could be turned inward and moved to a low visibility location. Easy to remove with a knife or other tool. 

    Cost? Think of them as consumables. And since we tend to leave them in place for long periods, removal will be seldom.

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