Freedom 40 Cat Ketch Junk Rig Conversion

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  • 28 Sep 2017 19:14
    Reply # 5284992 on 1424184

    My intention for my rig is to use 12mil thick, 50mil wide neoprene rubber strips to cushion the battens, so they don't clap against the mast. This stuff is readily available, not terribly expensive, and can be ordered online. Neoprene is very good for absorbing vibrations and sound as well, so it should perform well.


    I haven't done this YET, but I was a sound engineer back in the day, and we used neoprene for some applications in sound and vibration insulation. My guess is it would work very well, or at least as well as anything else one might use.


    EDIT: I realized I didn't mention.. this sort of rubber is a bit sticky, so you would have to sheathe it over with a thin, slick covering like sheet vinyl, or alternatively a bit of canvas or poly cloth.

    Last modified: 28 Sep 2017 23:47 | Anonymous member
  • 27 Sep 2017 07:45
    Reply # 5281733 on 1424184

    Annie, Paul - thanks for the input and advice.  I've been banging various things against my metal desk for testing and scaring the dogs.  The hoped for pros of the plastic tube included excellent wear, low friction, and simplicity.  My batten pockets are the "sailmaker type"  and my worry about sewing an added layer of cloth with padding or PVC cloth (vinyl in the US I think) is wear and the difficulty of repairing it.  

    David - that let me move forward.

  • 18 Sep 2017 09:21
    Reply # 5265695 on 5265354
    Paul Thompson wrote:

    If you fill your hollow aluminium or steel mast with polystyrene balls ("beanbag balls") you support the masthead wiring conduit and you eliminate any ringing noises.

    But you still get a hard 'thwack' rather than a soft 'thump'.  It depends how noise gets to one as to whether it's an issue.  We can't all turn off our hearing aids!!!
  • 18 Sep 2017 01:06
    Reply # 5265354 on 5264135
    Annie Hill wrote:

    Two things with PVC pipe worth mentioning:

    1. when you cut it, you end up with very sharp edges which need carefully rounding over so that they don't cut into the sail cloth
    2. PVC is hard and therefore noisy against a tin mast.

    Yes, the edges need to be smoothed with a bit of sandpaper. It's one of the quicker jobs.

    If you fill your hollow aluminium or steel mast with polystyrene balls ("beanbag balls") you support the masthead wiring conduit and you eliminate any ringing noises.


  • 17 Sep 2017 00:27
    Reply # 5264135 on 1424184

    Two things with PVC pipe worth mentioning:

    1. when you cut it, you end up with very sharp edges which need carefully rounding over so that they don't cut into the sail cloth
    2. PVC is hard and therefore noisy against a tin mast.
  • 16 Sep 2017 13:55
    Reply # 5263508 on 1424184

    A 30 degree maximum angle between halyard and mast establishes the minimum mast height.

    The after end of the batten fender positions the lashing of the after end of the batten parrel. There should be a short pocket near the luff, say 200mm long, then the batten fender starts immediately afterwards.

    Last modified: 17 Sep 2017 09:48 | David
  • 15 Sep 2017 19:35
    Reply # 5262696 on 1424184

    Batten pockets and bumper between the batten and the mast....


    Of the different design options, my current preferred one is the "split PVC pipe" mentioned by Paul in an earlier post that simply clips over the batten pocket onto the batten.  For 50mm diameter battens the same size PVC (for our sail grey PVC or black ABS since it coordinates better with our burgundy sails)  seems to work perfect.  Some narrow strips of foam insulation, used to seal windows, stuck onto the ID of the split pipe create a little more "give" and shock absorption.  Friction between the batten and mast is very low.  Finally, there is no extra sewing or gap in the in the batten pocket or attaching padding to the batten.  

    Question - how long should these be.  On my 4100mm long battens and 15% overlap, I have 600mm in front of the mast line.  Is 200mm or so on each side of the mast, i.e. total length of 400 to 500mm sufficient?

    e


  • 15 Sep 2017 19:21
    Reply # 5262666 on 1424184
    Number of Unknowns...

    David - I studied your instructions on designing the bridal and came to the conclusion that I am short one or more knowns (I always have an issue with too many unknowns)... either the position of the mast head and/or the total length of the bridal.  My masts are obviously much taller than needed since they are set up for wishbone boomed triangle sail.  And the intent is to move the halyard attachment point lower and eventually make the masts shorter.  So there isn't a fixed masthead point to aim for.  As to the length of the bridal, I started with two legs that were 45deg to the yard - these looked to be too long if the forward leg's final angle was to be 30deg to the yard.  

    Minimum drift from the bridal:  My halyards will be from 10mm Stayset.  Blocks for these are nominally 125mm in size - times 5 - equals 625mm.  Make it 725mm for extra space.  

    Playing with those and moving things around gives me something like this.




    One of the concerns I have is that the foward attachment point get very close to the mast line and may interfere in some nefarious way.  The points could be moved closer to the center.  And the centerpoint could be moved a wee bit up the yard.  And maybe working with a 100mm yard tube is too complicated and going to the 127mm (5" tube) and a single attachment point is easier.  If I ignore the bridal the length between mast and yard attachment point is about 860mm

    Erik 

  • 14 Sep 2017 20:54
    Reply # 5261203 on 1424184

    David:  Great instructions and I will draft both the halyard and topping lifts now.


    Batten Parallels  - I seem to recall the advice of having a 30 degree angle between the batten and the mast.  At 15% overlap, this angle to the forward end of the batten is more acute, can I do 30 deg or larger (more preferred if it helps in keeping the battens from going forward).   


    This being a double masted rig, I don't see a need to move the sail when sailing downwind to balance things since I can go wing-on-wing.  I could see the parallel tension going more slack if the angle is not 30 degrees as the batten has to move from the 250mm diameter mast at the base (and that diameter up some 7 meters) to somewhere higher and skinnier.  In order to help tension the BPs on the upper battens, I was wondering if I can utilize the throat parallel.  The BP, rather than being fixed at the end of the batten would go through a small block tethered to the end of the batten,  and then terminate a single, free floating block.  The THP would go through this last block.  Tension on the THP would then tension the BP.  Stopper knots could moderate the amount of travel in the BP.  When the sail is dropped, the THP goes slack and the BP could "lengthen" to accommodate the larger diameter mast.  See drawing to aid the description.




    e

  • 14 Sep 2017 19:58
    Reply # 5261073 on 1424184

    The halyard tackle, fixed as usual to the middle of the yard, must have enough drift such that when the yard goes to +/- 90 degrees, the rope doesn't make too great an angle with the sheaves of the blocks, otherwise damage will result. When a span is used at the yard end of the tackle, some extra freedom is allowed the lower block, as the span itself can twist a bit, as well as whatever rotational freedom there may be in the shackle and thimble. This means that the block to block distance when a span is used can be somewhat shorter than when a direct yard connection is used.

    When making the design, I would first mark the points at the one third and two thirds points of the yard, and also at the centre. I would then draw a line from the two thirds point to intersect with a line from the masthead block to the centre of the yard, such that the  angle between the yard and this first line is 30 degrees. Then draw another line from the one thirds point to this intersection, and this will be the shape of the span that you are aiming for. Then allow let's say five times the length of the halyard block for the tackle - two blocks plus the length of three blocks between them. I have found this to be enough drift.

    I tie an alpine butterfly knot (which can take a load in two directions) in the 6mm Dyneema at the intersection point, large enough that a full turn can be taken around the bow of the shackle on the lower halyard block. I tried a stainless steel thimble here, but it soon failed due to fatigue. The 6mm Dyneema should be tied right around the yard at the one third and two thirds points, with a strong eye just to keep them from sliding, not to carry the load.

    I use Dyneema for my lifts as well. I would use 6mm for yours. I tie two forward lift lines halfway down the topping lifts (to an alpine butterfly again) one on each side and lead the line on the mast side to the bottom batten/boom at the after end of the batten parrel, and the line line on the other side to a point level with the mast line. Actually, a span at the bottom of this latter line will help with gathering the bunt of cloth here.

    The reason for doing the forward lifts in this way is twofold. It stops the annoying clatter from a lift that is parallel to and close to the mast; and more importantly, it brings the line of the topping lifts further forward. With the weaverbird planform of sail, I have found that a gybe with three panels up is safe enough without this form of forward lift, but a gybe with two panels up risks getting the yard trapped behind the topping lifts. This planform of sail seems to be much less prone to misbehaving during a wild weather gybe than the HM kind; but there is still a risk, even when the yard has a light extension to bring it to the same length as the lower battens (essential). Moving the topping lifts forward is the cure.

    Last modified: 14 Sep 2017 20:01 | David
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