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Reversed spreaders on mast  Bottom

  • An idea, reverse the spreaders on the mast to gain an automatic mast bend. Typically the aft raked spreaders induce pre-bend. I have found that when you induce more bend by mainsheet and downhaul, the center of the mast will fall off to leeward a bit. If you reverse this and use less spreader tension, the mast would be straight in light air but allowed to bend (limited by the forward rake and tension) with downhaul and mainsheet tension. It is dramatically different and the diamond wires would probably need to go up one size. The trick would be to have enough side support to keep the side loads in check and to have the rake forward enough to control the bend.

    thoughts...

    --
    Scott

    Prindle 18-2 Mod "FrankenKitty"
    Tornado Classic "Fast Furniture"
    Prindle 19 "Mr. Wiggly" - gone
    Nacra 5.8 "De ja vu"
    Nacra 5.0
    Nacra 5.8
    Tornadoes (Reg White)
    --
  • I'm just glad my P16 doesn't have diamonds. You've gone and confused me.
    I think I get your point, and to a certain extent it makes logical sense and it is wild enough that no one would have thought of it before.
    The one caveat to me is it would seem to have to be a particularly bendy mast.

    --
    Joshua

    Texas Gulf Coast
    '82 Prindle 16 (Badfish)
    --
  • I would think that if that was an option the builders would say so. They are the marine engineers,
    I do not think you are taking the cut of the sails into consideration, mast rotation, pre bend is induced by diamond wire tension.
    What boat are you going to try this on
  • I am sure it is different for different cats, but my 5.0 has its diamonds slacked to allow for the mast to bend up to the limit of the diamond wire facing the bow. What I have read is that your mast rotates to the wind and bends on the minor axis. This reduces the camber of the sail and is better for low and high wind. A straight mast (minimal diamond tension) is best for medium wind. Of course I only race myself and can't say from experience. But hey, I am still in first place!

    --
    Robert
    83' NACRA 5.0
    Previously owned H18, Trac 14, G-Cat 5.0, H14T
    BYC, Mobile, AL
    --
  • QuoteOf course I only race myself and can't say from experience. But hey, I am still in first place!

    a win is a win is a win!

    congrats prost
  • One drawback would be that I would think a battened mainsail would be very difficult to hoist on a mast bent forward.

    --
    Bill Mattson
    Prindle 19 "Gelli Bean"
    Prindle 19 "Cat's Pajamas"
    --
  • To clarify from a couple of comments. I am currently racing a P 18-2 modified and a classic Tornado. But, I have also raced P19s, N5.8s, N5.2s, N6.0s over the last 28 years. I owned a rigging shop for about 15 years and have many years working the floor of a sail loft. I've built my own P 19 sails and assisted in the design of my 18-2 sails. On the cut/design of the main, it would become a mix of soft and hard rigs. While at rest, the mast would be straight with the diamond wires loose. But, Mattson is correct that a mainsail would be difficult to raise with the mast bent forward (inverted). This is a common issue we have with furling masts on big boats. The mast would never intentionally be inverted. I have broken masts from accidentally being inverted. Regarding the cut/design of the main; sails have a luff curve built into them. This and the depth of the panels add to the draft (shape) of the sail. Basically the idea is similar to a jumper where the diamonds, with the angle forward, restrict the bend of the mast. Currently, (depending on soft or hard rig on how much spreader sweep and tension) the spreader sweep aft induces bend and restricts side load. The proposed would still restrict side load, but restrict fore/aft bend instead of inducing it. One thing that happens with swept spreaders is when one loads up the downhaul, it induces more fore/aft bend which loosens diamond tension (check tension with a gauge). This in turn allows the mast to bend more sideways and close the slot between the main and jib - thus choking the slot. Hence one reason for reducing rotation with a hard rig. The overall idea is to maximize shape in light airs, but allow the mast to adjust it's shape to accommodate for the luff curve and flatten the mainsail out when the rig loads up. This is similar to the reason we adjust the amount of sweep of the spreaders; to induce more or less pre-bend in the mast to match up the luff curve of the main.

    When you have a chance, look up your mainsail luff while you load up your downhaul. You will be amazed on how much the mast bends.

    --
    Scott

    Prindle 18-2 Mod "FrankenKitty"
    Tornado Classic "Fast Furniture"
    Prindle 19 "Mr. Wiggly" - gone
    Nacra 5.8 "De ja vu"
    Nacra 5.0
    Nacra 5.8
    Tornadoes (Reg White)
    --
  • It works. What the reverse spreaders gives you is the ability to go to a much lighter bendier mast, where you have wider range to control stiffness via tension in the shrouds.

    The UFO foiling dinghy uses this exact strategy, coupled with a kinda wishbone boom attached to the spreaders. Google it up for some images. It has a very versatile rig. There's some historical background of early wooden rigs with forward struts.
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  • April 22, 2019
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