Space between mizzen mast and mainsail

Discussion in 'Hydrodynamics and Aerodynamics' started by sanantonnio, Dec 7, 2017.

  1. gonzo
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    gonzo Senior Member

    It's not what I call it, but what it is. A cutter has two foresails, so the forwarmost can be dowsed to balance the boat when reefing. That is not possible in a sloop. A smaller headsail will have its center of effort shifted forward, since the forestay is not movable. Further, the main is also shifted forward.
     
  2. TANSL
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    TANSL Senior Member

    Whatever you call it, what you say in posts # 5 and # 11, apparently, is not true. Could you prove that it is?. Thanks.
     
  3. PAR
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    PAR Yacht Designer/Builder

    I'm not sure what bee is in your bonnet TANSL, but his statement is correct in those previous posts, ketches are easier to balance under various hoist, douse and reef options, if only because of the larger number of options. If you have this in doubt, go sail a gaff cat and see what happens as the wind picks up, even after you've tucked in a reef. Sloops do the same thing, though have a few more options than a cat, while ketches have more options, so more ways to fine tune helm pressure and more importantly, stay in the 3 degree window of it's groove. It' s also important to not confuse a cutter (actual) with a double headsail rig on a sloop. A cutter's mast is nearly amidship, while a sloops mast in in the first 1/3rd of the LWL. This placement makes a huge difference in how the boat balances under different hoist options. Again, as I mentioned previously, if any of the proposed rigs is well thought out in the design process, (some aren't) they'll do fairly well in the usual wind strengths they'd intended to operate in, reefed or not.

    I disagree in that the boat many balance horribly with a fully reefed main and storm jib, but would suggest that a fully reefed main and storm jib may be too much and a better option would be to douse the main and hoist a trisail and storm jib instead. When confronted with these choices, you're running out of options and getting a little scared (because you're running out of options). Most will error on the side of not enough area, thinking things may get worse, than enough to carry on at best speed or control. The jib and jigger technique I mention, solves this dilemma, if only for short duration wind speed occasions, which is what I assume Gonzo was referring to previously, while others (another assumption) were referring to much longer duration wind events, in which you'd need more durable and reinforced reefing options. The fact that you don't know the difference, shows your lack of sailing experience, which brings to question why you've insisted to point out these things, you don't fully understand or have experience with, let alone question someone that obviously has.
     
  4. gonzo
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    gonzo Senior Member

    I carry a small stormjib that gets hoisted with the spinnaker pole's topping lift. I find it helps keep the balance on the boat when it has three reefs down. I also use it for self steering balance. I once sailed from Nicaragua to Eastern Colombia without hardly touching the tiller.
     
  5. TANSL
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    TANSL Senior Member

    Yes, this is what I think too but, as I'm not a sailor, I colud be wrong (although, to my consolation, some experienced sailors are also wrong). That's why I ask for a demostration about my mistake. Anyway, for my part, there would be no problem in leaving things as they are. Thank you all.
     
    Last edited: Dec 12, 2017
  6. fastsailing
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    fastsailing Junior Member

    Do you realize that even then both sails in a sloop move CofE forward, the total CofE can move aft. It happens when reefed main is proportionally closer to full main than smaller jib is to the big one. It is not too difficult in practice to keep CofE approximately the same when reducing sails.
     
  7. gonzo
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    gonzo Senior Member

    I can't visualize what you are saying. How do two CoE moving forward produce a net aft movement?
     
  8. latestarter
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    latestarter Senior Member

    This particular bee has lasted way beyond its natural lifespan. ;)
    For years when Gonzo posts, TANSL tries to pick holes in what Gonzo has written.
    I have never blocked anyone on this or any other forum but I put TANSL on ignore this morning.
    Unfortunately in doing so the meaning of some threads is lost.
    :(
     
  9. MikeJohns
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    MikeJohns Senior Member



    Look up Steinlager II and New Zealand Endeaver both Whitbread maxis. A fair amount of money and wind tunnel testing went into those designs.
     
  10. MikeJohns
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    MikeJohns Senior Member


    Maxi ketches won the last of the two Whitbread races. Steinlager II even won every of the 6 legs consistently beating the very similar sloop rigged Maxi "F&P". The vessels were very close in performance but the ketches were actually faster overall.
     
  11. rwatson
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    rwatson Senior Member

    Well, I suppose a few exceptions don't prove a principle. What years were these ?
    Here's some comments I found on Steinlager II

    "Due to race course changes for the 1989/90 Whitbread a different kind of yacht was called for, again Sir Peter Blake drew from his experience and knowledge of sailing to create Steinlager 2, "

    So, for special courses, it can perform well.

    Just look at the recent Sydney/Hobart - and the placing of ketches in the race. Then look at worldwide racing design - not a lot of ketches.
     
  12. MikeJohns
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    MikeJohns Senior Member


    Just your run of the mill world race divided into 6 legs. A USA stopover for the first time in Florida was the “special course change”. Total race distance 32knm, 23 boats 17 of which were Maxis.

    Really though the rule favored the ketches as the full amount of sail a ketch could set on some courses was higher than the same sized sloop. And ketches can fly a lot of useful sail between the masts, they are very handy rigs with a lot of possible sail combinations.

    As for pointing: Split rig sailboats generally point around 4-5 degrees lower than a similar hull with a single rig. In a race start manoeuvering in the pack that's significant but in a seaway it’s immaterial.

    Why did the ketches stop being competitive……the Whitbread race was bought off Whitbread by Volvo and the rule was changed to a cheaper open design VO_70 rather than IOR. That favored the sloops and cutters again because of the max sail power to structure and rig weight. Kanting keels and single masted rigs on those boats became de rigueur. Nothing we can learn there for cruising boats though.

    Look at Dashews Beowolf for another performance cruising ketch. With those sort of designs looking at the polars the mizzen is fully contributing at 45 degrees off the wind. Some of the poorly designed cruising ketchs were better off without the mizzen till 60 degrees they gave ketches a bad name.
     
  13. Gary Baigent
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    Gary Baigent Senior Member

    This is a small but very light boat, 5.5 metres x 2.25 beam; the masts are very close together and theoretically this should be damaging for high windward performance ... but it's not. Maybe the rotating 6 metre wing masts make a difference? In fact I think they are the reasons for its speed and pointing ability.
    Although of little interest to the subject of this thread, the boat has the addition of T foils to daggerboard and rudder and the boat lifts off on reaches - which is very good fun.
     

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  14. rwatson
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    rwatson Senior Member

    How would they know ? Has it been tried with a more traditional rig ?
     

  15. Gary Baigent
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    Gary Baigent Senior Member

    "How would they know?"
    Because it has lined up and raced other similar sized and much larger designs and beaten them. People seem to forget how efficient the una (or double una) rig works. As said, the rotating wing masts are the reasons for good windward performance. On a reach, also fast when lifting onto its foils.
    Yes, with a traditional (albeit rotating) tall single mast the boat would be fast and high pointing to windward, maybe more efficient than the equal sized semi-schooner rig ... but also very tippy too. Sail area with the two masts is large, around 22 m2 and that area is carried low. Even so, it needs to be reefed early, around 12-14 knots.
     

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