Aftmast rigs???

Discussion in 'Sailboats' started by jdardozzi, May 28, 2002.

  1. brian eiland
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    brian eiland Senior Member

    I was just running back (pun) thru this subject thread looking for something else, and ran across this posting again. I've quoted it here so I remember to take a fresh look at your mizzen mounting idea.
     
  2. sharpii2
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    sharpii2 Senior Member

    Gee, Brian, I take this as quite a compliment.

    Attached is the drawing, so you don't have to dig it up.
     

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  3. CT249
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    CT249 Senior Member

    I thought it had been already agreed around here that the claim that the mast destroys the efficiency of a mainsail is wrong? In that case, why go for hoops and a jackstay (which will involve considerable compression loads)?

    What is the advantage of dropping a boomed sail instead of reefing it? In my limited experience I found dropping a ketch's mainsail a few hundred miles offshore was a PITA. You had to try to furl a sail sticking several feet above the deck onto a boom, while the wind got under it and flogged it around. Reefing the main or dropping a jib was much easier.
     
  4. sharpii2
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    sharpii2 Senior Member

    In your case, did the mainsail have lazy jacks?

    If it didn't, I couldn't agree more.

    With Lazy Jacks the sail is more or less contained, so the wind really can't blow it around.

    From sitting at my desk, I can imagine it is far easier to lower a sail, which is then contained by Lazy Jacks, than it is to slab reef it.

    On my Siren 17, I found reefing the Main to be a PIA.

    I had to lower the sail, pin in the new Tack, tie in the new Clew, then bundle up the rest of the mess. All of this while I'm riding the swells up and down, like an unstoppable elevator, and the sail is fluttering like mad.

    If I had bothered to rig Lazy Jacks, the whole operation would have been so much easier, but still there would have been the bit with the Tack, the Clew, and bundling.

    By simply dropping the sail (made possible with the Mast-aft Cutter rig), I reason, I eliminate two of these three steps, leaving just the bundling.

    As for the Jack Line, I reason it allows the Luff of the sail to somewhat end up on the lee of the mast. This is all the more important when you have a very tall, narrow main, and a fat compression tube for a Mast.

    I keep in mind two things with my reasoning:

    1.) the Jack Line holds only about 25% of the Main's area close to the Mast. The Hoops hold the other 75% of it. The Hoops hold not just that portion of the Sail Area there, but about half of the Jack Line as well.

    2.) The Jack Line does add compression to the mast, but about 40-50% less than a single-part Halyard would, if it were trying to do the same job.

    I know that in racing Lazy Jacks are rarely used, as they do cause some unwanted drag. And there are usually plenty of hands available, in proportion of the size of the boat too. In cruising, the crew is usually smaller and often far more tired, as they tend to be older and less able.

    Durable, simple, and easy to repair, labor saving devices, such as Lazy Jacks are well worth the few percent loss of performance they may cause on a cruising boat. In fact, they might actually add performance there, as the labor they save makes the crew less tired and able to perform better.

    Attached is a sketch of a ketch rig design of mine, showing the Lazy Jacks, in case some thread followers don' know what they are. These are the spider web like lines crossing the Main Sail. Now that I look at it, that rig could use at least one more Lazy Jack, leading to the middle of the Boom.

    Also attached is a sketch of my Mast-aft cutter, so readers can see that the 'Main' can be simply dropped, if the jib is too.
     

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    Last edited: Sep 13, 2016
  5. CT249
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    CT249 Senior Member

    Nope, that main didn't have lazyjacks and yes, they can certainly help.

    With respect, the Siren's reefing system seems outdated. You can easily fit a reefing system that uses just one reefing line, or perhaps a reefing line and a tack downhaul, which allows very easy reefing. On a 30-something footer the tack line can just be the cunningham; a 4mm going through a tackle. The clew line just involves winding in 6' of 6mm, which is mostly pulled in by hand. No big deal.

    In comparison, dropping a jib means going onto the foredeck, pulling it down manually and then lashing it. No big deal either, but arguably no easier.
     
  6. sharpii2
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    sharpii2 Senior Member

    Actually you don't have to go up on the fore deck to bring down a jib.

    A Down-Haul works quite well. And once the Head is down on the deck, the sheet line can be pulled tight. Yeah, it would be a good idea to bundle it up, but that doesn't have to be done right away.

    I can imagine, in a squall situation, the jib and tiny main could be pulled down, with the jib sprawling on the deck and the Main cradled in its Lazy Jacks, to wait out the squall. Then they could be hauled back up, with the crew never leaving the Halyard station.

    I think about things like this a lot, as I like to design tiny boats which might have to face a wide variety of wind strengths.

    With tiny boats, reefing can be a problem, because the skipper is often the heaviest item on board, and can even be heavier than the boat itself. If he/she has to move far from his/her ideal position, the boat's for-and-aft trim can be affected dramatically.

    Even with the small gaff headed ketch, shown in my last post, which should tip the scales at about 3,000 lbs, all-up, I don't want the skipper going to the extreme bow to take in the jib, or straddling the pointed stern, to take in the mizzen. The jib would have a down-haul and the mizzen would have a Clew out-haul, combined with braille lines, so it would furl to the Mast.
     
  7. CT249
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    CT249 Senior Member

    Yes, it all depends on your background. I don't leave the jib loose on the foredeck when it's getting rough, even if the sheet is tight and it's hanked on. The leach can still flog and there's too much chance of a wave breaking over the bow, filling up the furled jib, and destroying the stanchions. That's the reason reefing jibs went out of style, and it happened on at least one boat I sailed on.
     
  8. brian eiland
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    brian eiland Senior Member

    Are Genoas a Thing of the Past

    ...a few excerpts from another forum discussion...

    (Brian's note: Hmmmm,...another case of rating rules designing our boat :eek::D:rolleyes:)


     
  9. brian eiland
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    brian eiland Senior Member

    I believe it was my contention that the mast at the leading edge of a mainsail offered a considerable hindrance to efficiency of the mainsail:
    Now it has been subsequently shown (by Mikko) that the mast in some cases does not offer as much hindrance as I once pronounced. And that having the sail attached to rear portion of the mast decreases the drag forces that might be experienced in a 'bare mast' situation.

    But in the overall scheme of things a minimal size mast tube at the leading edge of the sail would certainly be beneficial in most cases. And the size of the mainsail behind that mast would be another important factor. If this attached sail is relatively small (as might likely be the case with a mizzen sail), then the leading edge dynamics should be reviewed anew. As the sail behind this mast tube is made ever smaller, its effectiveness (efficiency) becomes more problematic.

    My mizzen sail is mounted onto a nice rigid foil which I believe is superior to having a much bigger mast section at that leading edge.

    As an alternate I willing to consider Sharpii2's idea of this mizzen sail attached to the mast via hoops. What I find interesting here is that it would allow the luff of the sail to migrate over to the lee side of the mast tube, thus allowing for a cleaner airflow over the lee side of the mast-sail combination.

    We all know that its the lee side airflow that is most important in our sail settings. I seem to recall that a form of this idea has proven superior in the past, but I can't exactly remember were it was documented. The one somewhat similar example I can think of is a rotating mast configuration where the attached mainsail streams off the effectively 'lee side' of the mast tube.

    I can not see where a hoop mounted sail would add that much more compression loading to the mast over a normal halyard hoisted sail.
    My mizzen sail's halyard loading would not have to add much additional loading at all, since it is already on a very highly loaded stay already.
     
  10. CT249
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    CT249 Senior Member

    Windsurfers have been using RAF ("Rotating Assymetrical Foil") sail designs that allow (or actually force) the luff to migrate to the lee side since about 1984. They are slower than camber-induced sails, where the luff is behind the mast.

    The hoop idea started to die out almost 100 years ago. As the Star class history says, as soon as the marconi came along and sailors could use slides instead of hoops on the mast, they did. They then found that "the track and slide idea was so convenient it was applied to the boom also." Other classes did the same. They wouldn't have modified the boats if it made them slower.

    The reference to compression loads was about Sharpii's idea of a stay behind the mast, to which the mainsail luff was fastened. I'd have thought the triangulation of forces would have lead to great compression loads being applied to the mast, but I'm not an engineer.
     
  11. brian eiland
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    brian eiland Senior Member

    Adapting to getting older

    Just discovered this subject thread on another forum


     
  12. sharpii2
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    sharpii2 Senior Member

    Good point. Thank you. I can see now, that if I turned downwind, with the jib on the deck, it could fill with wind from the leach. And I wouldn't be able to do much about it, other than turn upwind. If a wave were to come on deck at that time, it could be disaster.

    Actually, a good roller furling jib would be best, if one of sufficient quality and durability could be afforded. But it must work in even the worst conditions.
    If that was the case, a straight masthead sloop would have much to recommend it. The inner stay could be eliminated, the Mast could still be back, close to the cockpit.

    My Siren 17 had what was called a 'spool furling' system for its jib.

    The jib had its own wire luff, didn't hank onto the fore stay, had a swivel on top and a cordage drum on the bottom. It routinely jambed. But I was always able to set the boat on a stable course, crawl up front and un-jamb it, then use it to furl the jib, while I was near the helm. I suppose it earned its keep, for this reason. If windy weather was expected, I simply left the jib furled and sailed under the main alone. This is one of the reasons the 3/4 rig is my favorite version of the Bermuda Rig.

    In defense of my Down Haul idea, the jib or stay sail could be hauled down to the deck, the boat could be turned onto a stable course, then the sail in question could be secured. The argument for this is this process could be done after the sail has been shortened, and while the boat is presumably under better control.

    Were jibs with reef points ever used in racing?

    I thought headsail swopping was the usual order of the day.

    In the cruising world, I know they were replaced with roller furling gear.
     
  13. brian eiland
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    brian eiland Senior Member

    Adapting to getting older

    another quoted posting from that other subject thread

    That reefed mainsail of his might just be the same as my 'mainstaysail', and my 104% genoa could be partially furled to account for winds in the range of 5 to 25-30 knots.
     
  14. brian eiland
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    brian eiland Senior Member

    I was just reviewing this subject thread titled 'Main-Less Rig', and found this particular posting:
     

  15. brian eiland
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    brian eiland Senior Member

    ...and another posting from that other subject thread....


    Then the reply from owner of a Catana 471:
     
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