Aftmast rigs???

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

  1. Spiv
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    Spiv Ancient Mariner

  2. Spiv
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    Location: The Big Wide Blue Brother

    Spiv Ancient Mariner

  3. CT249
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    CT249 Senior Member

    But why believe "this guy" instead of all the thousands of other iceboat sailers who use bermudan rigs?

    It's also noticeable that the videos on the page that link leads to shows the other iceboats using 25 year old windsurfer rigs, such as a Division II "pinhead" sail and what appears to be a Point Rainblow "fathead" sail from about 1989. We Division II windsurfers stopped using the "pinhead" sails as soon as the rules were changed in 1989 to allow us to use modern cambered rigs which had much lower drag and allowed much higher speeds. It appears that they may not be comparing the crab claw sail to a modern bermudan rig or to a bermudan rig designed for iceboats and therefore it is not a valid comparison.
     
  4. brian eiland
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    brian eiland Senior Member

  5. brian eiland
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    brian eiland Senior Member

    Aft Mast experiment.jpg

    The 'main' is likely doing more than that as a helper,...but nice experimentation. BTW what are your sails made of?
     
  6. brian eiland
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    brian eiland Senior Member

    Atrocia – a study of experimentation, risk and failure....

    I have been looking, and looking, for a reference to this vessel, and a photo that I know was posted long ago on the internet. But I had forgotten her name !...and could not find it as hard as I looked. Tonight I found this blogspot reference, and a photo!!

    http://6metre.blogspot.com/2013/06/atrocia-study-of-experimentation-risk.html

    [​IMG]

    For years I have been told this rig design was a total failure, and thus a reason that my aftmast concept was doomed to failure. But I was NOT ready to accept results from one experiment as a reason for rejection.

    And now as I read thru this blog posting I can see that a lot of the failure was a result of other conditions at the time of the sailing trials RATHER than just the aerodynamics of the configuration.

    ha...ha...ha
     
  7. tgtony52
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    tgtony52 ...

    I bought the sail material online from https://www.radiosailingshop.com.au/index.php?main_page=index&cPath=15 .
    I got 5 metres of Poly362 NEW Poly/Mylar Film 36 Micron NOW 600mm Wide per metre (Poly362) for $AUD34.25

    i'm thinking of making a longer sail for my Nirvana, to come past the mast like a 130% or so genoa. This will require altering my servo to become a fully revolving winch in order to sheet in around the mast. A bit like this fantastic and very expensive model boat from Stockmaritime http://www.stockmaritime.com/premiu...navi1=394&navi2=0&navi3=0&detail=2&lang=en_GB.

    I've also sailed my model without the main and it sails just as well. It even has a weather helm contrary to what you might think. I noticed this as well on my 24' aft mast gaff cutter when sailing with only the two foresails (no main).

    Here is a link to a video I took of the Nirvana - https://aftmastgaffcutter.com/links?iframe=true&theme_preview=true
     
    Last edited: Feb 24, 2017
  8. markstrimaran
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    markstrimaran Senior Member

    Hope to go sailing soon.

    https://youtu.be/ViYOSpFsZZY
    This was as far as I got two summers ago. Last season I never masted, partly because the mast was holding up a tarp to protect the blackberry patch from a later frost than usual. I got lumber at the ready this year.
    So time to get the sewing machine going, and finish the jib stay sail, cutting it down to be self tacking.
     
  9. CT249
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    CT249 Senior Member

    Atrocia was designed to exploit a loophole in the same rating rules that you regularly complain about, Brian, so it's not necessarily anything more than a rule beater.

    The blog you linked to is incorrect in at least one significant respect. It is simply undeniably wrong to claim that "a typical spinnaker of the time looked like a billowy regular jib which was flown free with no spinnaker pole". Poles had been in use for years and spinnakers were quite deep, albeit normally sheeted to windward of the forestay.

    Sherman Hoyt explains why the mast had to be so heavy - it was a direct result of the lack of a normal mainsail (UK edition of his memoirs, p 182). It wasn't a case of poor engineering, merely good engineering meeting reality. He also mentions that in the UK, Nicholson tried a similar rig with similar results.

    It would be interesting to find out where the blogger found out that "Atrocia streaked to the lead in anything resembling a fresh downwind leg, only to be repeatedly thwarted by light winds throughout the week". According to Hoyt there was only one race that had a long run before a fresh wind, which indicates a rather different tale.

    Hoyt's autobiography also casts doubt on the claim that once Atrocia returned to a conventional rig she "did not perform well enough in the trials to defend the Seawanhaka Cup." Hoyt states (p 183) that he "did well with Atrocia, and in a short series against Clytie, the next leading contender, generally finished in the lead." He said that it was impossible to know whether he would have done better in the Seawanhaka Cup itself if he was sailing Atrocia.
     
  10. brian eiland
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    brian eiland Senior Member

    Did you access those memoirs of his on-line, or did you have a copy?

    And why would a straight up standing mast have to be that much heavier because it didn't have a normal mainsail?

    Oops, I think I found an answer to that question on that blog link...
     
  11. pogo
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    pogo ingenious dilletante

    I guess that the mast is so thick and heavy because of missing lower shrouds , four ; back and forward,
    or alternatively diamand stays.
    A thinner, lighter mast without lower shrouds will not stay in column, in a seastate it will pump.
    On the upper shown 6mR forward lower shrouds would collide with the jib-boom.
    A big mainsail , together with backstay and running backstay can more or less take over the function of lower shrouds (see flexible rigg on starboat , " invented" by Pimm von Hütschler ; world champion 1937)
    A small , not top mainsail can't take over lower shrouds' tasks.

    pogo
     
  12. brian eiland
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    brian eiland Senior Member

    I noted a couple of other 'problems' in trying to get performance from this new experiment vessel

    It had almost no tuning time !!
    Then this;
     
  13. brian eiland
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    brian eiland Senior Member

    And why couldn't it have been stayed better rather than resorting to a heavier mast? I mean this guy was a top designer for the times,...correct?
     
  14. brian eiland
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    brian eiland Senior Member

    Interesting Summation

    I think this quote from that blog is a reasonable summation of this 'failed experiment'....
     

  15. pogo
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    pogo ingenious dilletante


    Yepp, he was a top designer in that era, an era when diamond stays were unknown. ( the new maconi riggs showed the first jumpers - single spreaders !)
    Why he did't use lower forward shrouds i've written above. Collision w. jib-boom.
    It' a wooden mast. For a tiny mainsail a flexible mast ( starboat) makes no sense, the powerhouse is the big jib. For such a constellation less sack in the forestay is essential,
    the mast MUST stay in column !!
    So,
    without lower shrouds only common tech , well known prooved setups of that era, were the solution ---a thicker , heavier wooden mast.
    My conclusions.


    pogo
     
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