Details of a canting rig

Discussion in 'Multihulls' started by bruceb, Nov 26, 2009.

  1. bruceb
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    bruceb Senior Member

    How do you engineer a canting rig? I have a small tri- 240 square foot main, and I would like to make the rig "cant". How do you size the stay adjusters set-up, how much tilt, what sort of blocks etc? I have not found many details on line. does anybody have some thoughts? B
     
  2. TeddyDiver
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    TeddyDiver Gollywobbler

    Why on earth?
    Sounds tricky to be done with stayed mast.. think it's lot better to go with self standing with hydraulic adjustments .. my 2c
     
  3. Doug Lord
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    Doug Lord Flight Ready

    canting rig

    Canting the rig can increase speed and such rigs have been used on many racing tri's and monohulls. Some race boats cant the rig and change the rake.

    Defining features of 3rd Generation:
    o Improved technology and methods of construction
    o Nomex/pre-preg carbon construction, vacuum bag cured at 120°C
    o Trimarans lighter and stiffer.
    o Fitted with transverse canting-masts with hydraulic shroud rams concealed in the floats
    o 12 Metre-style ram at the outboard boom end controls outhaul tension.
    o Composite forestays fitted with hydraulic rams to adjust mast rake.

    I'll keep looking and see if I can come up with some details. Are you doing this to improve racing performance?
     
  4. bruceb
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    bruceb Senior Member

    Kiss

    This is a Small! tri-no hydraulics. I have single side stays, very simple. I know several under 30' tris have canting rigs, with definite performance improvements. I want to know how, what with and when. I am ready to replace my side stays and this seems like a good time to upgrade. B
     
  5. Tom.151
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    Tom.151 Senior Member

    how much tilt - might first be governed by your mast step - either geometrically or structurally so that's the place to begin

    blocks - whatever you use matters less that having a runaway strap/line that bypasses all of the running parts and limits total length in case of either breakage or accidental release - make sure there are no shackles involved in the runaway link;)

    as for sizing the bits and pieces - you need to just make sure you size at least for the weakest link in the existing system - canting the rig doesn't really increase the stability (righting moment) of the boat so the max loading doesn't increase - the canting just points the sail force vector fouther forward or upward, that's what produces the increased speed after all.

    A place to start to guess for the mechanical advantage needed for the blocks would be to calc the max stability load on the shrouds then decide what the max line load you can tolerate and still be able to adjust the rig. You might need a coarse/fine type system - where a 4:1 system is used to amplify a 6:1 system. But keep in mind that you don't necessarily need to adjust under max load conditions (adjust while tacking/gybing for instance).

    When you get it done come back and show us what you decided.

    EDIT: I'm just now remembering the old Brown/Searunner trimarans and their huge 'highfield' levers used to tension their running backs. That approach might greatly simplify the canting gear setup- especially if you decide that you don't need infinitely adjustable canting angles.
     
  6. Corley
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    Corley epoxy coated

    I can remember samnz mentioning he had/has a canting rig on his Bucc 24 and some details of how it operated might be worth searching through his posts
     
  7. farjoe
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    farjoe Senior Member

  8. bill broome
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    bill broome Senior Member

    i saw a vid of a kite sail a few years ago on a cat about 8 m long. it was pinned at the center of the luff spar to a stub mast and tacked by bringing the lee tack down to the boat with a guy. the process quite resembled the old skate sailing with the whole sail flying over the mast.

    the mast is fixed in place, only two guys and a sheet for running rigging- looked easy.
     
  9. bad dog
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    bad dog bad dog

    It is definitely worth doing!

    I had a Catapult (16' cat) with a canting rig - in fact they all have them, but I also set it up with an adjustable forestay, as shown in the excellently instructive video of Firebird. I had no running backstay adjustment, just straight line shroud sortening/lengthening.

    The shrouds were on a 6:1 system which was impossible to work when loaded - the trick was to anticipate the degree of cant required before loading. Maybe 8:1 or more would be needed on your bigger rig. It also required some choreography to cant from side to side during a tack or gybe! I fantasised about a hifield lever but could never figure out a practical mechanism on a small cat - maybe the tri is big enough.

    I used 6mm rope and a connected system, so the line crossed the tramp from block set to block set. This reduced the confusion of free ends everywhere, as when one side was in the other was out, so it more less balanced.

    The mast step is an issue, but if you use something like a Hobie or A Class ball-in-cup or similar, it will give you all the canting you need - usually 5° is enough.
     
  10. bruceb
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    bruceb Senior Member

    more details

    Thank you BD, details are what I need. My mast is stepped on a 2" ball so it can tilt any way necessary. (A Stiletto 27 rig) Five to seven degrees seems about right- about half of the heel. I will have to work out the total expected loads, but an eight to one seems about the max purchase. I hope some more sailors with actual experience can chime in. I think it will really help. Thanks, Bruce
     
  11. bad dog
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    bad dog bad dog

    Bruceb, here are some pics, unfortunately I don't have close-ups of the canting hardware, but you can get some details at http://www.catapultcats.com/
     

    Attached Files:

  12. bruceb
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    bruceb Senior Member

    More details

    Both the Catapult and the Orion pics are great. The videos of the Orion have a lot of detail that is going to take me a while to digest, but it looks as if it really works well, and on a boat and rig about the same size as mine. 20 kts under decent control looks pretty good also:) Bruce
     
  13. phildowney
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    phildowney phild

    i saw the link above with the firebird orion the canting rig option has a unique safety feature i never apreciated, in conjunction with a mast tip float , canting the mast makes the boat self right!,

    whatch the vid on youtube its amazing, i would fit this to any cat i owned in the future since i dont sail cats because though great fun im 10 stone and would strugle to right it.
     
  14. bruceb
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    bruceb Senior Member

    self-righting cats

    The Orion's seem to have many nice details of design that seem to work well. It looks expensive:mad: A righting kit used to be available for Hobie's back in the 80s and early 90s, (might still be available) pretty simple to add and it worked well. Light crew or a single person could pull one pin on a side stay and the cat would almost right its self. Very easy to fit to most beach cats. My tri is probably too wide and heavy for it to work though. B
     

  15. bad dog
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    bad dog bad dog

    There's another thread here from a couple of years ago on self-righting multis... somewhere...
     
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