A-class mast rotation

Discussion in 'Multihulls' started by bad dog, Sep 7, 2010.

  1. bad dog
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    bad dog bad dog

    Hey all A-cat sailors,

    What's the best mast rotation system? (What kind of a question is that?!) I know there will be several different views, and let's have the technical arguments!

    The reason I ask is that I am setting up mine from scratch, and am not sure which way to go, not being tied to any particular system - the platform is a Mk4 Boyer, with a carbon Saarberg mast and who knows what in between.

    Photos would help, if you can post 'em.

    Thanks,
    Bad Dog
     
  2. nickopen
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    nickopen New Member

    What options are there, really?

    Everyone used to have the mast-to-boom spanner setup (I know it's not an a-class, but it was easier to find this photo of an F14):

    [​IMG]

    But looking around on the web, everyone seems to be using a mast-spanner to a hole-in-the-tramp setup, only now I can't find any good images of them.

    If people are using another setup, I'd like to know. I also have no idea why everyone moved to the hole-in-tramp setup either, the mast-to-boom setup seems more efficient and usable to me.
     
  3. Eralnd44
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    Eralnd44 Wanderer

    then how is it now that question is strong?
     
  4. bad dog
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    bad dog bad dog

    Nickopen - I also found few pics on the web. Two I did get are of AHPC's setup on (possibly) the Taipan, which poses more questions for me than it answers;

    and one of an F16 Falcon, which is what my A currently has and it does not work: the free ends need to be on an endless loop, otherwise on a port rounding course, you end up always feeding out from the starbd side and quickly run out of slack and travel. A mate's Mk5 A has a similar system but with endless loop and it works well.

    I'm not sure how easily you would get full mast rotation with the boom connection device - can you explain? As it is now in light air I push my foot against the boom to hold it out. No probs in stronger stuff.

    Eralnd44 - sorry, I don't quite understand your comment - English is my second language (I'm Australian). ;-)
     

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  5. Pouakai
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    Pouakai Junior Member

    Dog, I have Falcon F16 - could even be my boat pictured.

    You overcome the running out of slack by building in a quick release system - that is what you seeing on the Taipan.

    I'm just updating my system now to the quick release version.

    You still have the hole in the tramp with the line going to a block on the end of the spanner, but instead of tying the block to the end of the spanner, then the line goes to a cleat either on the spanner itself (Taipan and Viper) or on the mast (Falcon). Hopefully you can see it in this image.

    [​IMG]

    So, now the rotation line is only used for fine adjustment and you use the quick release to go from upwind to downwind mode.
     
  6. bad dog
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    bad dog bad dog

    Thanks Pouakai, I get the concept but the photo is too lo-res to make out the detail - can you post again in hi-res?
     
  7. Pouakai
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    Pouakai Junior Member

  8. mcollins07
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    mcollins07 Senior Member

    May I ask what are the specific challenges?
    As with any mast the materials and strength/weight, but in addition?
    1) the load carrying bearings?
    2) controls?
    3) supporing rigging?
    4) ...?

    ~ Michael
     
  9. bad dog
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    bad dog bad dog

    Thanks for the extra info there Pouakai.

    I'm guessing that after releasing the quick-release, you have to go fwd at some point to pull it tight again?? - isn't that a pain?
     
  10. Pouakai
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    Pouakai Junior Member

    On a F16 you are getting your hands forward anyway to drop the kite, so its not a problem. Haven't sailed an A so not sure what your rounding sequence is, but I would be surprised if you didn't get to within an arms reach of the mast during the rounding.

    If you don't want to or can't get forward on an A, then maybe splicing to rotator adjustment together so it is endless might be the better (and cheaper) solution.
     
  11. Pouakai
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    Pouakai Junior Member

    You also might want to do some searches on the catsailor.com forum, there is loads of stuff there on A Class mast rotation.

    Looks to me like you also need an 'over-rotation' system so you can get 90 degree + rotation downwind. Not needed so much on a F16 as our traveller remains centred downwind as the kite generates the apparent. Although in really really light winds it would help. But how much extra string do you want a solo spin boat?

    Looks like it gets pretty complicated once you factor in over rotation! Good Luck.
     
  12. nickopen
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    nickopen New Member

    It's a mechanism that seems to work well on things like Tasars, NS14's and MG14's (which is where I've used it), and I've seen some old cats use it, but people have moved away from the system so there must be some advantage in the current mast to tramp setup over the boom system - I just don't know what it is!

    Basically, you set the length of the connecting line between the boom and the mast spanner to define your mast rotation, and the mast rotates further out as you let the boom out (so you don't have to adjust it as much). You can still set it up so that the mast is pointing across the boat with the boom in the centre and run lines out to the sides if you want, but normally people just leave it on the boom and only change it at mark roundings.

    In light air I think you always have to lean on the boom to keep the mast rotated out unless you have one of those ridiculously tight bungee setups pushing the boom against the mast and rotating it around, but they are a pain when tacking and gybing.
     
  13. bad dog
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    bad dog bad dog

    Ok thanks all, these are interesting ideas. I will check out catsailor too.

    The possible problem I would have resetting a QR on the spanner is that we have no reason to go into the centre unless gybing or tacking, so when rounding the bottom mark on the same tack (usually port roundings in our club racing) I simply want to pull everything in to the close hauled position while heading out on the wire. I do have to pull the outhaul on the boom, but the less time spent doing stuff the better.

    The other side of that coin is that I suspect it may be quicker resetting a QR than pulling an outboard control line through the cleat... hmmm - might have to do a time & motion on this!
     
  14. Pouakai
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    Pouakai Junior Member

    It's definitely quicker, that's why I'm installing it on my boat. Then you just use the cleat for fine adjustment from the wire.

    For the cost of another turning block you could run the quick release down your boom, so your QR and out-haul are in the same place. You could even link them together so a single line did both.
     

  15. powerabout
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    powerabout Senior Member

    Check out the latest Nacra 20 and or a Tornado
    They have tramp mounted systems with 2 settings so the crew can dump to full rotation downwind and at the bottom mark there is a preset to go back to your upwind setting.
    Best system Ive seen/used.
     
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