Roach or No?

Discussion in 'Boat Design' started by BobBill, Jun 27, 2015.

  1. BobBill
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    BobBill Senior Member

    Idea, very slight luff roach for drive, NO leech roach.

    Means no battens etc...not racing, semi crab claw. Simple.

    Sound like a plan? Pic is idea, but has battens etc.

    I just do not see need for battens on such a rig...I also know that is a course less traveled.
     

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  2. Jamie Kennedy
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    Jamie Kennedy Senior Member

    When the Laser first came out Bombardier came out with their Invitation which was a similar bend mast cat rig, except that it had no battens. I don't know if it was the hull shape or the lack of battens but it would go ABSOLUTELY NUTS downwind on a deathroll. The mast would actually strike the water a few times before finally going over for good. There wasn't really anywhere in the cockpit to lock yourself in either. Good times.
     
  3. messabout
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    messabout Senior Member

    You will need some camber in the luff, which is not the same as roach, and the leech can have a roach or not. If the leech has a sizeable roach then battens are usually necessary. A slight concave leech can live happily without battens...........But that is only if the sail is cut and sewn with all the variables accounted for. The luff camber is calculated to set some shape into the sail but it must be cut such that the mast or whatever the luff is attached to is taken into consideration with regard to bend.

    I expect that you know all that.
     
  4. PAR
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    PAR Yacht Designer/Builder

    Luff round , as it's called is necessary on all sails, though bending and/or free standing more so. The amount of round, it's maximum camber location and other details are best left to some experience. There are quite a few variables has hes been hinted at by other posters. I just recently designed a sail, with luff, foot, gaff round and significant roach. I spent an hour and a half on the phone with the guy, who fortunately was on the same page as me, in regard to how to get the best shape, camber and round locations, etc. for the applications.

    As a rule, if you have anything more than a slightly hollow leach, you'll need battens to hold out the extra fabric, especially in certain wind strengths.

    I remember those early Laser rigs Jamie and I think the CE was intentionally moved aft a bit, with the stick shape and this caused a longer couple, with sheets well eased.
     
  5. Jamie Kennedy
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    Jamie Kennedy Senior Member

    I think where this sail is a semi crab claw it should work very well without battens. I might be inclined to design the boom to be a little bendy also, and sheet it mid-boom with a tight shallow bridle to spread the load. Much like an Optimist Pram boom.
     
  6. PAR
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    PAR Yacht Designer/Builder

    I'm not very familiar with all of the dynamics of the crap claw, but any kind of roach will curl over in certain conditions, without battens.
     
  7. BobBill
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    BobBill Senior Member

    Excellent advice. Thank you all.

    This spar will bend, a lot, in a breeze, even off the wind...

    I know it will need luff round or luff roach built in and sort of wondering if that might be only the lower half...?

    Have to talk to loft also. The boom will be flexy, and foot free...but the "line" traveler, is confined to stern and quite narrow, especially relative to the overall beam.

    Not a racing rig.

    Thanks for your input. A little bit of each will likely be part of final product...
     

  8. Jamie Kennedy
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    Jamie Kennedy Senior Member

    The Optimist sail is semi-loose footed. There are a few sail ties along the boom. Six as I recall not counting the tack and clew. I think this makes sense as it will help shape the sail evenly as the mast and boom both curve and straighten together. I like the rig. I am curious what you will have for a vang arrangement for sailing off the wind. Reverse thrust boom vangs seem to be in vogue, and might be very suitable for this rig. I know it is not a racing rig, but let's face it, neither is the Optimist, and it's still an awesome boat to sail when set up properly. :)
     
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