Huge roach control

Discussion in 'Sailboats' started by feetup, Mar 15, 2007.

  1. feetup
    Joined: Oct 2006
    Posts: 8
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: western Canada

    feetup seeker

    For the knowledgeable:

    The current trend toward absolutely enormous roach in mainsails found on the latest ocean racing designs seen in the VOR and Velux etc., and the massive square heads on many of the high performance cats has me wondering how twist is controlled in such a high aspect ratio sail with so much of it's area in the top half of the sail.

    Any thoughts?

    Feetup
     
  2. gggGuest
    Joined: Feb 2005
    Posts: 847
    Likes: 30, Points: 28, Legacy Rep: 76
    Location: UK

    gggGuest ...

    Full battens, stable sailcloths and plenty of leech tension.
     
  3. Doug Lord

    Doug Lord Guest

    Square tops

    The square top on small boats and dinghies(and AC boats) requires a fairly stiff upper mast section but allows you to control gust response
    with the vang w/o the complications of some rigs and their upper shrouds.
    The extra area is not really roach since a square head roach is measured from the upper aft point of the square top(peak in gaff terms). A square top can be supported by a modern version of a gaff and not even require full battens- a big advantage in some model sailboats. A modern gaff can also allow an upper outhaul that works identically to a "normal" outhaul-ideal on models but a little complex on full size sails though it can work real well.
    A square top is not only aerodynamically superior- it represents a simple form of automatic( with an adjustable range ) gust response.
     
  4. Hansen Aerosprt
    Joined: Mar 2007
    Posts: 62
    Likes: 0, Points: 0, Legacy Rep: 29
    Location: SF Bay

    Hansen Aerosprt Junior Member

    Wyliecat 17
    Big sail, small boat, simple rig.
    Extremely fast in light air and a blow...
     

    Attached Files:

  5. Mychael
    Joined: Apr 2006
    Posts: 479
    Likes: 14, Points: 0, Legacy Rep: 125
    Location: Melbourne/Victoria/Australia.

    Mychael Mychael

    So what would it mean in terms of sailing and handling to use that type of sail shape (I've heard the term "fathead main" used) with a conventional rig and not changing anything else?

    Mychael
     
  6. Hansen Aerosprt
    Joined: Mar 2007
    Posts: 62
    Likes: 0, Points: 0, Legacy Rep: 29
    Location: SF Bay

    Hansen Aerosprt Junior Member

    Would depend on the boat and rig. Some better than others. Lots of variables to consider like mast bend, back stays (or not), righting moment, keel and rudder type, placement and size. Generally speaking, a typical pinhead mainsail is inefficient in many ways not only in an aerodynamic sense but with respect to rigging and mast length. IMHO, a 'chop top' would probably improve most any boat, jib headed or uni-rig (cat) if you could work around any conflicts with the standing rigging.
    - Bill Hansen
     
  7. Mychael
    Joined: Apr 2006
    Posts: 479
    Likes: 14, Points: 0, Legacy Rep: 125
    Location: Melbourne/Victoria/Australia.

    Mychael Mychael

    Okay.Now bearing in mind I'm only an owner and have no design skills all I can give you is general information about my boat. So Here goes.

    Fixed fin keel, spade rudder,26feet LOA. Masthead rig conventional, ie not gaffer or anything else.
    Loose footed main. Adjustable tension backstay, standard forestay and adjustable tension inner forestay.
    Selection of genoas from 120% down to storm jib.
    Weather helm if too much wind for main (before reefing or sheeting out).

    I soon have to replace my main, can you give me an informed opinion with the information I've given you as to how a "fathead" main might work on my boat.?

    Mychael
     
  8. Hansen Aerosprt
    Joined: Mar 2007
    Posts: 62
    Likes: 0, Points: 0, Legacy Rep: 29
    Location: SF Bay

    Hansen Aerosprt Junior Member

    Your main obstacle is the backstay. You would need to replace it with running backstays, at least under way with a full main. Reefed down in a blow you could have a fixed backstay depending on the size of the 'chop top.' If your rig depends on a highly tensioned backstay to keep the mast in the boat, it could be problematic. An alternative staying arrangement which supports the mast without high backstay loads would need to be added. Other than the hassle of running backstays in tacks and jibes, your boat handling would be pretty much the same and light to medium performance would improve.
     
  9. Mychael
    Joined: Apr 2006
    Posts: 479
    Likes: 14, Points: 0, Legacy Rep: 125
    Location: Melbourne/Victoria/Australia.

    Mychael Mychael

    So if I had swept spreaders and no backstay then it would work? I doubt I'd want to make that many changes. My boat has dual spreaders but they are straight.

    Mychael
     
  10. Mychael
    Joined: Apr 2006
    Posts: 479
    Likes: 14, Points: 0, Legacy Rep: 125
    Location: Melbourne/Victoria/Australia.

    Mychael Mychael

    I just looked to refresh my memory how a running backstay works. I recall now as my mates Dragon had them. Just more work for a single hander and they refer to fractional rigs, my boat is masthead so I assume a running backstay would not work even if I wanted them.

    Mychael
     

  11. Frosty

    Frosty Previous Member

    When I got my new sail from Hong kong and I opened the package I was shocked at the huge roach in the sail they had sent me. I did not order that!!


    Any way it was already dead so I just flicked it way with a stick.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.