Head boards for head sails

Discussion in 'Multihulls' started by noodle, May 6, 2010.

  1. noodle
    Joined: Feb 2008
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: australia

    noodle Junior Member

    Square head mains seem to have advantages over pin heads so how about squarish heads for head sails?
    My main interest in this is because I'm soon going to order a 'jib' for a Farrier F82 but it will be a free flying furling jib. This seems to indicate a large luff hollow and, without battens, a large leech hollow. The overall effect could look like a fishing net hanging in the breeze :)
    The trend seems to be for more roach supported by either leech (non furling) or vertical battens. Instead of several vertical/leech battens supporting the difference between hollow (-150mm) and roach (+150mm), how about just one vertical batten supporting a square (maybe elliptical) head of 300mm and a conventional leech hollow below so no extra battens needed?
    The upper section of the head sail gets to do something useful maybe.
    Need to furl for tacking - OK.
    How to distribute the batten load into the sail?
     
  2. fhrussell
    Joined: Dec 2004
    Posts: 156
    Likes: 2, Points: 18, Legacy Rep: 30
    Location: Long Island, NY

    fhrussell Boatbuilder

    I think it's an interesting idea and looking forward to hearing opinions from those who are more knowledgeable on the topic!
     
  3. Doug Lord
    Joined: May 2009
    Posts: 16,631
    Likes: 311, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ==========
    I've experimented with a square top jib on several models and on one 16' foiler. Has a lot of promise. I used a straight carbon "gaff" at the head of the jib(no diagonal batten) with the halyard attached about 30% aft of the leading edge-this point was adjustable fore and aft. The Peak(gaff terminology) or "upper clew" was adjustable but in practice didn't make much difference. For future reference full size I'd go with a bigger head/gaff combo.

    model and full size examples:
     

    Attached Files:

  4. Chris Ostlind

    Chris Ostlind Previous Member

    While the examples shown above do represent a negligible enhancement of sail area, they do, very much, represent an excessive amount of complexity added to the mast head of any given rig.

    Now, instead of a simple block setup for hoisting, (or going fractional, like many of these rigs) you also have the addition of a rather substantial bearing surface which will require maintenance well beyond that of the simple block.

    Additionally, there is a need to run calcs on the moving arm of the forward/aft gantry to make sure that it conforms to load requirements.

    The whole thing represents a cosmetic attempt to do something that is already being done with mainsails and the benefit is dubious at best.

    Why not just run a really clean, hard sail wing on the boat and completely do away with the business of screwing around with all the fiddle-faddle represented in the forward/aft gantry?... if you want to have performance in a tidy package ;-)

    Of course, the boat has to be somewhat proven as a design that will actually do what it is supposed to do, (ask the designer above if the boat could actually generate enough power to get up on foils and could he be so kind as to provide photographic evidence that this actually happened) and the potential for the boat being crashed with some frequency has to be brought to bear within the design process.

    Keep it simple, focus on clean design process and if you feel the urge, go after one change at a time, so that you can see the result very clearly. Ditch the changes as needed and perhaps, move on to another conceptual approach after that. The design shown above tried too many departures from the existing norms all at once and the designer probably got confused as to what may, or may not, have caused the failure of the craft's design goals, mostly because they were too numerous to iterate in a cohesive correction.

    Simple is always better.

    A quote that is frequently connected with Team Lotus F1 and commercial automotive designer, Colin Chapman, is appropriate here...

    "Simplicate and add lightness"

    It worked in the 60's amd 70's and still works today.
     
  5. Paul B

    Paul B Previous Member

    If you do want to go upwind you won't want a "big head", since that would just close off against the mainsail when sheeted in.

    Seems to me the Code Zeros many boats use today don't have the luff hollow or leech hollow you talk about. In the photo attached you can see Puma's Code zero with very straight luff/leech. Of course you'll need some purchase to get the luff tight enough.

    The AC boats were using bigger roaches on the jibs, but as you say that requires battens. Those boats were using inflatable battens. I think you can do well with vertical battens these days for furling sails.
     

    Attached Files:

  6. Doug Lord
    Joined: May 2009
    Posts: 16,631
    Likes: 311, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ----------------------
    1) That is simply false. The jib and the main are hoisted in the same manner as any other sail.
    Benefits of a more rectangular planform vs a triangular planform are not speculative-they are well proven.
    2) Tom Speer said that the wing on USA was more like a sloop rig. That would be a sloop rig with a square top jib....
    right here: http://www.boatdesign.net/forums/multihulls/why-so-stable-31516.html post#7
     
  7. Chris Ostlind

    Chris Ostlind Previous Member


    Hoisted the same? OK, they may be HOISTED the same... But, which rig has more parts, Doug? Your gantry-cantilevered setup, or a conventional fixed hound with but a simple hoisting block? Complexity is about the number of maintenance oriented parts, as well as the manner in which a system is utilized.

    As to the benefits of a rectangular planform vs a triangular version... the jury is out and not even visible on that topic when it comes to headsails.

    How about this for a challenge... you go and take an inventory of all the major, truly fast, multihulls and monohulls on this planet and let us know, by percentage, just how many of them are sporting square head planforms. Don't bother with the less than banging boats, because they won't adopt a thing until the race boats do it first and show it to be appropriate.

    We can wait for the results, because it will take forever to find anything along those lines compared to the existing installed base. When you come back with the representative percentage that shows just how WELL-PROVEN this thinking might be, please bring it to our attention.
     
  8. noodle
    Joined: Feb 2008
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: australia

    noodle Junior Member

    Would a 'big head' behave as well as a big roach if it was well supported?

    I speculate that the large headsails in those photos are not free flying but supported by a well tensioned forestay so there is little luff sag and little need for hollow. In any case the object is to prevent the luff from sagging laterally and it is easier to do that if tensioning a hollow than if tensioning a straight member. The downside to the luff hollow (~1.5-2%)is a significant loss in sail area (~%5)
     
  9. noodle
    Joined: Feb 2008
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: australia

    noodle Junior Member

    Great to see some serious experimenting. It is way easier to talk about it than to do it.
     
  10. Doug Lord
    Joined: May 2009
    Posts: 16,631
    Likes: 311, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ----------------
    Some mini 6.5's have recently experimented with a square top jib-so far I can't find a picture.
    This stuff is certainly worth experimenting with! The gains could make it worth it. Besides it's fun doing something nobody else has.....
     
  11. noodle
    Joined: Feb 2008
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: australia

    noodle Junior Member

    I'll try to find one, true enough about the fun bit. This is a photo of my F82, almost ready to go.
     

    Attached Files:

  12. Doug Lord
    Joined: May 2009
    Posts: 16,631
    Likes: 311, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    --------------
    Wow! She looks great-one hell of a job.... Good luck and good sailing!
     
  13. Stumble
    Joined: Oct 2008
    Posts: 1,896
    Likes: 71, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    Looks great,

    only problem I see is all the holes in the cockpit where old hardware was attached... But I figure you can fix that over time.
     
  14. noodle
    Joined: Feb 2008
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: australia

    noodle Junior Member

    That's why the idea is to take the photos before everything gets broken or relocated :)
     

  15. Paul B

    Paul B Previous Member

    Your speculation is incorrect. The sail I mentioned, PUMA's Code Zero, is set on a fulrler out to the end of the sprit. It has an internal luff rope that is tensioned to keep the luff tight.
     
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.