Self tacking jib

Discussion in 'Sailboats' started by Paul Scott, Jul 21, 2008.

  1. Butch .H
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    Butch .H Senior Member

    Omeron good come back LOL. Lots of wierd things on this boat. I am rebuilding and will post a few pics
     
  2. Omeron
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    Omeron Senior Member

    Good luck mate,would love to see you progress and ofcourse the pics.
     
  3. rwatson
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    rwatson Senior Member

    Hi Omeron

    Yeah, I got pretty excited myself. The sprit isnt required, just happened to tack it onto something else I was working on.

    I had the vision of making it removable by running a steel 'axle' from the bowsprit or deck to the bottom of the reefing drum.

    The boom or whatever has a verticle groove with some sort of tube running up it, that has this axle running through it. The tube gets bolted to the boom with, say with U bolts (or something a bit more elegant) like a car axle, allowing it to rotate, but enforcing horizontal attitude.

    I did indeed see the possibility of flying an asymmetrical off the front - I was sketching fittings for it all day today.

    Remember folks - you saw it here first :)
     
    Last edited: Jul 30, 2008
  4. Paul Scott
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    Paul Scott Senior Member

    Matt, I actually thought of something in the same vein. Talked to Mr. Perry about the idea (for about the 5th time, you'd think I'd learn), and he likes the idea of a full width athwartship jibtrack. Nothing less, My cabintop is too narrow. In otherwords NO.

    That and the cabin is 17" high. Yikes!

    I would love a Hoyt boom, but my foredeck person (aka my wife) would not. However, when the boat was built, I had Mr. Rander build the bow as if a Hoyt boom would be installed. So it might just be a matter of time......:D

    And yes, the boat would be easier to sail, and I would never miss tacking on a gust cell again. :p

    Paul
     
  5. Hansen Aerosprt
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    Hansen Aerosprt Junior Member

    Paul:
    How about a small wishbone on the jib and a single sheet to the C/L? No track, self vanging and something to drop the sail into when the day is done. Could be elegantly made in low-drag profile out of carbon fiber. Give you something to hang onto up there too...
     
  6. alan white
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    alan white Senior Member

    No need for a full wishbone. I built one with a single curve on one side. In spruce a 100 sq ft jib boom might weigh 5 lbs.
    One real advantage I liked was adjustable draft. Another was ease of poling out the sail (helps to have a point forward like a sprit, as I did, to rig a preventer).
    Mine was a T section with the tee stem out and sideways, and tapered like a long banana.
    It also had a bridle attached to prevent its dropping onto the deck when the jib was struck. The inside curvature of the spar ensured the sail never contacted the boom.
    Using this setup, I commonly reached at up to 6.9 kts on a 18 1/2 ft waterline, and this on a stubby (S-2 7.0) 3600 lb cruiser. This bettered the former 6.2 kts formerly achieved.

    Alan
     
  7. Paul Scott
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    Paul Scott Senior Member

    I really like that idea. (The single spar idea too, Alan) It also demonstrates the braces on my brain when it comes to postmodern approaches to what I would call traditional solutions. I could get rid of the foil, the furler, whisker pole etc., which would be win-win. Could go with an aero hank on system too, now that I think on it. Never get ripped luff fabric from the foil feed again.

    I also could have asked you, Mr. Hansen, if you do jibs. I am embarrassed. I apologize. Next time. With advice like that, definitely next time.

    It's funny, but when I think about IC design, I can make leaps like that. When it comes to my cruising sled, I'm using tooth straightening technology on my frontal lobes. Ouch.

    :idea: But that's why I ask you guys stuff. Thanks.

    Paul
     
  8. alan white
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    alan white Senior Member

    Just a note: All spars mounted to swivel about a stay will bend the stay at the mounting point (usually the luff perp. level). The forestay has to be quite taut to prevent the bend being significant. The spar is pushed forward with a lot of force.
    One remedy might be a second wire from the masthead and an extended (forward) strut as part of the spar, which would act as a spreader. It would have to have a small roller on its end to roll down when the stays'l is struck, and also a keeper to prevent the strut coming off the roller. Maybe a bronze eye would be sufficient.
    Not good if there's a jib outside of the stays'l (cutter-rigged), because the strut could interfere and catch the jib.
    Proper tensioning is absolutely required in any case to keep the luff reasonably straight. Long luffs (to tall mastheads) with a big fortriangle would, I think, be a least-favorable candidate for an LP spar. On mine, I dropped the upper attachment point to a 3/4 position (and ran a yankee jib on a bowsprit to the masthead). This seemed to work out well.

    Alan
     
  9. CT 249
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    CT 249 Senior Member

    I've experimented a little bit with wishbone jibs and as Alan said, you end up with point loading on the forestay. If you rig a secondary stay, my jury-rigged attempts just loaded the secondary stay up as the wind increased, reducing forestay tension.

    The brother's 38' cat has a wishbone on the main that is brilliant, but there seem to be problems with wishbone jibs.
     
  10. verbertus
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    verbertus Junior Member

  11. Paul Scott
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    Paul Scott Senior Member

    I do recall a jib spar that was two light spars from the clew of the jib to the forestay, but that only takes one load point and turns into two, although I suppose you could cut the jib to that?

    Maybe Uffa Fox & L. Francis H. (among others) had the beginning of a solution without going far enough- replace the forestay with a spar, get rid of those pesky swept back spreaders, and running backs? and get a bit more lift off of a properly shaped jib leading edge- perhaps the problem of point loading could be suppressed, as well as headstay sag, mast compression etc.. Might be stuck with a stiff rig, though. I suppose you could have a roller reef inside of the jib spar to reef, and keep flow and shape more controlled. This idea seems to crop up once on a while- I think I saw it in Marchaj somewhere, along with a track on the bow so the jib could move to windward and to lee of the main.
    I suppose there are problems with this, has anyone actually tried it? I can see weight (which was L Francis' critique), but with carbon....? Could even incorporate the wishbone into the spar, I suppose. Might make a main wingmast easier? Could think of it as a large jib foil?

    Paul
     
  12. Doug Lord

    Doug Lord Guest

  13. verbertus
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    verbertus Junior Member

    Good design is always simple.
    I'm convinced the Gallaghan jib boom is both simpler, cheaper and superior to the Hoyt jib boom. But its merits are easily overlooked..;)
     
  14. Paul Scott
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    Paul Scott Senior Member

    Doug, having been down at the Forespar factory, the kit has been part of the plan, although a custom piece might look more in keeping with the aesthetics of the boat. I,ve seen a laminated wooden Hoyt spar that looked kind of cool, kind of like a big wooden tiller.

    There was a point in the design process when I had been obsessing over Open 60s (late 90's versions) way too much, and the question of using a big Hoyt spar as a boom for the main was tossed around, and I thought two of them would look cool. Although now that I'm thinking back on it again, making everything strong enough for the mainsail Hoyt boom seemed a bit iffy.... although didn't Gary do that on something?


    Paul
     

  15. Paul Scott
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    Paul Scott Senior Member

    Mr. Watson, nice idea- my brother tried this as a vang for the boom on his OK dinghy. It worked well, but put some stress on the mast, and the boom too, that they hadn't (in all thier hollow glory) been designed for, with predictable results. He anchored the line 1/2 way up the mast.

    I like the idea of the spinn. on the 'bowsprit'. Wasn't Jet Services using a relative of this idea? I remember seeing a drawing of an Aerosparish setup with the spinnaker launched and retrieved out of the tube formed by the boom/bowsprit. Or did I draw that? You could do that with your idea too. You might have to make it that big to handle the loads anyway.

    The only problem I can see with the idea is the speed that the jibboom would come across the deck during a jibe. :p


    Mr. Scott
     
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