Dinghy Design: Open 60 influence?

Discussion in 'Sailboats' started by Doug Lord, Jan 22, 2011.

  1. Gary Baigent
    Joined: Jul 2005
    Posts: 2,959
    Likes: 102, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    Okay, you've got a track on the boom ... but why the complication? You could have a straight track on deck (why bother with a reverse curve?) plus boom track and do the same job, but simpler, less material etc. Still think you could mount a aft curbed track which becomes mainsheet/traveller/vang all in one.
    Nothing wrong with the foils idea .. but if you're carrying foils, you need larger sail area to make proper use of them - otherwise, what's wrong with keeping it a conventional dinghy, simpler, less material etc.
     
  2. Doug Lord
    Joined: May 2009
    Posts: 16,602
    Likes: 302, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    =============

    150sq.ft. on a singlehanded monohull seems appropriate-and fast. The way these foils are deployed they not only lift the boat but they add RM. The original was fun to sail- I bet this would be a blast. One of the things about these foils I like best is that they are shallow draft and still have a high aspect ratio-neat!
    The reverse curve allows the sheet to move aft on the boom in stronger wind and also makes room for the dry stowage compartment in addition to fitting an already proven structural plan.
     
  3. Cheesy
    Joined: Aug 2008
    Posts: 315
    Likes: 12, Points: 0, Legacy Rep: 189
    Location: NZ

    Cheesy Senior Member

    Would it not be much simpler to use a gnav vang and get rid of the traveller all together? You already have half of it on the boom by the sound of it. A simple bridle on the back with the sheet lead forward and either off the boom or down and off the cockpit floor/behind the mast step would be really simple and work well.
     
  4. Doug Lord
    Joined: May 2009
    Posts: 16,602
    Likes: 302, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    =================
    I don't like having a bridle aft where it can interefere with the tiller or tiller extentions-this reverse traveller works real well particularly with a square top rig. Its also pretty simple- eliminating the need for a vang and keeping the sheets and contol lines forward. I like it and it has been proven to work well-why change?
     
  5. MalSmith
    Joined: May 2004
    Posts: 111
    Likes: 9, Points: 18, Legacy Rep: 116
    Location: Australia

    MalSmith Boat designing looney

    Doug,

    That's a much better arrangement than the reverse curve foils you had previously. You could be on to something. I envisage that you could deploy the leeward foil upwind for added stability as you say. Downwind you could deploy both foils and they would act as surface piercing lifting foils, as per Hydroptere etc.
     
  6. Doug Lord
    Joined: May 2009
    Posts: 16,602
    Likes: 302, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Dinghy Design: Open 60 influence? / Tantra II

    ===========
    Thanks ,Mal. I hadn't considered your downwind scenario-something to think about. I would be concerned about what happens at faster speeds since the foil gets flatter when fully extended-perhaps retracting them a bit would work best.

    Tantra II
    LOA-15.5'
    Beam- 8.75'(pods fold to trailerable width)
    Sail Area-150sq.ft.+ asy-spin
    Draft-1.17'( 14" )
    Weight- 175lb
    Sliding Bench Seats
    Retractable, Curved Lifting Foils
    Retractable Rudder Gantry
    Wing Tip Rig RJ(ribbon jib)
    Reverse Curve Traveler



    Pictures showing old version of Tantra(with molded-in leeboards, reverse curve traveller, molded-in dry stowage compartment, molded-in cooler, circular cockpit) and Tantra II with curved lifting foils(click on images), wing tip rig(with ribbon jib) and the other features of the original boat:
     

    Attached Files:

    Last edited: Feb 6, 2011
  7. MalSmith
    Joined: May 2004
    Posts: 111
    Likes: 9, Points: 18, Legacy Rep: 116
    Location: Australia

    MalSmith Boat designing looney

    Yes, that's how I imagined you would do it. It could be quite a flexible system. The foils could be both fully deployed in marginal conditions for maximum lift, then partially retracted as the wind speed increased. I'm still thinking foil assistance rather than fully foiling, but a low level fully foil supported mode should be possible in the right conditions.
     
  8. Doug Lord
    Joined: May 2009
    Posts: 16,602
    Likes: 302, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Dinghy Design: Open 60 influence? / Tantra II

    Mal, thanks for your thoughts. The more I look into this and how a boat like the "Tantra II" would use these foils the more I like it. A small boat like this would definitely require the rudder t-foil with the foils lifting a large(80%) percentage of the boats weight. I like the shallow draft which is a big attraction. I think the possibilility of using "foil assist" on a "performance daysailer" has great potential for offering new types of exciting boats that aren't limited by the athleticism of super high performance current designs or the relative lack of performance of most daysailers.
    The downside is that the area of the hull is fairly large which will make keeping it light a bit more of a problem.
     
  9. Doug Lord
    Joined: May 2009
    Posts: 16,602
    Likes: 302, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Dinghy Design: Open 60 influence? / Tantra II

    I've thought more about the curved foils and rudder foil:
    1) seems like the angle of incidence of the lifting portion should be adjustable,
    2) probable use of an asymetrical section like the 63412,
    3) probable toe-in of the foils-fixed at around 3 degrees.
    4) adjustable angle of incidence of rudder foil-question whether to use twist grip facility like a Moth-leaning against that.
     

    Attached Files:

  10. Gary Baigent
    Joined: Jul 2005
    Posts: 2,959
    Likes: 102, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    A little voice in your ear, Doug - why not make the hull finer, like half the beam you have at the moment ... and maybe spread the overall foil beam a little ... now what do we have?
     
  11. Doug Lord
    Joined: May 2009
    Posts: 16,602
    Likes: 302, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ====
    What-no amas?! The original worked good with a narrow main hull and molded in leeboards. Of course, there was no hassle with raising and lowering them.
    Assuming that's not a great problem a boat like this ought to be fun. Even w/o amas.... And fast...

    -----------------------
    Now that I thought about it some more(nice spark, Gary!):
    To make a decent trimaran using these"tight curve" shallow draft foils ,it seems to me that the boat would have to be something like a WETA-maybe with smaller amas-just enough to support 20% of the weight. That would allow more sail area and give the resulting small tri the ability to fly the main hull which is a good thing and not available on almost any small tri's currently. But there are problems: a small tri with a huge RM doesn't want to fly early so something like this might be a better solution-especially if the planing amas don't work too well because the shallow draft curved foils with a small ama would be an excellent solution. Shown is a 12 footer where it is almost impossible to get the main hull narrow enough for the required weight-making a planing main hull+foils the best choice. The foils allow the main hull to fly early:
    http://www.boatdesign.net/forums/multihulls/mpx-11-very-small-high-power-trimaran-33686.html
     

    Attached Files:

  12. Doug Lord
    Joined: May 2009
    Posts: 16,602
    Likes: 302, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Dinghy Design: Open 60 influence?-Max Performance

    The sketches I showed earlier illustrated curved lifting foils on a "performance daysailer". The more I've thought about it I think this technology can be adapted to high performance design-specifically to exploit the advantages these foils can have in helping to generate speed with exceptional allround performance for a monohull dinghy.
    Anybody have any thoughts on a design like that?

    curved lifting foil on the Open 60 V3:

    (click on image)
     

    Attached Files:

  13. Gary Baigent
    Joined: Jul 2005
    Posts: 2,959
    Likes: 102, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    It's just another boat, Doug, just another dinghy and instead of trapezes, uses foils for power and stability. Whether on a dinghy you can beat the performance of a similar sized multihull foiler ... remains to be ... actually no, it will be slower. I think you're just fiddling around trying to be close to a Weta ... and Weta is now being super tuned with outsider full wings, probably foils too. Going to be hard to beat. So why bother? Weta is a superb design. Kiwi too, you know.
     
  14. CutOnce

    CutOnce Previous Member

    Gary:

    Why do you persist in telling the punchline well before the troubled genius telling the saga is finished? It takes all the fun and suspense out of the story, and puts our favorite storyteller into defensive mode.

    Given sufficient time, this valiant quest for low effort high performance will end with the evolving Weta, but why deprive us all of the fun napkin engineering, wild integration of mismatched technologies and Rube Goldberg-esque design?

    Boatdesign.net's favorite son gives us the opportunity to enjoy living within an ongoing and long running Monty Python skit. Enjoy it for what it is.

    --
    CutOnce
     

  15. Magnus44

    Magnus44 Previous Member

    I have to know. Is there proof in these objections and in the presentations of Doug? I wish to make a boat of the type being discussed for dinghy and small boat fast sailing in the waters of Scandinavia and this looks good if it can work. I live in Sweden and Montana as both are of the same climate, but sail in Sweden with old friends

    I look for the responses of men with design knowledge.

    Mag
     
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.