Tantra-Prototype Daysailer 1977

Discussion in 'Sailboats' started by Doug Lord, Oct 30, 2009.

  1. Doug Lord
    Joined: May 2009
    Posts: 16,597
    Likes: 300, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    I designed and built this boat between 1974 and and 1979 as a one-off of glass. She had a circular cockpit with molded in leeboards.The leeboards were asymetrical and toed in a couple of degrees(2.5) Just ahead of the cockpit was a huge dry stowage compartment and just aft a cooler with flush hatches. The cockpit had two self-bailers.
    The boat sailed very well hanging with US 1's when using a US 1 rig even though she was 80 lb heavier. She went to windward very well.
    The experimental square topped main (1977)was the very first square top made by Johnson Sails when Clint was still the man. It was too much SA for the boat.
    She might have made a good production boat(and still might) with some refinement.
     

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  2. Doug Lord
    Joined: May 2009
    Posts: 16,597
    Likes: 300, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Tantra II-Twin Foil

    The Tantra was an exciting project and at the time it was limited to proving that asymetrical molded in leeboards would work. It was hoped that with those, the circular cockpit, molded in cooler and huge molded in dry stowage compartment that the boat could be put into production as an advanced, shallow draft daysailer. That didn't get done but the boat has stayed with me all this time and the concept has morphed over time as I've learned more.
    The Tantra II-Twin Foil is a design concept where the molded in leeboards have become trunks to contain twin curved lifting foils that will allow substantially increased righting moment and hence greater performance.
    Curved lifting foils have been pioneered by multihulls and are now used in many of the fastest multihull classes including the A Class, Nacra 20, Nacra Olympic 17 and many more. This type of foil- that generates vertical lift as well as lateral resistance- has also been pioneered in the Open 60 monohull raceboats, notably on Saffron and Virbac-Paprec III.
    Well, it dawned on me a while back that the Tantra configuration is IDEAL to incorporate curved lifting foils in a monohull dinghy, probably a bit bigger than the original boat perhaps in singlehanded, singlehanded trapeze, and double handed trapeze versions. For the singlehanded version the lifting foils dramatically increase righting moment probably allowing a doubling of SA from the original.
    On trimarans that use the curved lifting foil in the ama the foil lifts in the vicinity of 70-80% of the boats weight-the rest is supported by ama buoyancy and is used for pitch control. Since the Tantra II-Twin Foil has no ama the boat will probably require a small T-foil rudder for pitch control.
    The T2-TF ,if it is ever built by me, will be very similar to the original and here are a couple of rough sketches of the concept and the foils:

    click-
     

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