buccaneer 40 mods

Discussion in 'Multihulls' started by sailorman282, Jan 18, 2016.

  1. Gary Baigent
    Joined: Jul 2005
    Posts: 3,019
    Likes: 136, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    Go for it Doug, build a full size version, say 8 metre size - and then sail it in 45 knots wind and big seas.
     
  2. pogo
    Joined: Mar 2010
    Posts: 342
    Likes: 9, Points: 18, Legacy Rep: 73
    Location: Germany Northsea

    pogo ingenious dilletante

    "Touché",
    oder auch
    "Treffer, versenkt".
     
  3. pogo
    Joined: Mar 2010
    Posts: 342
    Likes: 9, Points: 18, Legacy Rep: 73
    Location: Germany Northsea

    pogo ingenious dilletante

    Perhaps the most practical solution for a foil- assisted cruiser/racer trimaran has been developed about 20 years ago by Aldis Eglåjs for his Catris.
    His boats feature a symmetric foil at the float's stern--a stabilizer controlling the floats attitude.
    There is an inverted t-rudder which also has a symmetric horizontal foil/stabilizer.
    Negative longitudal trim of the whole boat means negative angle of attack at the symmetric stabilizers thus negative lift for correcting this "bad attitude " , and, vice versa.
    The whole setup one could compare with that one of modern airliners - aircraft configuration.
    The advantage of Aldis' system is that it uses no wands, automatic or manual articulating foils,
    or similiar complex, vulnerable and not reliable gimmicks.
    The Catris have retrectable mainfoils for harsh conditions ----when they would become dangerous. the floats have sufficient buoncy.
    On the latest version the floats' stabilizers are also retractable , either for getting rid of their wetted surface under lightwind conditions and for negative attitude under thesese condition, or for a seastate when the stabilizer/mainfoil system can' t cope the wavepattern. The Catri is a conventional tri then.

    Unfortunately i have found no pix of this principle, they have gone with the russian, brazilan and latvian yards that have tried to produce Catri 26R , Catri 27, Catri 24.....
    There is a new attempt under new management,
    i found found this :

    http://i0.wp.com/catri.catrigroup.c...5/03/Foiling_mode_of_the_new_Catri_series.png
    http://i0.wp.com/catri.catrigroup.com/wp-content/uploads/2015/03/Catri23_No3_Sweden.png

    Here' s the site with an interesting , short multihull-vita of Aldis :
    http://catri.catrigroup.com/designer/

    And the Bucc 40 ?
    i would opt for retractable asymmetric mainfoils not too far forward and retractable symmetric stabilizers. Being retractable means that they ....see above ; Catri.
    I think the stabilizer is also necessary, because the Buccs floats have a too little area in the aft sections for dynamic lift/planing, which might result in too much positive attitude generated by the mainfoil.




    pogo

    pogo
     
  4. warwick
    Joined: Jan 2012
    Posts: 423
    Likes: 7, Points: 18, Legacy Rep: 63
    Location: papakura south auckland new zealand

    warwick Senior Member

    Catri 24

    [​IMG]
     
  5. Gary Baigent
    Joined: Jul 2005
    Posts: 3,019
    Likes: 136, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    Excellent boat, ahead of its time when it first arrived - and still is in terms of production family trimarans.
     
  6. oldsailor7
    Joined: May 2008
    Posts: 2,097
    Likes: 44, Points: 48, Legacy Rep: 436
    Location: Sydney Australia

    oldsailor7 Senior Member

    Can you imagine having to go outboard to handle that retractable board in really bad seas , or even at night in any weather. :rolleyes:
     
  7. Gary Baigent
    Joined: Jul 2005
    Posts: 3,019
    Likes: 136, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    Why bother; foil down in nasty conditions (okay, half board down) is exactly what you require: greater stability and better platform motion through seas.
     
  8. OzFred
    Joined: Nov 2015
    Posts: 510
    Likes: 57, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    This seems to be a pervasive misconception and if true, foilers wouldn't need weird foil shapes or fancy control mechanisms. But they do, so it isn't.

    The lift of a foil is based on its angle of incidence to the flow (all else being equal). If a foiling boat is in equilibrium with a velocity in a particular direction (let's say parallel to a mean water surface), then pushing down the bow also angles the vector downward, the foils continue to see exactly the same angle of incidence with the flow so the boat simply drives into the water.

    A control mechanism is required that creates more lift and overcomes the downward vector component. Many such mechanisms exist (wand control of a flap or angle of incidence of the foil and increased immersion of surface piercing foils being two).

    Rudder foils work on planing skiffs because when the bow goes down, the velocity of the boat continues more or less in the same direction (roughly parallel to the surface) as it's constrained by the surface of the water, so the angle of incidence of the rudder is changed, creating down–force (or maybe just less lift).

    As the bow starts to bury, the boat slows so the effectiveness of any foil is reduced, hence the need for "wave piercing" bows to keep the speed and hence foil effectiveness up.
     
  9. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 349, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    That isn't correct: the angle of attack of a rudder hydrofoil set at zero degrees angle of incidence will change if the bow is momentarily depressed by a gust causing the rudder foil to develop less lift or create downforce. That's how a trailing rudder foil works and why it can help maintain pitch stability on boats with surface piercing foils that have no active control over the mainfoil angle of incidence and whose altitude varies with speed.
    NOTE:
    --"Angle of Attack"(right illustration below) is the angle of the foil relative to the oncoming flow.
    --"Angle of Incidence" (left illustration below) is the angle of the foil relative to the boat it is on relative to something like the flight waterline and/ or the static water line.
     

    Attached Files:

  10. pogo
    Joined: Mar 2010
    Posts: 342
    Likes: 9, Points: 18, Legacy Rep: 73
    Location: Germany Northsea

    pogo ingenious dilletante

    Catri
    Longitudal Stability by amount of Lift from mainfoil ( Complete down to Partly retracted) and pre-adjustable angle of attack For stabilizer


    http://catrigroup.com/wp-content/th...08/Catri-25-foiling-mode1.jpg&w=432&h=150&a=c

    "After the first trial of new Catri 25 we have received several questions. Some will be able to answer after the next trial, other can immediately. Here first talk about Catri hydrofoil system stability as the main answer to questions have already been rounded off 30 years ago and also later stability and security are most studied. Hydrofoil to be effective, especially on a wavy sea, the surface sensor is needed on front of it which changes the angle of foil. As a sensor on a Catri hydrofoil system serves entire leeward float along with the front foil. To provide the highest possible system stability the front foil shifted far forward, but total weight of trimaran to the rear. The front foil lift capacity can be adjusted in two ways – by raising or lowering and now on the new Catri 25 also changing float aft foil depth and angle. This can be done at three levels and three angles, that is, in nine different positions. Therefore at relevant wind hydrofoil lift almost similar to common weight of trimaran and water covers only the bottom hole of case.
    http://i0.wp.com/catri.catrigroup.com/wp-content/uploads/2014/08/M120018.jpg
    Starting the tests, we were afraid that vertical surface of unchanging foils will interfere steering. The tests showed that the difference of surface areas is large enough to be felt not fault at all. Therefore, the production construction will be left unchanged. Every owner will have the opportunity to experiment and choose the most appropriate foil position for his payload with the minimum float draft and maximum longitudinal stability."

    Source with some Pix
    http://catri.catrigroup.com/catri-foiling-mode/



    pogo
     
  11. OzFred
    Joined: Nov 2015
    Posts: 510
    Likes: 57, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    Your statement is inconsistent with your definition. Starting from equilibrium, if the bow of the boat is depressed 1° then the entire boat travels in a vector depressed 1° from previous and the angle of incidence and angle of attack of the foils remains exactly the same. Nothing changed their angle with the boat, and since it's the boat's velocity that creates the flow, it also sets the the angle of attack, they must remain in a constant relationship.

    If the speed remains the same and the angle of incidence remains the same, the angle of attack can't change, regardless of where the boat points (i.e. the actual velocity vector).

    Without some adjustment, the foils have not changed relative to the hull nor to the oncoming flow.

    Think of the sail planes on a submarine with neutral buoyancy. Starting from a vector say parallel to some equipotential surface, if they are used to pitch the nose up say 5° then returned to the original angle of incidence, the submarine just continues in a new straight vector in the new nose–up attitude (relative to the previous vector).

    There is no magic from the stern planes to push the nose back down parallel to the previous vector or return to the previous depth. There may be a tiny amount of resistance from the stern planes while the submarine is turning, but that just resists the turn, it doesn't return the boat to its original vector.

    You're back on ignore.
     

  12. waynemarlow
    Joined: Nov 2006
    Posts: 435
    Likes: 50, Points: 28, Legacy Rep: 134
    Location: UK

    waynemarlow Senior Member

    If only the vectors on a yacht were as simple as if you change the angle of attack the boat will immediately rotate toward the new desired vector, re establish the neutral point and the boat will continue on that vector.

    Yes on aircraft there is an almost case for this and I can remember doing graceful loops in gliders where with just speed and very small elevator deflection you can pull small positive G throughout the loop. The amazing thing was the efficiency of a modern glider was that you would only lose about 30 metres of altitude in the process. Quite an eye opener or should I say back of the neck hair raiser, for the passenger in the front when on completing 2 loops you completely traded speed for height and when the wings no longer could hold the glider, intentionally spun the glider rotating vertically at the ground only to pull out and end back up within a couple hundred metres below where you started from. I digress but to put just how much less friction and drag there is in air I have been told but not able to confirm, the very large wing span gliders now have a L/D not unsimilar to the earths curvature in a perfect non sinking air masses.

    But we are talking about yachts and we have lots of other forces operating, such as leeway on the foils, vertical lift from the sails, large amounts of mass forcing the yacht to maintain its foward vector despite the bow starting to drop, it's way way more complicated than simply what the angle of attack is of the front and rear foil.
     
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.