low speed planing cat

Discussion in 'Multihulls' started by Blacky, Nov 26, 2015.

  1. Blacky
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    Blacky Junior Member

    the building plan of a 16ft catamaran is available again, an oldie from the 80s.
    According to the designer Bernd Kohler the P5000 is "...very fast and in plane even at low wind speeds"


    "The boat was very fast and in plane even at low wind speeds. Can be just seen on the photo below. I designed this boat after much research 1988. The idea used was from the research done by Mr. Ludwig Prandtl at the Aerodynamische Versuchsanstalt Göttingen" around 1958." ... "he secret is in the underwater ship. The shape towards the transom is the secret why this boat planes so easy. "

    [​IMG] [​IMG]
  2. gonzo
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    gonzo Senior Member

    Some photos or video of the boat planing would go a long way to make the claim credible. All they show is the boat surfing a little wave. One more unfounded claim by a sales department :(
  3. pogo
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    pogo ingenious dilletante

    Bernd Köhler also invented the " anti-vortex-plates" for his sharpie hulls , a sort of winglets that shall perform better than keels and daggerboards.
    His latest scoop is an A- mast with very small base and conventionel roller furling for the main--perfect aerodynamical solution.
    All his boxy boats are admired, ' cause of being simple , effective and pragmatic ---in the eyes of.....
    Al his solutions are admired by ....
    He's a sort of Piver.

    I've sailed pretty often against Köhler designs.
    Some of them have good styling, only.

  4. pogo
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    pogo ingenious dilletante

    Lot of research, Prandtl, Göttingen and secrets of underwater-shape--very funny.
    A charlatan, a succesful charlatan.

    I remember the hydraplaneur, a succesful record-holder under special circumstances.


    A planing multihull can be very fast , really , very fast . But the drawbacks under non planable circumstances, or conditions are too high.
    I know what i'm talking about. My "planing" 35 Footer from 1986 was designed for speed records,over the 500m strip , at least 35 Knots--1.2 to. She can be very fast She can.
    Even in holiday/cruising trim (2,2 to) she does 26 knots and 16 knots average over 50 nm---broad reach, beam reach.
    Performance in light winds is poor.
    On the other hand the dynamic lift, which is no planing, can help a lot.
    My boat for example ( 2.2 to) is able to sail on the ama alone , which displaces then about 800 liters --the Rest is dynamic lift !

    Planing multihulls ?
    See here:

    Best way seems to be foil assistance on a tri-- less surface in the water, planing on the aft section of the ama. Most security( bow- up attitude).
    When the lift from the foil collapes , one has the conventional static lift as reserve. Having wavepiercing hulls and the Ce back, Mast at 50 % .....
    Full foiling is in vase of a collapsing foil a desaster ---too much negative trim angle.

    Vernünftig handeln wir, wenn wir die Extreme vermeiden.
    We act clever , when we avoid the extremes.

    Claims with extreme boats ?
    Planing " Wonderboats" ?
    Again, "low speed planing cat" , hahaha !
    "Surfing" , no , following a wave on it's back with bow up attitude and claiming the boat would plane.
    Was für ein Idiot.

  5. Doug Lord
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    Doug Lord Flight Ready

    Really?! Quick: be sure to tell Team Gitana, Team Macif, all the AC teams, the Exocet 19 guys,Flying Phantom guys, the G4 guys, Nacra 20 guys, GC 32 guys and on and on......
  6. Manfred.pech
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    Manfred.pech Senior Member

    Good plans for planing hulls are very rare. Bernd Kohler has studied physics and mathematics, has worked in aeronautics industrie and has a lot of fans. He knows what he is doing. His plans are easy to follow for amateurs and are cheap.
    For my taste I would like him to redesign the top of the sail of TENSON and we should know more about his "secret".

  7. Banzai
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    Banzai Junior Member


    I don't think Bernd was making any outrageous claims here. The design is an old one for which , for reasons dating back to the pre-electronic age he no longer had the hard copy of the plans. A former client recently sent him a copy of the original plans , so he recently made them available again, very cheap. "Fast and early planing" by the standards of the day makes no special claim IMO- after all , what from the eighties would have been a comparison -Hobie 16 etc??
    I recently built one of Bernd's designs and I have to say the man is a delight to deal with.

  8. CT249
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    CT249 Senior Member

    By 1988, a "very fast" 16 foot cat should have been a lot faster than a Hobie 16. The Taipan 4.9 in its original form in 1982 was faster than an A Class in very light winds, very competitive with Tornadoes, and was over 10% quicker than a H16.

    If the "planing cat" was really all that fast it should have won lots of races. Did it?

    If someone is going to make an exaggerated claim about how good their boat is, why can't other people make claims about it too?
  9. Doug Lord
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    Doug Lord Flight Ready

    Two wrongs don't make a right. There is definitely a better way of handling it than doing the exact same thing!
    And ,lacking any further information, maybe the guy is right.
  10. Richard Woods
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    Richard Woods Woods Designs

    All boats are fast by themselves. The only way to prove a boat is actually "fast" is to race it. And in Holland in the 1980-90's that would mean the Texel race.

    So it would be interesting to see the Texel race results, and of course its TR

    Richard Woods

  11. pogo
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    pogo ingenious dilletante


    you know the planing boat above is not a Köhler design---it's the Vario 18 designed and built in 1986 by Schulz. (The pic has been made by u.)
    A Cat with variable geometry---pushing the leehull forward . Hulls are half Vees with outer stringers/sprayrails ----splitted V-hulled motorboat.
    An experimental very special and very fast boat, but, for broad reaches only.
    I remember the boat being exhibited at the Hanseboat in 1986. It was there for demonstrating Schulz's knowledge about honeycomb-sandwich, with which he produced his Baltec Catamarans Series 30-50' ( also available as kits ; precutted flat honeycomb panels --predecessor of Duflex Kits.)

    "Damit Du ein gleitendes Multi zu sehen bekommst, zeige ich zum wiederholten Male ein Foto, das ich 1987 beim Multi-Treffen in Kiel aufgenommen habe. Es handelt sich dabei um den Vario 18 von Stefan Schulz, einen Kat, dessen Rümpfe gegeneinander verschoben werden können (Parallelogramm)."
    Source : Manfred Pech; Post # 136 ; http://forum.yacht.de/showthread.ph...digkeitspotenzials-von-Mehrrumpfbooten/page14

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