Jessica Rabbit-40' Foil Equipped Trimaran

Discussion in 'Multihulls' started by Doug Lord, Mar 10, 2013.

  1. Doug Lord
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    Doug Lord Flight Ready

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  2. Doug Lord
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    Doug Lord Flight Ready

    Jr 40

    I found this on MA from the designer:

    Posted 05 March 2013 - 10:41 PM

    Hi,

    I am Martin Fischer. I designed Jessica Rabbit together with Benoit Cabaret and John Levell. First of all I want to correct something. Further up in this discussion someone wrote that we had reported 40 knots of boat speed. That is not correct, so far our top speed has been 33.1 knots in about 19 knots of wind, two sail reaching on flat water. We have rather regular trade winds here in Noumea and while broad reaching we achieve regularily 30+ knots of boat speed.

    We are still "discovering" the boat, but we are getting better at sailing her. Jessica Rabbit has - for the size of the boat - relatively large foils and she has T-rudders. This combination of big foils with T-rudders stabilises the boat very nicely. So far we never have had any critical nose dive situation or any kind of pitch instability.

    We sailed the boat once with normal rudders in about the same conditions as on the video. The difference was quite dramatic. Broad reaching the boat was much less stable. Average speed was about 2 knots lower and top speed more than 3 knots lower.

    Upwind the boat is pretty amazing for a 40-footer. Up to about 16 knots of wind we are doing 14 to 15 knots of boat speed, which is what we expected. But in 18 to 20 knots of wind the boat suddenly steps on her foils while sailing upwind and boat speed increases instantaneously from about 14.5 kts to 17.5 kts. This was achieved with a true wind angle of about 44 to 45 degres.

    Most of the tooling of Jessica Rabbit is still available - so contact me (martin.ncl@gmail.com) or Philippe if you are interested.

    cheers

    Martin
    ================
    Hi,
    mast height above water line is 20 meters, maximum sail area upwind is about 130 m2, engine is about 30 hp. The maximum sailing weight including crew and equipement is 3.7 t. The interior is pretty simple, but nevertheless there is enough space for 6 people to sleep, there is a nav station and a simple kitchen. So the interior is much more comfortable and spacious than on an ORMA-60.

    cheers
    Martin

    =================
    More interesting comments by Martin Fischer in this thread: http://forums.sailinganarchy.com/index.php?showtopic=144893#entry4073189
     

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  3. SteveMellet
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    SteveMellet Senior Member

    If I win the Lotto, I know where my money's going..:D
     
  4. Doug Lord
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    Doug Lord Flight Ready

    Jr40

    Here is an excerpt of an interview with Martin Fischer in catsailingnews.com :

    What about Jessica Rabbit, that wild Tri you once sent me images of her launch, you reached 40knots? It flies too ?! Why you used T rudders on that Tri instead of L ?

    MF: We haven't reached 40 knots - that probably would be a bit much for a 40ft trimaran - but 2 weeks ago we hit 33.1 knots in 20 knots of true wind speed. The boat does not fully fly, but it is very close to flying. I reckon that the foil and the T-rudder carry between 80% and 90% of the total weight when she is on her foils. At high speed the boat is very stable and she never feels dangerous.
    Upwind in stronger winds (20 knots) the boat is surprisingly fast for her size. In fact the foils are very big for the size of the boat and in these conditions the boat steps literally onto the foils when sailing upwind. The effect is an immediate jump in boat speed and pointing angle.
    We went for t-rudders mainly for structural reasons. For a bigger boat the loads can become pretty high and with a T-rudder the maximum bending moment is reduced by a factor of 2 compared to an L-rudder.
     
  5. tomas
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    tomas Senior Member

    Weight?

    Doug, what is the dry weight of this tri, ready to sail?
     
  6. Doug Lord
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    Doug Lord Flight Ready

    Jr 40

    --------------------
    Maximum sailing weight(incl. crew and equipment) in Post #1: 3.7tons- I assume long tons, so 8140lb- other than that I don't know.
     
  7. tomas
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    tomas Senior Member

    Oh, missed that. That's helpful, thanks.


    I found a recent interview that references his website but couldn't find the actual site address, do you know it?
     
  8. Doug Lord
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    Doug Lord Flight Ready

    ========
    I didn't know he had a website! Search "catsailingnews.com" or send a PM to K2Mav who IS catsailingnews and ask him. Let me know if you find out or just post it here. K2 has posted in the "Dario Valenza.." thread so just go and click on his name and go from there....
     
  9. Doug Lord
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    Doug Lord Flight Ready

    JR 40--foil adjustment

    From Martin Fischer on SA:

    For the AOA of the foils we have a hydraulic system to change the rake of the foils. If you change the rake of the foil you implicitly change also the load distribution along the curved foil and thus the effective dihedral angle. Hence if you increase rake this has the same effect as if you increased the dihedral (more horizontal).cheers
    Martin
     
  10. Doug Lord
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    Doug Lord Flight Ready

    Among his other projects, Martin Fischer designer and owner of Jessica Rabbit has designed Championship F18's and is working on foil systems that have a lot less wetted surface and complication than "traditional"(pre-Martin) fully submerged or surface piercing foils. Paradox is another Fischer designed A Class using the new foil system and Martin is working with a team on the Flying Phantom F18 foiler.
    So here is a bit about the man:

    Martin Fischer, Naval Architect

    Born in 1962
    Doctor in fluid mechanics
    Designed the Capricorn in 2001
    Member of the Groupama design team 60" Orma trimaran Groupama 2 in 2004
    The Capricorn was crowned F18 World Champion in 2006
    Member of the Groupama design team Maxi trimaran Groupama 3 in 2004
    Member of the Oracle design team maxi trimaran in 2008
    Designed the Wild Cat in 2008
    The Wild Cat with SAIL INNOVATION sails is crowned F18 World Champion in 2010
    Groupama 3 won the trophé Jules Vernes in 2010
    Designed the Phantom in 2011
    The Phantom was crowned F18 European Champion in December 2011

    Sail Innovation: http://www.sail-innovation.com/
     
  11. Skyak
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    Skyak Senior Member

    The daggerboard AOA is adjusted, but not controled? How about the T-Foils? Are there any attack controls?
     
  12. Doug Lord
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    Doug Lord Flight Ready

    -------------
    See Post # ( above)
    -------
    I guess you mean angle of incidence which is what you change when you adjust a board relative to a boat. I would imagine there are adjustments on the deck to,at least, change the angle of incidence of the curved boards to change how much vertical lift they develop. With a curved board you can adjust the angle of the vertical lift portion of a foil independently of the lateral resistance portion. I'm 99% sure that every foil that develops lift on this boat is adjustable for tuning purposes if for no other reason.

    Picture- this is a sliding plate on an A Class deck that allows vertical lift adjustment by sliding the plate fore and aft:
     

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  13. Corley
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    Corley epoxy coated

  14. Doug Lord
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    Doug Lord Flight Ready

    Cool-maybe that means Martin will do a full flying bigger boat?
     

  15. Corley
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    Corley epoxy coated

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