pitching control

Discussion in 'Multihulls' started by pitbull, Mar 28, 2019.

  1. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    Could you convert the wave energy from the pitching motion into forward movement? If you had a computer controlled foil at the bow of the boat and a wave lifts the bow up, the foil could be angled slightly upwards so that while the buoyancy is trying to lift the bow the foil is resisting that motion and pushing the boat forward. Similar when the bow is sinking down, the foil would angle slightly downward to "glide down" into the water.

    This probably wouldn't accelerate the boat on it's own or not much, but maybe it would reduce the resistance caused by external waves. Or maybe this is already a standard mechanism for ship stabilization to smooth pitching and surge from waves.

    A deep V hull would then actually be good for this purpose because it reacts most to waves and you could put the foil on the relatively deep keel.
     
  2. Doug Lord
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    Doug Lord Flight Ready

    ===============================
    Foils are certainly subject to damage from floating junk-not just lifting hydrofoils either. But it doesn't seem to me that if they are properly designed, engineered and built that they should be subject to"overload"?
     
  3. W17 designer
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    W17 designer Senior Member

    Well, to my mind Doug .... hitting anything hard could certainly be labelled as an 'overload', no?

    We all sense how enthusiastic you are about your foil system, and perhaps for good reason, but has anyway installed your foil system on a larger boat (18'+) of late that we can see in action ?
     
  4. Doug Lord
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    Doug Lord Flight Ready

    Mike, a nearly identical version of the system is used on Gitana 17-100'+, Maserati(70' MOD 70 conversion), Macif jr(converted 24' Diam), Macif-100'+ and the former and new Banque Populaire-100'+. The main differences are that the Fire Arrow System has automatic mainfoil incidence control and a single rudder t-foil whereas the big boats require manual control input and have two rudder T-foils in the water. All the boats including mine use uptip ama foils(angled "L" on Maserati that works like an uptip) and a mainfoil capable of vertical lift and downforce along with one or two rudder T-foils in the water.
    In your post, I guess I thought you were referring to both damage from hitting an object and a different "overload". Sorry if I was wrong.
    Fire Arrow:
    MPX_Fire Arrow-3D SAILING-7-24-14 009 (4) - Copy - Copy.JPG

    Gitana 17:
    Gitana 17 very much like FA - Eloi Stichelbaut.JPG
     
    Last edited: May 15, 2019 at 5:26 PM
  5. W17 designer
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    W17 designer Senior Member

    Doug, considering the range of different foils out there now, I'd consider the lack of auto-incidence control on the big boats plus the lack of your 2 stage 'ama' flotation a not inconsequential difference, but this is hardly my field of expertise.
    But to keep this Thread on subject, how similar is your Fire Arrow system to say the Gitana17 as far as pitch control is concerned ? My guess would be that an auto-incidence system is really required for dynamic pitch control.
    I can also imagine that a large 100 footer on foils will sail flatter and can therefore benefit from sailing on two T-foils at the rear. The much smaller Fire Arrow will most likely sail with more heel, making two aft foils less practical. The larger boat will likely be proportionally heavier too.
     

  6. Doug Lord
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    Doug Lord Flight Ready

    I've talked to the designer of Gitana 17 and the designer of Banque Populaire and they both are in favor of automatic angle of incidence control of the main foil. It's presently illegal in the Ultim class but Gitana is going ahead with a system for their non-class record attempts. I'm sure that sooner or later it will be legal-just as will rudder t-foils in the IMOCA Class. On the Ultim boats it is a safety measure as well- especially when they're sailed singlehanded.
    The Two-Stage Amas are probably only suitable for relatively small tris but I haven't studied an application to larger boats. Not really related to the foil system-primarily a way to reduce drag due to intermittent ama hull contact with the water at speed and to help prevent and/or recover from a capsize.
    I wrote this a little while ago in the Fire Arrow/WOLF thread:
    Control of pitching with the Fire Arrow Foil System and the nearly identical foil systems on Maserati, Gitana 17, Macif and the former(and new) Banque Populaire:
    The Fire Arrow Foil System and the similar systems on Maserati and the Ultims use an uptip(angled "L" on Maserati that works like an uptip ) ama foil with virtually automatic altitude control , and an adjustable mainfoil on the mainhull capable of vertical lift and downforce.
    The big ocean going boats all use two rudder T-foils in the water(3 total). The rudder t-foils and the mainhull foil work together to control pitch giving substantially greater pitch control authority than a tri with just one or two rudder t-foils only (or none at all). However, on the big tris(Ultims), because of a Class Rule, the mainfoil and rudder t-foils can only be adjusted by manual control input- for the time being. Still much better than a tri without these foils.
    But the Fire Arrow (and WOLF) use an automatic surface sensor(wand) to change the effective angle of incidence of the main foil to create vertical lift and/or downforce instantly as required. The mainfoil on Fire Arrow(WOLF) working with the single rudder T-foil controls the flight altitude of the main hull, the pitch attitude of the whole boat(including the ride angle of the lee ama foil) and the angle of heel of the whole boat. The rudder t-foil is a trailing foil that automatically follows the lead of the mainfoil with no manual adjustment necessary. The rudder t-foil automatically adjusts from lifting about 20% of the boat at takeoff to providing downforce as the boat speeds up and slightly pitches down.
    ==============
    PS-Fire Arrow/WOLF are designed to fly at a 10 degree angle of heel in order to prevent the crew from having to manually raise and lower the windward uptip foil.
    On most other cats and tri's using uptip foils the windward foil is usually raised with every tack or gybe-not the case on Fire Arrow/WOLF where both ama uptip foils are left down(only one immersed at a time). The angle of incidence of the ama foils rarely if ever needs adjustment.
     
    Last edited: May 15, 2019 at 3:11 PM
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