Patient Lady Wing Control System

Discussion in 'Multihulls' started by Doug Lord, Sep 13, 2010.

  1. Doug Lord
    Joined: May 2009
    Posts: 16,653
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Thanks to Steve Clark for converting this to a PDF!

    Steve:
    The wing self tacks just as an over rotating mast tacks.
    The camber control is all lead and cheated on the wing, not on the trampoline.
    SHC

    Beatings will continue until morale improves.
    =================
    More on this from Steve on SA:

    The flaps are torsion-ally wimpy. They have to be able to twist about 10 degrees from top to bottom. If they are a spar and frame structure this is easier than making them rigid. If they are composite skin structures, like on my new wing, it is still pretty easy for them to twist this much because thin airfoils aren't really very good torque tubes.

    The deltas and control arms are linked by control cables.
    The port side of each delta is connected to the starboard side of its matching control arm.
    Thus as the flap swings back and forth the flap angle at the boom is transmitted to the control arms.
    The cam paths within the deltas allow us to alter the relationship between the boom flap angle and the flap angles at the respective control arms.
    The flap angle itself is controlled by a purchase between the a frame that is attached rigidly to the #1 element and flap at boom height. If this purchase is tight, there is no flap angle. As it is eased, the flap angle can increase.
    Because the wing is supported by the mast step and a sheet point on the flap, aerodynamic load forces flap angle increase. Therefore we limit the growth of flap angle by limiting the distance between flap and the aft end of the a frame.

    us772- your confusion is probably because dirt boats don't have sheets as soft water boats have. So you have a fundamentally different way of doing things. You control AoA of the wing with gears and push the flap to windward to induce flap angle. We do not need to restrain our wings as much as you do because our apparent wind speeds are so much lower.

    SHC
    ==============================
    Magnus Clarke from SA:

    I'll chime in, without having looked in detail at the PL files.

    for your own sake seperate two things in your heads now.

    One, Camber angle.

    Two, twist (Delta system)

    Camber angle we use to describe the angle between the main element and the flap, at the foot of the wing. Get it? The alpha wing has an arm, the CAMBER ARM, that projects off the back of the main element below the flap. There is a line from the flap down to the camber arm. If the Camber arm is right under the flap, you have zero degrees of camber. If you let that camber line out, it allows the main element and the flap to fold up relative to each other, this is CAMBER. So picture you are sailing along on Starboard tack, and the flap is folding away from you as wind pressure is making it fold about the hinge line in the wing. The camber arm will be sticking out to leeward of the flap. The camber line is stopping it from folding or cambering any further.

    Now tack. All the wing does is fold inside out. guess what, the camber line is still the same length on the other side of the boat, so therefore the camber angle is the same from tack to tack. Thus it is self tacking.

    Questions about camber?

    Two, twist-delta. The job of the delta system is to translate motion / angle from the bottom of the wing to other places higher up on the wing. Alpha, Cogito etc all have the same kind of system, thanks to SHC, Duncan, Dave Hubbard etc. The delta horn is mounted to the lower hinge pin (Which is NOT in line with the slot loaction, it's forward of there). To start, consider the delta horn being set to a center position relative to the FLAP. When sailing on starboard again, the leeward delta line will be under tension, the weather one will be slackish, if the system is centered, you preload these lines as much as possible to accurately transmit camber angle up the wing, if it's loose, it sucks. So the leeward delta line is tight upwind at the foot of the wing. Now follow this line forward to somewhere near the LE of the main element. it turns and goes up the wing, it crosses over to the windward side of the wing and exits the wing, say at the hounds. It comes aft and attaches to the horn of the FLAP. Keep in mind this line is under tension, so it is stopping the FLAP from blowing open to leeward. the FLAP is hinged and without support it would simply blow off to leeward right? The delta line stops this.

    Any questions so far?

    So here we are sailing on Starboard, the wing is folded and pushing to the port side of the boat, at the foot of the wing the leeward delta line is under tension and it carries up and crosses over and out of the wing at the hounds. Here is supports the top part of the flap from blowing open to leeward. So what the delta is doing is transmitting the CAMBER ANGLE from the foot of the wing to some place higher up the wing. I have 20 degrees of camber at the bottom, now I have 20 degrees of camber somewhere higher up the wing too. Make sense so far?

    So now if I were to go back to the delta horn at the bottom, and allow it to rotate relative to the FLAP, and by allow, I mean ease off because it's held there with a piece of string. It would allow the delta line to effectively get a little longer. So If I allow the Delta horn to rotate 5 degrees while I have 20 degrees of Camber, what would by camber angle be at the hounds? thats right 15 dergees, the 20 degrees of camber at the bottom minus the 5 degrees of TWIST I just allowed into the Delta system. thus I have allowed my flap to twist between the foot and the hounds.

    Now think about the delta horns at the bottom of the wing. I ALLOW it to rotate between zero and 15 degrees lets say by allowing it to move away from center line with a piece of string. That means it too is self tacking. Because the ease on one tack is the same as the other.

    Also, you can set up your delta to control more than just one point aloft on the wing. We just used the hounds because its a sensible place to do it for a number of reasons.

    What this system cannot do is pull your flap, aloft, to have more camber than your foot, unless you set up seperate Port / Starboard delta controls, and you manually tack it, to pull it to windward like a traveller in light air. that having been said, there is not a lot of reasons to do this until you know a bunch more about wings.

    ===============
    More from Steve on SA:

    The green bit is the boom and is "rigidly" attached to the bottom of the flap.
    The quotes are because there is some rocking and rolling necessary to accommodate the flap twisting, but forget that for now.
    The mainsheet is attached to the boom.
    The flap angle or camber is adjusted by controlling the distance between the boom and the camber A frame ( which is Cyan in this rendering) This is done with string and blocks. Because the aerodynamic center is between the mast step and the main sheet, if you ease this purchase the camber will increase. If you tighten it is will decrease. If the flaps were stiff enough, or your wing small enough, you would need nothing else. This purchase system is double ended, so there are port and starboard cleats. you can adjust it from either side, but it is self tacking.

    The delta control is a cam, or orange cylinder, is pulled aft by a block and tackle and bungeed forward. Like the camber control, it is lead to both sides of the wing, but does not have to be adjusted with each tack or gybe.

    The main structural element of these wings is a "D" section mast. This is the leading edge of the main wing. It takes all the torsion and compression loads of the rig.

    The control cables run from the ends of the deltas, forward to the D section, up inside the wing, crossing to the other side on the way,at the correct height they exit the wing and go back to the control arm (or horn) Thus the port end of the delta is connected to he starboard end of its corresponding control arm (or horn.) There are four such cables for this wing. They can be adjusted to assure that the flap is straight, but once they are set, they are fixed length and aren't adjusted while sailing.

    Hope that helps.
    SHC





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    Attached Files:

    Last edited: Sep 16, 2010
  2. bearflag
    Joined: May 2010
    Posts: 227
    Likes: 17, Points: 0, Legacy Rep: 195
    Location: Thousand Oaks, California

    bearflag Inventor/Fabricator

    I will ruminate on this... v. interesting.
     
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