buckdouger

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About buckdouger

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  1. buckdouger

    Luna Rossa Challenge. AC 36

    Thanks and agreed, the reason for asking for a definition is because that is the challenge for the teams - to engineer things quantitatively. We don't have the same data, but thinking that way can reveal new things. I am not sure I see any issue with maximum camber at the foot, disturbed or not. Certainly the more power down low, the less the heeling moment, so you would think of maximizing this. Maybe there is somethings going on with Ineos along those lines, although the high sides could equally interfere. One reason for not putting max camber might be inability of the flow to stay attached, but I think with the exception of really large macro turbulence which would be transient and sporadic, the disturbed air would not hurt. The boundary layer will already be tripped and turbulent. Putting the boom under the sail itself means you don't need a bending or articulating boom - simpler to engineer, maybe more reliable. I'm not sure ETNZ has more camber control - I'd be looking at how many points of contact there are between their bending boom and the sails. It may just be at the clew, and the complicated mechanism is designed to bend just to stay clear of the sails. This seems very sensible - are the ovals simply access holes for servicing? Adjustment? This kind of system would not give you the camber shape control that could be imagined if tracks were used, but it does seems more likely. If camber is controlled via outhaul, the range of outhaul positions is limited by the longitudinal width of that slot. Wide enough for a persons' leg, not sure how much wider than that. It would be interesting to look at AM to see what range of clew positions are used.
  2. buckdouger

    Luna Rossa Challenge. AC 36

    Interesting variable to consider. How would you define the power zone for starters (presumably a combination of factors define it, heeling moment arm, chord, available camber?) Would you think endplating moves this zone?
  3. buckdouger

    Luna Rossa Challenge. AC 36

    Continuing to look at LRs deck ovals, I mocked up a 'batten' and looked the locus of points from fixed locations along the length, which would correspond to the scenario of cars on the batten that ride the ovals as tracks on the deck. Without knowing the range of the main, it's clear that it still doesn't add up. The cars could equally travel along the batten (alone, or as well as riding tracks on the deck) but that would seem to get exceedingly complex. Edit: Side note, if we imagine LR only had straight tracks across the beam of the boat, any sail shape within that range could be imagined, but it would require the cars to slide along the batten because the locus of points of a fixed reference on the batten is not straight. This seems reason enough to believe that the cars don't move relative to the batten, otherwise the tracks should be simple straight lines. The idea of holding the foot of the sail for inducing camber and trim gets around the need to design the aforementioned bending boom of ETNZ, so it makes sense as a design direction from a superficial level. It is less versatile in trim positions, but much more versatile in location of max camber, which matches our expectations of limited AWA and the need to power up and depower across a wide range. Posting nevertheless in case someone else sees something here. Red - locus of points on the 'batten' Blue - straight line from mast to end of 'batten' Purple - a hypothetical LR oval 'track' to show it's a nonsensical interpretation Yellow - ...
  4. buckdouger

    Luna Rossa Challenge. AC 36

    Three different views from the launch day - low res unless someone cares to buy the photos at Alamy.com
  5. buckdouger

    Luna Rossa Challenge. AC 36

    I don't believe these were posted. Photo credit SailingSardinia.it, http://www.sailingsardinia.it/finalmente-mare-2/
  6. buckdouger

    Luna Rossa Challenge. AC 36

    Looks like at least 5 ovals
  7. buckdouger

    The new sailing twin skin setup

    Worth revisiting this to see if the parentage is there. Boomless
  8. buckdouger

    Boats and foils comparison

    Not seeing the righting moment difference given the required mass is the same for all teams. Another quote in the article from Nick Holroyd seemed to confirm @basilisus' comment that LRs outboard pods were housing actuators.
  9. buckdouger

    Boats and foils comparison

  10. buckdouger

    Boats and foils comparison

    Not sure I follow; the above numbers are simply a calculation of volume for required ballast using steel as an example. The above is simply a baseline, the comments about using tungsten and putting ballast in the connection to the foil arm are all valid directions, along with the bulb strategy.
  11. buckdouger

    Boats and foils comparison

    Not sure if this helps, but it is the combined effects in the 'elbow' of the two adjacent spans of material. Both the vertical and horizontal members locally increase the flow velocity by occupying volume, and in the corner, there is the least amount of space for the flow to pass, so it has to accelerate the highest. The local pressure dips down, and cavitates if unaddressed. The superposition notion is the combination of pressure drops from the two outboard sections to drop even lower in the middle section.
  12. buckdouger

    Boats and foils comparison

    As a baseline, if the wing, flap, fairing was all steel - at 7850 kg/m^3, 0.124 m^3 volume is required per side. Very roughly: 0.50 m avg chord, 0.11 thickness, Eppler 817 for example Max span 4 m (rule) Volume = 0.07317 m^3 in the foil wing
  13. buckdouger

    Boats and foils comparison

    This is pretty rough, but I am not sure I'd say that violates the rule just by looking, the linkages could be simply creating a virtual axis of rotation.