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erdb

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542 F'n Saint

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About erdb

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  1. Are there any rules that prevent SailGP teams from building their own surrogate cat/wing for training? If teams start to take this series seriously, time spent training between races could be a major factor.
  2. I think they had issues with the boat. Even the commentators mentioned something about their hydraulic problems on day 1. Interestingly, at one point they were 1st in the first downwind leg on both days. Then came a horrible jibe/mark rounding, and they would never be back up to speed for the rest of the day. Their windward board seemed to be a bit wobbly in the finish of the 3rd race on Day 1. Is that normal? "Happy just cruising here, right?"
  3. I've never been annoyed this much watching otherwise excellent racing or in fact any sailing ever. The sailors and sailing are awesome, boats are good for trashing around short courses - how can they screw up everything else so badly? Which genius thought they should film the pre-start head on from the other side of the Atlantic? Who thinks viewers like kph more than kn, when every sailor interviewed talks about knots and the commentators keep converting kn - kph back and forth all the time. Remember the obsession with the 50 knt barrier? Is it now going to be the magical 92.6 km/h
  4. I doubt anyone would complain here about a little thread drift while we're waiting for the next AC . I'd love to see more pics of that proa and an explanation of how that rig works.
  5. Yes, I understand all that and I agree. I just thought it's interesting how the seaworthiness of the boat was never part of the debate. If Dean knew that with a bad bear-away he's risking the boat and the whole program, he would have never tried it. Yes they did have some bad races in the RRs, but they actually sailed really well in the ACWS. So it's not like they were inherently bad. They could have turned things around just like INEOS and LR did at various points in their campaigns.
  6. While I agree DB wasn't the best choice for helmsman, I think it's unfair to blame it all on him. Yes, it was a stupid risky move during a race that had no real importance, but I'm sure no one even remotely considered that punching a hole in the hull was a possible outcome. PB capsized TR twice and the one during the practice race was pretty violent. Yet, the boat was righted and suffered no major damage. You could argue AM also needed to practice that kind of mark rounding if they wanted to make it to the AC. The AC75s were well known for this type of broach and capsize. Patriot should h
  7. They had this low speed mode when only the keel was in the water, but the hull not. From there they could pop up any time. Getting up from full displacement mode would have taken much longer.
  8. I think it's reversed. If you want small foils, you have to go with T foils.
  9. There is another plugin: https://lukemiller.org/index.php/2011/09/digitizing-data-from-old-figures-with-imagej/ With this, you have to click on data points you want to save, so you're back to manual drawing, but the nice thing is you can calibrate your image to export coordinates in the 0 - 1 range right away. Cool project BTW!
  10. Hey @MaxHugen and @Basiliscus , check out ImageJ - a free image analysis software developed at the NIH. It has a line graph analysis tool that does exactly what you want. Long long time ago, I used it to digitalize paper recordings from physiology experiments. Just tested it in the current version and it works like a charm. Converts a line drawing straight into a csv file or copy to excel. You will have to do the top and the bottom separately, because it's looking for a line graph, you can't have two Y values for the same X. Download Fiji (Fiji is just ImageJ - literally ), it has al
  11. Does chord length (and Re) have any effect on the onset of cavitation or on how cavitation affects drag? Just wondering if the real benefit of the T foil may have been the simpler flap mechanism allowing reduced thickness and therefore chord length -> less adverse effects from cavitation.
  12. Yes, when I made my VPP, I included rudder vertical force, too. Rudder downforce increases righting moment, but it also increases drag. Initially, I always had downforce on the rudder, but as I played with parameters like location of CG and pitch angle of the boat, I found that upwind performance was best when the rudder produced a slight vertical lift. Reaching angles (mark rounding) however require a lot of rudder downforce, and downwind as well depending on wind strength. Rudder and foil vertical forces: (As the rudder produces more downforce, the foil needs to produce more
  13. Are there any rules that prohibit wearing some kind of fairing that could reduce the drag of a hiking human body? Sure it would be torture pumping the main downwind in a costume like that - but in theory...
  14. Just to complicate things even further, the answer depends on whether you look at a T foil or a Y foil. What's unique in the AC75's foils is that the lateral and vertical forces are coupled. In the foiling catamarans, the vertical and horizontal surfaces of the L foils handled the vertical and horizontal forces (mostly) separately. However, in the AC75, the same foil generates both forces. For the T foil, it's fairly simple: The lift generated by the foil (L) is perpendicular to the foil wing. You can figure out the angle (a) relative to vertical for any cant angle from th
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