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      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  

Doug Halsey

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Everything posted by Doug Halsey

  1. What assumptions did you make about the velocity gradient in the Earth's boundary layer. In other words, what was the difference in true wind speed & over what distance?
  2. What's a Cb?
  3. Mach2.3 Vertical is ~41 1/2", measured the same way. The older Mach2 vertical is ~2" shorter, I believe.
  4. I find it pretty strange that you're using the past tense & referring to Moths as "ancient foilers." The class is doing just fine in many parts of the world, and the boats & foils continue to evolve. Nevertheless, I'm curious about Gacking too. I know it has been done in the Moths, but I wonder how common it ever was & whether its use has diminished as the best sailor's ability to do foiling tacks has improved. It would be pretty incredible to see one of the AC teams pull it off though!
  5. The SpeedPuck (like the other Velocitek products) stores a file that can be downloaded to a computer & analyzed in software like GPS Action Replay to display the boat's performance. If Tom would make at least one of the Astus's files public, that would help a lot in evaluating his speed claims.
  6. When I tried to get insurance from BoatUS for my Moth (3 years ago) , they told me they wouldn't insure any boats with hydrofoils. Try Gowrie Group.
  7. Sorry about that! I know the 14's are great boats & I'm glad to be wrong in this case.
  8. I don't think you'll come across many I14's in San Diego, but we've got an active & growing bunch of Moths at Mission Bay YC. Currently ~8 Mach2's & several older BladeRiders. 6 mph would be a very light-air day; more typically around 10mph or more in the afternoons. Enough for >20knot boatspeeds most days. Lots of fun! And rotating masts & other innovations are definitely allowed.
  9. You don't have to consider cant angles & leeway to find examples where having a slight V can be advantageous. It's an established fact (backed by both experiments & numerical calculations) that the induced-drag efficiency factor improves as the angle of V increases. At higher speeds, the increased wetted area & possibly sooner tendency to cavitate make the V foils have more drag. But at lower speeds, the induced drag becomes more dominant, often resulting in smaller total drag. So, it's not really surprising that the light-air foils might have more of a V shape.
  10. From the Racecourse description: "Please note: Racecourse orientation and length may vary based on wind direction & strength." So you can bet we'll see some shorter courses in lighter winds. My question is whether there is any minimum length for the course?
  11. And might some of them already be prepared to do that?
  12. Since the helmsmen can control the foil incidence, shouldn't they be able to help avoid this situation in the future by learning to reduce the AOA whenever they round up?
  13. I'm not sure exactly what the research shows, but you only mention generating more lift. So, what about conditions where the boat is fully powered up & they need to trim to minimize drag?
  14. +1000!
  15. I do appreciate your comments & was just making a lame attempt at a joke. I'm not really as grumpy an old man as I sometimes seem.
  16. I think Estevie Norman must be another name for Steve Brewin, but WetnWild is also telling us he's part of the same inner circle.
  17. I doubt if these diagrams are the results of any calculations. They show the magnitudes of the forces to be the same for the upper and lower wing sections, giving an exaggerated picture of the importance of the tip. In reality, the upper forces should be smaller, by an amount that depends strongly on the wing's planform & twist distribution (as well as other details of the shape).
  18. When I 1st read this, I thought you were just misspelling "Okoume" & was surprised you could find it at a big-box place. But a little Googling showed me I was wrong & there actually is something called "Okuma." Can you tell me how they compare?
  19. Those are all too slow to stay on the foils, aren't they?
  20. When I click on that link, I get my videos again & it gives the following as the url: https://www.youtube.com/my_videos?o=U They must have folders with the same names several places, making it tricky to know the right one to paste into your posts. I don't entirely understand it either.
  21. I watched the 1st video & was especially interested in the portion after about 5:15, when the boat is on starboard tack & you can see the wake from the forward foil sweeping aft & sometimes impinging on the aft foil. At times some spray from the rudder/aft foil is visible above the crossbeam, but it doesn't seem to correlate with when the forward wake hits the rudder. Are you aware of any effects from this kind of thing? I was going to let you know that I've made some crude attempts to get videos of the same phenomenon on my Moth, but I see from the 2nd link that you already know that. It's interesting to read about your experiences with the S9 & to watch the videos. It looks like you're having lots of fun!
  22. Since the very concept of hull speed is all about wave drag, zero wave drag implies no hull speed (or perhaps infinite hull speed). Exactly! Instead of "extraordinary," maybe I should have said "impossible", "absurd", or something stronger. But I don't think Amati wants to hear it. I do want to hear it. But FWIW I was one of those unfortunates who couldn't replicate the Millikan Oil Drop experiment and paid for it. So when I say, as I did, that models are an opinion, I actually meant it. Granted, my argument was an appeal to authority, while yours seems to be 'it's just a pile of shit.' Which is basically what self appointed enforcers were doing with the Oil Drop Experiment. Resistance isn't all wave related. I think skin friction is resistance too? Am I wrong in thinking that waves are a result of a hull (in this case) displacing water at a speed? And waves exist because of the gravity interface between water and the atmosphere? Different hull shapes create diffferent waves, and different resistance- if that is the case, it seems a little arrogant to proclaim a truth that something is true based only on supposition. Hypersonic flow does exist. Large Boats do plane I think your assertion is a very practical one based on current knowledge. But if I was willing to actually build a model, and try it out based on what I have at hand, other that your impatience with my apparent stupidity, why the condescension? I'm not denying physics- I'm trying to understand physics in a more personal way. I'm sorry if I came across as arrogant & condescending. I only intended to point out a couple of matters that I thought were well-established (not my personal suppositions). In any case, we shouldn't let that distract from the more interesting questions concerning proas, and I hope your experiments will help shed some light on them.
  23. Since the very concept of hull speed is all about wave drag, zero wave drag implies no hull speed (or perhaps infinite hull speed). Exactly! Instead of "extraordinary," maybe I should have said "impossible", "absurd", or something stronger. But I don't think Amati wants to hear it.
  24. You've probably heard the expression "Extraordinary claims demand extraordinary proof." It would be pretty extraordinary if someone could design a hull with zero wave drag at its hull speed. What's the extraordinary proof? That the code developer used to work at Boeing? That your boat could sail with a keel that he designed? That you built a cool boat? I don't think so!