Doug Halsey

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Everything posted by Doug Halsey

  1. Doug Halsey

    Beginning Moth - first attempt = failure

    When there's no wind is absolutely the hardest time to get into the boat. I would definitely advise you to learn when there's a little more breeze. But if you insist on trying, and you find that you can't make either method work, here's something else you can try: a variation of the waterstart, where you start from much farther aft & pull yourself in with a forward motion. Without the line between the wingbars, you can even start from the transom. You'll find that the boat is much more stable fore & aft than sideways, and you should be able to get in that way even when there's no wind at all.
  2. Doug Halsey

    Foilers: brushing off seaweeds?

    Reattaching flows are very tricky though. What helps for one type of boat in certain situations may possibly be the wrong thing for another boat or in other situations. I would like to see some hard data about it.
  3. Doug Halsey

    Foilers: brushing off seaweeds?

    Is this true? Can you explain it or point me to any references?
  4. Doug Halsey

    Moth decksweeper and lowered mast stumps

    There's an old thread on the boat design list with lots of examples of multiperson monofoilers: https://www.boatdesign.net/threads/new-high-performance-monofoilers.25366/
  5. Doug Halsey

    2018 moth worlds - bermuda (march 25 - april 1st)

    Some preliminary racing in Florida a couple of weeks ago... http://usmothclass.com/2018-us-nationals-recap-struble-wins/
  6. Doug Halsey

    Moth Foiler & Back bone issue

    Phil: I know that Chris Rashley had a serious issue with his back just prior to the 2015 Worlds, but was still able to compete & place very near the top. Do you know more precisely what his injury involved and what he had to do to cope with it?
  7. Doug Halsey

    Super foiled configuration

    Here's another moderately successful attempt with bow mounted foils. Gary Seaman (who also sailed sailboards in California) won a speed-trial against the D-Cat Beowulf in about 1972. That was in fairly light conditions (but still foiling). The boat was quite a handful when it blew harder though.
  8. Doug Halsey

    EC2018 Thread

    CCock & DeSea aren't shown as having made CP2 yet. They didn't skip it, did they?
  9. Doug Halsey

    EC2018 Thread

    WaterTribe: https://www.facebook.com/groups/440773022707818/
  10. Doug Halsey

    Everglades Challenge 2018

    https://www.facebook.com/groups/440773022707818/ http://www.watertribe.com/Default.aspx
  11. Doug Halsey

    Can we save Portsmouth handicap racing?

    Like this? (Figure from Ian Ward)
  12. Doug Halsey

    SuperFoiler Grand Prix 2018

    So far, they're not entered. https://www.regattatoolbox.com/entryList?eventID=WYEX9X6zFL
  13. Doug Halsey

    C-Class Little Cup news

    That's pretty funny! I do happen to be a retired aero engineer with some CFD experience (not that it makes any difference). I'm not sure why Erwan was admonishing me to pay attention to your posts; I thought we were saying essentially the same thing.
  14. Doug Halsey

    C-Class Little Cup news

    Are you sure you're computing the speeds correctly? Your saying "Sum of all drags = driving force (@ constant speed)" makes me doubt it, since the aero & hydro drags act in very different directions & cannot be simply added. I also think you would need something more powerful than a hand-held calculator to do the calculations. Even the relatively simple VPP's that I've written require several hundred lines of code.
  15. Doug Halsey

    Moths in Annapolis/DC

    Maybe you could ask at one of these sites, or directly email the officers:
  16. Doug Halsey

    Wing Sail Design

    Thom: I don't think that max lift is the desired condition very much of the time (even assuming that the boat isn't overpowered). As you mentioned, it doesn't give max thrust (except for apparent wind angles of 90°). At smaller apparent wind angles, I think a lift coefficient somewhat larger than the value for max lift/drag, but smaller than max lift, would be the aim. The attached figure illustrates how a solid wing can be better than a soft rig in that range. It was taken from a paper by Sam Bradfield, analyzing the results of the last Little AC won by a soft sail. http://vm2330.sgvps.net/~syrftest/images/library/20160306205859.pdf The solid wings of that era had simpler hinged-flaps, so the newer wings with slotted flaps should have an even greater advantage.
  17. Doug Halsey

    14' Stunt S9 Foiling Cat

    This is also just a guess: If the boat is allowed to slow down too much prior to the gybe, the apparent wind angle can change quite a bit. Having more twist ensures that at least part of the sail will be trimmed properly, in that case. Of course, it's better to maintain as much speed as possible during the gybe to keep the apparent wind forward. If that is done, the boom does not come across violently; it's more like a tack in light-air.
  18. Doug Halsey

    Wing Sail Design

    I think you can download AMO's paper for free here, but you have to sign up 1st: https://www.scribd.com/document/81116884/High-Lift-Aerodynamics
  19. Doug Halsey

    Wing Sail Design

    Here's a link to the Scherer article: http://mararchief.tudelft.nl/file/39710/
  20. Doug Halsey

    Wing Sail Design

    I think the max-camber location is probably less important in a multielement wing, at least partly because the boundary layer gets to start fresh at the leading edge of each element. The best starting point for understanding the theory is probably still AMO Smith's 1975 Wright Brothers lecture. I couldn't find a link to a free download (yet), but this more recent reference summarizes part of it: http://www.dept.aoe.vt.edu/~mason/Mason_f/HiLiftPresPt1.pdf Some interesting experimental data for models of actual C-Cat wings were published by Otto Scherer in Marine Technology. I'm also still looking for a link for that.
  21. Doug Halsey

    Foils

    I'm getting one of these:
  22. Doug Halsey

    Moth Developement

    Since you're asking about older Moth designs, you might be interested in this: http://www.mothboat.com/ Nothing much about scows though, since there weren't many of them in the US.
  23. Doug Halsey

    Origin of VMG as terminology

    Apparently Einstein was a big fan of his too, calling him "the greatest mind in American history," according to this biography: https://www.aps.org/programs/outreach/history/historicsites/gibbs.cfm
  24. Doug Halsey

    Moth - adding bladder to tramp

    I think that learning to sail the Moth is difficult enough without adding to it by going without the bladders. Apparently, even some big names in the Moth World agree with me. Chris Rashley describes them as "absolutely critical" in this link https://www.youtube.com/watch?v=m4OWY1MgZIU And Nathan Outteridge praises them in this one: https://www.youtube.com/watch?v=FlQi0Vxh1-w