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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.  

Erwankerauzen

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  1. 14' Stunt S9 Foiling Cat

    Sorry ACS, your argument is not correct, It is not 10 to 15 years, it is more than 20 years they do not have any meaningfull results in the A -Cat series. And to be totally transparent, they achieved their results only in Europe when the fleet was at 90% bimare, so no actual competition, but a handfull of plywood-DIY attendees. As soon as Goodall /Boyer boats were available in Europe, they disappeared gradually from the market. The problem they have is very simple: They have no actual R&D . while they have been operating in a very competitive environment: Where Greg Goodall is ingeneer, Mischa too and the same for Jackub which in addition is cooperating with a designer who has experience in the AC. The Petruccis used to market Tornado until Fred Le Peutrec* saw his bimare Tornado self desintegrated in "Baie de La Baule" in 1992. * French competitor in Tornado @ Olympic Atlanta / Savannah 1996.
  2. 14' Stunt S9 Foiling Cat

    ITA16, You should not focuse on trying to demonstrate your S9 can keep up with A-Cat, especially windward. A quick look at your sail plan, its aspect ratio, with or without the jib, gives clear insight on the S9 potential. What I say is: your boat as already a strong disadvantage since the drawing board. You just need to crunch a few figures related to the "EFFECTIVE ASPECT RATIO" of your S9 to understand this point. And according to the actual apparent wind angles on foiling boats, what is relevant windward is also relevant downwind, as the change in AWA is tiny when going from 45° to 115° of TWA. Of course, this remark is relevant only if you actually crunch any figures before designing a boat, don't you??
  3. DIY Wing Mast Questions

    Very interesting experience, thanks for sharing. Before construction, some structural engineering must be performed to know how many carbon's UD or Bi ply must be used. Any suggestions on how to make these calculations for a rookie in structural engineering? Thanks in advance Happy Sunday
  4. The winning foils

    Thanks Hoom, If ETNZ used to sail with the tip horizontal, then my former remark is totally irrelevant. Sorry, I apologize for this disinformation, just forget it. Obviously, the reverse engineering of winning foil is not a trivial exercice. Regards
  5. The winning foils

    Foil wave drag is addressed (among all other foil drags) in a Cheasapeake workpaper about the Moth. It is a few years old document, but still interesting, cannot find it among the hundreds of CFD pdf I have on my laptop. Should be findable on a Moth thread. Regards
  6. The winning foils

    Thanks for posting these nice pictures of ETNZ Foils, What is interestiong is to imagine the lift distribution of the upper part of the foil: And according to the "Horizontal" part and the tip part kinked upwards, one could imagine or "reverse engineered" the design philosophy, or a part of it. Among many sources of drag there is a more or less marginal component of drag for a foil which is the WAVE DRAG, and digging in the theory, one might find that this "foil wave drag" is prop of squared lift coef and inverted proportional to foil depth. (Not 100% sure, but that's the spirit / check by yourself) So the flat part gives the max lift and the kinked tips have their lift decreasing in order that the couple of variables (local lift, depth) remains similar all along the foil span, in order to minimize wave drag along with induced drag, and friction drag Sorry if not that clear, hope some specialist would provide clearer explainations Regards
  7. Back to real world issue, I would like to know if the following suggestion is already at full use on bomless decksweeper or not yet. According to my ancient experience with an A-Cat boomless package (but not decksweeper) the problem was simple, as soon as you ease the main because overpowered, the sail start to get fuller in the bottom before twisting at the top. In order to address this problem: I wonder if it would be possible to use much stiffer low batten, close to the clew , and a pulley block slightly oriented to the front (clew point should be a little behind the circular track ) in order to bend the batten when pulley block is under tension and let the batten straigthen when the tension is released? It is probably already the case on A-Cat DS sails, but I would be happy to have confirmation. Looking at the problem from another perspective, one could think that decksweeper sails can have a lot of camber at the bottom, in any situations, and whatever happen when easing the main, it has little effect on a sail shape already "full". Regards
  8. A Cat Worlds Sopot

    Thanks for these relevant informations
  9. A Cat Worlds Sopot

    It seems the big wing mast prototype did not attend the Polish championship! did it?
  10. A Cat Worlds Sopot

    Hi Mates, A few ° rake is not a good reason enough to fight on the forum, d'ont you appreciate this peaceful atmosphere without Doug getting on the nerves of everybody with his uptip obsession??? It is Holidays for Anarchists, just enjoy!!! If I wish to get a few relevant numbers for the mast rake, just to see how much the sail CoE will move forward with a wing instead of a teardrop mast + sail. The wing has no leech and pulley block to retain the rig to move alone forward, so a minimum rake is required from the design table. But if classic rigs allow good foiling with 0° aft rake, I am f&#ked, the idea would not be that relevant But with 3.5° to 4 ° aft rake, a wing will allow to move the foils closer to the main crossbeam That is just insane curiosity, Thanks to all
  11. A Cat Worlds Sopot

    if the hound is at 6 meters height , and the shroud attachement 50 cm behind the mast foot. then at 5° the hound is aft of the vertical of the shroud attachement on the gunwhale.. I was expecting something between 0° and 4° ???
  12. A Cat Worlds Sopot

    Has anybody a idea of what kind of mast rake is used for the foiler in middle wind condition ? If in ° it would be great. Happy world for the lucky attendees
  13. Sail twist simplified

    MultiThom, You are perfectly right, I mentionned figures from memory, and my Alzheimer mislead me: Windward with 13knts TWS and 45° TWA with boat sailing @ 13knts at 18 feet height AWS is 24 knts and AWA is 22.5° at 6 feet height AWS is 21.6 knts and AWA is 19.86° at 2 feet height AWS is 19.3 knts and AWA is 16.58° Downwind with 13 knts TWS and 115° TWA with boat sailing @ 17 knts at 18 feet height AWS is 16.4 knts and AWA is 45.6° at 6 feet height AWS is 15.74 knts and AWA is 36.8° at 2 feet height AWS is 15.42 knts and AWA is 27.3° In the same conditions for a foiler sailing around 20 knts windward and 26 knts downwind twists are reduced by circa: 40% . Happy Sunday
  14. Sail twist simplified

    Sorry, I am not a digital native, I guess you can rotate the picture by 90°
  15. Sail twist simplified

    Multi Thom, It is only about turbulent BL