Erwankerauzen

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About Erwankerauzen

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  1. Erwankerauzen

    The new sailing twin skin setup

    @Mikko Brummer May be a little "sample" of lift distributions /downwashs along the span for different AWS ? But whatever the simulations you will run, I am looking forward to watch them. Thks
  2. Erwankerauzen

    head like a hole

    Yes, very strange decision, when you desesperatly need a win, and you are finishing the race with a sizeable lead..... Well, you are supposed to put the belt and the suspenders... Scott Anderson's mantra in his book "Advanced Catamaran Sailing", written in 1986 is: "In doubt, don't do it" I have insider information and I am sure at ETNZ, they have read the book. It is really a pity this happened, bcos, after first races, AMagic seemed well born , same for LR and then, when INEOS finally showing serious performances, all was in place for a good Cup without outrageous domination from one team. Would not like to be the head of the shore/repair crew of AM at the moment, some pressure for sure, but not from the wind. Hope they will recover quickly and be back competitive. Wish them the best
  3. Erwankerauzen

    Main sheeted to windward

    OK, but if the Coriolis effect is not that serious for sailing, what about the water spinning when the bath tub get empty? Theoricians suggest it turns in opposite direction whether you get a bath in Melbourne or in Paris!! well honestly I couldn't check!
  4. Erwankerauzen

    Main sheeted to windward

    Thks Enigmatically, long time ago Tornado crew training for Olympics explained me they accounted for Coriolis after each tack. But this discussion about gradient, is a bit my fault, I just misunderstood the adjective "Vertical" in Frogman56 post. While it is the correct wording, I just guess wrongly it was another gradient than the gradient along the span (vertical). I used the famous log law for my EXCEL spreadsheets to account for this gradient, and I "validated" it by comparison with the graph available in HPS by Franck Betwaithe. So far, just between 0 and 3 feet from the surface, we can observe differences between the HPS Graph and the Log law calculations. As a result, if you need it for foiling boats, the Log law is perfect. Cheers
  5. Erwankerauzen

    A-Class foiling sailors

    After some thinking, I wonder if it is the lateral distance which is important, or being in the same vertical plan (like the Moth) or not (like a cat) ?
  6. Erwankerauzen

    A-Class foiling sailors

    You are right Simon, of course, for the Moth, the lateral force comes from the horizontal main foil when heeled. But the longitunal position of this force is more or less aligned with the vertical strut, so it is not a game changer. If I try to make things a bit clearer : Would you increase the max beam of an A-Cat to become a "18 square", then you will have to move the centerboard closer to the front crossbeam, everything else equal. Have a nice week
  7. Erwankerauzen

    A-Class foiling sailors

    The longitunal position of the centerboards depends on the type of boat: 1-With a monohull, the centerboard and the sail plan are in the same vertical plan. 2-With a multihull which has her centerboards on the amas, then you must have a look at your boat from the top, put the resultant forces of the rig which must meet the opposite force from the centerboard, so the larger the cat or the tri, the more forward will be the centerboard relative to the rig. In conclusion, I would say that analogies between Moth & Multihull should account for that issue. Cheers
  8. Erwankerauzen

    Main sheeted to windward

    Thanks Frogman56, for your expertise. Is the Vertical Velocity Gradient significant ? How is it possible to mesure it? Cheers
  9. Erwankerauzen

    Main sheeted to windward

    Main sheet to windward, IMHO it is the consequence of ... Downwash . More Twist to minimize lift at the top in order to bring down the CoE will lead to a a lift distribution with more downwash at the bottom, consequently, if you want your bottom part of the sail to be put at full use, you need to bring windward the boom, in order to compensate for downwash and maintain the required AoA of the sail, at the bottom. Cheers PS: a bit disappointed by American Magic, was expecting a good fight from them, hope they will "recover" soon.
  10. Erwankerauzen

    High speed foiling mainsail control

    Thks Simon, Too bad there is no pic about this rig. the heru sail is just a double classic sails, so conceptually very far from a morphing wing. What is inreresting in the above interview, is that it confirms what a CFD guru used to say: "The sail makers and the CFD engineers do not speak the same language". But they are saying the same thing: The main feature of this double skin rig is managing the lift distribution, and therefore the downwash along the span to achieve the optimum in all conditions. That is probably "The Spirit" of the box rules regarding the rig, with the 4 top meters and bottom 1.5 meters allowance for internal mecanisms. Have a good week Cheers & fair winds
  11. Erwankerauzen

    High speed foiling mainsail control

    ThksUpp3, but your guy lives in Italy, not in WA, probably not the same guy ?
  12. Erwankerauzen

    High speed foiling mainsail control

    Interesting info, Thanks Any pictures available somewhere of this A-Cat rig? Cheers
  13. Erwankerauzen

    The new sailing twin skin setup

    Sorry NROOSE, but a foil with no thickness like a windsurf rig, seems to deliver significant lift, same remark for Moth or A-Cat rigs. But I would advise you not to pay too much attention to my above remark regarding thickness & lift, and instead you should read Basilicus's post. Cheers
  14. Erwankerauzen

    The new sailing twin skin setup

    Please read the windward skin cannot be cambered much
  15. Erwankerauzen

    The new sailing twin skin setup

    afair, thickness is not the criteria for high lift, instead it is the mean camberline which provides the lift. So, as your sail has inside mecanisms to control the camber, probably, the windward skin can be cambered much, and only until it touchs the inside mecanism, therefore the max camber is limited. But the leeward skin has no outside mecanisms which could limit the camber so it seems to be the only solution to get more camber in the whole section at the cost of a thicker wing section. Compared to a windsurf sail or Moth type sails, it is probably less efficient. With these little single skin sails, if you add 1% camber in the sail it provides 1% increase in mean camberline as they are the same. But for a twin skin, the windward one being limited by the inside mecanisms, you must add 2% of camber in the leeward skin to achieve 1% increase in the mean camberline of the whole wing section.