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  1. Spoonie

    don't mock me

    Mmmm... is that cardboard? the front is definitely going to fall off that one
  2. Spoonie

    ticky tack?

    frankly, y’all should learn to float a kite. human poles in a takedown? luxury...
  3. My parents are cleaning out, but in their position was a book of mine I specifically asked them to keep: "Catamaran Sailing To Win", Chris Wilson & Max Press , 1973 Which you can amazingly still get on Amazon https://www.amazon.com/Catamaran-Sailing-Wilson-Chris-Press/dp/B002I7IKCI There was a bunch of reasons I wanted to keep it, but one of it was the notes around the design and campaign of "Miss Nylex", I think one of the first, if not the first solid wing C class. It was also apparently quite controversial in the use of "Nylex", it's sponsor, as part of its name. Anyway, very much old hat now, but I thought some of you might find of interest the short note and drawings by wing designer, Roy Martin on the benefits of rigid wings (circa 1971). The justification for one of the first wings in Catamaran racing we now know and love in the Americas Cup. Cheers Spoon. MissNylexWing1.PDF MissNylexWing2.pdf MissNylexWing3.PDF
  4. Spoonie

    Showtime capsize on return trip

    My wife thinks this is a forum about Sailing
  5. Spoonie

    I'd like to thank the previous owner for...

    Someone in my previous owner history used metal tacks to attach the figure 8 wire to the bulkheads. apparently didn't get perfectly centre in a few places.
  6. Spoonie

    Showtime capsize on return trip

    I don't know where you go it, but I posted it in reply to you up above. It's not a proper keel test. They're attempting to validate design assumptions on acceleration and forces, as opposed to confirming the failure mode of the as built design meets expectations. One of those boats in that paper would go on to have a catastrophic ram failure though. A good example of a proper test would be the work that went into the de Havilland Comet https://en.wikipedia.org/wiki/De_Havilland_Comet I would suggest such a test is cost prohibitive in most yacht design scenarios.
  7. In the old days, the North MK I was a softer cloth and routinely a flatter head than the hyde MK I. From my experience, there was also about a .4kg difference between light and heavy top sections at the dealer (2.2kg to 2.6kg from memory). I think the Aussie top sections seemed like a harder temper though. I also felt the aussie bottom sections were stiffer as well. Maybe psycho sematic. We did weigh a lot of top sections though. I haven't sailed with a MKII sail or carbon section. If the carbon sections are at least consistent from batch to batch, that has to be a good thing! Edit: looking at other top section weights, maybe my memory was a little off. I certainly remember 2.6kg. I had it in my head that the other was 2.2, but that seems a long way from other weights listed online.
  8. Spoonie

    Showtime capsize on return trip

    Nah... as an applied mathematician, it's a guesstimation. you build a model, plop in some boundary assumptions & conditions, and spit out some numbers. Your model could be wrong, your assumptions could be wrong, or both. Chances are you're wrong somewhere. They're certainly called assumptions for a good reason. Newtonian physics being what it is, they could be highly educated guesses, but they're still just an approximation of the real thing. Especially when you add hydrodynamic loading into that picture. You can see from the paper I posted above, the numbers used were relatively arbitrary. 1G loadings with a safety factor of 3 using "quasi-static analysis". In testing, Hugo Boss bumped up against those numbers from time to time. WOXI was a little more comfortable inside the comfort factor, but definitely over the 1G spec. 1g and 3x are too convenient for me. IMHO someone's made an educated guess. Maybe there was some real data that informed those numbers who knows. In some circles though, breaching the comfort factor would be considered an engineering failure. Either way, as fastyacht pointed out, race boats are experimental engineering. There's precisely one of them (in many cases) built to withstand at a bare minimum, the structural needs to get them around whatever race course they're on. With all due respect to the NA's here, to suggest they have a perfect understanding of the dynamic loads placed on those boats, I think would be giving them a lot of credit. Especially the big fancy ones (Boats, not NA's) *shrug*
  9. Spoonie

    Showtime capsize on return trip

    No such structure exists. Everything has a failure mode. One of the practices in building resilient systems is to assume the element has failed and then assess the impacts across the rest of the system. All too often people try to guess why it might fail. If they can't, they assume the risk to be minimal. this can lead to solution designs that are inherently less resilient to failure than other options. Even experienced engineers are not immune to this and there are many famous examples (like the challenger disaster) where an assumed low risk proved to be vastly inaccurate. I know little or nothing about keel design, but back of the envelope, even a forged keel will have failure points. The bolts, the hull structure, the right angle flange at the top of the fin, thinner material mid span to the bulb. Lots of opportunity for failure, but perhaps more reserved capacity for failure in the system. There was also a presentation at the Institute of engineers (I think) a few years back. One of the big boat programs here put a load cell on their keel and I think were genuinely surprised by the extremes of the dynamic loadings. That led them to update their keel maintenance & inspection program but I think was still within design parameters. I seem to remember a paper on it, (maybe this one?) but I can't be arsed looking for it too hard. That paper above though suggests the loadings were as high as the "ultimate loading" they thought the keel would endure, but also that the nature of those loadings was pretty specific to each boats design. I guess that leads to one of the earlier assertions about guesstimating the loads. At any rate, I guess that's a long way of saying in any dynamic critical system, you're always better off assuming a component might fail, and acting accordingly than the opposite
  10. Spoonie

    Cancelling a Race for High Winds: No limits in SI's

    Crazy Ivan.... when i was mountain biking lots I went riding with a mate. We were elbow to elbow down this trail drifting through corners with shear drop offs on the outside. It was fun because we trusted eachother’s capability implicitly. I have the same implicit trust (and distrust) of my fellow skippers. some I outright avoid, others I have no quams about being gunwhale to gunwhale with knowing that should something go pear shaped, the other would respond. I’ve come to expect even great sailors have the odd crazy ivan. It’s how you both react when you are close that makes difference between fast, fun, and safe. As to abandonment, as Fast said, devil is in the details. I would have thought that was a bit soft, especially because it was closed flat waters, but maybe Im missing something. I certainly agree documenting wind speeds makes things more complicated. unfortunantely here, racing will be cancelled on strom and gale force warnings regardless of conditions. that’s a liability issue. On the flipside, i’ve had arguments with RO’s who refused to abandon despite active lightening storms on course. The RO had the idea that lightening would go aound the boat, and besides, his kid was winning. That day on another course a laser was struck, exploded, and the sailor found himself in hospital for a week. on our course another boat returned to shore after apparently experiencing an electric shock holding on to the stay. That club developed an explicit storm risk policy after that as part of their risk mitigation plan, providing clear guidance to RO’s introducing greater consensus and the ability for the executive team to overrule the RO on such things if it was deemed appropriate to do so. it was a policy document though, not an SI.
  11. Spoonie

    Australian Sailing

    QYA has had interesting things going on as far back as the late 90's.
  12. Spoonie

    wtf Australia what is yall doing??

    well on the bright side, it should provide some phd candidate with a nice little bit of research on global wind patterns.
  13. Spoonie

    wtf Australia what is yall doing??

    i have a maths degree (dynamic systems mostly). I’d say the maths component of that was pretty tough. just say’n
  14. Spoonie

    Non-furler headsail handling options

    Outside gybe with a 2m strop between your sheets and the chutes clew. The strop acts a bit like a delay fuse when you madly pull the sheets through. For me, the problem is dropping the lazy sheet in front of the bow. You need to somehow keep the sheets tight while letting the kite blow forward. Hence the strop.