trenace

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About trenace

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    Ocala, FL

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  1. trenace

    Some of my old sailing photos 2

    Sailing Tyranny, the website encouraging unfettered discussion on all things sailing has commenced shutting down forum discussions at will. – you might remember it as Sailing Anarchy (SA) from years past. Usually attracting more than 50,000 visitors from Sydney readers and contributors, it was, until recently, the largest community driven sailing discussion site. Such a prestigious site attracts advertisers, media players, photographers and sailors alike, however this week, organizers from SA seemed more interested in getting negative publicity and member criticism than in gaining good exposure for their marquee website. At least that's the lesson learnt from SA officials this week, when they refused to comment on well substantiated claims by insiders of a breakdown in journalistic standards and ethics, and commenced deleting forum topics at will. As a regular reader, and sometime contributor to the forums, I and all other bona fide members of the site (as well as the general public) have been excluded from access to SA's most read and contributed forums of this week. The website has no problem allowing other forum topics to continue, but only if they do not criticize the editorial staff. Despite repeated requests by members, no reasons have been provided for the unilateral decisions taken. SA has also not responded to industry rumours that a leaner budget this week has resulted in smaller capacity within the forum database, the only logical reason for upsetting the forum membership. Due to the lack of feedback, this reporter can only draw on information listed in the 'About' page, namely, " Where the hell else are you going to have this much freedom to say what you want? After all, that is ultimately what Anarchy is all about" Officials would not respond to requests for an explanation of how deleting numerous forum topics fits the above commitment. Sailing Anarchy had a long and esteemed partnership with its members, but relations with the members broke down this week. Reasons for the breakdown were never released publicly, but given SA's apparent lack of interest in generating maxium exposure for the much lauded forums, the members probably made the right call. To Secure the vast majority of members for such a large forum is imperative for its quality and longevity, and only maximum attention to journalistic ethics and contributor selection due diligence can convince the large membership to get behind the forums. Journalistic ethics also ensure that the less prominent members – those that haven't abandoned ship yet – get return for their time spent in the forums. After all, deleting numerous forums before less active members have had a chance to complete their reading doesn't bode well for continued membership. SA officials seem to have no idea of these basic tenets, and their lackluster commitment to journalistic integrity and lack of response to member queries may contribute to a substantial fall of daily page visits in the coming weeks. Rumours are rife that SA has been hit hard by a failure to properly vet stories before publishing, and one can't help but wonder if their mismanagement of basic reporting duties isn't just the tip of the iceberg. It has also been reported that members are planning an "Occupy Anarchy" protest, where members will attempt to create as many forum topics related to the questionable reporting ethics as possible, scheduled for 12 noon 3/16/2012 USA EST. Will SA's premier member forum lose another 10 topics tomorrow, and each day onwards? Or will it crash under the unceasing pressure of the members. Will it survive at all? Not like this is won't.
  2. trenace

    Perry Sliver Class Day Sailor

    Done! Apologies for having failed at spotting your PM. By no means was it deliberate. My fault entirely.
  3. trenace

    DC Designs

    As an ignorant-but-quick answer -- hopefully you will get an authoritative one later! -- the allowed half angle would seem to be more than 22.5 degrees, as for example Gaijin appears to have a half-angle of about 33 degrees: http://forums.sailin...dpost&p=3504262
  4. If you have started the thread recently and only seen the near-completed hull photos I can see where that could look possible. From earlier construction photos, though, it's an absurd failure for structural strength. With regard to framing, it's clear that he consulted no scantling rules, did no engineering analysis, didn't do good guesswork, most definitely did not get it right, and MOST definitely the huge errors were not in the direction of strength. It seems very questionable whether it can survive even being hoisted. It's a heavy pig, but it's most certainly not a strong pig. Nothing like.
  5. trenace

    DC Designs

    Yes, one of the goals agreed and definitely, but I was meaning to say that the design wasn't optimized to be the best a board could be in that mode and is probably a fair bit from that, for the sake of planing performance. How much of a hit it is taking, I don't know. Apparently not too severe though, at least where there's enough breeze for people to be windsurfing at all. I do think it's very interesting how windsurfing designs are dealing with the combined needs of planing and displacement performance! Obviously a lot's been done lately.
  6. trenace

    DC Designs

    Perhaps if being flexible with definition, it does have rocker when trimmed for displacement mode, though certainly it's as flat as can be in the trim shown. If so then the deepest point is unusually far forward. But the board is really not optimized for displacement mode I would think. I'm totally guessing on the amount of immersion but as a mockup:
  7. trenace

    DC Designs

    Thanks; I see the article does have his e-mail address. Ordinarily I'd rather find out another way whether a design has been sailed, as it could come off as critical of the designer or a sore spot to ask, but on the other hand in this case there can be the polite aspect of writing to make sure of having his permission to build. (Not technically necessary to do as he posted it, but polite anyway.)
  8. trenace

    DC Designs

    Do you know if this design was ever built, or is it a computer file only? As the Freeship file is provided, I'd be tempted to build it if it's actually proven, as the Exocet is nearly $3000. Not that that's unreasonable for what you appear to get.
  9. trenace

    DC Designs

    Lift comes down to f=ma. Populist explanations such as "curved surfaces" are just that. The cause of lift is not molecules judging whether a surface is curved or not, or whether a shape is symmetrical or not.
  10. trenace

    DC Designs

    (No offense intended, just being humorous)
  11. trenace

    DC Designs

    His point wasn't that it is actually compressible, but rather that he saw a similarity between it being able to squish upwards (and store potential energy that way) and come back down as being somewhat analogous to being compressible. Though it is unclear to me whether there is a usefulness in looking at it that way.
  12. trenace

    DC Designs

    Well, as an utterly amateur and quick look at it, if we mostly push the water forward, then there will tend to be a heap of it (or some amount anyway) in front of us, which can't be good. If on the other hand we tend to push it more to the sides (narrower half angle of entry), then that would seem better in that regard. With regard to filling in the moving hole, that's going to happen in any case and it's not obvious we have any control over it or whether it matters, except that the more waves that are created, the more energy must be lost to do that, as you point out. Whether for a given half angle of entry (or length to beam ratio; I don't know which is the better way to look at it) and DLR and considering hulls that are good designs, one can really do anything much about further reducing wave-making drag, I don't know and I'm happy to stipulate Chris's position that this is not the place to look.
  13. trenace

    DC Designs

    At 2 bar of pressure, there can be cavitation from sharp hull geometry changes at around 60 knots ( http://proceedings.f...cuments/514.pdf ). This is with respect to submerged craft. This was not a sharp value where cavitation suddenly appeared, but is an example speed (actually 30 m/s) where it was a substantial effect. At 1 bar (atmospheric), I don't know what the relation would be... perhaps 70.7% the speed as a guess? As that would be half the kinetic energy. In that case, somewhere around 40 knots? I had never seen cavitation raised as a concern with regard to the hulls of sailing vessels. I would attribute bubbles to entrained air.
  14. trenace

    DC Designs

    Agreed that such wording is vague. But when something varies over a range, trying to break it into two or three parts will tend to be vague, unless there are sharp transitions. Which often there are not. But if using the word "significant," then so long as there is no significant displacement reduction, I don't think there's any significant drag benefit from the dynamic lift, either. Certainly no significant reduction in wetted area, if no significant reduction in amount of water displaced. Of course if the boat design has transom still immersed at lower speeds, then yes, breaking free of that will give a significant benefit. But not if the static transom immersion was a value that would be appropriate for both speeds. I would see it more as paying a penalty below that speed from having excessive immersed transom, then a benefit suddenly appearing at that speed. Other than, correct immersed transom for the speed is always a good thing, with this amount being zero or near zero at low speed and increasing somewhat as speed increases.
  15. trenace

    DC Designs

    If you've got a big bow wave in front of you, from your DLR and your half angle of entry, then the stern no longer being supported by the stern wave doesn't in and of itself reduce the work of pushing through that bow wave. What does aid is that per unit time, a mass of water is being accelerated downwards such that it exits the transom cleanly. At lower speeds, the force resulting from accelerating this mass of water is not so much and doesn't reduce displaced volume much. At high speed, and assuming transom immersion is an appropriate amount, it is a large force and does reduce displaced volume to an extent that can be very beneficial.