Richard Feynman on doubt, uncertainty and religion

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Outfitting for the 2008 Sailing Season

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A few days ago I ordered a C-map SD card for my Furuno chartplotter to cover my intended navigation area: Eastern Med. I ordered the m-em-m003: Mediterranean, Aegean, Black Sea and much to my surprise I received a card labelled m-em-m917. Apparently C-map has updated their product line from "mega-wide" to "mega-max" and the retailers haven't bothered to update their online catalogs (I use Waypoint out of Alameda, CA). If you're in the market make sure and get the new mega-maxes they cover the area of two mega-wides for the same price.
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The Math and Physics of Anchoring

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Ref. http://trimaran-san.de/die-kettenkurve-oder-wie-ein-mathematiker-ankert/ In a nutshell, the main results are : The guidance of using a fixed scope like use 3 times or 5 times the water depth as length of chain, etc., is not adequate. It is not enough in shallow water, and it may be too much in very deep water. And it does not depend on the wind strength at all, which is rather odd. We consider this guidance to be dangerous, at least for the novice. Our results do depend – among other parameters – also on the wind strength. Neglecting swell and waves, the result is very simple, based on the catenary equation: Minimum required chain length is L = square_root( Y ( Y + 2 a )), where the parameter a depends on the wind strength, on A eff , which is the effective cross section of the vessel towards the wind – i.e., the windage area – as well as on the mass m of the chain per meter. Y is the water depth at the anchor (and not the vessel!). This simple non-linear catenar...
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