A couple of newbie questions
Actually meant to post only 2 place precision. Yes is only accurate to 1
decimal place. Bill "JAXAshby" wrote in message ... 3.21 x 3.21 != 10.3041 is only accurate to 10.30. correct me if I am wrong, but as I remember it 3.21 x 3.21 is only accurate to one decimal because the factors are accurate to only 1 place. I am pretty sure of that but it has been a while since I worried about "precision" and "double precision" numbers. |
A couple of newbie questions
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A couple of newbie questions
On Sun, 18 Jan 2004 11:57:33 +0000, Wayne. wrote:
On Sun, 18 Jan 2004 08:54:44 -0800, "Lloyd Sumpter" wrote: "Far Cove" Catalina 36 - hull speed 7.5kn, has seen 10 ============================================= Lloyd, what is your water line length (LWL) ? 30 ft - with a "fudge factor" of 1.35 gives hull speed of 7.4 knots. Easy to see 5, she will do 6 on a 10-knot breeze, 7 is a good reach, 7.5 is reaching on 15 knots, 8 is close-reaching on 25 knots or so... Lloyd |
A couple of newbie questions
On Sun, 18 Jan 2004 11:53:25 -0500, Wayne.B
wrote: The concepts being wrestled with here are "precision" and "accuracy". Precision implies repeatable results to some number of decimal places plus or minus an uncertainty factor. That is true. Accuracy implies the correct answer in absolute terms. Accuracy is related to how good (accurate) the data set is. For example, "accurate within 3 meters" is not an absolute - it could be dead on, or three meters off. Now if the phrase stated "accurate to within 2.987654321 =/- .0000000001 meters" - that is precise - you will always know that you will be within 2.987654321 +/- .0000000001 meters of any mark rather than somewhere within the accuracy range of 0 to 3 meters. Now I have a headache. Later, Tom S. Woodstock, CT ---------- "My rod and my reel - they comfort me." St. Pete, 12 Lb. Test |
A couple of newbie questions
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A couple of newbie questions
snip
The concepts being wrestled with here are "precision" and "accuracy". Precision implies repeatable results to some number of decimal places plus or minus an uncertainty factor. That is true. Accuracy implies the correct answer in absolute terms. Accuracy is related to how good (accurate) the data set is. For example, "accurate within 3 meters" is not an absolute - it could be dead on, or three meters off. Now if the phrase stated "accurate to within 2.987654321 =/- .0000000001 meters" - that is precise - you will always know that you will be within 2.987654321 +/- .0000000001 meters of any mark rather than somewhere within the accuracy range of 0 to 3 meters. snip I work with precision measuring devices and find that these are slippery concepts for most people. The shoddy day-to-day usage and close relationship between the two words does not make things any easier. See: http://www.ieee-uffc.org/freqcontrol...g/vigaccur.htm for a nice intuitive explanation of the difference between accuracy and precision. Mark Browne |
A couple of newbie questions
I can think of a thousand reasons why a boat MUST go over a wave,
nah. however I can only think of one reason why a boat MUST go through a wave and that is if it is heavier than water and is capable of passing through a wave. all boats pass through waves to some greater or lesser extent. Just stand at the bow and watch, or watch a Hobie cat go by (a displacement if there ever was such a thing) besides, the sine function claimed to support "theorectical hull speed" does not hardly EXPLODE at zero degrees. In fact, it is zero at zero. In fact, even at 2x hull speed it -- if it were accurate and it is not -- would only account for about a 40% increase in needed hp, while doubling the speed would required 800% more hp just to overcome drag. |
A couple of newbie questions
"JAXAshby" wrote in message ... and will only add that it is theoretical it is not even theoretical. It is and always was just scientific sounding gibberish. Welcome back Jax. We are looking forward your enlightening explanation of how to calculate hull power requirements. Mark Browne |
A couple of newbie questions
try Dave Gerr, for power required. He makes some dumb comments regarding theory
but his formulae are "close enough" to be more than useful for specific power needed for specific speeds for "displacement" type boats. Double check with your propeller vendor, and LISTEN to them, for they have some views that don't necessarily map one to one with DG's thoughts. btw, Bob Perry publicalycalled me "an asshole" (his words, several times) for pointing out that a sine function does not EXPLODE at zero degrees (in fact it does nothing at all at zero degrees), which of course means that tens of millions of people across the country are -- by Bob's definition -- "assholes" for knowing from sine functions. Welcome back Jax. We are looking forward your enlightening explanation of how to calculate hull power requirements. Mark Browne |
A couple of newbie questions
On Sat, 17 Jan 2004 22:20:54 GMT, "Calif Bill"
wrote: "Joe Parsons" wrote in message .. . [HAIRSPLITTING=ON] On Sat, 17 Jan 2004 19:57:18 GMT, Short Wave Sportfishing wrote: A nautical mile is also, precisely, 6,076.12 feet. That's not precise--that's rounded to two decimals. A nautical mile is, by definition, precisely 1,852 meters, as mentioned above. That converts to 6,076.11549 feet (which still is not precise!). [HAIRSPLITTING=OFF] I look at it this way - if I can get within four feet of something, I can holler at it. :) Now THAT is practical navigation! Joe Parsons Difference between an engineer and a mathematician. Voluptuous Dallas Cheer leader is standing nekid on the goal line. The engineer and math nerd are on the other line. Told that the first one to her gets her. Only restriction is can move only 1/2 the distance to the goal in any one move. Math nerd says 'won't even start, is an infinite series and will never get there.'. Engineer is moving and states, 7 moves and I am close enough for any thing I want to do. Joe, you a math minor in a business major? Bill Neither. I'm a writer. :) |
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