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You've got it reversed!
10 nm (Nautical Miles) equals 11.5 Mi. (Statute Miles). 5,280 Ft in a Mile, 6,076 Ft in a nm.
10 nm (Nautical Miles) equals 11.5 Mi. (Statute Miles). 5,280 Ft in a Mile, 6,076 Ft in a nm.
No
If 1 nautical mile = 1.15 statute mile then 1 statute mile = 0.8695652 nautical miles so 10 statute miles = 10 X 0.8695652 = 8.695652 nautical miles. A nautical mile is determined by 1 minute of latitude. Therefore 1 degree of latitude equals 60 nautical miles or 69 statute miles since there are 60 minutes in 1 degree. Check out the link below for a handy conversion webpage. They have 0.86897624 as the conversion number but it really depends on how many decimals your calculator can handle. The fewer the decimal places the greater the rounding error.
If 1 nautical mile = 1.15 statute mile then 1 statute mile = 0.8695652 nautical miles so 10 statute miles = 10 X 0.8695652 = 8.695652 nautical miles. A nautical mile is determined by 1 minute of latitude. Therefore 1 degree of latitude equals 60 nautical miles or 69 statute miles since there are 60 minutes in 1 degree. Check out the link below for a handy conversion webpage. They have 0.86897624 as the conversion number but it really depends on how many decimals your calculator can handle. The fewer the decimal places the greater the rounding error.
Backwards again
If 1 statute mile = 0.8695 Nautical miles then 10 statutue X 0.8695 = 8.685 Nautical 10 nautical miles / 0.8695 = 11.5 statute miles Just remember that since a nautical mile is longer you will always have less nautical than statute.
If 1 statute mile = 0.8695 Nautical miles then 10 statutue X 0.8695 = 8.685 Nautical 10 nautical miles / 0.8695 = 11.5 statute miles Just remember that since a nautical mile is longer you will always have less nautical than statute.
Also...
I know it wasn't mentioned or brought up as a question, but I hear people incorrectly say, "Knots per hour". A Knot is a unit of speed. One Knot is one nautical mile per hour. Therefore, it is correct to say "5 Knots", but it's redundant to say "5 Knots per hour." ~ Happy sails to you ~ _/) ~
I know it wasn't mentioned or brought up as a question, but I hear people incorrectly say, "Knots per hour". A Knot is a unit of speed. One Knot is one nautical mile per hour. Therefore, it is correct to say "5 Knots", but it's redundant to say "5 Knots per hour." ~ Happy sails to you ~ _/) ~
Dick,Dream Chaser and I all agreed
and Steve's link confirmed that we were correct. Dream Chasers "No" threw me off and I didn't look closely at his /her math. Sorry if I added to the confusion. remember multiplying by 1.15 is the same as dividing by 0.86956....
and Steve's link confirmed that we were correct. Dream Chasers "No" threw me off and I didn't look closely at his /her math. Sorry if I added to the confusion. remember multiplying by 1.15 is the same as dividing by 0.86956....
Decimal Places
It appears that a part of the argument is about how many decimal places is appropriate. Frequently when people work on a problem, the data is only accurate to two places. They then divide one piece of data by the other using their $10 calculator. For example I have a board 7 feet 9 inches long which I need to cut into 7 equal places. The board must be cut into 1.107142857 foot lengths. Not only that, the saw kerf is 7/64 inches or .109375 inches. Never mind, I will just cut it into one foot lengths and throw away the rest. Back in the days of slide rules, I think people were more aware of this. As any idiot with a slide rule knows 2 X 2 = 3.99. Depends on the application. For all practicle purposes, in a sailboat, usually nautical miles and statute miles can be used interchangably.
It appears that a part of the argument is about how many decimal places is appropriate. Frequently when people work on a problem, the data is only accurate to two places. They then divide one piece of data by the other using their $10 calculator. For example I have a board 7 feet 9 inches long which I need to cut into 7 equal places. The board must be cut into 1.107142857 foot lengths. Not only that, the saw kerf is 7/64 inches or .109375 inches. Never mind, I will just cut it into one foot lengths and throw away the rest. Back in the days of slide rules, I think people were more aware of this. As any idiot with a slide rule knows 2 X 2 = 3.99. Depends on the application. For all practicle purposes, in a sailboat, usually nautical miles and statute miles can be used interchangably.
Dan that's a big maybe!!!!
A nautical mile is 15% larger than a statute mile. If you are just sailing around the lake or bay you are probably correct in that it doesn't matter. But if you are planning to sail 100 NM and want to arrive during daylight hours you might run into trouble. I mention this specifically because I plan to sail about 150 NM in the gulf soon. I would like to arrive at the jetty during daylight hours. If I devide that distance by statute miles it will take me 30 hours but really the distance is 172.5 SM and it would really take 34.5 hours at 5 SM/hr. That would mean missing the tide and/or arriving after dark. All that said I plan to arrive in the morning so that if the wind is not as expected we should still arrive during daylight. To keep it simple I do everything in Knots including my GPS. KISS. When it is possible for me to make an error I will!!! I agree that it is fuzzy math planning a trip on a sailboat but the more accurate calculations give a better starting point. As to rounding off numbers I usually wait until the last number. Then decide what is significant. Using your example it is ridiculous to round off at a 1/100 of an inch if you are cutting 2' firewood with a chainsaw. But if you are machining a new part for a diesel that would be incredibly sloppy.
A nautical mile is 15% larger than a statute mile. If you are just sailing around the lake or bay you are probably correct in that it doesn't matter. But if you are planning to sail 100 NM and want to arrive during daylight hours you might run into trouble. I mention this specifically because I plan to sail about 150 NM in the gulf soon. I would like to arrive at the jetty during daylight hours. If I devide that distance by statute miles it will take me 30 hours but really the distance is 172.5 SM and it would really take 34.5 hours at 5 SM/hr. That would mean missing the tide and/or arriving after dark. All that said I plan to arrive in the morning so that if the wind is not as expected we should still arrive during daylight. To keep it simple I do everything in Knots including my GPS. KISS. When it is possible for me to make an error I will!!! I agree that it is fuzzy math planning a trip on a sailboat but the more accurate calculations give a better starting point. As to rounding off numbers I usually wait until the last number. Then decide what is significant. Using your example it is ridiculous to round off at a 1/100 of an inch if you are cutting 2' firewood with a chainsaw. But if you are machining a new part for a diesel that would be incredibly sloppy.
Mental Conversions, FWIW.
When explaining the difference to novices and when doing rough calculations in my head, I use a 5/6 = nm/sm ratio. It has a significant margin of error, but works very well for many routine applications.
When explaining the difference to novices and when doing rough calculations in my head, I use a 5/6 = nm/sm ratio. It has a significant margin of error, but works very well for many routine applications.
I remember doing this stuff
Now I point to where I want to go on a electronic chart and the computer does the rest. Ain't life grand?
Now I point to where I want to go on a electronic chart and the computer does the rest. Ain't life grand?
Thinking is why I like Sailboats
It's part of the fun. If I just wanted to go someplace a boat would be low on the list. A sailboat probably wouldn't make the list. The little thought processes like planning when and where to tack. trimming sails reading charts etc. Add to my enjoyment. We use the GPS to confirm my dead reckoning. My wife keeps track of where we are using the chart and the GPS. I usually plan the trip in my head.
It's part of the fun. If I just wanted to go someplace a boat would be low on the list. A sailboat probably wouldn't make the list. The little thought processes like planning when and where to tack. trimming sails reading charts etc. Add to my enjoyment. We use the GPS to confirm my dead reckoning. My wife keeps track of where we are using the chart and the GPS. I usually plan the trip in my head.
Tom, there are so many reasons to do this sport
that Gary needs to post it as one of his topics. But then too, he probably has.
that Gary needs to post it as one of his topics. But then too, he probably has.
Bit of a Stretch Tom
Lets keep it simple (KISS). You need to sail 150 something. You are intending to sail at 5k. You don't actually think you are going to sail at 5k do you? You would be better off to estimate that you are averaging between 4 to 6k and that accuracy is probably optimistic when you consider the accuracy of the wind forecast. At 4 to 6 knots will take you 37.5 hours to 25 hours to sail 150nm. Now if it is actually 150 statute miles it will take you 32.5 to 22 hours. In both cases it is questionable whether you will make it in 30 hours. Another way to look at it is that for a 5k cruise, the variation between knots and sm/hour is only a half knot. My point was then and still is that the other accuracies make it the difference between nautical miles and statute miles insignificant. And to argue about it out to six decimal points is ludicrous. I like to think also. When driving I mentally try to calculate how long it will take me to get to the next town and I try to estimate how fast the other cars are going by timing how long it takes them to increase or decrease the distance between me and them by 100 yards. I also mentally shift between knots and statute miles per hour by using a factor of 1.1, but it really makes very little difference. Its all lost in the noise.
Lets keep it simple (KISS). You need to sail 150 something. You are intending to sail at 5k. You don't actually think you are going to sail at 5k do you? You would be better off to estimate that you are averaging between 4 to 6k and that accuracy is probably optimistic when you consider the accuracy of the wind forecast. At 4 to 6 knots will take you 37.5 hours to 25 hours to sail 150nm. Now if it is actually 150 statute miles it will take you 32.5 to 22 hours. In both cases it is questionable whether you will make it in 30 hours. Another way to look at it is that for a 5k cruise, the variation between knots and sm/hour is only a half knot. My point was then and still is that the other accuracies make it the difference between nautical miles and statute miles insignificant. And to argue about it out to six decimal points is ludicrous. I like to think also. When driving I mentally try to calculate how long it will take me to get to the next town and I try to estimate how fast the other cars are going by timing how long it takes them to increase or decrease the distance between me and them by 100 yards. I also mentally shift between knots and statute miles per hour by using a factor of 1.1, but it really makes very little difference. Its all lost in the noise.
I am Ashamed
I just realized I made a terrible error when I said that there is only about an error of a half knot when cruising at 5k. The error is actually 5 minus 5/1.1507757576 or .6550366208. I was in error by .155036208k. Since I sail about 1000 miles per year, I am no longer sure where my boat is at. It is probably about 31.0072416 nm miles away from where I thought I left it.
I just realized I made a terrible error when I said that there is only about an error of a half knot when cruising at 5k. The error is actually 5 minus 5/1.1507757576 or .6550366208. I was in error by .155036208k. Since I sail about 1000 miles per year, I am no longer sure where my boat is at. It is probably about 31.0072416 nm miles away from where I thought I left it.
Tides and Deadlines
We keep imposing these artificial deadlines on ourselves. For example, we have to get there by 4:15PM because of the tide. There are a several things wrong with this deadline. You might consider leaving a few hours or even a day earlier. Then there is the accuracy of the tide forecast. Tide forecasts, unless you get a tailored forecast, such as in a local newspaper, do not take into account local tide conditions. For example the tide tables say high tide will occur at 4:15PM. However, if there is any kind of restriction in the movement of the water such as shallows or another restriction, which slows down the flow in or out of a pool, the high tide may be delayed by several hours. The other thing wrong with this type of deadline is that the tide does not suddenly stop flowing in at 3k at 4:15PM and then suddenly start flowing out at 3k. The tide gradually stops flowing in and then gradually starts flowing out. The tide will probably be less than a knot for several hours. How many knots can you tolerate, and where is that in the tide tables? When traveling to Panama City, Florida we sometimes take a small catamaran, which we keep in a bayou. There is a restriction in the flow in and out of that bayou. The tide runs very rapidly through that restriction. The local newspaper have tailored tide forecasts for a half dozen locations in the Panama City area. The times vary from each other by several hours. In spite of that, none of the forecasts adequately describe the flow through that restriction.
We keep imposing these artificial deadlines on ourselves. For example, we have to get there by 4:15PM because of the tide. There are a several things wrong with this deadline. You might consider leaving a few hours or even a day earlier. Then there is the accuracy of the tide forecast. Tide forecasts, unless you get a tailored forecast, such as in a local newspaper, do not take into account local tide conditions. For example the tide tables say high tide will occur at 4:15PM. However, if there is any kind of restriction in the movement of the water such as shallows or another restriction, which slows down the flow in or out of a pool, the high tide may be delayed by several hours. The other thing wrong with this type of deadline is that the tide does not suddenly stop flowing in at 3k at 4:15PM and then suddenly start flowing out at 3k. The tide gradually stops flowing in and then gradually starts flowing out. The tide will probably be less than a knot for several hours. How many knots can you tolerate, and where is that in the tide tables? When traveling to Panama City, Florida we sometimes take a small catamaran, which we keep in a bayou. There is a restriction in the flow in and out of that bayou. The tide runs very rapidly through that restriction. The local newspaper have tailored tide forecasts for a half dozen locations in the Panama City area. The times vary from each other by several hours. In spite of that, none of the forecasts adequately describe the flow through that restriction.
Dan I generally agree with you
But not totally. I am doing as you have said in calculating a range of speeds using your example of 4-6 knots. Then that gives me about a 12 hour range so that if I plan to arrive off of Panama City early in the morning I should arrive sometime that day. Being able to time your arrival is a valuable ability. Running into a stange inlet at night and finding an anchorage in the dark is something I don't want to do. Arriving early an hour or two before dawn is no big deal but arriving a little after dark and having to hang off shore for 8-10 hours(in summer) is to be avoided. Fuzzy numbers build up the error in a calculation. After a while it becomes a meaningless number. I might worry about it more than some because I am a pilot. I know when I take off that I have enough fuel to travel a certain distance. That's through calm air!!! The fudge factors add up in flying. But in a plane you will start going down as soon as the fuel is used up!!! So using the best information available on wind speed, direction, distances fuel consumption I take off with a reasonable expectation of arriving at the next airport at a certain time. It doesn't always work out as planned. One time I had a 60 knot tailwind!!! A couple of times I ran into an unexpected headwind and had to divert to another airport to refuel. But most of the time I used about the amount of fuel and it took about the amount of time that I had planned.
But not totally. I am doing as you have said in calculating a range of speeds using your example of 4-6 knots. Then that gives me about a 12 hour range so that if I plan to arrive off of Panama City early in the morning I should arrive sometime that day. Being able to time your arrival is a valuable ability. Running into a stange inlet at night and finding an anchorage in the dark is something I don't want to do. Arriving early an hour or two before dawn is no big deal but arriving a little after dark and having to hang off shore for 8-10 hours(in summer) is to be avoided. Fuzzy numbers build up the error in a calculation. After a while it becomes a meaningless number. I might worry about it more than some because I am a pilot. I know when I take off that I have enough fuel to travel a certain distance. That's through calm air!!! The fudge factors add up in flying. But in a plane you will start going down as soon as the fuel is used up!!! So using the best information available on wind speed, direction, distances fuel consumption I take off with a reasonable expectation of arriving at the next airport at a certain time. It doesn't always work out as planned. One time I had a 60 knot tailwind!!! A couple of times I ran into an unexpected headwind and had to divert to another airport to refuel. But most of the time I used about the amount of fuel and it took about the amount of time that I had planned.
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