what are you talking about?

Nov 8, 2007
1,590
Hunter 27_75-84 Sandusky Harbor Marina, Ohio
Nautical Mile/statute mile = 6,000 feet/5280 feet = 1.136 = knots/mph.

We use nautical miles because:

60 nautical miles = 1 degree of latitude = 1 degree of longitude at the equator, or

1 nautical mile = 1 minute of latitude.

That is, a nautical mile fits easily into the navigation system of latitude (and longitude, but a degree of longitude approaches zero as you get closer to the North Pole.)

I can do bullards, but that’s enough for tonight.
 
Mar 29, 2011
169
Beneteau 361 Charlotte,Vt
How about - when you see a boats displacement. Is that in saltwater or fresh water? Wouldn't a boat displace more water in fresh water then saltwater?
 
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May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
a great lakes sailor just described ocean miles properly. david, your the man :)

" if you can sail the great lakes, you can sail anywhere"
 
Oct 19, 2017
7,976
O'Day Mariner 19 Littleton, NH
How about - when you see a boats displacement. Is that in saltwater or fresh water? Wouldn't a boat displace more water in fresh water then saltwater?
Not if you measure in weight, only in volume or, if you sank your boat, then it displaces more in saltwater, but only in weight.:confused:

- Will (Dragonfly)
 
Nov 8, 2007
1,590
Hunter 27_75-84 Sandusky Harbor Marina, Ohio
“Seawater weighs about 64 pounds per cubic foot—on average. "Average" fresh water weighs about 62.2 pounds per cubic foot.“ So, yes, the same boat displaces a higher volume (but same weight) of fresh water than salt water.
 
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May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
so now google is saying that a nautical mile is 6076. 1 ft. that's new to me. i always used 1.1359 for the conversion so i looked like i knew what i was talking about.. now they saying 1.1508 to 1.

what's correct? and why
 

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,770
Hunter 430 Waveland, MS
1 nautical mile = 1 minute of latitude.
:worship:
Is the winner.
But...
He doesn't win the "Demaflichy" because SBO just ran out of inventory on those!:p

60 nautical miles = 1 degree of latitude = 1 degree of longitude at the equator
60 nautical miles = 1 degree of latitude is a Constant.
Also ≈63 nm for longitudes in most of USA

You can estimate distances between two Lat/Lon points by remembering 60 nm.:thumbup:
Jim...
 
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May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
hull speed? ALL blow boaters need to understand this dynamic. trawler types too. all 93,000 SBO people should understand this
 
May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
what's a flemish flake? saw one on a post here tonight. again, son taught me from boy scouts. kids, what can you do :)
 
May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
On what heel angle? What is the sea state? What is the water temperature? Are you in 20 knot winds off the beam?:hook2:
Jim...
well, none of that applies to explain the dynamics of hull speed. now, on my old CCA vessel the hull speed can change because of the shape of that old alden hull. BUT, the explanation of the the 'hull speed' dynamic is the same :)
 
May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
the hull speed formula is approximately the square root of the the water line times 1.32. but we all need to understand the dynamics of hull speed.
 
May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
stu, i need all the help i can get with grammer. mom's gone now and there is no one to help me
 

dLj

.
Mar 23, 2017
4,409
Belliure 41 Back in the Chesapeake
]You burn more fuel, you make more noise, you do not go much faster.
TRUE :) but why?[/QUOTE]

I haven't seen an answer to this... Wish I had a pencil, it's a lot easier to draw than explain in words, but here goes. In a displacement hull as you go faster, you start to form a sine wave shaped form of the water under your boat. The top of the sine wave is up near the bow, and the low part of the sine wave is towards the stern. As you approach and exceed your hull speed, the shape of that sine wave increases in amplitude, or the height of the front part gets higher and the low part gets lower. So you boat basically starts going up hill more and more. The stern drops down, the bow goes up, and all you do is burn more fuel, make more noise...etc...

dj
 
Aug 22, 2017
1,609
Hunter 26.5 West Palm Beach
so now google is saying that a nautical mile is 6076. 1 ft. that's new to me. i always used 1.1359 for the conversion so i looked like i knew what i was talking about.. now they saying 1.1508 to 1.

what's correct? and why
is that an international nautical mile? or a us nautical mile? Or an imperial nautical mile?
 
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May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
dj, your in the neighborhood, sorta, close, well, ....... no! ..... and the explanation needs to also explain how and why you can then calculate any hulls speed