Knots vs. MPH

pcator · Posted: Sat Jul 07, 2007 5:22 pm Post subject: Knots vs. MPH

Has there ever been a poll about how many of us use Knots vs. MPH on the chart plotter? If not could we have one? Just curious.

starcrafttom · Posted: Sat Jul 07, 2007 6:34 pm Post subject:

I use mph ,not only because it drives my father crazy, but because I have used it all my life and cant think in knots. I would have to convert from one to another every time. It really does not matter as long as you know what your talking about.

Alasgun · Guest

I use both, the Simrad shows them both along with water temp etc. on the top of the display. Of coarse, I'm not bright enough to"think" in either so it's probably good they both show. Wink

Mike

Susan E · Posted: Sat Jul 07, 2007 6:55 pm Post subject:

MPH, but when the orca whale boat told me what speed i was allowed to go they listed it in knots . so i had to aks someone what that would be in <MPH.

susan

William and Beth Tucker · Posted: Sat Jul 07, 2007 7:04 pm Post subject:

We use mph.I have knots in my ropes and knots in my stomach.I'am too old to change...I'am glad i was potty trained when i was young..Keep your life jacket on ! tucker.]

thataway · Posted: Sat Jul 07, 2007 7:14 pm Post subject:

The ICW's are marked in Statuate miles, so we use Statuate miles when on the ICW's. If we are gping in more open areas we will usually use knots, because it is sligtly easier to plot on a chart (one nautical mile equals one minute of lattitude). Take your dividers from the distance you want to go, and transfer this to the lattitude on the side of the cart to give nautical miles.

Sea Angel · Posted: Sat Jul 07, 2007 7:23 pm Post subject:

Converted from KTS to MPH for daily use.

The ICW measures the distances in statute miles, as do the local cities on their navaids for speed & distance. So, MPH is primary tools locally.

I prefer the KTS for the simplicity of my simple mind from the tears & years of flying as ASW aircrew and working/servicing flight simulators.

JamesTXSD · Posted: Sat Jul 07, 2007 10:17 pm Post subject:

Knots for us, except when on the ICW or inland waters. But lately, I've been keeping one chartplotter on knots and the other on statute. Belt and suspenders. Wink

Best wishes,
Jim B.

C-Hawk · Posted: Sat Jul 07, 2007 11:45 pm Post subject:

Knots here, most charts in our area are in knots. Easy enough to convert
1 knot = 1.16 MPH (I think)
5 Knots = 5.8 MPH
10 Knots = 11.5 MPH
15 Knots = 17.3 MPH
20 Knots = 23.0 MPH
25 Knots = 28.8 MPH
30 Knots = 34.6 MPH
35 Knots = 40.3 MPH
40 Knots = 46.1 MPH

Doryman · Posted: Sun Jul 08, 2007 1:05 am Post subject:

Looks like 110% of mph gets you in the ballpark for knots.

How many of you have to perform mental gymnastics to remember to check if a chart is marked in fathoms or feet, and to do the conversions?

Warren

DaveS · Posted: Sun Jul 08, 2007 1:09 am Post subject:

In my past I was told that I had a "knotty streak" Embarrased

....in me.....so I'll just continue to be "knotty"... Wink

jlastofka · Posted: Sun Jul 08, 2007 7:21 am Post subject: Knots to MPH

Hi,

Warren, using 110% as a conversion is easy to do in your head, that's true. Your statement was backwards, though. It's 110% of Knots that gives you approximate MPH. (The real number is almost exactly 115%).

100 Knots would be 115 MPH, but for most speeds, like 12 knots, for instance, it's easier to mentally calculate 1.2 as 10% of 12 and then add them to get 13.2 MPH. The true result is 13.8, by the way.

I've been doing mostly ocean sailing for the past couple years, so I just use knots. I suppose when I start trailering the C-Dory to lakes and rivers, I might use MPH there. I guess it depends on whichever charts or maps or guidebooks I might be using.

By the way, does everyone know (probably not) that you can go to the Google search window and type in something like

100 knots in mph

and it will respond with the answer 115.078

You can also type in 27.32 dollars in pounds and get 12.59 British Pounds

(that one will vary with the exchange rate....)

Or 12 fathoms in feet and get 72 feet.

And on and on and on. It's an excellent unit converter and calculator and will do a lot more than I'm showing here.

Jeff Lastofka

Doryman · Posted: Sun Jul 08, 2007 8:46 am Post subject:

Jeff, thanks for catching my bass ackwards math.

I hope I never run aground because I mistook a foot depth for a fathom depth. Probably not much of an issue with C-Dories and with electronic depthsounders always reading out in feet, but it's still in the back of my mind.

Where would one encounter mission-critical measurements in knots?

Warren

El and Bill · Posted: Sun Jul 08, 2007 9:17 am Post subject:

We have used knots, since our "knotty" (thanks, Dave S.) days of childhood and never been a problem. No wake speed signs are sometimes knots, sometimes mph -- no sweatski -- at those low speeds a few decimal points has never been critical for us. Come to think of it, those decimal points seem most critical when attached to $$.

timflan · Posted: Sun Jul 08, 2007 11:09 am Post subject:

I use knots because knots and nautical miles are the appropriate units to use aboard a boat (or in an airplane, for the same reasons). It's one unit that trumps both metric and so-called "Imperial" units.

Why? Because all navigation is done in nautical miles, and all wind velocities are reported in nautical miles per hour. Why is this? Because one minute of latitude (at sea level, average at the equator) is exactly one nautical mile, so one degree of latitude is 60 nautical miles. Every chart has a scale built along both sides...the latitude markers! Don't try to use the longitude lines the same way, it won't work.

Also, just curious, why do you need to convert? If you're working with nautical miles, you're working with nautical miles. I never convert, because...why bother? I don't understand why I need to know how many kilometers or statute miles are involved? It's navigation.

On to the next question: magnetic or true? Smile