Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 08-08-2009, 00:37   #1
Registered User
 
Down2TheC's Avatar

Join Date: Aug 2009
Location: Lake MI
Boat: Tartan 37
Posts: 83
USNA Short Course: Chapter Three - 6 Mile Rule

This is the simplest of them all and very handy for not looking to the GPS every 5 minutes.

6 minutes is 1/10th of and hour. So in 6 minutes your travel 1/10th of your speed in distance. Not handy at all unless you convert to yds. (again, we're using 2000yds - 1 NM.)

Doing 5 kts, so it 6 minutes we'll travel 1000 yds. (5 x 2000 = 10000 / 10 = 1000.)
So to skip the math, here's the rule.

Six Minute Rule: Speed in kts * 2, then add two zeros (shift the decimal two places) and you have the yards you'll travel.
8kts will be 1600 yds in 6 min.
3 kts will be 600 yds.
4.6 kts will be 460 yds.

Even easier is if you need to keep it in miles you're just moving the decimal.
6 kts will be .6NM in 6 min

Three minute rule is the same but don't double the number. Just shift the decimal 2 places.
5kts = 500yds in 3 min.
4.5kts = 450 yds in 3 min.

Example: You're 3.2 miles from your harbor, you're doing 5 kts. Your wife wants to know "are we there yet". What's your reply?

3.2 miles at .5 NM each 6 minutes. 3.2/.5 is about 6 and a little bit (remember we're doing quick brain calculations here) 6*6 = 36 min.... say about 38 min.

or

3.2 miles = 6400 yds. 5kts means 1000 yds in 6 min, 500 yds in 3 min. So 6 six mins, and a little less than 1 three min. So just under 39 min.
__________________

__________________
... and all I ask is a tall ship and a star to steer her by...
Down2TheC is offline   Reply With Quote
Old 08-08-2009, 03:58   #2
CF Adviser
 
Pelagic's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Boat: Van Helleman Schooner 65ft StarGazer
Posts: 6,887
Quote:
Originally Posted by Down2TheC View Post
Example: You're 3.2 miles from your harbor, you're doing 5 kts. Your wife wants to know "are we there yet". What's your reply?

My reply is quite simple....no math needed...."Yes!"
__________________

__________________
Pelagic is offline   Reply With Quote
Old 08-08-2009, 11:47   #3
Senior Cruiser
 
SkiprJohn's Avatar

Cruisers Forum Supporter

Join Date: May 2006
Location: Kea'au, Big Island, Hawaii
Boat: Cascade, Sloop, 42 - "Casual"
Posts: 14,192
Down to the Sea,
Thanks. I'll study that one for awhile and see if I can figure it out.
Regards,
JohnL
__________________
John
SkiprJohn is offline   Reply With Quote
Old 08-08-2009, 11:59   #4
CF Adviser
Moderator Emeritus
 
TaoJones's Avatar

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Montrose, Colorado
Posts: 9,850
Quote:
Originally Posted by Down2TheC View Post

Doing 5 kts, so it 6 minutes we'll travel 1000 yds. (5 x 2000 = 10000 / 10 = 1000.)
So to skip the math, here's the rule.

Six Minute Rule: Speed in kts * 2, then add two zeros (shift the decimal two places) and you have the yards you'll travel.
8kts will be 1600 yds in 6 min.
3 kts will be 600 yds.
4.6 kts will be 460 yds.
Little mistake in that last calculation, D2tC. You've increased your speed by more than 50%, from 3 kts. to 4.6 kts., but you give a distance traveled that's 140 yds. less (600 yds. down to 460 yds.)

The correct value, given your method of calculating this, would be 920 yds. (You skipped the x2 step.)

TaoJones
__________________
"Your vision becomes clear only when you look into your own heart. Who looks outside, dreams; who looks within, awakens."
Carl Gustav Jung (1875-1961)
TaoJones is offline   Reply With Quote
Old 08-08-2009, 12:40   #5
Registered User
 
Down2TheC's Avatar

Join Date: Aug 2009
Location: Lake MI
Boat: Tartan 37
Posts: 83
True, but I can no longer edit it to fix. Besides, any numbers like that it's easiest to stick to miles. 4.6kts - .46 miles in 6 min. Really no need to discuss yards in the 6 minute rule. Don't know why I started with yards (I wrote that 2 years ago and just pasted w/o reading)
__________________
... and all I ask is a tall ship and a star to steer her by...
Down2TheC is offline   Reply With Quote
Old 08-08-2009, 12:47   #6
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,150
All navigatiors should know the six minute rule. Its as basic as knowing latitude from longitude.

Another nice trick for doing mental math is to know that there are 2000 yards to a nautical mile. Not exactly, but close enough.

The same goes for 1 meter/second being closely equal to 2 knots.

I get asked by people how fast is a knot? 1.15 MPH. It's easy to remember. Calculate it the same way you mentally calculate a 15% tip in a restaurant.
__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 08-08-2009, 12:58   #7
CF Adviser
Moderator Emeritus
 
TaoJones's Avatar

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Montrose, Colorado
Posts: 9,850
Quote:
Originally Posted by David M View Post
I get asked by people how fast is a knot? 1.15 MPH. Easy to remember. Calculate it the say way you calculate a 15% tip in a restaurant.
Uh-oh . . . I calculate a 15% tip by doubling the sales tax and rounding up.

TaoJones
__________________
"Your vision becomes clear only when you look into your own heart. Who looks outside, dreams; who looks within, awakens."
Carl Gustav Jung (1875-1961)
TaoJones is offline   Reply With Quote
Old 08-08-2009, 12:59   #8
CF Adviser
Moderator Emeritus
 
Hud3's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: Virginia
Boat: Island Packet 380, now sold
Posts: 8,929
Images: 49
6 and 10 are two very handy numbers. If you change your course by 6 degrees, you'll be off the original course by one mile after traveling ten.
__________________
Hud
Hud3 is offline   Reply With Quote
Old 08-08-2009, 13:38   #9
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,150
Quote:
Originally Posted by TaoJones View Post
Uh-oh . . . I calculate a 15% tip by doubling the sales tax and rounding up.

TaoJones
You are a generous man Tao! The sales tax in a lot of counties, at least in my parts, are up close to 10% now.
__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 08-08-2009, 13:40   #10
Registered User
 
Down2TheC's Avatar

Join Date: Aug 2009
Location: Lake MI
Boat: Tartan 37
Posts: 83
I knew some of you salty dogs would know this stuff.
Hud, see Chapt 2: Radian rule. You're spot on.
__________________
... and all I ask is a tall ship and a star to steer her by...
Down2TheC is offline   Reply With Quote
Old 08-08-2009, 13:48   #11
CF Adviser
Moderator Emeritus
 
TaoJones's Avatar

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Montrose, Colorado
Posts: 9,850
Quote:
Originally Posted by David M View Post
You are a generous man Tao! The sales tax in a lot of counties, at least in my parts, are up close to 10% now.
Yeah, that's a good point David - OK, from now on I'll round down.

TaoJones
__________________
"Your vision becomes clear only when you look into your own heart. Who looks outside, dreams; who looks within, awakens."
Carl Gustav Jung (1875-1961)
TaoJones is offline   Reply With Quote
Old 08-08-2009, 19:38   #12
Senior Cruiser
 
SkiprJohn's Avatar

Cruisers Forum Supporter

Join Date: May 2006
Location: Kea'au, Big Island, Hawaii
Boat: Cascade, Sloop, 42 - "Casual"
Posts: 14,192
Ok Michael. Please revise your first post so that I might understand it with Tao's input.
Kind regards,
JohnL
__________________

__________________
John
SkiprJohn is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
USNA Short Course: Chapter Two - Radian Rule Down2TheC Seamanship & Boat Handling 4 24-10-2017 05:00
USNA Short Course: Chapter One Down2TheC Seamanship & Boat Handling 20 17-08-2009 13:23
Five Mile Wifi - EU or UK Dealer? multihullsailor6 Marine Electronics 5 01-06-2009 09:07
New chapter in our lives bayoubouy General Sailing Forum 3 18-04-2008 06:26
brand new and about to start the next chapter peter d christensen Meets & Greets 7 12-03-2007 04:14



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 00:37.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.