Rule Of Thumb Formulas...

[daddle]

Originally Posted by roger.waite

So five degrees (or so) is another hour at sea!

Well maybe, if the navigator is completely asleep, but 5 degrees off-course only lengthens a 60nm trip by 0.3nm so long as the 5 degree error is corrected somewhere during the middle of the voyage. And only a little more if not corrected until near the end.

And way off topic...heading 5 degrees off is often way faster until you hit the reef...

Pretty embarrassing to make a 95degree heading change after 60 miles...

Okay, I'm a trig wonk..

[joshea]

Hey Jedi
Thanks for the wise guy remark but anyone who is following this post would think that we are talking daily amps. So learn how to multiply and maybe your total would fit the formula.

Jim
s\v Kismet

[hummingway]

Originally Posted by daddle

Pretty embarrassing to make a 95degree heading change after 60 miles...

A sailor just smiles and says "sweet tack huh?"

[Jim Cate]

Back to the important subject of estimating time required for boat projects:

Make best possible, conservative estimate of how long it SHOULD take to get it done.
Then multiply that number by two. Then move up one unit.

IE, if your best guess is two hours, double the two to get four, and move from hours to days... THAT is how long it will really take!

Cheers,

Jim and Ann s/v Insatiabe II lying Church Point NSW Oz

[chala]

Originally Posted by Jim Cate

Back to the important subject of estimating time required for boat projects:

Make best possible, conservative estimate of how long it SHOULD take to get it done.
Then multiply that number by two. Then move up one unit.

IE, if your best guess is two hours, double the two to get four, and move from hours to days... THAT is how long it will really take!

Cheers,

Jim and Ann s/v Insatiabe II lying Church Point NSW Oz

So lets apply it to building a boat. 4 years equal 8 years plus ? (what is the next unit after years, infinity?)

[GordMay]

Originally Posted by chala

... what is the next unit after years, infinity?

Decades?

[chala]

Originally Posted by GordMay

According to Bowditch,

And according to Wikipedia
Horizon - Wikipedia, the free encyclopedia

[roger.waite]

Originally Posted by daddle

Well maybe, if the navigator is completely asleep, ... so long as the 5 degree error is corrected somewhere during the middle of the voyage. And only a little more if not corrected until near the end.

Amazing.

We are all so used to GPS & radar fixes now that we assume all errors get corrected mid-ocean! Of course, there is that yacht that left Australia for New Caledonia, and set the waypoint 1 degree south. Wondered why there was a whole lot of ocean at their destination! Still, better than grinding down the reef if the waypoint had been a degree too far north.

[Michael D]

I've been told that build, buy and make ready or buy used and refit/upgrade it's a ten year project more often than not. 1997 to 2010 I've managed to do it twice. But the individual job time estimate is spot on!

From my exalted position on the bridge of freighters or tankers we can see roughly 12 miles to a hull up target much further on a 'good' day to see the mast and house of another commercial ship. Occasionally the othr ship or boat rises a a mirage, changing color, appearing and disappearing, even upside down.

Most, the vast majority of the time what we see is the apparent horizon. The real one is rarely seen. And when the sun goes down what you see as the sun setting is always a mirage the real sunset has already occured.

The enjoyment is chasing green flash and it's more elusive cousins (mulitples, blue or violet and those in the morning and other such atmospheric phenomena. Moon Bow for example.

As for the five degree error there are several good books the best of which is Emergency Navigation by Dave Burch on the subject. Relying on only one method of navigation be it GPS or sextant is the Being able to navigate without either of those two instruments is the stuff of good sailors.

I'm off to 7 degrees south roughly 76 degrees East home of the 777 band which plays at a local seaman's club. Where? You've got 65 or so days to figure it out. And thanks for all the good posts.

Cheers

Michael D

[barnakiel]

Rule of thumb:

If it is blowing hard from one direction and then suddenly stops, the next blow will come from the opposite direction and will be hard too.

b.

[Chief Engineer]

The tool that "you just had a second ago".....you are usually sitting on

[missnmountains]

Just to clarify the distance to horizon equation. The distance to horizon is the sum of (the square root of the height of "you" times 1.17) plus (the square root of the height of the object you see or the shore times 1.17)

Previous post suggest the you only calculate your height. You must also utilize the height of the object you are seeing.

Ken

[daddle]

Originally Posted by missnmountains

Just to clarify the distance to horizon equation. The distance to horizon is the sum of (the square root of the height of "you" times 1.17) plus (the square root of the height of the object you see or the shore times 1.17)

Previous post suggest the you only calculate your height. You must also utilize the height of the object you are seeing.

Ken

Yes and no. One is the HORIZON the other is another OBJECT.

[Chief Engineer]

We are talking horizon....vessels that are "hull down" are another thing.

[s/v Jedi]

Originally Posted by joshea

Hey Jedi
Thanks for the wise guy remark but anyone who is following this post would think that we are talking daily amps. So learn how to multiply and maybe your total would fit the formula.

Jim,

I later found that what was meant is daily energy output in Ah. I can assure you that I wasn't trying to be "the wise guy" and thought that we were talking about Amps output like it was written. You might well be right that non-technical people would think Ah when reading that but why not write that then? I don't know the term "daily amps" but figured out what you mean with it, which is energy output per day instead of power output. Everyone technical and every manufacturer calls that Ah or better kWh; a unit that includes time.

Sorry for not thinking like you...

cheers,
Nick.