Safe distance offshore?

[skatastrophy]

Originally Posted by Tropic Cat

Lightning killed everything attached to the 12v DC wiring. by everything...I mean everything from starters and bilge pumps, to florecent lights...Everything. Also, Everything mounted to the top of the mast was either blown off or disintergrated.

Battery powered cell phones and hand held GPS on the Salon table were unaffected and still work fine to this day.

The hit was to the top of the mast, the charge came down the mast wires and found a path into the hulls and down the drivetrain. Soaking wet and in bare feet, I felt nothing at all at the Helm. Not even a tingle. Sails were down and I was heading into the storm cell, so wind and horizontal rain were in my face in 50 knots of wind. My head was down when the lightning hit. When the 'bang' came, I looked up just in time to see my mast head tricolor splash off the starboard quarter. A second later plastic began raining down on me as pieces of the Windex and steaming light were blown backward into the cockpit.

The hulls were undamaged, and electrics / electronics were the only casualty. The boat has no lightning protection of any kind.

Didn't you feel it coming?

I was within 20 meters of a lightning strike once. I was gathering wood for a camp fire and I felt a weird sensation... like you feel when someone's watching you... like the hairs on the back of my neck type feeling. I looked up and a tree got hit about halfway up. I couldn't see a whole lot afterwards because it was dusk and the flash was so bright, but man... the feeling of lightning coming (within the next 1-2 seconds) is one I'll never forget!

[Tropic Cat]

Originally Posted by skatastrophy

Didn't you feel it coming?

No.. I saw the storm closing on us, dropped sails and started both engines. When it hit us, in 50 knots of wind, I was too busy keeping the boat into the wind. Conditions were what I'd call exciting. The wind driven rain was brutal and the noise level very high.

[GordMay]

See also:
Estimating the distance of an object using a “Rule of Thumb”
Did you know that your arm is about ten times longer than the distance between your eyes?
That fact, together with the use of similar triangles, can be used to estimate thedistance between you and any object of an approximately known size.
Goto:
http://www.atlantictallships.ca/PDF/...stionsheet.pdf

[Pblais]

One exception would be the Diamond Shoals off Cape Hatteras. You would probably do well to be very far off those since they do extend 20 miles from shore and have been sinking ships for about 400 years. The proximity to the Gulf stream combines to make it a place you just don't want to be caught in in foul weather.

[RickD]

The hit was to the top of the mast, the charge came down the mast wires and found a path into the hulls and down the drivetrain. Soaking wet and in bare feet, I felt nothing at all at the Helm. Not even a tingle.

WOW! Amazing story. I've taken two near strikes. Once as a kid, crossing a field, lightning hit about 20 yards from me and threw me to the ground, knocking the wind out of me. I felt the concussion more than anything.

A few years ago, I was standing in my garage when a sudden Colorado severe thunderstorm perked up. I'm part of the local Skywarn net so I had a handheld radio and had joined in the weather net to give hail information.

A lightning strike came down directly in front of me in the street, made a 90 degree left turn and went horizontally up the street.

I was standing two feet from the garage door roller system (large piece of metal, stuck in the concrete holding the rollers for the door). An arc jumped from that metal bar to my left arm knocking me right on my rump. It stunned me, and I CERTAINLY felt it. My buddy who was standing right next to me caught me and kept me from hitting my head and said "WOW! You got hit!" then laughed.... ouch! lol

(Note: Those two incidents were at least 30plus years apart so I figure I have another 18-20 more before another such incident! )

Originally Posted by GordMay

A safe rule of thumb is to stay “off soundings”, that is, in water of 100 fathoms (600 Ft) or deeper.

Rules of Thumb can be very handy, but this one strikes me as completely useless. Here on the West Coast of North America your stern can be in 100 fathoms and almost have your bow on the beach, where on the East Coast especially the Northeast Coast, that might put you 15 miles offshore. Excuse my poetic liscense, but I'm sure you know what I mean.

The "Thumb's Width" rule certainly didn't work for me on my local charts, it had me right on the beach for passages between San Francisco and Monterey.

I know that Gord would agree that nobody should follow such things blindly.

Either of these rules might work some places, but it is far more important to know WHY these rules might makes sense and then apply it to YOUR local situation.

If you are transiting a well traveled coast (like the east coast of the USA!)there will be many local cruising guides which will give you very detailed local knowledge and passage info that will have all kinds options depending on weather, time of year etc. You can download your local Coast Pilot for FREE.

Yes, you'll have to read and digest information, but short easy discussion board answers are not the answer.

[GordMay]

Originally Posted by GreatKetch

Rules of Thumb can be very handy, but ...
... The "Thumb's Width" rule certainly didn't work for me on my local charts, it had me right on the beach for passages between San Francisco and Monterey.
I know that Gord would agree that nobody should follow such things blindly.
Either of these rules might work some places, but it is far more important to know WHY these rules might makes sense and then apply it to YOUR local situation...

A Rule of Thumb represents an often useful rough approximation, but is not intended to be strictly accurate or reliable in every situation.
Understanding the variables affecting the values is essential in it’s application to specific situations.
A thumb rule can give an approximation which is probably sufficient in the larger part of the practical cases.

Scale is the relationship between distance on the chart and actual distance on the earth. "Natural Scale" means the relationship between the size (distance) of the chart and the earth. For example, 1:15,000 means that one unit on the chart equals 15,000 units on the earth.

As a rule of thumb, the upper joint of your thumb is about one inch long (base of nail to joint), or wide. This is the often-cited origin of the term.

There are about (12 x 6080) 73,000 inches (actually 72,960") in a nautical mile; so on a 1:100,000 Coastal Chart, your 1" thumb will represent about 1-1/3 to 1-1/2 nautical miles (actually 1.37149 nm); which is likely to be adequate separation from charted hazards.

Harbour Charts: are large scale, 1:5,000 - 1:15,000 and are used for navigation in harbours or intricate, hazardous, shoal-infested waters.

Approach Charts: 1:15,001 - 1:50,000, are used for approaching coasts where a lot of detail is required.
On an Approach chart, at 1:25,000 scale, a thumb width with will represent about > 0.33 nm. (0.3428725505699296)

Coastal Charts: 1:50 001 - 1:150 000, are used to show continuous extensive coverage with sufficient inshore detail to make landfall sightings easy.
On a Coastal chart, at 1:100,000 scale, a thumb width will represent about <1.5 nm, or > 1.33 nm.
(1.3714902022797184)

General Charts: 1:150 001 - 1:500 000, give extensive offshore coverage with sufficient inshore detail to make landfall sightings easy. Fisheries charts use these scales.
On a General chart, at 1:250,000 scale, a thumb with (± 1") will represent about < 3.5 nm, or > 3.33 nm. (3.4287255056992962)

Sailing Charts: are small scale, 1:500 001 and smaller, are used for offshore navigation beyond sight of land.
On a sailing chart, at 1:600,000 scale, a thumb with (± 1") will represent about < 8.25 nm, or > 8 nm. (8.228941213678311)

[Easterly-30]

When traveling South on the East Coast, is there an ideal distance from the edge of the Gulf Stream where you can get the maximum benefit of the South flowing eddies?

The edge of the Gulf Stream flows various distances from shore along the coast. At Cape Canaveral it runs around 25 to 30 miles from shore. It gets closer to the shore as you get further south. At Miami it is very close, less than five miles I believe.

So, if there is an ideal distance from the Stream that would affect your decision as to how far from shore to travel when going South.

Also, if you are going North you would want to travel in the Stream wouldn't you?

As for the Gulf Stream affecting the weather, Wikipedia says that it does: "The warm water and temperature contrast along the edge of the Gulf Stream often increases the intensity of cyclones, tropical or otherwise. Tropical cyclone generation normally requires water temperatures in excess of 26.5 °C (79.7 °F).[12] Tropical cyclone formation is common over the Gulf Stream, especially in the month of July. Storms travel westward through the Caribbean and then, either move in a northerly direction and curve towards the eastern coast of the United States, or stay on a north-westward track and enter the Gulf of Mexico.[13] Such storms have the potential to create strong winds and extensive damage to the United States' Southeast Coastal Areas. Strong extratropical cyclones have been shown to deepen significantly along a shallow frontal zone, forced by the Gulf Stream itself during the cold season.[14] Subtropical cyclones also tend to generate near the Gulf Stream. 75 percent of such systems documented between 1951 and 2000, formed near this warm water current, with two annual peaks of activity occuring during the months of May and October.[15] Cyclones within the ocean form under the Gulf Stream, extending as deep as 3,500 metres (11,000 ft) beneath the ocean's surface.[16]"

[imagine2frolic]

Going north? Definatley you want to be in the Gulf Stream. Everybody wants an extra 3+ knots of speed.

An easterly wind can push the stream to the beach. When we were less than a half mile off the beach. Less than a quarter mile farther east we would lose 2 knots. That is how close I have experienced the stream to the beach.

What's your plans Jim? Sounds like you are collecting data?

[Zach]

If the wind is blowing a small craft advisory, you will want to go around the shoals off Cape Lookout. The charted slew bouys are not out there any more, for those wanting to slither through the shoals to the bight.

600 foot depths off the coast of NC put you at the continental shelf. This can mean the edge of the gulf stream depending which way the wind is blowing.

If you are curious about where the stream is currently, you can get an idea by looking here.
Sea Surface Temperature - IMCS Marine Remote Sensing

</title> <meta name="description" content=""> <meta name="keywords" content=""> <meta name="author" content="Frank Monaldo"> <meta name="generator" content="AceHTML 5 Pro"> <title> Ocean Remote Sensing Group - JHU/APL


DEOS: Current velocities of the Gulf Stream

[Easterly-30]

IMAGINE, I want to go explore the Keys! Especially, the West Coast side. It won't be anytime soon though.

ZACH, Most people duck inside onto the ICW rather than go around Cape Hattaras don't they? I assume that you would have to go way, way out to stay out of trouble at Cape Hattaras. I'm not sure how far out would be safe, but you'll definitely have to tangle with the Gulf Stream near there.