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Old 09-05-2011, 10:38 PM   #1
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When to start blowing your fog horn

When should one start blowing one's fog horn?* In my mind, it should be when the level of visibility is less than the range of one's fog horn.* So, big ships should start blowing when visibility drops to two miles, and the smallest vessels at one-half mile.* Leastwise, this is "according to Mark."* What do you all say?

<table style="width:400px;" border="1" cellspacing="0" cellpadding="0"><tbody><tr bgcolor="#2266a7"><td align="center" valign="middle"><strong class="white">Whistle Class[/b]</td><td align="center" valign="middle"><strong class="white">Length of Vessel in Meters[/b]</td><td align="center" valign="middle"><strong class="white">Limits of Fundamental Frequency[/b]</td><td align="center" valign="middle"><strong class="white">Minimum Sound Pressure Level Measured in 1/3 Octave Band at 1 Meter[/b]</td><td align="center" valign="middle"><strong class="white">Audibility Range in Nautical Miles[/b]</td></tr><tr><td align="center">I</td><td align="center">> 200</td><td align="center">70-200 Hz</td><td align="center">143 dB</td><td align="center">2</td></tr><tr><td align="center">II</td><td align="center">75 -200</td><td align="center">130-350 Hz</td><td align="center">138 dB</td><td align="center">1.5</td></tr><tr><td align="center">III</td><td align="center">20 - 75</td><td align="center">250-700 Hz</td><td align="center">130 dB</td><td align="center">1</td></tr><tr><td align="center">IV</td><td align="center">< 20</td><td align="center">250-700 Hz</td><td align="center">120 dB</td><td align="center">0.5</td></tr></tbody></table>
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Old 09-05-2011, 11:56 PM   #2
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When to start blowing your fog horn


Every weekend afternoon in the summer, we would leave Angel Island heading to Berkley. We would have to enter and cross the thick fog bank that comes into the Bay making its way up to San Pablo. We would start blasting the horn just before entering the fog (one prolonged blast every two minutes). We would listen intently for tankers making their way in or out of the Richmond Chevron tank farm, or for freighters heading up the Delta. We only had a close call once. We heard the sound of engines in the fog and then this big ass tanker comes out of nowhere about a hundred yards ahead of us. No horn, no bell, nothing. Moving way too fast for conditions.

Frankly though, I was usually more worried about not running smack into the Berkley Pier which sticks out about three thousand feet into the bay. Sometimes I would focus so much on navigating that I would forget about the horn. Usually we would be under jib alone so that I could change course before hitting something. What a relief it was to finally come out of the fog*bank, sometimes right where I thought I would be, sometimes not, and I would*think, holy s--t, how'd I get here.

*Anyway, I think when to start sounding your horn is a judgment call. I dont think there is anything in the regs that stipulate distance.
Also, vessels over 100 meters are required to have a horn, a bell, and a gong.*** *KJ







-- Edited by KJ on Tuesday 6th of September 2011 05:17:27 PM
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Old 09-06-2011, 02:33 AM   #3
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RE: When to start blowing your fog horn

When I hear the big boys start to blow , its time for me too.

Compressor and air horn , so noise supply is no problem.

No law against being early , big hassle if too late.
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Old 09-06-2011, 07:16 AM   #4
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RE: When to start blowing your fog horn

"Anyway, I think when to start sounding your horn is a judgment call."

Definately a judgement call, but not at 2 miles vis, that is too soon IMO. We have less than 2 on many occasions around the Mystic, Ct area, and that is plenty of vis for navigation. I*probably would not bother firing up the radar in that.

Mayb when less than 1/2 mile would be proper to sound a horn. I have an automatic fog horn built into my VHF.


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Old 09-06-2011, 08:57 AM   #5
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RE: When to start blowing your fog horn

markpierce wrote:
When should one start blowing one's fog horn?
*When it's foggy we boat in the fog.* We start sounding our horn when we enter the fog, which seems to be what everyone else around here does too, including the Washington State Ferries.
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Old 09-07-2011, 10:16 AM   #6
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RE: When to start blowing your fog horn

good to know..
long beach often has grey light fog, and its thick too.. but still it seems few are using horns.
radar is a nice thing though..
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