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Old 09-02-2017, 02:27 PM   #1
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Just felt a thud underneath us...

Heading from Half Moon Bay to Monterey today. We are about an hour outside of Half Moon Bay with gorgeous conditions (see photo) and all of a sudden we felt a thud beneath us. Wasn't severe, but enough to hear and feel it for sure. Checked the bilge, looks fine. Engines are fine. No change in feel of the boat such as vibrations coming from the prop or anything.

Has this happened to you? I assume I just keep an eye on things and leave it at that? As you can see from the conditions, we would have seen anything noticeable in front of us, but we didn't.

Thanks,
Mike


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Old 09-02-2017, 02:42 PM   #2
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Happens sometimes.

It happened to me a couple years ago in the Stockton deep water channel. Never a leak or vibration either but boy it sure does make your butt pucker.
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Old 09-02-2017, 02:49 PM   #3
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whale bump?
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Old 09-02-2017, 03:16 PM   #4
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Navy sub communication something or other?
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Old 09-02-2017, 03:23 PM   #5
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whale bump?


There were tons of whales heading from San Francisco to Half Moon Bay. Probably saw at least 10. However, haven't seen one on this leg down to Monterey. I would expect a bigger jolt if any contact with a whale was made, but anything is possible!

I'm a new boater. Why does this #$&@ happen to me!?!? :-)
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Old 09-02-2017, 03:51 PM   #6
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Had a similar experience years ago, in Pass-a-Grille channel, departing from St. Petersburg (Florida) Beach heading west into the Gulf of Mexico. The water depth was about ten feet, with a sand bar near to hand on the north (starboard) side of the marked channel. Motoring along at about seven knots, we struck something hard enough to bring the forty-one foot, twelve-ton sailboat nearly to a stop. It was more of a "thump" than a bang, but a very hearty thump. The bow dipped, the stern rose, then whatever it was seemed to give way and we began to gather way again, practically before I could pull the throttle back.

I never knew what it was. On the next haul-out, there was a scuff on the leading each of the modified fin keel, at about four feet below the waterline In those waters of that relatively shallow depth, a marine mammal big enough to have that much effect is unlikely. Besides, we never saw anything. Have speculated a sodden, submerged timber floating out with the tide, but who knows?
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Old 09-02-2017, 04:30 PM   #7
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Heck of a lot of submerged but mobile shipping containers out there too, but I reckon you'd be very lucky to hit one so gently it wouldn't sink you
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Old 09-02-2017, 04:49 PM   #8
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Navy sub communication something or other?

We had one run under us in FL a few years back. They make them go in and out underwater at the one port.
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Old 09-02-2017, 05:02 PM   #9
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It was North Korean hackers

But seriously, it was probably some sort of marine creature. We have bumped one or two over the years. It's always startling, but I expect even more startling for the creature. Just imagine the headache
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Old 09-02-2017, 05:02 PM   #10
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Dad, in his then nearly-new '72 Morgan 27, hit a submerged something at speed at night when racing in the Chesapeake Bay. When hauled, there was the clear imprint of a large hexagonal bolthead in the leading edge of the lead keel. Years later, when I removed the rotting plywood sole which was tabbed into the hull and bedded on filler made of marble dust and polyester, I found the filler thoroughly cracked around the keel bolts and out to the edges of the filler. Clearly, that boat took quite a wallop!
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Old 09-02-2017, 05:21 PM   #11
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Actually, it just happened a second time. There are a bunch of patches of seaweed with a very thick root or something floating on top of the water that we are seeing a lot of. Have mostly avoid them when we see them, but maybe a few that were slightly submerged hit the props?
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Old 09-02-2017, 05:52 PM   #12
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Yes I hit a submerged log last week doing about 8 knots didn't see it until after when it surfaced in my wake, but sure did give me something to do for the next 20 mins or so, checking bilges etc. all ok but sure gets the heart rate up.
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Old 09-02-2017, 07:22 PM   #13
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Maybe it was a waterlogged log that wasn't very bouyant.
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Old 09-02-2017, 07:27 PM   #14
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Maybe it was a waterlogged log that wasn't very bouyant.


Maybe I'll mount a GoPro to the bottom on the way back. :-)
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Old 09-02-2017, 07:36 PM   #15
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Actually, it just happened a second time. There are a bunch of patches of seaweed with a very thick root or something floating on top of the water that we are seeing a lot of. Have mostly avoid them when we see them, but maybe a few that were slightly submerged hit the props?
Sounds like Bull Kelp?
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Old 09-02-2017, 07:51 PM   #16
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Hmmm! Happened to me last year in 600' of water. The whole boat shuddered with a large thump. It was a humpback whale. No running gear issues, which was good for us as well as the whale involved. Sure hope it was ok.
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Old 09-02-2017, 10:27 PM   #17
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[QUOTE=Blissboat;589192.....departing from St. Petersburg (Florida).....In those waters of that relatively shallow depth, a marine mammal big enough to have that much effect is unlikely.........[/QUOTE]

There are some good size sharks in that area though...

And a loggerhead turtle or a goliath grouper could get up to 400 pounds
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Old 09-02-2017, 11:08 PM   #18
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I've hit stuff that I didn't see. Whether inattention for a moment or it was submerged I don't know. We do have a lot of deadheads, submerged logs, around here. Fewer than years before but enough to be a constant hazard yet.

Sure does wake you up.
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Old 09-03-2017, 02:52 AM   #19
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Quote:
Originally Posted by MichaelB1969 View Post
Heading from Half Moon Bay to Monterey today. We are about an hour outside of Half Moon Bay with gorgeous conditions (see photo) and all of a sudden we felt a thud beneath us. Wasn't severe, but enough to hear and feel it for sure. Checked the bilge, looks fine. Engines are fine. No change in feel of the boat such as vibrations coming from the prop or anything.

Has this happened to you? I assume I just keep an eye on things and leave it at that? As you can see from the conditions, we would have seen anything noticeable in front of us, but we didn't.

Thanks,
Mike
It happened to us during our very first sail after we had purchased our last sailboat. It had just been launched after being trucked up from SoCal and we screaming on a beam reach when we felt and heard a very large thump. Never did see what it was and never could find any damage.
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Old 09-03-2017, 03:34 AM   #20
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Originally Posted by MichaelB1969 View Post
Actually, it just happened a second time. There are a bunch of patches of seaweed with a very thick root or something floating on top of the water that we are seeing a lot of. Have mostly avoid them when we see them, but maybe a few that were slightly submerged hit the props?
When you find gatherings of seaweed floating it is not unusual that floating items such as logs or wood pieces become intwine within the "Glob or Blob" of matter. Here in the Pacific Northwest and Alaska, the odd tree stock that has been floating for a long period of time and becomes water logged to the extent they are not floating vertical with a small portion protruding which are hard to see when they are submerging and re emerging with the sea action. They can sneak up and hit you midship and into your wheel in a 'Jimmy Second'. Now that sound is a real butt cheek clincher let me tell you!!

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