How to panic powerskipper , just a bit.

[powerskipper]

I was up the top of Southampton water on the school boat Motala, now I mean right at the top near a little sailing club on the port side. We had a slight problem, in that the water pump was running but no water in the taps was appearing. So I checked the pump and yes it was running we have a cute little filter just by the pump that you can see the water flowing though, so that bit was working and the tank was emptying, again we can see the level of water in the tank and it was going down slowly but no water from taps. So I was doing my detective bit, engine bay had no water in it, so it had gone passed that bit, so checked under the floor in the galley area, yaaay, found where the water was going, so bilge pumps and good old bucket and sponge got rid of most of that, powerskipper bit happier.
So off we set again and after about 50m heard this thumping on the hull, I went down to galley, yes it was near the bow of the boat, this sounds bad i thought to myself, so went on deck and could still hear it, I thought I had caught a diver or something and he was banging the hull to let me know he was there and did not want chopped up by my props.. You can see how my mind works.
Then the thumping moved down the hull to mid ships,only then I noticed that they were pile driving new posts in at the dock area half mile away and every time they thumped the post in, about 5 to 10 second later the thump hit the hull, as we moved along the vibration or thump moved down the boat, we turned up river and it changed sides, we headed right up to the top and as we cleared the last corned it stopped.
Now it was a new one on me and one I will not forget. LOL

 

[Firefly625]

A thump is not a noise you want to hear, I can imagine the situation... And imagine the relief when the penny dropped!

 

[sarabande]

the speed of sound in water is about 4600 feet per second, and as a mile is 5280 feet, you would hear the sound from the pile driver half a mile a way in just under 6/10ths of a second, and before the sound of the driver through the air which would reach you in about 2.5 seconds.

The delay of 5 to 10 seconds is therefore, it seems, a bit of a mystery, however clearly related the pile driver activity and the hull thumps are related.

There may be other seismic reasons, such as the pile driver noise going down to a very distant layer of rock and rebounding.

 

[powerskipper]

It may have been a shorter time but felt like that at the time.

 

[lisilou]

Hahaha wish i could've seen your face!

 

[jimmy_the_builder]

the speed of sound in water is about 4600 feet per second, and as a mile is 5280 feet, you would hear the sound from the pile driver half a mile a way in just under 6/10ths of a second, and before the sound of the driver through the air which would reach you in about 2.5 seconds.

The delay of 5 to 10 seconds is therefore, it seems, a bit of a mystery, however clearly related the pile driver activity and the hull thumps are related.

There may be other seismic reasons, such as the pile driver noise going down to a very distant layer of rock and rebounding.

Does that assume zero windspeed? Could an adverse wind speed/direction alter the through-the-air timings?

Cheers
Jimmy

 

[Piers]

In the days when Concorde was flying, I was caught twice when crossing the Channel as she flew over. The first time I heard the sonic boom it sounded as if I'd blown an engine. Throttes brought sharply to neutral - but nothing was wrong. Then it dawned on me. Looking towards the west, there she was - beautiful Concorde, streaking towards the Atlantic on the Paris - New York route.

And blow me down, she had me a second time a month or so later!

Piers

 

[sarabande]

Does that assume zero windspeed? Could an adverse wind speed/direction alter the through-the-air timings?

Cheers
Jimmy

Air temperature and density affect the speed of sound more than wind speed. If you get an inversion layer above you, sound can be refracted quite long distances. I've heard ships' engines from over 10 miles away before they were on the horizon.

 

[benjenbav]

It may have been a shorter time but felt like that at the time.

There's a simple explanation. The earlier problem with the tap must've stopped you filling the kettle. Hence, you hadn't had enough tea. No wonder you were a bit jumpy.

 

[powerskipper]

There's a simple explanation. The earlier problem with the tap must've stopped you filling the kettle. Hence, you hadn't had enough tea. No wonder you were a bit jumpy.

Love it. lol

 

[oceanfroggie]

Enjoyed a good yarn.

 

[Bajansailor]

In the days when Concorde was flying, I was caught twice when crossing the Channel as she flew over. The first time I heard the sonic boom it sounded as if I'd blown an engine. Throttes brought sharply to neutral - but nothing was wrong. Then it dawned on me. Looking towards the west, there she was - beautiful Concorde, streaking towards the Atlantic on the Paris - New York route.

And blow me down, she had me a second time a month or so later!

Piers

Me too - 20 years ago, sailing from Portsmouth to Douarnenez at Easter, beating down channel, everything on the boat is going wrong, and the wind is on the nose, and then there is an almighty bang! We were convinced the mast had come down, looked all around, mast still up, hadn't crashed into anybody, and then we cottoned on. Relief! (of sorts).