Slapping sound - SailNet Community

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  #1  
Old 09-20-2009
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Slapping sound

I am teaching my wife to sail so we have been going out for a few hours as often as possible borrowing any boat I can get my hands on.
This weekend it was Fri nite, Sat afternoon and Sun nite.
She is tired, went to bed already.

This afternoon we went out on a Pearson Ensign with an outboard. The wind was light from 0 to maybe 6 knots. The sea was almost flat just some chop from powerboats etc.

I noticed a loud banging from the stern when the boat was becalmed. I believe it was just waves slapping the overhang.
This is a picture of the hull http://www.geocities.com/SailaPearson/bP22Ensign.jpg.

Does that make sense? At first I was really concerned that something was wrong with the boat but it seemed to just be just the overhang.
Most modern boats don't have the overhang even though it looks shippy.
Is this one of the reason why? I thought it was just more interior space.
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Old 09-20-2009
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It is very possible that your slapping sound could have been caused by waves striking the "overhang". Another possibility is that the outboard might be loose on its bracket and making a noise.....?

The reason for more modern boats having no "overhang" is that a non-planing boat's hull speed is a function of waterline length. Maximising waterline length for a given hull length means reducing overhangs as much as possible, hence almost vertical stems and no overhang at the stern.

Stuart
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Old 09-20-2009
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More interior space and a longer water line for more hull speed. Unfortunately, most of the space gained is where you can't always make use of it. Many of the boats with the overhangs lie to you because as they heel the waterline grows, so any speed loss is negated.

Most likely the overhang is the source of the slapping sound.

Ken.
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Old 09-21-2009
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Try using some of those long pool noodles tied under the stern. There is a dedicated thing called a Slap Silencer which does a great job of killing the slap.
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Old 09-22-2009
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Pool noodles work well - the slapping is one of the down sides of a centre cockpit and we can't sleep in our stern cabin if the wavelets are coming from astern, we use pool noodles.

And a much more frivolous negative of a long counter (overhang) is that it counts towards overall length in the slip cost calculation.
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Old 09-22-2009
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What a great idea skip & oma.
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Old 09-22-2009
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I use the Slap Silencer. I tried the pool noodles and it did ok, but wasn't as effective as the Slap Silencer. Not cheap, but worth the money.
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Old 09-22-2009
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Quote:
Originally Posted by Omatako View Post
And a much more frivolous negative of a long counter (overhang) is that it counts towards overall length in the slip cost calculation.
Many newer boat designs have that goofy stern that adds 3-4ft to overal length, but nothing on deck So you have a 30ft boat, with the useable space of a 26 footer. (sugar scoop without the platform or steps)

Ken.
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Old 09-22-2009
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Quote:
Originally Posted by Omatako View Post
.

And a much more frivolous negative of a long counter (overhang) is that it counts towards overall length in the slip cost calculation.
You'd probably be singing it's praises if you were sailing in a big following sea.
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Old 09-22-2009
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Don't overlook the advantage of a little slap on your hull! It's a natural alarm signal. When the slap stops; your anchor is dragging! 'take care and joy, Aythya crew
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