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Old 30-12-2005, 20:14   #1
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pirate Hull Slap at Anchor

I have recently purchased a Beneteau First 35S5. I love absolutely everything about her except for.............the incredibly annoying hull slap as she rests at anchor! In anything less than completely still conditions any wave action enters from behind, lifts the stern up and then settles her down with a resounding slap! The whole boat shudders and sleep is damn near impossible. The flat design underneath is the culprit. Has anyone heard of a solution for this type of problem? It is really interfering with our cruising enjoyment. Thanks in anticipation.

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Old 30-12-2005, 20:30   #2
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There were two single-hand racers, did a lot of the runs from Calif. to Hawaii. One was and old timer and the other was much younger with a lot less experience.

They were talking about racing tactics and all the normal stuff single-hand racers talk about. At one point the young racer asked the older one. "On these races to Hawaii, dead down wind for over a week, how do you deal with all the rocking from side to side? Tack down wind? Set the jib different? Its driving me crazy fighting with this."

The older racer took a pull on his beer, looked at the horizen for a moment then leaned over to the youger racer. "Its all in technique you know.."


"Ummhmm, You see its very simple, really..."

He smiled at his young friend. "All you have to do is learn to love the rocking."

* * * * * * * *

Mine has a hull slap at anchor just like yours. That sound says to me "Your on our boat, life is good!"

-jim lee

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Old 31-12-2005, 05:13   #3
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Jeremy, yours is not an uncommon problem in these days of aft quarter cabins, under-cockpit cabins, small wetted surface canoe-bodied hulls, and the broad tendency among the AWB builders to maximize hull volume while ignoring aspects of how the boat behaves in the water. One proof of this - to answer your Q - is that vendors now make & sell a diaper of sorts, an fabric curtain that is lowered off the transom and, like the oil booms that surround commercial ships in port so their bilge discharge does not foul the harbor, inhibits impact of the water on the hull. It of course will work only to a limited degree, is a hassle to install/remove/store, and the need for such a product is an indictment on the boat builder...but there you go, that's AWB boat building these days.

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Old 31-12-2005, 06:38   #4
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Hi J,
I've also heard of those diaper / fender type hang on's that claim to minimise this form of slap - but sorry have no experience of effectiveness.
We've experienced this on most of the faster / flat aft surface yachts we've had and can only assure you - one can learn to live with it.
Noting your location, we had a JOG aluminium flyer named Krakatini which we sailed out of Perth / Freo for three years and to sleep in her one had to withstand BOOMS rather than slaps.

We found one could minimise the noise in a variety of ways.
(a) Using a bridle to anchor her so the swell did not hit directly aft (where exactly are you anchoring to experience a wave action going against the wind anyway?)
(b) ensuring most weight below was over keel or possibly further aft to minimise 'hobby-horse' movement
(c) four cartons of Swan imbibed before bedtime.

Of these, I found (c) to be most effective.

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Old 31-12-2005, 07:34   #5

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Completely agree with Jack on this one... it's the design of your boat. They are very flat and it only makes logical sense they would slap some in a choppy anchorage.
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Old 31-12-2005, 08:51   #6
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Frankly the problem is not strickly one of modern hull shape. Even the traditional boats that I owned had a problem of waves slapping under the counter. In fact, the noisiest boats that I have owned have had short waterlines and long overhangs like the Pearson Vanguard that was in my family for years. The big difference is that we now sleep at the very ends of the boat where as boats like the Vanguard had lazarettes and sail lockers at the aft end of the boat. Quarter berths were almost never used for anything except storage.

As it a cure to the problem, I understand that these diapers work reasonably well, but I have never actually tried one.

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Old 31-12-2005, 09:36   #7
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It sounds to me like your anchoring in a leeward cove where the waves enter the mouth but the wind is comming from over the land.

I've had a couple anchorages like that myself. It's not a pleasant feeling.

What I found that will calm things down was to head the boat into the waves and then set another anchor off the stern. Or a line to shore or something to keep the boat head into the waves.

As long as the wind stays fairly light (up to 10-15 kt.) it works out pretty good. If the wind picks up then you'll have to rough it out or find another spot................._/)
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Old 31-12-2005, 11:13   #8
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Another Optioin

You could try springing the rode, and experiment with different stern-on angles to deflect some of that energy while retaining an overall acceptable ride at anchor.

Springing the Rode
s/y Elizabeth— Catalina 34 MkII
"Man must have just enough faith in himself to have adventures, and just enough doubt of himself to enjoy them." — G. K. Chesterfield
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Old 31-12-2005, 19:17   #9
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I've had a lot of personal experience springing the rode on fishing boats up to 150' lying to (massive) parachute anchors. It works very well and the affect on crew morale is great. Such a simple method, the article says it all.

Positively, socially deviant.
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Old 31-12-2005, 19:18   #10
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I have to agree with JeffH ... the traditional designs also have a resounding wave slap problem, but with a full bulkhead between the cabin and the aft third of the boat, it certainly doesn't intrude on our sleep.

As for dealing with your problem, I'm with Jim Lee - learn to let it be a soothing lullabye ... at the very least, a handy indicator of sea state and direction!

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Old 31-12-2005, 21:27   #11
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hull slap


If it's just the noise that's keeping you up, get earplugs. If it's the motion as well then you may want to use your favourite sleep-inducing beverage.

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Old 01-01-2006, 17:36   #12
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Thank you all for your serious and not so serious replies. I shall try a combination of springing the rode, boat diapers, earplugs and heavy drinking as I depatr for a few days of relaxation this weeks.
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Old 01-01-2006, 18:35   #13
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Jeremy - I read your post on the slapping and looked at the design on Yacht World. I understand why you are in the back with that great double berth, but my answer would be to move to the bow. The extended stern with swim platform is a great feature and if the penalty is some wave slapping - not a bad trade off. Probably can't help you with the overly clean first mate mentioned in your other response to my Beneteau post. We carry spare sunshowers and use them about half the time to stretch our water supply. You might also modify the shower head to reduce flow. Nice boat.


We have met the enemy and he is us. - Walt Kelly
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Old 04-10-2007, 01:07   #14
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a freind has a hard chine dispacment launch. what he dose is he puts a "skirt" around the transom it works realy well. The skirt is a heave canvas with fishing weights to keep the botom in the water and the top attached to the push pit rail
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Old 04-10-2007, 05:23   #15
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hull slap at anchor

I also own a Beneteau 35s5 and love the boat except for that same problem. I keep it on a mooring in Raritan bay and at times when the waves are just right the boat slaps with a shudder. (It is more of a bang then a shudder) The problem is more noise than an uncomfortable motion .

I don't think changing the position of the boat will matter much because a wave coming at any angle can cause the problem. In my situation the wakes from the power boats seem to be the biggest problem.

I did see something on the Beneteau web site for $300 that was suppose to help this but before I spend the money I would like some guarantee it would help. I think this is the information Jeremy was looking for.

It's all good!
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