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Old 09-09-2013, 01:32 PM   #1
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Wake Slap in Bow Area

Hello all. We are thinking of purchasing a GB 42 Europa or Classic. Our current trawler, our first after sailing, is a semi-displacement that has a lifting chine or something similar near the bow that causes a lot of wave noise in the front cabin, even with small chop. This is quite annoying, and can get outright loud, when anchored out. Any GB owners know if the GB hull has a similar feature that causes this wave noise? We are used to the smooth sailboat hull with no wave slap. I can't tell from photos of the GB hull if this hull is area similar or not. Any thoughts on the subject?

Thank you in advance.
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Old 09-09-2013, 01:44 PM   #2
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I can sympathize, I know exactly what you mean and how loud it can get. Not sure about the GB lines. But I suspect most semi-displacement hulls suffer this curse. My OA Mk 1 certainly does.

If anyone has a good cure I'd love to hear it. I have been thinking about insulation/sound deadening on the offending areas but its hard to get to and a big job. And I dont know how effective it would be.
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Old 09-09-2013, 01:50 PM   #3
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Greetings,
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Old 09-09-2013, 01:57 PM   #4
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Try out bow-slapping with a metal hull! ... But doesn't the GB 42 have the master suite in the stern?
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Old 09-09-2013, 02:02 PM   #5
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Quote:
Originally Posted by markpierce View Post
Try out bow-slapping with a metal hull! ... But doesn't the GB 42 have the master suite in the stern?
Classic, yes. Europa, no. AFAIK.
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Old 09-09-2013, 02:05 PM   #6
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This is a picture of what I did when I owned a Defever 45 PH. I had the yard, where I was getting a bow thruster installed, put in a fillet. They filled it using a putty and than put a layer of glass over that.

I remember trying to sound proof the noise from the inside and that didn't work at all for me. This fillet totally quieted the wave slap.

This fix may affect the performance of your boat if you do run it on a plane. My Defever didn't have enough power to go much above hull speed so the fillet didn't matter.

Ron
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Old 09-09-2013, 02:12 PM   #7
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I had thought of a fillet, but have not looked at the practical aspects yet. How long was it, and how far back, and below, the waterline did you put it? I guess some experimentation with some foam/velcro might be worthwhile doing before a permanent glass job.
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Old 09-09-2013, 03:20 PM   #8
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I happen to have a Grand Banks 42 docked right in front of me at the marina, so I took this bow on shot. There seems to be a hint of a chine but nothing like what my NT 42 has, which has the annoying bow slap.

The GB appears to be an early '80's model; don't know what later versions would look like.
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Old 09-09-2013, 04:08 PM   #9
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Wave slap is also a problem in some sailboats with an aft cabin.

SlapSilencer eliminates excessive wave slapping noise in aft cabin sailboats | From Anson Sailmakers NH

Same item here:

Cabin: HunterOwners.com chandlery

Might be adaptable?
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Old 09-09-2013, 06:27 PM   #10
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We have a 1996 Grand Banks 46 Europa. Master stateroom is forward. Underway there is loud wave slap. At anchor or on a mooring it is silent. No wave slap at all regardless of conditions. Since I don't sleep underway, it has not been an issue. Hope this helps.
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Old 09-09-2013, 09:02 PM   #11
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Quote:
Originally Posted by Insequent View Post
Ron
I had thought of a fillet, but have not looked at the practical aspects yet. How long was it, and how far back, and below, the waterline did you put it? I guess some experimentation with some foam/velcro might be worthwhile doing before a permanent glass job.
This was done about 6 or 7 years ago and as I have trouble remembering what I did yesterday, I am low on actual measurments. Looking at the picture, the fillet begins at the beginning of the chine forward and goes back to about 6 inches below the normal waterline. You can see where the normal waterline is by the difference in color of the blue bottom paint. The fillet looks to be about 5 or 6 feet long.

I will tell you that is made a huge difference in the quietness at anchor. I was very happy with the result.

Ron
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Old 09-09-2013, 09:37 PM   #12
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On some boats it may make a difference on the amount of spray thrown...always a tradeoff...
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Old 09-09-2013, 10:38 PM   #13
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No wave slap issue on mine. . . .When at anchor or anytime we're bow out to even a small wind blown ripple there is this constant gurgling sound right under the bow. No way could I sleep in that compartment

Thank god for the aft cabin or this boat would have been gone years ago.
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Old 09-09-2013, 11:01 PM   #14
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I suppose you either like it or not, the sound lulls me to sleep. If it bothered me that much I'd glass it in like Ron did, who cares about a little spray underway? Buy better wipers.

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Old 09-09-2013, 11:10 PM   #15
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What bugs me is the occasional situation when wavelets sound through the galley sink. Correction requires closing the sink's hull valve (which on the Coot requires moving the back of the starboard settee to gain access, but fortunately no tools are required.)
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Old 09-09-2013, 11:30 PM   #16
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(rt--- Sent you a Private Message re the wave slap characteristics of a GB hull)
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Old 09-09-2013, 11:33 PM   #17
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I also spoke to a couple who owned a big powercat with the same condition. They also added a fillet to each hull, and it did affect the lift of the hull for above hull speeds. No mention about the spray, but chances are likely that every action has a reaction in boat matters. I know of at least one owner who used a faux fillet with wood and a hot glue gun. It didn't hold very long but it but it was long enough to find out its effect. He had to strip the wax off that area of the hull before applying. I recall he slept overnight and was able to plane the boat for a few minutes in the morning before one side came off. He used layered thin sheets of plywood to form the shape.
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Old 09-11-2013, 08:54 PM   #18
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Did the same - reshaped the chines where they cross the waterline - from 20 deg reverse to 10 deg up - this removed 90% of the chine slap without affecting performance. Pioneer has a "fast cruise" of 12Kn and the spray pattern was virtually unchanged.
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Old 09-12-2013, 01:04 AM   #19
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If you want to hear some annoying "slap" sounds... in even the slightest ripples... try sleeping in a relatively small (32í) wooden lap strake planing hull with sharp strake edges! Noises usually donít bother me at all... But, concerning a wood lap strakeís slaps, in the dead of night - - > Never again! And, when wake waves hit the strakes the down-move suction sounds remind me of repetitive toilet plunger removal! Years ago... We sold that boat after only one noisy summer!!
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Old 09-12-2013, 10:29 AM   #20
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I feel your pain. Nordic Tugs, a semi displacement hull with hard chines, have a notorious rep for hull slap. The first night on the mooring, I knew I had to do something. Canvas wave slap preventers, which I made up, work, but a pain to deploy, and a safety factor when anchored out (not to mention embarrassing). Putting 4" of sound deadening foam panels inside hull muffled the slap, but did not eliminate it. I took the plunge and filled in the chines... a combination of bonding in CoreCell foam panels, covered with a couple of layers of carbon cloth and layers of epoxy resin. Problem solved, with no impact on performance or wave deflection. I know several other NT owners that have filled in chines (just 2 this year). Here's a link to my modifications on the NENTOA site, Great Ideas.

NENTOA Eliminating hull slap
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