Hull slapping on chine

[Frosty]

Originally Posted by firehoser75

It is my understanding that the NT bow design is supposed to reduce waves (green water) over the bow and making a "dryer" boat. I don't know this as fact however, and I have not heard of any owners who have "adjusted" their bows for wave slap, complaining that they noticed more water over the bow or any noticeable drop in performance.

The article I read was a link from one of the NT owners' sites. It was a pdf showing how the owner had that forward chine permanently filled in for a certain length forward and aft of the bow waterline at rest*.

He had recordings you could play of the before and after. The after, to me, sounded like normal, after-all-you-are-on-a-boat water/hull noises. In other words, not gone, but not unexpected. The "before" was (IMO) more annoying, with hollow "schlonks," suction noises, and loud bangs in random but kind of "listen for the next one" patterns.

He mentioned (or maybe it was someone else who had done the same job) that when motoring faster than hull speed, there was enough bow rise that the filled in section was out of the water anyway, so the chine/no chine would at least not have been doing anything at those speeds.

Apparently NT does fill in some of the larger ones now right as they built the boat (40xx footers).

I would love to own a 37 NT. Swoon! Wouldn't kick a 32' out of the slip either

So what I'm taking from this thread is that if you want to avoid it during the boat selection process, look for one without that little chine at the forward waterline. (Or plan to get used to it, or fill it in.)

Frosty

BTW, I'm not against any water sound at anchor. Years ago I had a lapstrake style hull. Talk about hearing water sounds at anchor! But it was more regular "light but constant" sound if I had to describe it.

*I went and looked and here is a link to the article, including photos, if anyone is interested:

https://www.sentoa.org/maintenance_t...ine_nt_32.html

I couldn't figure out how to extract them, but there are links to the "before" and "after" sound within the article in case anyone wants to have a listen.

[Nomad Willy]

I can add that if you’re anchored, turning the boat stern-to may eliminate the slapping. And w a bridal attached to the stern cleats .. one on each side .. may eliminate “sailing” also.

[rslifkin]

Originally Posted by Nomad Willy

I can add that if you’re anchored, turning the boat stern-to may eliminate the slapping. And w a bridal attached to the stern cleats .. one on each side .. may eliminate “sailing” also.

Stern to gets rid of the chine slap, but on many boats, the slap and splash against the transom and swim platform is as bad or worse.

[Art]

Originally Posted by Nomad Willy

I can add that if you’re anchored, turning the boat stern-to may eliminate the slapping. And w a bridal attached to the stern cleats .. one on each side .. may eliminate “sailing” also.

Due to anchoring conditions throughout islands in SF Delta we are often front and rear anchored; nosed toward/into island edge - rear toward the slough/channel. This leaves our transom exposed/susceptible to wakes from passing boats. Due to speed limits and most captains' good seamanship there are usually no boats creating large wakes in the sloughs... so our boat gets not often rocked by wakes. That wakes hit us square on the stern means the "rocking" is in length of boat not width. Lengthwise rocking from wakes is way less bothersome than from on the side... virtually unnoticeable in comparison.

With that said: When anchoring such as this... wakes can force water into exhaust pipes on the transom; possibly way up into the engine [depending on exhaust configuration]. I strongly recommend to have Exhaust Flappers attached to the exhaust pipes.

https://www.westmarine.com/buy/sierr...SABEgItUfD_BwE

[bligh]

Our NT 37 has the chines and the infamous chine slap. Its usually not bad at all. I keep earplugs aboard as I thought I needed them once. But I have yet to use them . The noise I dont notice anymore and it blends into the other cacophony of noises that you experience when sleeping aboard.

Aft cabins are usually closer to the ERs, so sleeping aft is not always that advantageous. I remember once in my youth a captain woke me in the wee hours up to help reset the anchor as he could heard the anchor dragging from his bunk. His cabin was not the focsle, but he was well forward of the engine room and could hear it.

Even though I am getting ready to sail my NT37, the chine issue would not affect my decision to buy another NT. I can live with the chine slap. If you are a sensitive sleeper you will have to deal with other noises as well.

[Northern Spy]

Originally Posted by firehoser75

Frosty and OP,
Nordic Tugs, due to their bow structure can experience wave (bow) slap. We have had a couple of nights where it was terrible, but mostly you can get used to it.
Several NT owners have spent (a fair bit of) money getting some permanent, fibreglass work done to the bow area and have reported great success in reducing or even eliminating most of the noise. It is my understanding that the NT bow design is supposed to reduce waves (green water) over the bow and making a "dryer" boat. I don't know this as fact however, and I have not heard of any owners who have "adjusted" their bows for wave slap, complaining that they noticed more water over the bow or any noticeable drop in performance.
For us light sleepers, ear plugs do help.

Nordic Tugs are wet boats on a head sea.

I don't think the reverse chine does much for rolling the bow wave outward on a slow plumb bow.

It transitions well to the hard chine, though.

It also makes the boot stripe a bugger to paint.

[rslifkin]

Originally Posted by Northern Spy

It also makes the boot stripe a bugger to paint.

I'll agree with this. Taping out my boot stripe where it crosses the bit of reverse chine up forward is a pain, as it ends up making somewhat of a Z shape, but on a multi-faceted surface.

[Nomad Willy]

Art wrote;
“this... wakes can force water into exhaust pipes on the transom; possibly way up into the engine [depending on exhaust configuration]. I strongly recommend to have Exhaust Flappers attached to the exhaust pipes.“

Glad you mentioned that Art. Probably over time it could fill up a lift muffler.


Northern Spy wrote;
“I don't think the reverse chine does much for rolling the bow wave outward on a slow plumb bow”

I always thought NA’s just thought they looked cool. Still do.

[OldDan1943]

Originally Posted by Arc

You guy just aren’t tired enough. A couple shots of rum and the slapping goes away.

[OldDan1943]

Chine slap, oh yea
TOO quiet at home.

If you want distraction, turn the radio or tv on.

You hear the lady screaming on the next boat over, one does not know if one should call the police or congratulate him in the morning.