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Old 07-18-2016, 11:31 PM   #1
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Nice sea trial conditions

For about 20 to 30 minutes I watched a pair of 37 footers come straight at me in 4' following, quartering seas. The difference was startling.

Internet specs and pics of like boats:

37 Mariner Yachts International;
LOA: 37 ft
LWL: 34 ft 6 in
Beam: 13 ft 4 in
Max Draft: 4 ft
Displacement: 25,000 lb

37 Nordic Tug;
LOA: 39 ft 2 in
LWL: 37 ft 4 in
Beam: 12 ft 11 in
Maximum Draft: 4 ft 4 in
Displacement: 22,600 lbs

Both single Cummins.
The NT was probably close to 4' lower and had an RIB on the stern. The MYI had an RIB up top.

I estimated the wind to be 15-18 and boat speed 5-7 knots.

The MYI was fighting it all the way.
I could see the stern raise up to starboard, the bow dig in, slewing to port and then a heel to starboard a good 20 degrees before straightening out to do it all again.

The NT plowed through in a straight line and overtook the MYI.

Maybe they were loaded differently, maybe different skill sets, I don't know but I was thinking what a great setup for a sea trial.
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Old 07-18-2016, 11:55 PM   #2
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The NT hull form is pretty nice, but also consider that the Mariner/Helmsman 38 will have more weight and more windage up high compared to the NT, particularly with the dinghy up on the boat deck.
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Old 07-19-2016, 12:24 AM   #3
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Quote:
Originally Posted by Hawgwash View Post
For about 20 to 30 minutes I watched a pair of 37 footers come straight at me in 4' following, quartering seas. The difference was startling.

Internet specs and pics of like boats:

37 Mariner Yachts International;
LOA: 37 ft
LWL: 34 ft 6 in
Beam: 13 ft 4 in
Max Draft: 4 ft
Displacement: 25,000 lb

37 Nordic Tug;
LOA: 39 ft 2 in
LWL: 37 ft 4 in
Beam: 12 ft 11 in
Maximum Draft: 4 ft 4 in
Displacement: 22,600 lbs

Both single Cummins.
The NT was probably close to 4' lower and had an RIB on the stern. The MYI had an RIB up top.

I estimated the wind to be 15-18 and boat speed 5-6 knots.

The MYI was fighting it all the way.
I could see the stern raise up to starboard, the bow dig in, slewing to port and then a heel to starboard a good 20 degrees before straightening out to do it all again.

The NT plowed through in a straight line and overtook the MYI.

Maybe they were loaded differently, maybe different skill sets, I don't know but I was thinking what a great setup for a sea trial.
Maybe the MYI needed a little more throttle for steerage or an adjustment on the autopilot. How different are the hulls BWL?
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Old 07-19-2016, 12:33 AM   #4
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Originally Posted by bligh View Post
Maybe the MYI needed a little more throttle for steerage or an adjustment on the autopilot. How different are the hulls BWL?
Yes, things that would have been borne out in a sea trial in those conditions. Both your comments and Dave's were considered in my OP. I didn't want to be critical, just report my observation of two similar boats in exactly the same sea conditions.

The NT has a bit less beam and more LWL but other than that, I don't know hull differences. Tankage could have been quite different also.
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Old 07-19-2016, 06:12 AM   #5
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I would compare the rudder size and response ,

as well as the ability of the Auto Pilot for rate of response and adjustment.

If the boat was hand steered , that could also be a problem.
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Old 07-19-2016, 06:29 AM   #6
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The autopilot can make a tremendous difference in a following sea. When I purchased my Mainship 34T ten years ago, it came with the standard Raymarine autopilot. That boat also has a very wide beam for its size.


It would slew 30-40 degrees side to side in a 4' following sea with the autopilot, so I had to hand steer in those conditions. So I installed a Raymarine add on gyro feature and it stabilized it to 10 degrees slew in similar conditions.


I would doubt that the basic hull form caused the differences you saw. Loading, windage and autopilot were more likely reasons.


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Old 07-19-2016, 08:59 AM   #7
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Hawgwash is right that those conditions would be terrific for assessing any boat's hull form and responsiveness (along with the drawer and cabinet latches). Being familiar with the boat's load-out plus being "hands-on" at the helm would be the way to reach conclusions, though.

Those are two interesting boats to compare. In that setting, the NT's slightly longer (waterline length), narrower hull probably made a difference all by itself.
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Old 07-19-2016, 10:15 AM   #8
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Another thing is power setting. My light planing hull can be downright squirrely in following/aft quartering seas a couple knots below hull speed. But if I give some extra rpm she tightens right up.

My AP in those conditions is pretty sloppy. If I handsteer, it is much better as you can anticipate vs the AP merely reacting.

Could be the difference seen in the two boats is more due to one operator really knowing his boat.
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Old 07-19-2016, 12:29 PM   #9
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In my limited experience trim tab settings also make a difference in the conditions you describe. I see SD boats at speed with the bow low, which makes sense in some conditions but maybe not following seas. In my Mainship 34 I've been experimenting with speed, autopilot settings and trim tab setting in quartering waves, and there is a significant range of behaviour across variations of all three. Generally speaking allowing the bow to rise (less trim tab) improves stability and steering response.
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Old 07-19-2016, 04:55 PM   #10
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I have been considering a Helmsman and the one single-most question I have had with the performance of these vessels is how they would react in a large following sea. From aft pics below the waterline, they have a squared off transom, no round or gentle edges to allow the sea to pass under the hull. I am not sure what the hull or transom shape is on the Nordic Tugs.

I too agree with the OP, what a wonderful way to compare performance and ride by getting two boats out side by side. I wonder how dealers would react to that setting! I will now make every attempt to set up sea trials of boats on my short list the same day, same body of water, preferably same time!
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Old 07-19-2016, 05:20 PM   #11
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Quote:
Originally Posted by Jeff F View Post
In my limited experience trim tab settings also make a difference in the conditions you describe. I see SD boats at speed with the bow low, which makes sense in some conditions but maybe not following seas. In my Mainship 34 I've been experimenting with speed, autopilot settings and trim tab setting in quartering waves, and there is a significant range of behaviour across variations of all three. Generally speaking allowing the bow to rise (less trim tab) improves stability and steering response.
I think more than bow up, it's the tabs that make the difference. Tabs down in those conditions will get your ass pushed all over the place. A true test is both boats piloted by the same person.

I've delivered a few Nordics and did not find them any better (or worse) than most other non-displacement hulls.
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Old 07-19-2016, 05:25 PM   #12
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Originally Posted by boatpoker;
A true test is both boats piloted by the same person.
That's the ticket. Plus both loaded equally; cruise ready.
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Old 07-19-2016, 05:52 PM   #13
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Quote:
Originally Posted by Jim Cooper View Post
I have been considering a Helmsman and the one single-most question I have had with the performance of these vessels is how they would react in a large following sea. From aft pics below the waterline, they have a squared off transom, no round or gentle edges to allow the sea to pass under the hull. I am not sure what the hull or transom shape is on the Nordic Tugs.

I too agree with the OP, what a wonderful way to compare performance and ride by getting two boats out side by side. I wonder how dealers would react to that setting! I will now make every attempt to set up sea trials of boats on my short list the same day, same body of water, preferably same time!
I have seen the NT hulls out of the water and my recollection is that they are pretty similar to the Helmsman (and my North Pacific) in the stern section. The bows of the NT are a but more bluff. As others have noted, the width of the hull may make a difference there, but in the example that HW gave, I think it is likely the difference in the CG between those two boats and where the dinghy happens to be.
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Old 07-19-2016, 07:00 PM   #14
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Quote:
Originally Posted by Jim Cooper View Post
I have been considering a Helmsman and the one single-most question I have had with the performance of these vessels is how they would react in a large following sea. From aft pics below the waterline, they have a squared off transom, no round or gentle edges to allow the sea to pass under the hull. I am not sure what the hull or transom shape is on the Nordic Tugs.

I too agree with the OP, what a wonderful way to compare performance and ride by getting two boats out side by side. I wonder how dealers would react to that setting! I will now make every attempt to set up sea trials of boats on my short list the same day, same body of water, preferably same time!
Jim,

Here's a post that you might find interesting by my late friend, windmist.

Trawler Forum - View Single Post - Articulating rudder 101

I saw this rudder in action and the boat behaved much like it had a stern thruster in close quarters handling. Based upon Ron's post, it sounds like it did not do much to improve the following seas handling. With a larger engine, a turn of speed might solve the issue, but Ron's boat was limited to about 7-8 kts.

Here are some other related threads...

torgue for articulated rudders

Rudder Modifications

As I recall, some 34 Californian LRC owners have modified their rudders for improved performance in following seas by enlarging the rudders' area.
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Old 07-19-2016, 07:38 PM   #15
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My fantail is ok in head seas, abominable in beam seas and quite simply the best I've ever piloted in following seas. I brought her from Lake St. Clair to Toronto in early September 2014 in a horrible storm on Lake Erie that brought down buildings in Toledo...... 12' following seas with a 2.5 second period and never spilled the coffee.

She was however, an absolute bugger to handle in close quarters so I added fishtails to the rudder ..... don't need no stinkin' stern thruster ! The response is amazing. I'll have to wait for some big following seas to see if I've created a problem at the other end of the spectrum.
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Old 07-19-2016, 09:11 PM   #16
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[QUOTE=FlyWright;462055]Jim,

Here's a post that you might find interesting by my late friend, windmist.

Al - interesting threads...thank you
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Old 07-19-2016, 09:15 PM   #17
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Now this is what I consider nice sea conditions. In this case, in Carquinez Strait off the industrial section of Benicia:

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