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10-02-2017, 10:59 PM
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#21
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Guru
City: Kenai, Alaska
Vessel Name: Melanie Rose
Vessel Model: 1999 Willard PH
Join Date: Feb 2013
Posts: 1,236
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Some of the areas I have to transit have heavy tides that can turn moderate seas into really heavy roll "for little while". Sometimes (usually) it's only for a few hundred yards and then the "fun" is over and it's back to happy cruising. I have learned to always have everything very well secured transiting those areas. There is no way you are going to secure anything while the fun is going on. One time I lost a fish cleaning table and a landing net in that couple of hundred yards of fun :-)
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10-02-2017, 11:44 PM
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#22
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Guru
City: Between Oregon and Alaska
Vessel Name: Charlie Harper
Vessel Model: Wheeler Shipyard 83'
Join Date: Jun 2016
Posts: 3,023
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You want as much weight below the waterline as is reasonable. The more low weight, engines, fuel, water, the better and makes for a quick recovery. Commercial fishing, going where I shouldn't have gone in the conditions, I rolled 90°, got caught in rollers and went to 90° the other way, once again to the 1st 90°. By then I was out of the rollers. I have witnesses, one I am divorced from.
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10-03-2017, 12:13 AM
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#23
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Senior Member
City: Camarillo
Join Date: May 2015
Posts: 438
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Ballast really helps a lot
As "Al" of Al-Ketchikan said in above post & he is correct -- Ballast does make a big difference.
PHP Code:
With 1400 # in 50# lead ingots laying over the keel running from aft of the anchor bulkhead in the bow to the bulkhead fore the lazarette, with the major portions under and surrounding the engine, the roll on our boat has been reduced to a very soft motion This on a 28'L X 9'.6"B x 4'D. The original draft was 3'.6". The added weight increased the final draft by 6". It is pure pleasure to have 'rollers' of 3 feet come under the boat and the boat remain vertical for the most part with that soft roll expressed. I'd say well placed ballast is required in the majority of our pleasure boats. Added weight above the center of gravity should not count in my opinion, it has to be low and centered.
Also read what " Lepke" has to say - center of gravity is so important to be low.
So that is something to think about. I recommend it be secured rather then just laid in place. You don't want any sudden unexpected shifts to cause an issue. But the theory is the same - Lower that center of gravity
Alfa Mike
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10-03-2017, 12:38 AM
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#24
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Guru
Vessel Model: Nordic Tug 37
Join Date: Sep 2015
Posts: 1,107
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Boat openings hole for exaple the machine room air inlet, this set the maximum angle when the water penetrates inside and the vessel loses more stability.
NT max angle is about 45° emphty boat and 40° load boat when water coming in engine rooms and The game begins to become dangerous, loose liquid or other load increases the risk of crashing not logically(NT does not bilge pump in machine room standard.)
In my opinion, every manufacturer should give the boat GZ-curves to the boat users in order to see approximately how the boat behaves in theoretical swing and what is the biggest angle before the gapazitance. I asked this GZ-curve NT manufacturer but I did not ...
You can see what small improvements the Nordic tug made that they got the CE mark B for the vessel on the European market and a bit of general stability
http://r.search.yahoo.com/_ylt=A0LEV...YVuR5doUur7TQw-
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10-03-2017, 12:45 AM
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#25
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Guru
Vessel Model: Nordic Tug 37
Join Date: Sep 2015
Posts: 1,107
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Quote:
Originally Posted by OldDan1943
Check with the designer..... Of course, that figure will no doubt be an empty boat.
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Hi tug's!
Has AT given the owners information on stability and GZ-curves ? NT did not give them to me despite my request .
NBs
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10-03-2017, 12:53 AM
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#26
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Guru
Vessel Model: Nordic Tug 37
Join Date: Sep 2015
Posts: 1,107
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Quote:
Originally Posted by alfamike
As "Al" of Al-Ketchikan said in above post & he is correct -- Ballast does make a big difference.
PHP Code:
With 1400 # in 50# lead ingots laying over the keel running from aft of the anchor bulkhead in the bow to the bulkhead fore the lazarette, with the major portions under and surrounding the engine, the roll on our boat has been reduced to a very soft motion This on a 28'L X 9'.6"B x 4'D. The original draft was 3'.6". The added weight increased the final draft by 6". It is pure pleasure to have 'rollers' of 3 feet come under the boat and the boat remain vertical for the most part with that soft roll expressed. I'd say well placed ballast is required in the majority of our pleasure boats. Added weight above the center of gravity should not count in my opinion, it has to be low and centered.
Also read what " Lepke" has to say - center of gravity is so important to be low.
So that is something to think about. I recommend it be secured rather then just laid in place. You don't want any sudden unexpected shifts to cause an issue. But the theory is the same - Lower that center of gravity
Alfa Mike
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The weight point drop too low causes more stability that will result in motion acceleration which will cause more sorrows to roll the boat(Movement fast and acceleration large).
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10-03-2017, 01:10 AM
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#27
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Guru
City: Adelaide
Vessel Name: Kokanee
Vessel Model: Cuddles 30 Pilot House Motor Sailer
Join Date: Jul 2012
Posts: 3,218
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Quote:
Originally Posted by seattleboatguy
If I had to guess, I would say too much roll for the average trawler crew would be around 20 degrees each way, and too much roll before the trawler itself became dangerously unstable would be more like 50 degrees. What are your thoughts?
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Every boat is different, along with every captain, but I think your estimates are close for most recreational trawlers and crew.
Although my boat is a motorsailer, it is based on a full displacement cruiser hull similar to a Willard. There is some ballast in the keel but I don't know how much.
I've had it laying down at about 60-70 degrees when hit with a freak gust of wind when under full sail. That is well beyond my comfort limits and it sure seemed dangerous at the time, but I don't if I was to capsizing.
One thing that really adds to the risk of capsizing is a shifting load. If stored gear, dinghy, fuel/water tanks, batteries, etc break loose, then it starts getting ugly real fast. Especially anything stored on the flybridge or cabin roof (including people). Keep your load secure.
I had a hot water tank come loose, at the most inopportune time on my first venture into rough water with this boat.
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10-03-2017, 02:10 AM
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#28
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,482
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I spilt a drink once.
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10-03-2017, 04:55 AM
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#29
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Guru
Join Date: Oct 2007
Posts: 22,553
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The distance a boat rolls is not what causes a vomitorium , it is the speed of reversal between rolls.
I would rather be on a boat that rolls 5 deg further than a boat that snaps up .
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10-03-2017, 06:00 AM
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#30
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Guru
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,148
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Weight low may prevent the roll to a point but it can make it a snappy roll. Which itself can be small but miserable .
If naval architecture only needed one formula, we all would be one.
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10-03-2017, 06:31 AM
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#31
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Guru
City: North Charleston, SC
Join Date: Sep 2010
Posts: 4,870
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Quote:
Originally Posted by ksanders
How much roll is too much???
If you are unhappy it’s too much!
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That's a good enough answer for me. Boating is supposed to be fun. If you're uncomfortable or getting sick, it's not fun.
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10-03-2017, 06:39 AM
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#32
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Guru
City: Aventura FL
Vessel Name: Kinja
Vessel Model: American Tug 34 #116 2008
Join Date: Oct 2017
Posts: 10,595
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I questioned the builder of my Nordhavn 46 about the max recoverable roll.
His answer was something like, 'The boat can recover from a significant roll. Can you survive from this same significant roll? Probably not.'
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10-03-2017, 06:44 AM
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#33
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Guru
City: Aventura FL
Vessel Name: Kinja
Vessel Model: American Tug 34 #116 2008
Join Date: Oct 2017
Posts: 10,595
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Many of us add 'stuff' to the upper deck maybe a crane and tender, an off shore life raft, a dock box for spare lines..... all these things will decrease the chances or recoverability from the factory specs.
What happens if you have guests on the top deck? 4 or 5 150# guest will have a significant effect on the recoverability especially if they all rush or are thrown to one side.
My dad was part of a group watching a boat race, on an official real life tug boat. The tug turned turtle when everyone rushed to one side. No lives lost.
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10-04-2017, 05:42 AM
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#34
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Guru
Join Date: Oct 2007
Posts: 22,553
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A seakindly boat will have a longer roll period.
With loose dock lines one can go side to side and get most boats to roll.
Time the roll period , full up on one side to same position after the roll.
4 seconds , 6 seconds, 8 seconds your stomach will notice the difference.
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10-04-2017, 07:34 AM
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#35
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Guru
Vessel Model: Nordic Tug 37
Join Date: Sep 2015
Posts: 1,107
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10-04-2017, 11:00 AM
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#36
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Guru
Join Date: Dec 2007
Posts: 4,021
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We have an auxiliary, never used, stainless steel water tank under the forward cabin sole on our sun deck trawler, capacity unknown as it is encapsulated by boat and cannot be measured. Wonder if fillin' it would take out some of the roll on our unseakindly boat?
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10-04-2017, 11:08 AM
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#37
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Guru
City: Walnut Grove Ca
Vessel Name: Cary'D Away
Vessel Model: Hatteras 48 LRC
Join Date: Apr 2012
Posts: 887
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Right on
[QUOTE=ksanders;597647]How much roll is too much???
If you are unhappy it’s too much![/QUote Round chine boats will in general recover from higher degrees than hard chine boats.
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10-04-2017, 12:05 PM
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#38
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Guru
City: Boston
Vessel Name: Adelante
Vessel Model: IG 30
Join Date: Nov 2016
Posts: 1,609
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Quote:
Originally Posted by Crusty Chief
From my experience, the boat will take more than you will.
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Ditto.
Rule of thumb is a wave 1/2 the length of your boat can flip it.
So if you are in 8' avg height seas with a 30' ft boat, (can't imagine you would be) it's likely a 15 ft wave will eventually come along. You'd better not be beam to when it hits.
My wife likes a level boat so if conditions are over 3-5 I'm apt to stay where we are until it quiets down.
Broaching worries me more than rolling. Many of us have to come through an inlet to reach a port and trawlers aren't noted for a lot of reserve speed or large rudders. 8 footers on the stern can be exciting.
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10-04-2017, 01:52 PM
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#39
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
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Quote:
Originally Posted by ancora
We have an auxiliary, never used, stainless steel water tank under the forward cabin sole on our sun deck trawler, capacity unknown as it is encapsulated by boat and cannot be measured. Wonder if fillin' it would take out some of the roll on our unseakindly boat?
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ancora,
Probably not as the tank may be very close to CG. If it's on CG there will be little roll damping.
I had an Albin 25 before the Willard and there was a blurb in the manual that recomended that if ballast was to be added it would be most effective where the deck meets the topsides close to the caprail .. on each side. Or in uneven amounts to deal w a list. Quite far from the CG. I didn't try it but the Albin is a light boat that had a visious snap roll.
I steer courses that are at an angle that puts one wave on the fwd qtr and another on the aft opposite qtr. If the fwd wave is trying to roll the boat clockwise the aft wave will be trying to roll the boat anti-clockwise. They of course cancel each other out .. no roll. You may be amazed. You can practice achieving that on boat wakes. Get the right angle and your boat will just rise and fall a bit. The waves are always there .... or there's no roll.
__________________
Eric
North Western Washington State USA
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10-04-2017, 07:09 PM
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#40
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Guru
City: ketchikan, Alaska
Vessel Name: 'SLO'~BELLE
Vessel Model: 1978 Marben-27' Flybridge Trawler(extended to 30 feet) Pilothouse Pocket Cruiser[
Join Date: Apr 2012
Posts: 2,206
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I recommend it be secured rather then just laid in place. You don't want any sudden unexpected shifts to cause an issue. But the theory is the same - Lower that center of gravity
Alfa Mike[/QUOTE]
Sorry. I did secure the ingots that are along side the engine stringers. I used WIDE Gorilla tape. Stuff sticks to the fiberglass really and as the ingots are only 1-1/2" thick by 5" wide, the ones stacked on top of each other are confined by the engine stringers and the hull shape which accepts them 2 deep.
All is well
Al
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