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Old 10-02-2017, 10:59 PM   #21
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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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Old 10-02-2017, 11:44 PM   #22
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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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Old 10-03-2017, 12:13 AM   #23
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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 lazarettewith the major 
portions under 
and surrounding the enginethe 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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Old 10-03-2017, 12:38 AM   #24
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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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Old 10-03-2017, 12:45 AM   #25
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Originally Posted by OldDan1943 View Post
Check with the designer..... Of course, that figure will no doubt be an empty boat.

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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Old 10-03-2017, 12:53 AM   #26
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Quote:
Originally Posted by alfamike View Post
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 lazarettewith the major 
portions under 
and surrounding the enginethe 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
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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Old 10-03-2017, 01:10 AM   #27
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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?
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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Old 10-03-2017, 02:10 AM   #28
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I spilt a drink once.
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Old 10-03-2017, 04:55 AM   #29
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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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Old 10-03-2017, 06:00 AM   #30
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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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Old 10-03-2017, 06:31 AM   #31
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How much roll is too much???

If you are unhappy its too much!
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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Old 10-03-2017, 06:39 AM   #32
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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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Old 10-03-2017, 06:44 AM   #33
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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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Old 10-04-2017, 05:42 AM   #34
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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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Old 10-04-2017, 07:34 AM   #35
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This roll is to match me


https://video.search.yahoo.com/video...Av&fr=sfp&tt=b


NBs
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Old 10-04-2017, 11:00 AM   #36
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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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Old 10-04-2017, 11:08 AM   #37
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Right on

[QUOTE=ksanders;597647]How much roll is too much???

If you are unhappy its too much![/QUote Round chine boats will in general recover from higher degrees than hard chine boats.
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Old 10-04-2017, 12:05 PM   #38
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Originally Posted by Crusty Chief View Post
From my experience, the boat will take more than you will.
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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Old 10-04-2017, 01:52 PM   #39
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Originally Posted by ancora View Post
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?
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.
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Old 10-04-2017, 07:09 PM   #40
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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

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