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Old 10-02-2017, 02:32 PM   #1
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how much roll is too much?

How much roll is too much roll in a trawler? My neighbor on the dock and I were talking about it last night. I told him my 38' Marine Trader seemed very unstable to me, but I come from a heavy displacement sailboat background, so I'm still a beginner in the trawler world. 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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Old 10-02-2017, 03:07 PM   #2
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When the refrigerator empties out on the floor you're rolling too much :-) My vessel is ballasted so I have no fear it will overturn, nor stay overturned if it did wind up in that position. Good topic though
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Old 10-02-2017, 03:14 PM   #3
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Trawlers behave very differently from a heavy displacement sailboat with a keel weight of about a third of the boat's weight. Many, maybe most trawlers have no weighted keel or ballast low in the hull.

So a trawler depends on hull form for its roll stability whereas a sailboat depends on its ballast.

A typical semi displacement hull trawler has a vanishing stability of about 80-90 degrees of heel, whereas most sailboats have at least 120 and some 140 degrees of positive stability.

With that said, I have been out in our semi displacement Mainship 34T in 8' beam seas and probably rolled 30 degrees. It was tough and a little scary but I don't believe I was in any danger.

So, back to your title question, I don't know how much roll is too much. I am sure that I would be scared shitless if I were experiencing 50 degrees of roll. And with only another 30-40 degrees of margin before turning turtle I doubt if it is safe in those conditions.

I do know that I have hit at least 45 degrees in a sailboat and although it was ass puckering I didn't feel I was in any danger.

So my best answer to your question is to keep the roll below 30 degrees and you will be fine although probably not very happy in those conditions.

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Old 10-02-2017, 03:22 PM   #4
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Ten both ways is getting too much for me.

20 is borderline where if things arent tied down tight, especially if its the right sized chop where it is snappy.

Yes .....past 50 is getting dangerous in my mind as most of us have no idea how many mods and storage has changed the stabity curves. But thats just a wild guess.

I just am spoiled with ICW cruising and too many trips rocking and rolling for work, but not giving up just yet.
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Old 10-02-2017, 03:27 PM   #5
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Check with the designer..... Of course, that figure will no doubt be an empty boat.
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Old 10-02-2017, 03:29 PM   #6
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How much roll is too much???

If you are unhappy itís too much!
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Old 10-02-2017, 04:07 PM   #7
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Some trawlers are self-righting. Interesting capsize test

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Old 10-02-2017, 04:07 PM   #8
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Rolling along.

IMHO - For a typical semi displacement trawler that is not ballasted & with an A/B Ratio of over 2.6 to 1 here is what my experience has been:

For most Semi-Displacement Trawlers with out any sufficient ballast down in your keel, chances are you will not recover from a roll of much over 60 to 70 degree roll. The designer has calculated where that point of no return is & it varies from boat to boat. This has to do with the interaction of the center of buoyancy & center of gravity relationship to each other as the boat heals over & the specific design of the particular boat your looking at.

Without sufficient ballast in your keel, the non ballasted semi-displacement trawler boat with an A/B ratio over 2.6 to 1 can be more stable upside down than it is right side up should you turn turtle. That means it will not self right should it get beyond that point.


of course there are exception like the Dutch boat shown in the video of the "Elling E-4" -- but they also use shaping to encourage self righting & have a lower A/B ratio. BTW - One more thing when it happens in the real ocean, it is not like shown in the video in a quiet bay, it can be quite violent !

My Current boat - The Kadey-Krogen 42 Trawler - which is a ballasted true full displacement hull, has an approximate A/B Ratio 2.2 to 1 & is only stable to about 85 to a max of 90 degrees of roll.
Which BTW is pretty good for a Trawler, as most all Semi-Displacement type trawlers are way less tolerant in their roll axis.
Of course other Full displacement boats with ballasted keels like the Willard's, Nordhavn's & Diesel Duck's, & the like, etc. are in that same neighborhood as the Kadey-Krogen.

Even though this boat has a displacement of 39,500 lbs., They recommend never have more than 750 lbs. up on the fly bridge or on the boat deck or that will upset the center of gravity enough to affect your max recoverable roll angle & make that then under the wanted self righting recoverable angle of roll of 85 degrees, if weight over that 750 lbs. is up there. Yes, I was told this is calculated with 1/2 tank fuel & 1/2 tank water. Filling both gives you about another 5 degrees I am told - but never tested. However, I have never asked the designer the specifics of the details except the interior is empty of everything not factory installed.

So center of gravity is big a key element.

How much roll under those maximums you can comfortably tolerate is up to the crew to decide. When your at 60 or 70 degrees your almost walking in the walls. Anything over 80 degrees you are on the walls. BTW - not recommended.

Most crew get pretty uncomfortable past 30 to 35 degrees.

Good Luck.

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Old 10-02-2017, 04:16 PM   #9
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Heavy weather expected? If you cant our run it and cant find a place to hide the boat. Be considerate and get a bucket. Lower the water level in the head too.
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Old 10-02-2017, 04:20 PM   #10
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Quote:
Originally Posted by gsholz View Post
Some trawlers are self-righting. Interesting capsize test
That's a pretty cool video. I suspect the Coast Guard boats in Astoria can do the same trick. Very impressive.
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Old 10-02-2017, 05:07 PM   #11
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What percentage of a Ford Lehman is considered ballast?
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Old 10-02-2017, 05:31 PM   #12
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I'll get back to you in that.

I'll have to get back to you on that.

Part of the issue is that it is not in the keel.
Typical Ford Lehman is bolted on top of the stringers and weighs about 1,060 lbs.
So it is relatively low in the boat, but not much below the boats actual center of gravity.
So the lever arm is shorter & reduces it's effectiveness.

So the lever arm is very short in relationship to the center of Gravity which reduces its effectiveness when it comes to roll stability.

Contributes some, but not enough.

But lead bars bolted to stringers at bottom of the bilge would help some as they are below the engine so lever arm is a bit longer. Still preferable is in the keel.

Good luck with your "Lehman ballast".

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Old 10-02-2017, 05:35 PM   #13
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Quote:
Originally Posted by gsholz View Post
Some trawlers are self-righting. Interesting capsize test


All boat tests should strap in the marketing guy during the test.
Very strong windows
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Old 10-02-2017, 06:35 PM   #14
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Quote:
Originally Posted by gsholz View Post
Some trawlers are self-righting. Interesting capsize test

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Old 10-02-2017, 06:41 PM   #15
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Quote:
Originally Posted by ksanders View Post
How much roll is too much???

If you are unhappy itís too much!
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Old 10-02-2017, 07:47 PM   #16
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I once was told by a navy seaman that the frigate he sailed with had a certain point at which the gun turrets would part ways with the vessel if roll exceed a certain point.
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Old 10-02-2017, 09:02 PM   #17
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[QUOTE=alfamike

But lead bars bolted to stringers at bottom of the bilge would help some as they are below the engine so lever arm is a bit longer. Still preferable' is in the keel.

Good luck with your "Lehman ballast".

Alfa Mike [/QUOTE]


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 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.
This offered from one who's cheeks of his butt were found up around his ears when the boat was NOT ballasted as described.

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Old 10-02-2017, 09:14 PM   #18
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When the refrigerator empties out on the floor you're rolling too much...
That has never happened to me on my boat, but it did happen on a cruise ship during a gale in the Tasman Sea.
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Old 10-02-2017, 09:25 PM   #19
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Simple formulas for roll. Too much roll=point of significant discomfort. Iron stomach and care free attitude cockpit full of water=too much roll.
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Old 10-02-2017, 10:37 PM   #20
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From my experience, the boat will take more than you will.

Nothing nice about 30+ degrees in each direction, but the boat pulled through. Cant say the same about the Admiral.

I try my best to avoid anywhere near that and the admiral appreciates my effort.
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