how much roll is too much?

ksanders said:

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.

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.'

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.

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.

This roll is to match me


https://video.search.yahoo.com/vide...m1ajbg&age=1469640469&fr2=p:s,v:v&fr=sfp&tt=b


NBs

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?

Right on

ksanders said:

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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Crusty Chief said:

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.

ancora said:

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.

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

Everytime sailing out the Golden Gate on my father's Columbia Defender 28-foot sloop on the lightship races, I got seriously sea sick (like wishing for death). Half of the boat's weight was in the boat' keel.

When I re-ballasted my previous boat, I used bags of shot, bought from the a large sporting goods store. Advantage, they bags conform to the shape of the hull shape. Disadvantage: have to put the bag in a more substantial bag.

Al said:

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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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[/QUOTE]

So, would a 34MT have weighted underneath sine it can have a steadying sail?

Vandeusen said:

So, would a 34MT have weighted underneath sine it can have a steadying sail?

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I'm finding on ours that the keel may be filled with concrete with a layer of gravel on top.

Since I found this thread and I'm new to the traiwer world I'm learning

A lot depends on how the engine room is ventilated.
If you notice the roll over demonstration, there are no facilities to ventilate the engine room, no chance for down flooding

You shouldn't heel that much with a steadying sail and you shouldn't have to add weight or keel additions because you use one.

If you need to..... the sail is probably too big as it is not a driving sail.

psneeld said:

You shouldn't heel that much with a steadying sail and you shouldn't have to add weight or keel additions because you use one.

If you need to..... the sail is probably too big as it is not a driving sail.

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The sail is quite small, I think the flybridge canvas has more windage.

CharlieO. said:

The sail is quite small, I think the flybridge canvas has more windage.

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It's true that many production boat masts and steadying sails are more of a gimmick, so a very small sail is probably useless for steadying purposes.

But if done and used correctly can help quite a bit in some conditions.

psneeld said:

It's true that many production boat masts and steadying sails are more of a gimmick, so a very small sail is probably useless for steadying purposes.

But if done and used correctly can help quite a bit in some conditions.

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Can you give me a couple of examples

Interesting video

Vandeusen said:

Can you give me a couple of examples

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You really need to be in very strong winds for a steadying sail to be effective. A Sailboat has a huge amount of square footage in sail area. Sail roughly beam to, the wind holds their healing angle via the sail and they ride up and down on the waves. No roll.

In order for a trawler stay sail, with such a small footprint, you'd have to have a decent amount of constant wind to reduce the roll as the trawler tops the wave peak and starts to come down the other side.

IMHO, by the time you start getting to an effective amount of sail, you start to need to ballast the boat with a weighted keel as well. This is where motorsailers shine.

A proper steadying sail needs no wind to work properly...go resesrch the subject if you are truly interested.

A steadying sail is stiff and sheeted flat...it provides resistance to roll by resisting the roll through air resistance....wind may help but isn't the real factor in rolling resistance.

Every bit of info that has this many divergences in opinion needs very thorough investigation at the highest possible references as so much misinformation is published on the internet.

Heck.... many consider riding sails and steadying sails the same.

Vandeusen said:

Interesting video

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Yes, very interesting video. I just measured the roll period on my little 30 foot trawler the other day. I'm planning on doing some modifications to reduce and slow the roll. I have a 4 foot draft with a fairly substantial keel, so that helps. Forgot to get the total weight when I hauled out.

What I noticed most about the video is that that boat has a faster roll period than my 30 foot trawler! And I thought mine was snappy. The boat is light , shallow, and sausage shaped so that it can roll over. But so what if it can go completely over. Since this thread is about roll, just remember that drinks will be more comfortable on my flying bridge.

Weight down in the bilge is a sailboat thing that generally doesn't apply to SD trawlers. For a trawler, placing any additional weight out from the keel usually puts it further from the center of gravity and provides more roll elimination. Seems counterintuitive, but works. And no trawler is likely to roll back up because of lead in the bilge. Might as well place it where it can give the gentlest ride for the weight.

"For a trawler, placing any additional weight out from the keel usually puts it further from the center of gravity and provides more roll elimination. "

The sailing schooners on the grand banks would haul an anchor up the fore mast.

The weight would increase the roll angle some, but slow the roll and the hull reversal making life more comfortable on board.

FF said:

"For a trawler, placing any additional weight out from the keel usually puts it further from the center of gravity and provides more roll elimination. "

The sailing schooners on the grand banks would haul an anchor up the fore mast.

The weight would increase the roll angle some, but slow the roll and the hull reversal making life more comfortable on board.

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Good history FF.

I am often amazed at the misunderstanding of stability and the suggestions often offered up when questions are asked.

Stability and its use overall in boating design is a lot more than above the water "structure" or just exactly where the center of gravity should be.

Thus why naval architecture isn't an 8 hr course like getting a boating safety certificate.

FF said:

"For a trawler, placing any additional weight out from the keel usually puts it further from the center of gravity and provides more roll elimination. "

The sailing schooners on the grand banks would haul an anchor up the fore mast.

The weight would increase the roll angle some, but slow the roll and the hull reversal making life more comfortable on board.

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Before the mast was installed on my boat it had a very snappy roll. On the first cruise with the new mast (with no sails up yet)it was very obvious that the roll had been dampened.

My boat has 4500 lbs in the keel for ballast vs 5000 lbs in the SP Cruiser that has the full sized sail rig. The navel architect at Island Packet concluded that my smaller 40’ mast and reduced sail area would be fine with my 4500 lbs of ballast.

Anti roll tank.

Roll Attenuation and Bilge Keels

What About Anti-Rolling Tanks for Smaller Boats...?
While the displacement penalty of an anti rolling tank may not seem to be a big deal in some cases, the positioning of an anti-rolling tank is usually very problematic in terms of the accommodations, deck space, etc.

Many anti-roll tank geometries have been tried. It seems that the simpler the approach, the better. Active tanks that pump water around do not appear to be optimum, since the water pumping requirements may be quite extreme, therefore they tend to be expensive, noisy, and power hungry. The most viable "active" system appears to be one that is configured as a broad "U" tank that is joined by an air tube across the top, having a valve that's controlled by the ship's gyro. It should go without saying that these are complex and expensive to set up even aboard larger ships.

For the sake of simplicity and economy, it appears that passive tanks may be the best. Among them the simple "H" tank seems likely to be the most easily implemented with the least impact on the vessel layout, etc. If the budget allows a slightly more sophisticated system, then there may be other possible configurations, and with them, the possibility of improved roll reduction as noted above.

The simplest tank, in the form of a broad "H" will have a large volume tank (perhaps twice the volume of the contained liquid in its capacity) at each end, joined by a somewhat narrower "slot" which forms the cross bar of the "H." In some designs, the "cross bar" of the "H" may be less narrow, and may instead be heavily baffled. There must be a good spot onboard, ideally offering the full width of the ship, and as a rule of thumb about 20% as high as that off the water. We have used this type of anti-rolling tank on our 40' Coaster design, and reports are that the tank is quite effective.

Anti rolling tanks need to be planned quite carefully. The weight of water in the tank must be able to be tolerated in terms of the stability of the boat, as well as the "free surface" effect of the water as it sloshes back and forth. The trick seems to be to get the slosh to happen out of sync with the roll of the boat.

The stability of the boat must be known precisely in order to know the correct proportions of the tank, the weight of water required for roll reduction, whether the boat can tolerate the lessened stability effect of the tank, etc. For a motor yacht, if thorough calculations show that the applicable criteria can be met with an anti-rolling tank in place, then the vessel may be a workable platform for an anti-rolling tank.

Given adequate knowledge of a vessel's stability, and given the willingness to invest in the cost of planning a proper solution, anti-roll tanks may possibly be able to be integrated into smaller craft. The real benefit of a passive anti rolling tank is that it can provide a system that does not degrade the propulsive efficiency of the vessel in order to achieve roll reduction. Several studies appear to have shown the opposite, i.e. that if a vessel can be kept from heavy rolling, efficiency seems to be increased.

Until they become commonplace, the cost of proper planning will likely keep anti-rolling tanks from being a strong contender among the other roll attenuation options mentioned here.


do you have experience with anti roll tank system?

On larger ships I have experience. USCG old school icebreakers to be exact.

They were not very effective despite having huge pumps to assist...they were better for once up on the ice to get the vessel rolling to help us back off the ice.

But like all designs...my experiences might have little to do with smaller vessel, passive tanks.

I have researched in the past a little, but I found little on the web in rudimentary searches.