Boat Roll

[Fish Isla]

The wife and I are looking for a new boat. I know they roll with the soft chine. Can anyone comment on how they are stabilizers.

 

[DavidM]

A round bottom, displacement hull like the Krogen rolls in a beam sea but the motion is softer than a semi-displacement hull and should feel more comfortable in the same conditions.

Active stabilizers do work, but I have no experience on a Krogen. You can read about experiences of others with stabilizers on other boats by searching on stabilizers on this forum.

David

 

[meridian]

I have Naiad stabilizers on my Krogen 42. Night and day when activated on a beam sea.

 

[meridian]

What brand and model are you looking at?

 

[Fish Isla]

In this order Defever Krogen Nordhavn

 

[Martin J]

Totaly agree with Meridien
My 50ft Cheoy Lee is night and day.
Can go from 30 degree to 10-15 with the stabilzers in a quartering sea 25-30kts wind 6ft sea. Naiad stabilzers now (36yrs old)

 

[Maerin]

The wife and I are looking for a new boat. I know they roll with the soft chine. Can anyone comment on how they are stabilizers.

Our 43 Selene/Solo is stabilized, Wesmar. Makes the difference between stuff tossing off the shelves or not. Astounding difference. Ask anyone who has a boat with stabilizers if they'd like them removed at no cost... I can pretty well predict the answer.

 

[Fish Isla]

Salene is on my list. Another 43 was listed yesterday. I am moving away from the nordhavn having a bridge is a priority.

 

[hfoster]

I have Naiad stabilizers on my Krogen 42. Night and day when activated on a beam sea.

+1.

Stabilizers are must on my vessel when doing long trips.

Cheers.

H.

 

[CaptSteve53]

If you are looking for comfort keep looking at full displacement hulls (not semi planning or fast hulls). What comes into play is the Moment of Inertia as to the type of roll you will experience (either a sharp correction or a slower more comfortable correction), this is often vessels with an overall heavier top side build (like steel) will have a better roll motion than a GRP vessel.

As above vessels with mechanical Stabilizers perform way better than those with out basically in any type of sea conditions, most of these are electric/ hydraulic operated with external fins, which in most cases are designed to break off in any major incident rather than damage the hull.

In modern vessels these are slowly being replaced by gyro stabilizers, which have no fins or external equipment of any kind , the up side is that they even work at anchor (very well) down side you must have your gen set running

Cheers Steve

 

[Irish Rambler]

I would like someone to come up with a gyro computer programme that can be connected to both stabilizers and trim tabs that can work in unison, (yes, patent pending).
Anyone interested in building/marketing get in touch via private email.

 

[Mako]

I agree that some sort of stabilization is needed for any long distance motor cruiser. My steel hard chine didn't have any and the roll in bad conditions was really not fun. However you should check all your options: active stabilizers; paravanes; passive flume tanks; gyros; etc.

What are your requirements - your priorities? For example, if you really require to subdue the motion while anchored then the answer is going to be quite different from the norm.

 

[Irish Rambler]

A cheap and simple solution for steel boats is to fit a fairly long chine either side of the keel (and the keel if possible) using 'Laski effect' steel.

 

[Nomad Willy]

IR,
I think you're talking about bilge keels. I don't really know but I'd shy away from them because they may induce chine tripping and hence possible capsizing.

I prefer a boat that will slide sideways on the face of a big wave.

 

[Simi 60]

Bilge keels or rolling chocks?
One is a lot larger than the other.

 

[Wxx3]

IR,
I think you're talking about bilge keels. I don't really know but I'd shy away from them because they may induce chine tripping and hence possible capsizing.

I prefer a boat that will slide sideways on the face of a big wave.

Really good point. Thanks.

 

[Gordon J]

Stabilizers Worth Every Penny

We have a semi displacement hole on our Ocean Alexander 456. We have Trac stabilizers with three different modes of operation. I have been in 4 to 5 foot seas and not felt any side to side motion. Riding on our boat is more a kin to writing an elevator. I would not have bought our boat last year if it had not had stabilizers installed six years ago by the previous owner.

I have never heard of anyone who had stabilizers who wished they did not have them. I do have friends however, who have to limit their boating, because they or their wives have a difficult time with seasickness. One of these is a DeFever 49, no small boat and a full displacement hull.

 

[Irish Rambler]

Yes I was talking of bilge keels and they've proved very effective both underway and stiffening a 'tender' boat. In all my years on the water I've never heard of a boat tripping on this side of the pond.
A boat with stabilizers here is as rare as hens teeth.
I'm afraid I'm a coward, not wanting a divorce I check the weather and don't go out in more than a Force 3/4 gusting to 5.
I know which side my bread is buttered on ! (Irish expression). Meaning I know when I'm well off.

 

[Al]

Is there a biblical formula in the maritime world in the proportions of rolling chocks in terms of construction to meet beam/length/depth? What determines the construction size of a given set of chocks? I have never read where measurement are included. Just that a boat had rolling chocks installed. Viewing many examples on boats on the hard, they vary in configurations/size.

As happy as I am with the ballast that I have mentioned numerous times on the forum, one wonders if installing a set of chocks would enhance the improved roll motion even more (cost being one consideration).
In speaking with a marine fiberglass repair/construction fellow in Wrangell AK, constructing chocks is a common enough project, in the same class as bulbous bow components , that a couple of days is all it would take to lay up a pair and install. Very tempting. Thoughts?

 

[Wxx3]

I know which side my bread is buttered on ! (Irish expression). Meaning I know when I'm well off.

I thought THAT was a New York expression.

 

[Irish Rambler]

Maybe you brought over to Waterford Richard !
Glad to hear your safe and well.

 

[CaptSteve53]

Is there a biblical formula in the maritime world in the proportions of rolling chocks in terms of construction to meet beam/length/depth? What determines the construction size of a given set of chocks? I have never read where measurement are included. Just that a boat had rolling chocks installed. Viewing many examples on boats on the hard, they vary in configurations/size.

As happy as I am with the ballast that I have mentioned numerous times on the forum, one wonders if installing a set of chocks would enhance the improved roll motion even more (cost being one consideration).
In speaking with a marine fiberglass repair/construction fellow in Wrangell AK, constructing chocks is a common enough project, in the same class as bulbous bow components , that a couple of days is all it would take to lay up a pair and install. Very tempting. Thoughts?

The only real way to have correct proportional rolling chocks fitted is using a Naval Architect, saying that however some naval architects don’t believe they are very effective at all, or cite roll magnitude reduction of only 10%, but other designers and builders report reduction of 30% to 50%.

Here are some General Considerations how ever:

1) Hard-chine boats and others with high initial stability benefit less from bilge keels/rolling chocks than do round or soft chine hulls, because the harshness of the hard chine edge creates its own turbulence and damping effect.
2) They can be made fairly long—half the length of the boat or more,depending on the curve of the hull. However, they should extend forward only to the point where they start converging due the curve of the bow; any more and they would add drag when underway. Besides, they would be ineffective if they were to come out of the water when the boat pitches.
3) Commonly they are only eight inch eight inches or so in width to avoid extending beyond the “envelope” of the hull, where they could be damaged by a trailer, carriage, or at the dock. If the keel is positioned down at the
turn of the bilge, and is placed perpendicular to the surface of the hull at that point, it can be made longer without extending far enough to attract damage. Some yards put bilge keels as wide as 16 to 18 inches on a 60-foot hull.
4) The trick is to place the keels such that they are within the water flow streamlines of the hull so they produce minimal drag.This can be a problem if the boat operates over a wide range of speeds, as do most semi displacement hulls, because the streamlines change with speed. Some engineers place rolling chocks high on the chines to produce a little lift, and they claim they work best when underway. But the more widely held view seems to be that they should be positioned lower and at a 45° downward angle,which precludes any lift effect. If correctly positioned they work quite well at anchor, and even better underway.
5) There is a drag penalty for chocks, and it’s there whether you need the roll control or not. But the increase in fuel consumption is estimated at less than 10%.
6) The fins should taper at both ends (rather than start and end with sharp corners) and should have a rounded or flat outer edge rather than a knife edge, to avoid damage to and by fishing gear and other obstacles in the water.

Cheers Steve

 

[FF]

Our boat LUCY is a US Navy Utility, that was converted to a lobster supply boat , then to a lobster boat, then to a cruiser to run the Loop and for cruising fun.

It was fitted with roll chocks about 8 inches deep and 30 ft long.

I have not been in the rough with an unmodified Navy Utility so can not compare how effective it is.

The boat still rolls , but there is no harsh check and rapid acceleration as a hard chine would have at the reversal of the roll.

I don't know if it does work , but it seems to have done no harm .

A beam sea is not comfortable but there is no snap roll to create a Vomitorium.

 

[Pgitug]

Don't want the roll?
Get a power cat.

 

[Wxx3]

The only real way to have correct proportional rolling chocks fitted is using a Naval Architect, saying that however some naval architects don’t believe they are very effective at all, or cite roll magnitude reduction of only 10%, but other designers and builders report reduction of 30% to 50%.

Here are some General Considerations how ever:

1) Hard-chine boats and others with high initial stability benefit less from bilge keels/rolling chocks than do round or soft chine hulls, because the harshness of the hard chine edge creates its own turbulence and damping effect.
2) They can be made fairly long—half the length of the boat or more,depending on the curve of the hull. However, they should extend forward only to the point where they start converging due the curve of the bow; any more and they would add drag when underway. Besides, they would be ineffective if they were to come out of the water when the boat pitches.
3) Commonly they are only eight inch eight inches or so in width to avoid extending beyond the “envelope” of the hull, where they could be damaged by a trailer, carriage, or at the dock. If the keel is positioned down at the
turn of the bilge, and is placed perpendicular to the surface of the hull at that point, it can be made longer without extending far enough to attract damage. Some yards put bilge keels as wide as 16 to 18 inches on a 60-foot hull.
4) The trick is to place the keels such that they are within the water flow streamlines of the hull so they produce minimal drag.This can be a problem if the boat operates over a wide range of speeds, as do most semi displacement hulls, because the streamlines change with speed. Some engineers place rolling chocks high on the chines to produce a little lift, and they claim they work best when underway. But the more widely held view seems to be that they should be positioned lower and at a 45° downward angle,which precludes any lift effect. If correctly positioned they work quite well at anchor, and even better underway.
5) There is a drag penalty for chocks, and it’s there whether you need the roll control or not. But the increase in fuel consumption is estimated at less than 10%.
6) The fins should taper at both ends (rather than start and end with sharp corners) and should have a rounded or flat outer edge rather than a knife edge, to avoid damage to and by fishing gear and other obstacles in the water.

Cheers Steve

You basically said everything I was going to say.

While in New Ross, having my bottom done, I did consider adding them. The cost would have been about $2500.

The reasons I ended up deciding not to:
1. I estimated the roll reduction would at most be 10 to 20% on a beam sea. My paravanes would reduce roll 75% on the same beam sea. Therefore the window for me to use them would be relatively small.

2. I estimated that fuel consumption would go up 10%.. Since I used over 2000 gallons in the last two years, that's not an insignificant amount.

3. The final deciding factor, I asked someone at Kadey Krogen. Surprisingly, he informed me that in fact, James Krogen had designed some bilge keels my owners' request.
So when my follow up question was, "Does that mean it was a good idea?"
The response was, "James Krogen did a number of things at owners' request, but had it been a good idea, he would have done it for all the boats"
Nuff said.

 

[FF]

"Don't want the roll?
Get a power cat."

And learn about Multihullers Eyeballs!

FAr far worse in accelerations than even a box underwater.

Think of each hull snapping up 5 rapidly ft as each wave goes under.

 

[Rebel112r]

I have had chocks on the boat for 2 seasons of cruising. Installed cost around 4K. I have not noticed any speed reduction, no increased fuel consumption. They do not cause problems with docking or lifting the boat. They temper the roll, and help with pitch. This is actual observation and not speculation. I have talked to 4 other NP owners that have had them installed and all have had positive things to say about them. There are about 10+ NP's that have had them installed, but I have not talked to all these owners. Added maintenance is about zero, maybe an extra quart of paint every other year. I have crewed on a fish boat with paravanes, which I feel are more effective than the chocks, but there is a lot of highly stressed hardware involved and there definitely is drag, and they do catch crap in the water. Active stabilization or gyro stabilization would be great, but not available for 4K.

 

[Nomad Willy]

A boat that has very rounded cross sections like Dixie II (pics) stabilizers will be very effective and you'd love them. However if you put stabilizers on a wide and flat bottomed boat you may be very disappointed.

The stabilizers need to counteract the tendency for the boat roll. If Dixie was sideways on the face of a wave a little righting moment induced by her stabilizers would keep her from responding to her natural tendency to roll putting her lee rail down toward the wave trough. Very little rolling would take place. If you put stabilizers on a barge almost no reduction in roll would take place. The barge would assume a position on the wave that almost matched the shape of the wave. And as quickly as the wave changed shape. The barge would allow the wave to dictate her rolling position almost entirely .. and almost instantly. The barge would assume her natural position no matter how powerful a stabilizing system would be.

Lots of pleasure boats have hull bottoms that are more like a barge that the fish boat in these pics. So unless your boat resembles Dixie's hull cross section any stabilizer installed will need to work very hard to dampen the roll enough so most are comfortable on board.

I include a pic of my Willard to show that even FD pleasure boats are not round in cross section to the extent that Dixie is. And much of the suitability of boats to stabilizers are a result of length to beam ratio. But most SD trawlers are wide and largely flat too. Stabilizers on a pleasure trawler may work acceptably well and then maybe not.

In the first pic you can see Dixie II roll just from the weight of her extended spar.

 

[Nomad Willy]

"don't want the roll?
Get a power cat."

and learn about multihullers eyeballs!

Far far worse in accelerations than even a box underwater.

Think of each hull snapping up 5 rapidly ft as each wave goes under.

yes .... +1
Similar in some ways to a barge but every boat differs.
A very narrow barge could be controlable (roll wise) and her pronounced hard chines may act much like bilge keels chocks ect.

 

[dannc]

...
I know which side my bread is buttered on ! (Irish expression). Meaning I know when I'm well off.

I thought THAT was a New York expression.

I thought that was a Southern expression!

The more I watch UK and Irish TV programs the more I see how many American sayings are from the home countries. We were watching a British show last weekend and a character said, "I reckon" which I thought was a Southern saying.

Later,
Dan