Easy way to reduce rolling on bilge-keeler?

[Richard Reed]

Given that much of the keel is hidden in the shadow of both keels, its area to damp rolling is somewhat reduced. More keel is not always good, I sailed on a Colin Archer long keeler that would almost dip both rails when a wave swell would sweep through, yet on a narrow fin and rudder lightweight boat, there was nothing under the water for the wave energy to have much impact on.

I think your rolling is more to do with the hull shape rather than lack of keel area. I had the same trim issues swapping out an old Lister for a Yanmar. I purchased scarp lead pipes that i beat flat and laid them in a cement slurry.

Good point about an extra keel not making much difference between the two bilge plates. As you say, that rounded bottom is the culprit. I think if I add anything it will be a mini bilge plate on each side, as others have suggested, but I'll add some more ballast first and see how this season goes. I've been buying up rolls of roofing lead and squashing them into underfloor compartments.

 

[Herreshock]

Given that much of the keel is hidden in the shadow of both keels, its area to damp rolling is somewhat reduced. More keel is not always good, I sailed on a Colin Archer long keeler that would almost dip both rails when a wave swell would sweep through, yet on a narrow fin and rudder lightweight boat, there was nothing under the water for the wave energy to have much impact on.

I think your rolling is more to do with the hull shape rather than lack of keel area. I had the same trim issues swapping out an old Lister for a Yanmar. I purchased scarp lead pipes that i beat flat and laid them in a cement slurry.

A full keel will receive the wave impact thats why it will roll while any keel, and mostly these high aspect ratio keels will create a pendular momentum and thats why boats start to roll several times after the wave has passed and a big mast will exacerbate it too.

Otherwise if the boat has wind on anchor area it will roll less because the wind trim the mast, at least with smaller waves but not with a swell switching wing direction and keeping the waves to the shore

A extra central fin will damp the boat, any short fin will do it and without ballast, otherwise instead active fins stabilisers two hinged fins can be tweaked by using cables and pulleys doing the same movement as active fins with the rolling movements

 

[skaraborgcraft]

I think if I add anything it will be a mini bilge plate on each side, as others have suggested, but I'll add some more ballast first and see how this season goes.

Adding bilge plates may help, but you are also adding a significant amount of extra wetted surface or drag.

You could put a foam and glass keel fore and aft of the bilge keels on the centreline. Anything that will force the water to change direction of waterflow around the hull will help dampen roll, given your hull shape. Having extra ballast and more hull in the water is a good first trail.

 

[gonzo]

Here comes the paper of the arquime-freudian theories.... These wide beam sailboats roll like crazy, all pogos, hanses, etc with whatever the size of the waves that arrive they start a violent pendular momentum, and both cases are different

-pogo with big span mast and keel and ultra-wide beam with stern lateral overhangs even if having low freeboard

-hanses with medium-high freeboard and with wide beam stern lateral overhangs at considerable height, basically an inverted wide piramid which is the most unstable shape

There's some cases in an anchorage where a boat rolls more and probably related to the coast refraction , always there's a "sweet spot" where sailboats roll more than the rest

In the case of these IOR yachts the high freeboard (related to length and beam) makes the cabin height

IOR boats had moderate to low freeboard to beam ratio. However you contradict your statement previously: "even if having low freeboard".
Refraction is a property of materials and light which does not make any boat roll.
arquime-freudian theories asside, sometimes a bowsprit is just a bowsprit to paraphrase the Austrian.

 

[gonzo]

A full keel will receive the wave impact thats why it will roll while any keel, and mostly these high aspect ratio keels will create a pendular momentum and thats why boats start to roll several times after the wave has passed and a big mast will exacerbate it too.

That is exactly the opposite. They actuall dampen the roll more.

 

[Herreshock]

IOR boats had moderate to low freeboard to beam ratio. However you contradict your statement previously: "even if having low freeboard".
Refraction is a property of materials and light which does not make any boat roll.
arquime-freudian theories asside, sometimes a bowsprit is just a bowsprit to paraphrase the Austrian.

Yes you tell me while i have slept in a IOR yacht for years while anchored ...

 

[Herreshock]

That is exactly the opposite. They actuall dampen the roll more.

Yes damping...you seem to have forgotten how a pendulum works...

The bulb keel ballast will damp it eventually but in the meantime it creates a pendular feedback with the wave fridenfrodamedes

 

[gonzo]

it creates a pendular feedback with the wave fridenfrodamedes

Is that a Freudian slip? Get real and stay on track with the thread.

 

[CT249]

Putting those together it seems that Herrochocker may have slept on a high-freeboard high-cabin IOR boat with a bulb keel.

I wonder what the heck it was? Bulb keels were extremely rare on IOR boats due to the CGF factor and other matters.

 

[Herreshock]

Putting those together it seems that Herrochocker may have slept on a high-freeboard high-cabin IOR boat with a bulb keel.

I wonder what the heck it was? Bulb keels were extremely rare on IOR boats due to the CGF factor and other matters.

Symphonie 32, I forgot to mention that it's from 10m to 7m where there's more height disproportion in some of these 80s boats

Fin keels create pendular feedback too while full keels can damp the pendular movement because the shape besides ballast but unfortunately they also are more affected by the passing wave

 

[Herreshock]

Is that a Freudian slip? Get real and stay on track with the thread.

I couldn't be more arqfrodo on topic now

 

[Ad Hoc]

Yes damping...you seem to have forgotten how a pendulum works...

And what has a pendulum got to do with damping?

...The bulb keel ballast ...

And explain how a blob of solid ballast will dampen the amplitude?

 

[Herreshock]

And what has a pendulum got to do with damping?



And explain how a blob of solid ballast will dampen the amplitude?

Forget about those "amplitude" terms, this reminds me of loudspeaker design superfluous talk

Any wave will roll the keel boat and create a pendular feedback that is finally corrected by the ballast and hull hydrodynamic damping

 

[Ad Hoc]

Forget about those "amplitude" terms, this reminds me of loudspeaker design superfluous talk

Any wave will roll the keel boat and create a pendular feedback that is finally corrected by the ballast and hull hydrodynamic damping

Hmmm....that's a no then, you don't understand....

 

[Herreshock]

Hmmm....that's a no then, you don't understand....

Yes i understand speaker design and sound wave amplitude more than the average audio sick consumer but in the end anything will do pour some sound

Wave amplitude is more important in sailing for crossing swells and the conditions and waves they create and coastal wave refraction too to avoid during anchoring