Probably far from a new idea

[Southern Cross]

The liquid ballast is used only when it comes to maintaining a certain depth or some trim, when the ship carries no load. When the boat is loaded, the ballast is removed. This is the only reason that justifies the liquid ballast. Effectively exist stabilizers devices based on liquid ballast. When used in this way, you need to place special devices (connected vessels, valves, longitudinal bulkheads, to prevent or reduce the free surfaces). When used to get a specific trim or depth, should be avoided ALWAYS the effect of free surfaces. A fixed ballast weight should NEVER be done with liquids. It is nonsense because with much less volume, about 7 times less, a solid ballast has the same effect.
An internal solid ballast can be controversial, since its conditions can adversely affect the stability of a ship. You have to make the move the ballast towards port side when the ship heeling to starboard and vice versa. It is not easy and, of course, impractical.

I got a little lost there. Why is a proven external solid canting ballast system more practical than an internal one using the same mechanism?

 

[TANSL]

Articulated keels only use a hinge at its base, and stoppers to control their movement. They are complicated elements, I do not know in detail, but that, I believe, are simpler than the apparatus for controlling the internal ballast.
I hope the attached figure clarify something

 

[Southern Cross]

Unless I'm wrong and I am usually, if you take that pivot point and move it up to under the deck and shorten the arm to swing the radius of the hull, isn't it kind of the same?

 

[TANSL]

Whenever you do not use liquid ballast I'll agree with you. The effect is the same, actually, but we have to calculate if the righting arms are the same or not. There therefore appear at one of the two systems will need more weight than another.
For other reasons the boat need to have a keel. So why not use it to carry the ballast?.

 

[Southern Cross]

Ok. I thought we previously established it may not need a keel. The big problem is turning it back over if it capsized.

 

[gonzo]

TANSL: movable liquid ballast on sailboats has been used for decades. There are tanks as far outboard as possible under the deck. The water can be moved from side to side by gravity or pumps. Gravity is used to drain the windward tanks into the leeward ones before tacking. There are sometimes trim tanks installed also. This is a link where you can learn some of the typical applications: http://www.vgyd.com/Waterballast.html

Internal ballast has been used for centuries with proven results too.

 

[Southern Cross]

Articulated keels only use a hinge at its base, and stoppers to control their movement. They are complicated elements, I do not know in detail, but that, I believe, are simpler than the apparatus for controlling the internal ballast.
I hope the attached figure clarify something

Sorry, I couldn't see your drawing too clearly on my phone earlier.

I agree, I think an internal ballast coupled with an external one would not only be redundant but also dangerous.

 

[DCockey]

Ok. I thought we previously established it may not need a keel. The big problem is turning it back over if it capsized.

When was that established? Without a keel what will be used to provide "lateral resistance" so that the boat can go to windward?

 

[Southern Cross]

When was that established? Without a keel what will be used to provide "lateral resistance" so that the boat can go to windward?

Dagger boards. Similar in the way Speed Dream Moves forward when the keel is completely out of the water. Lateral resistance comes from hull shape and foils. It was mentioned earlier.

 

[michael pierzga]

The advantage of a swing keel is that you develop the maximum righting moment with the minimum ballast. If you removed the swing keel bulb ballast and went with movable ballast inside the boat, you would need a lot more kgs and would suffer with a very heavy boat fitted with an internal guillotine.

Moveable Water ballast and a fixed keel are the best way to go if you decide a swing keel is unworkable for your design.

 

[kerosene]

The weight could travel on rails driven by cable mechansim. This way the ballast case woul be much smaller as no space would be needed for the swinging arm. Also the path could be "any" smooth shape.

Still I think the limited moment arm is the key problem.

 

[Southern Cross]

The weight could travel on rails driven by cable mechansim. This way the ballast case woul be much smaller as no space would be needed for the swinging arm. Also the path could be "any" smooth shape.

Still I think the limited moment arm is the key problem.

Yes. I was originally thinking rails with hydraulics. But a cable system is practical. The cables could run up through the deck and back to a grinder for the crew. If the pendulum swung easily enough, you might even be able to tack relatively quickly with this thing.

I guess with all new designs there are positive and negative aspects to it that you can either work through or the idea dies out.

The obvious huge disadvantage is righting moment. But where there is a will ...

I was reading elsewhere that a breakaway mast might be a solution. But I don't like it. I can imagine that thing swinging around in seas and puncturing a hole in the hull. Even still, without a mast, there may not be enough righting moment. The math is beyond me.

If you used a deck stepped mast the position of the ballast could be played with in the design. Shrouds and chains plates could also be attached to this structure.

The guillotine question can be resolved by having redundant safety features, the cable initially and then a pin or brake on the rails like a roller coaster. No big deal.

The issue of dividing the boat is valid especially for cruising and aesthetics. But for racing? Speed over creature comfort. Also, access to the forward part of the boat could be easily made when the pendulum is on center or on either tack, through watertight hatches.

Another thought. The Ballast Box as I am coining it, would be an integral part of the boats structure, housed between two structural bulkheads. Built as a stand alone component in carbon , it could be glassed into the hull and glassed to the deck. (Do you say glassed in? Is that what they do with carbon hulls ?)

One advantage over water ballast is that it takes some time to fill the tanks making short tacking unlikely. One disadvantage with the Ballast Box is that it's a permanent ballast. It can't be jettisoned in light air. But if this ballast is figured into the overall boats displacement it might not matter.

Setting the righting moment aside for the moment I'm still curious what length and what sail plan the boat would need with 2000lbs ballast? Visualizing in my head would help me with the rest.

Thanks in advance.

 

[michael pierzga]

Your ballast system has already been done. look in Seahorse Mag, past issues, or do some googling

 

[Southern Cross]

Your ballast system has already been done. look in Seahorse Mag, past issues, or do some googling

Link?

 

[Southern Cross]

Would there be any advantage to dagger boards that could turn changing the angle of attack, doubling, say, as a steering mechanism? One placed forward and the other aft.

The dagger board could slide into a chamber that is fixed through the deck angled to be vertical when the boat is at optimum heel, like the daggers on the IMOCA, only they could turn through 40 degrees more or less?