# Innovative method of increasing stability of the yacht

Discussion in 'Boat Design' started by BTG YACHT DSGN, Oct 31, 2008.

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### BTG YACHT DSGN-sailing is believing-

Last month I was thinking very hardly about: How to increase sailing boat's stability without putting another tons of lead into the bulb?

So I went back to the theory and started to analyze how accually sailing boat produces the righthing moment and what forces are acting on her when sailing (so the stability).

I completely understand that you know al these basics (for sure better than me), but for my considerations here it would be helpful to the forces acting ona sailing boat at x heel angle. So we have the aerodynamic side force that can be divided into heeling force acting x degrees under aero side force and force acting downwards which pulls the hull farer into the water. Other forces are: buoancy (acts upwards, has begining in center of buoancy) and weight force (acting downwards, has begining in center of gravity) the lever that is created when x heel occurs creates a moment of forces that tries (good if he does!) to upright the yacht, heeled by the aero force from the rig. So the arm of the gravity to buoancy force multiplied by the value of the gravity foce must be equal to the arm beetween buoancy and aero force multiplied by value of the aero force to keep the boat in equilibrium.

uff... that's the theory (if any errors occur please tell me!!!)

Now my idea is to put at the top of the mast highly eficient wing that will produce lift force in direction parallel to the mast and. Let's go back to the theory (only for a second, don't worry =) ) to see what happens now.

The "wing" is now producing relatively small force but on a much longer (twice?) lever than the aerodynamic force. Wing force creates together with the aero force a lever that works quite similar as forces acting when lifting a wheelbarrow- we can lift by hands quite large weights on a wheelbarrow, because the arm at which our hands "work" is quite big. The same situation happens using the "wing"- it creates a lever that helps boat to upright, and allows us to use smaller ballast weight. Why the wing doesn't seem to be as stupid solution as you might have thought =)?

+
- it allows to reduce the weight of the ballast, which is very desired in ANY boat

- The "wing" can be quite small because of the fact that it works on a higher arm

- It don't make too much aero drag...- because it can be small, it produces the higher the force the higher the wind speed ( so the higher righting moment boat requires)

but.......

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-I haven't found yet how exactly can be manufactured the "wing" ie the most problems will be with: constructing multi axial steering system so that wing can adjust to to heeling angle and apparent wind angle

- It would be good to stiffen (even a little bit) the mast -that weighs (ah, I'd forgotten about this- the goal is that the "wing" SHALL BEAS LIGHT AS POSSIBLE!!!)

I'm very interested in your opinion about the "wing", can you see any practical applicatin for this solution, and maybe some thoughts of evaluation this idea. Do you know of any similar solutions that were evaluated in history of boat design (I assume that if such wasn't quoted in Marchaj than it don't exist )? I'm opened for any kind of cooperation in evaluation of this project

Regards

Jakub Batog BTG YACHT DESIGN studio.btg@gmail.com

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### TcubedBoat Designer

This has been explored in differing forms already. The problem with the approach you've outlined is that it would have a very high drag cost. The drag is actually due to the total resultant aerodynamic force vector of the upper stabilising sail. And that is going at close angles to the wind, as soon as the wind comes more from the side it becomes almost impossible. There are other better forms of reducing/eliminating the heeling force, but they have certain problems as well.

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### TeddyDiverGollywobbler

Turning it around with a similar wing in the tip of the keel could be more efficient?

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### NordicFolkboatJunior Member

Exactly. An extra rudder on the keel would provide lots of righting moment, a bit like the stabilizing fins you may find on larger boats. You could use a servo and a gyroscope and a lot of electronics, but it's probably better to make a passive system. Maybe a damped pendulum controlling a smaller servo rudder at the end of the righting rudder on the keel?

I had this idea myself some time ago, but I pretty much abandoned it because of complexity and drag penalty. But it would be cool to see this tried out.

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### BTG YACHT DSGN-sailing is believing-

Yes, all of you guys make a good point. I appreciate your interest about the project . TeddyDiver suggested to add a wing instead of on a mast- on a keel. I'll try to consider this solution:

So on the one hand the one hand the wing placed on a keel can be smaller compared to the wing on a mast (due to higher density of the fluid it work in), but on the other hand the wing has to be bigger to produce as much MOMENT as the mast wing, because the arm of this force is smaller. So bigger wing in water brings lots of drag. The biggest advantage with the "wing" is that it works on a BIG ARM

And to make it as light as possible- maybe it's a good idea to manufacture it from a nylon/spinnaker cloth, stiffened by high-modulus carbon rods.

And the multi axial adjustment can be placed in the hull, and kind of chain will be running through the mast to pass the rotation force of electric engines (that can be located near the center of gravity)

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### TeddyDiverGollywobbler

Just a though..
As a "top" related solution better than a wing might be a "double" wind turbines. Lower turbine working as a motor giving the thrust to the top turbine uprighting the boat.

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### BTG YACHT DSGN-sailing is believing-

yes... that's interesting ... can you explain some more details of how that turbine might work?

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### BTG YACHT DSGN-sailing is believing-

I'm worry if there wont be any interference of the turbine and shrouds???
Because I understand that you suggest to make a "helicopter" at the top of the mast?

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### BTG YACHT DSGN-sailing is believing-

Also turbines (rotating parts) are more complicated parts than a wing, so they would more likely damage

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### BTG YACHT DSGN-sailing is believing-

Any suggestions of evaluation?

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### kach22iArchitect

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### TeddyDiverGollywobbler

Imagine on a tack power pushing short lever (lower turbine) leeway pushes the mast head long lever (upper trb) to the opposite direction. No work (well allmost none) done against the fw movement..

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### BTG YACHT DSGN-sailing is believing-

yes, that mignt be a kind of solution... thanks for that I'll take that under consideration.
So the aero wing at the top of the mast has been officially proven to fail? The only solution would be those turnines? As I said before- turbines might be more complicated than a single wing, I think...
Now let's try to consider a solution when the wing will be controlled by the crew/rc winch by lines attached to the endings. Then it would work rudder like a paraglide, but wouldn't it be too much complicated- long lines along the mast...hmm...that might be a problem aspeccially in strong winds, when wind pressure ''bends" the lines...
So what solution do you propose for an idea of controlling it as multiaxial adjustment wing? Ropes running through the mast combined with an electric engine inside the hull as low as possible in order to lower the center of the gravity?

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### PetrosSenior Member

There are problems with each of these ideas.

Putting a small wing on the top of the sail means you will be generating lift in the opposite direction that your mail sail is, so you would be fighting against the forward thrust you need move the boat, and at the top, likely messing up the airflow over the upper part of the mainsail/jib. It might be possible there is a small advantage since the center of lift on the small wing would be higher (better lever arm), than the center of lift of the main sail. But the extra drag, weight that high on the mast, and complexity means any real advantage would likely be minimal.

The adjustable trim tab on the keel has more promise, but unless the keel is very deep there would be a large induced drag penalty since you would need a fairly large adjustable surface with a short lever arm. A high aspect ratio wing like keel with a trim tab down at the bottom would be the best bet, but it too would be counter to the force your keel is generating to counter the sails lateral force.

A wind turbine near the deck driving a fan at the top of the mast is just too complex to consider. You would have losses at the each of these device, add weight and complexity, and drag (there is cost in terms of drag to extract energy out of the air stream), and if the trubines injested a sheet or halyard, you could be in trouble real fast, not to mention damage to the rigging.

The best approach is also the simplest, use a wide beam, deep weighted keel (even one that allows it to swing side to side), and keep the rig clean and used stream lined mast to reduce drag on the rigging and sails, and you can get more thrust from the sail with less heeling moment.

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