# Sail Area vs Keel Area - Stability Calculation

Discussion in 'Hydrodynamics and Aerodynamics' started by Dabrownone, May 28, 2012.

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### DCockeySenior Member

More than that.

Either the relative sizes and shapes fo the sail rig and hull would have to be such that the a force on the keel that matches the force of the wind on the rig/sails and the heeling moment of the force from the current on the keel matches the heeling moment of the force of the wind on the rig/sails
- or -
The boat would have to be constrained so that it could not move sideways but could pivot and the heeling moment of the force from the current on the keel matches the heeling moment of the force of the wind on the rig/sails.

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### HakimKlunkerAndreas der Juengere

Who wants a boat like that?
I call this a case of mathematical diarrhoea

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### BobBillSenior Member

Dab, I thank you for your inquiry, and the others for contributions, as I learned.

But, Dabrownone, if static, a waste of time, to me, or, as one noted, self-abuse...real world...learn from these boyos.

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### BobBillSenior Member

Very kewl link, very kewl, Daq. Thanks.

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### dougfrolichSenior Member

I would recomend reading Areo-Hydrodynamics and the Performance of Sailing Yachts
by Fabio Fossati
In section- 6.4 Equilibrium under sail - estimating the surface area of hull appendages
is a very nice article that goes back to the "spirit" of the origonal post.
My \$.02 worth.

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6. ### Paul BPrevious Member

Not really.

That section is more like the "spirit" of the diagram daiquiri has posted.

The OP is intent on proving that a large enough surface area under the waterline will somehow stop a boat from heeling.

These are two very different things.

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### TeddyDiverGollywobbler

And the reality makes it just opposite way.. more keel area, more heeling, less lateral area (no keel) less heeling

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### PetrosSenior Member

That just shows why mathamatitions working in any other field need to be supervised by people in that field.

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### dougfrolichSenior Member

In the "spirit" meaning here is a fine preliminary math model for first estimates.
Can we be more pedantic?

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### BobBillSenior Member

Why would ya? Seems to be pointless enterprise to begin with. No offense intended, but not practical, therefore pedantic, perhaps? Still, my numb head picked up some needed material via the out takes, regarding major sail plan change...

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### RBauerNew Member

I need help to determine the weighted needed in the keel for my RC model of this Wianno Senior. It is a scratch build 1”= 1’

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### DCockeySenior Member

Do you want you model to float on the same waterline as the full size boat? If so the total weight of the model to be scaled appropriately from the total weight of the full size boat. The total weights to be scaled as the dimensional scale ratio cubed. So for a model built to a scale of 1" = 1' or a dimensional scale ratio of 1/12 the weight of the model needs to be 1/1728 of the weight of the boat.

My understanding is scale model boats intended for sailing frequently have keels which are deeper than the original boats keel.

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### HowlandwoodworksJohn Howland

If you were to Heave-To you would create a similar scenario but from a different set of circumstances. Sail configuration and angle of attack could create the stall over the keel you are looking for without creating a Frankenstein boat.

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