# Calculating KG

Discussion in 'Stability' started by ed198, Sep 24, 2018.

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### TANSLSenior Member

... so you can use the formula in post #4.

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### ed198Junior Member

Ok thanks ...what does KC refer to pls?

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### TANSLSenior Member

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### ed198Junior Member

Ah ok don't have that...

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### TANSLSenior Member

What is really what you have, inclining experience data, calculations, drawings, etc ... of your boat?

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### ed198Junior Member

I have the drawings on Rhino however only trial version ...and as mentioned Gm calculation from the inclination experiment...

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### TANSLSenior Member

To calculate the GM at a certain displacement and trim you need to have performed the calculations of the hydrostatic values. One of the values obtained in these calculations is the KC value. Do you have any calculation or how have you come to deduct the value of the GM?

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### ed198Junior Member

If you can't help no problem...as far as i know you can calculate GM from the inclining experiment which i did

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### TANSLSenior Member

Yes, I can and I want to help and that is what I am trying to do from post # 4 ..
Trying, no doubt about it, to help, I'll tell you that if you already have the GM, you just need to calculate the Rmt and the KC (see formula in post # 4). To obtain these two values it is enough that you look at the hydrostatic values (which I suppose you have already calculated).
It would be of great help, for someone to help you, to tell us how you have made the experience of stability and the data you have obtained from it: draught at fore and after perpendiculars, length of the pendulum, average angle of heel, weights transferred, distance of translation of the weights, main characteristics of the shipboat, body lines plan, hydrostatic values ....

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### tlouth7Junior Member

It sounds like you have a 3D model of the boat? In that case you could find the centre of buoyancy in CAD. The easiest way is to create a solid of the underwater hull (check this has the same displacement as you found by weighing the boat). The centre of mass of this solid is the centre of buoyancy.

You can then use TANSL's formula

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### jehardimanSenior Member

Tansl is correct, you can calculate GM without knowing KC (called KB here in the USA) or KG. You really need the curves of form to get KG from the GM. See the following post ( and ignore the snark)… Calculation of GM https://www.boatdesign.net/threads/calculation-of-gm.8852/#post-60405

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