# stability of elliptical hull

Discussion in 'Stability' started by hbr, May 15, 2009.

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### hbrJunior Member

Based on the assumptions and calculation in the attached pdf, want to have some feedback, review comments on the assumtions of a hull that is based on a half ellipse below the waterline and a triangle deck form.
first variant has a triangle keel ( waterline at the stern and draft at the bow)
second variant has a semi circle as keel ( with both the keel and stern at waterline level)

Are the results reasonable ?

on the one hand for the second variant of hull, what freeboard needs to be foreseen in order to be sure that from lateral point of view the hull is stable ?

on the other hand, how can the stability be calculated at different levels of heeling (also in excel) ?

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2. ### Guest625101138Previous Member

Just to be sure I have what you have in mind. Does the attached image represent the hull you have modelled?

If it is then you would need to have the CofG 2cm BELOW the water level to keep it upright. This is not particularly stable.

Rick W

#### Attached Files:

• ###### Triangle_Hull.jpg
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hbr

Am i missing something..since your Q is.."...how can the stability be calculated at different levels of heeling ..", since the A is, same as another hull form.
So begs the questions. Have you done a stability analysis/report before?

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### hbrJunior Member

curve of static stability

Hello,

want to understand the curve of statical stability.
need the righting lever for differnt levels of heel for an elliptical hull form

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### hbrJunior Member

Rick,

the draw is in line with the first hull.

Yes the area distribution is not balanced and that is directly linked with the triangular deck form.

will need an alternative hull form in order to become a balanced area distribution

post the correction asap.

calculate the Cy distance below the waterline based on the 4*Y/(3*3,14) for each half hull section

#### Attached Files:

• ###### ellips math and hull estimation area distribution.pdf
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### PARYacht Designer/Builder

What, pray tell, is the logic behind this contrivance? Clearly efficiency and stability aren't high on the priority list.

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