KN Calculation

Anybody can help me how to manually calculate/produce KN Values in every Displacement and in every 10 degrees heel increment needed for stability booklet.Thank you.

 

Helo Toy, re u studying IIMS course?

 

Hi Adeyele, planning to make stability booklet.

 

Kindly look into http://gcmshipdesign.com/members.html and post your comments

 

Helo toy, am nt planing to make any1 but I have a exercise relating to your question.
Its exactly as your question.

 

Find GZ first.We know that relation between GZ=KN-KGsin(theta)..GZ=GMsin(theta) .But it is true for angle between 0and 5degree.7degree is maximum.For larger angle of heel,use Barne's method.

 

Normally we use software to calculate KN and we generate GZ curves right? How is the other way working?

 

Atwood's formula.It will take 4 hr to complete one curve.

 

Looking for Manual KN Calculation, kindly post your question in the forum

http://gcmshipdesign.com/members.html

to get the excel sheet

 

Since I use software to calculate KN, forget it

 

You need to:
1. Section your boat
2. Calculate the heave a trim for a given heel angle so that the integral of immerged surface area of the sections gives you the proper volume and LCB
3. Calculate the position of the centre of buoyancy using a barycentre calculation
4. Use trigonometry to find KN
Unlike someone said earlier, you don’t calculate GZ first then KN but the opposite. A stability software always calculate KN first then derives GZ. Remember that KN represent the form stability. Which means that once you have your KN curves you can derive your GZ curve for any VCG you like.

The KN curves isolate the form stability from the mass stability.