Ship Equilibrim Angle, Trim and Heel

Discussion in 'Stability' started by AliKaragisi, Nov 11, 2019.

1. Joined: Nov 2019
Posts: 4
Likes: 0, Points: 1
Location: Turkey

AliKaragisiNew Member

hi all,
Firstly, ı need to calculate ship equlibrim status. My program can calculate all hydrostatics data (Volume, Lcb,Tcb, Vcb, Lcf, Tpc, Mtc, Ix,Iy , Wpa etc..) but ı can not calculate equlibrim condition. For example ı have Weight 750 ton, LCG 30 m from AP, TCG 0.02m stb and VCG 4 m from BL. I need to calculate ship equilibrim for this condition. I can calculate Weight and Displacement equilibrim but cannot trim and heel equilibrim. Which method is use for equilibrim.

2. Joined: Oct 2009
Posts: 4,919
Likes: 453, Points: 83, Legacy Rep: 1485
Location: Midcoast Maine

DCockeySenior Member

Are you a student?

If not a student what experience in naval architecture do you have?

3. Joined: Nov 2019
Posts: 4
Likes: 0, Points: 1
Location: Turkey

AliKaragisiNew Member

i m not student , i m working on my loading software. ı have 3 years experince in ship building but i have been working abouth stability.

4. Joined: Sep 2011
Posts: 6,525
Likes: 392, Points: 93, Legacy Rep: 300
Location: Spain

TANSLSenior Member

Calculate hydrostatics for various trim values. With this you will obtain, for the displacement you wish to study, how the longitudinal position of the center of buoyancy varies. When that position coincides with that of the CoG - which logically also changes when the boat is trimmed - you will have reached equilibrium floating.
For the transverse equilibrium position you will have to draw the GZ curves - righting arms - for the desired displacement, define the curve of heeling arms at each angle of heel and calculate the intersection.

5. Joined: Oct 2008
Posts: 6,840
Likes: 795, Points: 113, Legacy Rep: 2488
Location: Japan

This would be calculated by setting the programme to "free trimming" or uncheck the "fixed trim"...depending on how your software programme is set up.

6. Joined: Nov 2019
Posts: 4
Likes: 0, Points: 1
Location: Turkey

AliKaragisiNew Member

not fix trim, ı want to calculate real position of ship.

7. Joined: Nov 2019
Posts: 4
Likes: 0, Points: 1
Location: Turkey

AliKaragisiNew Member

your solution is good but this process is very slow in my software. all hydrostatics (or some trim hydrostatics) calculatingincrease time my equilibrim process..

8. Joined: Oct 2008
Posts: 6,840
Likes: 795, Points: 113, Legacy Rep: 2488
Location: Japan

I know.

Please read very carefully what is written above. What does YOUR programme use....???....it is an either or...perhaps you're not very well versed in the programme, hence your statement?!

This for example..is merely asking to fixed or unfixed...i.e free trimming:

or the other way:

Thus what does YOUR software programme say. There are many ways to sate this...but you're reply suggests you do not understand the terminology or its implications if checked or unchecked?!

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.