calculating GZ

Can someone please explain to me the steps that are required to calculate GZ. I'm trying to produce a righting arm curve to see if my class project is stable at angles 0-80 degrees.

Thanks

 

First...

Do you know how to calculate B, G, Envelope Volume, Tank volumes, Iwp, I transvers tank, KG, KB, and BM for any arbitrary waterplane, tank condition, and angle of heel? Otherwise what I will tell you won't make much sense.

 

For convetional shapes , its a lengthy process. We need to find equilibrium water plane for each angle of inclination and corresponding water plane area,Moment of Inertia & Volume of displacement. Then follow the basic equations ( BM=Transverse Moment of inertia of water plane / Volume of displacement.KM = KB+BM, KN = KM X Sin(Heel angle), GZ=KN-KG sin(theta) etc) to obtain GZ for particular loading condition / draft.

PNACS@hotmail.com

 

PNACS,

I have all the values that I need except KN. I'm not sure what the X value is in the formula KN=KM X Sin(theta).
I'm using GHS for the first time so I'm learning the capabilities of the program. Is there a command that will give me the GZ values in GHS.

Thanks

 

First tell me, Have you made vessel hull model in GHS?

 

Yes
I have imported the rhino model into GHS. I also have added tanks and a skeg using the part marker in GHS.

Thanks

 

Once model is defined, Obtaining GZ for a particular draft / loading condition is simple.

start GHS, then read the model using command - read <model file name>

If u need to find GZ at a particular draft, say 3.0 meter and KG=5 meters.

draft = 3.0
VCG= 5 meters
solve weight
RA 0,10,20,30,40,50,60,70,80

Above will give you RA (GZ) at specified draft and heel angles.

Similarly if you set weight add centroids for a particular condition, u can obtain GZ for the case.
Say, Total weight of the vessel is 500, LCG=15.0, TCG=0, VCG=5.0

weight 500,15.0,0,5.0
Solve
RA 0,10,20,30,40,50,60,70,80

Will ve you GZ values.


Read GZ user Reference manual for details