Weather Criterion

Can anyone help me to solving my problem...

 

The solution is to make some of this huge superstructure weathertight -i.e. able to keep water out when submerged shortly due to roll motion. Then you will have huge volume to help in high angle stability. Your stability range will be not ~30 degrees, but 60 or even 90... .
For stability calculations, all the airpipes, portlights, shell doors are considered as CLOSED, and are specified for the builders as weathertight. Otherwise no ship would comply with stability requirements.

 

hm...:idea:

So in other words, some of huge superstructure can be included in calculation?
Because my knowledge says that for calculation of stability, just main hull included (just until main deck/ continues deck).

I'll try to change my model in maxsurf,
thanks perm, i waiting for your reply...

Thanks a lot...

 

Yes superstructures can be included in stability calculations, PROVIDED they comply to certain requirements for strength, closures of openings, etc.. In simple words, Classification Society want to be sure, that in no circumstances the volume of superstructures, included in stability calculations, will be possibly flooded trough open porthole, ventilation inlet/outlet grid, smashed door, smashed window, etc., etc..

 

When you says : "Area 1" should be greater than "Area 2" : these areas are areas calculated under the GZ curve. It is not the lateral plane area of the vessel.

 

Ok perm, all of your opinion has been noted. Thanks a lot Perm...

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thanks for your response booba,
Yes, I'm agree with you that "Area 1" should be greater than "Area 2" are areas calculated under the GZ curve and It is not the lateral plane area of the vessel.
But my knowledge says that these areas depends on Wind Heeling Lever.
Wind Heeling Lever depends on displacement, centroid height of lateral area above and below water line, lateral area and wind pressure, that's why, me and Perm discussing about lateral area (my ferry has so wide of lateral area).
Maybe you have any suggestion for my case please ?

thanks for your reply..

 

Is your "k" coef. for windward heeling angle = 0.7 ?

 

for right now, i used 1 for windward heeling angle coef. ...
How?

 

you can decrease the windward rolling angle (and thus the area) if k=0.7 (using bilge keels for example if you have a round bilge hull). It may have an important effect.

 

Thanks booba
Here i use Hydromax to calculate the stability.
Please see the attachment file,
is "k" coef. same with constant "a" in hydromax criteria (see the attachment)?

 

I do not know this software. All details on the calculations are in the IMO : "Code on Intact Stability (IS), 2009 Edition"

you can purchase it on : http://www.imo.org/Publications/Pages/JustPublished2010.aspx

regards.

 

Ok Booba,
Thanks for your information...

 

Weather criteria is always difficult to pass for certain design (it's why the criteria exists!).

Your windage area is maybe too large or , as said in previous messages, your CoG is expected too high ?

If you don't pass the weather criteria => your GZ curve is not "strong" enough to counteract inclining moment modelled by the weather criteria. Then no option => reduce your windage area and/or improve your GM !


François-Xavier Nettersheim

 

thanks for your answer nettersheim,
noted.

But, that's my problem, my boss said that i can't change the design of his vessel..
Haha..

 

How far up did you made your superstructures weathertight?
What modifications your boss do not want to accept?
_______________________
Sh*t happens: sometimes design brief requirements are inconsistent, i.e. impossible to fulfill at current stage of technology or within price restrictions.