hydrostatic in rhino 3

[Ahmed Wahab]

I designed a hull in rhino 3.The WL is 9.8 m,When I check hydrostatic it gives me WL is 13.7 m !!!and I think also the rest of the calculations are wrong.
I deleted the model several times and restarted again But the same result !!
If you have any idea what I'm doing wrong
Regards

[Grant Nelson]

Hi Ahmed, its always handy if you include the file so we can see what your are doing. I assume you are using the hydrostatics command under analyse. I tried it out, and it works fine for me. Perhaps you can check your waterline - by default its the cPlane - if your boat is below the cPlane, then its going to give a waterline length closer to the maximum hull length (and a displacement equal to the entire volume of the hull...
Hope this helps
Grant

[Ahmed Wahab]

I will try to attach the file tonight.But I'm sure the WL is the 0 in the cplan!
Thanks for help

[Ahmed Wahab]

This is the file which is done with rhino 3.
It's just an inial hull to check the hydrostatic.
I would apreciate your comments !
Regards

[Grant Nelson]

After an Xmas dinner, all my blood is in my stomach, and so I can not say exactly why, but if you set the option 'symetric' after you start the hydrostatic command, to Yes, then you boat is 9.8meters... just as we assumed it was. Have a nice holiday period,
Grant

[terhohalme]

Rise the body 0.001 m and hydrostatics will work. If the body has several corners exactly at origin, rhino's hyrdostatics can do errors.

Here are my results after 1 mm rising:
Volume Displacement = 5.15971
Center of Buoyancy = 4.7028, -6.88549e-016, -0.210555
Wetted Surface Area = 18.6501
Waterline Length = 9.79552
Maximum Waterline Beam = 2.2674
Water Plane Area = 15.2934
Center of Floatation = 4.36588, -4.84571e-016,0

Sounds reasonable. RhinoMarine found it similar.

ps. your model had two stems, deleted one.

Terho

[Ahmed Wahab]

Thanks alot !!!!
It works great and I got the same result.

another question please
Is there large deviation sometimes between the hydrostatic in rhino& rhinomarine

regards

[terhohalme]

Rhino's hydrostatics is only for quick checking and can give unexpected results. Rhinomarine modules are for real yacht design work. Look at:

http://www.rhinomarine3d.com/