Inclining Experiment

Discussion in 'Boat Design' started by mbhanoo, Apr 2, 2009.

1. Joined: Apr 2009
Posts: 13
Likes: 0, Points: 0, Legacy Rep: 10
Location: INDIA

mbhanooJunior Member

Hello Everybody,

In the inclining experiment calculations, why free surface effect is added to the GM value. Since the value is too small, instead of neglecting it, why it is added to the GM. Please clarify.

2. Joined: Oct 2008
Posts: 6,166
Likes: 399, Points: 83, Legacy Rep: 2488
Location: Japan

You've written that slightly incorrect.

GZ =GMsin(angle), so for small angles the shift of centre of gravity from the free surface is ineffect to "raise" the CoG. This rise in CoG creates the loss of GM, when you draw out the geometery of vectors.

3. Joined: Apr 2009
Posts: 13
Likes: 0, Points: 0, Legacy Rep: 10
Location: INDIA

mbhanooJunior Member

Yes sir, I fully agree with you. For small angles of heel, there will be negligible raise in KG hence no loss in GM. But I have seen in so many inclining reports, free surface correction GG0 is added to the GM value, even if it is too small. I request you to clarify that.

4. Joined: Oct 2008
Posts: 6,166
Likes: 399, Points: 83, Legacy Rep: 2488
Location: Japan

mbhanoo

You misunderstand me. The formula and procedure IS for small angles and there IS an effective rise in CoG, for small angles, hence the reduction. So you're incorrect in assuming a "negligible raise in KG".

For large angles the reduction is:

(density -liquid/density-sea) x Inetria of tank/ Volume of ship

see attached.

Attached Files:

• free surface.pdf
File size:
27.6 KB
Views:
331
5. Joined: Feb 2018
Posts: 4
Likes: 0, Points: 1
Location: Cochin

Syam KrishnanNew Member

Hi,
Please use XShip Inclining App available on the below link to make calculations easy. It will calculate all the parameters for you and give results and GM values and it's totally FREE...!!
http://apps.xship.in/Inclining/

XShip products - visit www.xship.in

6. Joined: Feb 2018
Posts: 4
Likes: 0, Points: 1
Location: Cochin

Syam KrishnanNew Member

Hi,

Please use XShip Inclining App available on the below link to make calculations easy. It will calculate all the parameters for you and give results and GM values and it's totally FREE...!!
http://apps.xship.in/Inclining/