# FreeShip Hydrostatics and Cross Curves

Discussion in 'Stability' started by terrnz, Jun 11, 2017.

1. Joined: Mar 2014
Posts: 67
Likes: 0, Points: 6, Legacy Rep: 10
Location: NZ

### terrnzJunior Member

Any users?
It could be my concept or my maths.
The Cross curves function in calculations gives KNsin values

Does not

KNsin = GZ

therefore
KNsin-KGsin=RM ?

where KG is centre of gravity?

I am using this as a design tool evaluating a concept/design brief.
It does not need to be accurate to the nth degree +/- 5% would be fine.

Any practical help would be appreciated.

2. Joined: Sep 2011
Posts: 7,008
Likes: 563, Points: 123, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

In any hydrostatic program the user must manually enter the value of the KG because the software, although it could make an estimate, could also be very wrong.

3. Joined: Mar 2014
Posts: 67
Likes: 0, Points: 6, Legacy Rep: 10
Location: NZ

### terrnzJunior Member

So if we are talking 1 degree, ie RM1 KNsin1*m= RM1 is a rough guide

where m = displacement

so m=4200kg
KNsin1=.035

RM1=147KgM

then if we use the Nordic approximation RM30=29*RM1
we can use a figure of 147*29=4263KgM for emphirical rig dimensioning

4. Joined: Sep 2011
Posts: 7,008
Likes: 563, Points: 123, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

According to this formula, the KN value is 2.005
Although perhaps "sin1" means sine of one radian. In that case, KN = 0.04159
In any case how did you calculate the value of KN?
See attached file, please.

#### Attached Files:

• ###### Stab mLDC.pdf
File size:
107.4 KB
Views:
455
Last edited: Jun 11, 2017
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.