# How to find hydrodynamic lift from lift coefficient vessel? on planing

Discussion in 'Hydrodynamics and Aerodynamics' started by alfieb, Apr 18, 2011.

1. Joined: Apr 2011
Posts: 3
Likes: 1, Points: 0, Legacy Rep: 13
Location: select

### alfiebNew Member

Hi! I'm using savitsky's method to find the equilibrium trim angle for a vessel and was wondering how I can calculate the hydrodynamic lift generated? I already have the lift coefficient.

Thanks for any help!

2. Joined: Oct 2009
Posts: 5,030
Likes: 515, Points: 113, Legacy Rep: 1485
Location: Midcoast Maine

### DCockeySenior Member

How is the lift coefficient defined? What reference(s) are you using for Savitsky's method?

3. Joined: Apr 2011
Posts: 3
Likes: 1, Points: 0, Legacy Rep: 13
Location: select

### alfiebNew Member

Lift coefficient = Δ/((ro/2)*V^2*b^2). From Savitsky's '64 paper.

1 person likes this.
4. Joined: Oct 2009
Posts: 5,030
Likes: 515, Points: 113, Legacy Rep: 1485
Location: Midcoast Maine

### DCockeySenior Member

Re-arranging that formula results in:
Δ = Lift coefficient*((ro/2)*V^2*b^2)

2 people like this.
5. Joined: Apr 2011
Posts: 3
Likes: 1, Points: 0, Legacy Rep: 13
Location: select

### alfiebNew Member

Ah ok, I thought Δ was equal to the weight of the vessel. But it is in fact the lift?

6. Joined: Oct 2009
Posts: 5,030
Likes: 515, Points: 113, Legacy Rep: 1485
Location: Midcoast Maine

### DCockeySenior Member

Only if lift equals displacement. Is that consistent with Savitsky's assumptions?

1 person likes this.
7. Joined: May 2004
Posts: 5,373
Likes: 254, Points: 93, Legacy Rep: 3380
Location: Italy (Garda Lake) and Croatia (Istria)

### daiquiriEngineering and Design

Delta in the Savitsky formula is the vertical component of the hydrodynamic force (a force due to fluid dynamic pressure) acting on a prismatic hull moving through the surface of an inviscid fluid. It has to be added to the hydrostatic (buoyancy) component to obtain the total vertical lift.

1 person likes this.

8. Joined: Aug 2007
Posts: 5,875
Likes: 311, Points: 83, Legacy Rep: 1749
Location: Tasmania,Australia

### rwatsonSenior Member

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.