Cs & av values of RINA

Hello there, i am a yacht design student and currently working on my 27m alluminium hull motor yacht which is my master thesis.
I am about to calculate my bottom pressures and i can't figure out what are the Cs and av values that i need to input for the p2 value which is : P2 = 15*(1+av)*(W/(L*Cs))*g*FL*F1*Fa

Cs is explained as "Support contour of the yacht, in m, defined as the transverse distance, measured along the hull, from the chines to 0.5L. For twin full yachts, Cs is twice the distance measured along the single hull." which is incomprehensible.

av is explained as : maximum design value of vertical acceleration,
in g, at the transverse section considered

Thank you in advance for your help!

 

Cs is the distance "1 + 1" (see picture), measured along the shell of the hull.
For multihulls, you need to measured one hull and multiplied by the number of equal hulls.
"av" is a variable that varies along the length of the boat. At some point in the regulation you are using you can find the formula that gives you the value of "av" for the area of the boat you are considering.

 

Thank you good sir!, its impossible to find those things online I will look for av more deeply in Rina then.

 

It is in Part B, Chapter 1, sec 5:

 

Thank you very much!

 

Forgot to ask, is this to be calculated only on 0.5L or for only frame?

 

Cs : just for the Main Section, usually at 0.5 Lbp from after perpendicular.
av : for every area of the ship you are calculating. As you can see on Ad Hoc's picture, it varies with x/L

 

Thank you and merry christmas !

 

You're welcome. I'm at your disposal if I can help with anything else.
I wish the same for you.