Truncated transome - question about Cp ?

I have a question about truncated waterlines. In computing Cp, can one use imaginary extension of waterlines of the healed hull in order to compute true value of Cp? The picture should explain my question. I do understand that there is a discrepancy in this, but what is more wrong:

(a) compute Cp with truncated waterline (and get distorted hull's shape Cp) or
(b) compute Cp with imaginary waterlines (and get an hydraulics error and get more proper shape for computational purposes)?


Thank you all for your help.

 

Depends on what you need the Cp for. For powering, it depends on speed. Unless your Fn is well above 1.3, the drag caused by an immersed transom needs to be accounted for unless your standard series data accounts for that.