Help with Savitsky Prediction and shaft inclination

Hi, I'm working on a spreads. for planing hulls using formulas taken from Principles of Yacht Des.

The thing that's driving me crazy is that variations of shaft angle of about 5 deg. give back an increment /decrement of required power of 600 hp (from 500 to 1100) on a hull I'm using as a sample.

Is that possible that a change of 5 deg in shaft inclination gives such a different result????

 

i'm working on that calculations too, write me at crispilo@tiscali.it

ciao
Mistral

 

Solved...thanks

 

Hey Guys, are u students in "Laurea in ingegneria nautica" ????
However an increment of 600 hp caused by a variation of 5 degree is more than acceptable. The max efficiency of planing hulls is limited in a range of 2-4 degrees , then resistence's curve jump very high.
Bye

 

Now you have me interested in how such large horsepower changes occur in the given size of a craft. Could you pick a well known make and model and engine size with HP graphs to show the changes that must take place in the real world we boat in? Thank you.