aww198
11-10-2007, 11:54 AM
I'm trying to write a quick excel spreadsheet to work out powering and porpoising from Savitsky's 1964 paper and I've encountered a couple of problems - can anyone point out where I am going wrong?
1) Working logically through 'Table 1' 'Computational Procedure Hydrodynamic Performance of Prismatic Planing Hull' I have got down as far as row 10 on the table and agree with all the numbers. However when calculating the formula in 10 for Df I am not getting anything like the stated 7.340. I don't know if its because I am not using the correct value for p, or if I'm simply messing up the calculation or if there is a term missing in the formula. Any one have any ideas for me?
2) For the porpoising calc I've created a spreadsheet for it and it all works given the inputs that are in the example in the paper, however when I input my boat particulars I'm getting a value for SQRT Cl/2 of less than 0.1, which is off the Savitsky porpoising limit graph. Is this a common occurance for light weight boats <~10 tonnes??
Thanks
1) Working logically through 'Table 1' 'Computational Procedure Hydrodynamic Performance of Prismatic Planing Hull' I have got down as far as row 10 on the table and agree with all the numbers. However when calculating the formula in 10 for Df I am not getting anything like the stated 7.340. I don't know if its because I am not using the correct value for p, or if I'm simply messing up the calculation or if there is a term missing in the formula. Any one have any ideas for me?
2) For the porpoising calc I've created a spreadsheet for it and it all works given the inputs that are in the example in the paper, however when I input my boat particulars I'm getting a value for SQRT Cl/2 of less than 0.1, which is off the Savitsky porpoising limit graph. Is this a common occurance for light weight boats <~10 tonnes??
Thanks