Ship's hull form coefficients

(At preliminary merchant ship design)

Introduction

HELLO!

Herein I present a form to get basic hull form coefficients of merchant ships, following the formulae and concepts explained in Refs. 1 and 2, in order to serve as a guidance in the preliminary stage of a ship's design.

The main goal of this form is to get reasonable values of block (CB), midship section (CM) and loadline (CW) coefficients to be used in the different modules presented in the program Arqnaval, enclosed to the book Ref.2, and the program Getxonaval, being under construcion, to be used on-line via any browser, both intended to offer approximate and quick calculation methods in the preliminary stage of a ship design.

Some additional coefficients are also calculated and displayed in the enclosed form, of a lesser interest but that can also be of some utility.

Some user guidance

1) Service speed is meant at summer draft.

2) U / V rate refers to hull transverse sections, with zero (0) value for strong U shaped sections and one (1) value for net V shaped ones. A value between 0 and 1 should be selected for intermediate shapes. If you enter a zero the program takes an intermediate 0.5 value by defect; if you want a really strong U shape, zero should be simulated by inputing a very low value as 0.01. By defect the program adopts a value following fig. 3.4.1 in the book.

3) Alexander K constant is used in the formula 3.4.1 of the ref. book. By defect the program adopts a value following fig. 3.4.1 of the book.

Output of results (1st. table)

Following results are displayed:

• 1) Blok coefficients (CB) are calculated and displayed according to formulae from Alexander, Townsin, Katsoulis, Schneekluth and the average of all the four. Schneekluth formula is valid for a Froude Number between 0,14 and 0,32.


• 2) Midship section (CM) coefficients are calculated and displayed according to formulae from Kerlen and HSVA and the average of the two.


• 3) Loadline (CW) coefficients are calculated and displayed according to formulae from Schneekluth and J. Torroja and the average of the two.

Output of results (2nd. table)

• 1) Froude Number


• 2) Speed to squared root of length (knots and feet respect.)


• 3) Advisable center of buoyancy abscissa according to L.Troost formula (3.4.19) if CB is less than 0,76 y according to MARIN (3.4.20) if it is bigger.


• 4) Wetted surface with appendages up to selected draft, as per Holtrop and Menen formula (3.5.10).


• 5) Load line entrance half-angle, as per formula (3.4.22)


• 6) Parallel body length as a %Lpp, as per formula (3.4.21)

References

• Ref.1 Ship design for Efficiency and Economy. H. Schneekluth
• Ref.2 El Proyecto Básico del Buque Mercante (Basic design of merchant ships)
  R. Alvariño, J.J. Azpiroz, M.Meizoso FEIN 2007

Input data

Length Lpp (m)
Breadth B (m)
Draft design(m)
Service speed (knots)
Grade U-->V transv. sections (0-->1) *
Alexander's k coefficient *

Hull form Coefficients

Coefficients	Alex.-Town.-Kats.-Schn.	Average
CB
CM
CW

More results

Particulars	Values
Froude No.
Ratio V/rL
C.of bouyancy Abscisa (%Lpp) (+ fore)
Wetted surface (m2)
Loadline entrance Halfangle (º)
Parallel body Length (%Lpp)