Sec. X1.2 



SYMBOLS AND THEIR TITLES 



905 



t/e — Slope, waterline, in run, with reference to 

 centerplane 



is — Slope, section line, with reference to base- 

 plane; this slope becomes greater than 90 deg in 

 way of a tumble home 



Iff — Slope, waterline, general 



/ — Square moment of area of a plane surface 

 about an axis in that plane 



II — Square moment of area of a waterplane 

 about the transverse axis through CF, for pitching 

 motion 



It — Square moment of area of a waterplane 

 about the longitudinal axis through CF, for 

 rolling motion 



Iw — Square moment of area of a free-water 

 surface, with axes defined for each case 



/jj — Square moment of area of a plane surface 

 through an axis x-x in that plane 



J — Advance coefficient, number, or ratio, = 

 UJ{nD) = Fx/(nZ)); F^/CnZ)) is the alternative 

 expression 



J — Moment of inertia of the mass of a body or 

 ship; this is a true moment of inertia as com- 

 pared to the square moment of area of a plane 

 surface denoted by I 



Jl — Moment of inertia of a body or ship for 

 pitching motion, about an axis transverse to the 

 plane of symmetry 



Jt — Moment of inertia of a body or ship for 

 rolling motion, about a longitudinal axis 



J^ , Jy , J, — Moments of inertia about the x-, 

 y-, and 2-body axes, respectively 



Jjj — Moment of inertia of the mass of a body 

 about an axis x-x 



Jabs , X(lambda) — Absolute advance coefficient, 

 number, or ratio, = UA/iimD) = V A/{TrnD) = 



fc— Constant of capillarity (6th ICSTS symbol) 

 k — Fractional value, at any point in a propul- 

 sion device, of the ultimate induced velocity Ui 

 far astern 



k — Radius of gyration 



fc — Surface roughness height, average; hill 

 height above a smooth reference surface 



k^ , ky , fc, — Radii of gyration about the x-, y-, 

 and z-body axes, respectively 

 K — Bulk modulus of elasticity of a Hquid 

 K — Rolling moment about longitudinal x-axis 

 Kq — Torque coefficient, non-dimensional, = 



Ks — Equivalent sand roughness; requires also 



a surface or area density factor and other relation- 

 ships, not yet worked out for the general case 



Kt — Thrust coefficient, non-dimensional, = 

 T/{fm'D') 



Kr//fo— Thrust-torque factor = TD/Q 



I — Chord length of an airfoil or hydrofoil; 

 alternative symbol c 



L — Length, the principal longitudinal dimen- 

 sion of a ship; any characteristic length, specified 

 in detail; for special study, the length on the 

 surface waterline WL of the immersed form of a 

 ship, at any draft and trim 



L — Lift as a force, when generated by a com- 

 bination of circulation and uniform flow or by a 

 deflected flow 



Lx — Length, afterbody, = L/2 



Lc — Length, projected, of the area bounded 

 by the chine of a planing craft 



Ld — Lift, dynamic, due to planing action 



Le — Length, entrance, from FP to section of 

 maximum area or to forward end of parallel 

 middlebody 



Lp — Length, forebody, = L/2 



Lh — Lift, hydrodynamic 



Lm — Length of model, as distinguished from 

 ship length Ls 



Lp — Length, parallel middlebody, of constant 

 shape and area 



Lr — Length, run, from section of maximum 

 area or after end of parallel middlebody to WL 

 termination or other designated point 



Ls — Length of ship, as distinguished from 

 model length Lm 



Lw — Length of a surface gravity wave from 

 crest to crest or trough to trough 



Lbf — Length, effective, for hydrodynamic 

 analysis, as defined locally 



LoA — Length, overall or extreme, wherever 

 occurring on the main hull, in a direction parallel 

 to the longitudinal axis 



Lpp — Length between perpendiculars (6th 

 ICSTS symbol) 



Lws — Length, mean wetted, of a planing craft 



LwL — Length, on any given waterline 



Lr, WL — Length, on designed waterline 



L/Bx — Length-beam ratio; beam-fineness ratio, 

 greater than unity 



L/D — Lift-drag ratio 



L/D — Length-depth ratio; depth-fineness ratio, 

 greater than unity 



L/D — Length-diameter or fineness ratio of a 

 body of revolution, greater than unity 



