!I0 nVDROnVNAMIQS IN SHIP DESIGN 



Wove FVofile at 12 hi. Jy 0371, f„' 259 Wove Profile ot 16 M. 1^- 1.161; F„- 0.i45. 



Sec. 52.2 



Fio. .'i2.R OBSF.RVF.n Wave Profiles at Two Speeds on a CiiiNnoAT 



setAotl in this manner [Powoii, J. W., SXAME, 

 1902, p. 49 and PI. 11]. Wave profilos ob.served at 

 two speeds during tiie trials of the U. S. Coast 

 Guard cutter Manning of the late 1890's are 

 drawn over an outboard profile of the ship in 

 Fig. 52.B [Peabody, C. H., SXAME, 1899, PI. 

 93; NA, 1904, Fig. 20S, p. 513]. 



There arc in the literature litcrallj' thousands 

 of photographs of ships inidorway, surrounded 

 (on the near side at least) by the waves of the 

 ship's Velox system. Almost never are the.se 

 photographs of more than pictorial value becau-se 

 either: 



(1) The}' do not show the wave profile directly 

 against the ship's side, or 



(2) They do not state the exact speed at which 

 the ship is traveling. 



Nevertheless, they are better than no data at all, 

 especially because sj'stematic procedures are 

 lacking for the prediction of wave profiles along- 

 side models or ships in advance of tests or trials. 



One interesting photograph of this kind shows 

 a small battleship of the German Deulschland 

 class at full speed [STG, 1940, p. 341]. Another, 

 equally interesting becau.sc of two very large 

 wave crcstvS that appear in the photograph, shows 

 the German World War I battle cruiser Gocbcn 

 at what appears to be full speed [USXI, 1912, 

 Vol. 38, p. 1GG8]. A third sliows wave profiles 

 along.side the Gennan battle cmisor Moltke of the 

 World War I pcri(Kl (SchilTbau, 22 May 1912, 

 p. G49|. These indicate in a general way that the 

 first Velox wave is something less than one ship 

 length long, because of the lag of the first wave 

 crast aimft the bow, but otherwise they are useless 

 for analysis by any known method. 



Some data are listed here relative to excellent 

 photographs of certain French men-of-war of a 

 half-century ago, wlion underway at what appear 

 to Ix; full speed and full power. The i)liotograplis 

 in qucHtion are rcproductid in the .Inly 19."j4 issue 

 of the U. S. Xavnl Institiile Procecdiiig.s, jjages 

 79(i to 799. The nuincrical data appenilnl here arc 



taken from contemjiorary issues of "Jane's 

 Fighting Ships": 



(a) French cruiser Condi of about 1904, making about 



22 kt. The photograph shows that the Velox wave 

 length is about L/2. For this vessel, L = 452.75 ft, 

 B = 65.33 ft, ;/ = 24.5 ft, A = 10,000 t, P., = 

 20,500 horses, V = 21 kt (nominal); for 22 kt, 

 T, = 1.034. 



(b) French crui.scr Chaleaurcnault of about 1S9S. The 



photograph reveals a considerable trim by the stern 

 and a Velox wave length of well over L. Here 

 L = 443 ft, B = 56 ft, // = 22.5 ft, A = 8,01S t; 

 Ps = 23,000 horses, V = 23 kt (estimated); for 



23 kt, 7', = 1.093. For a speed-length quotient only 

 slightly greater than that of the Condi, the Velox 

 wave length appears to be much greater. 



(c) French battleship MagctUa of 1890. The photograph 



gives the distinct impression that the ship is down 

 by the head. The Velox wave length appears to be 

 about L/2. Here L = 330 ft, B = 65.5 ft, // = 28.5 

 ft, A ■= 10,850 t, Ps = 12,000 horses, F = 16 kt; 

 T, = 0.881 at this speed. 



(d) The Voltaire shows a Velox wave length of about L/2. 



For this ship, L\(-l = 475.75 ft, B = 84.75 ft, 

 H = 27.5 ft, A = 18,400 t, Ps = 22,500 horses, 

 V = 19.4 kt; T, = 0.889 at this speed. 



(e) A photographic wave profile of the U. S. battleship 



Iowa (old), presumably made at or near full s|)oed, 

 shows one crest at the bow, one amidships, and one 

 at the stern [.\SNE, Aug 1897, p. 454). A similar 

 photograph appears in "Jane's Fighting Ships," 

 1910, p. 192. The wave length at this speed, assumed 

 to be 17.087 kt, is thus about half the length of the 

 ship. For a waterliiic length of 360 ft, 7', = 0.9005, 

 F„ = 0.26S2. For a trochoidal wave in deep water, 

 the wave Icngtli Lw for 17 kt is about 1(>2 ft, some- 

 thing less than half the ship lengtli. Data for the 

 old Iowa, corresponding to thase for the French 

 ships, are: />,r,, = 360 ft, B = 72.0 ft, // - 24.02 ft, 

 A = 11,363 t, Ps = 11,835 horses, Cp - 0.668, 

 Cx = 0.944, S = 31,110 ft', Cr = 0.7:53, .\x - 1,635 

 ft«. 



(f) Wave profiles at two speeds for the Italian crui.'wr 



Picmontc are publi.shed in INA, 1SS9, Plato XXVII. 

 The ship is 325 ft long, and for the higher s|>ced the 

 wave length is about eijual to the ship length, 

 minus the lag in the bow-wave crest. At 20 kt the 

 value of T, Is 1.11, F. - 0.331; at 21.5 kt, 7', is 

 1.193 !tnd /•■„ - 0..3.5.5. 



(g) The Danish ship Tjaldur is shown ninning at IS kt, 



revealing a deep trough at an estirnati'd position of 

 O.l.'iL from llic bow and a seronil crest (following 



