High Speed Displacement-Type Hulls 601 
Since the date of that paper, quite a lot more evidence on this matter has reached me, 
both from actual seagoing experience and model tests in waves. In particular and resulting 
from model tests carried out in irregular waves at the Davidson Laboratory of the Stevens 
Institute in 1959, Figs. D1 and D2 were reproduced in a report of the “Development and 
Running of the ‘Brave’ Class Fast Patrol Boat” read at Goteborg in February 1960. 
SO fee as ee a 
— | 
MODEL TYPE 
56 VOSPER HARD CHINE 
57 PLANING FORM, 
WIDE & ROUND FORWARD 
ROUND FORM L+20% 
eit eal 
AVERAGE BOW ACCELERATION (G's) 
0 10 20 30 40 
AVERAGE SHIP SPEED (KNOTS) 
Fig. Dl. Average bow acceleration versus average ship speed 
in an irregular head sea; Beaufort scale sea state 5; average 
height, 5.16 feet; signal height, 8.10 feet 
MODEL TYPE 
56 VOSPER HARD CHINE 
57 PLANING, WIDE, : 
ROUNDED FORWARD 
58 ROUND FORM 
MAXIMUM BOW ACCELERATION (G's) 
0 10 20 30 40 
AVERAGE SHIP SPEED (KNOTS) 
Fig. D2, Average bow acceleration versus average ship speed 
in an irregular head sea; Beaufort scale sea state 5; average 
height, 5.16 feet; signal height, 8.10 feet 
This shows remarkably little difference between the round form 58 and the Vosper hard 
chine 56, especially when it is realised the round form was 20 percent longer for the same 
displacement. 
To summarise, there is little to choose between the forms for speed/length ratios 
between say V/V7, = 2.5 to 3.8. After this the hard chine planing form is a “must” for 
reasons of resistance. 
