0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3
0.25
Stagger 20 % Stagger 30%
It is interesting to note that where curves present higher undulation, the CR curves do not show similar trends. Probably the viscous phenomena have a strong influence on values.
Fn 0.30 0.35 0.40 Figure 31: [C 932 – L/1/3 = 5.08]
0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3
0.25
0.6 0.7 0.8 0.9 1.0 1.1 1.2
Stagger 6 % Stagger 10 % Stagger 20 % Stagger 30 %
0.45 0.50
0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5
IT Stagger 0% LWL
Stagger 6% LWL Stagger 10% LWL Stagger 20% LWL Stagger 30% LWL
Fn 0.25 0.30 0.35 0.40 Figure 34: [C 932 – L/1/3 = 4.66]
In the Figure 34 the performance of the staggered catamaran and the demihull are compared through the IT factor:
IT= Fn 0.30 0.35 0.40 Figure 32: [C 932 – L/1/3 = 5.74]
Stagger 10 % Stagger 20 % Stagger 30 %
0.45 0.50 or
CTCATstaggered CTDH
Into a wide speed range the staggered configurations can balance
improve the symmetric catamaran’s
performances (often worse than demihull). As it was to be expected the greatest improvements, up to 9% of resistance reduction, are reached for the greatest stagger and displacement.
6.
CONCLUSIONS AND RESEARCH DEVELOPMENTS
0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 Fn
Figure 33: [C 925 – L/1/3 = 4.66]
The figures show that can have quite different values changing configuration and hull form. Therefore, the use of values of a particular configuration (displacement, stagger, hull form) to evaluate the performance of other configurations
can generate significant errors.
Nevertheless, examining the trends of the curves it is possible to express the following considerations:
around Fn = 0.45, the curves of both models have a minimum;
between Fn = 0.35 and 0.40, the stagger advantage is reduced or disappeared;
in a wide speed range, for increasing stagger, the factors indicate a remarkable resistance reduction; of curves are amplified by
the undulations increasing stagger and displacement. It
Two displacement catamarans have been tested at same L/1/3 S/L and stagger. Residuary resistance coefficient and interference factors, IT and , are reported. has
highlighted that the great influence inaccuracies on
catamaran’s performance due to clearance, stagger and displacement, causes
if the
interference factors measured for a configuration are applied to evaluate the performance of a different solution (i.e. different displacement, clearance, stagger or hull form).
For Fn > 0.40 interference phenomena become less sensitive to speed variation.
The experimental data obtained highlight the great potentiality of stagger configuration. It has been measured resistance reductions up to 30 % vs. symmetric catamaran and up to 9 % vs. demihull.
The research is in progress with investigation on a third catamaran model.
To evaluate the feasibility of the staggered configuration, a preliminary design of water bus in inland waters have been realized [6] and sea-keeping model tests are planned.
experimental 0.45 0.50
B-30
©2007: Royal Institution of Naval Architects
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54