Pt. Barrow
Wrangell Is.
10 Rams
@ 23.9 MW
70
33 Rams
@ 34.3 MW
7 Rams
@44.8 MW
220 Rams @ 34.3 MW
Cape Lisburne
14 Rams @ 44.8 MW
Pt. Hope
Russia
USA
65
Nome
14 Rams
@ 23.9 MW
St. Lawrence Is.
147 Rams
@ 34.3 MW
60
St. Matthew Is.
15 Rams
@ 9.0 MW
53 Rams
Nunivak Is.
@ 23.9 MW
Ice Edge
St. Paul Is.
St. George Is.
55
Dutch Harbor
s
Island
Aleut
ian
50
160
180
170
Figure 23. Number of ramming operations during the transit of U.S. icebreaker Polar Sea
from 23 March to 4 April 1983 (after Voelker 1991).
conditions. Though most of the hulls were coated
information, readers are referred to their paper and
with Inerta, a few hulls were bare steel, and one
to the reports prepared for that study. A summary
hull was fitted with a stainless-steel band at the
of their performance predictors is given below.
waterline. Performance measures included in their
study are level-ice hull resistance, propulsive per-
Resistance in level ice
formance, hull lubrication, ridge resistance, turn-
For chined ships, an expression for ice resistance
ing performance and open water resistance. Ac-
at a speed of 1 m/s is given as
cording to Keinonen et al. (1991), these results were
compiled to understand the influence of key pa-
R1 = 0.08+0.0177 CS CH B0.7 L0.2 T0.1 H1.25
rameters on the performance of icebreakers. The
{1 0.0083 (t + 30)} {0.63 + 0.00074 σf}
key parameters chosen for this comparison were
{1 + 0.0018 (90 ψ)1.4} {1 + 0.004 (ϕ 5)1.5}
simple and obvious to all observers. For detailed
26
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