Environmental Factors - Shiphandling Facts and Rules

Question 1

Environmental Factors - high sided ships in wind

Answer 1

feel the wind significantly when 3x ship speed

Question 2

Environmental Factors - low sided ships in wind

Answer 2

feel the wind significantly when 5x ship speed

Question 3

Environmental Factors - wind effect on slowing ship
(Rowe)

Answer 3

• most ships head up into the wind as they slow except if trimmed well down by the stern (Rowe pg 38, 41)

Question 4

Environmental Factors - backing with wind

Answer 4

• most ships back into the wind esp. if trimmed by the stern
• transverse force and windage make predicting this unreliable (Rowe pg 41)

Question 5

Environmental Factors - stopped with wind (Rowe)

Answer 5

• most ships lie with the wind just forward or aft of the beam when stopped (Rowe pg 38)

Question 6

Environmental Factors -
wind force (lbs) =
(Hooyer)

Answer 6

0.004 x V(kts)^2 x area
(divide by 2000 for tons)
- area in ft^2
- speed in kts

Question 7

Environmental Factors -
current acts on ship’s…
(Hooyer)

Answer 7

center of gravity (Hooyer pg 62)

Question 8

Environmental Factors -
wind acts on ship…
(Hooyer)

Answer 8

by creating a wind lever between wind point and PP (Hooyer pg 62)

Question 9

Environmental Factors - trimming by the stern with wind

Answer 9

• will reduce head into wind tendency with headway
• will increase backing into wind tendency with sternway

Question 10

Environmental Factors - wind force varies…

Answer 10

as the square of wind speed

Question 11

Environmental Factors - current turning effect (Hooyer)

Answer 11

• no turning effect as long as entire ship is subjected to even flow
• a turning effect when part of ship is exposed to a current (Hooyer pg 62)

Question 12

Environmental Factors - wind to current comparison
(MacElrevey)

Answer 12

30 kts wind = 1 kt current (MacElrevey pg 130)

Question 13

Environmental Factors - shallow water vs. deep water current power
(Rowe)

Answer 13

• with depth to draft ratio of 1.05 the current force is 3x that of 3.0 ratio
  (Rowe pg 81)