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Alaska Pilots > Formulas and Conversions > Flashcards

Formulas and Conversions Flashcards

1
Q

Squat - Open water (feet) - Barrass method
(MacElrevey)

A

(C𝚋 x V²) / 30
- V is in kts
- margin of safety included
- initial squat is double the calculated value when accelerating from stopped

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2
Q

Squat - Open water (meters) - Barrass method
(MacElrevey)

A

(C𝚋 x V²) / 100
- V is in kts
- margin of safety included
- initial squat is double the calculated value when accelerating from stopped

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3
Q

Squat - Shallow water - Barrass method
(MacElrevey)

A

2 x open water squat
- margin of safety included

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4
Q

Wind Load - force formula (lbs) (Hooyer)

A

Force (lbs) = .004 x Area x V²
- Area is in ft²
- V is in kts
- divide by 2000 for tons
(Hooyer)

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5
Q

Wind load - Area w/ wind on beam formula
(Hooyer)

A

(LOA x D) - (LBP x mean draft)
- D = molded depth
(Hooyer)

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6
Q

Wind load - Area w/ wind on bow or stern (Hooyer)

A

(B x D) - (B x fwd or aft draft)
- D is molded depth
- B is molded breadth

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7
Q

Wind load - force formula (tonnes)
(Rowe)

A

(V² / 18) x (Sail Area / 1000)
- V is in meters/sec
- Sail Area (LOA x freeboard) is in meters²

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8
Q

Wind load - force on the beam formula (kg)
(Henson)

A

.08 x V² x Area
- V is in meters/sec
- Area is in meters²
- 20% safety factor included

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9
Q

Current load - force formula (short tons)
(Hooyer)

A

f x L x D x V²
f is factor -
- 1.1x draft = .0036
- 2x draft = .0018
- 3x or more = .0015
L = LBP in ft
D = mean draft in ft
V is in kts

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10
Q

Current load - force formula (kg) in deep water (6x draft)
(Henson)

A

40 x V² x Area
- V is in meters/sec
- Area (LBP x mean draft) is in meters²
- includes 20% safety factor

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11
Q

Current load - force formula (kg) with UKC 1.5x draft
(Henson)

A

110 x V² x Area
- V is in meters/sec
- Area (LBP x mean draft) is in meters²
- includes 20% safety factor

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12
Q

Current load - force formula (kg) with UKC 20% draft
(Henson)

A

150 x V² x Area
- V is in meters/sec
- Area (LBP x mean draft) is in meters²
- includes 20% safety factor

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13
Q

Current Load - force formula (kg) with UKC 10% draft
(Henson)

A

185 x V² x Area
- V is in meters/sec
- Area (LBP x mean draft) is in meters²
- includes 20% safety factor
- bollard pull required is 5x more as in deep water

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14
Q

Bollard Pull (metric tonnes) - formula for ships with large displacement ie: loaded tankers and bulk carriers
(Henson)

A

BP (metric tons) = ((displacement / 100,000) x 60) + 40
- displacement in long tons

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15
Q

Wave load - force formula (kg)
(Henson)

A

112 x LBP x H²
- H is wave height in meters
- LBP is in meters
- only for short period beam waves
- 20% safety factor included

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16
Q

Rate of Turn in degrees/min

A

360 / (3.14 x 2r /V) x 60
- r = radius of turn in nm
- V is in kts

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17
Q

Narrow channel Blockage factor as percentage
(MacElrevey)

A

% = (draft x breadth) / (channel depth x channel width)

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18
Q

Geographic range formula

A

1.17 x √ height of eye (ft)

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19
Q

Turning circle diameter
(Hooyer)

A

( 6(L-B) / (L+3B) ) x L
- diameter is in L (ship lengths)
- for full speed and full rudder

20
Q

Drift angle
(Hooyer)

A

L / C x 180
- C = 3.14 x turning circle diameter
- C is in L (ship lengths)

21
Q

Tug turning torque

A

force applied x distance from tug to PP

22
Q

Gyro and compass error

A

PGC
GE
T
V
M
D
C
- add West moving away from True
- compass error = deviation + variation

23
Q

Propeller Slip - Engine speed formula in feet and meters

A

in feet = (pitch x RPM x 60) / 6076
in meters = (pitch x RPM x 60) / 1852

24
Q

Propeller slip - slip %

A

( (engine speed - actual ship SMG) / engine speed) x 100

25
Q

1 meter = ______ feet

A

3.28 ft

26
Q

1nm = _____ meters

A

1852 m

27
Q

1nm = _____ feet

A

6076 ft

28
Q

Squat when 2 ships meet in narrow channel (MacElrevey)

A
  • generally increases by 50%
  • could be 60%-100%, with greater speed and less distance between ships
29
Q

1 cable (british) = ____ nautical miles

A

0.1 nm

30
Q

1 shot or shackle = ____ fathoms

A

15 fathoms

31
Q

1 fathom = ____ feet

A

6 ft

32
Q

1 shot or shackle = ____ feet

A

90 ft

33
Q

1 short ton (US ton) = ____ pounds

A

2000 lbs

34
Q

1 long ton (British ton) = ____ pounds

A

2240 lbs

35
Q

1 metric tonne = ____ lbs

A

2204 lbs

36
Q

1 metric tonne = ____ kilograms

A

1000 kg

37
Q

1 kilogram = ____ pounds

A

2.205 lbs

38
Q

1 inch mercury = ___ feet of water

A

1.13 ft of water

39
Q

standard atmosphere at sea level =

A

29.92 inches of mercury
1013.3 millibars
760 milliliters of mercury

40
Q

1 knot = ____ feet per minute

A

100 ft/min

41
Q

1 displacement ton = ___ long ton

A

1 long ton

42
Q

Bollard pull - horsepower to short tons
(Hooyer)

A

100 HP = 1 ton bollard pull

43
Q

convert kts to m/s formula (Rowe)

A

kts / 2 = m/s (Rowe)
1 m/s = 1.944 kts

44
Q

1 US Navy cable = _____ fathoms

A

120 fathoms

45
Q

1 kip = _____ pounds

A

1000 lbs

Alaska Pilots (36 decks)

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