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Definition
| Length Overall; Linear distance from bow to stern, measured parallel to baseline |
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Longitudinal curvature of vessel's deck
greater fwd than aft
increases buoyancy w/ air space |
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| Width + projections (bridgewing, gangway, etc) |
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inward slope of the ships side
measured widest beam less narrowest beam |
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opposite of tumblehome
outward slope of ships side
"dryer decks," throws waves from bow
creates space/lessens impact force of water |
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Definition
vert distance from lowest part of hull to waterline
indicated fwd aft amidships |
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distance from highest point to waterline
important re: bridge clearances
changes due to ballast |
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Transverse slope of deck
directs water to drains at sides
not specifically for added strength |
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| Rise or slant up athwartship from bottom keel to bilge aka rise of the bottom / rise of the floor |
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vertical distance from the lowest point of the hull to the side of the deck to which it is referred
depth = draft + freeboard |
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Dimensions taken from inside plating of a ship
important for cargo stowage |
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| distance measured vertically downard, at the side of vessel amidships, from upper edge of deckline to waterline |
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Definition
mid-ship part of vessel where constant cross-sectional shape is maintained thru length.
most merchant ships = parallel middle bodies, sides are vertical |
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Definition
immersed part of the hull fwd of middle body
expensive to build cuz it's curvy |
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Definition
immersed part of hull aft of middle body
where thrust is applied from prop
where torque is applied from rudder |
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Definition
| cheapest to build, hold most cargo |
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Term
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Definition
| symbol for centerline plane |
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Definition
| Used as an aid in locating points for design & building |
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Definition
established near base of ship
runs thru upper edge of flat plate keel
vert dims measured from this ref point |
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Definition
fore-aft (longitudinal)
at right angles to BL
hull shape essentially symmetrical on either side of CL |
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Term
| Transverse Vertical Planes |
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Definition
at equal intervals along length of vessel
aka frame stations
may NOT be equal to actual frame locations |
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Term
| Forward Perpendicular (FP) |
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Definition
| line perpendicular to BL, intersecting the fwd edge of the stem at the design waterline |
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Definition
| perpendicular to the baseline, intersecting the after end of the rudder post at the design waterline |
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Definition
| center of ship (longitudinally), located at the midpoint between FP and AP |
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Length Between Perpendiculars
measured parallel to BL |
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Definition
| Average between fwd and aft drafts |
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Definition
| mean draft compared to midship draft |
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Definition
| mean draft is > mid ship draft (which is actual draft of vsl) |
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| mean draft < midship draft (which is actual draft of vsl) |
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Definition
| Hog/Sag caused by cargo load |
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Term
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Definition
| Hog/Sag caused by crest & trough of wave under hull |
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Definition
Bottom of number is even
top is + 6 inches
middway is + 3 inches |
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Term
| 2 primary types of tonnage |
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Definition
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Term
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Definition
used to determine vsl earning capacity
from 13 cen "tun" - wine cask
equal to 100 cubic feet |
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Term
| Volumetric tonnage determines... |
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Definition
port fees, dock fees, dry dock chgs
idea is to base fees on ability to earn |
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Term
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Definition
| entire volume of the inside of the hull from main deck down to keel |
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Definition
Remaining tonnage after non-earning spaces are removed from Gross
ex tanks, foc'sle, psgr above main deck |
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Term
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Definition
Nominally water tight; no gasket
secured via bolt hooks (old wood battens)
allows for space deduction from gross |
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Definition
doublebottoms
fore/aft peak if water ballast only
poopdeck, bridge, foc'sle w/ tonnage openings |
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Term
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Definition
| design machinery space btwn 13 & 20% of total gross tonnage and 32% may be deducted |
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| cubic ft required per crewman |
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Definition
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Definition
displacement tons
deadweight tons
lightship tonos |
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Definition
weight of water displaced by hull
exactly equal to ships weight |
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Definition
| amount of water cargo fuel and stores a vessel can carry fully loaded |
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Definition
weight of empty ship
displacement of vessel w/ no cargo crew stores fuel water or ballast |
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Term
| Lightship tons + deadweight tons = ? |
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Definition
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Term
| volumetric tonnage: 1 ton = ? |
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Definition
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Term
weight tonnage:
long ton
short ton
metric ton |
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Definition
long = 2240 pounds
short = 2000 pounds
metric = 2204.6 pounds (1,000 kg) |
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Term
| 4 general categories of steel items used in shipbuilding |
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Definition
beams plates
columns shafts |
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Term
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Definition
| coordinated functions of all 4 groups of steel used in shipbuilding |
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Term
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Definition
length from crest to crest = length of vsl
height = 1/20 length of vessel
use of wave this size determines max load on hull girdle & scantling requirements |
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Term
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Definition
| total force acting on structure, usually expressed in pounds or tons |
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Definition
| force per unit area, usually expressed in pounds/tons per square inch |
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Definition
| distortion resulting from stress |
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Definition
| occurs between 2 parts of a body when each draws the other end toward itself |
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Term
| equation for tensile stress |
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Definition
Tensile Stress = Pull / Area
Ts = P/A |
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Definition
opposite of tensile stress
Cs = push/area |
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Term
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Definition
tendency of one body to slide over another body
magnitude of this tendency at any point is termed shearing stress |
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Definition
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Mild steel:
ultimate tensile strength
ultimate shearing strength |
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Definition
ult ts = 28-32 tons per sq inch
ult ss = 22 tons per sq inch |
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Definition
| compressed at about 18 tons per sq inch |
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Definition
| point at which metal will no longer return to its original shape |
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Definition
| metal hardens, slight additional weight stretches it out of proportion until reaches ultimate strength, then fails |
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| standard factor of safety |
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Definition
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Definition
| strength of individual parts of the ship |
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Definition
| strength of ship as a whole |
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Definition
| A moment of a force about any line is the product of the force times the perpendicular distance to that line |
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Term
| Bending moment: 100 lbs located 4' from end of board imbedded in a wall = |
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Definition
weight x distance
100 lbs x 4' = 400 ft-lbs |
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Term
| Bending moment: 100 lbs located 8' from end of board imbedded in wall |
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Definition
BM = weight x distance
BM = 100 lbs x 8'
BM = 800 ft lbs |
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Term
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Definition
| Horizontal strength members loaded vertically |
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Term
Load applied to center of beam causes...
upper surface must be under...
lower surface must be under... |
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Definition
...deflection
...compression
...tension |
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Term
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Definition
layer in deflected beam where compression & tension are neutral
located along center of gravity (centroid) |
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Term
| beam made up of 5 individual layers (versus solid beam) |
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Definition
will only carry 1/5 load vs solid
top 2 will NOT be under compression
bottom 2 will NOT be tension
middle will NOT be nuetral |
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Term
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Definition
...determines resistance/strength.
AKA larger distance from neutral axis to edges = stronger beam |
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Term
| 5 factors determine size of beam |
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Definition
1 type & amount of load on beam
2 distance btwn supports
3 type and efficiency of end connects
4 number of supports
5 material beam is made of |
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Term
| type & efficiency of end connections |
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Definition
A) fixed-ended rectangular beam supports twice as much concentrated load as free ended
B) deflection of fixed ended rect beam is 1/4th that of free ended |
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Term
| effect of number of supports |
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Definition
| greater # of supports in given distance equals shorter span. shorter span equals smaller bending moment. |
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Term
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Definition
most ship construction is mild grade steel
other materials: stainless steel
high tensile steel
aluminum |
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Term
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Definition
strut placed such that it is loaded vertically (also referred to as stanchion or pillar)
usually symmetrical (round) |
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Term
| shafts subjected to twisting motion... |
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Definition
...said to be in torsion
twisting moment = torque |
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Definition
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Term
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Definition
vessels must be constructed so that stresses may be graduallly and continuously dissipated
no part over/undersized
discontinuity or change in shape = stresses = failure |
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Term
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Definition
...fusion welding
6,000 degrees F
usually electric arc, gas less common |
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Term
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Definition
| ...starts to replace other joining methods. By WWII it has replaced them almost completely. |
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Definition
| main cause of cracks aboard ships. ex hatches, port openings, faulty welds |
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Term
| secondary causes of fractures |
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Definition
| low temp, unusually high bending moments, heavy seas |
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Term
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Definition
| backbone. ties together transverse bottom members. absorbs large portions of stresses from hull girder action. |
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Term
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Definition
| bar keel. flat plate keel. box keel. bilge keel. |
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Definition
| olderships. protects when grounded. 1st pt contact. reduced rolling. disadvantages: increased draft no xtra cargo space. |
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Definition
| utilizes increased shell plate thickness allowing it and components to better withstand dry docking /grounding loads. resembles i beam |
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Term
| transverse bulkheads assist... |
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Definition
| ...in supporting keel and bottom by transforming long flexible girder into shorter length |
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Definition
| act as conduit for wires/cables. allows access into other areas of double bottom. |
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Definition
| fin like pieces of steel plate fitted to hull at turn of bilge along midship length . reduce rolling in heavy seas. NOT for stability. |
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