Forces on Fishing Vessels and Equipment PDF

Forces on Fishing Vessels and Equipment FISH 119 Module 3 – Marine Engineering For class use only  Learning objectives Determine the different types of fishing vessel in motion 2...

Forces on Fishing Vessels and Equipment FISH 119 Module 3 – Marine Engineering For class use only  Learning objectives Determine the different types of fishing vessel in motion 2 Measuring fishing vessel stability Analyze fishing vessel stability standards Measure fishing winch storage capacity, torque, CFOS-UPV and power  Outline Forces on a vessel Vessel motion Vessel stability Buoyancy 3 stability standards Fishing vessel operations Fuel consumption of engine Speed of operation Fishing winch Length of rope to be stored Torque Power CFOS-UPV  Ship motion 6 types of ship motion as assumed in fix space: Translational motion – movement 4 perpendicular along an axis Surge – forward/backward Sway – horizontal movement Heave – upward/downward CFOS-UPV Source: The Maritime Engineering Reference Book  Ship motion Rotation motion – movement of attempting to rotate in an axis Roll – rocking motion to either 5 starboard or port Pitch – rocking motion to either bow or stern Yaw – rotation of the bow to either starboard or port CFOS-UPV Source: The Maritime Engineering Reference Book  SHIP MOTION 6 CFOS-UPV  Ship stability Buoyancy force Makes ship float despite being made of steel Balance in downward weight 7 of ship and upward force that liquid exerts Archimedes’ principle - upward buoyant force exerted on a body immersed in a fluid, whether fully or partially, is equal to the CFOS-UPV weight of the fluid that the body displaces.  Buoyancy Review Buoyant force formula: 𝐹𝑏 = 𝑚 𝑑𝑙 𝑔 = 𝜌𝑑𝑙 ∗ 𝑉𝑑𝑙 ∗ 𝑔 = 𝜌𝑑𝑙 ∗ 𝑉𝑠 ∗ 𝑔 𝑉𝑠 = 𝑉𝑑𝑙 8 Where: 𝑚 𝑑𝑙 = 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑑 𝑙𝑖𝑞𝑢𝑖𝑑 𝜌𝑑𝑙 = 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑑 𝑙𝑖𝑞𝑢𝑖𝑑 𝑉𝑠 = 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑢𝑏𝑚𝑒𝑒𝑟𝑔𝑒𝑑 𝑝𝑜𝑟𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡ℎ𝑒 𝑠ℎ𝑖𝑝 𝑉𝑑𝑙 = 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑑 𝑙𝑖𝑞𝑢𝑖𝑑 CFOS-UPV 𝑔 = 𝑎𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛 𝑑𝑢𝑒 𝑡𝑜 𝑔𝑟𝑎𝑣𝑖𝑡𝑦  Buoyancy Review To determine whether an object will float or not: If 𝐹𝑏 > 𝑊𝑠 = 𝑠ℎ𝑖𝑝 𝑓𝑙𝑜𝑎𝑡𝑠, 𝑝𝑎𝑟𝑡𝑖𝑎𝑙𝑙𝑦 𝑠𝑢𝑏𝑚𝑒𝑟𝑔𝑒𝑑 9 If 𝐹𝑏 = 𝑊𝑠 = 𝑠ℎ𝑖𝑝 𝑓𝑙𝑜𝑎𝑡𝑠, 𝑓𝑢𝑙𝑙𝑦 𝑠𝑢𝑏𝑚𝑒𝑟𝑔𝑒𝑑 If 𝐹𝑏 < 𝑊𝑠 = 𝑠ℎ𝑖𝑝 𝑤𝑖𝑙𝑙 𝑠𝑖𝑛𝑘 **𝑊𝑠 = 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑠ℎ𝑖𝑝 CFOS-UPV Ship stability Reserve buoyancy Enables ship to float even with addition of weights 10 Volume of hull above waterline, accommodation, deckhouses, other structures Must be watertight! CFOS-UPV Sample buoyancy problem A fishing vessel is docked in Iloilo port and the submerged portion weighs 5 tonnes with submerged hull volume of 200 ft 3. Determine F b and prove that the fishing vessel floats. Given: 11 𝑚 𝑑𝑙 = 5 𝑡𝑜𝑛𝑛𝑒𝑠 𝑉𝑠 = 200𝑓𝑡 3 𝜌𝑑𝑙 = 1025 𝑘𝑔ൗ𝑚 3 𝑔 = 9.8 𝑚Τ𝑠 2 Find: 𝐹𝑏 , 𝑊𝑜 , 𝑎𝑛𝑑 𝐹𝑏 =/>/ 𝑊𝑜 , 𝑡ℎ𝑒 𝑣𝑒𝑠𝑠𝑒𝑙 𝑓𝑙𝑜𝑎𝑡𝑠 CFOS-UPV Intact stability Ability of partially/totally submerged body to float upright When tilted, should have the ability to correct itself into an upright position again 15 CFOS-UPV Source: http://www.martialmakers.com/?p=44  Longitudinal vs. Transverse stability Longitudinal stability Ship’s tendency to upright itself when pitching No problems with stability 16 Transverse stability Ship’s tendency to upright itself when it rolls This is what we will discuss CFOS-UPV  Simplification of buoyancy All buoyant forces acting on submerged part of the hull is added together into a single vector pointing upwards called center of buoyancy 17 CFOS-UPV Source: A Guide to Fishing Vessel Stability  Simplification of weights All weights in the vessel (stores, fuel, equipment, fishing gear) can be represented as the center of gravity 18 CFOS-UPV Source: A Guide to Fishing Vessel Stability  Movement of G If weight is added above the vessel, G moves up Adding more weight – G moves down 19 CFOS-UPV Source: A Guide to Fishing Vessel Stability  Movement of B B acts on the centerline (vertical broken lines) of the vessel. If the vessel rolls port side, B also moves port side but the vector still acts upward at right angles. 20 CFOS-UPV Source: A Guide to Fishing Vessel Stability  Stability change of rolling vessel Floating upright, G and B are both at the center line. When the vessel rolls at 20° port side, B moves and levers the boat back upright. The horizontal distance between G and B is called the righting lever (GZ) and the force of a successful upright is called the righting 21 force. CFOS-UPV Source: A Guide to Fishing Vessel Stability  Stability change of rolling vessel If the vessel rolls too far, say 80°, the vessel cannot produce a righting force. Instead, it will cause the vessel to capsize, the force of which is called the capsize force. The vessel’s hull and deck determines how much buoyant force is 22 available for enough righting force. CFOS-UPV Source: A Guide to Fishing Vessel Stability  Stability change of rolling vessel If the vessel has too much weight, the freeboard lessens. This will make the deck to submerge into water sooner when the vessel rolls. The vessel will capsize earlier at a lower angle because of this. 23 CFOS-UPV Source: A Guide to Fishing Vessel Stability  Stability curve of a vessel GZ and the righting force significantly lessens as the deck is dipped in water (downflooding). 24 Note that a negative GZ means that the vessel is experiencing the capsize force. CFOS-UPV  Stability hazards Fishing vessel owners must be familiar with stability hazards to ensure the safety of their crew. 25 Some stability hazards that must be addressed properly to avoid vessel capsize: 1. Overloading 2. Swamping of the deck 3. Shifting catch 4. Trawling, dredging and towing CFOS-UPV 5. Lifting the catch sideways  Overloading the hazard of overloading through reduction of freeboard. The capsize angle is reduced, which means that 26 it is much easier to capsize an overloaded vessel Source: A Guide to Fishing Vessel Stability CFOS-UPV  Swamping of the deck Water on deck is a stability hazard. Waves can introduce tonnes of water- weight and cause a rolling force called free-surface effects. The figure below shows that even at small angles, water completely shifts to either port or starboard to attempt a capsize. Owners must make sure that scupper holes are free and has no obstacles to effectively drain water 27 from deck. CFOS-UPV Source: A Guide to Fishing Vessel Stability  Shifting catch Fish catch stored in bulk or in boxes are recommended to be stored at the center line or 28 balanced port and starboard. A shift to this (see figure below) drastically reduces stability. Source: A Guide to Fishing Vessel Stability CFOS-UPV  Trawling, dredging, and towing The tow line’s load when performing either of this three causes: 1. General reduction of freeboard (mostly at the aft) 2. Transfer of G from below the center of the hull to the towing point. Reducing stability 29 CFOS-UPV Source: A Guide to Fishing Vessel Stability  Trawling, dredging, and towing The situation is similar to the previous slide, only that it has tow towing points that critically 30 decreases the capsize angle and GZ. CFOS-UPV Source: A Guide to Fishing Vessel Stability  Lifting the Catch Sideways Keep in mind that when there is a power block that lifts a catch upward to the highest point, G 31 automatically shifts to that point despite the catch still being near the waterline. The heavier the catch is lifted, the lesser the ship’s stability. CFOS-UPV Source: A Guide to Fishing Vessel Stability  Calculating Ship Stability You now know B, G and the center line. Another point is introduced, which is the metacenter (M). M is defined as a point where the ship is 32 virtually suspended. This can be identified by drawing a vertical line from the shifted position of B up to the point where the vertical line intercepts the center line (broken line). CFOS-UPV Source: Ship Knowledge: Ship Design Construction and Operation  Calculating BM BM is the vertical distance from the metacenter (M) and the buoyancy force 33 (B). BM can be calculated using the following formula: 1 𝐿𝐵 3 𝐵𝑀 = ∗ 12 𝑉𝑑 Where: 𝑉𝑑 = 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑢𝑏𝑚𝑒𝑟𝑔𝑒𝑑 𝑝𝑎𝑟𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑠ℎ𝑖𝑝 𝐿 = 𝑜𝑣𝑒𝑟𝑎𝑙𝑙 𝑙𝑒𝑛𝑔𝑡ℎ CFOS-UPV 𝐵 = 𝑜𝑣𝑒𝑟𝑎𝑙𝑙 𝑏𝑟𝑒𝑎𝑑𝑡ℎ  KG and KB as given KG is the distance between the keel (K) and G. This value is initially given by the 34 shipyard. Added weights change the value of KG. KB can be found with T on hydrostatic tables of the ship. CFOS-UPV  Values of GM GM has three (3) values: GM + = M above G GM - = M below G GM 0 = M and G have the same 35 location (KM = KG) GM can be calculated using the following formulae: GM = KB + BM – KG CFOS-UPV GM = KM – KG Source: Ship Knowledge: Ship Design Construction and Operation  Calculating GZ GZ was already mentioned in the previous slides and you have observed that there are stability angles that corresponds to each GZ value. 36 GZ can be calculated using the stability angle (φ) and the GM values using the formula 𝐺𝑍 s𝑖𝑛𝜑 = → 𝐺𝑍 = 𝐺𝑀𝑠𝑖𝑛𝜑 𝐺𝑀 Source: Ship Knowledge: Ship Design Construction and Operation CFOS-UPV  A more detailed stability curve description When the ship is upright, there are no φ, GZ, and GM. 37 CFOS-UPV Source: Ship Knowledge: Ship Design Construction and Operation  A more detailed stability curve description GZ starts to increase as soon as the ship tilts or “lists” as caused by an external force. 38 CFOS-UPV Source: Ship Knowledge: Ship Design Construction and Operation  A more detailed stability curve description GZ starts to decrease when the bilge comes out of the water since it indicates that the 39 submerged volume lessens, which results to a lower GM value CFOS-UPV Source: Ship Knowledge: Ship Design Construction and Operation  A more detailed stability curve description When G and B are on the same vertical line, GZ becomes 0. Note that the formula 𝐺𝑍 40 s𝑖𝑛𝜑 = → 𝐺𝑍 = 𝐺𝑀𝑠𝑖𝑛𝜑 𝐺𝑀 does not apply anymore since GM is also 0 (G=M). The φ (around 55-60°) in this figure is purely theoretical and used for CFOS-UPV illustration purposes only. Source: Ship Knowledge: Ship Design Construction and Operation  A more detailed stability curve description If the vessel tilts further, KM value will become lesser than KG (KM