Section 6: Impact of the Current.


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In untamed ocean a boat is taken care of in the same path with or without ebb and flow ... This is know as
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Part 6: Effect of the Current

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Ch6. Impact of the ebb and flow An ebb and flow (mass of water) is a few hundred times denser than air/creates powers of awesome greatness In vast ocean a boat is taken care of similarly with or without ebb and flow The boat in an ebb and flow is being diverted in respect to altered items (floats, secured vessels, hindrances… ) Prior to begin any manœuvre: evaluate tidal strenght and bearing keeping in mind the end goal to determine adequate space

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Ch6. Impact of the flow/Position of Pivot Point Current follows up on submerged segment of boat When cruising with ebb and flow: ground speed = speed in water + pace of ebb and flow When cruising against ebb and flow: ground speed = speed in water – rate of ebb and flow

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Ch6. Impact of the current/Position of Pivot Point Steering in the current: Moving in the current: Faster: rotate point close bow, great controlling Slower: same as sponsorship , turn point close stern , temperamental boat Moving against the present: Pivot point in bow quarters, great guiding, stable boat

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Ch6. Impact of transverse current In pillar current: ship must remunerate the impact of the current

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Ch6. Impact of transverse flow Ship dead in the water: Force applied by the ebb and flow is expansive Proportional to uncovered submerged surface of boat (LxT) and to squared speed of ebb and flow V² Force F = C x L x T x V² Example: tanker of 260m Lenght

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Ch6. Impact of the ebb and flow/Working in a tide When tide streams over a billet , it can be utilized to: Improve moderate pace control Create horizontal movement Always better to stem the tide

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Ch6. Impact of the ebb and flow/Tide from ahead Short kicks ahead to keep up progress through the water and keep turn point forward with little speed over ground Good guiding lever Good control over the boat - This is know as « stemming the thide »: boat\'s rate greater than momentum speed.

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Ch6. Impact of the ebb and flow/Tide from toward the back Most unsuitable circumstance Extremely hard to keep positive control of the boat To keep turn point ahead, boat must be running at a rate over ground much higher than velocity of the tide: awfully quick To decrease speed: motor toward the back/turn point moves after + transverse push

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Ch6. Impact of the momentum/Working over a tide Balance boat\'s pace through the water and tidal stream 2. Make sideway (horizontal movement): - use rudder point alone or with kick ahead - flow goes onto inverse bow - resultant of 2 vectors brings vessel towards the compartment (crablike) - to stop float: bring boat\'s head into the tide

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Ch6. Impact of the ebb and flow/Working over a tide When working over a tide: Be tolerant Never surge the move Always put the tide fine on the bow Don\'t put the tide too far around on the bow: - great horizontal movement - hard to bring ship again into the tide

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Ch6. Impact of the flow/Vectors Ship\'s head into the tide Ship\'s pace through the water = velocity of tide No sideways float : α = 0 (point between boat\'s heading and ebb and flow)

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Ch6. Impact of the current/Vectors α = 60° and V = S V1 < S → boat is supporting V and S produce R (float) Conclusion: - If V= S , the boat will billet toward the back of his position V must be expanded to compartment at the great spot (see next slide).

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Ch6. Impact of the current/Vectors To keep position: V must be expanded until V1 = S Then will R correspond with V2 And vessel floats opposite towards the compartment. For α = 22°5: S = 2\' → V = 2\'3/R = 0\'8 S = 3\' → V = 3\'3/R = 1\'2 For α = 45°: S = 2\' → V = 2\'8/R = 2\' S = 3\' → V = 4\'3/R = 3\'

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Ch6. Impact of current on mobility Turning in the current With the current, the boat makes a wide swing Against the present it makes a tight swing

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Ch6. Swinging on a stay A boat with a completing tide swing 180° to stem the tide before continuing to its billet. In a slender conduit the boat Swings on a grapple, keeping A tight control over the position. This is just conceivable if the base is clear of deterrents

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Ch6. Impact of the flow/Swinging on a grapple This move relies on upon experience and ability and: Depth of water UKC (Under Keel Clearance) Strenght of the ebb and flow Type of base Type of motor force accessible Size of the boat Amount of room accessible for turn

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Ch6. Impact of the flow/Bends in a tidal River The tide might be of various strenghts : quickly on the outside yet weaker within the twist

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Ch6. Impact of the flow/Following tide The solid tide is chipping away at the stern with the turn point forward: great turning lever and solid turning power. Suspicion + kick ahead and counter rudder

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Ch6. Impact of the rudder/Following Tide A boat can respond viciously and quickly to this power : keep in mind. Better to keep more to the outside of the curve: the boat is dependably in the zone of more grounded taking after tide.

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Ch6. Impact of the rudder/Tide from ahead When a vast boat arranges a twist in a channel with ebb and flow from ahead: Better to keep to within so that the bow does not enter the range of more grounded ebb and flow amid the turn. This side is frequently the shallow side also

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Ch6. Impact of the rudder/Tide from ahead In this position, the boat\'s bow is affected by the solid Tide : the turning minute contradicts the expected turn. Danger of establishing Anticipation with steerage and force

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Ch6. Impact of current/Rapid alters in tidal course

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Ch6. Impact of ebb and flow/Rapid alters in tidal course A boat can pass near shallow ranges or man rolled out structures where the tide improvements quickly in bearing. On the off chance that the boat continues at moderate speed this can have genuine Consequences for the taking care of.

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Ch6. Impact of current/Rapid alters in tidal course

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Ch6. Impact of the momentum/Restricting the tidal stream Avoid intense points with a wharf, even with powerless tides The tide is compelled to stream speedier amongst boat and compartment: a low weight shows up and the boat is sucked towards the quay.

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Ch6. Impact of the ebb and flow/Tidal powers Force of the tide relies on upon : Draft and profundity of water Ship\'s bow setup Velocity of the tide Under bottom leeway Force of tide can change with the profundity : a tidal contrast Of up to 2.5knots over a profundity of 5 meter is conceivable. Distributed « Tidal Stream » is here and there off base.

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Ch6. Impact of the ebb and flow/Tidal strengths Force of the tide: straightforwardly corresponding to the square of the speed A little increment in pace implies a tremendous increment in power applied upon a boat

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Ch6. Impact of the momentum/Tidal strengths UKC : blocking impact of a vessel when the UKC is decreased/the tide can\'t stream under and is compelled to stream around

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Ch6. Impact of the momentum/Tidal power at stay 50.000DWT tanker at grapple/5 ties tide/profundity/draft proportion: 3.0: The tidal power = 19 tons (applied on the windlass)

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Ch6. Impact of the flow/Tidal power at stay 50.000DWT tanker at grapple/5 hitches tide/profundity/draft ratio:1.1 because of falling tide: Tidal power expands three times to 64 tons and can surpass the Holding force of the stay → boat will drag.

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Longitudinal powers on tanker at stay Wind 50knots/Tide: 5knots

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Ch6. Impact of the flow/Lateral tidal powers When boat moored or held with the tide on the shaft with a little UKC: sidelong constrain made can be tremendous

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Ch6. Impact of the current/Lateral tidal strengths Example 1: Ship of 280.000 dwt/draft 22m Current: 1knot on the pillar Depth-draft proportion: 1.05 Total horizontal power = 328 tons Example 2: Same boat Current: 1,5 bunches on the bar Total parallel power = 700 tons

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