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Lesson 4.4 Trim and Draft FP AP LCF MP
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Class Topics Longitudinal Stability Terms Drag / Trim
Longitudinal Weight Shifts Example Longitudinal Weight Adds/Removals Examples
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AP MP FP DWL LBP
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LCF - The Longitudinal Center of Flotation
MP CFD LCF LCF - The Longitudinal Center of Flotation
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MP FP AP LCF LCF
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SHIFT - TA equals the longitudinal distance shifted
Trimming Moment = w x TA TA MP TA MP FP AP LCF MP MP LCF MP MP TA LCF LCF LCF w SHIFT - TA equals the longitudinal distance shifted
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Class Topics Longitudinal Stability Terms Drag / Trim
Longitudinal Weight Shifts Example Longitudinal Weight Adds/Removals Examples
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DRAG - A design feature having the draft aft greater than the draft fwd. Primarily done to increase plant effectiveness. 16' 0" 14' 0" DWL DRAG = 2 FT By the Stern
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TRIM - The difference between the forward and after drafts in excess of drag. DRAG = 0 16' 14' TRIM = 2 FT By the Stern
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DRAG = 1 Ft By the Stern 15' 14' TRIM =
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DRAG = 1 Ft By the Stern 13' 14' TRIM = 2' By the Bow
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DRAG = 1 Ft By the Stern 17' 13' TRIM = 3' By the Stern
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Class Topics Longitudinal Stability Terms Drag / Trim
Longitudinal Weight Shifts Example Longitudinal Weight Adds/Removals Examples
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Trimming Moment = w x TA w Change in Trim(CT) = TM MT1" LCF MP FP AP
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CT Trimming Moment = w x TA Change in Trim(CT) = TM MT1" LCF MP FP AP
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AP FP MP LCF
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AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF
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AP FP MP LCF CT
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AP MP FP CT CT CT CT CT LCF
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AP FP MP LCF CT df da
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df da CT = + AP FP MP LCF LCF da df CT LCF da df CT LCF da df CT LCF
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AP FP MP LCF CT = da df + LCF df LBP/2 LBP/2 + LCF LBP
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AP FP MP LCF CT LBP
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df df df LBP/2 + LCF df LBP/2 + LCF df LBP/2 + LCF CT df LBP/2 + LCF CT CT LBP/2 + LCF df CT CT LBP/2 + LCF df CT CT LBP/2 + LCF df LBP CT LBP LBP CT LBP/2 + LCF LBP df LBP CT LBP LBP/2 + LCF = LBP LBP LBP/2 + LCF LBP
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da df da df df = (LBP/2 + LCF) LBP x CT + CT = = CT - df CT df CT = =
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Class Topics Longitudinal Stability Terms Drag / Trim
Longitudinal Weight Shifts Example Longitudinal Weight Adds/Removals Examples
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Class Topics Longitudinal Stability Terms Drag / Trim
Longitudinal Weight Shifts Example Longitudinal Weight Adds/Removals Examples
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LCF
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LCF
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w PARALLEL SINKAGE = TPI
Parallel Sinkage (PS) is the distance that the drafts fore and aft increase due to a weight addition. LCF LCF LCF LCF LCF
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w PARALLEL SINKAGE = TPI w - PARALLEL RISE = TPI
Parallel Sinkage (PS) is the distance that the drafts fore and aft increase due to a weight addition. Parallel Rise (PR) is the distance that the drafts fore and aft decrease due to a weight removal. w TPI - PARALLEL RISE =
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Any weight addition can be equated to an addition at LCF and a shift to its final location.
AP FP MP LCF
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Any weight addition can be equated to an addition at LCF and a shift to its final location.
For a weight addition the Trimming Arm (TA) is equal to the distance from LCF to the center of the weight AP FP MP LCF TA
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AP FP MP LCF
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AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF
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AP FP MP LCF TA
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AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF AP FP MP LCF
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TOTAL DRAFT = PS/PR df or a AP FP MP LCF df PS da
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Class Topics Longitudinal Stability Terms Drag / Trim
Longitudinal Weight Shifts Example Longitudinal Weight Adds/Removals Examples
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LBP = 500 FT COMPT # L B = 24 FT L = 30 FT H = 12 FT LCF = 30 FT aft of MP FLOODED TO A DEPTH OF 6 FT AP MP FP 100 LCF 30' 130 280 500 250
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WTsw = B x L x D 35 = T B = 24 FT L = 30 FT D = 6 FT Wo = 4500 T Wf = T MP AP FP 500 250 LCF 280 100 130
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TPI = 40 T/IN PS = w TPI = T 40 T/IN = 3.09 IN MP AP FP 500 250 LCF 280 100 130 AP MP FP LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 LCF 280 100 130 500 250
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TA = = 165 FT TM = 165 FT x T = FT-T LCF 280 100 130 MP AP FP 500 250 TA 115
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TA = = 165 FT TM = 165 FT x T = FT-T LCF 280 MP AP FP 500 250 LCF 280 MP AP FP 500 250 LCF 280 MP AP FP 500 250 LCF 280 MP AP FP 500 250 LCF 280 MP AP FP 500 250 LCF 280 MP AP FP 500 250 LCF 280 MP AP FP 500 250 LCF 280 MP AP FP 500 250
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CT MT1" = 1050 FT-T/IN CT = TM MT1" = 20361 FT-T = 19.39 IN
LCF 280 MP AP FP 500 250 CT
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df = (LBP/2 + LCF) x CT LBP = ( ) x 19.39 500 = IN LCF 280 MP AP FP 500 250 df
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df da = CT - = = IN - DRAFTf = PS + df = = IN LCF 280 MP AP FP 500 250 da DRAFTf PS df
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DRAFTa = PS + da = = IN LCF 280 MP AP FP 500 250 DRAFTa da PS DRAFTf PS df
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