Audio Overview Ch9 Part 5 Illustrative_Trim_Problems

STABILITY AND TRIM FOR THE SHIP'S OFFICER, 4th Edition, by William E. George Illustrative Trim Problems Source Material: Pages 208–214 Audio Overview 32 concluding Chapter 9 and details the practical application of trim theory through standardized examples, forensic LCG determination, and the use of simultaneous equations for cargo loss analysis. I. Illustrative Shifting and Loading Dynamics (Pages 208 to 209) Example 10 (Shifting weight): Moving 50 tons a distance of 98.4 feet Aft to Forward. Trimming Moment: 50×98.4=4,920 foot-tons. Change of Trim: 4,920/820(MT1)=6 inches total, or 3 inches at each end. Result: Forward draft increases by 3 inches; Aft draft decreases by 3 inches. Mean draft remains constant. Example 11 (Loading weight): Loading 82 tons at 160 feet Forward of the LCF. Trimming Moment: 82×160=13,120 foot-tons. Total Trim: 13,120/820=16 inches (8 inches per end). Parallel Sinkage: 82 tons/40 TPI=2 inches. Physical Truth: Final drafts are calculated by applying parallel sinkage to both ends, then applying the trim change (additive Forward, subtractive Aft). II. Multiple Weights and MT1 Derivation (Pags 209 to 211) Example 12 (Multiple Discharges): Managing three weights removed from different longitudinal positions relative to amidships. Parallel Rise: Total weight removed (160 tons) ÷ TPI (40) =4 inches rise at both ends. Net Trimming Moment: Calculated by summing Forward moments and Aft moments to find the resultant force. Example 13 (Empirical MT1): Using the formula MT1=k×(TPI)2/B. For a vessel with a block coefficient of 0.75, k=30. MT1 is calculated as 30×(40)2/50=960 foot-tons/inch. Example 14 (First Principles MT1): Calculating MT1 using the moment of inertia (I) of the water plane. 1. BML​: I/∇ (Moment of Inertia ÷ Volume of Displacement). 2. KML​: KB+BML​. 3. GML​: KML​−KG. 4. Final MT1: (GML​×Δ)/12L. III. Forensic LCG and Trim Tables (Pages 211 to 212) Example 15 (Determining Light Ship LCG): Working the LCG Method backward using observed drafts. Trimming Moment: Observed Trim in inches × MT1. Trim Arm: Trimming Moment ÷ Displacement. Physical Rule: Since G is always between B and the deep draft end, the trim arm is applied to the LCB to find the Actual LCG from the After Perpendicular (AP-G). IV. Practical Case Study: Log Loss and Simultaneous Equations (.tif 212–214) Example 18 (Operational Truth): Determining the weight of cargo lost overboard during a trans-Pacific voyage. 1. Step 1: Use observed arrival drafts to find True Trim and displacement. 2. Step 2: Calculate the arrival Actual LCG by applying the Trim Arm to the LCB (referenced from Midships). 3. Step 3: Identify all known weights (Light ship, fuel, remaining cargo). 4. Step 4 (Simultaneous Equations): Solve for the unknown weights at two specific longitudinal positions (Hatch 3 and Hatch 4) using Equation 1 (Total Weight) and Equation 2 (Total Longitudinal Moment). Figure 9-10: Illustrates the relative positions of Midship B and Midship G. Figure 9-11: The Theory of Moments form used to isolate the weight and moment of the lost cargo. Produced by William E. George and Powered by Google's NotebookLM. Become a supporter of this podcast: https://www.spreaker.com/podcast/stability-trim-for-the-ship-s-officer--4180737/support.