EXPERIMENT 2 BUOYANCY FLOTATION METACENTRIC HEIGHT PART 2

EXPERIMENT (2) BUOYANCY & FLOTATION (METACENTRIC HEIGHT) PART (2) 1 By: Eng. Motasem M. Abushaban. Eng. Fedaa M. Fayyad.

PURPOSE: To determine the metacentric height of a flat bottomed vessel in two parts: PART (1) : for unloaded and for loaded pontoon. PART (2) : when changing the center of gravity of the pontoon. 2

EXPERIMENTAL SET-UP: The set up consists of a small water tank having transparent side walls in which a small ship model is floated, the weight of the model can be changed by adding or removing weights. Adjustable mass is used for tilting the ship, plump line is attached to the mast to measure the tilting angle. 3

Remember: - Pontoon dimension : Depth (D) = 170 mm Length (L) = 380 mm, Width (W) = 250 mm. - The height of the center of gravity of the pontoon is OGvm = 125 mm from outer surface of vessel base. - The balance weight is placed at x = 123 mm from pontoon center line. - The weight of the pontoon and the mast Wvm = 3000 gm 4

PROCEDURE PART (2) : when changing the center of gravity of the pontoon. 1. Replace the bilge weights by 4 x 50 gm weights. 2. Apply a weight of 300 gm on a height of 190 mm from the pontoon surface. 3. Apply weights of 40, 80 &120 gms on the bridge piece loading pin, then record the corresponding tilting angle. 4. Calculate GM practically where 5. Draw a relationship between θ in degrees (x-axis) and GM Practical (y-axis), then obtain GM when θ equals zero. 5

PROCEDURE 6. Move 50 gm bilge weight to the mast ahead, then repeat steps 3, 4&5. 7. Repeat step 6 moving 100, 150 & 200 gm bilge weight to the mast. 8. Determine the height of the center of gravity for each loading condition according to equation 6

7

8. Calculate GM theoretically according to equation GM (Th. ) = BM + OB – OG Notice: BM & OB are constants for all loading conditions, since the dimensions & the weight of pontoon do not alter. 8

Table (2) Part (2) Off balance wt. Mean Def. Exp. GM BM OG Theo. GM P (gm) θ (degree) (mm) Mast Weight = 0. 0 40 2. 40 80 4. 88 120 7. 50 Mast Weight = 50. 0 40 3. 45 80 7. 23 120 10. 50 3. 28 40 6. 35 80 12. 00 Mast weight = 100. 0 20 Mast Weight = 150. 0 10 3. 70 20 10. 23 40 14. 78 Mast weight = 200. 0 Unstable 9

10

11

QUESTIONS 12