What are the best methods to measure the heel angle and the shift of weights during an inclining experiment?

Points to remember: 1. Inclining experiment is done when the vessel is newly built or has undergone major structural changes. 2. The vessel should be upright. 3. Provide sufficient slack in mooring ropes so that the vessel could easily heel and the gangways should be lifted. 4. Ensure there are no loose weights aboard. 5. Conduct the experiment in calm water. 6. Record the draft and density prior to the test. 7. Only people responsible for conducting the experiment should be on board.

While ideally the ship should be in the closest to 'lightship' possible; that is not always possible, especially with ships which have undergone modifications which have changed weights or CG's more than 5%. 'Lightship surveys' can be done to adjust the actual displacement to the lightship condition - it's tedious and requires a team of personnel who can size up the mass and location of an object without resorting to scales. Same goes for the crew - it's OK for non-essential crew to be onboard (especially if there's no facililties for them otherwise) - their weights can be adjusted like other loads onboard; they just need to be reminded often that during the inclining test it is ABSOLUTELY essential they stay where they are assigned.

In a shipyard, finding weights for inclining is relatively easy - concrete blocks are the norm. If you are called to perform an inclining test at a lay berth, talk with local crane operators (you're gogin to need them anyway) - they often have welded steel test weights or concrete blocks for load testing. As long as the test weights have flat bottoms or dunnage can be placed under the blocks to prevent sliding, they are sufficient. Locating weights is often done by assigning the weight to a deck - that gives your vertical location. Establish a centerline on the deck for transverse location and mark major frames to establish longitudinal location. If you're moving 10 tons 5 meters, you don't care about the millimeters - they're noise.

The weights should be sufficient to provide a heel between 2-4 degrees. Any deviations from this range will result in inaccuracies. Typically, concrete blocks of equal weight are employed for this purpose.

Traditionally, the angle of heel has been measured using pendulums with the longest arm possible. Some things to remember when setting up this 'traditional' method: 1. Outside disturbances will throw off the measurements. The pendulum should be proected against outside influence - position in a protected space. 2. Choose your dampening fluid carefully. Oils are traditional - but an environmental headache. Liquid soaps work. 3. Longer is better. The deflection will be easier to measure if the swing is long. 4. Longer also means wider - make sure you account for that with your dampening trough and makring board. That said, we now have access to MEMS accelerometers/angular rate sensors. Should allow more varied measurement means.

KM is derived from the hydrostatic curve for that particular condition of the vessel, following the computation of the vessel's GM. The difference between KM and GM yields KG, ie, KM-GM=KG. Consequently, the vertical center of gravity (KG) for that particular lightship condition is determined. This KG value remains applicable for computing stability parameters across different loading conditions.