![]() ![]() The squared term means that the distance of heavy items from the Center of Gravity greatly affect the RMoI, and the greater RMoI the less the boat will react to a gust of wind, or a large wave. This is calculated by multiplying the weight of all the boat's constituent parts by the square of the distance from the boat's Center of Gravity to the part's Center of Gravity - a tedious but necessary task for the designer. It's the Roll Moment of Inertia (RMoI) that should concern us most as it's around the fore and aft axis that a boat is most likely to capsize. This is the measure of the boat's resistance to angular acceleration.īoats rotate around three axes - rolling around the fore and aft axis pitching about the transverse axis yawing around the vertical axis. There's no arguing that heavy displacement helps a boat's stability, but the most important factor affecting dynamic stability is its moment of inertia. How will it react to a sudden gust of wind or when clobbered by a large wave? Dynamic Stability The relationship between heeling angle and righting moment is different for all boats, and the plotted Gz curve gives an excellent indicator of the boat's static stability.īut the boat's static stability and its righting moment is only part of the story. As the boat heels past this point it decreases, leading eventually to a capsize. There comes a point at which Z reaches a maximum value, normally at an angle of heel of around 60 degrees or so. The Moment Arm (Z) is the horizontal distance between G and B, and the Righting Moment Gz is the product of the moment arm and the boat's displacement.īut whilst the boat's displacement and the location of its Centre of Gravity remain constant, Z changes as the boat heals more and more. With the boat upright, the Centre of Gravity (G) is in line with the Centre of Buoyancy (B) effectively there is no righting moment.īut as the boat heels, a righting moment develops. Righting Moment created as the boat heels
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |