A keel also provides weight low under the water to lower the boat's center of gravity below the waterline, which is needed so that the boat bobs back upright if knocked over by wind or waves.
The center of mass will immediately produce a force that swings the aircraft back to its position directly below the fulcrum, just as a pendulum or keel would.
大规模的中心会立即产生波动的力量，飞机回到自己的立场正下方的支点，就像一个钟摆或龙骨会。
3
KEEL - main structural tube that runs along sail at center chord of wing.