Thing is that there is no way to repair the keel. The keel is the foundation for the ship. If it breaks or is removed the whole ship collapses. Even Franky who was raised by Tom said so and the Klabauterman was just able to do a touch up job on itself, not fully repair his damages.
Also, how the little broken ship was able to reach EL shortly after Rocketman and make it through Aqua Laguna is beyond me.
