A centerline structure running the length of a ship and fastening the transverse members of the floor to the keel below.
- ‘The ribs would have been treated with steam so that they could be bent sharply over the keelson.’
- ‘‘A few short ribs at the bow and stern will be fitted later when the new keelson is in place,’ said John Steer, one of the committee members.’
- ‘When we found she could sail in stronger winds, we fitted a stronger mast and rigging and, later, a keelson, an internal timber spanning three frames.’
- ‘One of the main uses we have made of it is for the keelson which required a piece of wood 6.7m in length.’
- ‘There was no central keel in the hull, but a large extruded central keelson was used.’
Middle English kelswayn, related to Low German kielswīn, from kiel keel of a ship + swīn swine (used as the name of a timber).