The keel, with the floors of the frames and the bottom longitudinals, form the cellular structure extending about two-thirds the length of the hull known as the double bottoms .
Isiseko senqanawa, sikunye nemigangatho yezakhelo kunye nezide zemiphantsi, zenza isakhiwo esibuselula esanda kangangesibini kwisithathu kwaye ubude besiqu senqanawa baziwa ngokuba ngamaqhosha aphindaphindeneyo.