This cylinder would displace 100 liters of water. To keep it vertical you would have to find some way to keep its center of gravity below the water line otherwise it will seek a position of lowest energy on its side. This would probably involve adding more weight as ballast to one end of the cylinder. As it is stated the 100kg would require 1/4 of the volume of the cylinder to displace enough water to float it so you have adequate volume to support near 400 kg.
This cylinder would displace 100 liters of water. To keep it vertical you would have to find some way to keep its center of gravity below the water line otherwise it will seek a position of lowest energy on its side. This would probably involve adding more weight as ballast to one end of the cylinder. As it is stated the 100kg would require 1/4 of the volume of the cylinder to displace enough water to float it so you have adequate volume to support near 400 kg.
