Unlike Hais, Hamel pipe was too stiff to be coiled in a ship's hold, as it could not withstand the twist along the longitudinal axis that came with each turn of the coil.[25][26] The Petroleum Warfare Department proposed that it be wound around a buoyant steel drum that could be towed by tugs or fitted on a Hopper barge.[16] The resulting steel drum was 60 ft (18 m) long and 40 ft (12 m) in diameter,[25] and was known as a "Conun" or "Conundrum". Tests were carried out in the Froude tank at the National Physical Laboratory to verify that Conundrums could be towed at speed without yawing.[26]