It was necessary to load the timbers on a ship because the raft was not strong enough to survive the choppy Hyuga-nada and Genkai-nada Seas, which they had to sail across on their way from Kagoshima to Kinai region.
鹿児島から畿内までの航路には波の荒い日向灘や玄界灘が控えており、筏のままでは強度が不足するため船に乗せる必要があった。