Originally manufactured by an independent sub-contractor , the tanks were rivetted .
Originally manufactured by an independent sub-contractor , the tanks were covered with a resin sealing agent ; however , this technique would result in joints that would rapidly degrade in the presence of vibration .
Originally manufactured by an independent sub-contractor , the tanks were rivetted and covered with a resin sealing agent ; however , this technique would result in joints that would rapidly degrade in the presence of vibration .