Lewis knew his Expedition would travel the continent by water but did not know the size of these future waterways out west. He designed a modular boat for Harpers Ferry to make. On April 20, 1803 Lewis tested his experimental steel frame boat. He was delayed a month, waiting on the completion of his design of the steel frame. From his letter it appears that the final frame might never work, but his letter notes that he would try it on the Expedition. His crew hauled the steel frame, which was probably 250 to 350 pounds all the way to Great Falls, Montana (3,500 miles) where it failed to float due to no availability of pine sap to seal up the seams of the deer hide.