First find the area of the square sail: 5 inches * 8 inches = <<5*8=40>>40 square inches
Then find the area of a square sail with the same height and length as the first triangular sail: 3 inches * 4 inches = <<3*4=12>>12 square inches
Then divide the area in two to find the area of the triangular sail: 12 square inches / 2 = <<12/2=6>>6 square inches
Then find the area of a square sail with the same height and length as the second triangular sail: 4 inches * 6 inches = <<4*6=24>>24 square inches
Then divide the area in two to find the area of the triangular sail: 24 square inches / 2 = <<24/2=12>>12 square inches
Then add up the areas of all the sails to find the total amount of canvas needed: 12 square inches + 6 square inches + 40 square inches = <<12+6+40=58>>58 square inches
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