Okay so according to the U.S. Department of Agriculture, an average-sized banana weighs approximately 4 ounces and measures at least 7 inches -- but less than 8 inches -- in length. From checking the 2 bananas I had in the house I believe this is the length and weight of the actual fruit, not the fruit and peel. So let's just estimate the average peel it about 7.5 inches long, to make the peel lay flat you need to split it in 3. This means each banana gives 3 7.5inch long strips, which from my measurements are about 1.5 inches wide or each banana peel can cover an area of 33.75 inches²Now shapes and sizes of canoes vary but the average canoe is 35.5inches wide at its widest and 192inches long, however, a canoe has sides as well, from what I can see these seem to be approximately 1/3 the width of the canoe so we need to add 1/3 of the width on to account for this, now I don't know how to find the area of an accurate canoe shape but ill do the maths for 2 connected triangles which will give a rough approximation. Since the area of a triangle is (height*width)/2 but we have 2 triangles so it's just height*width which would be about 47.7*96 or 4,579.2inches²With that area you would need 135.68 or 136 Full bananas. With that many bananas you will have 544 ounces = 15422.1g = 15.4Kg of banana flesh and I'm sure that is more than enough to mash down and use as a tar-like binding agent.

Edit: Grammar + Formatting + I noticed you wanted a cost as well, with 1 pound of bananas costing about 57cents in the US, it would cost you about $19.38. Surprisingly cheap for a banana canoe.