I have a 13 ft. whatewater kayak, it has a good rocker on the bottom, which makes it harder to track but great to turn into an eddy on the river. The first 2-3 times in it, it was impossible to track with, but by the 4 th time out and several hours i can do a straight line in a river or pond. but if you're determined to put a keel on it, which i had thought about after the 1st time out, here is what i had considered. We were going to sand down thru the gel coat to the resin and cloth and run a 1/2 inch lenght of rope saturated with resin. then cover with a strip of cloth. the materials could be bought at any dept store, in the automotive section. i've used this to do patches on my yak ( whitewater has a tendency to put holes in fiberglas boats). you can get a kit for under $20. steve