I put one of these "Swim Noodles" in a friends boat the other day.
His inflatable keel has been patched over and over, and then painted twice with the wrong coating. He was screaming at the price of a new one, and I have a bunch of these lying around.
I trimmed it to the length of the original keel, and then formed the ends with a bread knife to improve the fit & aquadynamics.
It performed surprisingly well, is material friendly, and took about 15 minutes to produce. It is not a stiff as one of the older wooden type keels, but it works, and also only cost about 2 Euros.