I know the basic answer....plug one end of the keel, fill with sand, plug the other. I've done it before, but the calk that I used to seal the ends didn't hold very well.
So my question is: what is the BEST way to seal off the ends? What is the best calk?
Also, I have a few decoys that have cracks and need repair....what have you found to be the best "glue" to seal off these cracks?
Thanks in advance.........

We used a chunk of stainless rod and silicone. The stainless rod was handy but any old weight will work.

Throw them away and buy weighted keels.

How about expandable foam?

We have used Gorilla Glue over a piece of paper wadded up on one end till it set up. Flip over, fill with sand and a few pieces of wheel weights, then piece of paper and Gorilla glue over that. Rough up inside of keel with sandpaper first for guaranteed bond.