OK, I dug through here, but couldn't find the answer to this question(maybe I gave up too soon). Is there a way to scrap a few ships on purpose??

Example:
Once you get built up enough to start using large cargo ships, is there a way to get rid of your old small cargo ships once you have built replacments for them??

Nothing efficient. The only option is to send them at someone and rec the DF, but most people just keep the ships. Might as well.

I have to admit, I have sent my fleet crashing into a wall of defenses before to recycle the DF.

you could always send them all on an expedition, if you run into a black hole, ships are destroyed and you dont have to worry about them.. or you might find extra resources or more ships