Boat making noise

Its an old boat (1978) and Ive had her forever. Last weekend I was out with my son and on the way in the boat kept making a popping noise. It sounded like it was coming from the rudder assembly or the very back of the boat. We were going down wind and in light wind so the boat wasnt stressed. I couldnt "make" the noise moving the tiller or sails. It would just make a pop sound occasionaly. Like something was loose. On the trailer, the pylons seem anchored. The sound was not metallic in nature. Any ideas?

Maybe check the rudder gudgeon screws? could the rudder blades be loose in the castings? Check the hull to deck seams or for any soft spots.

That's all I can think of at this time.

Individual strands popping on the side stays?

I didnt notice anything when coiling the side stays do I dont think its that. I will check the gudgeon screws this weekend. I had a soft spot in front of a pylon but it never made this noise. Ill check the rudder casings too.

could be rocks too

When did Hobie start putting rocks in the hulls? My boat doesn't have any installed rocks. Can I refit my '77 H-16 with hull-rocks? Do I have to use Hobie rocks to be class legal, or is it OK to use after-market rocks? Does Rick plan to sell hull rocks on Catsailor.com? I'd prefer to give Rick my business!

I took the boat out again and not a peep. The only thing I can think of was the rudders bumping fish as they had been schooling in the area.

Hey, what a great idea, putting rocks in hulls! Rick and I have an unlimited supply of rocks, because we live on rock islands both Key Largo and Put-in-Bay. No charge. Just come and pick them up off our lot at either place. PLEASE!
Usually we just put them into grapefruit bags to use as anchors for racing marks. Take your choice: coral rocks in Key Largo or granite rocks at Put-in-Bay.