Update 28 Jun 17:
The Sunfish coaming or splashguard is held on to earlier models by machine screws and riveted nuts (rivnuts) or by rivets on later models. you can tell by whether there is a slotted screw head or a rivet head. Sometimes coamings come loose, leak, are broken or need to be removed for repair and restoration. Here is a Sunfish damaged by Hurricane Sandy, it has rivets that you can see in the coaming remnants and fractures around the deck holes where the rivets pulled out.
Here is a Sunfish that has clean rivet holes on the deck. The owner is cleaning up old silicone and a makeshift screw and wall anchor repair.
Rivets can be purchased from a Sunfish parts house like
Yankee Boating Center and installed with a rivet gun, available from your local hardware store. The demonstration holes in this piece of particle board are 1/4 inch.
The rivet is inserted into the gun and then the barrel is placed though the coaming into the deck hole.
Squeeze the rivet fun handle, keeping rivet flush against surface. As the rivet shank is pulled the barrel will expand inside the hole. Continue to pull the shank until it snaps under pressure or will pull no further, gently rock rivet gun back and forth to shear top of shank if needed.
Here is comparison of a pulled rivet on the left vs new rivet. You can see how the barrel is shortened and expanded, filling the hole. It will expand below the deck on a Sunfish and anchor the coaming, the collar of the rivet holds on the top and the expanded barrel holds on the bottom.
This is what the rivet looks like on top of the hull and inside the hull.
1960 to mid 70s boats had closed end rivet nuts (rivnut) and 10-32 x 3/4 inch stainless steel machine screws to attach the coaming. The rivnut had a small bead of sealant that prevented water from leaking inside the hull.
Closed end rivnut seen from inside the hull.
If the screws are frozen, soak them with penetrating oil for a few days. Give them a few light taps with a screwdriver and hammer. Tighten slightly then back them out.
1st Gen splashguard.
2nd Gen coaming aka "The Mustache."
