I finally found a source for rivet casings. They can be used for shimming an enlarged pop rivet hole or waterproofing a new pop rivet. See the attached photo if you don't know what they look like. Rick's store doesn't carry them.

Murray's Marine does carry them. Rivet Casing 6-10 (3/16 x 1/2) Part #19-5020 $.70 each.

Great find! Wondering how they work do you cut them to length then rely on the pop rivett to pull them tightly into place or do you have to knock them flat from underneath? What are they made of? and are they strong enough for a mast?
regards

You just put them into the hole before the rivet goes in. Cutting them would defeat the watertight purpose.

They are commonly used on masts to help seal the pop-rivets used for all the fittings.

They're a very soft aluminum. Just put them in the hole, insert the rivet and set it.

Great idea. I wonder if they're available in Oz?

I asked Matt Miller of Hobie what their source was. he said they used a speciality house and bought them in quantities of 100,000.

I'm sure that Murray's would ship international. It would pay off to order a large quantity as they weight next to nothing and split them up among all your sailing friends. Murray's might even cut you a quantity discount.

Your might also contact Hobie Australia to see if they carry them and be open to selling small amounts.

I don't believe they're aluminum. Monel most likley.

Ill take some Berny just contact me if your interested in getting a quantity
regards