Rivets for mainsail track and spreader brackets

I completely stripped the mast on my BCC because of some surface corrosion that I wanted to address, and to make it easier to paint. I popped the rivets out on the mainsail track and also the spreader brackets. Does anybody know what kind of rivets I should use to replace the old ones? I heard Monel was a good option. What are the other options? If I do stainless, what kind of coating do I need to put on the rivets? How do I to go about getting the right size rivets? What else do I need to know?

The mainsail track holes are 3/32 size drill bit and the spreader rivets are 3/16 size drill bit. Thanks in advance.

We used monel rivets for some hardware and SS machine screws for other hardware when we fitted out BCC Calypsos new Selden mast. Use TedGel on everything (including rivets). Even so, long term, I think you need to accept that you will eventually develop some corrosion blistering under the paint originating from fastener holes. It just seems to be an unavoidable eventuality with painted masts.

The original Forespar masts had an integral track for mainsail slides and an external SS tee track for the trisail.

In your case, I would aim to replace using the same size fasteners as the original unless you came across evidence of hardware pulling away possibly caused by undersize fasteners. It’s just easier and faster to not reengineer when restoring a boat unless there’s a compelling reason to do so.

Rivets come in metric and standard sizes. They also come in various depth sizes. Generally speaking, there is no harm in using a rivet with more depth than you needed as the shank is going to pull in and finally break when the actual clamping distance is reached. Use a heavy duty two handle rivet gun - not one the plier like things.

Do hammer out and collect the mandrels as they are commonly carbon steel and will bleed rust if you don’t remove them. You can use a large magnet to remove them from inside the mast while it is on saw horses, or they will hopefully all rain out of the mast as it’s lifted for stepping. It’s obviously easier to get them out before the mast gets fully stepped.

Cheers - Jeremy

Okay, this is very helpful. Do I need to paint the mast?

I’m sorry that I have to differ here. I have a background in material science, and advice to use a more noble metal for fasteners is not good advice. Whenever possible, you should use the same metal for the fasteners as for the fittings.
Of course, this is not always possible. If your track is stainless steel, for example, use stainless steel fasteners. If your track is aluminum, if possible, use aluminum fasteners. In general , monel is almost never the best choice, because it is more noble, that is higher on the galvanic series, than almost everything else. This means that the Monel will not corrode, but it will encourage corrosion in all the metals around it.
Materials like teflon paste and gel reduce corrosion by displacing water from the interface between dissimilar metals, so use them also.
For aluminum track, use all aluminum rivets. You must be sure that the pin in the center of the rivet is also an aluminum. Some aluminum rivets have a steel center pin. You must be sure that the pin in the center of the rivet is also a aluminum.
By the way, the same considerations apply to anchor chain and fittings. If you mix stainless steel and galvanized, the stainless steel will accelerate the loss of zinc in the galvanizing. This means, for example, that seizing wires on galvanized fittings should be galvanized wire, as opposed to stainless steel or monel. I expect to get a lot of disagreement on this, but this is the science of it.