Rivets for top mast plug

One of the rivets holding the plastic plug at the bottom of my top mast section has broken off. Can I replace it with a plain (lightweight) rivet, or does it need to be a stainless one?

David

There appears to be a fair amount of shear loading on the rivet, as mine also broke.

I replaced it with SS. No issues since then

SS works fine, but I believe (unsure; ask the hardware store guy) aluminum rivets work just fine, and they're a lot cheaper. The reason I question is because there's some metal that corrodes with something else, but I don't remember what.

SS have the greater tensile strenght but in this case AL might be sufficient. They are more expensive and harder to find in the right size but worth it for things such as cleats and equipemnt on the boom.

Don't worry too much about corrosion on your mast (unless you are on a salty environment). You'll likely bend your mast before you need to repace those rivet due to corrosion. In salty envriornment, it might be a different story... not sure.

Annie

Al does not have enough shear strength for this application.

One tip for the rivet. Try and have the rivet facing aft when you are rigging the boat. This will cause the mast to bend "onto" the rivet, not stretching out the hole.

TimClark said:

One tip for the rivet. Try and have the rivet facing aft when you are rigging the boat. This will cause the mast to bend "onto" the rivet, not stretching out the hole.

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That's good advice for the collar rivet, but this discussion is about the mast plug.

The uppers I have had don't have the rivets lined up between the collar and plug.

49208 said:

Al does not have enough shear strength for this application.

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How much of a shear load is on the plug?

It seems there is not that much, as the plug cannot move in the lower mast. (Depending on wear, I guess.) I also don't think there is much rotational force either.

What am I missing?

When the upper mast starts to bend, the foward portion of the plug is pushed against the forward wall of the lower section. As the upper bends further, the plug tends to lock in place while the aluminum tube is levered slightly up, off the plug. This is where the shear load on the rivet comes from.

If you tape your plug and collar for a tight fit, it can be a real PIA to get the upper off once the plug gets a little loose, as it will wedge itself in the lower because of the movement described above.

Mast bend and sail shape are also affected when the plug is loose in the upper and lower.