Tabernacle fasteners

[HvB]

I am installing a tabernacle on a DS-II and need to decide what fasteners to use to connect the mast to the aluminum casting seats. Galvanic corrosion is not an issue because of a freshwater environment. The options seem to be 1) to drill and tap for SS machine screws, 2) use aluminum rivets or 3) use SS rivets.

For machine screws I was thinking 3 or 4 screws, for each seat, either 8/32 or 12/24. This would make it easy to remove the tabernacle if needed and be very strong. At the same time, the screw heads may require a little bit of filing on the edge of the mast partner to create enough space. Furthermore, the strength of the screws could cause expensive mast damage in case of a shroud failure if the edge of the tabernacle seat did not break off.

For rivets I was considering four 3/16" rivets on each mast seat with a grip of 1/4". This would eliminate the space issue in the mast partner but raises the question of aluminum vs SS from a strength perspective, especially when lowering and raising the mast and encountering some sideways motion.

Any thoughts will be appreciated. Maybe there is a standard way of accomplishing this that has worked and I am making it too difficult.

Thanks.

[GreenLake]

My thought is that aluminum rivets are the way to go. They are plenty strong on shear, but, as you point out, when the mast comes down, they will not the be the strongest point.

For ordinary mast raising, they should be strong enough.

You may be using some mechanical advantage when you raise your mast (I don't know), but it is possible to raise a mast by main force. If you think about it, raising the mast (or holding it at an angle) creates two forces, one in your hand and one on the tabernacle. They are equal and opposite, but offset. This creates a moment that's opposed to the moment created by gravity acting on the center of gravity.

As a result, what those rivets have to be able to hold is similar to the force you apply to the mast where you push at it. Even with a good safety factor, aluminum rivets should be up to it, if you choose the correct grip.

[HvB]

Thank you green lake. Your reply was much appreciated. Tomorrow the aluminum rivets go in.