How to reattach this block to mast

[workmaster2n]

I just purchased a new to me vessel, and on the sail up the coast to the haul out location, this block popped out of the mast (it is the block for the screecher halyard). Luckily the previous owner noticed before the halyard chafed through and we dropped the sail.

I'm having a hard time getting a rigger or shipwright to attend and I return to the boat in a few weeks. It looks like I might be going up the mast to fix it myself.

How are these blocks usually held in? I feel a pop rivet wouldn't be strong enough? Perhaps they are usually screwed into a tap on the mast?

My hope is that the hardware that held the block in place corroded away after 16 years and I can simply reattach the block. My fear is that the mounting bracket in the mast got torn out.

The boat is in a small town, so just trying to proactively think about what I might need to source before I get out there.

[Tin Tin]

So this is a catamaran rig? Normally the screecher/spinnaker halyard would exit well above the forestay fitting, even the mast top and then pass down through a swing block just above the forestay attachment. This means the halyard force on the exit fitting would down the mast so all the rivets would do is hold it in place. If the sail is allowed to fly direct out of the sheave it will put sideways force on the fitting. Whichever way you will need to go up take a photo and figure if next size up rivets or even stainless rivnut (with tefgel) would be better.

[workmaster2n]

Originally Posted by Tin Tin

So this is a catamaran rig? Normally the screecher/spinnaker halyard would exit well above the forestay fitting, even the mast top and then pass down through a swing block just above the forestay attachment. This means the halyard force on the exit fitting would down the mast so all the rivets would do is hold it in place. If the sail is allowed to fly direct out of the sheave it will put sideways force on the fitting. Whichever way you will need to go up take a photo and figure if next size up rivets or even stainless rivnut (with tefgel) would be better.

Yea, she is a catamaran.

Interesting point about a swing block. When we lowered the sail, this (what I now think is called a sheave box) came all the way to the deck, which would seem to indicate that there wasn't another block attached between the head of the sail and the sheave box.

I know the previous owner did thousands of sea miles with this setup, so that feels a little strange. Perhaps the swing block broke and put tension on this sheave box, which could explain why it popped out.

I'll definitely have to look into what kind of swing block there was up there.

Thanks for the pointers!

[steve77]

I have used stainless heli-coils to repair threads on a mast. I've never tried the riv-nuts, but heli-coils work fine for thread repair.

Cheers!

Steve