Mast step sinking?

[Dieselmech]

Hey all.
I have recently had my rig tensioned by a rigger who noticed the rigging was tensioned almost all the way on one side. There are a few things to consider here
1. The bushes at the top of the mast where the rigging attaches to the mast are noticably worn.
2. The cabintop/deck seems to have a small sink in it on one side. But no cracking.
The mast is deck stepped but the core inside the step seams to have a solid tone and there is no cracking of the fibreglass.
The compression post all seems to be sitting straight and not sinking into the floor.
Is there anything I/we may be missing here that I/we should check before pulling the mast and opening up the step?

[skipmac]

Lots of potential variables that could be causing this so some more info might help.

How long have you owned the boat and how old is the rigging? When new did the rigging have lots of adjustment left so has the rigging gone from plenty of adjustment to none or was the rigging originally cut a bit long leaving little room for tension?

If there is no adjustment left on one side how much is left on the other? Maybe the mast is adjusted to one side.

Is the depression in the deck obvious where the mast sits on the deck?

Have you checked the bottom of the compression post where it sits in the bilge? Any chance the post has sunk down due to rot or sagging there?

When you refer to the bushes at the top I'm guessing you mean the tangs, flat stainless stock with a bend that bolts to the mast on one end and has a hole on the other end for the rigging pin? How elongated is that hole?

Could be a combination of all these: a little slack from the worn tang, rigging cut a little too long, stretching with age and a little depression at the step all adding up. Plus if the rigging is more than 5-7 years old most experts recommend replacing regardless of how it looks.

[Dieselmech]

I have owned the boat since November last year. There is a fair bit of adjustment left on one side . There is no history on the rigging age. It is a catamaran and the post doesnt seem to have sunk but i suppose if it had sunk a tiny bit it would be hard to notice. The hole on the tangs are elongated quite a bit.

[Suijin]

Originally Posted by Dieselmech

The hole on the tangs are elongated quite a bit.

Well that sounds like your culprit right there. Did the rigger render an opinion on whether it was enough to be responsible?

Over tensioned rigging can be just as bad as under tensioned when it comes to potential for damage.

[skipmac]

Did not understand that the boat is a catamaran. With the mast stepped in the middle and the shrouds running to the outside of the hulls is it possible the hulls are pulling up a little when the rigging is tensioned.

[chris95040]

Originally Posted by Dieselmech

The hole on the tangs are elongated quite a bit.

I agree with other's that this is important. Probably time to replace those, other folks will know better than I but I think the danger there isn't just about the elongation, it's about the resultant work-hardening of the stainless that the tang is made of. Maybe go a higher gauge with those tangs.

But here's another question. Are you sure the mast is perpendicular to the boat's horizontal? Maybe the mast is perfectly vertical, but the boat is listing a bit. Or maybe the boat is perfectly horizontal, but the mast is not perfectly vertical. In these cases, simply shifting some weight around in the boat, and then adjusting your rig to take up on one side and let up on the other would rectify this.

[Dieselmech]

Thank you all for the responses.
I contacted the boats builder and they responded with "The mast step area (on the deck) should not have a core. There is a piece of aluminum between the deck and headliner and the rest should be solid glass." If this helps at all.
I also asked them what is under the compression post so I can be sure nothing is rotten underneath there.
When i run a straight edge across the deck near the mast step it does seem to have sunk a little as shown in photos.
So im thinking its a combination of all these things.
Maybe i plan to pull the mast, reinforce/shim the base of the compression post, replace the tangs, replace the rig and reseal the step.