Argonauta stress fracture triage

I'm looking at an Argonauta long distance. There's what appears to be stress fractures on the pivots at the main hull. I posted a picture of the worst one. Three of the four show cracks. The picture is of the port aft pivot at the main hull.
Does anyone know anything about how that would have been constructed and what would be required to repair it?

 

Another picture

 

It is difficult to tell from a photo if it is a stress crack or simply old gelcoat cracking. What is the rotted piece of wood on top?

 

I am sorry, but I don’t know what the pivot is even to start to say much.

But.

Grind the gelcoat away and/or assume the worst. If the substrate beneath is rotted; it could be extensive work to remove all the rot and then reglass the structure.

Based on the other visible rotten wood; the least common denominator here is that.

 

I think the wood is part of the pin assembly. I'll try and get some additional detail. I'm relying on pictures the seller provided.

 

The rotten piece of wood is a diy replacement for the cap preventing water flowing into the pipe. You can see the original cap just to the right, the brown thing on top of the aluminum pipe with the line wrapped around it. It's also cooked and has to be replaced.

As to what it is, you are looking at part of an ama pivoting system that works like a barn door hinge, the pipe is the pin.

As for the cracks, it depends, there are several methods possible. I would grind the raised boss completely, enlarge the hole, insert a new thicker fiberglass tube, fillet and generously patch over the fillet with biaxial cloth. Then cosmetic filler and paint.

 

I am not sure what you describe as a pin. A pin is a small diameter bar. Do you refer to the rudder stock?

 

No, I refer to the hinge pin. We are talking about a folding trimaran, what you see in the photo is part of the hinge that allows the outrigger float to be folded parallel to the main hull. The hinge pivots are made from pipe.
The aka has holes on both ends, the ama has a pipe sticking up that fits trough the hole in one end, the main hull has two cantilevered supports for the pipe at the other end.
Here some pictures of the boat, you can find others online. Restoring a Newick Designed Argonauta Trimaran https://smalltrimaran.co.uk/restoring-a-newick-designed-argonauta-trimaran/