I'm not familiar with how Hunter built their boats, so I may be off base here. The crack does not appear to be in the rudder post, it looks more like the rudder bearing or the tube the rudder bearing sits in has broken loose from the hull.
Yes, the question is what are the materials on each side of that crack? But if you look carefully at the photos, it appears both sides of that crack may be the same material. But you may well be right, could be one side is fiberglass.
If this were my boat, after haul out, I would drop the rudder and inspect the rudder post. Then I would clean up all the gelcoat/paint around the crack and see what's there. Getting a copy of the original shop drawings would be helpful.
I definitely agree with you here on several points, but I'm not sure I'd drop the rudder first.Shop drawings would be really useful! The problem in my mind w.r.t. dropping the rudder first thing, is currently everything is in alignment. If you can get everything cleaned around that, open up the cracks so you can then fill with epoxy, you'd keep everything aligned. Then you could drop the rudder and inspect everything else, like the lower bearing surface, rudder etc. It seems to me if you dropped the rudder first, you'd have a job making sure the bearings are all aligned in reconstruction. Now, I'm assuming this has a top and bottom bearing.
The rudder tube and bearing assembly is not something to mess around with. JB Weld would not be my product of choice. It may be fine for other applications but this is not one of them.
+1!!!
Since the joint has broken, it means one of two things, the joint was subjected to some kind of trauma, like a rock, or it was under built in the first place. Get the rudder out, clean up the area to see what you have and send us new photos.
It may also be a poor weld joint; bad weld, incorrect filler material, residual stresses during welding, etc. That is, if the bottom side of that crack is also aluminum. Images 4 , 5 and 6 sure seem like aluminum on both sides of that crack.
If it is fiberglass, then what broke? How did they adhere this aluminum to the fiberglass? I would be skeptical it was under designed, unless that is the only bearing and there is not another one lower down. Then you would be spot on!
dj