So I want to beef up the area where the tunnel tubes meet the hull plating so I am installing a doubler flange on each penetration. I had cut the tubes so they extended roughly 1/2 inch past the hull plating on each side. I then took some 3/8 inch thick plate and cut an elliptical doughnut ring. The inner ellipse is 15 inches wide but 17 1/2 inches tall for the forward tunnel. The stern tunnel is canted back even farther so that ellipse is still 15 inches wide but 18 1/2 inches tall.
Here is a picture of the finished port side forward penetration –
And from another angle –
I debated whether to remove the TC bolts in the flange area and then bolt through the flange through the same hole in the hull and frame. Instead, I just cut the flange plate around the bolt heads and welded them into the flange.
It is nice that these flanges overlap the frames underneath – that will make it much stronger in case I was to take a hit in this area.
Here is the starboard side forward penetration –
Next is to do the same process with the stern tunnel and make some sort of guard to keep flotsam from clogging the propellors.