I have a 1980 Catalina 27 and am going to put in two additional keel bolts just for good measure. The current pattern of the bolts is 1-2-2-1. The bolts are 5/8" stainless. I'm planning on putting them right in between the center two sets of two bolts and will place them side by side. The bolts will be windowed(as opposed to lagged) at the bottom end and will have dowel nuts, if I can find them, or, I will stack a few stainless fender
washers and use stainless hex nuts.
I have read elsewhere that because of using the window method I should stagger the depth of the bolts or slightly stagger the fore/aft placement of them. Anyone have any thoughts on that?
In drilling the vertical holes, I am planning to slightly oversize the first 3/4 of the total depth in the lead and then drill a 5/8" diameter hole the last quarter. I would then fill the hole with thickened epoxy
and also fill the window with thickened epoxy
I am planning on 12" bolts which would allow 9" into the lead.
As far as the existing bolts go I'm planning on inspecting a couple of them by drilling a small diameter hole parallel with and tangent to an existing bolt, down to the lead. I should be able to see the condition of the threads with this inspection boring.
Just FYI this is a catalina that had the 1 1/2" of plywood in the keel stub. I have eliminated that and epoxied in 6 layers of 1708 glass. When I ripped out all the plywood the existing bolts were in perfect condition down to the bottom.
Anyone see any concerns or have anything to add that would help?
Thanks for any input.