SS- It certainly needs reinforcing inside and out. There are some three functions that the area performs.
1. It has to take the loads on the forward keel bolt, both weight and impact.
2. It has to take the loads of the mast foot down force vs. the forestay leverage plus the hydromanic forces.
3. It has to keep the water out, despite having a hole for the keel bolt through it.
The Coronet owners club only talks about their stinkpots. The builder went out of business in 1977 - this was his last delivered boat. The subsequent builder of Mk IIs also went out of business in th '80s. A yard has looked at it and suggested replacing most of the hull, but I don't think he had time to take on the work.
Ocean - Its a 1977 vintage Coronet Elvstrom 38 (ft) the area affected is between the mast foot and the forward keel bolt.
The lead keel is below, the fibreglass hull above. I drilled that hole to check how deep the crack was below it. The crack goes all the way through, about 6 cm, to a corresponding crack on the other side. In other words, the base of the hull/keel mount is split across. If you look carefully, you can see the keel bolt, just aft of the hole. Note also the signs of repair attempts including angle grinder scores in the lead keel and the multiple flexure cracks in the anti-fouling above.
How thick is it? Well that is a bit difficult to judge from the repairs. I think the hull sides started at about 1 cm and the foot at about 2 cm - so I am not surprised at the failure. Obviously, I dug further.
Now you can see a previous glass+polyester repair. The crack was found to have travelled higher, so I drilled again to find out where on the inside the crack was. The upper hole is at about the backing plate level. After initial digging on the inside it looked like this.
I had to drill and chisel down through one layer of glass and 20 cm of resin to reach the keel bolt/nut. That bucket of resin had stiffened the area, but not enough. I don't have a later stage picture, but I chiseled out all of the resin, it had not adhered well to two further glassing jobs further down. OK found a later picture:-
Basically, the entire bending forces get concentrate on that stud and its tiny backing plate. It can hold it, but the surrounding structure needs to be stronger.
SD - If I used glass and then carbon, surely the carbon, being less elastic, would have to take all the load? So the stress would still be on the polyester to epoxy bond.