Pvajko and Skygazer, Thank you for your kind words of support.
In the case of a wooden boat, I would think that a fin or a full keel would sustain more damage than a glass boat, but the fin keeled boat would always be more susceptible to damage than a full keeled boat. That is just basic physics.
As far as the Westsail 32 you helped build with concrete and scrap steel, 95% of these boats left the factory with the ballast installed (this is from the general manager of the factory at the time)
Unfortunately you have contributed to building a not so desirable Westsail 32 ..what a shame as the boat is potentially a great cruiser.
Starting from the bottom up, I agree with you entirely about the Westsail 32 with the concrete and scrap metal ballast and specifically said that to the fellow building the boat at the time. I tried to make the case that the Westsail started out with less ballast than the Eric which it was patterned after, so going to a low density ballast made less than zero sense. He claimed that he had sailed on one and talked to "A bunch of guys who were building their Westsail 32's that way, and they sailed fine." I'll take your word that these other not so desirable Westsail 32s were a rarity. But that is another story.
Getting back to the original topic, as you acurately note, due to the physics of the situation either a wooden boat or a glass boat with a fin keel will potentially experience much higher stresses in a grounding than a full keeled boat.
One of the clear advantages of a full keeled boat with external bolt-on ballast is that the ballast takes the initial impact and spreads the load over a much larger area of the boat's structure. Because the ballast is comparatively low aspect, and placed outside of the structure, the forces imparted into the hull and fastenings are predominantly in compression and sheer, which is what conventional boat building techniues can absorb best.
The stresses on a fin keel are higher in part because of the greater lever arm of the keel, but also because of the smaller contact are of the fin limiting area within which the connections need to be made, and so the fastenings work at an inverse mechanical advantage. Not an inherently good thing.
The higher stresses of the fin keel, require much more careful engineering and construction techniques if the same margin of safety is to be achieved. (This was in part why I said that properly engineered fin keeled boats are typically more expensive than a simialr strength full keeled boat.)
But that does make any specific fin keel automatically weaker than any specific full keel. Properly engineered, the fin keel needs to be design to equal or greater safety factors than the full keel design intended for the same purpose. That means designing an internal structure and fastening scheme which can safely withstand the fin keel's greater loads, and distribute them over a large enough area of the boat that damage is not incurred during its service life.
In my mind the problem with discussing this in the abstract, vs analyzing this in the specific, is that for the most part, the majority of fin keel boat whoch have been built have been aimed at the racing, coastal cruising and value oriented communities. These boat have purposely smaller safety factors than boats intended for dedicated offshore passage making and cruising. By the same token, a much larger percentage of full keel boats built in recent years were designed with the intent of offshore use.
So, when this comes down to debating the strength advantage of a specific design feature citing specific boats, it is easy to suggest a range of examples of full keeled offshore cruiser that are way more robust than some collection of fin-keeled coastal cruisers, or more glaringly yet, compare dedicated offshore full-keeled cruisers to the strength of some dedicated race boat. But it gets harder to make the point when the same comparison uses dedicated offshore cruisers with fin keels that in theory have been designed to the same safety factor as any other purpose built offshore cruiser.
The same argument applies in the hull form debate as well. It is easy to say that a purpose built, offshore cruiser- no matter what its keel type, should have a more comfortable motion, more carrying capacity, and a more seaworthy hull form no matter what its size or displacement than would be expected on a dedicated race boat, racer cruiser, coastal cruiser, or even a boat designed to make occasional offshore passages.
Where these debates go off the rails is that comparasons are often made between purpose built offshore cruisers versus purpose built race boats, racer-cruisers, value oriented family cruisers and coastal cruisers and so on, when each may be well suited and optimized for their secific intended use and so do not represent a fair example for comparason on the issue being debated.