“Stronger” doesn’t tell the whole tale and it would be interesting to know what sort of boat
you consider to be the best fin keel
If you’re talking about even the best high aspect fin, there’s no getting away from the tremendous concentrated forces that the combination of a long moment arm and a small cross section yields. I’m sure you’ve seen these boats with the aft part of the keel
rotated right up into the hull and cracking it like an eggshell. Some end up on the bottom shortly afterward but some make it to a nearby boatyard and are repaired at great expense. Ive seen these hauled out and some were very expensive, high performance yachts that many would consider to be “the best.”
More moderate fins with lead ballast bolted on are probably the best for withstanding hard groundings with minimal damage just as long as the keel bolts
are inspected to ensure they haven’t developed microscopic cracks that could lead to failure, but very few are inspected because keel bolt failures are infrequent and it’s an expensive process. These keels have some of the groundings energy used to transform the shape of the lead and the remainder is spread over a much larger area than with a more aggressive fin. The damage from even a hard grounding can usually be repaired with some filler and paint
Encapsulated ballast boats with fins usually have a shape similar to a moderate bolted on lead keel but with the ballast completely encapsulated there is zero chance of bolt failures allowing it to break loose and the boat
sinking as a result. However, the damage from a hard grounding can be much more expensive to repair
, especially if sea water
penetrates into any voids around the ballast, and doubly so if the ballast used is a ferrous metal.
So, for as an owner/skipper responsible for paying the boats yard bills, for a hard grounding I think I’d rather be in a boat with a moderate fin with bolted on ballast, but if I wasn’t going to have to pay for repairs
I think I’d choose encapsulated ballast as the safest. Even the best boats with aggressive fins are much more vulnerable to catastrophic damage from a hard grounding than are the other 2 types.
Then there’s another option I can think of and that’s a design where the boat has no keel and instead has ballast encapsulated in the bottom of the hull with a large bronze centerboard
that is both ballast and fin but would flip up in a hard grounding, minimizing damage. Ive only seen one of these, a Ted Hood
design that was a 49 footer and the owner said it sailed very well.