the concept of unsinkable yachts
Hanging out here all by itself, I´m left to wonder what generated this post in the first place. Having said that, here are a couple of add´l observations in addition to Jeff´s more technical analysis:
I see no correlation between a boat (let´s presume it´s an Etap) with in-built flotation and a lost keel. None. So if we back up to the larger data base, of all boats that are sunk, rolled, dismasted, clobber reefs, go aground and otherwise experience a terminal event, how many keels fall off? Virtually none relative to any kind of longitudinal statistical analysis. So most of this post, which involves follow-on effects from a lost keel, strike me as irrelevant to the topic of unsinkability specifically and design issues, generally.
Sadler´s brand name has been recently resurrected but Sadler has not built boats with in-built flotation for many years now, so I´m not sure how their product is relevant to today´s boating world except where the potential buyer is in N Europe and wants one of the relatively small percentage of Sadlers that were built with flotation. Similarly, bagged floation has been commercially attempted in the past, only to fail at meeting even the simpliest criteron, that of keeping the Mother Ship afloat, and the vendor had to abandon the idea altogether...so this topic also seems essentially irrelevant in today´s market.
To my knowledge, Etap is the only builder of a range of offshore sailboats with in-built floation, and the only builder that then meets certification for the boat to be *sailed* in the totally flooded condition while still retaining acceptable stability. The fact that these boats may also inhibit catastrophic flooding due to a colision, depending on the location of the hull strike and what is hit and what speed, isn´t promoted by Etap but I think it´s worth considering as a potential, additional safety feature.
''Unsinkable'' boats are not UNcatastrophic Event boats, and so a fire may still require the crew to abandon the boat...but that´s a small portion of the issues faced by an owner today. Beyond this, I´m not sure what motivated this post.