Pinned post for Q&A :)

My vote goes to the carrier pilots that found out the magnetic detonators of their torpedoes didn’t work when they accidentally attacked HMS Sheffield during their hunt for Bismarck.

There's the time the Pacific squadron failed to hit anything off the dogger bank hence avoiding a war Russia couldn't afford to engage in...

In the words of Bob Ross.

“We don't make mistakes, just happy little accidents."

Id probably have to go with the failure of the Sims class destroyers. Their instability problems led directly into the fletcher class being given large stability margins and made them into one of the most successful destroyers of the war

The first "mistake" has a parallel.

In the late 60s and early 70s, designers and builders of yachts were transitioning from using wood to fibreglass, and they similarly weren't sure of the new material's long term strength and durability.

The legend is that they simply used the same thickness of GRP that they had previously used of wood and ply, which has resulted in thousands of sailboats with 3/8" sides and 1 1/4" keels. Being basically indestructible, these commonly survive to this day, and are usually scrapped when their engines wear out.

the great eastern was such a leviathan of a ship. too bad she just missed surviving into the modern era

Ahh yes, the "task failed successfully" notification.

It still blows my mind how quickly after the advent of heavier than air flight, someone said, let's take this unreliable rickety airplane, fly it over water, and land on a ship, apparently because my odds of survival simply flying over land aren't low enough for me. They truly were pioneers.

How about ram bows that, in effect, came right on back as bulbous bows that helped increase fuel economy and speed?

I would have added the Lexington and Saratoga to the list.  With their gigantic size and thin armor they would have been horrible battle cruisers.   However because of the Washington naval treaty they got converted into the best prewar aircraft carriers.

There is an aviation equivalent to that "overbuilt iron ships" condition.   The Douglas DC-3 was similarly overbuilt, hence the reason it stayed in service for so long.  It was pretty much the first "modern" style aluminum aircraft built to what was at the time some very new principles, so the engineers used massive factors of safety on everything.

Chances are good that the Boeing 787 exists in a similar condition.  It was the first all-composite fuselage, nobody yet knew quite how the material would behave, so the Boeing engineers used massive factors of safety just in case the material properties they got from the test labs were wrong.

Okay the SoDak switch failure is crazy and a good example of how the 16” gun was NOT actually small enough to avoid damaging the ship’s components with blast waves.

Greatly appreciate the analysis of what happened to USS South Dakota’s electrical circuitry. I’d read many times that she had basically “gone dark” at a critical moment during the battle with Kirishima, but what exactly caused this wasn’t explained especially well. Now I know. Thanks for that.

Many undesirable things in life turn out to have unexpected upsides that one discovers only by failing to prevent them.

I'm going to add an honorable mention to this list: the embracing of ramming in the Ironclad Era and resulting use of ram bows.  This, unintentionally, made ships of that time more hydrodynamic, and led directly into the bulbous bows which are standard on today's ships.  This is less a mistake and more of a "we worked from a faulty premise but accidentally found something more useful in doing so" scenario.

The mk14 torpedo saved a lot of lives, so it’s probably one of the most benevolent mistakes in history!

I cannot imagine, rocking up in the Falklands c. 1941, then seeing SS Great Britain at Sparrow Cove, having only read about the ship in a school book.

5:50 The same happened when fiberglass boat building happened. Nobody knew how strong or durable it would be, so the laminates were as thick as the timber used on wooden boats. Those boats will never break. Swan sailboats build in the 60's will probably sail for a hundred years still.

I'd have to add one more into this mix.  But one of Drach's previous videos had a discussion where turret communication had been mis-wired, which led to the fore and aft turrets being put on the same circuit by accident.  This was found to be preferrable to the intended design, and became standard practice.   I just can't remember which video/ship to cite.