Best case reduction in drag from a bulbous bow bulb

Seeing refits having these added. Anyone familiar with the numbers?
ie how much drag is reduced, fuel saved in a given application.

Yacht Design and Construction - Our Approach | Bering Yachts https://www.beringyachts.com/yacht-design-construction-approach/

 

A bulb refit will only work in certain applications, it is not a cure all.
Design Questions - Bulbous Bow / Wake Smasher ? https://www.boatdesign.net/threads/design-questions-bulbous-bow-wake-smasher.60929/#post-838392

 

I heard they were mostly for navy ships because they wanted to reduce bow spray for both less visibility and so less spray is spraying all those freshly cleaned guns etc on their busy decks. Bow spray was often used to estimate speed of enemy ships prior to radar.

 

Sorta...Blub bows grow from a finding by Taylor that a ram type bow reduced powering (the PENNSYLVANIA trials). This followed on to the heavy forefoot Atlantic type bows used for the second generation fast cruisers, carrier, and battleships, as well as commercial high speed liners, which were length limited. This bow combined drag reduction with good seakeeping, reducing the cutwater feather was a side benefit. In the 1950's several independent research projects pushed this concept to the extreme of drag reduction, giving way to what today is the projecting bulb seen on some ships. These types of projecting bulbs have some restrictions however. On the flip side, most modern bulbs on naval vessels are not optimized for drag, though it provides some benefit, but for acoustic reasons.