The scow bow phenomenon explained by “guru” Sam Manuard

scow bows
Alberto Bona’s Class 40 IBSA

Scow bows, that is, those with round front volumes, are the future and present of ocean openers, and perhaps not only of ocean openers, as they have completely revolutionized the performance of boats such as the Mini 650s, the Class 40s, and some of the Imoca 60s. There are in fact no longer any winning boats in Ocean races equipped with “classic” bows, a fact that enshrines a design evolution from which there is unlikely to be a return.

Can scows also have a future in the cruising world? Too early to tell, we talked about it with “guru” Sam Manuard, the French designer who designed Alberto Bona’s Class 40 IBSA and is regarded as one of the most successful designers in the Ocean at the moment. The full interview, with contributions from Italian designers Gianluca Guelfi and Oris D’Ubaldo, will be published in the November issue of the Giornale della Vela, print edition.

Prue Scow – Sam Manuard’s Word.

Sam Manuard scow bow
Sam Manuard

The concept behind making scows is to avoid sinking the bow underwater. In the scows the bow instead of cutting through the water will stay high on it. The shape is so wide and flat that it creates hydrodynamic lift, which also helps the boat get some lift to break away from the waves. These types of bows have been shown to be much more efficient in wave-carrying swells than standard bows, and in general they are very efficient in any swell that has waves from 60° angle onward.”

Scow Bows – A future in cruising?

“Each type of design has some pros and some cons. The main drawback of the bow scow is the violent upwind slamming in formed seas because of the shape and amount of the boat’s forward volumes. Would you really like to bang like that on a cruise with friends and family? I don’t think so. However, we could take this concept, the scow, and smooth it out a bit so as to get some of the advantages without penalizing too much of the going with opposite wave and then propose it, with different characteristics, for non-racing boats as well.”

Scow Bows – The design of the Class 40 IBSA by Alberto Bona

“Alberto’s boat is what we might call an allround hull, but one that will show its maximum performance in strong sternwind conditions. To achieve this, that is, control and performance in the stern in strong winds and good average performance in all other conditions, we have increased the overhangs of the bow, which is high on the water, and as a result we have reduced the length of the waterline overall.”

Mauro Giuffrè




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