Jul 27, 2009

Pete Melvin on AC Wave Piercers

Photos: Photo: Allen Chapman MorrelliMelvin A3 A-Class, Pete racing at US Nationals Gilles Martin Raget-BMWoracleRacing DZ 1,5 bow
Pete Melvin on his MorrelliMelvin A3, that bow looks familiar or what?
Suddenly everyone is talking about 'Wave Piercing', speculations are made every minute on "design failures" causing dives and stuff on BOR 90, we´d better listen to someone who knows of what he is talking about.
I respect guys like Pete Melvin the most, cause they not only have the theory, and a aeronautical engineering backround... he also sails what he designs, hey! he is even A-class World Champion sailing MorrelliMelvin´s A-class cats, so sit back and read from the master itself for a practical and logical explanation. Pete is also involved in the BOR project and also had some input on their new floats.
I asked Pete to comment those BOR 90 dives, and he kindly bothered to answer:

Pete Melvin:
"Regarding the new BOR 90 floats, I have not been sailing on the boat with the new floats so it is hard for me to say if there is a problem. As mentioned, there was a big swell on the day the recent photos were taken, which as you know can cause large pitching amplitudes depending on the relative speeds and angles of the waves and the boat. These types of bows are designed to occasionally penetrate through waves. A different bow shape may be optimum for the kind of ocean swell they encountered on that day.

Successful race boat design has always been about designing a boat that performs well in all the conditions expected, and that does not have any significant weaknesses. For instance, this is why the Infusion has been successful in my opinion. The smaller "wave piercing" bows on BOR 90 1.5
reduce weight and windage all the time, and reduce pitching and resistance especially in light to moderate conditions. In my experience, the smaller bows (like on BOR 90 1.5 and our A3 A cat design)are not as effective as higher volume wave piercing bows (like on the original BOR 90 floats and the Infusion design) in high winds and larger waves. If you are expecting light
to moderate conditions for AC33, then you would want the shape of the new floats..." ---------

Photo: Thom Touw
Pete Melvin Infusion F18, more height and volume than the A-Class, same Wave piercing concept, but different approach, taking account of final usage and specific class characteristics.

Photo: Gilles Martin Raget-BMWOracle Racing
1st DZ one, Infusion style, also the type of WPiercing bow used on Banque populaire V (right)
As mentioned in last BOR 90 'diving' post, they are testing amas designed for an specific venue in mind, they already tested their higher and more voluminous bows that would perform better in those swells. But the key here is maybe the definite venue has not swell at all! so these tiny low drag bows will simply fly and perform as designed in a flat water location.

There is an specific goal for BOR 90 designers in testing differents types of bows, there´s no design failure at all.
I mean a design failure would be having those DZ 1,5 extreme WP bows on 'Banque Populaire V' on her transatlantic records attempts...


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