Vendée Globe

place your bets

There are a number of new innovations in the upcoming Vendée Globe but the one that really stands out are the Dali foils. What are Dali foils you ask? Glad you asked because I am happy to explain. A number of years ago British yacht designer Hugh Welbourn came up with the concept of Dynamic Stability Systems or DSS. Essentially DSS is a lateral lifting foil, a foil that projects out from the side of the boat perpendicular to the hull and parallel to the water. When the boat heels the foil dips into the water and a foil being a foil it starts to generate lift. Leeward lift, which in turn reduces the boats displacement by partially lifting the boat out of the water. Ingenious I think.

Well the top IMOCA 60 designers were intrigued and of course wanted to incorporate this technology into their latest designs but they ran into trouble with the rules that govern IMOCA. The rule states that there may be no more than five appendages and traditionally this has meant the keel, double rudders and a daggerboard either side. It’s pretty hard to get rid of any of those but yacht designers can be clever and that’s when they came up with the idea of combining DSS with the daggerboards to get the benefits of both within the same appendage.  What you end up with is a shaft that projects laterally out the side of the boat, an elbow where the foil makes a sharp turn upward, and a somewhat triangular tip. The shaft acts as the DSS and the part that is turned upward replaces the daggerboard and stops the boat from slipping sideways. These new combination foils have been given the nickname of “Dali foils” in honor of the iconic Spanish artist’s distinctive mustache.

Another innovation that some boats have are tubercles on their rudders. Tubercles are not a new idea but they are making a comeback on some of the IMOCA boats. Tubercles are those protuberances on the pectoral flippers of humpback whales. The Tubercles are added to the leading edge of rudders and are said to generate more lift at rudder angles in excess of 22 degrees than smooth rudders, but the debate is goes on. Other designers believe that the tubercles decrease lift and increase drag at the lower rudder angles and that the trade-off is not worth it. Former Vendée Globe winner Vincent Riou is one skipper betting that the tubercles will give him an advantage and he has them on his boat PRB.

Dali foils, tubercles or whatever else designers have come up with, the result are some pretty amazing looking boats and it’s going to be interesting to see if any of the boats with Dali foils are able to carry them the entire way around the world without damage. If I was a betting man I would bet against it.

– Brian Hancock.
From Sailing Anarchy