Doug Lord
Flight Ready
- Joined
- May 26, 2009
- Messages
- 16,679
- Reaction score
- 353
- Location
- Cocoa, Florida
This is an excerpt from an article on the SA front page: Full article- http://www.sailinganarchy.com/index_page1.php
According to Melvin, the Nacra 17 was chosen by the majority of sailors at the evaluation trials for a new Olympic catamaran for 2016.
In the last few years curved foils have appeared on A Class catamarans, the new NACRA 20 and SL33 catamarans, and some custom and limited production catamarans. All of these designs successfully incorporate constant-curvature daggerboards, commonly referred to as “c foils”. The innovation with the curved foils on catamarans is that they are used to enhance performance for both upwind and downwind sailing.
Performance improvements with the c-foils have been well documented in the A class catamarans and c-foil equipped boats have won the World Championships for the last several years. Other foil geometries have been tested on the A Class cats but so far the c-foils have proven to provide the best all-around performance and are by far the most user-friendly and practical solution.
Lifting foils on catamarans are an area of intense development at the moment, especially with the next AC being contested in catamarans that allow lifting foils. I do not think anyone knows exactly what developments will prove to be best in the future. Each class of boat will evolve toward a foil geometry that is best suited to their specific rules and requirements.
For the NACRA 17 we chose c-foils for the following reasons:
A) C foils have proven to make catamarans easier to sail, especially downwind.
They provide lift which helps keep the bows up and reduces the tendency to pitchpole.
The extra lift generated from the foil helps reduce hull wetted area and markedly reduces hull drag.
B) There are other foil geometries that could provide efficient lift but all the ones we evaluated for the NACRA 17 had issues that we determined were not suitable for this type of boat. For instance, L foils are not able to be retracted from the top and would make launching and beaching problematic. We are also not convinced that L foils would be faster on this type of boat. They would certainly create more drag in light air, due to having more wetted area. The windward L board would also need to be lifted to reduce drag and unwanted vertical lift on the windward side, thereby making the boat much harder to tack. C foils can be left down on the windward side since they automatically reduce their vertical lift when on the windward side.
C) C foils make the boat more exciting to sail. The ISAF Olympic Multihull Evaluation Committee report and individual sailor reports confirms this. There is an added dimension of control and speed that can be attained after gaining some experience sailing with them. We believe that this is an area that should be exploited with a modern racing catamaran and is why you see them on the NACRA 17, NACRA 20, and SL33 catamarans.
click on image:
According to Melvin, the Nacra 17 was chosen by the majority of sailors at the evaluation trials for a new Olympic catamaran for 2016.
In the last few years curved foils have appeared on A Class catamarans, the new NACRA 20 and SL33 catamarans, and some custom and limited production catamarans. All of these designs successfully incorporate constant-curvature daggerboards, commonly referred to as “c foils”. The innovation with the curved foils on catamarans is that they are used to enhance performance for both upwind and downwind sailing.
Performance improvements with the c-foils have been well documented in the A class catamarans and c-foil equipped boats have won the World Championships for the last several years. Other foil geometries have been tested on the A Class cats but so far the c-foils have proven to provide the best all-around performance and are by far the most user-friendly and practical solution.
Lifting foils on catamarans are an area of intense development at the moment, especially with the next AC being contested in catamarans that allow lifting foils. I do not think anyone knows exactly what developments will prove to be best in the future. Each class of boat will evolve toward a foil geometry that is best suited to their specific rules and requirements.
For the NACRA 17 we chose c-foils for the following reasons:
A) C foils have proven to make catamarans easier to sail, especially downwind.
They provide lift which helps keep the bows up and reduces the tendency to pitchpole.
The extra lift generated from the foil helps reduce hull wetted area and markedly reduces hull drag.
B) There are other foil geometries that could provide efficient lift but all the ones we evaluated for the NACRA 17 had issues that we determined were not suitable for this type of boat. For instance, L foils are not able to be retracted from the top and would make launching and beaching problematic. We are also not convinced that L foils would be faster on this type of boat. They would certainly create more drag in light air, due to having more wetted area. The windward L board would also need to be lifted to reduce drag and unwanted vertical lift on the windward side, thereby making the boat much harder to tack. C foils can be left down on the windward side since they automatically reduce their vertical lift when on the windward side.
C) C foils make the boat more exciting to sail. The ISAF Olympic Multihull Evaluation Committee report and individual sailor reports confirms this. There is an added dimension of control and speed that can be attained after gaining some experience sailing with them. We believe that this is an area that should be exploited with a modern racing catamaran and is why you see them on the NACRA 17, NACRA 20, and SL33 catamarans.
click on image:
