This past week we finally had enough wind(about 10mph) to get the RAVE V to foil, unfortunately it only partially did. The windward side and the mainhull were rising, however, front aka was twisting causing the leeward ama and foil to change the angle of attack and actually cause negative lift. You can watch a short clip here to see it happening.
We took the masts down to add some structural reinforcement to the front aka and decided to do a tow test to otherwise test the foiling ability. The first test the front of the boat rose well, however the rudder wasn't generating the lift we needed. We took the rudder off the boat and changed the sonic tube on the foil from a 4in to a 6in tube. With this increase it generates about 2.5x more lift. We then did more tow testing the next day and the boat fully foiled.
What we learned and the tweaks we are making:
1. With the twisting in the akas we need more torsional rigidity. We will switching from 2.5in tubes and going to a custom D profile. This D profile will still allow us to telescope the amas in and out, but will provide more stiffness.
2. The rudder foil was too small, but the tubes on the main foils are just right. We will be going back to the original design of a 6in tube on the rudder foil, but keeping the 4in tube on the V-foils.
3. Sail plan was aggressive. We found that with the 26ft masts and the sails, we had too much sail area. The boat sailed better when we reefed the sails. We will be decreasing the mast length from 26ft to 23ft and decreasing the sail area.
4. The RAVE V is fastest on a close reach. Unlike the WR17, the RAVE V is fastest when sailing closer to the wind. The other interesting thing to note here is that it points about 15degrees higher than the WR17
5. Freeboard of the mainhull is too much. We will be removing between 4 and 6in of freeboard from the production boat. This will give us better clearance over the water, helping to reduce the effects of hitting waves.
6. Lowering the mainhull side V foil. To get the boat out of the water sooner and allow it to ride higher over the water, we will be lowering the main hull connection point of the main V foils. This will put about 10 more inches of foil into the water right off the bat.
7. Fixed angle of attack on the rudder. Our prototype has an adjustable rudder, but we have found that about 6degrees of angle of attack on the rudder is about perfect for all conditions. For simplicity we are looking at keeping it a fixed position instead of having it adjustable. This will mean that while sailing, you won't ever have to touch the foils, the only thing you will need to do is trim the sails and steer the boat.
