Without going into a full thesis here, I will simply explain the wing elements and what their functions are.
WING FILLET... This is the 'elbow' in the wing where the wing effectively is joined to the end of the beam via a large, high-tensile ball joint. It's also the structural junction for all the other bits. There is a 600mm stub that sticks out the top with a steel ball on it. The main mast sleeves over this and has a cup in it. This is where the component on which the main wing rotates. The wing fillet also has a female sleeve which the horizontal WING EXTENSION fits in. The wing fillet is fixed off to the beam at a pre-set angle of 10 degrees to the wind. It is not sheeted whilst sailing but rather used as a sheeting point to control the angle of the LOWER WING which is immediately above it.
LOWER WING... This is the 7 meters of area immediately above the wing fillet. It is limited in its ability to rotate by the strut which holds the wing up in compression. It can rotate around ±45 degrees which is plenty. It can be manually linked to the MIDDLE WING for raising/lowering/transporting/storage purposes. It can also be sheeted independently from the cockpit via a small mainsheet which is linked to the WING FILLET. The LOWER WING isn't connected to the main carbon COMPOTECH spar. The spar passes through all the ribs so that they are free to float around it. This way it can spin independent of the upper wing elements and can be removed to fit in the container.
As the Wing Fillet is fixed in relation to the boat, the COSWORTH wing angle sensor uses a laser to measure the difference in angle between the bottom rib of the lower wing and the top rib of the wing fillet.
MIDDLE WING... This is the largest component of the wing. All these ribs are bonded onto the COMPOTECH spar so when the mast rotates, this whole section of wing rotates. This section of wing can rotate through 360 degrees as it is not interfered by any shrouds or supporting struts. When we get towed back up the course it can therefore fully backwind/depower. It is sheeted via a bridle which also pulls in the LOWER WING at the same rate i.e. they come in together when the mainsheet is pulled. For towing, the whole wing can be locked together using sliding pins between the sections.
TRIM FLAP... This is the small flap on the TE (Trailing Edge) of the MIDDLE WING. When removed it reduces the chord of the wing so that it fits in the 40' container. It is also adjustable to alter the 'feathering'/de-powering properties of this key section of wing. It is a slightly lighter construction.
UPPER WING/WINGTIP... This small tip section of the wing cannot rotate through 360 degrees due to its proximity to the shrouds which attach to the top of the COMPOTECH spar. For this reason it is separate. It is sheeted via a bungee that will stretch if the WINGTIP does interfere with the shrouds... but have enough strength to sheet in the small section otherwise.
WING EXTENSION... This is an interesting part of the wing that adds greatly to its overall efficiency. Previously the outboard end of the boat was flown by generating lift from the beam. This was pretty inefficient as the pressure areas from the beam and the wing were cancelling each other out. Chris and Wang at AEROTROPE who did all the structural design work and performance analysis for the wing which shaped the overall package came up with this solution. I didn't welcome the complexity it added but the performance benefits were undeniable so we went with it. Basically it does the following...
- creates a more effective lifting lever for the outboard end of the boat. This is what makes the outboard end of the boat fly.
- compliments the pressure distribution along the wing which makes the wing feel much higher aspect ratio than it is whilst maintaining a low centre of effort.
- Works in 'ground effect' due to its proximity to the water. This reduces the amount of spillage of pressure from one side of the wing to the other (induced drag)
WING LIFT FLAP... This is an active component that adds or reduces the lift of the WING EXTENSION. It will be used to actively control the flying height of the outboard/leeward end of the boat. It will most likely become fully effective at around 50 knots and be controlled by as simple a system as possible. It can't be fixed as the faster we go, the higher the beam will fly and we will lose a lot of performance. It only needs to 'just' fly the float. I don't want to be controlling it during a run. We have a number of viable options for controlling it from a surface sensing wand as seen in hydrofoiling moths to a simple means of mass balancing it so that it only generates just enough lift to fly the pod in ground effect as per VSR1. We will start with this option.
As mentioned, the wing extension combined with full wing lift flap deployment can only lift the weight of the wing and beam at around 50 knots. If we see the leeward pod flying before this... as we have at around 38 knots in initial trials... it means that the whole wing is over inclined and needs to be stood more upright.