Thank you Regis for trying to be diplomatic
Arguing with a m.oron is getting tiresome, others will just have to work out the basis of his assertions are flawed. Arguing from authority sigh/lol.
Yes WAC lines they simply change the ratio of the mixer for part of it's range. They allow the use of lower cambers when more depowered and higher when powered. If you think of them in terms of a car gear box they are like having another gear. The negative to them is they increase bar pressure by pulling on A through B.
Why I may have explained Z in simple terms:-) what other way is better?lol But I haven't yet explained B and C! B and C are very similar in a way and similar to Z also in another way. B, C and Z all engage the part of the wing preceding them. If you were to solely engage one of BC or Z, ie have it tight and the others slack, you would find B makes the least power, followed by C making more and Z the most. It's all to do with the amount of wing area between A and B or A and C or A and Z, (but also the camber). Now the big difference between BC vs Z is camber, pulling on B or C or both will create negative camber or reflex which in turn with torque the kite backwards pitching it up, back into the window with more tension on the bridles, ie more stable , Z does the opposite
Now of B and C I believe B may make the most torque backwards i.e. most stable but what it definitely does do is make the least power on the kite. This then gives the possibility that if you can control B alone you can have good control of the kite, by sheeting in and tightening B the kite will become more stable and sit back in the window but won't generate too much power. Bringing us to the mixer, thinking of the mixer in terms of something that just changes AOA is well stupid, naive, ill informed and well just dumb. The mixer's function is to assist in control of the kite. It has a number of problems to try and overcome, like make a kite manageable (stable) while depowered or somewhat depowered, make a kite have the best L/D (upwind, float), make a kite have maximum lift (power), make a kite have reverse flight( for relaunch and more). Amazingly or not
it can solve all these problems in one package. The real problem the mixer has is that best solution for one problem is bad for another problem. A very stable mixer has poor lift, a high lift mixer has bad L/D, mixer that doesn't stall can't relaunch. Bringing us to B and why looking at the mixer just changing AOA is stupid. The mixer has the ability to only affect B before C or Z and B is the secret to stabilize a kite and make it more manageable. So you can have this sort of play between A and B long before C or Z enter the picture. This then forms most of your kite control A and B and nothing else. When Z or C become too tight they interfere with this and you get a kite that is harder to manage. When should then C and Z engage? well at the perfect spot somewhere before the kite starts to stall. Engaging more Z actually delays the stall more so things get interesting. In simple terms what you have is the mixer engage with B for a large part of it's range then suddenly C and Z engage together. If you have C engage too much before Z you loose some performance and some manageability and you could delay C till Z engages and maintain just the A and B relationship. Even more basically if after lengthening Z you find a kite not stable enough try lengthening C. Or if you find the performance loss from lengthening Z too much instead of lengthening Z try lengthening C. The important thing to observe on a foil when tuning it is when are the different bridle rows going tight and how much gap is there between them. If Z tightens before C you have higher lift less L/D. If C tightens before Z lower lift possible better L/D. If C and Z tighten before B = messed up kite. If C and or Z tighten long before stall = kite hard to manage and stability problems.
TLDR B and C are complicated