Firstly there may be a bit of confusion how to write the ratios for mixers, I am not even sure which is correct without referencing foilzone. I say moving Z 4, say cm, causes C to move 2cm and B 1cm etc, so 421.
The difference between the 421 (2 pulley) and 631(3 pulley) mixers is the amount B is changed. 631 changes B less so will allow higher changes to camber but also require more bar movement to get B to release and depower the kite. It could be dependent on the kite which style of mixer better suits it. I would say the further back B is placed on the kite, like the Pansh A15, the less suitable 631 would be for it, as the bar movement required would be exceedingly ridiculous. One other difference is the reduced ratio on the 631 also reduces the force at the bar. This could present an option for someone to reduce bar pressure on foil kites with 421 mixers. As to performance I think a 421 feels more responsive, probably mainly because of the shorter throw, but the higher camber on a 631 should have performance benefits as it is possible to nearly double the lift out of a wing through camber changes vs AoA, but not with out drag...There is a third option that uses a 421 mixer with a WAC or diablo line. This will give you short throw like a 421 and the camber changes of a 621 mixer, negative being even higher bar pressure than the 421. You could also get the benefit in a such a combined mixer of also combining a stable mixer setting with an unstable one, i.e. benefits of both.
Converting from 421 to 631 and back should be simple. Just make sure your final AB depower point is the same, C pulley line has the same travel ,B has enough travel and ABCZ line up, though you may find each needs a slightly different setting. Flysurfer uses nearly 50% more B pulley line than they need on their 421 mixers, not sure why. If you want to change the AB end point you need to lengthen BCZ or the C pulley line, but make sure B pulley line doesn't then restrict.
Last edited by foilholio
on Thu Mar 24, 2016 1:14 am, edited 1 time in total.