Hi, have a careful read of the rigging manual at 7.2 - Vang System, points (d) to (i).
Others might have the measurements best for both 7 & 9 rigs. By memory, you need to adjust the fixed dyneema part of the vang so that you have sufficient travel (of your big black vang blocks) so that you can can't max out the vang on either sized sail. While still having sufficient adjustment to also still fully loosen the vang to be able to raise the sails This means you have to undo some of the dyneema knots, including the cow hitch that connects the dyneema to the small shiny double block that sits up under the boom. If the knots are a bit old they will be set hard like rocks and it will take a truckload of very patient prying cursing, and then trial and error to get the correct relevant lengths for both sails. Either that or just cut the knots and buy a new length of dyneema. Best you wait for anyone else to chip in with advice before you resort to cutting anything etc. Same considerarions apply for anyone with a single sized rig, if they haven't set their dyneema lengths correctly, they either won't be able to raise their sail fully, or will max out their vang with insufficient travel to properly flatten their sail.
I can't seem to get my Vang setup to swop between my 7 and 9 rigs. Has anyone got any decent pictures or advice on measurements required. I'm having a bit of a blank in working out the correct set up. Currently i've just about got enough tension for my 7 rig but nowhere near enough for my 9. I have the rooster tapered kit but think i may have it incorrectly set up. Ive looked through the forum but not a great deal of info on vang setup. Thanks
