I've had the same problem with all my sails when using the North XT pinlock extension.
It's not too bad with my smaller sails, (less tension required). However, with sails of 9m and over, the tension on the downhaul rope cutting over the edge of the last roller of the sails pulley is simply dangerous!
I have snapped new downhaul rope on a number of occasions while rigging my 11m Warp (very frustrating). I then replaced the rope with the White NP RSX type (best cord money can buy) I was using the 42cm model set at 28cm for my 11m Warp however by setting it to 30cm I found it much easier to rig and tune. Adding an extra 1 or 2cm of extension stops the last part of the rope that feeds into the cleat from being pulled or cut across the roller too much. (interesting that we are talking about ICE wave sails all the way up to FW warps,,,can't be all the sails at fault)
I used the same XT extension so many times at such high loads of tension that the 3rd tack pulley on my 11m Warp (the one closest to the mast, which feeds the last line into the cleat) actually BENT INTO THE SHAPE OF THE ROPE!!!! NO JOKE AT ALL! Imagine how much tension it takes to bend a 4mm groove into the edge of a brass pulley!!!!! Then think how strong the NP rope is to bend the brass edge without snapping!!!! By the way, the groove made it possible for my rope to easily thread from sail pulley to extension cleat with no danger of being cut. (would never have thought of it on my own!)
I have recently stopped using the XT pinlock extension for my race sails even though i found it to be one of the most reliable extensions i've used. (even though the cleat position was not well designed) I have now cut down the 40cm Carbon Extender to my required length and am using a simple race cup.
The reason the sail pulley doesn't rig perfectly inline with the XT extension is quite simple.
The XT has "oversized" plastic rollers which makes it easier to pull but moves the center of axis further away from the mast. The sails all have standard sized rollers. Also the sail and extension are at 90' to each other which is not normally a problem when the pulleys are of a similar size. And the last but most important bit of this puzzle is in the placement of the XT's cleat. The cleat is about 1.5cm!!!!! closer to the mast than the axis of the rollers on the extension.
Most other extensions will work perfectly with all North Sails. I'm convinced that North Sails were not designed on the XT extensions.
By the way, there have been other design oversights at North. Has anyone else had problems with the new generation of Platinum racing masts? The tail piece is very stiff indeed by fitting over the main tube of the boom instead of into it as is the norm. But one simple problem is that the tail piece needs to be hollow to fit "over" the boom. This means it fills with water!!! Carrying a couple of liters of water around in the end of your race boom makes sail handling a whole new experience.
Anyway, this must all sound very confusing and pointless to a lot of people. However if you have used the XT series with a North Sail you may have experienced this dilemma yourself. Oh, and I agree with the last poster about the RAMS Min and Max wind settings. Think of Min wind mark as Max instead.
Relax and go fast
P.S I also use the streamlined extensions for my Slalom sails.
Last edited by JJay; 13th February 2008 at 02:38 PM.