It releases the 5th line at the bar. When you activate the grenade the 5th line releases from the bar and dangles from the kite allowing you to relaunch and get back to shore and re-connect the 5th.
And you fly it back to the beach on 4 lines? Does that work?
Somehow I'm still not convinced to go for either kites.. So many people are putting me off North / Rebel: main reason being a 5 line system:
When you crash a 5 line like a Rebel, things can get real messy, especially in waves or if you invert. Of course you have the advantage of 100% depower but you also need pay for this in other situations?
Others are putting me off Cabrinha for the IDS complicated mechanics of the QR, or for the dubious quality of canopy, or poor performance (still not sure if a switchblade is fast enough for waves).
I wonder if I should just stick to what I know: 4 lines?
Maybe give Wainman a go.. I will improve my safety clipping the leash to the front and buying myself a releasable bar too!
I haven't flown a 5th line kite, but I think you have to differentiate between a system that might damage the kite and a system that might damage you.
From what I have read, the 5th line is very good for safety if you use it the right way at the right time.
Its probably worth getting someone who uses a 5th line kite in waves to demonstrate what way it works and what is possible or not.
Sometimes I put an extra 5m on the leader lines if I will need to pull in a lot of steering line on a kite. And 5m extensions on the centre lines.