...how to make the ultras?
No, I sure don't. I figured it out from looking at pictures of them...
Basically, you need a piece a little more than twice the finished length. Fold in half, form your end eye (put any chafe guard you need, or hardware in it first)... 3 brummels, leave loop space, 3 brummel, leave loop space, etc. and you'll end up with 2 tails at the end. I usually do five brummels at the end, then stick one of the short tails inside the other, lockstitch that all up and shrink tubing to finish. Your loops need to be large enough for the eye, or any hardware (pulley, etc.) that you splice onto the end, to fit through them.
You need to try to keep the lengths of the two legs of each loop the same, as best you can. Otherwise, one leg will carry too much more load than the other. To use the sling, you just put it around the limb and stick the eye/hardware through whichever loop keeps it closest to the limb. It is basically a sling that is in basket mode (because there is two legs of rope throughout) that is then used in choker mode. So, it's very strong... the MBS of the sling, when using Tenex-TEC will be very close to the MBS of the rope. With the Class 1 ropes like Amsteel, the sling MBS will be more like 70% of the rope's MBS.
