If you want to show me that UPT requires a washer on the main closing loop, and or want to show me that there is some min tension required on a Vector container, the new ones, I'm all ears
Ok, I'll bite -- Your post did get me to go look through a recent Vector manual. (Oct 2010, Rev 1, apparently the latest). While some manuals do get pretty old before updating, it is good to see that this manual has a lot of little updates -- there are some things UPT recommended jumpers do with their gear in the past, that they don't now.
While washers aren't mentioned in the text, the replacement parts section shows a washer:
Most people are used to using a washer, and it seems important when using standard type IIa with a single overhand knot under a #0 grommet. As you point out, other bigger knots are possible, and nothing in the manual says a washer is mandatory.
But unless a jumper knows very specific techniques that make a washer redundant, I wouldn't want to tell them that you don't need a washer for their closing loop!
I personally don't see any issue with wear from washers on the closing loop... but I make sure the rounded edge of the washer is against the knot. You may notice that the sharper stamped edge of the washer is against the knot in the photo, which isn't what I like to see, even if any wear is likely to be very slow...
(This post was edited by pchapman on Jul 30, 2013, 7:54 AM)