I like to think I’m a bit more objective when it comes to this sort of thing, so I looked up the knot and ran some Instron tests using the same material and parameters as my previous experiments. The knot itself, for those who don’t know it, starts identically to a water knot i.e. the leader and tippet are laid side-by-side and a loop formed. However, instead of winding the tag-end and tippet through the initial loop multiple times in the same direction, in the ‘J knot’ these are fed through the loop in alternate directions. A picture is much better than words at this point, I ‘borrowed’ the one attached from www.netknots.com/fishing_knots/j-knot, where you can also see an animation of the tying.
Normally with a ‘new’ (to me anyway) knot I would practice it first before tying up the samples for the Instron. The ‘J knot’ however was simple enough to go straight in with the tensile testing; so long as all four pieces of nylon (leader, tippet and two tag-ends) were drawn down at the same time a pretty consistent looking knot was produced. The pull tests proved to be equally consistent with an average strength of just over 73% recorded with an acceptably low standard deviation. As such it pips my previous best, the blood knot, to top position (excluding the Bimini loop-to-loop). My updated results are also pictured.
So thanks to Peter (if you read this) for putting me on to this knot, I’ll be using it for sure on my next trip.