Rob Clark from Mansfield in a video by Tim Thomson demonstrated a strainer knot for fence wire. Rob called it his “Everyday Knot”, Tim thought it needed a name and named it the “Mansfield Knot.”
Strainer knots are ones that go min line and must be tied between two strained end ends in a wire span, without releasing much tension from the span when the strainer is removed.
Above is a pic from instructions supplied with a Donald Wire Strainer, a quite old device that I am not sure is still available. The Donald Wire Strainer was my first strainer around 1970. Let’s call the left hand part the standing part and the right hand part the running part. Note that after pulling the running part through the U loop formed near the strainer grip, the running part is wrapped firstly over the standing part.
So this knot worked fairly well in terms of lost tension, but experience was that its strength was lower than you might want. I have not seen good test data, Tim Thomson published data for a knot he labels as Speed Knot (Donald Knot), but they are not synonymous and I would think the Speed Knot is stronger.
Above is a grab from the video. It is pretty easy to see how to tie the knot, but check the video.
It is more complicated to tie that the genuine Donald Knot, and probably about as difficult to tie as the common Speed Knot, but it has superior breaking strength (almost 90% of the UTS of the wire tied in medium tensile 2.5mm wire on a single sample of the wire and knot.)
Whilst some testers publish breaking strain of fence wire knots, they do not usually measuring elongation at some relevant tension, like the recommended span tension for a particular wire.
The construction of the Mansfield Knot leaves me thinking that elongation under tension may be poorer than the Speed Knot, and I have not seen either measured. That said, Tim did show the failed knot and it has elongated a little, but probably less than 10mm at failure which should be quite satisfactory.
I have tied eight of these in 2.5mm medium tensile and 2mm soft wire using variously a Hayes 108 strainer and an modified early Wireman strainer (modified so it would walk the supplied chain.)
An interesting knot that could certainly be your “everyday knot” as Rob called it, but I like Tim’s name, the Mansfield Knot.