There are many possible "Janus" bowlines ( = two collars, one "higher" around the Standing End, and one "lower" around one eye-leg, sharing one common leg, which goes through the nipping loop ). For some first comments about their number, see (1) and (2).
Many knot tyers ( misled, perhaps, by Ashley ...) still believe that all the standard/common bowline needs, in order to be turned into a "secure" bowline, is
a second nipping loop - hence the attention to the overestimated
Double and
Water bowlines. However,
a second collar can offer much more to the security of the common bowline, than a second nipping loop... After each 180 degrees U-turn, the magnitude of the friction forces required to completely and securely immobilize the Tail End, is greatly reduced.
Ceteris paribus, a TIB bowline is always a more versatile practical knot than a non-TIB one. So, I have focused my knot-tying efforts on TIB bowlines, which are able to offer anything the most sophisticated of the less versatile, non-TIB ones, do. Alpineer has tied one interesting and good-looking particular
Janus bowline, which happened to be a TIB one (3). However, Alan Lee had expressed doubts about the ability of this knot to "close" evenly, and at the same instance, without leaving a loose collar - i.e., without limiting the functioning part of the loaded nub to the half of the whole (4). So, since then, I had shifted my attention to a TIB variation of the
Fontus bowline, shown at (5), which I call
"Ampersand bowline" ( its collar structure looks like the figure of the ampersand )(6).
However, I have not tied
all the possible TIB Janus bowlines - nor I had tested the ones I did tie in the required detailed way I would had wished. There may well be other secure
TIB Janus bowlines out there, standard or "Eskimo" ones, which can be tied easily and quickly
in-the-bight, and serve for climbing/rescue purposes. ( An example of an "Eskimo" Janus TIB bowline is shown at (7)). So,
hic Rhodus, hic saltus ! In KnotLand, there are no paths other than the ones
we make, by walking... The "knot tying community" is more of a euhemerism : knot tying is a lonely sport, and the (few) spectators are often more willing to throw something against you, than applaud your efforts !
1.
http://igkt.net/sm/index.php?topic=3150.msg19418#msg194182.
http://igkt.net/sm/index.php?topic=4329.msg27171#msg271713.
http://igkt.net/sm/index.php?topic=46974.
http://igkt.net/sm/index.php?topic=48515.
http://igkt.net/sm/index.php?topic=1202.msg19317#msg193176.
http://igkt.net/sm/index.php?topic=48777.
http://igkt.net/sm/index.php?topic=4703