Page 160 - Buck Tilton - Outward Bound Ropes, Knots, and Hitches 2 ed.

Form a second loop, a duplicate of the first loop,
and lay it on top of the first loop.

A second loop at the beginning of a double bowline doubles

the pressure on the working end and provides greater
security. The finished knot does not have two loops, even

though the name implies that it might. If a double loop is
needed, use the bowline on a bight (see page 54). This knot

reduces the strength of a line by only 25 to 30 percent,
making it an overall stronger knot than the basic bowline or
the bowline on a bight. A stopper knot in the working end

also adds security. You may see this knot, as with other
variations of the bowline, being used by campers and

climbers.