{{explanation}}
Retain the basic triangular shape throughout

1–
: 1c lead between 2c & 3c | cross and cast up round them ; cross Rsh 1M to face 2c and 1W to face 3c | all set
9–
: 2c & 3c make arches as 1c dances under, cast off | 1c meet & turn RH ; cast up round outside of set (1M behind 2c, 1W behind 3c) to original positions
17–
: All C Petronella Turn to partners and set ; repeat to finish in P's place
25–
: All M chase 1/3 clw **while**{4}   all W 2/3 LHA ; join RH with P and set in star, all C turn RH ½
33–
: All W chase 1/3 clw **while**{4}   all M 2/3 LHA ; join RH with P and set in star, all C turn ¾ RH (to 2,3,1)
41–
: All circle6 and back