take a look at your ostrich herl. its like many feathers and has a convex and concave side to them. i think you will want to wrap the ostrich herl with the stem as the leading edge with the herl flues pointing to the bend of the hook
http://www.artflies.com/sec_engelsk/...g_herlbutt.htm
http://www.invictaflies.us/Wet%20Fli...%20drummer.htm