Curve brush won't weld

[yoyozozo]

Hello everybody,

I'm new to zbrush so sorry if this seems very basic.

I'm trying to create a brush that has a round pretruding tip on one side and a thin edge on the other. therefore i took a cylinder and a sphere and merged them.
i then made that into and insert brush, chose curve option in Stroke menu, and in Brush options I have Tri parts, Weld points and Strech selected and I upped my curve res and max bend.

Still when i draw the parts are not welded... /; what am I doing wrong??

Thanks for any help !!
Y.