Kala mam here is my pencil drawing of Margazhi kolam-21. 13-7 interlaced dots. I added some extensions beyond the dots mam. Hope this drawing will help u mam. 
dotted 13-7 interlaced (sandu pulli)
Here are the kolams and rangolis in this page:
- Pencil Drawing for Kala mam
Created by GOMATHI_KRISHNA on 2013-01-04,
