create a circle
select the circle and click on outline
create an outline in this case with 10mm
select the inner circle again and choose outline
this time negative in this case -15mm
select all 3 circles and choose align center

create a form 
i started from the center of the smallest circle
the shape can be angular at the beginning because we will change it with the node
as soon as the shape has been created, select the shape and edit node
select the top two nodes and change the node to perfect symmetry
use the handles to set the desired shape
now select the shape and choose circular array in the side menu
copy to 8 and set with the y coordinate that all are in the circle

mark all handles and the inner circle 
and select unite
then change the outer circle and center circle to engrave
select both circles and choose substract
then you can connect the circle with the rest
 

painted with acrylic paint 
i made the cord with a hangman's knot
this is a very light knot 
you can find many instructions on the internet