# Relation between the hole in a semispherical parachute and the area of the parachute and drag coefficient of such parachutes

I can't seem to find much information regarding the size of the Vent (the hole).

Nor can I find a concrete answer to the value of the drag coefficient, $C$. I've read in some websites that $C$ is usually around $1.4$.

If someone could tell me, or, better yet, point me to some sources (books that are readily available on-line, or websites, for example), it would be deeply appreciated.

Thanks.