[Henry the Hermit]

There are tons of free CAD programs out there. I'm using Qcad, which runs only in Linux, but do a Google search on "easy cad freeware" and there are many free CAD programs available. You don't need much to design slingshot patterns.

Henry

DeltaCad for drawing on a computer.
http://www.deltacad.com/

You can learn it in a couple of nights. It's dead on accurate. I have been using it for many years now, both in my job and at home. It's a great program to use. I highly recommend it.

 

[Henry the Hermit]

Sounds great I run Ubuntu so will give that a try!
Thanx

Cool! You can find Qcad in the Ubuntu repositories.