[ZDP-189]

The old saying goes "Aluminium is 1/3 the weight of steel and 1/3 the tensile strength". Seeing as you should want some bulk to the slingshot, I'd use aluminium if making a large plate slingshot or steel if it's steel rod slingshot and you want some heft. These are just my preferences. Either material will be affordable, if you can find a right sized offcut to work from.

If you can use AutoCAD, that's best, but seeing as you're asking, you probably can't, so you may as well draft it in any way you can that leaves sharp clean lines because whoever's making it for you will have to digitise it.

 

[ZDP-189]

Can Google Sketchup output in, or be converted to Autocad?

 

[ZDP-189]

Great job both of you! That's what I have in mind( my own design) of course!
Have been playing with the emachine software now and it does not seem to hard, but it will probably get to expensive...
A shame... It could have been a great way to get metal slings for us without tools...(knowlege)
well great job they both look nice! I realy lkie the chiny metal=) BlingBling

Yeah, they look expensive, but they are really designed for people doing prototypes, high value custom jobs, reproducing unavailable discontinued machine parts.

If you are considering making a slingshot that is hand cut from metal plate, you will need to learn to hand-draft accurately enough for someone to scribe the profile out on the plate. Either that, or get some Formica or a thin sheet of aluminium and make a template on that for someone to scribe around.