Shield rim help

[inblackandlace]

I'd like to make a shield to go with a suit of stahlrim armor I'm making. Problem is, I don't know how to make the rim of it. I want it to be perfectly round so I don't trust myself to draw it out (it needs to be about 3 ft in diameter). I thought maybe a small sliver of one of those industrial sized PVC pipes? They're about $300 a piece though. Any suggestions?

 

[Shipwrek]

Queen's Blade - Risty Mace & Shield Build for Jessica Nigri - YouTube

There is a similar build in this series. The pin method can be done using a string and then cut and sanded by hand out of any flat stock. (Plywood, foam, plastics, etc)

 

[Alexfx]

Dunno if I'm following you correctly or not, but you want a rim for a round shield? Have you made the shield? Why not just draw around it? Or pin and string, or even cut a flat strip of (whatever you wanna make it from) and wrap it around... If I'm not mistaken the metal rims of round shields were traditionally bent around the existing shield?