homemade downrigger?

[10 brownie points]

All, I was wondering if anyone has a homemade downrigger?
The mechanism of a downrigger doesn’t look that technical, the main parts appear to be the arm (or boom) some kind of spool and the right type of wire..
Could anyone suggest what could be used as replacements for these parts?
Has anyone had a go, if so do they have any advice and/or pic’s?
There is a recession on, you know and any advice for saving a few bob is welcome.

[jw]

you could just use 10 or 15 heavy leads and lower it on a piece of string to the desired depth.
this will work just as well as the expensive gadgetry

[fergalb]

How about this one looks like an easy build.