WARNING:
It is safer to purchase an approved filter rather than risk blindness with a badly made one. Your eyesight is precious - preserve it for life!
Here is a Baader Solar Film solar filter that I made for my WO 80mm ED. It fits nicely over the dew shield. The filter body is made from 4 inch plumbing fittings. The inner ring is cut from a 4 inch pipe and the outer ring/flange is a standard fitting – both purchased at Bunning’s.
Note the 2 foam pads on the inside of the inner ring, to hold the assembly firmly on the dewshield. Do not stretch the Baader solar film - the Baader information sheet states this.
The Baader film is sandwiched between the inner ring and the flanged ring. I pre-formed the Baader film before push fitting the inner ring, so that the Baader film would not be stretched, a no-no in accordance with the Baader Information sheet.
I have also cut two flats into the circumference of the outer flange so the completed assembly now fits snugly inside a plastic storage container.