I first saw these on Mr Sam The Allotment Mans YouTube video - I like his sense of humour and I have built mine based on the link he had on his early videos
I found out last night that he has now produced his own video on how to make these. I found the cutting of the pop bottles really dangerous using a Stanley knife and I have previous for cutting half way through my left index finger as a model making teenager so I'm really careful and respectful of knifes.
I found a branded cola bottle that I can't really use for building greenhouses and it comes profiled with flutes around the base and in the top which act like guide lines for the cuts to form the blades.
I took the soldering iron to the top and bottom of the side flutes and burnt holes which sealed the plastic and stop it splitting or the cut going too far and then started a slot with a Stanley knife just big enough to get in scissors and cut between the two burnt holes. then I folded each section outwards and an angle of about 5 degrees at the top all in the same direction then repeated the process on the bottom so that when the pop bottle is squashed like a Chinese lantern the two ends match.
I have seen in the YouTube videos that ultimately the fixing of the wire keeps the windmill shape or the use of tape, but I was not happy with that, so I took the soldering iron to the touching ends and used it to weld the plastic together and spot welded around the circumference of the bottle between the blades.
Once done I then creased the ends of the blades flat and welded each blade at the mid point on one side then turned it around and did the same on the other side. I preferred this to the use of tape which may or may not last once wet.
I then cut up three of the bottle tops that I keep from the bottles used for the greenhouse frames into four and stuffed them inside the windmill via the cap. I then drilled a hole in the cap and in the bottom of the bottle for the coat hanger wire.
Wire bent in a loop at the bottle cap end and another bottle cap with hole added to the rear to maintain clearance for the 90 bend in the coat hanger wire and job done... all that now remains is to drill a hole in the top of a timber stake for the wire to go into then the windmill can follow the wind and as it turns the noise from the cap bits inside will hopefully also help to scare the birds silly, it's just a shame it will not work on slugs!.