Demijohn cap with fan

To make vinegar from wine you need a jar/bottle with a wide opening for the required ventilation. However, you can also use a 15 liter, or larger, demijohn which has a narrow bottleneck. For ventilation you could use an aquarium air pump or a wort aeration pump or this 3D printed cap with built-in fan. The fan has the dimensions of 40x40 mm and requires =12 Volts power supply. The 40x40 mm fan provides ennough air flow. You could use larger 50x50 or smaller 30x30 fans. The fans height can be any (10-20 mm).
Power Adapters starting from =7 up to =12 volts are also sufficient. Fans are available from 2.50 Euro and lower.
The opening of the cap, with the fan, must be covered with a cloth to prevent fruit flies and other pests of entering the demijohn. The cloth can be cheesecloth, some other air-permeable cloth or some very fine netting.

To customize it to your needs better install Openscad on your computer and load the script BottleCapWithFan.scad. Somehow the Customizer displaye