What you say above only holds true for AC voltage measured with a "True RMS" meter. Most folks do not have access to such a device. Instead, their AC meter may measure "Peak to Peak" voltage.you only need 10 VAC as the input to a full wave bridge to get 14 VDC
you need somewhat less than 20 VAC into a single diode to get 14.5 VDC
You can check out he original B&S patent dating to 1973 for the basis of all 'rectifier/regulators made since then and Byte Magazine for Steve Ciarcia's great article on how to build power supplies.
Jay,One of the best examples of voltage doublers in modern computers is the MAX232 chip,now decades old. It used 'charge pumps' to generate the +12 and -12 volts from +5 needed for proper RS232 communications. lesser known is the 'cheat' to use a timer from a 3 volt microcomputer to generate +5 for the more common(cheaper) 5 volt LCD modules.