This is the bill of materials the first version of the USV-01 build:

#	Item	Unit Price / £	Unit Mass / kg	Qty	Total Price / £	Total Mass / kg
1	HobbyKing Marine Scott Free Offshore Racing Deep V Racing Boat 730mm ARR	108.57	1.2	1	108.57	1.2
2	Turnigy 4000mAh 2S 30C Lipo Pack	12.86	0.254	2	25.72	0.508
3	FrSky X8R 8/16Ch S.BUS ACCST Telemetry Receiver W/Smart Port	22.87	0.017	1	22.87	0.017
4	Raspberry Pi 3 ∗	32.00	0.045	1	32.00	0.045
5	CJMCU uBlox 6M GPS & HMC5883L Compass module	9.66	0.02	1	9.66	0.02
6	USB Servo Board ∗∗	15.47	0.01	1	15.47	0.01
7	Edimax EW-7711UAN Wireless nLITE High Gain USB Adapter	17.87	0.03	1	17.87	0.03
8	Pololu 4-Channel RC Servo Multiplexer	6.86	0.01	1	6.86	0.01
			Total:		239.02	1.84

∗ I’m using a Raspberry Pi 2 in my build because I had one lying around, but if you’re starting from scratch there’s no reason not to go for version 3. Note that while the Raspberry Pi 3 has on-board WiFi, its antenna is tiny, so I would recommend using a WiFi USB dongle with a large antenna anyway.

∗∗ Currently, my build is slightly different in that it uses the GPIO-mounted version of this, not the USB version. The disadvantage of this is that it takes up the Pi’s UART, so a separate USB to UART adapter (CP2102) is required to communicate with the GPS. This is just because I had the bits lying around so could save some money—if starting from scratch, I would use the part listed here.