The log reel was used to measure the speed of the ship.

It had a long rope wound round it. There were knots in the rope every 7 fathoms (12.5 metres) and a piece of wood called a "chip" tied on the end.

One man held a sandglass, another held the reel and the third threw the chip over the side and counted the number of knots that went overboard in 30 seconds. (A ship's speed is still measured in knots today.)

Could you make your own log reel and test it by running across the playground?