Given the relaxed attitudes of the crews, these dhows clearly aren't racing for home at all. In fact, given the general pace of life in Zanzibar, I think it unlikely these guys ever race anywhere. Still, had they been, they would have been about half a length apart.
This is one of many photographs I’ve taken of dhows just like the two here.
This image is supplied with a substantial border with the title printed in the centre at the bottom.
Picture sizes are to the nearest inch.

Half a Length, Zanzibar