I love sailing but it does have a serious downside. If the wind is good you get great exercise and exciting racing. If the wind is low it can get rather dull and fail to provide much physical challenge.

So these boats, pictured at Cowes Week in 2050, are Modern Viking boats. If the wind is strong they sail. If the wind drops the crew row. At intermediate strengths, as shown here, they sail and row simultaneously. Two of the 6 crew keep the boat level, 4 row.

The class doesn’t only provide a great work out, it also provides lots of interesting tactical opportunities. There would be a need for rule changes – for example oars must be stowed close to marks.

I guess the same principles could be applied to smaller and larger boats, up to full Viking size with perhaps 50 crew.

Like everything on Sketchfifty, this type of sailing is sustainable. No need for engines, and little need for rescue, because these boats are seaworthy.