I was involved in three new designs this year.  One used the 4 stations driving two props through bike chains and toothed belt.  Another used just a chain with single pedal station and the third used a single station with two gearboxes.  The 4 pedal station was pictured in an earlier email.  The other two below.  All three finished the race with drives intact albeit with some maintenance.

My curved shaft arrangement suits fast pedal boats where drag on the in-water parts can be a significant factor in the total drag.  They are also designed for the pilot to face forward.  On a sailing boat there are more seating options; facing sideways or even backwards.  On a sailing boat it is desirable to motor sail up to the limit of your peak foot speed, around double the design pedal speed.  On fast sailing boats you need to be able to easily get the prop out of the water once speed builds.  If using cleats (i always recommend them in recumbent pedalling) it can be dangerous to be cleated when the boat takes off because it is impossible to stall a big prop once it becomes a turbine.   The photo below showing the leg with two gearboxes, shown in the up position, swings backwards and upward as soon as it is no longer providing thrust against the transom.  This is a lesson learnt years ago with pedal drives on the 8T peccadillo that was pedalled at 2.5kts with two stations but could accelerate to 8kts or more in a flash.  It had 700x400 props with a 2X ratio and there was no way the human engine could stall those props once the boat exceeded the foot speed at about 5kts - very dangerous for the pedaler.

The majority of the bigger R2AK boats are now using pedal drives rather than oars.  Some of them are sparing no expense in getting reliable, efficient drives. If you GOOGLE R2AK pedal drives you can usually find videos and photos.  Many of the teams have their own Facebook page and they usually have photos of drives there.  Russell Brown provided a photo review of the 2018 pedal drives:

Of this bunch, his and Matt Johnson’s were the only ones I provided specific design detail on.  But I have a lot of information on the web that allows knowledgable people to have a good go at a design.

You can get any size boat to move under pedal power but sustaining a given level of output takes some training and good basic fitness.  The sustainable specific power of a human is about 2W/kg.  Humans are less fuel efficient than a diesel engine.  On the other hand there should always be enough fuel to sustain the human to work at rating for hours at a time ON DEMAND.  So human power can be a reliable, effective form of propulsion for some circumstances, as the R2AK demonstrates.   

Rick