Rowers and in particular competitive rowers have always tried to improve efficiency. Many modifications to traditional rowing crafts have been tried.
Competition rowing boats have been lengthened and made narrower and lower with great success but the modern rowing shells are quite tippy and sensitive to waves. Rowers have tried putting footrests and that gives the rower something to push against. Sliding seats have been a great success in improving the efficiency of boats because they allow the rower to use powerful leg muscles to aid in pushing the oars. Before sliding seats were developed some rowers would grease the seats and slide back and forth. Rowers have also tried to modify the oar locks so that they move instead of the seat also with great success.
What is a Sliding Rigger
Riggers is the name competitive sculling boats and shells use for the oarlock assembly. In narrow boats it often sticks out from the gunnel to improve the position of the oarlocks.
In order to allow a rower to use the wonderful strong leg muscles, the oarlocks are sometimes placed on a sliding carriage linked to the footrests. By pushing on the footrests the rower can use leg as well as arm power. The oarlocks slide back and forward while the rower stays in one spot not shifting the major mass of his body.
Why not use Sliding Seats?
Sliding seats are the norm and widely used. They have a disadvantage however. Because the mass of the rower moves forwards and backwards the boat has a tendency to bob up and down. It is said to dolphin or hobby horse. The longer and heavier the boat is, the smaller the bobbing is. In shorter boats the advantage of using a sliding seat can be offset by the wasted bobbing motion.
The video on the left shows a 1982 competition where the rowers were using sliding riggers. It's in French, but has good images. At one point they are discussing the boat and claim that they are faster. They also mention that there will shortly be a ruling about the sliding riggers. We know they were banned from competition shortly after.
It's not clear to me exactly why but I don't think anyone uses them. One argument I heard is that although the rowers go faster the order of the winning boats does not change. Everyone goes faster but the same guys win. (as long as they are all using the same kind of boat) Now sliding riggers are used by serious rowing amateurs who prefer to have shorter boats. Shorter boats are easier to store, move, and transport, as well as usually being cheaper to purchase.
Sliding Seat Video
Rowing with sliding seats on left clearly shows the boats bobbing motion. This is from the Beijing Olympics. Still blindingly fast though!
How Long have Sliding Oarlocks Been Around?
Michael Davis of Portland Maine applied for a patent for a sliding rigger/foot-board with fixed sea in 1877. So the idea has been around for a long time.
Are Sliding Oarlocks Available Now?
RUM International has a Sliding Rigger They are located in Florida. Their unit sells for about 1000 US. It's worth having a look at their website. They have a nice explanation on the principle of the sliding rigger.
Alden Rowing from US. have another version of a sliding rigger. Their unit can be adapted for mounting on canoes and other narrow beam boats. Their unit is about 700 US.
NOTE: Sadly, there appears to be a considerable number of Alden unsatisfied customers. Link to complaintboard.com. It appears the mechanisms are well made and perform as expected but the business side of the operation is failing to ship and respond to inquiries and complaints. Caveat Emptor.
One fact that all the manufacturers mention is the need for a good seat. Not only is there more pressure with the danger of blisters and irritations, but it is also possible to slide right off the seat if it is not cupped or slightly angled to retain the butt firmly in place as you row.
The Row Surfer allows you to add a rowing rig onto a canoe, kayak, board or any other suitable craft. They are located in The Netherlands, Amsterdam.
Wander through their nice website with lots of information.
Clovelly Sculls UK, use a Rigger system. Their website has several videos of their system and boat. They describe their boat as "A sporty single scull for rowing on open water"
Inventions and prototypes
Not available commercially but clever is the ROCAT designed in the UK
It has the advantage of being very stable.
More leg powered rowers
Several people have worked on the design and some fascinating prototypes have been made. Here are a couple.
Simon Farthing has designed a leg and arm rowing system that also has the advantage of letting the rower face forward. Here are a Youtube video of his forward facing rowing system including leg push. I think his position is a bit too high but it's really interesting.