I've been considering sliding riggers for my next boat.
Sliding riggers, where the rigger and stretcher slide and the seat is fixed, were invented in Victorian times but only became practical in the 1970s. In 1981 Peter Kolbe won the world sculling championship with a sliding rigger designed by Dr Victor Nolte and built by Empacher. Here's a video of the 1982 championship, showing sliding riggers in action. The commentary is in French, but I picked out some talk about sliding riggers being definitely faster than conventional fixed riggers.
They were banned because it was feared that smaller clubs would be unable to afford to upgrade and would drop out of competition.
Sliding rigs might seem overkill for recreational rowing, but they have advantages other than speed. Short boats (mine is 15ft) tend to buck as the rower slides back and forth, especially if he is of average height (6ft 4in) and less slim than he was at age 18 (ahem). The boat loses momentum during the recovery as well. Both these effects are eliminated with a sliding rigger.
A sliding rigger can also be easily detached from the boat and stored in the boot of the car, which makes cartopping a lot easier.
Two sliding rigger systems are available, as far as I know. The Piantedosi system (right), made in the US, and the French Virusboat unit (left).
I suspect that the Piantedosi system is easier to fit (you can buy a kit to attach it to a canoe very easily) but the Virusboat system has the rails wider spaced and may take the force of the oars better.
Does anyone have any experience of either sliding rigger system? If so, do get in touch by emailing using the link over there >>>------->
The most impressive sliding rigger system ever devised must be the Rocat - click here for a brilliant animation - but it does not seem to have gone into production. A pity, but it would probably have been very expensive.