Below:The beam set-up used for cruising by Malcolm Droy (see Cruising the SW Coast)  with an additional rear beam on the
boat  allowing him to have a small 2hp motor for work against the tide. It is high enough to avoid waves hitting it and allows the rudders and tiller bar to stay in place. Below right: the beam Mark 2 (as Mark 1 was not stiff enough at the beam end) sealed with fibreglass resin

  Below left. Alastair's engine mounting plate, sitting on the rudder pintles. This is secure and very simple to make. (The block does not rotate on the pintles.) There is no problem having the engine on one hull, as the slim hulls run true. The engine has a lengthened tiller, and tiller extension, to allow weight to be well forward.

  It is good for stowing the little mount unit and the engine, on the trampoline, and can be mounted while on the water---but this requires leaning well back holding the engine, so only a small engine (a 2.5hp Suzuki in this instance) would be possible. Obviously the rudder and tiller bar are unshipped (see also next example, below.)

Above right: Chris' engine is on a wooden plate and block clamped around the rear beam. It allows the engine to be put on and off while on the water. The tiller bar is removed. The potential diificulty is that the securing bolts for this sort of solution need to be very tight, to stop the mount rotating round the beam under load.

(The photo also demonstrates the perils of managing sail and power when the rudders are not separately controllable---the power of a gust, after the fleet was out of the wind-shadow, has spun Chris into the Oulton Dyke reeds. Chris is managing the situation with his usual sang-froid.)

Rowing:  Catapult also easily manoevres by rowing, (photos below) when the challenge is narrow spaces rather than tides. The rowlocks set up by Alastair for Thames cruising  fit into fairleads screwed simply on the beams, and the width of the boat is just right, to scoot the boat along.

The rowlocks are kept on the oars (as they could give a nasty injury left in the mountings!) and the oars sit easily-enough on the trampoline along the rear beam.

The fore-and-aft position of the oars on the boat was guessed-at, to give a reasonable bows-down trim, and the boat moves very easily---but with the position well forward, rowing with the sail up is awkward, and so the oars are used with the sail furled, in locks and narrow sheltered channels where the breeze is masked..