Rudders

(Updated 8-24-2020)

We've had several requests for more detailed information on the rudders for Minimus II. As with most of her construction, they're pretty simple. It should be noted that the method of securing the blade in the up or down position isn't particularly handy for frequent raising and lowering. Initial sea trials indicate though, that it should work well for the sailing we intend (offshore).

Minimus II, being a catamaran, of course has two rudders. Only one is shown and described here. The rudder stock is made from 3 layers of 1/2" (25mm) MDO. The blade is made from a 3/4" x 12" (18mm x 305mm) fir board. Since the blade is made from a single board, rather than glued up from smaller stock, it's strengthened against cupping by 4 pieces of 1/4" x 1" (6mm x 25mm) fir glued crosswise to the grain of the blade. The pivot area of the blade is also strengthened with a 3/4" x 3 1/2" x 12" (18mm x 90mm x 305mm) board glued to the side opposite the stock. Stock and blade are epoxied and the blade is glassed with 6oz. fiberglass cloth. Between the stock and the rudder blade is a bushing cut from a piece of 1/8" x 12" (3mm x 305mm) HDPE (ordered online). The rudder blade is secured to the stock with a 1/2" x 4" (12mm x 100mm) bolt, 4 washers and a wing nut. To keep the washers from cupping under the load, they're extra-thick and doubled. One pair of washers is on the outboard side of the blade and the other pair is on the opposite side of the stock. The fasteners are 316 grade stainless steel.

A doubled piece of 1/8" (3mm) braided polyester cord secures the blade in either the up or down position. The cord is secured to the blade by passing it through holes about 3/4" (18mm) in from the edge of the blade. To secure the blade up or down, knots in the doubled cord go over the end of the forward bolt that holds the tiller to the rudder stock. We plan to put a break-away piece of cord in the line on the forward side of the blade in case the rudder hits something and needs to swing up.

Rudder components from left to right: Rudder stock, HDPE bushing, rudder blade, stainless steel bolt with washers and wing nut.	Rudder stock made from 3 layers of 1/2" (12mm) MDO. The 1/4" (6mm) thick boards glued to the stock allow the bushing to clear the lower pintle. Holes for rudder pivot and pintle bolts were drilled oversize, filled with epoxy putty and then re-drilled to the correct size.
Port rudder blade in up position. The line on the aft side of the blade is taut, keeping the blade up. The line on the forward side of the blade is slack.	When the rudder blade is up, the doubled line from the aft side of the blade goes over and around the tiller. A knot in the line is then secured over the forward tiller bolt. The knot is permanent and doesn't need to be re-tied each time.
Rudder blade in down position. The line on the forward side of the blade is now taut, holding the blade in the down position. The line on the aft side is slack.	Note the block just above the upper pintle. It keeps the line positioned on the center of the rudder blade.
The doubled line from the forward side of the rudder blade goes over the tiller and is secured over the forward tiller bolt. As with the knot that secures the blade in the up position, it's permanent and doesn't need to be re-tied each time.