Proa Rudder Concept

Proa Rudder Concept

This is a concept for a proa rudder that can retact and also kick up on grounding. The lack of this kick-up on grounding feature is im my humble opinion a major flaw in the CLC proa's Mbuli and the newer proa Madness

The rudder concept works as follows.

A rotating drum is placed in the boat. This drum will require a casing of some sort to keep it in place (not shown). Through this rotating drum a stainless steel rod is threaded. This rod becomes the rudder blade pivoting rod. The aft end of this stainless steel rod has the rudder blade bolted onto it. Fowrard of the stainless steel rod a fixed wooden skeg exists. Obviously there would need to be attachments between the skeg and the stainless steel rod.

The wooden skeg protects the rudder blade from any impact damage.

To steer the boat the aft rudder is deployed (one line to lift and one to raise should be sufficient for this). To steer, the rudder blade is turned via a yoke which is at 90 degrees to the stainless steel rod. The yoke is then activated by a push-pull rod. Thus to turn the rudder blade the push-pull rod is moved backwards of forwards, the yoke then moves with it, which in turn rotates the stainless steel rod and the pivoting rudder blade which is rigidly attached to the stainless steel rod.

You may notice a small notch at the top of the pivoting rudder blade, it is at 45 degrees and not horizontal. The reason for this is that there is a chance that a grounding may occur then the rudder is being turned.

The 45 degree angle should force the rudder blade inline with the skeg as the entire rudder assembly is rapidly forced back into the casing on grounding the rudder at speed. Without this 45 degree angle there is a chance that the blade might catch on the hull if the blade was not straight and a fast heavy grounding occured thus rendering the entire concept null and void

Although it may sound confusing, I think it the idea has merit. As on 6 January 2013 when I put this page up, I think I will do a 3D freehand sketch that better explains the principle. Please give me a couple of days to do the sketch though (been a long time since I sketched something with pen and paper)

The hull of the proa would only require a 27mm wide slot (25.4mm plus clearance) for the rudder mechanism. Having the rudder blade in the hull improves rudder ventilation issues and imparts greater structural integrity than would side mounted rudders

Issue with rudder not straight and then sudden grounding occurs

There may be occasion when the rudder is being turned and at that moment the sudden severe grounding occurs. Well the above sketch is an attempt to overcome any issue with the blade catching. Because of the angle of the blade, the further the blade moves aft, the more of the pivoting section moves into the slot. As the blade moves into the slot it will be incrementally straightened, thus in theory stopping any catching issues

It should be noted that with this setup that the drum has a loose fit and is just there to keep the board in place, main loads which are to leeward and to windward and absorbed at the top and bottom of the board section which is inside the hull