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June, 2005
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Tribal Menace
By Chris Ostlind

WaterTribe Rudder Contender
By Larry Miller







WaterTribe Rudder Contender

A Kayak Rudder Conversion

By Larry Miller (aka PaddleFoot)

Does a WaterTribe Rudder already exist? Scanning through the WaterTribe Rudder Discussion Forum, I see that most of the requirements mentioned are met by the rudder I designed and built five years ago. Having built two more since then, the design is now fairly refined. Were I to build another, there is little I would change, unless to try a foiled blade or eliminate a few more ounces of weight. Although I designed this rudder to give an old pointy-ended river kayak a new life as a sailboat, it could be adapted to most kayaks.

A flat-blade, hard-anodized
aluminum rudder for sailing

When I ordered my first Balogh Sail Designs sail and BOSS rig, Mark Balogh recommended a commercially available kayak rudder and provided a template for a balanced blade suitable for sailing. After considering the modifications necessary to adapt the commercial rudder to my 20-year-old fiberglass Phoenix Cascade, and the need to cut a new blade, I decided that the effort would be better spent starting from scratch.

Working in AutoCAD, I designed a prototype and brought it to the October 1999 Sails Angels gathering. It worked well, so I returned home and built another, trimming a little weight, using a stronger alloy and having it anodized. The third one I built in the summer of 2002 for my wife's Phoenix Savage, an old 25-pound, thirteen-foot fiberglass whitewater kayak, also equipped with a Balogh rig. This is the one shown in the accompanying photos.

These rudders have proven to be strong, effective, durable, convenient and trouble-free. Our kayaks are responsive, maneuverable and fun to sail. Tacks are quick and never require a paddle assist. We can sail within 50 degrees of the wind, sometimes better. Turns require little foot pedal effort, even when surfing beyond hull speed. And, though it might be like that face only a mother could love, I think they look pretty good. Following are the WaterTribe requirements paired with descriptions of my design.

Strong and Tough

After slightly bending the mystery alloy blade used for my prototype, I switched to 6061- T6 aluminum. Since then, there has been no bending or detectable flexing. The blade is 1/8-inch plate, the yoke or rudder bracket 3/16-inch angle, and the remaining parts are from 3/16 or ¼-inch angle and bar stock.

Twenty percent of blade area
 is forward of the pivot

All aluminum parts are hard anodized for corrosion and abrasion resistance. Unlike the more colorful regular anodizing, hard anodizing leaves a two-mil thick dark gray-green ceramic coating that is harder than steel. It has yet to wear through on the tip of the rudder blade.

Foot or Hand Control -- and Self-Steering

 The steering cables attach to the rudder yoke three inches from, and in line with, the pivot axis. Just inboard of each cable pin is a hole for attaching a rope used to steer by hand or to lash the helm. For rope steering on a regular basis (I rarely use it), the holes should also be on a line with the pivot axis to keep the steering rope from slackening while turning.

Cable steering with rope
holes for backup

Easily Removed and Installed

When finished sailing, the rudder system can be quickly removed and disassembled without tools. Only the gudgeon bracket and foot pedal guides remain fastened to the kayak. Pulling the pintle pin releases the rudder from the gudgeon bracket. The blade axis pin is secured with a cotter ring, so the blade is easily removed from the rudder bracket. Two more cotter rings secure the steering cables to skirted pins on the rudder yoke. The forward ends of the steering cables have small swaged cable stops that are fed through Teflon tubing to the foot pedals. At the foot pedals, the cable stops fit into keyhole slots; no fasteners are needed. Everything is easily removable for rinsing and highway travel. Installation is just as easy.

These parts are removable
without tools

Balanced Blade

The rudder blade is balanced, with 20 percent of its wetted area forward of the pivot axis. For most of its length, the blade is 7-5/8 inch wide. It extends about 14 inches below the waterline, for a total wetted area of approximately 103 square inches. This is 2% of the area of the 36 square foot sail I use in light winds or about 2.5% of my 28 square foot sail. This is more than enough area for our kayaks.

The wetted portion of the blade is basically rectangular. The trailing edge is straight from the bottom up to where it curves aft to meet the pulley. Because most of the blade is forward of the blade axis (the "kick-up" axis, not the pivot axis), a rectangular blade would initially increase in depth as it swings back upon hitting a shoal, stressing the rudder mount. To prevent this, as well as to spread wear over more of the blade edge, the bottom end shape is one quadrant of an ellipse.

A Solid Stern Mounting System

Securely fastening the gudgeon bracket to the pointed stern of the kayak was a major challenge. It was necessary to saw one inch off the end of the kayak to provide a flat, vertical mounting surface of approximately 1-1/2 square inches. Two quarter-inch stainless tee-nuts were imbedded two inches deep in a glass-reinforced end-pour, perpendicular to the mounting surface. Two more tee-nuts were imbedded in a second pour, opening to the deck of the kayak. Quarter-inch screws and bolts secure the bracket to the kayak.

Every boat requires some sort of custom rudder mounting arrangement. What makes my design fairly adaptable is the small, but very strong, gudgeon bracket. Because of the kayaks' pointed sterns, I provided additional bracing to the decks. Most boats would not need this. When a vertical surface on the stern is not an option, a bracket having a vertical surface might be mounted to the stern, much the same way ordinary gudgeons are sometimes bolted to a hull. An advantage to this arrangement is that the bracket could be provided with multiple mounting-hole sets, so that mounting height could be adjusted to compensate for varying displacement or to fine tune the balance between the centers of effort and lateral resistance.

Give for Collision with Underwater Objects and Ability to Raise or Lower the Rudder from the Cockpit

The system for absorbing impacts shares components with the system for raising and lowering the blade. To minimize the forces required in both systems, I used a fairly large diameter pulley. The blade top forms one pulley face; the other face is formed by a disc of aluminum, with a smaller, 5-1/4-inch disc of Plexiglas between.

A continuous loop of rope is fastened to the Plexiglas disc. This haul loop provides a means to hold the blade down, as well as haul it up. The forward portion of the loop passes through a small block adjacent to the cockpit. This block is held by a small adjustable loop of rope encircling the cross-tube of the BOSS rig. The primary purpose of this small loop is to adjust the slack in the haul loop, but by adjusting it to its maximum diameter, it can be slipped over the end of the cross-tube without untying the knot, simplifying installation and removal of the rudder system.

While sailing, the blade is held down by a length of shock cord attached to the lower half of the haul loop. A short length of rope is tied to the forward end of the shock cord. This line passes through a fairlead directly behind the cockpit, and is secured in a cleat to the right of the cockpit. Tension on the shock cord is adjusted initially by sliding the knot along the shock cord, but can be fine-tuned underway by varying the position of the line in the cleat. Since the working length of the shock cord is nearly four feet, tension in the cord increases only 8% as the rudder swings back to a horizontal position.

Cleat by cockpit swivels to
align with either the shock
cord lead or haul line

The rudder hauls up easily regardless of steering angle. Hauled up, the rudder blade comes to rest 20 degrees past vertical. With the shock cord released, gravity holds the blade in its rest position against a step cut into the blade. However, the blade can be secured in this position by fixing the haul loop in the cleat that is normally used to tension the shock cord.

Unlike some rudder designs, the rudder bracket does not completely enclose the rudder pulley. This allows a larger sheave diameter without a corresponding increase in bracket weight. It also eliminates friction between the haul rope and the rudder bracket. By maintaining small clearances between the bracket halves and pulley faces I have avoided any twisting and side-to-side slop. Teflon sheet between the pulley faces and bracket halves minimizes friction.

Sandwiched between the rudder bracket halves is a block of Plexiglas that serves as the bearing for the pintle pin. The pintle pin passes through a vertical hole in the block. Teflon sheet provides a bearing surface between the top and bottom of the rudder bracket and the gudgeons.

The most innovative feature of the rudder is the integration of the line guide bracket and the pintle pin. The stainless steel pintle pin is permanently threaded into the bottom of line guide bracket. The line guides carry the upper and lower halves of the haul loop. The line guides need to be located on the axis of the pintle pin. This location prevents a turning moment on the rudder when tension is applied to the haul lines. It also prevents a change in tension or slack in the haul lines as the rudder is turned. The base of the line guide bracket bears against a step on the upper gudgeon, keeping the line guides oriented fore and aft. This also prevents the pintle pin from rotating so that there is no wear between the stainless pintle pin and the aluminum gudgeon.

Forming the line guides bracket and pintle pin into a single assembly has further advantages. Tension in the haul loop holds the pintle pin in place. The safety pin at the tip of the pintle pin serves only as a backup. The rudder blade, haul loop, haul loop block, adjustable loop and the line guide/pintle pin assembly all actually form a single assembly, so that when removed, the various parts cannot become separated and misplaced.

Although the upper line of the haul loop passes straight through its guide, the hold-down half of the loop passes through the lower line guide at a sharp angle. To reduce friction and line wear, I used ceramic fishing rod line guides. Despite the sharp angle, even slight tension will return the rudder to vertical after passing over a shoal. Without the need to overcome friction in the system, shock cord tension can be minimized to reduce wear and the risk of damage to the blade. With well-faired holes and a good hard-anodized coating, it might be possible to omit the fishing rod line guides.

Fishing rod line guides
minimize friction

Stop Ensures Vertical Orientation

To maintain the intended rudder balance, the blade must remain vertical while sailing. This is accomplished by providing a step in the forward part of the blade under the pulley. The Plexiglas block serves as the stop for the step so there is no metal-to-metal contact. Shock cord tension holds the step against the Plexiglas block. Because the blade axis is well aft of the blade center-of-gravity, some tension is always required to hold the blade against the stop.

There is no means included to adjust the stop position. My experience with this rudder indicates there is nothing to be gained by fine-tuning the balance with an adjustable stop. Mark Balogh recommended twenty percent balance, and, at least with this design on my boat, twenty percent seems optimal. An adjustable stop could be included, but I don't believe the increased complexity is justified. Slightly more pedal pressure, or slightly less feedback, would still be acceptable in any of the conditions I have sailed.

Switching Blades

Haul loop attachment method

The blade is easily removed but the haul rope is more or less permanently attached to the blade. A three-inch fold of the rope is captive in a keyhole slot radially disposed in the pulley's Plexiglas disk. A small plastic bead in the end of the fold keeps the rope in the keyhole. Six screws would have to be removed to release it. However, since all tension on the rope is perpendicular to the slot, it should be possible to dispense with the keyhole and provide a simple slot. The fold of rope could be stiffened with resin or wire inserts to keep it from pulling from the slot under normal use, yet it could be pulled straight out of the slot to change blades, with no tools required.

Stops to Limit Rudder Travel

Padded rudder stop shaped
to match yoke leading edge

Milled into the gudgeon bracket are padded stops to limit the maximum turning angle of the rudder. The leading edges of the rudder yoke are scalloped to provide about 60 degrees of turning angle to either side on my kayak. This is more than needed. I limited the travel to about 45 degrees for my wife's kayak.

Connect Two Yokes Together when Catamaraned

The yokes of two rudders could be interconnected by providing a set of holes in the rear of the yoke, widening the yoke if necessary to accommodate the holes and hardware. Only one hole per yoke would be required if the parties involved could agree on who was port and starboard.

Minimal weight

Although I reduced the weight with each new version, at 4-1/2 pounds (excluding the foot pedals), the system still seems a little heavy for a small, lightweight kayak. There are possibilities for further weight savings without compromising strength or function. These mostly involve more complex shapes or extra holes. I decided not to take advantage of these primarily to avoid all the extra hand sanding of edges than cannot be reached with my bench sander. Well-rounded edges are important because the anodizing won't build to the desired thickness at sharp edges.

Additional weight savings could be realized by reducing the size of the pulley and rudder bracket. The downside is that this would require a small increase haul-up effort and shock cord tension. It would also reduce the chord of the blade slightly at its narrowest point, just below the pulley.

For small kayaks like these, I believe the blade size could also be reduced for a little more weight savings without hurting sailing performance.

Field Repairs

The most likely problem underway is cable connection failure. A spare set of cables could be installed in just a few minutes, but it would be more pragmatic to rely on rope steering as a backup. If one has no extra rope, the haul loop could be cut away and used for a steering rope.

All screws and bolts fit into threaded holes. There are no nuts to loosen and fall off.

Lost cotter rings could be replaced with string or a bit of copper wire. Drilling slightly larger holes in cable connection pins would enable the cable ends to be bent around and used to replace a lost cotter ring.

A lost rudder blade or pintle pin is unlikely since both are connected to the haul lines, but a suitable bolt could serve as a replacement pintle pin.

Carrying an extra blade axis pin would be smart. Forgetting to attach the cotter ring, which would be dumb, could deep-six the blade pin.

Foiled Blade Possibilities

Until reading about foiled blades in the Forum Discussion, I was unaware of their benefits. When sailing, I sometimes feel I loose too much momentum during a tack. Now I wonder how much of this loss is due to rudder drag that I could avoid with a foiled blade.

Another reason to consider a foiled blade might be sail plan balance. With the standard BOSS rig, the leeboard is immediately adjacent the mast. So, with the leeboard vertical, there is a lot of weather helm. However, when the rudder is lowered, the center of lateral resistance moves aft of the center of effort. So, theoretically (I can't tell in practice), the rudder needs to be angled a little to the windward to keep from bearing-off when on a reach. I suppose a foiled rudder would reduce the extra drag caused by this. Possibly I could foil the rudder by laminating foam foils to either side of the flat blade and glassing over them.

Home-Built at a Reasonable Cost

Except for the anodizing, I built this rudder in my basement. Although the success of this design is dependant upon precise dimensions and alignments, I was able to accomplish this using ordinary Sears shop tools, a few tricks and a lot of forethought before each operation.

I spared no expense obtaining the right materials for the last rudder and probably spent as much as I would have for a commercial rudder. But, considering the end result, it was worth it. Purchasing minimum order quantities over the Internet, I spent $38 for the aluminum. The Teflon sheet and tubing were expensive, about $40 from my source. Anodizing cost $30, a bargain for the value added. All the various stainless parts, rope, cable, line guides and Plexiglas added another $50 to $100. A determined scrounger could do a lot better


What now? I have had some minor design modifications waiting in AutoCAD for a couple of years, but only to address weight reductions. The weights of the current rudders are not really a problem, and having no more kayaks, I have no immediate plans to build another rudder. Nonetheless, I am interested in hearing anyone's thoughts about the design or its suitability for other boats. I have been eyeing those beautiful CLC kayak kits for several years now, and I wouldn't want anything less than the perfect rudder for a project like that.

© Larry Miller 2005



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