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How to replace an older rudder

Dec 9, 2011

To solve the steering problems we’ve noticed over the years, we needed to reconfigure the rudder setup on Copernicus, our Spencer 42.

We contacted Eric Sponberg a yacht designer and engineer ( and asked him to design us a new rudder. Sponberg designed the very successful free-standing carbon fiber mast and sail plan for Copernicus. Sponberg’s design was a fairly high aspect carbon rudder with a tapered carbon fiber tube that was six inches diameter where it exited out of the rudder and tapering to three inches where it exits through the deck.

Composite Solutions Inc. was chosen to build the rudder. I had to do the keel and hull modifications to accommodate the new rudder. My plan was to get all the work done in a month with an overrun (should things go pear shaped) of another two weeks if needed.

In that month I needed to:

1. Take out the old rudder and hydraulic steering gear.
2. Remove the entire bustle since it would cause turbulence in the water flow.
3. Reinforce the hull with a new rudder tube as well as install said tube.
4. Install the upper rudder bearing and reinforcement.
5. Install the rudder and have the tiller cap/fitting built as well.
6. Fair in a new vertical trailing edge to the keel.
7. Make a bulkhead watertight. Since the hull would be empty and accessible at that point I thought that making the bulkhead aft of the engine watertight would make the bulkhead watertight and reinforce and tie in the shaft log to the bulkhead, making the whole structure integral and stiffer.
8. Paint the cockpit if I had time. Since the cockpit was already trashed and would be worse when this was all over I would fair and paint it.
9. Replace two through hulls and seacocks.
10. Remove a seacock and through hull that was no longer in use.
11. Install transducers for new depth and speed instruments.

Day one of the haul out consisted of measuring and cutting out the hole for the rudder tube, which was approximately one foot in diameter.

I used laminating epoxy for all the glass work along with release fabric over the fresh glass work at the end of the working day. Whether it was to be a secondary bonding surface or a finished surface, I would put release fabric down.

I then spot glued in the tube with quick-set epoxy. The self-aligning bearings were from Jefa bearing systems. They had a very good install diagram and rough lam schedule on their website that I adapted with a bit of beefing up.
A fillet of high-density epoxy came next to further tie the tube to the inside of the hull. The radius of this fillet was sufficient to allow the first set of alternating Knytex and 24 oz. cloth to readily change direction from the inside of the hull to the 90 percent cylinder walls of the tube.

I then added a second high-density larger diameter fillet at the tube/hull joint over top of that glass. A second set of glass was then layered and tapered over that second fillet to give a finished thickness of about an inch and a half. These finished layers tapered out over about three feet in a radiating pattern from the tube.

With the tube glassed in, my next job was chopping out the bustle. It originally was the wineglass flare that extended down from the canoe body to the top of the original rudder and included the old rudder bearing tube. To get back to a proper set of faired lines on the canoe body in way of the bustle I was going to have to cut out a hole approximately nine inches by 39 inches. That’s a big hole in the bottom of the boat — now I was properly scared, or perhaps nervous is a more accurate description. I tapered back from the edges of the cut on a 20 to one ratio. I then spot glued a piece of high-density foam into the hole from the inside, fairing that from the outside.

Twelve tapered layers of Knytek and 24 oz. cloth on the outside later, I was able to grind the foam away from the inside and lay down about 24 layers tapered out about three feet out from the cut port and starboard. Extra tapered strips along the center line inside brought the finished thickness to about an inch and a quarter minimum. Time would not allow me to do more than a two-step fairing process on the outside.

I moved back into the cockpit to finish the top bearing assembly on the aft cockpit seat. For this part I cut the top bearing hole. I then cleaned out the core back about two inches in from the edge of the cut out. It was then filled with high-density epoxy filler. Two layers of half-inch G-10 were stacked on top of a freshly ground cockpit seat. These two pieces were large enough to spread sheering loads across a fairly large area. The bearing was then bolted down.

Three weeks into the job, I could see that if I did all the work in series I would not get it all done. I decided to hire a local glass guy to come in and glass and fair out the trailing edge of the keel. I had money in the budget for this work to be done third party so it wasn’t a big shock.

My girlfriend, Carey, was coming over on the weekends to give a hand and calm things down. She would merrily cut cloth, advise and hand tools off along with jumping on her bike to get stuff I forgot.

About two weeks into the job, I contacted Frank Tremblay of Classic Welding who, with starts and stops, built a beautiful tiller/rudder head unit. Because the SS sleeves that came with the rudder were machined to the diameter of the carbon tube, which didn’t have standard pipe dimensions, all the work had to be machined from scratch.

Getting the rudder ready to be installed was next on the agenda. The chafing sleeves that protected the carbon tube from chafing against the roller bearing were glued in place on the rudder post along with a cap of G-10.
The three-quarter-inch tiller through bolt hole was drilled into the top part of the carbon tube at one-inch diameter to accept a three-quarter-inch inside diameter G-10 compression tube. A SS cap with a three-quarter-inch hole to take the tiller bolt was glued over all to prevent any chafing or rubbing from the tiller cap.

I was keeping track of the weight of stuff as it came out of the boat as well as the weight of stuff as it went into the boat. My guess is that we shaved about 250 pounds of old steering gear, etc., out of the aft end of the boat, perhaps a bit more. I can certainly see the stern is sitting a bit more out of the water now. My way of dealing with the trim was to try to get weight out of the bow as opposed to just putting more stuff in the stern.

Everything came together while counting down to a month of being out of the water. On launch day, the rudder was not yet installed. Tremblay of Classic Welding came through, saved the day and helped install the rudder. I locked it down with the set screws, tiller cap, bolt, tiller — and bang, the boat went into the water!

Bryan Pollock also wrote:
Two years before the mast