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Repairing the Aluminum Rudder on Jim Oppy's Wisp, a Lunn Built Boat  

July 4, 2010. Jim Oppy's Wisp is a Lunn built boat with an aluminum rudder that has significantly corroded over time due to galvanic action. Here is his repair project and photos with his (edited) email comments inserted as appropriate.

I got at the delaminating fiberglass on the rudder, and it has basically disintegrated from galvanic corrosion. It’s an aluminum rudder, wrapped up in 50 year old fiberglass, which is yellowed and brittle on the outside, and soft and powdery on the inside. The aluminum encased in glass is actually pretty solid over 65 % of the rudder, but at the bottom where it counts the most it failed completely. The rudder post heel fitting came apart, and it became apparent that the rudder must come out and be properly repaired or replaced.


I got as far as removing the rudder post heel, which is heavy cast brass or bronze and in excellent shape, and tiller bracket and dropping the rudder as far as it would go until I remembered you mentioning something about digging.…

I removed as much corroded material as possible with a wire brush, screwdrivers, vacuum and sander,

then positioned the brass receiver ring where the remains of the aluminum showed enough shape to determine it's relative correct location and alignment.

Then I ran steel strapping around it. I screwed the strapping into the aluminum with stainless steel screws.  It's a galvanic nightmare in there, with steel, stainless steel, aluminum and brass or bronze! But I slathered the whole thing with lots of clear epoxy, then built it back up to shape with 2 layers of 6 oz woven glass cloth  covering and encircling the whole mess. It's well buried at least.

I kept the ring from being filled with epoxy by banging a wooden boat plug into it, then taping the back end and waxing the outside. Then when I got into lighter fairing, I cut the wood/wax out and drilled out the wood, leaving only the brass ring encased in expoxy and glass.                 

Since I plan to basically dry-sail the boat in fresh water for the next few years I am not concerned about the metals in there, especially since I don't think much if any water will get in. If I were leaving her in salt water all season, I'd be more concerned.












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