Viva, our 1975 Tartan 44 test boat, has, like most fiberglass boats, a hollow fiberglass rudder and skeg. The rudderstock is solid stainless steel, to which are welded horizontally oriented steel webs or plates. The rudder is molded in halves, with foam filling the spaces around the rudderstock and webs. Its the conventional method of building a rudder, but it has serious shortcomings. To wit, it fills with water, and when that water is salt, it tends to cause corrosion of the welds. Worse, according to Bill Seifert, who worked at Tartan during the 1970s, Vivas webs are probably mild steel and rust easily.
Keeping water out of the hollow rudder is difficult because stainless steel and fiberglass have different coefficients of expansion, causing the joint around the rudderstock to open up, however microscopically, and admit water. On some boats it may be possible to apply a bit of flexible caulk around the rudderstock where it enters the rudder, but on Viva, the clearance is only about 1/8″, so you can’t effectively work on the area.
The telltale sign of trouble is rust-colored water weeping from the joint. About the only way to stay the advance of trouble is to drill drain holes in the rudder during fall lay-up. The idea is to let the water drain over the off-season, then fill the hole with epoxy and microballoons before launch. (Alternatively, Bill Crane, a local boatperson of many skills, suggests tapping the hole to accept a brass plumbers plug; insert the plug with caulk; throw away in the fall and replace with a new one each spring.)
Depending on the condition of the foam, however, a hole in the bottom of the rudder may not drain water that has entered at the top. Youve got to find the sweet spot. Water most likely will migrate down the rudderstock and travel along the webs. So you may have to drill holes where you think the webs are located to drain off pockets of water there.
Last fall, we noted rust-colored water weeping not only from Vivas rudderstock/rudder joint, but from a pinhole on the trailing edge of the rudder, and from the leading edge of the full skeg. I drilled drain holes in both skeg and rudder. They weeped off and on all winter and early spring.
Last May, before launch, I sanded around the holes, washed with acetone, and filled them with epoxy and microballoons. All sealed except the lowest hole in the skeg. Where it had been dry the day of the repair, the next morning I was surprised to see water again weeping from the hole and the epoxy uncured.
I stuck a rag soaked with alcohol into the hole, then tried Pettit Polypoxy, an excellent product Ive successfully used underwater before. It didnt set either, which made me think there was more than just water weeping out of the hole (perhaps caused by a chemical reaction with the foam?).
Finally, it was noted that the hole was wet only during the heat of the day, dry in the cool of the evening. Indeed, during the day, pressure inside the skeg actually pushed the epoxy out. When I tried the repair at night, it sucked the epoxy in.
My God, it lives!
Two evening applications of Pettit epoxy sealed the hole. Unfortunately, the skeg sprung a new pinhole leak higher up the leading edge. In desperation, I consulted Bill Seifert, who said, Forget it. When we built the skeg we knew water would probably enter through the gudgeon bolts. But water wont enter the boat. Some day, drill a 2″ hole from inside the boat into the top of the skeg so water can run freely out the bottom.
Meantime, Im more worried about the rudder. Next year Ill drill holes to inspect the rudderstock welds. If they look nasty, Ill remove the rudder, split it in half and have new stainless steel webs welded to the rudderstock.
I keep thinking Ive done the last major restoration job, but now I know better.