Restoring a Talent
Part 3 – Rudder housing, Skeg and Keelbolts With Talent’s rudder rebuilt, I turned my attention to her remaining underwater metal components, the rudder housing, skeg and keelbolts.
As designed Talent’s rudder housing is a 316 stainless steel tube holding bronze bearings. The lower 120mm of the tube is buried in the deadwood, the top is held by the cockpit floor, and a welded flange is screwed down to the inner keelson and bedded on epoxy.
Sealing stainless to timber with epoxy is often problematic. Under stress the epoxy cracks, leading to a difficultto-fix leak which, because the stainless is buried in damp timber, creates a perfect environment for crevice corrosion. Like her rudder shaft Talent’s rudder housing had corroded and required replacement.
A far superior replacement is an epoxy GRP tube with composite bearings. The GRP tube glues well to timber and can’t corrode. In conjunction with the new rudder shaft Henley’s Propellers supplied a GRP tube fitted with plain Thordon bearings. The GRP tube doesn’t have a flange; it’s created in-situ after installation.
After cutting the old stainless tube in half and applying heat, I was able to drive each section out in turn and add them to a growing pile of scrap metal.
To give a good bond to the GRP flange, with a friend’s help, we first glued and screwed fresh kauri to the inner keelson, then using a jig-mounted hole saw increased the hole through the deadwood and cockpit floor from 62mm to 75mm to suit the larger GRP tube.
The GRP tube was then installed and temporarily held with small timber wedges, enabling the rudder to be installed to check the alignment. It’s critical to check this both sideways and fore and aft so
silicon bronze, nickel aluminum bronze and stainless steel 2205.
After much thought I chose stainless 2205 for the keelbolts, with nickel aluminum bronze (AB2) for nuts and washers, a proven combination that will easily undo even after many year’s immersion.
To the same diameter, stainless steel 2205 has well over 2.5 times the tensile strength of HD copper. While 2205 has excellent resistance against crevice corrosion, careful sealing is still required. Stainless nuts weren’t used because in larger sizes stainless nuts on stainless bolts have a propensity to gall (fuse) together. There are ways to mitigate this, but if they don’t work the nut has to be cut off – good luck with that on a keelbolt lower nut.
Naturally I considered AB2 bolts, but besides their significantly higher material cost, AB2 bolts would have had to been machined from cast billets. With over four metres of bolts needed that meant considerable lathe time, whereas stainless 2205, one-inch diameter centreless ground shafting was available off the shelf. The AB2 nuts and washers were cast from timber patterns we supplied.
Incidentally, the keelbolts and nuts were threaded to one-inch UNF specifications. The UNF thread is shallower and leaves a stronger bolt than UNC, plus it’s easier to tighten.
I took the opportunity to address a minor design weakness. Like many Townson yachts, Talent’s front keelbolt is located 600mm aft of the front of her lead keel, a major reason for the gap between keel and deadwood at the front.
Surveyor Ray Beale and Bill Townson both advised adding an additional front keelbolt, which we did by angling a 5/8” 2205 bolt up from the front of the lead keel and into the starboard engine bed, which is on the yacht’s centerline and is bolted to the mast step.
ASSEMBLY
To suit my chosen bedding compound a perfect match was required between deadwood and keel. With Talent sitting 150mm above her keel and the well-greased original keelbolts loosely installed, a sheet of heavy duty plastic was laid over the lead and plastered with a mixture of WEST epoxy and high-density 404 powder.
After pre-priming the deadwood with epoxy resin, Talent was lowered, the keelbolts tightened and the keel alignment checked by switching the previously made pattern from side-to-side. It was easy to tilt Talent using the threaded cradle supports until her keel was perfectly square to the hull.
After a two-day cure, Talent was jacked up, the keelbolts, plastic and surplus epoxy removed leaving a perfect mirror match between deadwood and keel.
Professional opinions vary as to the best bedding between deadwood and keel – epoxy and polyurethane sealant being the two most popular choices. While a good case can be made for either, both have a downside and complicate future keel removal.
Not needing epoxy’s strength or polyurethane’s gap-filling ability, to simplify future keel removal I used the traditional, well-proven red lead paste to bed Talent’s keel.
For additional waterproofing we installed caulking cotton grommets around each keelbolt top and bottom, then injected warmed Lanocote into each keelbolt hole via a grease gun during final assembly. Besides its waterproofing abilities, Lanocote is a proven corrosion protective.
With Talent and her keel reunited, it was time to tackle her interior.