Here are a few comments about the Cal 39 rudder which are based on my own experience of owning a 1979 MK2 model for about 20 years, as well as info which is obtained from copies of Bill Lapworths original drawings of the 39 MK2/3 model.
The upper section of the rudder post is made of stainless tubing 3.5 in diameter with about schedule 40 wall thickness, or about 1/4 wall thickness. This tube extends from the top of the post down into the rudder about a foot where it is welded to a 3 tube which is angled aft maybe 10* and this tube continues further down into the rudder blade. The drawings appear to show this 3 tube inserted into the larger tube to absorb bending loads, but several rudders which I have seen have butt welds instead, and this has caused problems in some cases.
The rudder post is supported in the hull by a fiberglass
tube fairly heavily glassed to the hull bottom, and extending up maybe 15. On the top of this fiberglass
tube is glassed a Yacht Specialities bronze
seal fitting which acts to support the weight of the rudder. Above the seal fitting is the quadrant which is clamped and thru bolted to the rudder stock. The bronze
quadrant rides on the bronze seal fitting providing a low friction surface. The rudder post continues up to the underside of the deck
and is positioned by a bearing bolted to the underside of the deck
. On my boat this upper bearing consists of two pieces of 1 thick phenolic drilled a suitable size and bolted to the underside of the deck.
The fiberglass tube which supports the rudder is equipped with two grease zerk fittings to lubricate the rudder post, and in the models that I have seen there are no bearings/ bushings in the tube....the rudder rides directly on the fiberglass.
These rudders were made for Cal by Foss Foam in S. Cal, and I believe later by Foss Foam in FL. Foss Foam is still in business in Florida
, and I believe they are affiliated with Finco in S.Cal. Both companies can build you a replacement rudder if that is required, or they could supply an updated rudder design similar to one they supply for Cal 40s.
Hope this info helps. Feel free to respond if you have any questions.