Speaking from Experience
My wife and I lost our rudder between St. Lucia and Martinique. Passage was about 15 miles open to the Atlantic. We had left Rodney Bay about 9:00 in the am heading north with winds from the northeast at 20-25 kts. Seas were 10-12 feet. We were on a close reach with two reefs. (Boat is a Metalmast 36, fin keel and spade rudder). The seas generally build up around the headland going north due to the current but settle down after 3-5 miles. About 3 miles out, the boat rounded up and the helm lost all feel. I looked over the stern and the rudder was totally gone! The first thing my wife asked "Are we going to sink?" The short answer was no. The rudder had fractured through the 4 inch SS rudder post at the waterline. The rudder post seal was intact. I tried lashing the spinnaker pole with a piece of plywood secured to the end onto the stern. You can't believe how much pressure there is. Because of the height of the topsides, you have to put the pole at a high angle to get any bite and you end up with no leverage. I had started the engine and further shortened sail but trying to keep the boat going on a beam reach or better was too hard without the stabilizing effect of the rudder. I then left the pole lashed in place and put a canvas carry-all bag secured to two lines over the stern. I led the lines to the primary winches and was able to drag the heading of the boat to starboard by adjusting the lines. The boat was crabbing but was making headway. We operated this way for seven hours to complete the remaining 12-13 miles to St. Anne in Martinique where we anchored off the beach. I don't think we could have done this without the engine to keep us moving. Why didn't we go back to St. Lucia? We were too far west and I did not think we could get back. We may have ended up in Belize! Also, St. Anne is the center of yachting in the area and has much better facilities to do extensive repairs than St. Lucia.We eventually found a local craftsman to fabricate a new rudder using the remains of the old rudder post. The old one had failed because of water getting inside and rusting the weld joint between the post and the "fingers" inside. The fingers were made from mild steel! We replaced the fingers with 316L stainless, built a mold box, filled with foam, shaped, covered in woven roving, mat and cloth, gelcoat, bottom paint and reinstalled. It took 4 weeks and cost about $3000 usd.After this experience, I made an emergency rudder that mounts to the transom with pintles and gudgeons. It breaks into two pieces and stores under the vee berth. I tried it out and it works but with the rudder in place you can't really test it. If you decide to make an emergency rudder, make it twice as strong as you think and you might be ok.Get out there and check your rudders for water intrusion. Any rust streaks or movement of the blade relative to the post are indication you have an internal problem.Good luck out there!