Your hypothesis that the one rudder could have been free-spinning prior is certainly valid, but one thing about Doane's description is that they were forereaching under main alone when they needed to have full rudder. That boat has its mast more aft than most catamarans. This is even described in the marketing materials. Coupled with the windage aft due to the house, hardtop structure and freeboard, this could cause considerable weather-helm without a bad rudder.

I still don't see that the Alpha 42 rudder is any different in size than every other catamaran out there. If anything, it is a well-shaped foil and would be more efficient than the normal trapezoids found on many catamarans. If you consider the rudder size against the draft of the boat, which is 3.5', and against the saildrive which extends down 10-12", that rudder is close to 24" long. And shaped. This is both longer and better shaped than many catamaran rudders - but let's just call it normal, because it is certainly not shorter than any catamaran rudder I have seen.

You can judge for yourself from the installation pictures - unless those are really short men. Also, while the perspective of the picture in the air is not good, those are 17" diameter props fitted.

I don't understand your point about one hull loading up more than the other. Both rudders are at work whether they are loaded more or not.

Speed has nothing to do with this - these are standard sized catamaran rudders and work at any speed the boat is traveling. I am not understanding why non-catamaran owners keep insisting they are powerboat sized rudders and tossing aside the facts presented to them by people who actually own catamarans. Rudder size has nothing to do with this - it is about the scantlings and building method, not size.

Here is an anecdotal story about catamaran rudders. We were on a short one day passage last summer on our boat, which has rudders similar in size to the Alpha's. We were running downwind in 35kt steady with regular gusts to 40kt and 8-10' seas. The autopilot handled this wonderfully, making small corrections as we regularly transitioned from surfing to bottoming out and back. The boat was in complete control and the autopilot was happy and barely sipping juice running the boat.

After 24hrs, as we closed in on the mouth of the bay we were sailing to, I switched off the autopilot and had no steering at all! A steering cable had jumped the quadrant and the only steering surface we had most of that trip was the one rudder with the AP drive attached to it. The other rudder was free to swing from stop to stop at will (our steering system does not use a cross bar) - which explained the strange thumping noise we would occasionally hear from that hull on that trip. So I continued into the bay, circled around to find a good anchoring spot and anchored - all using the autopilot and one rudder.

Another anecdote. A catamaran recently hauled out here because they lost one of their rudders. The post snapped at the lower bearing. They lost it in some bad weather around Puerto Rico, yet continued to cruise with their boat for a whole year through the Caribbean and into the Rio Dulce, where they finally replaced the rudder.

So a catamaran with just one working "powerboat sized" rudder is perfectly under control in most normal sailing conditions.

Mark