Originally Posted by Alisske
Mine was single behind a keel. Semidisplacement round chine hull
After the adjustment, it steered better both ways and more predictably.
When i measured the actual rudder swing and saw the “lopsideded ness” to it, everything made sense.
Again, i believe a rudder i er 35 degrees becomes a brake. (Hydrodynamically)
From what I know, that 35 degree figure is pretty typical for a flat plate rudder. And any rudder is going to have a good bit of drag at higher angles. Foil shapes, etc. can have different angles before they stall or develop any bad behavior though, and whether there's prop wash across the rudder or not is a factor too. Some rudders can go beyond 35* without stalling (just some extra drag but no bad behavior or loss of steering) while others (particularly on sailboats) may stall before 35*.
The other big question becomes what the actual angle of the rudder is to the water flow once you're in the turn. The rudder may be turned 30* relative to the boat, but with the boat turning, the actual angle to the water flow can be significantly less.
Full rudder on my boat definitely slows the boat down noticeably at lower speeds, so there's certainly a lot of drag there. But no bad behavior, it just turns.