Jerry, Howard, Doug Gordon, & Chad: Thanks for the insight. I just checked Spirit's rudder. The trailing edge is cleanly squared off and about 1/4 inch wide for most of its length. The rudder is about six months old and in very good (but not perfect) condition. A careful sanding that brings the edge down to 1/8" (per Jerry's recommendation) and a few coats of varnish sound like good line items for the Winter Project List.
As reference for anyone else looking into this phenomena : Spirit was constructed in 2008 and her bottom has not been sanded, nor painted with anti-fouling. She has the standard rudder with the "turned down" rudder rod that Jerry described, and the rod appears to be chrome plated bronze. Jim M17 "Spirit" On Sep 27, 2008, at 1:19 PM, Howard Audsley wrote: > To clarify, that should be a sharp trailing edge, just as Jerry points > out, the edges are not rounded. The quote was from the book. I took > that to mean the side of the rudder near the trailing edge, not the > edge itself. The bottom paint thing stands. > > Howard > > > On Sep 27, 2008, at 9:47 AM, Howard Audsley wrote: > >> First I'd heard of this was in "Royce's SAILING ILLUSTRATED, >> Volume 1", >> bottom of page 134. >> >> "The trailing edge of the wide rudder at force 3 vibrated >> considerably, >> which eased when it was rounded. We had a similar vibration which >> disappeared after the edges were sanded. When new bottom paint is >> added, our rudder will vibrate for approximately a month, then stop". >> >> I have noticed the same thing with new bottom paint. If you think >> about >> it, the vibration is likely caused by a harmonic of some subtle cause >> of unbalanced lift on one side, which breaks down at some point, >> allowing the flow to force the rudder back to it's trailing aspect, >> lift is generated again, etc. >> >> Inspect your blade and/or run your hand over the trailing edges to >> see >> if you can see or feel any subtle bumps in the varnish or edge. If >> you >> find one, sand it smooth. Look at it under low light conditions, >> shining a flashlight down the edge. Shadows will appear if it's not >> perfectly smooth. >> >> They do not all do it. >> >> Howard >> >> >> On Sep 27, 2008, at 2:20 AM, James Poulakis wrote: >> >>> Sailing even with a moderate breeze makes Spirit's rudder hum loud >>> enough to drown out the Pillar Point fog horn. The rudder is new >>> and >>> doesn't seem to be warped. Is there a trick to stop this or is it >>> just a Monty thing? >>> >>> Jim Poulakis >>> "Spirit" (M17) >>> >>> _______________________________________________ >>> http://mailman.xmission.com/cgi-bin/mailman/listinfo/ >>> montgomery_boats >>> >> >> >> _______________________________________________ >> http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats >> > > > _______________________________________________ > http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats _______________________________________________ http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats
