Arne Kverneland wrote:

Stavanger, Saturday.

Just a thought: On big boats with unbalanced outboard rudders, I would consider fitting two trimtabs, either above each other, down along the rudder's trailing edge, or aft of each other with one attached to the rudders trailing edge and the other at some distance aft of the rudder.

The idea is to connect one trimtab (the lower or inner one) to a little " trimming tiller" with a fine-toothed pinrail on it. One could then easily trim out any constant  (main) tiller forces (weather or lee helm) . Then the other trimtab could be connected to a windvane gear.

My hunch is that the windvane now would have an easier job with keeping the boat on course. On Ashiki, the rudder is maybe of the fully balanced type (have forgotten) so will then not need the extra trimtab.

Cheers, Arne

Our rudder isnt balanced enough, Jay Benford's design looks to have only 5% balance and Belcher says ~17% is needed. Maybe simpler solution is I scarf on a another 3cm or so to the width of the tab, give it more area.

Stavanger, Saturday.

Just a thought: On big boats with unbalanced outboard rudders, I would consider fitting two trimtabs, either above each other, down along the rudder's trailing edge, or aft of each other with one attached to the rudders trailing edge and the other at some distance aft of the rudder.

The idea is to connect one trimtab (the lower or inner one) to a little " trimming tiller" with a fine-toothed pinrail on it. One could then easily trim out any constant  (main) tiller forces (weather or lee helm) . Then the other trimtab could be connected to a windvane gear.

My hunch is that the windvane now would have an easier job with keeping the boat on course. On Ashiki, the rudder is maybe of the fully balanced type (have forgotten) so will then not need the extra trimtab.

Cheers, Arne

Hi Gary and Antoine

In case it helps:

A very good self-steering for transom mounted rudders which is Servo Pendulum, but does not require operating cables to the tiller. It's known as the RHM (Rudder Head Mounted) and designed by Jan Alkema. He wrote about it in the Magazine called Catalyst in Jan 2006 issue No 23. This publication is by the AYRS (Amateur Yacht Research Society).

www.ayrs.org/catalyst.htm 

www.windautopilot.de/docs/alkema/RHM-USD.pdf

He also has devised an Upside Down Vane system (USD VANE) which can respond more quickly in some conditions.

As far as your Belcher gear is concerned I have his design book and can refer to dimensions etc if you need help to repair and get it running properly.

No HK parrles on this boat. She handles like a dream, has a few quirks depending on the seastate, panels reefed & phase of the moon. We had trouble tacking in 25-28kt and choppy seas, but this morning in Cockburn Sound she made every tack. But this is all about learning how to handle her and I think we may have been undercanvassed that day going to windward. She goes 6.2 to 6.5kts on broad reach, the sound changes about then..  but reefing down to a respectable 4kts is extremely comfortable, can go below and do stuff then.

Thanks Antoine.