Subject: [harryproa] one rudder proa, first sail
From: "Rob Denney" <>
Date: 2/23/2006, 9:47 AM
To: <>, <>

Sorry I have been off air for the last couple of weeks.  Got a bit obsessed with the single rudder proa.  Anyone with any unanswered questions or emails, please ask/send them again.
Following on from the successful "una from a schooner" rig and success using the aft rudder only, I have tried to build a single rudder that was moved from end to end.  To minimise the work involved, I used the beams as supports.  One of our clients was keen on drum rudders so I thought I would give these a go.  Mk 1 was a 300mm dia 300 deep drum.  Heavy and draggy so it was chainsawed and I made a T section with the ball races in the top.  Building it was possible without a lathe, but would have been much easier with one. 
First plan was to have it running on a couple of strings between the beams.  Looked ok, but did not work.  Next was a couple of 20x 50 strips of glassed timber between the brackets.  This works well, except the rudder unexpectedly floated, a nuisance as I had the runners on the top of the strips instead of under them.
Despite the rudder being 33% of the loa from the end (was 25% with the fixed rudders), it steered ok.  Interestingly, it luffed better than it bore away, whereas previously any difference has not been noticable.  Bearing away, particularly at slow speeds was novel.  The whole boat would climb to windward while the bows slowly turned downwind.  Had to stop and reverse the first time I tried to get around a moored boat.  The faster the boat sailed, the less obvious this effect was.  Helm balance was excellent, could leave it alone from broad to tight reach (didn't sail ddw) and the boat tracked straight.
A first for me was that nothing on the prototype broke!  Sailing tentatively reached 13.1 knots on the gps (not much breeze as you can see in the pictures), and everything felt really good. 
The drum and tracks weigh about the same as the old daggercase boxes, but could be lighter.  The difference between the 2 rudder schooner and the single rudder una is about 30 kgs and less drag, which is a big deal off a 130 kg boat.  Must weigh it next time it is off the trailer. 
The system works, but needs the following changes.  A solid stop instead of rope to keep the rudder vertical, lower the tiller, put a kink in the tiller extension to get it under the rails, and runners under the rails to stop the rudder floating up when shunting.  The drum works really well (thanks Col) and definitely has a place in future proas.  The end to ending is good for a little boat, maybe for a race boat, probably not worth the hassles on the bigger cruising ones.   
Should have the fixes done and sailing again on Sunday.
There are some pictures in the photos section of the harryproa chat group.

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