Could extend them, but easier to use the
beams. Also fun to push past the limits to see what happens. Not yet
sure what will happen on the bigger boats with one rudder. A
system like you suggest would work and be pretty easy to build. I don't
like the idea of extra headsails as there is nowhere easy to sheet them and they
involve going on the foredeck. Could be done, though. For light air,
I like a telescoping mast, but won't know about this until I build
one.
No rush with the spreadsheet. I agree about
the una rig. Should get some sailing photos on Sunday or
Monday.
regards,
rob
----- Original Message -----
Sent: Friday, February 24, 2006 4:42
AM
Subject: Re: [harryproa] one rudder proa,
first sail
Just some idle thoughts. Could you extend the rails past
the beams to get the
rudders further aft,maybe some support off the hull?
What about a simple
system utilizing bungee cord for the two rudder set up?
My idea would be
uncleat a line and the rudder pops up, pull the same line
and cleat it and the
rudder is locked down. Sounds harder than the
reality.
So now, what about harry with a una rig (with a wishbone?) and
rudders that
raise and lower easily, then staysail/assymmetic for light
airs downwind in
the light stuff?
I haven't got around to cleaning up
the materials/price sheet yet, got busy,
will try to do it this
weekend.
BTW I think the una rig looks slick.
------
Original Message ------
Received: Thu, 23 Feb 2006 07:48:34 AM MST
From:
"Rob Denney"
To:
<harryproa@yahoogroups.com.au>,
<proa_file@yahoogroups.com>
Subject: [harryproa] one rudder proa,
first sail
g'day,
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.
regards,
rob
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