Subject: Re: [harryproa] Beam mounts and tillers
From: "Rudolf vd Brug" <rpvdb@freeler.nl>
Date: 3/10/2011, 5:34 AM
To:
Reply-to:
harryproa@yahoogroups.com.au

 

Rob,
With the old rudders there was noticeable bow down trim when sailing.
Front rudder up or down didn't seem to make much difference.
Upwind or downwind wasn't different either. We never experienced any lee helm no matter what combination
of sail/rudder up or down. I think we covered most combinations.
Steering was ok on all courses, but over 10 knots rudders couldn't handle the load.
 
The new rudders downwind have about the same angle to fight the luffing as upwind.(10 deg at least)
Going upwind they stall easily if you it point a bit too high.
The front rudder needs to be in the water to help keeping the boat from luffing.
I think it isn't as much lack of lat. area as rudder placement causing the problem. See old rudders above.
Adding the extra (lee)board/keel made a huge difference when pulling the sheet lying beam to the wind.
Without it getting going was a matter of going almost dead downwind before we were able to counteract the luffing.
With the leeboard we just pulled the sheet and sailed of. It was actually easier then with the old rudders which also needed
a course a bit downwind to get going.
 
Ask as many questions as you like, I think rudders are the most important proa-issue at the moment.
 
Rudolf 
 
 
----- Original Message -----
From: Rob Denney
To: harryproa@yahoogroups.com.au
Sent: Thursday, March 10, 2011 12:49 AM
Subject: Re: [harryproa] Beam mounts and tillers

 

Rudolph,
Did it sail bow down with the old rudders? Was there any noticable
change in trim with the front rudder raised? Did it make any
difference upwind or down? Do the new rudders steer ok downwind?
Sorry about all the questions, but the more I know, the more able I am
to sort it out.

Ben,
There is no question it is sailing bow down and no doubt this affects
the steering. The question is why is it bow down? I suspect it is
because the rudders are turned at a big angle. The only other change
is the keel. If it is the rudder angle, the next question is why are
they at such an angle? Obviously a clr/coe balance problem. But if
you lift the front one (or align it with the flow), the coe is ahead
of the clr of the aft rudder which should provide lee helm. The keel
will influence this, not sure how much. If you reduce the sail area
aft of the coe (reef the main, the lee helm should be even more
pronounced. Apparently (Rudolph?) it wasn't.

I have found that once any of the boats are moving, the helm is pretty
easy (see the various videos). BD is the exception to this. The
time when it can be tricky to steer is coming out of a shunt. That is
when big rudders and no fixed foils work best, in my experience.

All very perplexing.

rob

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