Rob,
Current problems weren't around when we tested the
new rudders.
The rudders themselves are straightforward 40cm
wide and 1.5m deep, NACA section.
The rudder shaft is 70mm square and is not faired
above the blade to be able to pull it up
all the way to the tube with the rudder bearings.
That does produce some spray but the faired
part is piercing the water surface at
rest.
The rudders draw .7m minimum, pulled up all the
way.
This shallow draft ability is important to the
owner. They sail a non tidal water with well charted shallows.
We tried sailing BD with one 'old' rudder as an
extra. We pulled the new one out and used the old one instead,
steered with a tiller. That worked well. We steered with the aft rudder.
I'm not sure if you can compare small boats like
El. with bigger boats one - one.
Lengthwise trim might have something to do with
this too.
Rudolf
G'day,Honest answer is, no idea. I have not seen any pictures or reasonable descriptions of the rudders, the keel or the steering set up. The pictures of the boat I have seen have shown the jib sheeted to the mast and the rudder shafts kicking up a shower of spray and destroying the flow over the rudders. There are 5 people on the committee running BD, and they have 5 different ways of shunting and 5 opinions of what is wrong and how it should be fixed. I have made numerous suggestions to improve the steering, but have had no feedback on whether they were tried, or worked. It is heartbreaking for me as BD is the epitome of how a hp cruiser should be.
I do know the beam mounted rudders work well on El, even with comparatively more weight in the ww hul than BD. I am putting a similar set up on my boat and the second one we are building. It is also going on the two 20m/66'ters.
I also know the original rudders work on Rare Bird and consider this a far better option than keels, rudders on the ends etc. The problem is not shallow draft steering. This can be done with the original set up. The problem is if the boat is sailed at high speed in shallow water, when the rudders become unbalanced and steering loads get high. I think this is unseamanlike so the unbalance on the raised rudders will force the boat to slow down, which is a good thing.
I am happy to discuss this further, but until I have all the information, and the current problems are corrected, I will not be much help.
rob
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