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Old 31-08-2019, 04:32   #1
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Cruising CAT Rudder design

Hi I have a Summer Twins 25
and I want to refurbish the rudders this winter, but I wonder if the rudder design is correct for the latest thinking.
So at present the rudder has a carrier that acts as a foot, it is also completely made in stainless and it is tapered to a point.
So, also the boat seams to eat Tiller Pilots not sure if that the Raymarine or the boat at fault.

1) what is the best shape for a rudder back edge?
2) what dimensions so I actually need as I have 2 rudders itís not like one will ever be out of the water.
3) in some ways the buoyancy of the rudder must be useful.

What are your thoughts?

Thanks in advance
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Old 31-08-2019, 06:43   #2
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Re: Cruising CAT Rudder design

"1" is easy. Sharp. If not sharp, squared off cleanly and no more than 3/16" wide. But sharp is better.


Other factors.


Foil shape. NACA 0012 is the traditional choice. Google it.


Balance. Is the tiller stretching you arm? Could be rudder balance. Could be the main is over trimmed or stretched out.
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Old 01-09-2019, 15:01   #3
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Re: Cruising CAT Rudder design

Thinwater is on the money but some pics would be useful to give real advice
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Old 01-09-2019, 17:04   #4
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Re: Cruising CAT Rudder design

Does it look like this??

Pat knew what he was doing, so maybe speak with other owners and confirm that they do the job, then just clean up what you've got as indicated above.

I'm not sure that changing the rudders will transform the boat.
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Old 02-09-2019, 16:07   #5
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Re: Cruising CAT Rudder design

The Acumen of the rudders can play part, like toe in on vehicle steering.
The cross member joining the tillers together can adjust this, as it could been set wrong at birth.
Take in consideration what Thinwater posted first, sail balance and trim.
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