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Old 10-02-2014, 10:02 AM   #41
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Originally Posted by funangler View Post
The backside of the fish tail is pointing way more than 90
Ahhh...and therein lies the magic
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Old 10-02-2014, 10:40 AM   #42
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I had no idea that was possible. Very impressive and yes it would be nice if Willy did that.

However I don't think most fishtail rudders almost totally eliminate fwd movement. My rudder swings 45 degrees each way and w the big rudder we have plenty of rudder authority but w almost no drag penalty. I position my zincs above the propwash on the rudder ... not because I'm an efficiency nut but just out of principal. But I'm sure the extra drag of a fish tail rudder capable of the above performance would be noticeable. It's right in the propwash. The propwash (in concert w the rudder) effectively pushes the rudder backwards and the obvious happens as the rudder is attached to the boat. Somebody somewhere must have done a speed/efficiency loss study. The extra rudder drag can go on for 10 hours while the advantage would last only a few seconds.

But I'll weld on fishtails if the drag is low enough. But most owners may prefer bragging rights to real facts.

Seems to me the "fish tail" rudders frequently or most often have a wide rudder section in the vicinity of the rudder shaft. What role does that streamlined but fat part of the rudder play (if any) in the turning capabilities of the fish tail rudder?

There's been a lot of excitement on the Willard Boat Owners site 9in the past) about articulated rudders and that is what I'd consider a step up from the much simpler fish tail rudder. But if you can accomplish what funangler displayed in his video w the far simpler fish tail rudder why would anyone go to the extra trouble and expense to employ articulated rudders?

However if I wasn't about to launch I'd probably be cutting some flat bar.
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Old 10-02-2014, 10:40 AM   #43
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Old 10-02-2014, 10:44 AM   #44
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On a sidenote I can drive this single screw more aggressively then twin screw boats. I find it a little more predictable. Twinscrew can be tricky when you get aggressive with them. Twinscrew boats will let you do some amazing maneuvers that I cannot do in a single screw.
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Old 10-02-2014, 10:56 AM   #45
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Hobo with a 28" prop and SS rudder.
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Old 10-02-2014, 11:03 AM   #46
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Quote:
Originally Posted by manyboats View Post
"But I'm sure the extra drag of a fish tail rudder capable of the above performance would be noticeable."

"Seems to me the "fish tail" rudders frequently or most often have a wide rudder section in the vicinity of the rudder shaft. What role does that streamlined but fat part of the rudder play (if any) in the turning capabilities of the fish tail rudder?"
Eric,

If you will do a search for 'Schilling Rudder' or 'MacLear Thistle Rudder' you will find plenty of information on how and why these rudders work so well in low-speed vessels. They are popular on long-narrow canal barges and a variety of workboats and ships. My research on them leads me to believe that any increase in drag would only be noticeable above displacement speeds.

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Old 10-02-2014, 12:05 PM   #47
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I lost 0.1 to 0.2 knots of speed well worth the lost of speed. In big breaking waves I turn around really fast. My max speed is 8.5 knots.
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Old 10-02-2014, 12:44 PM   #48
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The bigger the rudder(s) the more wetted area. The more wetted area, the more drag. The more drag, the higher fuel burn. Comments?
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Old 10-02-2014, 12:51 PM   #49
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Large rudder is still cheaper than twins in the long run.
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Old 10-02-2014, 12:57 PM   #50
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Very impressive! Damn, now another project ......
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Old 10-02-2014, 01:58 PM   #51
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DANG,
And I thought my rudder was just fine. Next haulout. Funangler thanks for the demo ect. I would'a never believed ya w/o the video. I'll expect less w only 45 degree rudder swing and do my research.

ancora yes but the question is how much. Looks like not enough to shy away in this case. I don't think the average rudder here on TF would be capable of funangler's performance even if modified ... unless it was made MUCH larger.

Larry M,
Thanks for giving me a starting kit for my research.
I would'a thought the KK had more of a steep run of the bottom aft. Much straighter than I thought. SS rudder? How thick? My bronze rudder is 1/2". I plugged my prop hole. Will show later. Could'a just used a shapely zinc.
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Old 10-02-2014, 05:03 PM   #52
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the Coot's "barn door" makes tight turns even at idle speed.

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Old 10-02-2014, 05:07 PM   #53
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The bigger the rudder(s) the more wetted area. The more wetted area, the more drag. The more drag, the higher fuel burn. Comments?
With a top speed of 7+ knots, any difference is immeasurable.
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Old 10-02-2014, 08:20 PM   #54
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My fishtail rudder is small then my original rudder by 4 inch in length.
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Old 10-02-2014, 08:38 PM   #55
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I built the rudder and did not change the turning cylinder size the first year. I reduce my turning radius in half overall but I wanted more. My old cylinder was 5.5 inches of travel the new one jumped to 11 inch. Where I dock have to make a tight 180 turn to get to my spot on the wall and need the zero turn ability.
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Old 10-02-2014, 09:14 PM   #56
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A rudder to be thankful for

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Old 10-02-2014, 09:17 PM   #57
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Old 10-02-2014, 11:23 PM   #58
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While I enjoyed the video (and wished my boat had the same maneuverability), I suspect that most of that was due to the almost 90 degree rudder angle. In the view from aft you can't even see the propeller - it's entirely blanked by the rudder!
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