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Old 11-20-2012, 09:31 AM   #21
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Greetings,
I think Mr.rwidman has hit the nail on the head. The manufacturer installed running gear that met the needs of the vessel. Sure, higher performance rudders probably CAN be designed but I don't think anybody here has a high enough performance boat to really gain a major advantage with a rudder re-fit.
A picture of a 1982 Penn Yan (now defunct company) boat with factory rudder...

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Old 11-20-2012, 12:10 PM   #22
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Penn Yan: This is what I meant in my original post "split on shaftline" each 1/2 aligns with the propeller stream decreasing resistance. The contra rudder is offset the opposite way straightening the stream and reclaiming lost energy. I never had the equipment to measure 3-6% gains available.
Experimenters may be interested in this:
http://legacy.sname.org/sections/gre...ibution%29.pdf
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Old 11-20-2012, 12:15 PM   #23
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I agree but how do you determine the angles to use? Anything is better than nothing at all? And can you factor in prop walk?
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Old 11-20-2012, 02:24 PM   #24
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Quote:
Originally Posted by FF View Post
"Rudders move the stern not the bow,"

The bow gets a differential pressure on either side , which causes the boat to turn.
No, the water pressure, from the prop thrust and the boat's movement through the water, applies a sideways force to the rudder. That force is transmitted to the boat at the stern. This moves the stern sideways thus aiming the boat in a new direction. If your theory was correct you couldn't pivot your boat with the rudder and thrust if it was standing still. But every boat on the planet can do this.

The resulting swing of the stern and pivoting of the boat when it's going forward may cause the water pressure on one side of the bow to increase a bit which may add something to the turning moment, but it's not why the boat turns. It turns because you "re-aim" the stern.
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Old 11-20-2012, 03:19 PM   #25
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I agree but how do you determine the angles to use? Anything is better than nothing at all? And can you factor in prop walk?
I held a dowel w/ 2 pcs. paper taped to it in front of a fan to get my angle which stayed constant with fan speed (as I recall) and which looks now to be about 2/3 of what Penn Yan used. I don't think prop walk is greatly affected. I never saw any difference in any of my various trials.
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Old 11-20-2012, 04:08 PM   #26
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This maneuvering stuff is not rocket science peeps. We aren't trying to stay on strings of fish gear across a 40kt wind. We are simply putting small boats into places a couple of times per year. a little instruction and practice at the marina would serve 99% of the supposed handling issues. Why re-invent the wheel. Watch a commercial fisherman dock or un-dock and observe how they use gear and throttle. Most of us will not be as proficient, but nor do we need to be.
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Old 11-20-2012, 06:05 PM   #27
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Maybe practice with existing equipment would also be an option?......
Now where's the fun in that?

Probably not applicable to stinkpots like ours, but I added a 4" x 36" trim tab to the outboard hung rudder on a Cape George 36' cutter we sailed. The trim tab took ounces to turn, which in turn powered the much larger rudder. I could use the smallest, cheapest autopilot to turn the trim tab and hooked up a very simple and light weight wind vane that steered the boat to Hawaii and back with the tiller removed to get it out of the way. I was pretty surprised how well it worked....
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Old 11-20-2012, 08:28 PM   #28
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This maneuvering stuff is not rocket science peeps. We aren't trying to stay on strings of fish gear across a 40kt wind. We are simply putting small boats into places a couple of times per year. a little instruction and practice at the marina would serve 99% of the supposed handling issues. Why re-invent the wheel. Watch a commercial fisherman dock or un-dock and observe how they use gear and throttle. Most of us will not be as proficient, but nor do we need to be.
Who said anything about maneuvering?
Increased powering efficiency and less hunting on autopilot were the goals which prompted my experiments. These goals are actually somewhat at odds with improved low speed maneuvering.
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Old 11-20-2012, 10:36 PM   #29
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I understand completely. It's the obvious thing to do. All boat rudders should be like this. But it's just too small of a detail to be bothered w when you're trying to turn a profit. I like the Sumnercraft keel too but I've never seen another boat w that keel. They saw they had the chance to deflect the water flow into the advancing prop blades to increase thrust and they did it. Perhaps the Sumnercraft designer had once been a jet engine mechanic.

But I too like those little fine tuning details. Makes a boat all that it can be.
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Old 11-21-2012, 06:05 AM   #30
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Maybe if you had "hunting" issues with both the Bruno and the Willard, the auto pilot might be the place to look. Both hulls had many built so others would be dealing with the same problem.
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Old 11-23-2012, 03:32 AM   #31
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[QUOTE=Brooksie;113349]Eric, Thanks for response and suggestion. I will measure... I always assumed 35 degrees was a universally agreed upon figure. Funny, because "question everything" is my moto.

Brooksie, If your W36 is the same as mine was it has a Wagner T-2 hydraulic tiller that turns 45 degrees. Bill
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Old 11-23-2012, 02:15 PM   #32
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The stock rudder that came with my 35 Bruno & Stillman was disappointing to say the least. It was too small and not enough balance. Made a large SS rectangle rudder with a balance that is 28% of of the rest and significantly bigger. The swing was increased to 45 degrees. End result is that it steers very nicely from 6 to 18 knots. Close quarters manuvering at 6 knots is a dream and you can actually steer the boat going backwards as a result of the larger size.

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Old 12-07-2012, 10:40 AM   #33
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Quote:
Originally Posted by Sailor of Fortune View Post
Maybe if you had "hunting" issues with both the Bruno and the Willard, the auto pilot might be the place to look. Both hulls had many built so others would be dealing with the same problem.
Right: No issues with the Willard. But the Bruno did have a poor rudder as delivered, thus the hunting and the quest for a rudder with less deadband.
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Old 12-07-2012, 10:48 AM   #34
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The stock rudder that came with my 35 Bruno & Stillman was disappointing to say the least. It was too small and not enough balance. Made a large SS rectangle rudder with a balance that is 28% of of the rest and significantly bigger. The swing was increased to 45 degrees. End result is that it steers very nicely from 6 to 18 knots. Close quarters manuvering at 6 knots is a dream and you can actually steer the boat going backwards as a result of the larger size.Ted
Much the same result after replacing my rudder but by using an airfoil section on it, I introduced the constant "hunting" on autopilot so I moved on to try other shapes.
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Old 12-07-2012, 10:58 AM   #35
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Brooksie, If your W36 is the same as mine was it has a Wagner T-2 hydraulic tiller that turns 45 degrees. Bill[/QUOTE]

Mine had chain and draglink steering when I got it but I added hydraulic later. Never had any low speed steering issues so never tried 45 degrees and the rudder stops were all in place at 35. Mine is a 1971 thus the chain & draglink steering.
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Old 12-07-2012, 08:06 PM   #36
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Brooksie, If your W36 is the same as mine was it has a Wagner T-2 hydraulic tiller that turns 45 degrees. Bill
Sorry, I misread & misspoke. My Willard does have Wagner T-3 steering and is a '62. I never measured the steering angle. Isn't it built into the T-3 at 35 & 35?
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Old 01-23-2013, 01:40 PM   #37
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When I designed the hydraulic steering system for my 42 ft. steel tug I learned that the steering effort at 45 degrees is abiut double what it is at 37 degrees. Had to increase ram size etc.

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Old 01-23-2013, 01:47 PM   #38
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Greetings,
Mr. tugnut. Welcome aboard.
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