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Old 07-17-2014, 06:51 PM   #1
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Need rudder design options to improve slow speed turning

We have a 1978 40' DeFever Hudson that has poor maneuverability at slow speed. Rudder is a horizontal rectangle. Have thought of adding wedges to the back of the rudder. Trying to spend less and get more Anyone have design suggestions?
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Old 07-17-2014, 06:55 PM   #2
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A vertical rectangle should work a lot better!
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Old 07-17-2014, 07:13 PM   #3
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I had to think that one through, too.

Are you getting full travel?

Do a search on here for "articulated rudder."
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Old 07-17-2014, 08:21 PM   #4
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Could it be that you just need to learn how to maneuver the boat better? Try a quick burst of power with the helm hard over to get a turn started. You need to have water moving over the rudder to turn the boat.
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Old 07-17-2014, 08:46 PM   #5
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Second that. A low speed boat with little wash will barely turn, even if you double the rudder. Give 'er a snort of power to kick the stern the way you want, then if too fast go to neut or even a bump in reverse. Single screw handling is a learned art, lots of techniques out there to help. Rare to end up truly "pickled" except in some wind and current conditions. Then you need to learn what to avoid.
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Old 07-17-2014, 09:18 PM   #6
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Quote:
Originally Posted by jan n will View Post
We have a 1978 40' DeFever Hudson that has poor maneuverability at slow speed. Rudder is a horizontal rectangle. Have thought of adding wedges to the back of the rudder. Trying to spend less and get more Anyone have design suggestions?
Design suggestions, well, there is always the 'Thistle Rudder' or 'Schilling Rudder'. Here is an account of a modification made by the owner of a Sundowner Tug that was apparently a huge success.

As previously stated though, you have to have water moving over the rudder. The smaller the rudder, the more you need. At idle or in neutral there is virtually no rudder authority. The Thistle or Schilling rudder is designed to increase the effect of prop wash on the rudder, but there must still be water moving over the rudder.

Then there are thrusters, but you said you were trying to spend less.
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Old 07-17-2014, 09:45 PM   #7
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Many trawlers have very small rudders and are dependent mostly on prop wash. The rudders are small no doubt to enhance higher speed performance ... high speed trawler speed of course.

If the rudder or rudders are large enough and speed is kept down much better turning performance will result by increasing rudder deflection. The standard rudder deflection of 35 degrees on faster craft is not very effective at slower speeds in the vicinity of hull speed. Most semi-displacement or semi-planing (exactly the same thing) boats are capable of speeds in excess of hull speed thus requiring smaller rudders and low deflection angles.

When I first had my 30' Willard it had slow steering (6 turns L to L) and lower deflection angles. I changed the steering to 3 turns L to L and re-located the attach point on the rudder horn so that there is now 90 degrees rudder deflection ... 45 to each side.
The improved rudder performance is remarkable and I have no need or desire to search for trick rudders w articulating trailing edges or V shape or wedges ect. Just don't need any more rudder action. My rudder is large and the boat is operated only below hull speed. Larger rudders and increased deflection would not be appropriate for craft that operate at speeds above hull speed. Slight changes may have positive results for boats that are capable of faster speeds but never or almost never go there. These boats of ours are private property and there are no laws for rudder design.

For the OP I would seek out others w the same boat and try to learn from them.
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Old 07-17-2014, 11:46 PM   #8
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Quote:
Originally Posted by rwidman View Post
Could it be that you just need to learn how to maneuver the boat better? Try a quick burst of power with the helm hard over to get a turn started. You need to have water moving over the rudder to turn the boat.
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Old 07-18-2014, 12:47 AM   #9
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Originally Posted by jan n will View Post
We have a 1978 40' DeFever Hudson that has poor maneuverability at slow speed. Rudder is a horizontal rectangle. Have thought of adding wedges to the back of the rudder. Trying to spend less and get more Anyone have design suggestions?
Hi Jan or Will, it says in your profile that the DeFever is new to you. As the others have pointed out technique is probably going to help you more than any modifications. The current rudder has served it well since 1978.

The best thing you can do short of hiring someone to teach you is the next time you leave the dock find a patch of calm, current free water and slip her into neutral, drift to a stop and practice. I tossed an old orange PFD into the water and practiced coming along side it and maneuvering around it for the better part of an hour. Picked up the life jacket and went for a drive to another area with a little bit of current and repeated above. Picked up the PFD and went to a place that had current and lumpy water and repeated again.

By the end of that day I returned to the marina and practiced coming along side an empty side tie for a half hour. Then went to my slip and pulled her in and out of the slip probably a dozen times.

That was a fairly long Tuesday on the water but I had the place pretty much to myself, probably saw 2 boats all day. By the time I came up to the boat the following weekend I had enough confidence to come alongside a fellow TF members boat and raft up. Al even commented how impressed he was at how easily I maneuvered into place.

There's no shortcuts to seamanship and as this is my first "real" boat with single inboard power it took a little getting used to. My seamanship skills are far from what I'd like them to be but learning close quarter maneuvering is best learned in open water away from docks and Lookie Lou's.

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Old 07-27-2014, 03:24 PM   #10
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Need rudder design options....

Thank you all for your responses. Truly I think that practice, practice, practice is the best advice. Although I had never been on a boat before, Will had 20 years as a commercial fisherman - of course different type of boat and not this specific boat. Haven't had much opportunity to practice due to Will's work schedule, but that will be next step before design changes. To all - thank you again! Much appreciated. Jan
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Old 07-27-2014, 03:57 PM   #11
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I have done a lot of rudder changes on both my boats. Not for slow speed work but for better autopilot performance in rough conditions. The wedges on the trailing edge DO increase performance but not noticeably at low speed. If your rudder is large enough then indeed more practice (not near my boat please) is needed.
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Old 07-27-2014, 04:28 PM   #12
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Jan n Will
We had very poor helm response with our 1978 Marine Trader 36. I made a rudder modification about a year ago and put it on. The difference in the way the boat handles is night and day. I can't believe previous owners put up with it since 1978. We plan on pulling the boat in a couple of months and make the mod permanent. Here is that thread with a couple of pics.

Rudder Size

When we went out the first time I was making tight circles around one of the markers just astounded at how much better the boat handled. I can not tell any difference in the amount of effort it takes to turn the wheel. People say they put small rudders on these boats to help when over hull speed. I don't know if my modification would affect that or not. I am to cheap to go over 6 1/2 or 7 knots. I do know this though, it gives me a much higher comfort level operating the boat in tight quarters.
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Old 07-28-2014, 01:47 AM   #13
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I built a schilling rudder and have a turn radius of 0 ft on a 42ft steel trawler. I can turn faster then most twin screw boats.
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