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Old 01-05-2019, 04:14 PM   #41
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The rudders on my boat are good size for slow maneuvers, and usually I leave them centered and use the twin props, but that turns out to be the easy stuff. When you want (or need) to do something a little more sophisticated, rudders do matter. If your rudders are *actually* undersized and metal, they can be enlarged easily by someone who knows what they're doing. If fiberglass then its a different situation.

Ken
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Old 01-11-2019, 02:52 PM   #42
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It seems to me that the OP has a boat design that is all windage, with very little keel surface to provide the force of lateral resistance.
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Old 01-11-2019, 03:58 PM   #43
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On my 45 ft Bluewater Coastal Cruiser I was told that I have high speed rudders and that's why it is hard to dock or control at low speed. Is there a way to add on to the rudders to get a larger surface or due I have to buy new rudders.
We have a 51 ft Bleu water Coastal cruiser and the rudders work great. BUT for docking I leave the rudders centered and only work with the engines.
Leaving the engines at tick over ( just stationary ) and put them in and out of gear to maneuver

simple

at slow speeds rudders do NOT work well so forget about new or bigger rudders
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Old 01-11-2019, 04:48 PM   #44
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I owned a Bluewater 45 years ago. It had a pair of 330 HP freshwater cooled gasoline engines. Nice big props that could throw a lot of water when needed. The rudders were small. It is a planing hull, light for its size. Lots of wimdage and floated like a leaf. Any wind would make it a handful on slow speed maneuvering. But with a little practice working the throttles and gears I could turn her in her own length, back into any slip that was wider than the beam and stop her on a dime. Forget about the rudders. You have a very maneuverable vessel. Learn to use the props to control her.
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Old 01-11-2019, 05:09 PM   #45
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Originally Posted by kartracer View Post
On my 45 ft Bluewater Coastal Cruiser I was told that I have high speed rudders and that's why it is hard to dock or control at low speed. Is there a way to add on to the rudders to get a larger surface or due I have to buy new rudders.
What do you mean by "low speed?" If you're talking about when you come down from your cruising speed of 15+ knots to around 2-4 knots, then perhaps you do need larger rudders to help steer when you turn the wheel - although you could easily steer with the engines and the rudders mid-ship.

Docking is another matter altogether. As some have suggested, you can use your rudders to some effect when docking, but of greater effect is the use of your engines, port/starboard and forward/reverse. If you haven't learned how to use your engines (at low rpms) to twist your boat around and use the prop-walk to your advantage, perhaps you need to read a few books and practice, practice, practice!
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Old 01-11-2019, 06:45 PM   #46
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I can't find a reference for the 45ft Bluewater Coastal, only the 43' and 47' which appear to be single engine gas powered.

On a slightly related subject I have a Leopard 47' PowerCat. At five knots or less you tighten the friction lock on the wheel so you won't be tempted to use it and steer with differential power. However, I am interested in rudder extensions for long-range cruising on one engine. The crews who deliver these boats all over the world from the factory in Cape Town, South Africa use this technique with extended rudders and then swap them out for stock rudders after delivery. This substantially extends the range of these boats. The extended rudders better mitigate the effects of the asymmetric thrust during single engine operation.
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Old 01-11-2019, 07:28 PM   #47
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Do lLeopard power cats have saildrives where the rudders are in front of the saildrive like the sailing version?
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Old 01-11-2019, 07:58 PM   #48
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I can't find a reference for the 45ft Bluewater Coastal, only the 43' and 47' which appear to be single engine gas powered.

On a slightly related subject I have a Leopard 47' PowerCat. At five knots or less you tighten the friction lock on the wheel so you won't be tempted to use it and steer with differential power. However, I am interested in rudder extensions for long-range cruising on one engine. The crews who deliver these boats all over the world from the factory in Cape Town, South Africa use this technique with extended rudders and then swap them out for stock rudders after delivery. This substantially extends the range of these boats. The extended rudders better mitigate the effects of the asymmetric thrust during single engine operation.

I found a dozen of them like this one in five seconds. Don't know what you are looking at but the subject vessels regardless of size are twin gassers.
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Old 01-11-2019, 10:59 PM   #49
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I would love bigger rudders. They are so lethargic even at my 8.5 it cruising speed. I would definitely like larger rudders someday.

When docking, idling the engines and using forward and reverse only isn’t enough. I often have to use at least 1000 RPM in both forward and reverse to really make anything happen or to overcome any kind of wind. I do bring the engine to idle before shifting, then bring the rpm back up again if need be.

I’ve been told 1200 rpm is safe in reverse. Is it the prop or the transmission that doesn’t like much rpm in reverse?
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Old 01-12-2019, 05:57 AM   #50
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Quote:
Originally Posted by kartracer View Post
On my 45 ft Bluewater Coastal Cruiser I was told that I have high speed rudders and that's why it is hard to dock or control at low speed. Is there a way to add on to the rudders to get a larger surface or due I have to buy new rudders.
All conglusions are correct if you have twin engine&twin rudder.Ex.owner of my boat adviced also using engines at idle only while docking/maneuvring But If you would like to change the rudder dimensions please check the existings first.
As thumb of rule;

Rudder height : Should be 2/3 of draught,

Rudder lenght :Should be 2/3 of rudder height ,up to 15 Knots speeds.

Than you can reduce each rudder area by 20% if boat has twin rudders.

This is old DNV standarts for fishing trawlers.
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Old 01-13-2019, 08:37 AM   #51
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Imported several Taiwan yachts in the late 70's and early 80's including a lot of Monk 36's from the MMC yard. All had small rudders. Easy fix, went next door to a lumber yard, bought a length of 2 x 4 and had them cut it diagonally. Sealed with thinned epoxy and bolted and bedded to the aft rudder edge - problem solved.
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Old 01-15-2019, 04:31 PM   #52
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On slow single screw boats you can put rudder cheeks of both sides of the rudder. It is about 15 degrees . On a tug a owner consult with a N/A and he will tell you the proper size. When I ran the TEXACO Sky Chief it had that and we called it a Barn Door Rudder. Should you do that do not put the rudder hard over at full speed. Note the tug has cheeks on the rear. The cheeks are a wedge that gives the vessel more rudder power.
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Old 01-15-2019, 06:11 PM   #53
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Another method is to "box" the rudder in by adding side plates to each side on standoff plates. This gives more thrust and control, almost a Kort Nozzle effect. Here is a pic of how I did that to one of my RC tugs.
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Old 01-16-2019, 02:43 AM   #54
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Well, I hate to throw a bucket of cold water on those who say you donít need rudders to dock a twin screw boat but I would disagree. Use of rudders while docking greatly enhances the bag of tricks at hand for variable conditions including high current, breezy days and tight spaces. You will need rudders to walk a boat sideways into a berth. If you donít know how to do this, have someone show you how, it will certainly enhance your boat handling skills. Although I have a bow thruster, I seldom find use for it as I use my rudders in conjunction with engines to get into tight spots. Oh and btw I consider my rather small rudders to be a detriment and would rather have larger but they work well enough for me to single hand my 53í, 62,000lb boat into most berths.
"Diddo"

My NP45 has a keel and some weight (40,000 lbs) and a huge rudder which, makes docking so much easier.

My Carver C34's rudder was worthless below 5 knots but when used properly with the twin screws and thrusters the boat was dockable but rarely easy. With no keel the wind would take that boat and make life miserable. Even with the thrusters. It was a light boat at 18,000 lbs and had a tonne of windage. It was always a white knuckle docking fiasco with the constant afternoon winds on the San Francisco Bay.

Get a bow thruster and have a captain work with you for a day.

You will get it.
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Old 01-16-2019, 02:53 AM   #55
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If one has two engines, why would one need large rudders in low-speed situations? Assuming one knows how to operate twin engines for maneuverability.
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Old 01-16-2019, 07:22 AM   #56
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If one has two engines, why would one need large rudders in low-speed situations? Assuming one knows how to operate twin engines for maneuverability.

Small rudders donít do much at low revs. The advantage of large rudders is they are of some use at even when in nuetral. With two engines and small rudders, bursts of power are required to manoeuvre. This takes time to perfect.
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Old 01-16-2019, 07:32 AM   #57
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I guess the difinition of small and too small needs a bit more defining.

To me, too small is where bursts of power are always needed versus just occasionally or in extreme conditions/manuevering. But that probably is not how everyone sees it.
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Old 01-16-2019, 11:31 AM   #58
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When in idle (3kts) I have very little control with the rudders. This makes maneuvering in tight marinas more stressful than I feel it should be.

My old marina was tight. I feel like riddlers should be able to control the boat in idle. For me the most part they do, but I would often have to use two full turns on the wheel to make a slight correction. And even still I’d have to use power or transmission to help.
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Old 01-16-2019, 11:32 AM   #59
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Hereís the pic
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Old 01-16-2019, 11:53 AM   #60
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When in idle (3kts) I have very little control with the rudders. This makes maneuvering in tight marinas more stressful than I feel it should be.

My old marina was tight. I feel like riddlers should be able to control the boat in idle. For me the most part they do, but I would often have to use two full turns on the wheel to make a slight correction. And even still I’d have to use power or transmission to help.
That's not all that atypical at speeds of 3 knots or so, especially if there is any wind or current.

In tight areas, most move to throttles and shifters rather than rudder. Many diesel boats with decent rudders have such high idle speeds in tight areas, they are in neutral on one engine, and alternate to go straight.

And that last picture doesn't even look all that tight.
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