50' Navy Utility

[kapnd]

Old thread, I know, but I wanted to reopen discussion re the reversing rudder, if anyone is interested.
This the OEM configuration, and I consider it worthless.(pic)
It’s about a 3” tube with a little rudder under it. The barnacles love that tube, and it’s very hard to clean underwater.
The prop walk is very pronounced, it swings the stern 30* or so when transitioning from forward to reverse, rudder has no bite until boat is moving in reverse with some momentum, shifting to neutral helps then.
The keel stops 6’ or so in front of the propeller. This gives the prop clean water to work in for sure, but I’m thinking that it enhances prop walk too.
I’m thinking to replace the tube with the biggest plate rudder I can fit into the space. That failing, the whole second rudder works comes out and the hole gets filled in. The added linkage adds steering effort at the helm too, I’d be pleased if that improved!

 

[Sailor of Fortune]

Old thread, I know, but I wanted to reopen discussion re the reversing rudder, if anyone is interested.
This the OEM configuration, and I consider it worthless.(pic)
It’s about a 3” tube with a little rudder under it. The barnacles love that tube, and it’s very hard to clean underwater.
The prop walk is very pronounced, it swings the stern 30* or so when transitioning from forward to reverse, rudder has no bite until boat is moving in reverse with some momentum, shifting to neutral helps then.
The keel stops 6’ or so in front of the propeller. This gives the prop clean water to work in for sure, but I’m thinking that it enhances prop walk too.
I’m thinking to replace the tube with the biggest plate rudder I can fit into the space. That failing, the whole second rudder works comes out and the hole gets filled in. The added linkage adds steering effort at the helm too, I’d be pleased if that improved!

your report is probably the most valid I have heard... I know you have had your boat for a while.. Real world usage. Thanx. It will be interesting to hear your reports of bigger/modified rudder..

 

[Jeff F]

I removed mine after about a year owning the boat. I left the tube intact and capped it inside. Not long after my stern thruster died, so I've been without either since. I've learned how to do without.

My experience is that it helped with some maneuvers and made some maneuvers more difficult. Pivoting the boat by backing and filling with the rudder hard over didn't work as well because the two rudders are tied together. So a shot of reverse would stop the turn rather than allowing it to continue unless I spun the wheel when shifting between F and R. I found that a bit tiresome.

I think you're right in saying that the shortened keel and flat aft sections make the effects of prop torque more pronounced. The stern moves sideways very easily. I had a recent discussion with an experienced builder considering a yacht conversion on one of these boats, and he was talking about extending the keel aft for better directional stability and handing.

This may be fodder for another discussion, but I have two props, one 3 blade and the other 4 blade. The four blade prop shows less prop torque in reverse but a bit more in forward. I don't know why, but it's quite noticeable on my boat.

I thought about the idea of independent control of the forward rudder using a jog lever or something similar, but the complexity didn't seem worth the effort. Looking at work boats with flanking rudders I'm pretty sure that they have the ability to decouple control from the main rudders.

With reverse prop torque pulling the stern to port I'm more comfortable tying up on my starboard side. I can control the pivot of the boat with the rudder hard over to port with throttle and shift only, and backing out is easier with the reverse torque pulling the stern off the dock. I think of this as embracing the characteristics of the boat rather than fighting against them.

 

[kapnd]

The finger pier is too short to access the cockpit from, so I back into my port side slip, which is almost at the end of the fairway, not much room for error!
Hard over to starboard, reverse well before lined up with the slip, walking to port until momentum is achieved, go to neutral, forward, fill, back, fill, etc.
Wind is always a factor, when it’s from the north, it’s tricky as hell.
It’s not beautiful maneuvering, I’m sure it looks haphazard from the dock, but I’ve been doing it long enough to know that there’s not any other way to make it happen without thrusters.
The propeller I was able to find had a bit more pitch than the beat up oem, and I think that adds to propwalk as well.
The beautiful yacht that I share the slip with has so far not taken any hits from me, however it’s anchor has left some scratches on my boat!
The day I bought the boat, totally green as to its quirks, I pulled into Lahaina harbor to fuel, but the fuel dock and adjacent loading docks were full of commercial boats, so I was forced into the fairway, had a hell of a time getting turned around. Finally got a spring line on another boats bow to lever around on, Whew!
I’m really enjoying the boat, fishing day trips regularly far offshore, with occasional extended outer island trips. The boat rolls significantly when quartering, but altering course a few degrees usually mitigates that.
2 gph at cruise, 7-8 knots at about 1500 rpm.

 

[Sailor of Fortune]

The finger pier is too short to access the cockpit from, so I back into my port side slip, which is almost at the end of the fairway, not much room for error!
Hard over to starboard, reverse well before lined up with the slip, walking to port until momentum is achieved, go to neutral, forward, fill, back, fill, etc.
Wind is always a factor, when it’s from the north, it’s tricky as hell.
It’s not beautiful maneuvering, I’m sure it looks haphazard from the dock, but I’ve been doing it long enough to know that there’s not any other way to make it happen without thrusters.
The propeller I was able to find had a bit more pitch than the beat up oem, and I think that adds to propwalk as well.
The beautiful yacht that I share the slip with has so far not taken any hits from me, however it’s anchor has left some scratches on my boat!
The day I bought the boat, totally green as to its quirks, I pulled into Lahaina harbor to fuel, but the fuel dock and adjacent loading docks were full of commercial boats, so I was forced into the fairway, had a hell of a time getting turned around. Finally got a spring line on another boats bow to lever around on, Whew!
I’m really enjoying the boat, fishing day trips regularly far offshore, with occasional extended outer island trips. The boat rolls significantly when quartering, but altering course a few degrees usually mitigates that.
2 gph at cruise, 7-8 knots at about 1500 rpm.

Do you have the 6-71 or Cummins of the newer versions?

 

[Jeff F]

Do you have a bow thruster? There are lots of maneuvers I wouldn't try without mine. Now when I'm in close quarters maneuvers I focus first on stern position using a combination of prop torque and forward rudder position, and use the bow thruster to position the bow relative to the stern. It sounds strange, but works for me.

When I was trying to use the nozzle I found that it was sensitive to throttle. There wasn't a big effect until I really bumped the throttle in reverse, then it was really noticeable.

 

[kapnd]

No bow thruster, just concentrate on getting the stern pointed in the right direction, bow is usually not too far off that I can’t correct it when I get a line on the dock.
Mines a 94, came with a 6BT Cummins, or I’d have passed on the deal. I’ve dealt with DDs more than enough for one lifetime!
Throttling up in reverse only works for me if I’ve got lots of room behind the boat to get straightened out, which is not available at my home slip.
As I mentioned before, I don’t think there’s enough blade on the little rudder. Theoretically, there’s more surface area in a tube than a flat plate, but in practical application, it’s mostly ineffective.

 

[kapnd]

Oops!
Here’s some more

 

[Jeff F]

No bow thruster, just concentrate on getting the stern pointed in the right direction, bow is usually not too far off that I can’t correct it when I get a line on the dock.

Makes sense, but doesn't sound easy ?

Thinking about alternatives for you I don't think a plate rudder would perform any better than the cone, apart from ability to keep clean. The stock fitting fills most of the available space. A plate might work better at lower throttle, but that tapered cone is a powerful nozzle with more flow over/through it.

As I said earlier, I thought about getting independent control of the two. I have a spare linear drive, but never got around to trying it. That for me would have probably been the best solution. I can put the cone back in easily and may yet try it at some point.

 

[kapnd]

Not a cone, it’s a straight piece of pipe with a small keg on the bottom of it.
Somebody sold he government a Rube Goldberg idea, and managed to keep getting paid for it in several iterations over the years, in which time its development was a miserable failure.
This is a small example of how our tax dollars get spent!
Thank goodness, the rest of the boat is intelligently constructed, aside from the fact that the original wiring is all one color…

 

[Jeff F]

Not a cone, it’s a straight piece of pipe with a small keg on the bottom of it.

Huh. Mine is tapered, getting wider aft. I can see how a straight pipe might not be the greatest solution.