Chum, et. al., I'm continuing the discussion on US towboats over to a new topic: "US Towboats on the Eastern Rivers".

Lew

Thanks Lew for the photo describing your tow boats rudder linkage arrangement. Obviously well thought out. It seems to me that because tow boats operate in shallow water Zdrives would be impractical due to how far they extend below the hull.
Your description of turning a make up of numerous barges makes me realize there is a vast difference in towboat & tugboat operations. Maneuverability issues are not generally the same. An articulated tug/barge might approach similarity at some level.
It’s been so long since I’ve run my twin ASD tug, SVITZER FERRIBY that I don’t remember if they were reversible. The props were opposite hand, outward rotating.

I was only joking about no bow thruster.

Most of the towboats operating on the Mississippi River have a maximum draft of 9 feet. With the flanking rudders there is no need for bow thrusters. Bow thruster were made for pivoting a sing boat not 1,000's of tons several 1,000 feet our in front of the towboat. (I'm back on my PC now so I can add more photos of the setup.) Steering is done via levers, no wheel.

In my model I have all the rudders connected together. On the real boats the flanking rudders are controlled separately.

F.Y.I., I am attaching the drawing (one of many) that I made of the Arne Christiansen, a Schottle (or "Z") drive towboat. I have the drives and never the time to build it. Interestingly enough, the propellers turn in one direction only. There is no true reverse. The Schottles turns 360 degrees so they direct the boat in any direction and are independent of each other. I had a phone call from the captain and he told me how this boat was fantastic to operate. The last photo is the designers concept model.

Lew

Chum.. Not to worry about this thread (I started it). Most threads evolve in the same manner. Lew

What? No bow thrusters?😂😂 That is some impressive Lew. I didn’t know t.hat tow boats had open rudders as well as Korts & flanking rudders. Were the P&S steering components operationally linked hydraulically, electricically, etc? Their skippers & you
must be exceptionally dexterous with the controls.
The publication TUGS,TOWING, & OFFSHORE NEWS has recently described several new tow boat builds. I’ll have to read them more carefully.
I apologize for totally high jacking the original thread. Any future posts I make on the topic will be in a new thread.
Your build is very impressive!

Chum, no, it can't walk sideways. What this arrangement can do is pivot a "tow" (long string of barges) without moving in any direction.

Think of your arm a a tow and your shoulder as the towboat at the aft end of the tow. Point your arm straight ahead. Now swing your stiff arm left or right. Your shoulder or towboat turns the tow. You can also push or pull the tow forward and aft at the same time just like swing your arm as you step forward or backward.

You can see more on this towboat in my harbor, see link.

Also, check YouTube for "marktwained" for some real amazing US towboat videos taken by the captain himself with full explainations.

Lew

harbour/110651

Steerable Kort is my default. Lew, you tow boat encompasses a very maneuverable arrangement. Bet you can walk it sideways!
As far as I know many earlier tow boats & harbor tugs had dual open props with flanking rudders. The addition of Korts made an already agile tow/tug REALLY maneuverable.

Ron, I believe that the real tug photo was that of a retro-fit. Still probably not as efficient as a true Kort with the propeller inside of it. Not finding much on the "Texas Nozzle". "Steerable Kort" is where the Kort is around the perimeter of the prop but turns from side to side for steering.

My towboat that I built years ago has two drives with fixed Korts, after rudders, and four flanking rudders. This is what a lot of towboats use here in the U.S. The boat can pretty much spin in its own length. (See video.)

I still have my pair of Graunpner Schottles for another towboat I never got around to building.

Lew

https://youtu.be/wSUH3PX5QMY?si=d3se2GRWq3cUZdG0

My bad Ron. I didn’t look closely at the photos. I’m not a naval architect but without seeing any hydrodynamic explanation my guess would be that the increased maneuverability is primarily due to the larger rudder shown on the 1:1 on the ways.
Do you have a link to a description of how the nozzle works? The blade tips falling outside the nozzle diameter, & as Lew pointed out, screw well forward of the nozzle inlet also puzzles me about the functionality of the nozzle itself.
Any naval or marine engineers on this site that can offer explanation.Causes me to wonder if this arrangement was the precursor to Korts. Do you know if the Canadian naval architectural/ design firm Robert Allen has issued any papers on it?
BTW, given my experimentation, I stand by my preference for Korts over ASD drives for models. That said, one huge advantage of the ASD drives is that a tandem install of ASDs enables the skipper to walk the tug sideways.

Chum

I am not talking about Schottel ASD drives, Marcel uses the standard motor to shaft to propeller (wheel) as tugboats of that era. When he bought the tugboat it had been fitted with a Texas Nozzle on the rudder. There is nothing surrounding the prop. Study the photos he sent me.

First two photos are my model

Ron, I’ve done a lot of research on & experimentation with Kort nozzles on model boats. I was particularly interested in
discovering if Schottel ASD drives offered a significant maneuverability advantage over Korts. Schottels are mechanically much more complicated than Korts & have a lot more moving parts that can fail.
My experimental process indicted, at least to me, that the difference was not significant enough to warrant the use of Schottel drives.
Mike, glad I was able to give you some ideas.