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[MartinS]

Hi Folks,
I am building a scratch-built Mississippi Padel Steamer which is about 3ft in length.
From what I understand, steering by rudders is not very efficient on those vessels so I am wondering about adding a bow thruster to increase the maneuverability?
My question is how do you decide what size of thruster to use as they seem to come in several sizes?
I would welcome any advice on how to choose one.
Thanks,
Martin

[Umi_Ryuzuki]

If you want to maintain a more scale look, not putting a large hole through the hull, you could
install a reversible windscreen washer pump, like from a Passat. Then just run a three or four
millimeter hose to a brass tube out the hull for thrust to either side. 

[GG]

I'd like to second Umi's suggestion of using an auto windscreen washer pump as a discrete bow thruster.  I started using them this way in the late 1970's and the gentle sideways push a pump would give was much appreciated. The current "pumped" model is based on the US Navies Seaplane Tenders of WW2.


A couple of points though;
1) Only use the "gear type" of pumps as these are reversible.  The single outlet centrifugal types are not.


There are some twin outlet centrifugal type which could be used (I guess they were designed for use in cars with front and rear screen washers?).  They do need three (3) holes in the hull, one inlet and outlets on either side of the hull.  I have used such pumps on a Fire Boat model where I could operate either fixed forward firing jets or one on an elevating platform from a single pump, very handy.


2) Although designed for 12 Volt operation, they still work effectively on a 6 -7.2 Volt supply.


Glynn Guest

[MartinS]

Hi Guys,
Thank you both for the advice.
That looks as if it is the way to go, I'll have a look around for a pump and use that.
Regards,
Martin

[Circlip]

My MK4 Escort had a dual washer pump, nearly sure voltage had to be reversed to select which jets were selected.


  Regards  Ian.

[MartinS]

Thanks, Ian,
I'll have a look for one.
Regards,
Martin

[Colin Bishop]

As Glynn says, search for a twin outlet washer pump.

However, most pumps are intended for specific cars so the size and shapes differ. They will have two output nozzles but the input is usually a wide bore fitting that plugs into the bottom of the car washer bottle. This needs to exit through the  bottom of the hull and it's a good idea to fit a strainer.

You will normally need a speed controller to operate the pump by reversing the voltage unless you rig up an automated alternative method such as microswitches on the tiller (rudder) arm.

There could be some doubt as to whether the output from a car washer pump would be sufficient to assist the steering of a 3ft model though. Bow thrusters are intended to move the vessel when it is at rest and become very inefficient if it is moving. You could spend a lot of money for little gain!

I do recall reading years ago that the best way to improve steering of Mississippi type paddler models is to substantially increase the size and depth of the multiple rudders to give then more 'bite' on the water. If the extensions are transparent plastic they will not be noticeable when the model is afloat.

Colin

[Ralph]

I've never seen it tried but how about a rudder in the bow?  It would need to move the opposite way to the stern rudders to push the bow round.  As Colin says, clear plastic wouldn't be noticeable.


Ralph

[chas]

I can confirm that a twin output windscreen washer pump works very well. I've fitted one to a 42 inch ferry model , the speed of swing is nicely above scale speed but not dramatic. I didn't use a speed controller, just a servo with the arm pushing 2 spco microswitches. I couldn't see a reason why I'd need to change the speed. I control mine with a switch on the transmitter that has centre neutral and goes either way for port or starboard thrust. It's all very simple and intuitive but it's worked flawlessly for 3 years so far.
Charles.

[MartinS]

Thanks for all the excellent advice!
How the pump connected to the washer bottle had me fooled until you explained it...
I agree a strainer would be a good idea.
Transparent rudders, now that is a clever notion.
What about using a voltage uplifter to get 12 volts from my 6 volt batt?
I appreciate that it has been mentioned that the pump will run OK at a lower voltage.
Martin

[GG]

MartinS,
           First, thanks for being someone who acknowledges when people try to answer their queries.

I knew there was something else to add and eventually found a short article on this topic in the August 2011 issue of Model Boats.

In view of other comments I'd like to add a few extra comments;

1) The simple gear pump (just two connections as the inlet and outlet connections are reversible in function) only needs two small holes in the hull sides rather than three that the reversible centrifugal pumps need.  This can be easier to install.
2)General purpose pumps can often be obtained from Motor Factors. This can be much cheaper than buying one made for a specific make or model from a main dealer.  This I found out when the pump on our BMW failed..!!
3) On 6 Volts these pumps can easily turn a large model.  The Seaplane Tender illustrated in an earlier post is 40 inches long and weighs 10 pounds, it may take several seconds to turn through 90 degrees but do you need to spin your models like a top?
4) These pumps loose their turning effect when the model is moving at any significant speed.  But, if moving gently astern, I found you can sometimes use them to steer the model.  It can be handy when the models rudder has no control when moving astern.
5) I've only ever used simple servo operated micro-switches for forward/off/reverse pump operation.  Their action is so gentle that an ESC has never been needed.


Hope this helps,
         Glynn Guest 

[size=78%] [/size]

[MartinS]

Hi Glynn,
You are right, it is only polite to thank someone who has bothered to try and help.
Once again, thanks for all your input it is very useful.
I have ordered a pump that looks similar to the one in the photos and will use a servo and micro switches to control the action as you have recommended.
Regards,Martin

[Tug Fanatic]

I have run models with much more powerful bow thrusters than is being described here and I would extend what Glynn (GG) has said to say that the model need to be effectively static for them to do much at all.

Bow thrusters will improve manouverability but only when you have no forward or astern movement.

[MartinS]

So effectively more useful when docking rather than when attempting to turn while moving?
Perhaps a combination of forward rudders and bow thrusters could be the ultimate solution for a paddle steamer?
Martin

[Colin Bishop]

An anachronism though as paddlers never had bow thrusters although some did have independent paddles and many had bow rudders.

Colin

[JimG]

If you are not building an exact scale Mississipi paddle steam then a bit of thinking out of the box. A late friend once built one but powered it with a submerged propeller with a normal rudder, the wheel was free turning. Under power the wash from the prop turned the paddle and it loooked realistic, having the rudder behind the prop meant it steered well. It did mean though that he couldn't lay it flat on the bench but needed a stand.
Jim

[MartinS]

Yeah, I read that some had up to 5 rudders!
I can see how that idea would work with a prop and a rudder and allow the paddles to turn freely.
So plenty of choices there.
Although a thought just occurred to me, how would you control 4 rudders from one channel?
2 at the stern and 2 at the bow, it would not be practical I would think you use a linkage over a hull of that length so preferably I would use 2 servos on the same channel.
They would need to be configured so that they moved in opposite directions to make the turn.
Plus a bow thruster on a separate channel for delicate maneuvering when docking.

Is that even possible?

 Martin

[Umi_Ryuzuki]

The Empress of the North was built with Schottel drives at
the stern, just ahead of the paddle wheel.
 
https://www.nicholsboats.com/uploads/pdf/S-142%20Empress%20of%20the%20North.pdf

[Tug Fanatic]

So effectively more useful when docking rather than when attempting to turn while moving?
Perhaps a combination of forward rudders and bow thrusters could be the ultimate solution for a paddle steamer?
Martin

Yes. 

[Tug Fanatic]

The Empress of the North was built with Schottel drives at
the stern, just ahead of the paddle wheel.
 
https://www.nicholsboats.com/uploads/pdf/S-142%20Empress%20of%20the%20North.pdf

Somehow feels like cheating but I note that the paddle wheel is still power driven to get the water churning effect. Both model & full size paddlers that I have seen where the paddle wheel is driven purely by the motion of the boat but is unpowered just don't look right.

I would add that whilst the driven paddle wheel helps the illusion when I look at it I cannot fool myself into believing that it would drive the boat as it just doesn't look like it would shift enough water.

[KitS]

2 at the stern and 2 at the bow, it would not be practical I would think you use a linkage over a hull of that length so preferably I would use 2 servos on the same channel.

Why not? Some flying RC aircraft do exactly that, driving the elevators and rudder by pushrods or snakes from servos in the cockpit area. Some of my RC gliders have fuselages 4-5 ft long and that works OK.


With a boat the main problem would be finding a way past all the other stiff in the centre of the hull, motors, drive shafts, batteries etc. but with the pushrods you could a series of bellcranks and with snakes you'd need to attach them to hull sides out of the way.

[John W E]

Hi there


A good while ago whilst building another model I required a bow thruster and I was originally going to make my own.  This gentleman, Poll, on this forum showed us how he constructed his bow thrusters and they seem to work pretty well.


Here is a link:


SEAFORTH CONQUEROR (modelboatmayhem.co.uk)


john

[Circlip]

Coupling over long distances - closed loop, not snakes (ugh) or has the 'Y' lead become obsolete?


Regards   Ian.

[KitS]

Coupling over long distances -, not snakes (ugh)

They work fine for me, the RC sort, not the slithery sort.............

[MartinS]

John, the link you provided doesn't go to the post.
I tried a search but it did not return anything.
Aha, a Y lead, now I've looked that up that seems to be the bit of kit I will need.
Thanks, everyone, I'm getting closer now.
Martin