Tom, thanks for the information. I had already consulted the forums on paddleducks, but for reasons I do not want to discuss, I prefer to keep the discussion on this site. Plus I am continuing with my own investigation.
Roy

My first paddle boat built in 2001, scale Glen Usk. As I had no knowledge at all I kept the draft scale, 1.5" big mistake. With a boiler above the CofG, she is very tender. The batteries for the radio & gas control are mounted on a plate, the plate pivots from port to starboard. Coming from aero modelling many years a go, I use the aileron stick to fly her. The weight transfer keeping an even keel.
Building the Duke of Devonshire I have increased the draft 1" over scale. Also made my own boiler with 2 drums side by side reducing the height. No problems except in strong wind.

Hi,
I recomend repeatedly to put your question to paddleducks.There you could certainly find modelers, who have experience with models paddlesteamers and can help with your problem.

My model Lulonga has two independently driven wheel, each has its own ESC. Driving is a double ... classic rudder control but especially ESC ..drive back and forth is controlled via Throttle position on transmitter, using a Y cable. This allows the trimmer to adjust the speed .. optimally 90-150 rpm. Adjusting the speed of motors to the same value terms set by a trimmer on the transmitter.
Own control direction is a mix throttle with "ailerons" channel (1 and 3).
This allows you to change the speed of each wheel independently on Throttle position and thereby control the direction of navigation. . it is even possible to change the sense of rotation, so that the wheel rotates against each other. This ship turns almost on the spot.
A wheel diameter of my Lulonga is 150 mm.
A similar problem like yours, I did not met personally.
next ..and perhaps your main problem may be that you can not mechanically practically ensuring that each wheel had the same number of turns .. Each motor has the same input voltage slightly different speeds .. and without trim it is Impossible to adjust.
Additionally .. the question is the size of the model.
As regard to speed of paddle wheels (rpm) I think it is practically negligible, if any blade touches the water before the blade wheel on the opposite side of the model.... maybe you need a proper trim then.
Paddle wheel drive model has its own specific problems.
The main problem is, that the model has a closed paddlebox . it happens that the water, instead of being driven backward, is suctioned into paddlebox ,rotates similarly as in the pump , and model practically do not move.
Help .. proper area of holes in the paddlebox side panels (at least).
Lulonga has louvers fixed at the back of paddlebox .
My first paddleboat was australian type steamer Ned Kelly(live steam propulsion 115 cm long hull, hull breadth about 20 cm without paddleboxes). Her superstructure was too high and and a relatively small breadth of the hull caused great instability while sailing - the breadth recommended at least 25 cm. When I removed the superstructure, Improved stability, then model sailed with straight keel very exemplary. had the wheel of simple construction made of plywood, very effective .. though not as nice as yours at your model.
I have model ,at present , quarterwheeler Lulonga(see gallery, the long article about model building you can find at Paddleducks) .
She has also the paddlewheels of my homemade construction, nevertheless very heavy. Her stern sits very deep in the water
The model is about 75 cm long, but due to the structure and shape of the hull would be good if and its length was at least 85 cm. I have a problem lengthwise balancing model.
Tom

Thanks to everyone for their input. For those of you who may have been intrigued (or bored) by this discussion, I have more information.
Today I ran the tug with both paddle wheels clutched together and synchronised, in other words, paddles on both sides were entering the water at the same time when on an even keel. The water on the pond was almost flat calm, with no wind. Under these conditions there was no noticeable list when the boat was run ahead or astern.
When I declutched the wheels and ran them independently the list reappeared, although it seemed to be random.
I cannot claim to understand in detail what is happening, it seems clear that if a paddle on one side meets the water before a paddle on the other side, this mismatch results in a force tending to cause a list.

Hi,
I believe, plenty of interesting questions and answers about paddle boats you can find at > www.paddleducks.co.uk <
forum specifically for modellers and models of paddle steamers of all sizes and types
Tom

Had a look at your motors set up. Twin motors may not always run with the paddles in a balanced state so if one is entering the water earlier than the other it will tend to dig in pulling the boat down on that side. My attempts at rowing a small dingy spring to mind.
I note you have a similar problem when starting and at full speed on another tug and I suspect this may be where the cause lies. Do you control both motors from one ESC? if you had two ESCs you could experiment with staggering how you start each motor to counter balance the effect. I have a friend who is using a giro (from a model helicopter) to counteract a similar problem on a model boat.
Hope this helps and you can find a solution
Cheers
Dave

OK well in that case I have to conclude that your paddle wheel spindle axis is not at a true right angle to your hull centre line.

A small error would cause your hull to be moving at an angle and again produce the results you report.

Please accept I am treating this as a pure theoretical problem so I may well be in error.

HI guys,
Thanks for the feedback.
You are correct that torque reaction on a propeller driven boat with shafting along the boat axis will have this effect. I have that on my other tug, but it's only noticeable under full power starts and stops. Under normal running it's not visible.
Please take a look at the very first entry of my build blog on this model, under 'Director class tug'. You will see that it is a double reduction belt drive and all axles are transverse, none along the length of the boat.
The paddles are scale size and it is ballasted down to the correct waterline level. it doesn't seem to be unduly tender; I'd say it was about right.
Roy

I would agree with Haverlock's reasoning.
Another possibility is the depth of draught relative to the paddles as if the model is slightly top heavy the paddles are causing the tilt if they are high above the water. Also any heavy bits in the hull mounted above the metacentre will make the hull tender and prone to tilting.

how is your drive train arranged? I ask because the obvious is a torque effect.

if you have a single motor arranged along the length of your boat with a gear box, as the load, comes on the motor will try to revolve in the opposite direction to that of drive.

The fact that the direction of list follows the direction of drive is the indicator.