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[rgl2422]

I've jumped in the deep end and bought an Imara kit which will be steam powered (twin prop) and radio controlled. I've done lots of straightforward R/C stuff over the years - trains and boats and planes  and am planning to install pumps and other goodies - but am confused about how you rig (and steer) a boat if you have one channel for each engine / prop shaft shaft and another for the rudder. I have read that you can use a mixer but how exactly does this work in practice? Any advice would be welocme.


Richard.

[Stavros]

Contact Brian Roberts on here he has built an Imara I htink he has a build thread
 
 
Dave

[irishcarguy]

A simple fix is to fit an ACTion P94, it will run both motors & is a mixer too, 3 for the price of one. Now sold by Component Shop. Mick B.

[grasshopper]

If , as you say you're building a steam powered, twin screw tug then rudder is the way to go....so much easier than differential steering with steam power- either twin motored or one motor with drive to each prop.


If you're using electric motors then the situation is different and easier. All the above is dependent on how many channels you have available on your radio gear. Even with twin motors,I would be inclined to have independent throttles and rudder - gives more scope for manoeuvres, just invest in a 4 channel RC set.

[Colin Bishop]

I did the original Imara review for Model Boats back in 1990 or so. My model was electrically powered. I found that with the twin screws the rudder was out of the propstreams and not very effective with a turning circle approaching the Rings of Saturn. I think that is partly why a single screw version was subsequently introduced. For low speed steering I found independent motor control to be essential, I used tank steering at the time but a mixer would be the way to go with an electric version. Obviously independent control of steam engines would be more complex.
 
Colin

[rgl2422]

Thanks for all the contributions chaps. Would I be right in thinking:


1) That being able top control the two engines / motors separately is a bit pointless and that it's better to run them at the same speed and just rely on the rudder for steering and
2) That the magic R/C 'Mixer' combines the throttle and steering functions?


Sorry for my ignorance!


Richard

[rgl2422]

Thanks very much Colin - I'd posted my last post before reading your very helpful reply. I have read your review many many times and it is beside me as I type! I will head for the workbench now!


Richard

[Martin (Admin)]

"a turning circle approaching the Rings of Saturn"    

[Colin Bishop]

It would be useful to hear from others who have built the twin screw version of Imara to see if prop sizes etc. make any difference to the steering characteristics.
 
Martin, I hesitated to describe it as the orbit of Uranus....
 
Colin
 
 

[Perkasaman2]

I'm not sure that this is relevant or possible on a steam powered model, but, props should be outward turning to aid manoevrability. Inwards turning twin props improve performance. (Viewed from the stern looking forward.) Handed propellors are needed.!!!!!!!!   

[rgl2422]

Handed props now purchased, along with suitable mixer and other R/C gear from Howes of Oxford - they have a resident R/C boat expert - highly recommended.


Richard

[Shipmate60]

Sorry Perkassaman the other way round.
Turning inwards the propwash hits the counter and is directed on to the single rudder.

Bob

[Perkasaman2]

Hi Bob, when twin props are fitted and handed the same way it is often necessary to offset the rudder to achieve straight running. All props give some lateral or side thrust in the direction of rotation. This slight sideways thrust effect is additional to the linear thrust along the propshaft axis generated by the prop. It is useful for swinging the stern off when alongside another vessel or at the dockside. The outward turning prop's thrust will, of course, still also be deflected or vectored off the turned  rudder when necessary. As far as I can find out the above is true with all hulls, whether displacement or not. My interest is primarily higher speed planing hulls and the inwards turning props will give some small help in supporting the stern at speed. The obvious benefit with either inwards or outwards turning props is neutral steering at all speeds which is very helpful.
There was a very interesting thread earlier about props and handedness. Sorry for nor replying earlier.