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[tonyH]

Just planning the next build which is a 3 screw passenger ferry with a single rudder. The model is about 4ft long and fairly narrow. The outer screws will have independent control so is there any practical reason to power the middle screw or would a free-wheeling one adversely affect the manoeuvrability?
Is there any affect on full size vessels?
Thanks
Tony

[Shipmate60]

The Action mixer has the provision for a third shaft so you could have all 3 props controlled by rudder and single throttle channel.


Bob

[tonyH]

Thanks Bob. Doesn't the middle screw unbalance or reduce the turning effect if there is a big difference in the direction of thrust of the outer ones?

[John W E]

Hi there


Depending on how you have the setup of the control of your propellers - it will affect the turning of the vessel one way or the other - depending on the way the propellers are rotating.  In other words if the centre prop rotates in the same direction as the portside - it will have a better turning affect to the port rather than the starboard.


If you are going to use an ACTion mixer, the centre motor is controlled via your throttle stick and it isn't affected by the movement of your rudder.   Now, if you are really really clever and you have a set of 'old' 'very very old' speed controllers, which contain the chip ZN409 in them, such as early Electronize and the early ACTion ones, you can put a switch in the central signal wire of the speed controller, which allows you to switch the speed controller on and off.  Therefore if it is the centre motor that you have switched on and off, it allows you to tootle around the lake using the two outboard props and when you want that extra bit of speed, you switch in your third motor.


Sadly, with today's programmable speed controllers, you cannot do this, as the speed controller memorises the set position of your throttle stick - and therefore it won't work, unless we have a very clever person amongst us who can re-programme the modern day speed controllers.


Here is a link to when I built my RAF Launch which has 3 props - there is a also a photograph of the above layout where the centre motor is switched.


https://www.modelboatmayhem.co.uk/forum/index.php/topic,9758.msg90496.html#msg90496

[tonyH]

Thanks John, that's the sort of situation that I was wondering about and what prompted the question. The boat is closer to 5ft rather than the 4ft I mentioned and at 15lbs could be a bit of a b****r pulling away from the pond side. I suppose that any decision should be made post-build when I find out whether any additional power, from a third, driven screw is needed.Meanwhile I can carry on looking for a few more Action P80's to add to the one kindly supplied by Pete (Klunk) and now in HrMs Koningin Willie!
Tony

[Geoff]

I would counsel that the center propeller is powered as the prop wash will act directly on the single rudder and make the boat much more controllable as otherwise the rudder will only work once you have a reasonable speed.


Cheers


Geoff

[tonyH]

Thanks Geoff, I've never used a mixer so I'm trying to get a picture of how, for example, I could swing the bow away from the dockside where, I presume, the land side screw would be set ahead and the outer side screw would be set astern. The central screw would be stationary until the ship was clear. If I use a mixer and the throttle stick is at the stop point, will the outer props work to do that by moving the stick sideways alone? John W E mentioned a switch for the centre screw ESC with early P80's or similar and since these have got VERY fine, albeit noisy, take up, I'll try any options!
It's almost as if any even number of screws is OK but odd numbers are......interesting!
Tony      

[John W E]

hi there Tony


If my memory serves me rightly, and I will have to check on this - the modern ACTion mixers have a facility where you centralise your rudder and throttle stick and when you move the rudder stick to either port or starboard the props rotate in such a way that it moves your vessel in either a clockwise/anti clockwise direction, without applying forward motion to the vessel.  So, this means that the vessel basically could be at the quayside and you move your rudder stick to the correct direction and it will swing the bow out from the quayside without moving the vessel forward.


The other option on this modern day mixer is you have to apply a slight forward or reverse and then you can engage the rudder/s which in turn will either speed up one prop and reverse the other one to match the rudder movement.


Hope this is of some help.    I do have the instructions somewhere for setting the ACTion mixer up.


Also, you know, a Company called Forge, they do a mixer as well and that is pretty good.  Food for thought for you.


John

[tonyH]

Thanks again John, I think I'm going to have to set up a dry desk-top trial system since I haven't even got to the keel laying stage. This is one of those rare projects with a family connection that deserves time. I'll have to "borrow" the P80's from Koningin and my Project X and sort out either a Forge or Action mixer. I must admit I like the Forge bits so........
Tony

[Colin Bishop]

Tony,
If you visit the Component Shop website and click on the P94 or P40E Esc/mixers there is an option to view and download the wiring and setup datasheets in pdf format.

There is provision for connecting a third motor.

https://www.componentshop.co.uk/action-electronics.html

Colin

[tonyH]

Hi Colin, It looks as if the P40 could be the best option out of the 3 (2 Action and the Mk2 from Forge). The only niggle, being one that John's suggestion of a switch would knock on the head, is the possible narrowness of the "dead" band on the centre motor. Knowing, and oft exhibited at Mayhem weekend, of my twitchy trigger finger it could be a wise move Cheers, Tony