Dual Rudders

[Stephen Paterson 2Participant @stephenpaterson2]

I have/am building an Elco 80ft PT boat, The original as you will know had three props and rudders. I have opted for twin 540 motors and rudders. What would be my best option for the linkages to rudders? L shape along hull and straight arm across it or sleeved wires similar to the old style bicycle brake cables?

Just concerned with even movement on both rudders.

Out of curiosity had I went for three motors I surmise outer two rotating ccw to each other and middle one would it matter direction? Then do I want to have either outer cutting rpm in relation to turn which would allow the centre and outer to turn in tighter… result being turn one way tighter than other which I'm sure could be 'dialled' out with speed controller programming? Or have I overthought this? 😂🙈

[Stephen Paterson 2Participant @stephenpaterson2]

[ashley needhamParticipant @ashleyneedham69188]

🏆Cor, those 540s are going to have their work cut out propelling an 80ft boat!

Stephen. Yes, over thinking is the order of the day! It’s best if the props are handed as this will help straight line stability. BUT this is a model, and having both props going one way is easily countered by a bit of rudder bias. Reversing is also helped by handed props. If you were going in for steerage competitions, then it might be a different matter, but for zooming round the pond is the extra expense and faff worth it? Extra turning ability can be had by…having more rudder angle! Or making the rudders bigger, both frowned upon by some but again, it’s a model and the loss of efficiency won’t be noticed.

As far as rudder operation, if the servo is not too far away, I use garden mild steel wire which is stiff enough for the job. Likewise I like to use the clamp-on nylon tillers as they are easy to adjust. For a longer servo-rudder run, garden wire can be supported by some plastic tube, or use an aircraft control snake, and this has the advantage of ready made fittings for the ends.

No doubt someone will post a picture of their rudder setup!

Ashley

[John W EParticipant @johnwe]

hi there

Heres a pic of the RAF Air Sea Rescue Launch (63 ft one triple rudder) this gives equal amounts of movements on the rudders and is a fairly robus setup. If I remember rightly on this particular model the 2 outer props rotated inboard towards each other as looking from the stern. The centre prop turned anti clockwise if I remember rightly. If you want to be pedantic some of the real Coastal Forces Vessels (PT boats) have all their props turning the same direction due to the fact that they were unable to obtain or manufacture in time, the reverse gear boxes.

John

[Stephen Paterson 2Participant @stephenpaterson2]

Thank you Ashley! I did actually order two CW props in error which I will have on for now and later on will swap

for a ccw. I did make the motor connections to

allow for a swap later.

And thank you John. I do wish I had went for the triple prop and rudder now. 🙈

The Raf launch is many times neater than the inside of my PT offering. 😂🙈

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