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[hopeitfloats]

has anyone tried twin props rotating the same way. i know torque is the issue and counter rotating counteracts it but talking to an old x mariner a while back he was pretty sure the ship he worked on had props that turned the same direction.

[dougal99]

I have this arrangement of a small model frigate, about 20 inches, as I couldn't find handed props at the size and price required.  :-\Doesn't give me a problem.

Doug

[hopeitfloats]

so you dont need to add rudder to counteract  the torque. i am just wondering if it would affect a larger model. maybe rotation isnt as important as i have been lead to believe

[dougal99]

I'm using 30mm props with two rudders and quite small motors. I don't notice any particular turning moment. The hull is a carved bread and butter construction and with my skills I can't guarantee it's symmetrical so I don't get upset with a slight turn over a long straight run.

However, bigger props and more powerful motors may give a different outcome.

Cheers

Doug

[Martin (Admin)]

I think tug skippers would beg to differ.... but they do spend a lot of time going sideways......  

[grantl]

I'll be doing some practicl research on this soon. I have done a spinger style tug thing with inappropriate motors (2 speed 400s), a pair of right handed props and no rudders. I'll report how it goes in the water in about a months time.

Grant.

[hopeitfloats]

 i was just about to start building the drive for mine now i might just have to hold off for a bit and get a few more opinions first. same rotation would simplify it even more.

[DickyD]

The 63 FOOT RAF AIR SEA RESCUE LAUNCH that John bluebird is building in his masterclass had 3 props all turning the same way. Another bit of useless information.

[Bryan Young]

Beginning with a single screw. Assume a right-handed prop (clockwise when viewed from aft). Transverse thrust from the prop makes berthig port side to the jetty much easier than going starboard side to. With contra rotating props the transverse thrust effect is exactly the same if one prop is stopped, i.e. use the starboard prop when going port side to, and the port one when going starboard side to. In normal sailing I guess that a small correction with the rudder(s) will keep the ship going straight, but berthing will be hampered.

[hopeitfloats]

do you think that without being able to stop one prop it would cause major berthing problems or just an extra tweak on the controls to bring it in.

[Stavros]

Never had a problem with a MTB that I had with both props running the same way


Stavros

[John W E]

hi there hopeitfloats

What everyone tends to forget is; a model will only perform as good as the person who controls it; this has been proven many times during Scale Sail Competitions   when a skipper, who does know his model well, whether it be twin or single propeller.  He can make that model perform just as well, if not better, than any multi-propellered model with bow thrusters - in fact all the gizmos in the whole world    if the truth were to be known this was why the well respected late Mr Craig Talbot (creator of the ACTion Mixer); put the dwell function at the neutral position.  This was so the skippers could just flick the rudder servo to operate the rudders, just to move the stern in either direction without the propellers engaging.

So the truth will answer my friend - as the model is just as good as you in performance  :)

aye
john e
bluebird

[DickyD]

Very good, back to bed John.

[John W E]

Well Dicky,

The above statement of mine - comes from experience gained whilst organising, planning and running scale sale championships in the North East. 

When one has had the experience of this; one begins to realise this that it does not matter how difficult you design a course for the competitors to sail their models' around - there are always one or two who can sail around and complete the course with very few faults.

These people tend to be very skilled at operating their models and the majority of the time when I have been involved - these people have ran even the basic model i.e. single screw with no fancy Kort nozzles or bow thrusters.

The most difficult part is trying to explain to other competitors why these people have managed to negotiate the course with the minimum of faults; and others, who do have all the other gizmos - singing and dancing - cannot get round the course without accumulating faults.

In other words Dicky they rely too heavily on the gadgets etc., in their models - instead of polishing their own skills.

aye
john e
bluebird

[AlanP]

Guess thats told you Richard   

Alan

[catengineman]

I am a Richard and I would agree with Bluebird

This said I have one of them all singing all dancing tugs but I can switch it to pretend that it is a not so singing tug
I acctually do this to berth rather than use the B/thrust and ASD to "walk the tug alongside" much more fun!

I hope to have a VS tug soon  and I am thinking on the lines of a small craft as an addition. (just need the wife to OK all my idea's) :(

[meechingman]

I'm with Bluebird as well and I'm happy to sit for a few hours on a dead calm day just trying to learn how best to manouevre my fleet. They're all different and I still have lots to learn, even though I was taught how to drive twin and single screw real tugs by my Dad.

It's the same thing in real life and I've come across some brilliant ship handlers, and just one or two inept characters who were either heavy-handed or just plain 'lost' at times.

Andy

[Bryan Young]

do you think that without being able to stop one prop it would cause major berthing problems or just an extra tweak on the controls to bring it in.

Try to stop one prop.

[hopeitfloats]

i am planning (subject to change of course) to run both off one motor so stopping one not really practical. not impossible but trying to keep drive as simple as i can

[catengineman]

Hi,
  From what I read you are going to have twin screws working at the same time so in my opinion your vessel should act in the same manor as a single screw
Berthing would be as if it was a single IE. rudder/prop control.
If both props turn the same direction then there may be some *walk* which you will get used to very quickly (IMHO)

R,

[hopeitfloats]

thanks for all your views. time to start building i think.  one motor. two props spinning the same way and maybe a bit of fiddling at the controls when its running. i can live with that.

[farrow]

The whole idea with standard twin screw inward turning screws is to get max maneuverability due to paddle wheel affect, when maneuvering the vessel. Also when going ahead on both engines in reasonable sea conditions the wheel should be amidships, this will give max drive efficiency safe fuel at best speed.

[Martin (Admin)]

Found this on YouTube....
http://www.youtube.com/watch?v=LhtB5fRDSV4&feature=related

[Martin (Admin)]

And this..... http://uk.youtube.com/watch?v=2ZPf7wNTaGY

[andyn]

My Llanberis Straight Running Competition Winning Perkasa has two 40mm props on 545 motors going the same way

Did I mention it won the straight running competition? It won it you see.

Andy