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Bow Thruster advice please.

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Terry Plumridge28/04/2020 12:37:51
86 forum posts
8 photos

My current build, a paddle ship, has a Length of 94cm, Beam 17cm, width across the Sponsons 33cm, and an all up weight of 5kg. It is a bit unresponsive to the rudder, and struggles against even a small sidewind. This before it even has a superstructure. I am going to fit a Raboesch bow thruster. I would welcome any advice regarding the size of Bow Thruster to use, don't want to over-engineer it!! Power for this boat is 6 volt.

Cheers, Terry.

Chris E28/04/2020 14:37:48
105 forum posts

My experience is with models with lots of directional stability, props rather than paddles and home made bow thrusters rather than Raboesch. What that has told me is that, for my models, bow thrusters are brilliant when the model is stopped or nearly stopped but rapidly become less effective as speed builds. They make very poor rudders.

Ray Wood 228/04/2020 15:21:38
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1991 forum posts
709 photos

Hi Terry,

I have no experience with paddle boats yet , but individual paddle drives to each side ?or a bigger rudder would seem a couple of answers ?

Regards Ray

Tim Rowe28/04/2020 16:40:48
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405 forum posts
440 photos

Echo Chris E 1

It's the same on full size boats and ships. Even dead slow will render a bow thruster ineffective. You will need another solution like Ray says and maybe even a bow rudder.

Tim R

ashley needham28/04/2020 17:32:31
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6599 forum posts
150 photos

I am with the guys on this. You are not using scale wind, and therefore unless a model is exceptionally heavy or deep, then a bit / some / a lot of drift is what you get!

I deliberately made my various battleships and so on with extra deep hulls for exactly this issue.

We have collectively a fair few models on the pond that don't like the wind.

Ashley

Paul T28/04/2020 17:52:22
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7146 forum posts
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Terry

You could copy the Brunel solution and use paddle wheels with a propeller. The prop is hidden underwater and provides controllable thrust over the rudder.

Paul

Colin Bishop28/04/2020 18:20:15
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4522 forum posts
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The practical issue is that a paddle vessel rudder will not 'bite' until the model is moving at an appreciable speed as there is no propwash over it. When Waverley visits Portsmouth facing up harbour a tug is needed to push the bow round when she leaves. Even at cruising speed paddlers are not known for their steering agility.

As the others have said, a bow thruster wlll only work effectively if the vessel is pretty much stationary. This applies to both full size ships and models. I have the smallest Raboesch thruster fitted to my 3 ft Revell Queen Mary 2 model and it does give a reasonable thrust when the model is stopped, more one way than the other though. There is no reason not to fit a thruster to assist low speed or static manoeuvering but I'd go for at least the next size up, in fact the biggest that will fit in the hull would be good.

As far as general steering is concerned, it has long been recognised that in models there is little alternative but to break away from full size practice and operate the paddles independently - a mixer would be handy to smooth out the effects of slowing/reversing one side and speeding up the other. Otherwise you will have a turning circle resembling the orbit of the moon!

As an aside and going back to full size practice, Waverley has semi demolished a number of piers in her time from inadequate steering response, while back in the 1960s as a lad, my family used to holiday on the Isle of Wight which was still served by a couple of paddlers in those days. On one occasion when berthing at Ryde Pierhead the bow came smoothly alongside but the paddle box slammed into the pier timbers. The ship stopped dead but the passengers standing waiting to disembark didn't...

On Lake Lucerne they still run regular paddle steamer services which are wonderful and some years ago we spent quite a bit of time on them and I was able to observe the docking technique. The piers protrude from the shore so the ship can accurately line up its approach so it comes in at 90 degrees to the pier parallel to the bank at some speed (being on a mostly calm lake helps). As the ship comes alongside the pier the engines are put into reverse and the ship stops almost immediately. Depending on how well the gangway is lined up (and they get plenty of practice), a couple of strokes of the paddles moves the ship a few feet fore or aft and lines thrown ashore are used to draw her in against the pier. Very impressive to watch.

Colin

 

 

Edited By Colin Bishop on 28/04/2020 18:21:33

Terry Plumridge29/04/2020 17:20:37
86 forum posts
8 photos

Thank you for your replies, I am going to take the simpler option first, an oversize rudder, and see what happens.

Colin, referring to your remarks regarding Waverley and a tug, maybe I should have my Joffre ready and waiting in the water when I sail the paddler !!

Paul, I am wondering did Brunel anticipate steering problems and incorporate a propellor into his initial design. Or was a propellor and drive retro fitted to overcome a steering problem?

Cheers, Terry.

John W E29/04/2020 18:55:56
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263 forum posts
257 photos

hi there

with regard to adding a bow and stern thruster to help the model to turn whilst under way - is not very successful - as has already been stated. Unless, you have the bow thrusters connected in with variable independent propeller control. On the other hand, independent paddle wheels give you a greater manoeuvre-ability when under way - when stationary you can literally spin the vessel on the spot by putting one paddle wheel forward and one reverse. You don't need a mixer in your model, independent stick control on your transmitter will do the job.What hasnt been mentioned is 

 that a lot of paddle steamers have what is known as a bow rudder to help them turn; I would suggest you try independent paddles first off. Also slightly increase the weight of your model so that it sits deeper in the water. You will find that some 'paddlers tend to dig in' i.e. tend to lean as the paddle pulls the water back. To counteract this, if you fancy going to the expense of making 'feathering' paddles - anyway - if I can find out to put a video on here without going through the bother of YouTube - I do have one of the Forceful, which I built - going through its paces .

John58384380_2201674793259590_3698850844909764608_n.jpg

Edited By John W E on 29/04/2020 18:57:46

Edited By John W E on 29/04/2020 18:59:21

Terry Plumridge29/04/2020 19:55:23
86 forum posts
8 photos

Hi John, thank you for the information. Unfortunately I am too far into this build, and too deep into my budget, to make any major modifications to the boat. But I am learning as I go and if I attempt a second paddler I will be much better informed. Your boat looks very impressive.

Cheers, Terry.

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