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[Umi_Ryuzuki]

I just ran across this proposal.

The RAve tug with the VS drives at each end, combined with the 360° Carousel towing ring.

http://www.towingline.com/archives/2331

Perhaps it is time for Poll/John to update and build a new tug. 

[poll]

  Thanks Amee.
  You are so good to me, yes you are right it is time to put the old girl in dry dock, it's just purchasing a hull that would lend it's self to
  VS, Norton cross is close but stern end would need a little surgery & a little more beam, come on guys & gals could do with a little
  help here, or as anyone got a hull for sale?

    John

[Brian60]

Well the idea of twin v/s are not new but the towing ring certainly is. Apart from the novelty factor I wonder how it would cope in a real life situation? There cannot be much in the way of anchoring points given that it must run on some sort of an inverted castor system under the rails. Plenty of weak points to cause problems.

[Umi_Ryuzuki]

The carousel "technology" has been around for a while, but few have adopted it for use.
Seems like I recall research dating it back to 1998?



I know of at least three models, but John's seems to be the only tug out there working.
The two others I think have visited Balne Moor, and the original RC and manned models were for research.


http://www.imcgroup.nl/news/CCT.html
.
  It might also be known as the Mampaey Dynamic Oval Towing system. 
https://www.youtube.com/watch?v=0V3peYq53XM

Macduff installation
https://www.youtube.com/watch?v=YCC7fF5Z8mU.
..


The RAve Carousel is a new proposal, and the first major adoption of the technology that I have seen.

[mrturbo553]

Brian , have a butchers at these
http://youtu.be/PZ87AqoG2gk


Aid 
And Polls tug
http://youtu.be/kLGUbzPN5HM

[Xtian29]

Hello


Have you seen this video Aimée ?


https://www.youtube.com/watch?v=eGPWbxWrIlA


On my side I have made a try with two Graupner prop on a easy made foam hull and it's not working very well.   


The main reason is because the Graupner Voith are controlled from a vertical stick by to links then it's impossible to move this stick from neutral to 0° or 180°  as the stick is moving on an ark of travel because of the second link.  Then the vertical stick is going to 5° or 175°.


With two Voith side by side it's not a real problem as one Voith is going 5° and the other one to 355° -  the result for the pair is 0°

When the two Voith are along the center line it's not easy to drive the boat straight ahead as you are never sure the generated flow is directed like you want. [size=78%]  [/size]


Twirlingwith this boat is ok but going where you want to go is another challenge.


In fact there is a solution to avoid this problem by using a X-Y plate on top of the prop, like that the movement of one link is not interfered by the other link.




Anyway there is another thing with two Voith on center line as the boat is turning well to one direction and slowly + drifting to the other one as there is gyroscopic effects similar to the ones when you drive a monoVoith.   Then driving a boat with two Voith along the center is like driving a double monoVoith and not a double Voith : just boring


I will made some other "sea trails" to better understand all effects and to make a video then I'm really thinking to convert this hull to a side by side Voith





About the Carrousel, Yep it's funny to sail the Rave with it, but sometime these Voith problem (arc travel for the stick) and gyroscopic effects are really surprizing and even jeopardy.   


I have to try this carrousel with better prop conditions !


Then I will continue to play well with my regular side by side Voith  (home made Voith prop)





Xtian

[Umi_Ryuzuki]

Thanks Xtian,


I had not seen that video. I knew that they had some carousel tugs for trials at Port Revel, but
I did not know that there had already been a RAve Carousel on the water. I will have to post
that video to FB, and see if someone claims ownership of that model.    I did post the
RAve photo to a friend and said, "...just to make running a tug more difficult." 


It will be interesting to know your test results from your experiments.
I know you were also interested in the EDDY tug also.
 

[Xtian29]

I'm still interrested with the 2 prop along the center line : Voith or azimuthal. 


As I have two Graupner Voith on shelf I tried the Rave.  But I'm really surprized about these gyroscopic effects - If there are solutions for the ark travel of the Voith control stick I'm thinking (maybe a mistake) there is no solution to avoid this gyroscopic effects and by this way I'm affraid to drive a tug that turn better in one direction than the other and even sometime fail to turn and only drift sideway.  I tried my rave as stern drive (Carrousel) and it works well on indirect mode, not so good when towing on direct and it's just a buls... to sail and maneuver alone.


So now I'm still "dreaming" to test the Eddy concept on RC   ... Normaly (I hope) there is no gyroscopic effects like that, maybe another challenge with stray flow during transit from one angle to another one. 


To be continued ...  Anyway prior that I will try to finish my regular Voith and my Invader Class  [size=78%] [/size]

[Brian60]

Brian , have a butchers at these
http://youtu.be/PZ87AqoG2gk

Yep Aide that certainly looks safe - broadside on with the deck underwater and trying to apply a towing force! That is exactly what I was getting at in my post. You have a small craft trying to overcome the inertial momentum of a big ship, broadside on.It's only got one outcome and that ends with the small craft underwater, At least towing from the front or rear of the tug gives you a greater leverage over the fulcrum of the towing hook.

[Umi_Ryuzuki]

I believe the point of the Carousel system is that the tow point is off set from
the center of the tug, so that it prevents girting or overturning of the tug.
Especially when preforming "Indirect" towing maneuvers which increases a
tugs bollard pull, or braking force by 150% using the drag of the tug boat's hull, but
also puts the tug at the higher risk of overturning.


While John's carousel tug looks about to be dragged under, the tow line is actually
pulling up on the tug, preventing it from over turning, and John can use the entire
deck of his model to create maximum drag, and slow the ship in tow, and keep the
lead tug from being over run and over turned.


Below, the stern tug, has allowed the tow to over run the lead tug.

[Brian60]

A good theory they have come up with Umi. But that video clearly shows the carousel tug heeled over with water across the deck while trying to apply a towing force broadside on. Either the skipper eases the tow or his ship goes under. in a confined river this could mean the larger ship out of control and hitting something.

[mrturbo553]

Brian , I was trying to explain they don't heel over as much in "indirect " mode due to the winch being on the outside of the hull
Normal bow mounted winch  on the other hand.....enjoy    bottom nipping
http://youtu.be/8l0Oja_rm0s
Aid

[Umi_Ryuzuki]

You are also looking at tests designed to push the Carousel systems to their extreme.
The crew treat the water over the bulwarks as "just another day at the office.". 
https://www.youtube.com/watch?v=3QecHdByM20

[Xtian29]

The "deck washing" is spectacular but it's not effectiveness and in fact it's the opposite !


Loosing flottaison surface because of this water on deck is bad for stabitity not only because of list angle, weight on deck and capsize risk - just because of smaller flottaison surface.  It's also dangerous, a door not well closed and it's the end of the story - Then having a angle of list degrease the indirect mode working surfaces of the hull and sked (paravane effect).


A well calculated escort tug like the Velox and sisters or Svitzer Lindsway have no water on deck even during high speed escort duty. One of the reasons is the bulge on each side of the hull. 


The RC springer hull with carrousel arrangement is funny to play but already at low convoy speed there is deck washing and lower acting surface for paravane effect, a conventional hull would be more appropriate and effective but less spectacular !


Xtian

[BarryM]

From the 'Marine Professional', periodical of the Institute of Marine Engineering, Science and Technology.

Quote:
Towage and salvage specialist Multraship ordered two Carrousel Rave Tugs from Damen Shipyards Group. Commissioned through its subsidiary Novatug, these new vessels will provide more power as well as reducing the risk of capsizing under a tow load.

Construction is underway at the German shipyard Theodor Buschmann in Hamburg. The final outfitting will be done by Damen Maaskant Shipyards in Stellendam, The Netherlands and delivery is scheduled for early 2017.

The 32m-long vessels have a bollard pull of 70t. Propulsion consists of two Voith thruster units and two ABC main engines of 2,650kW operating at 1,000rpm. Free running speed is 14 knots at 5,300kW.

The Carrousel Tug’s lower operational costs, improved response and manoeuvrability and enhanced control over the tow are said to confer advantages over conventional tugs, for example by widening or even removing tidal and weather windows for certain ports.

Multraship director Leendert Muller said: “This new tug design, for the first time, eliminates what has always been the most significant threat to safety in towing – the risk of capsizing under a tow load. The benefits in terms of efficiency and flexibility, meanwhile, are also substantial.”
Unquote

BM

[Umi_Ryuzuki]

I would add, that John, like me, probably enjoys the reactions of other modelers when
the decks go awash, and the other modelers start freaking out. 


Found a couple photos from a Marine Expo.