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Author Topic: Control co-ordination and combinations.  (Read 3268 times)

meechingman

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Control co-ordination and combinations.
« on: May 03, 2010, 05:34:04 PM »

OK, My Smit Nederland now has a bow thruster and I'm off to the lake in a few days for trials.

With independent control of the twin screws and rudders, she can already turn on the spot, but my question is this. Has anyone posted details on the manoeuvres that can be carried out using screws, rudders and bow thruster in combination? I'm sure it won't take long to find out, but maybe someone already has and has the info.

For example, which combinations would make her crab sideways (if it's possible)?

Andy
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andywright

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Re: Control co-ordination and combinations.
« Reply #1 on: May 04, 2010, 07:52:44 AM »

Delete above ,Done, this is the correct way!!!!

To make your tug go side ways to st'b'd, rudder hard port, st'b'd engine  ahead, port engine astern and thrust to st'b'd, but the thruster has to be more powerful than the turning moment of the engines, if you try to use the opposite engines, it will make the bow accelerate too fast to st'b'd. A lot of fiddling, if you fitted a becker rudder, you could use one engine and the thruster to make the tug go side ways, and just a touch astern on the other engine to arrest any ahead movement. Its not easy, I used to do it 1:1 scale easily, but a model would be harder. Nowadays any full size tug capable of this manouvre would be joystick control, or a voith tug.
Andy

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Umi_Ryuzuki

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Re: Control co-ordination and combinations.
« Reply #2 on: May 04, 2010, 09:17:43 AM »

Here are a couple of diagrams for VS drives, and schottel drives.
While your tug is neither of these, the same thrust vectors can be created
using your propellers and rudders, and the addition of the bow thruster will make
the maneuvers a bit easier.

 :-)
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andywright

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Re: Control co-ordination and combinations.
« Reply #3 on: May 04, 2010, 08:50:29 PM »

They are a great way of showing it all ,magic. You do learn to think like that when skippering, trouble is joy sticks can make you lazy, you need them to go faulty occasionally to make you think again.

Andy
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meechingman

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Re: Control co-ordination and combinations.
« Reply #4 on: May 04, 2010, 10:55:48 PM »

Many thanks for all this.   :-)) I'll print out the diagrams for the trials.

I have waaaaay too much power for realism on the bow thrust so should be OK. The tug is fitted with twin Becker rudders, so that will help. It's just a question of remembering which way to push the sticks.

I also have no problems throwing a real twin-screw, twin rudder tug around in 'old school' fashion with telegraphs and a real proper BIG wheel, (haven't had a chance for a few years, though) but it's taken a while to get used to scaling things down for models. As with the real thing, 'gently does it' is the way to go. That's what my Dad taught me years ago.

Andy
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Ghost in the shell

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Re: Control co-ordination and combinations.
« Reply #5 on: May 05, 2010, 02:21:40 PM »

meech, if you go full left stick on the screws, to pirroette counter clockwise, thus walking the stern to the right, and go full RIGHT stick on the bow thruster, by juggling the thrust of the screws, i think you can make the boat move bodily to the right
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TugCowboy

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Re: Control co-ordination and combinations.
« Reply #6 on: May 13, 2010, 08:24:03 PM »

You thinking of entering her for the steering comps this year Andy?

Alex
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meechingman

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Re: Control co-ordination and combinations.
« Reply #7 on: May 13, 2010, 09:29:16 PM »

Hi Alex

Nice to hear from you.

Sadly, family health problems are still ongoing, so visits to the lake have been non-existent for around a year. However, I do intend taking Denton over next week for trials and, all being well, hope to take her to the scale regatta and to at least one of the steering comps.

Hope to meet up with you at one of them. How did your build go?

Andy
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TugCowboy

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Re: Control co-ordination and combinations.
« Reply #8 on: May 14, 2010, 08:25:58 AM »

Hi Andy,

MY build went brilliantly and a couple of weeks ago was in a finished state, then she got knocked onto the floor and is now laying with her back broken and superstructure shattered. A repair may be possible but it will take a very long time.

However it is my birthday next week and wonderful SWMBO may have sorted something for me so I hope to be on the lake lots over the summer!

Alex
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meechingman

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Re: Control co-ordination and combinations.
« Reply #9 on: May 30, 2010, 12:12:41 PM »

First trial of the bow thrust was a bit of a let-down. The thruster worked for all of 30 seconds then the paddle slipped off the shaft.  :((  Back home for a dab or two of epoxy!

Second trial went much better, though I discovered that I must replace the current ESC. It came with the tug and is probably one from a car - 100% power one way and about 50% the other.

Using thruster alone, the tug will turn more or less in her own length. OK, that's not new as using twin screws and Becker rudders, she turns on the spot anyway. However, it was interesting to see what could be done with the thruster in combination with screws and rudder. I couldn't get her to crab sideways but diagonal movement is possible. I think a bit of practice is required here!

Going astern with many models seems to be hit and miss, but I found that it was possible to go astern and correct any swings with a quick blast of the thruster.

When towing something heavy, or when acting as stern tug (towing over the stern), using the thruster is a useful way of swinging the tug's bow without changing the amount of pulling/braking force. OK, this could be done with rudder, but just a quick burst on the thrust produce the result quickly.

And of course, it's nice to apply a quick burst of thrust to move the bow away from the quay when leaving 'harbour', or as a gentle nudge alongside.

All in all, I'm well pleased. For relatively little outlay (approx 30 for the thruster, 5 for filler (tons left) and a few quid for sundries like wire and glue, it's added a new dimension to the tug. Well worth the money and time spent, iMHO.  :-))

Thanks to those who have supplied info and help in getting it installed.

Andy


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