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Author Topic: Smitt Nederland and towing  (Read 6266 times)

ACTion

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Smitt Nederland and towing
« on: March 23, 2011, 03:30:36 PM »

We have a customer who has a Smitt Nederland from the Billings kit. He has two 2.5:1 MFA Torpedo motors fitted and is running them on 12v. The problem he is encountering is that there is a definite delay between applying full reverse from full ahead and the model responding. At first he thought it might be the radio or the speed controller (a P94) but we have eliminated those on the basis of bench tests. I believe that the props are not either large enough or perhaps of the right shape for the Korts to provide an instant response i.e. to stop the model and reverse its direction as quickly as he requires.
I've suggested he might first look at fitting Prop Shop Kort nozzle props instead of the brass ones he has on at present, but I'd be grateful for any help which you blokes might have based on your experience and which I can pass on to him. He doesn't have an Internet connection - BT's fault, he says!
Dave M @ ACTion
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DickyD

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Re: Smitt Nederland and towing
« Reply #1 on: March 23, 2011, 03:46:20 PM »

We have a customer who has a Smitt Nederland from the Billings kit. He has two 2.5:1 MFA Torpedo motors fitted and is running them on 12v. The problem he is encountering is that there is a definite delay between applying full reverse from full ahead and the model responding. At first he thought it might be the radio or the speed controller (a P94) but we have eliminated those on the basis of bench tests. I believe that the props are not either large enough or perhaps of the right shape for the Korts to provide an instant response i.e. to stop the model and reverse its direction as quickly as he requires.
I've suggested he might first look at fitting Prop Shop Kort nozzle props instead of the brass ones he has on at present, but I'd be grateful for any help which you blokes might have based on your experience and which I can pass on to him. He doesn't have an Internet connection - BT's fault, he says!
Dave M @ ACTion
Hi Dave, aren't the 2.5:1 MFA Torpedo motors supposed to run better on 6V ?

I thought you used the 6:1 MFA Torpedo motors on 12V.

Still what do I know, now shoot me down in flames. {:-{
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Marks Model Bits

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Re: Smitt Nederland and towing
« Reply #2 on: March 23, 2011, 03:50:03 PM »

I think Dicky has hit the nail on the head....... 6300rpm on 12 volts is a bit high and it is possible that the props are sucking in air and reducing thrust..

Mark.
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DickyD

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Re: Smitt Nederland and towing
« Reply #3 on: March 23, 2011, 03:55:40 PM »

You mean I might have got something right for a change.

Quit while I'm ahead, wheres me coat ? O0
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Roadrunner

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Re: Smitt Nederland and towing
« Reply #4 on: March 23, 2011, 04:08:49 PM »

err not to sound like a right ploker.. which happens a lot with me..

The boat is actually quite heavy and it will take a few moments for the boat to respond with a direction change just like the real ones!

Im running the same setup with my tug p94, twin mfs 2.5:1 on 12v and i have at least a 1-2 second delay before i see the model alter its direction, its not capitation as there is thrust occurring (im running 50mm korts with a 45mm prop) whats happening is the thrust countering its current direction to a stop/brake before it can move in its new direction.. if you run the model at a very slow speed and hit reverse i bet the models direction charge is far quicker then it would be at a higher rate of speed.


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DickyD

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Re: Smitt Nederland and towing
« Reply #5 on: March 23, 2011, 04:26:07 PM »

err not to sound like a right ploker.. which happens a lot with me..

The boat is actually quite heavy and it will take a few moments for the boat to respond with a direction change just like the real ones!

Im running the same setup with my tug p94, twin mfs 2.5:1 on 12v and i have at least a 1-2 second delay before i see the model alter its direction, its not capitation as there is thrust occurring (im running 50mm korts with a 45mm prop) whats happening is the thrust countering its current direction to a stop/brake before it can move in its new direction.. if you run the model at a very slow speed and hit reverse i bet the models direction charge is far quicker then it would be at a higher rate of speed.



My Al Khubar is using the same set up but on 6V and I have no problems at all. :-))
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ACTion

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Re: Smitt Nederland and towing
« Reply #6 on: March 23, 2011, 04:51:07 PM »

Thanks so far, chaps. I also feel that the 6:1 motors are better suited to 12v but as I know the square root of Sweet Fanny Adams about tug towing then I presumed that this combination was some part of that Black Art.
Keep it coming, please.
DM
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Re: Smitt Nederland and towing
« Reply #7 on: March 23, 2011, 05:16:27 PM »

The delay.
Is it a delay before the model responds (natural)
Or a delay before the motors go astern?
The ship?model has to use the astern engine order to brake before going astern
I would have thought 1 or two secs was scale speed/manoeuvering.
A delay before the motor responds is summat else

Ned




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ACTion

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Re: Smitt Nederland and towing
« Reply #8 on: March 23, 2011, 06:09:27 PM »

Is it a delay before the model responds (natural)
Or a delay before the motors go astern?
Ned

No - the response of the motors to the speed controller to the transmitter command is instant, but George says that the model doesn't respond straight away. Now please don't tell me it's only normal; logically that's correct, but the guy is insistent that for tug-towing it's not acceptable  (which is why I posted this originally).
Is it reasonable/usual for a tug to respond instantly in Tug Towing events - knowing that huge Korts and props are the norm for such models - or has this customer unreasonable expectations?
DM
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ZZ56

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Re: Smitt Nederland and towing
« Reply #9 on: March 23, 2011, 07:32:23 PM »

I'd advise him to fit the larger Kort propellers and if that still wont' work, there's nothing he can do except get a new boat for towing.
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craftysod

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Re: Smitt Nederland and towing
« Reply #10 on: March 23, 2011, 07:39:37 PM »

As you already mentioned Dave,
Is he using kort props or standard round edged ones,makes a lot of difference.
Mark
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John W E

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Re: Smitt Nederland and towing
« Reply #11 on: March 23, 2011, 07:50:37 PM »

Hi there
I have a few models which I have built I have never though had one which is capable of going from full-ahead to full-astern instantly.  There has always been a delay as the propeller goes into reverse it breaks the model stopping it, and then taking it into reverse.   Apparently, models tugs are one of the worst for not responding instantly, because of the nature of the vessel needing weight to help with the towing for the momentum.   Sitting thinking about it; two models which I have been able to get from full ahead to reverse are the Boston Blenheim and the HMS Leeds Castle.  These have the MFA x 2-1 belt drive gear boxes in them.   But this is not what makes them go into instant reverse. The trick is you have to be distracted momentarily and drive them straight into a concrete bank side of the pond.   This puts them in instant reverse but alters the bow somewhat. :embarrassed:

aye

john
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unicorn

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Re: Smitt Nederland and towing
« Reply #12 on: March 23, 2011, 08:11:01 PM »

 :-) :-) :-) :-)
                 korts are designed for extra thrust when going ahead and lose a substantial amount of thrust when going astern.
           

                                   
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towtug

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Re: Smitt Nederland and towing
« Reply #13 on: March 23, 2011, 08:20:27 PM »

No - the response of the motors to the speed controller to the transmitter command is instant, but George says that the model doesn't respond straight away. Now please don't tell me it's only normal; logically that's correct, but the guy is insistent that for tug-towing it's not acceptable  (which is why I posted this originally).
Is it reasonable/usual for a tug to respond instantly in Tug Towing events - knowing that huge Korts and props are the norm for such models - or has this customer unreasonable expectations?
DM
If the customer is controlling the stern tug in a towing team and the bow tug says apply power does he expect the tow to stop instantly? If the tow has inertia it will take awhile to stop, a full size ship can take up to five miles at full astern. If his tug has no inertia it has insufficient weight to be a tug of use to a towing team.
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Shipmate60

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Re: Smitt Nederland and towing
« Reply #14 on: March 23, 2011, 08:27:10 PM »

This is one of the problems with Tug Towing now.
Some want instant response from their model which would take 100,000 Kw per shaft on a real harbour tug.
The Smitt Nederland is quite a heavy model and will always take some time to stop then reverse.
Unless it is severely overpowered of course.

Bob
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Re: Smitt Nederland and towing
« Reply #15 on: March 23, 2011, 08:55:31 PM »

Try putting your car into reverse going foreward. Their is whats called inertia.Personally ive never seen any tug at speed reverse straight away. Still live and learn. Possibly he should be asking the modellers whose boats perform how he likes.To find out there set ups. Last thing have you seen the fire work display inside a motor
running foreward and put into full reverse without time to stop? John.
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poll

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Re: Smitt Nederland and towing
« Reply #16 on: March 23, 2011, 10:49:28 PM »

Hi Dave  We have a guy at our club with a smit tug when he built it what was in the box went on the tug, so the fixed nozzles, props, and becker rudders are standard fitting, he fitted belt drives. he do's not have any probs been the stern boat, all he do's is put a little something on the stern of the tug to stop it lifting when going a stern. Get him to come up to Balne Moor m.b.c. to one of our towing events.

Regards

John.
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brianB6

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Re: Smitt Nederland and towing
« Reply #17 on: March 24, 2011, 03:04:46 AM »

Surely it's the anticipation of what manoeuvre will be required next that makes for a good tug captain.
Practice, practice, practice.
and then more practice.   <:(
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Roadrunner

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Re: Smitt Nederland and towing
« Reply #18 on: March 24, 2011, 10:22:11 AM »

think your guy needs to go back to tug driving school ... its all anticipation of the next move and tug tower will plan there tow and know when to start braking and reversing. its all part of the challenge, tugs do not go instantly forwards then reverse at the flip of a switch its near enough impossible.

I've been tug towing for quite a while and spoken to several men who have worked on tugs, and have been told the model in is far more reactive then a real one given its scale and thrust ability's. you have to remember every model is different and will react differently this is all part of towing, plan your tow, and know your models capability's.

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poll

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Re: Smitt Nederland and towing
« Reply #19 on: March 24, 2011, 07:52:51 PM »

FLJ   Sorted :-))

John
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ACTion

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Re: Smitt Nederland and towing
« Reply #20 on: March 24, 2011, 11:05:59 PM »

FLJ   Sorted :-))
John

Many thanks, John.
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Geoff Cropper

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Re: Smitt Nederland and towing
« Reply #21 on: May 23, 2011, 10:42:55 PM »

        Tugs are designed to push with the bow and pull from the stern aren't they ?    why else are props shaped to give maximum thrust going ahead.        Not counting schottle or variable pitch props. of course.         I've never seen a stern tug pulling from the bow with the engine going full astern, what a gross waste of power, not to mention pulling the shaft straight out of the tube.           The tug with the most power always goes on the stern,    stern to stern with the towed vessel to act as a brake.            It seems there's still a lot to be learned about ship handling (tug towing)               Happy towing.           Geoff.
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meechingman

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Re: Smitt Nederland and towing
« Reply #22 on: May 23, 2011, 10:51:40 PM »

I've never seen a stern tug pulling from the bow with the engine going full astern
I have, plenty of times. Been on board and done it, too, with some very experienced tuggies, including my father! Never needed full astern, though. That anticpation of what's going to happen and the experience of bow and stern tug skippers saw to that. Depends on the situation, I guess, as I've also done it stern to stern.
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AndrewB

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Re: Smitt Nederland and towing
« Reply #23 on: May 24, 2011, 01:18:15 AM »

Interesting thread.
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tugmad

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Re: Smitt Nederland and towing
« Reply #24 on: May 24, 2011, 08:45:55 AM »

        Tugs are designed to push with the bow and pull from the stern aren't they ?    why else are props shaped to give maximum thrust going ahead.        Not counting schottle or variable pitch props. of course.         I've never seen a stern tug pulling from the bow with the engine going full astern, what a gross waste of power, not to mention pulling the shaft straight out of the tube.           The tug with the most power always goes on the stern,    stern to stern with the towed vessel to act as a brake.            It seems there's still a lot to be learned about ship handling (tug towing)               Happy towing.           Geoff.
Well said geoff  we never towed head to the stern of the towed vessell with the stern tug (conventional tugs Not Voith or azimuthing that is a different thing altogether)
it was always the stern tug Dragging with a really good gob rope that way stopping power is applied with the tug going ahead with full power available if required..  geo
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