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Author Topic: DHULIA/MOORCOCK TUG  (Read 5283 times)

FIRPARK

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DHULIA/MOORCOCK TUG
« on: January 24, 2010, 11:47:56 PM »

Can anyone please help with information on the Thames tug Moorcock or sister ship Dhullia built at Hessle on the Humber 1950's. I am well on with the rebuilding of the steel frame and steel hull of 1:24 scale tug. I have the Nexus Oliver Smith drawings, and just the March 1980 article Nova in Model Boat, but would like info. on deck fittings-fire hydrants-vent pipes etc. ---bridge and chart room fittings and any help that you can offer. I hope to power it with a 12 volt heater motor, but will this be too small? The rudder is 6inX3in.  will I need to use a slave motor?
As you can guess--I am new to this game, and any help will be appreciated.
Firpark
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derekwarner

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Re: DHULIA/MOORCOCK TUG
« Reply #1 on: January 25, 2010, 03:06:15 AM »

Firpark.........without knowing or understanding the the mass or size of the scale vessel [1:24 of what?  :D] a rudder of 18 square inches surface area sounds a large number

However it also depends on the rudder design.....a 1950's style may have been an oval paddle design & totally unbalanced ....ie., no leading surface FWD if the vertical pintal  axis  >>:-(........a 1950's rudder could have also have been rectangular with rounded corners & partially balanced  {-)

Your thought of.....  "will I need to use a slave motor?" is an excellent idea..........if space & mass permits....a 12 V motor vehicle windscreen wiper motor would provide masses of slow speed torque with the worm & worm wheel output which could simply be connected to the rudder quadrant below deck & standard servo control

An alternate to this could be a heavy duty hi-torque yachting type winch servo....how this may need additional engineering for installation

There a number of +'s and -'s with both concepts......

Are you actually building the hull in steel?.....a few photographs would be appreciated........Derek





Here is a posting from yesterday in another thread ......Hi Toesupwa,

The pivot point must be counted as the last point the the tow rope is in contact with the tugs structure and as you correctly point our your towing point (Staple) is aft of the units.  If you look at the configuration of any single, twin or ASD propelled tug you will find that the towing point is just aft of midships, mush further forward that on your vessel.

The easiest way to explain i feel is in terms of vessel rudders.  These have developed over the years and there are three basic types which have been used over the past century or so;

Fully Balanced.  This is when the rudder stock is almost in the centre of the rudder blade allowing equal forces to act on the area ahead of the pivot point and equally on the area aft of the pivot point.  The advantage of this is that you require a very small torque to turn the rudder, but the disadvantage is directional instability as the rudder will have a tendency to wander due to the equal forces being appled as it passes through the water.  In tug terms this would be great for a harbour tug with her towing point midships as she would be very maneuverable and would be able to pivot on her tow line with minimum rudder appled.  This direction instability always gives the danger or turning the tug over (where the tow rope comes across the beam at right angles almost midships at the towing point) and this is why a gog or gob rope is sometimes used to transfer the towing point further aft.

Semi Balanced.   This is where the rudder stock is approximately 1/3 back from the leading edge of the rudder blade.  This increases the turning torque required but gives much better direction stability.  This is the type of rudder used in all merchant vessels with a conventional propulsion package built today.  In tug terms this is what most single/twin/ASD tugs have.  This gives good maneuverability for use in harbours but still excellent direction stability for towing at sea (i.e. in a straight line).

Non Balanced.  This is where the rudder stock is located right on the leading edge of the rudder, whilst giving the best directional stability it gives the worst turning performance and requires the most torque to turn the rudder blade.  This is the category that your tug falls into.  When you are towing over aft your tug will not pivot around the towing point at all.  The entire tug will have to force the complete length of her hull through the water to change direction which will lead to using all engine power to position your tug and not the tow, this will lead to total loss of control of the tow.

You have made such a nice job of her top sides and she looks like she will be a cracking model, i would just suggest that you think about the option of placing the towing winch on the bow and towing through the lead on the bow as most ASD tugs to to avoid disappointment with the performance of your finished model.

Cheers.

Tugchief.
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Derek Warner

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Illawarra Live Steamers Co-op
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tigertiger

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Re: DHULIA/MOORCOCK TUG
« Reply #2 on: January 25, 2010, 04:44:10 AM »


An alternate to this could be a heavy duty hi-torque yachting type winch servo....how this may need additional engineering for installation


Hi Derek
Winch servo can be taken as either sail arm servo or sail drum winch servo, unfortunately %)

If in your you were referring to the latter, there is an alternative.
There are several, what are called, 1/4 scale servos on the market. These are an arm type servo with a lot of torque, for example the Hitec HS815BB has about 23kg/cm torque on 6v. Should be plenty powerful enough to turn the rudder in question, using pushrods.  :-))
All you would need is to step down the voltage to 6v or run it off a separate power supply.
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derekwarner

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Re: DHULIA/MOORCOCK TUG
« Reply #3 on: January 25, 2010, 05:24:10 AM »

Thanks TT.........if our newer member responds & questions.....I am sure one of our world wide member base will respond ......& help ....... O0 ....Derek
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Derek Warner

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tigertiger

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Re: DHULIA/MOORCOCK TUG
« Reply #4 on: January 25, 2010, 05:48:16 AM »

Another advantage of the 1/4 scale servos is that they are much cheaper than sail arm servos.
They are bulkier as well, but space will not be an issue in this model I think.

And as you say Derek, with so many tuggies on this forum, there is a wealth of knowledge to tap into.

BTW
Welcome aboard Firpark
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Re: DHULIA/MOORCOCK TUG
« Reply #5 on: January 25, 2010, 01:09:28 PM »

It may be of help to you to know that the original data for this model was published in "Model Engineer" in the form of a series of articles spanning many issues.
The Nexus plan that you have is, in fact, derived from these articles.
I have a number of photocopies (some very poor quality) of articles taken from the original magazines. They form a very good source of data for building the ship.
Sorry that I cannot quote the dates of publication at present as I am away from home at the moment.
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FIRPARK

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Re: DHULIA/MOORCOCK TUG
« Reply #6 on: January 26, 2010, 11:12:42 PM »

Another advantage of the 1/4 scale servos is that they are much cheaper than sail arm servos.
They are bulkier as well, but space will not be an issue in this model I think.

And as you say Derek, with so many tuggies on this forum, there is a wealth of knowledge to tap into.

BTW
Welcome aboard Firpark


Hi--Many thanks for your input, I will look into 1/4 scale servo's--never heard of them before. It has to move a big "barn Door" front hinged rudder over from one lock to the other, against the pull of the prop if on power astern. (if she ever gets to the water). I can't work the loading out,  will a servo do the job?
Thanks for your help
Dave
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derekwarner

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Re: DHULIA/MOORCOCK TUG
« Reply #7 on: January 27, 2010, 12:30:08 AM »

Dave asks ....."I can't work the loading out,  will a servo do the job?"


..........you would near need a degree in astro physics to convert the [vessel mass x speed x block coefficent x the sero radian divided by the servo torque  [in U nM per degree of movement] X [density of fresh water divided by the dead sea salinity scale] & finally divided by the square root of scale..... :o

In convict OZ we would consider an alternate form of calculation

Insert the vessel in the water.....attach a fish weight spring scale to the rudder extremity,,,,propell the vessel @ the desired speed, create a moment by rotating the rudder to the maxinium position & read the strain value created on the fish scale ...simple but true  O0...this is the actual load created & thus an easy calculation to the torque value required...... :-))

Compare this value with the servo manufacturers maximum torque output..........Derek  :D

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Derek Warner

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derekwarner

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Re: DHULIA/MOORCOCK TUG
« Reply #8 on: January 27, 2010, 07:15:54 AM »

Dave .....just thinking of the example servo offered by TT as ...... "the Hitec HS815BB has about 23kg/cm torque on 6v"

So....if we consider......your barn door rudder is 6" long.. or ~~~~~152 mm long.....100 divided by 152 = 0.66...so 23kg torque on the same 152 mm = 0.66 or 15Kg

What does mean?....... {-) %)...if your fish scales are of metric calibration & you get a resultant from my recommended test scenario of 15 kg or less...hey presto...the  Hitec HS815BB on 6v would be a good solution  O0 :embarrassed: ....Derek
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Derek Warner

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Illawarra Live Steamers Co-op
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www.ils.org.au

FIRPARK

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Re: DHULIA/MOORCOCK TUG
« Reply #9 on: January 27, 2010, 07:58:52 PM »

 Derek--
Thanks very much for the information, I will have a look at this Hitec HS
Many thanks
Dave

link=topic=22034.msg216592#msg216592 date=1264388775]
Firpark.........without knowing or understanding the the mass or size of the scale vessel [1:24 of what?  :D] a rudder of 18 square inches surface area sounds a large number

However it also depends on the rudder design.....a 1950's style may have been an oval paddle design & totally unbalanced ....ie., no leading surface FWD if the vertical pintal  axis  >>:-(........a 1950's rudder could have also have been rectangular with rounded corners & partially balanced  {-)

Your thought of.....  "will I need to use a slave motor?" is an excellent idea..........if space & mass permits....a 12 V motor vehicle windscreen wiper motor would provide masses of slow speed torque with the worm & worm wheel output which could simply be connected to the rudder quadrant below deck & standard servo control

An alternate to this could be a heavy duty hi-torque yachting type winch servo....how this may need additional engineering for installation

There a number of +'s and -'s with both concepts......

Are you actually building the hull in steel?.....a few photographs would be appreciated........Derek





Here is a posting from yesterday in another thread ......Hi Toesupwa,

The pivot point must be counted as the last point the the tow rope is in contact with the tugs structure and as you correctly point our your towing point (Staple) is aft of the units.  If you look at the configuration of any single, twin or ASD propelled tug you will find that the towing point is just aft of midships, mush further forward that on your vessel.

The easiest way to explain i feel is in terms of vessel rudders.  These have developed over the years and there are three basic types which have been used over the past century or so;

Fully Balanced.  This is when the rudder stock is almost in the centre of the rudder blade allowing equal forces to act on the area ahead of the pivot point and equally on the area aft of the pivot point.  The advantage of this is that you require a very small torque to turn the rudder, but the disadvantage is directional instability as the rudder will have a tendency to wander due to the equal forces being appled as it passes through the water.  In tug terms this would be great for a harbour tug with her towing point midships as she would be very maneuverable and would be able to pivot on her tow line with minimum rudder appled.  This direction instability always gives the danger or turning the tug over (where the tow rope comes across the beam at right angles almost midships at the towing point) and this is why a gog or gob rope is sometimes used to transfer the towing point further aft.

Semi Balanced.   This is where the rudder stock is approximately 1/3 back from the leading edge of the rudder blade.  This increases the turning torque required but gives much better direction stability.  This is the type of rudder used in all merchant vessels with a conventional propulsion package built today.  In tug terms this is what most single/twin/ASD tugs have.  This gives good maneuverability for use in harbours but still excellent direction stability for towing at sea (i.e. in a straight line).

Non Balanced.  This is where the rudder stock is located right on the leading edge of the rudder, whilst giving the best directional stability it gives the worst turning performance and requires the most torque to turn the rudder blade.  This is the category that your tug falls into.  When you are towing over aft your tug will not pivot around the towing point at all.  The entire tug will have to force the complete length of her hull through the water to change direction which will lead to using all engine power to position your tug and not the tow, this will lead to total loss of control of the tow.

You have made such a nice job of her top sides and she looks like she will be a cracking model, i would just suggest that you think about the option of placing the towing winch on the bow and towing through the lead on the bow as most ASD tugs to to avoid disappointment with the performance of your finished model.

Cheers.

Tugchief.
[/quote]
Dave .....just thinking of the example servo offered by TT as ...... "the Hitec HS815BB has about 23kg/cm torque on 6v"

So....if we consider......your barn door rudder is 6" long.. or ~~~~~152 mm long.....100 divided by 152 = 0.66...so 23kg torque on the same 152 mm = 0.66 or 15Kg

What does mean?....... {-) %)...if your fish scales are of metric calibration & you get a resultant from my recommended test scenario of 15 kg or less...hey presto...the  Hitec HS815BB on 6v would be a good solution  O0 :embarrassed: ....Derek
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FIRPARK

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Re: DHULIA/MOORCOCK TUG
« Reply #10 on: January 27, 2010, 10:39:56 PM »

Thanks for the info. re 1960 Model Engineer article's have a friend who may well have the issues required. I never thought of Model Engineer, the article I have for Nova was in March 1980 Model Boats. and it covers just superstructure construction in wood, and a few deck fittings. The hull I have is steel frame, epoxy coated with a similar material to that they use to plaster full size quality steel sailing hulls with in the 1970's, to take out imperfections. --The hull length is almost 57ins--will a 12volt Smiths car heater fan motor be OK, or should I look for something with more power?
Thanks for your help.
Dave
 
It may be of help to you to know that the original data for this model was published in "Model Engineer" in the form of a series of articles spanning many issues.
The Nexus plan that you have is, in fact, derived from these articles.
I have a number of photocopies (some very poor quality) of articles taken from the original magazines. They form a very good source of data for building the ship.
Sorry that I cannot quote the dates of publication at present as I am away from home at the moment.
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derekwarner

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Re: DHULIA/MOORCOCK TUG
« Reply #11 on: January 28, 2010, 12:04:20 AM »

Dave........there are hundreds of experienced long term modelers on Mayhem [I am just a newbe] ....but without photographs & accurate hull detail we are all just guessing

Option 1..... post a heap of .jpgs....+ hull dimensions + vessel displacement + the prop size + detail of your Smiths motor...RPM, no load current draw /stall current draw ...etc

Option 2 ....take the hull down to & join a Model Boating group in your home location...most club members will also be more than happy to offer constructive comment

Option 3 ........do both  O0 {-) :-)) .......Derek
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Derek Warner

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Illawarra Live Steamers Co-op
Australia
www.ils.org.au
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