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 real size new builds and the scale build

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tarak
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Posts : 5
Join date : 2019-10-18
Location : Devonport Tasmania

real size new builds and the scale build Empty
PostSubject: real size new builds and the scale build   real size new builds and the scale build EmptySat Oct 26, 2019 6:26 pm

Hi, I am new to this forum, and have been looking though what may interest me.
My two brothers have scale model tugs one being the Yorkshireman or the Irishman
I was ask a number of questions as my brother Roy know that I have been working on new build problems of full size ships.
This had come about due to a new form of power generation but using steam for driving the generator instead of the diesel engine or gas turbines.
The new Plasma heated SCW Generator to provide supercritical steam, and the plasma system uses fresh water desalinated from the seawater, for both the plasma system and the steam generators.
 
So I have to do a crash course on hull and ships power systems I am an electrical tech.
The need was to find out how much power a ship requires, this was for a new build ship, navy, but can apply to all ships.
 
New build ships normal use a scaled model hull in a test tank, pressure downward for the designed DWT or GWT, the towed to the required speed to find out how the hull performs.
 Building a scale model to the overall size is one thing but then to run it at is true scale speed is another. Then getting the propeller thrust correct to do this and weighing the boat to the scale GWT.
So I am asking is anyone interested it what I am doing and how some of the computations may be applied to a scale models that you are building.
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tarak
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Posts : 5
Join date : 2019-10-18
Location : Devonport Tasmania

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PostSubject: Continuing   real size new builds and the scale build EmptySun Oct 27, 2019 9:02 am

for you interest


When looking at ships the power to weight ratio is important if you have to consider the fuel that you are going to use and the distance between stops.
 
Now with my new approach this fuel to weight ration does not apply only the size and to the ships engine room.
 
The military have a different power to weigh ratio the need for speed to fuel and distance is important and two speeds cruise and tactical speed.
 
So let’s look at some real ones  
 
Emma Maersk single engine one screw 25kts
Gross tonnage 170,794 ton
Propulsion power only 81,000,000 watts  or 81MW or 108,622.79 HP
So power to wt
So  474.26 watts to the ton  but in
shipping language 474.26 kw per 1,000 ton or  635.99 HP per 1,000ton
 
QM2   4 azimuth thruster type podded propulsion units  twin propellers each  speed   30kts 

       

Gross tonnage     149,215 tons
Propulsion power only 86,000,000 watts  86MW  or 115,327.9 HP
So power to wt
576.35 watts per ton
shipping language 576.35 kw per 1,000 ton  or  772.90 HP per ton
 
now the Daring class destroyer type 45
Gross tonnage 7,300 tons   twin screw 27kts
Propulsion power only 42,000,000 watts 42MW  or 56,322.93 HP
 
So power to wt
5,753.42 watts per ton but in
shipping language 5,753.42 kw per1,000  ton  7,715.47 HP per 1,000 ton
 see the difference
 
The Yorkshireman tug  50ton bollard pull
Gross tonnage 144 ton twin screws 12.5kts -13kts
Propulsion power only 2,460,000 watts 2.46MW  or   3,298.00 HP
So power to wt
17,083.33 watts per ton but in
shipping language 17,083.33 kw per 1,000 ton or 22,902.78 HP per 1,000 ton
 
model The Yorkshireman tug  my brothers 1/48 scale
 
Gross wt  13kg   twin screw 50 mm 6 bladed props
Total power 120  watts  12v x 5a max each motor so is total 120w
So power to wt
9.23 watts per kg
Timed full speed over 10m 7.5 real time seconds or 1.33m/sec  2.975mph real time
Bollard pull 2.5lb  or 1.13kg
 Then what is the real scale speed?
Problem here is the gwt and the power are not scaled and this is why scale speed is hard to fully calculate.
I have been working on it for them
 
I do have a new proposed real build
Trimaran
Expected  Gross tonnage 9,000 tons  twin screw and 4 water jets speed excess of 45kts
Propulsion power only 100,000,000 watts 100MW  or 134,102 HP
 
 2 x 20 MW motor driven 6 blade VP screws plus 4 water jets 15MW each
So power to wt
11,111.11 watts per ton but in
shipping language 11,111.11kw per 1,000 ton  or 14,900.22 HP per 1,000 ton
 
the difference here is it has unlimited range and could do 30kts all day
 
So could I then take a cargo ship and give it unlimited range? yes, and that is what I am working on sizing up power systems for them.
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tarak
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Posts : 5
Join date : 2019-10-18
Location : Devonport Tasmania

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PostSubject: trimaran   real size new builds and the scale build EmptySun Nov 10, 2019 2:38 pm

the new proposed real build trimaran drawing outlines and for a model build is in progress power and speed already done
still working on the hull shape but starting to look good
the real size would be basically for a new destroyer, 160m x 40m  draft 10 - 12 not fixed at the moment
9,000 imp tons speed in excess of 45kts. and no fuel on board unlimited range.
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nhp651
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Posts : 3951
Join date : 2011-06-11
Age : 68
Location : Fleetwood Lancashire

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PostSubject: Re: real size new builds and the scale build   real size new builds and the scale build EmptyMon Nov 11, 2019 11:19 pm

you'd keep more people interested, tarak, if you posted some photos with each of your written  posts...…...we like photos on here.
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stavros
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Age : 59
Location : Bethesda in the land of the dragons...North Wales

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PostSubject: Re: real size new builds and the scale build   real size new builds and the scale build EmptyTue Nov 12, 2019 9:27 pm

Defo PHOTOS PHOTOS AND EVEN MORE


Dave
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tarak
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Posts : 5
Join date : 2019-10-18
Location : Devonport Tasmania

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PostSubject: Re: real size new builds and the scale build   real size new builds and the scale build EmptyThu Nov 14, 2019 8:58 am

ok yes it is good but I wanted to see if was interested on how your scale boat compare with the real size.

as for the new scale model build of the full size trimaran I am still doing the design work and frame by frame on a full size build takes time once the skeleton is done then the skinning can be done this then is transformed into a model size that size has been picked for 100:1 so the scale model will be 1.6metrs.
then sizing the scale power system from the real 120MW to the model has to be then done.
not easy from scratch.
I do have photos of my brothers tug  but that is not the same as your  own.
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Roadrunner
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PostSubject: Re: real size new builds and the scale build   real size new builds and the scale build EmptyMon Nov 18, 2019 9:08 am

Generally only the astetics are scaled to give an overall accurate model ( and that tends to only be the rivet counters) most models are generally accurate but come down to time, money and ability to get true scale....

Internally not a chance no model is internally accurate  what so ever.

As for Thrust, rpm and Bollard pull forces within a model....
First thing you can’t scale water or distance water is still water and a mile is still a mile... so running gear for boats tends to be what works best to use the model, but also to have extra power to get out of issues, or over powered due to the use of the boat... examples of overpowered from scale would be the tug towers, or fast elective mono 1’s, cats etc.

So to sum up 

Scale from full size to model subjective to the hobbies needs...

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