Author Topic: 1960s Refinery Tug – Parahaki  (Read 2269 times)

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sea monkey

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Re: 1960s Refinery Tug – Parahaki
« Reply #60 on: November 05, 2017, 14:02:57 »
At this stage I've also found another major error on my part. I had drawn up the plan for the deck and superstructure footprint from several photos I took at the Auckland Museum. That were taken from directly above the model and when drawing up the plans I hadn't taken into account the amount of distortion or fisheye that my camera gave the image. Subsequently when I measured the width of upper deck I got an incorrect measure. The whole superstructure is about 10mm too wide. It still fits but any deckhand would have to hold his breath when he tried to walk past the front of the superstructure. The gap to the bulwark is only 1m in scale. Better luck next time!

model tugman

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Re: 1960s Refinery Tug – Parahaki
« Reply #61 on: November 05, 2017, 14:20:42 »
That looks a complicated structure Steve, very nice, but it is only 5mm too wide each side, there now that doesn’t sound so bad does it?  Geo.
Tugs are for life      George B

sea monkey

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Re: 1960s Refinery Tug – Parahaki
« Reply #62 on: November 06, 2017, 21:16:19 »
Ha ha, if you put it like that, it's not much more than my usual margin of error – a mere gnat's.


sea monkey

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Re: 1960s Refinery Tug – Parahaki
« Reply #63 on: November 06, 2017, 21:24:14 »
Shapeways came through with the the goods very quickly. Eight days from placing the order, printed in New York to delivery in New Zealand. Not bad. Let's see if PPD Etching in Scotland can match that for the brass etched components.

Image No 1 shows the initial drawing with dimensions.

Image 2 is a screen shot from the 3D stl file

Hey presto! 8 days later.

sea monkey

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Re: 1960s Refinery Tug – Parahaki
« Reply #64 on: November 06, 2017, 21:30:50 »
I had this part printed in strong, white and flexible as Kort nozzles are easy to knock around.

It is surprisingly strong – the nozzle wall is only 1.5mm thick but this material does show the striations from the painting process.

Printing in finer detail material would have doubled the cost.

Hopefully a few coats of paint will flatten a few of those layers – it doesn't handle sanding too well. The last time I had something similar printed (some ASD units) the looked the same and didn't look too bad after throwing on some paint.
« Last Edit: November 06, 2017, 21:42:09 by sea monkey »

VANYA

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Re: 1960s Refinery Tug – Parahaki
« Reply #65 on: November 07, 2017, 12:56:16 »
Steve.

Those nozzles are real tug bling! Nice they are.

I made some out of fibreglass resin then lathed them up.Also heavy gauge steel machined and silver soldered would be equally as nice for working models.

Looking good.

H
VANYA

mengam

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Re: 1960s Refinery Tug – Parahaki
« Reply #66 on: November 14, 2017, 09:43:43 »
Hello

Your Kort nozzle have a strange shape, it's normaly a cylinder inside, conical outside with a torus for the inlet and like a blade as trailing edge

Your conical nozzle as oulet is a typical counter intuive shape for a boat. It's possible for air propeller as compressible fluid but inapropriate for the not compressible water.

With your shape you decrease the bollard pull of your tug without any profit.

Around 2002 have seen this twice tugs at Noumιa New Caledonia, I have to search in my pictures (prior digital pics) I'm sure to have some details pics.

Mengam

 

   





sea monkey

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Re: 1960s Refinery Tug – Parahaki
« Reply #67 on: November 14, 2017, 12:29:20 »
I agree, it is an unusual shape.
As I don't have any plans or images of the boat out of water I am basing below the waterline on the model at Auckland Maritime Museum. Their model is pretty accurate and was made in the tug's home port a few years after it began working there. In those days the harbour boards were quite generous about sharing plans so I'm assuming that the model is correct.
These photos of the model are a bit blurry but you can see the rear tapering of the nozzle.
They could be wrong, maybe? The nozzle doesn't look like it would have much of a turning arc either.

Steve

des

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Re: 1960s Refinery Tug – Parahaki
« Reply #68 on: November 14, 2017, 19:57:47 »
I was looking into the shape for a Kort nozzle, and found this - check it out

http://www.propellerpages.com/?c=nozzles

I didn't realise until a couple of days ago that there are different nozzle shapes intended for tugs (which need to develop thrust both forward and in reverse) and for others such as trawlers, AHTS / PSVs etc (which primarily need most thrust forward).

There is also a newer design, the Rice nozzle, which delivers higher thrust and better fuel consumption than either Kort shape.

Des

sea monkey

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Re: 1960s Refinery Tug – Parahaki
« Reply #69 on: November 15, 2017, 11:41:51 »
I'm pretty sure the shape of Parahaki's nozzle is right.
Mengam rightly points out that you can't compress water – although all Kort nozzles have a very slight taper that 'focuses' the flow into a 'directed' stream. The forward opening in always slightly wider than the rear. Often this is just in the 'wing' shape of the nozzle wall.

back at the bench – a bit of paint always helps...
I've added a skirting around the base to hide any gaps between the deck and the bulkheads. Still need to add a few more basic details such as a gutter strip around the edge of the upper decks and some trim around the top edges of the bridge. Then on to the fiddly bits.
No bridge details on this one – it would have all been guesswork and tinted glazing will make any interior details redundant.

sea monkey

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Re: 1960s Refinery Tug – Parahaki
« Reply #70 on: November 15, 2017, 11:42:37 »
And, yes, to any eagle eyed viewers. The rear 4 port holes on the port side don't have surrounds – they will be covered by hatches.

model tugman

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Re: 1960s Refinery Tug – Parahaki
« Reply #71 on: November 15, 2017, 23:54:08 »
Lovely work matey , looking good.
Tugs are for life      George B

VANYA

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Re: 1960s Refinery Tug – Parahaki
« Reply #72 on: November 16, 2017, 01:26:08 »
Steve.

You really need to build the Aorangi. 

It would be most impressive and after seeing the details you build into the models it would look brilliant. Only you can do it this well and at this scale.

She is 86 feet long.

Hayden
VANYA

mengam

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Re: 1960s Refinery Tug – Parahaki
« Reply #73 on: November 17, 2017, 05:31:41 »
Hello

The outside shape of this nozzle is up to the model, maybe correct maybe not, this conical section only at the end maybe for structural or industrial reason ...

Anyway for the inside shape it's hundred percent not correct.

It's a fault for a marine engineer to built a nozzle with smaller diameter at the outlet than at the propeller place

With an outside like this, the interior shoud be like that



Then as the propeller must be at the nozzle rotation axis - you will have a problem with the leading edge of the inside rudder during rotation of the nozzle up to the regular max at 35°

As promised : the two sisters at Noumιa in 2004 







It's a pity as most of the time I also take detail pictures of the aft deck (like spy in relation with my job ...)  but that time as they looked more like bohemians traveling with trailers on the deck I didn't !

Mengam



 
« Last Edit: November 17, 2017, 05:33:44 by mengam »

sea monkey

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Re: 1960s Refinery Tug – Parahaki
« Reply #74 on: November 20, 2017, 14:17:24 »
Thanks Mengam. Great shots, were you working in Polynesia? Looks like the tugs are doing general cargo work as well.
As this is a display only model I'll leave the nozzle as it is. If you don't tell, I won't either.

Made a little progress over the past week. I now have all of the components needed for the hull ͺ the last bit being the Kort Nozzle) so I assembled everything and got some paint onto the hull. I'm a bit of a stickler when it comes to colour and the deck and inboard bulwarks went through several coats before I was satisfied with the final colour.

Both colours as shown in most of my reference are in post NHB use, and are slightly different from the Harbour Board colours.
After the boats left NZ the superstructure was repainted in a sort of International Buff and the decks in dark red. In Whangarei the superstructure was more of a 'Caterpillar' yellow and the decks a dirty, dark orange. I'm using the Museum model as reference for my colours.