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Author Topic: NZ Coastal Tug Koraki  (Read 9511 times)

Steve Mahoney

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NZ Coastal Tug Koraki
« on: September 17, 2015, 01:40:37 AM »

I've got this build log on a couple of other forums but some of you may be interested in it. I've completed the hull and these posts will bring you up to date on the build so far.
[/size]My last project – the Mark I SDM, had barely left the bench when I started on this one: the tug Koraki.
The Koraki is a small (21m) coastal tug buit in New Zealand in 1986. It has had a very busy worklife and has worked out of just about every port in the country, mostly towing barges. Currently it is ferrying barges of cement 24/7 between Auckland and the new oil refinery being built in Whangarei.
For a while in the 1990s it worked out of my town, Wellington, and it was the subject of my first attempt at scratch-building. I was lucky enough to get some plans from the builders' yard and made a basic model for my son’s room. Not sure what possessed me to make this particular boat at the time but it’s a tough looking little tug and the yellow looks good.
Twenty years later I’ve decided to rebuild it, static only. The Koraki has changed a bit since 1995 and was never built exactly as the original plans depicted. I still had the plans so I contacted the current owners and was able to go aboard and get plenty of photographs. The owners were very heplful. The boat has had a few changes over the years and I’ll build it as it is now – only not so knocked around.
At 1/50 it is tiny – 420mm LOA. I’ve always built at 1/50 so I’ll stick with it. Wish my first models had been at a larger scale then I wouldn’t be locked into the fiddly small stuff at this size. Could be a slow build but I'll try to make regular updates.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #1 on: September 17, 2015, 05:53:24 AM »

First job: Drew up the keel and hull ribs and had them laser cut out of 3.6mm ply.
Quick and easy and much more accurate than I could get by hand. Everything just slots together and super glued.
In the late 1980s I met an old bloke who had made a model schooner in 1914 (when he was 14) and he made the whole thing out of a single 6"x6"x6' piece of black oak. Had to saw it into planking, mast, ribs, etc and also turn and carve all of the equipment from the one plank. The model still exists – he had just got it back from a great nephew to restore it. Makes me realise how easy we have it these days with easy access to materials and high tech tools.
As this model is static only, I won’t need to get inside the hull so the ribs are solid and they are twice as many as I would use if I needed room for motors and electronics. etc.
I made a simple jig from MDF and Lego to hold the keel staight and true. Spacers keep the ribs parallel and at 90º to the keel.
…and that is the cleanest, tidiest photo of my bench you'll ever see.

[/size]With the 1.5mm ply deck attached the carcase is very solid and feels almost bulletproof. Would have been ideal to make a hull mould at this stage – hindsight is always 20/20.
The deck has the bulwark support bases already laser cut, ready to drop in the laser cut supports.
Packed out the bow and stern sections with basswood and sanded them and the rib edges into shape to accept 1.2mm ply hull sheeting. This is the easy part where things seem to progress quickly.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #2 on: September 17, 2015, 07:12:12 AM »

Next step: [/size]Drew up a pattern for the topmost chine and cut it out of thin cardboard. I used this for checking the size and alignment, and then cut the final section from 1.2mm ply.[/size] [/size]I did the top chine in 4 segments: bow, stern and 2 sides. That gave the lower edge of the chine a nice clean line. It overlapped a bit at the deck but that was easily sanded down to deck level.The rest of the hull was done in the same manner.The section where the bow meets the keel was a very complex curve and I couldn't form it out of 1 piece of ply. Can usually do this with layers of 0.5mm or 0.8mm ply but not this time. Had to do it in short sections and sand the joins flush. Not ideal but that's what filler is for.Happy with the basic form. Starting to look like it should now – a very solid, muscular hull.Now – resin, sand, undercoat, sand, fill, sand and repeat about 10 times.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #3 on: September 17, 2015, 07:28:37 AM »

Attached the bulwark struts which I had laser cut. Very easy to drop them into the slots laser cut into the deck. The struts are 1.5mm ply.
Cut out the anchor well at the same time. Involved a little sanding and filling but now looks fairly seamless.
Also built up the roller deck. All of these components have been laser cut – much quicker construction, and more accurate than I could do by hand. Takes a little time to draw them up but seems worth it the long run.
The bulwarks are 0.8mm ply – much stronger that is looks. I give the exterior a coat of polyester resin for good measure. Seals it, fills any minor gaps and stops any flex in the ply. I use the same pattern technique as used for the hull sections to form the bulwark sections. As long as the lower edge is a good fit with the deck I can always sand down any excess at the top to make it flush with the top of the support posts. As you can see, the rough cut at the top is easily sanded down.

[/size]The complex curves at the stern are 2 layers of 0.4mm ply laid with the grain at 90º to each other. This is very strong. Individually the pieces are very flexible and can't stand a lot of handling, together they are very robust.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #4 on: September 17, 2015, 07:33:07 AM »

I got preoccupied with the build at this stage and forgot to take some progress photos so the next images fast forward a couple of weeks. The capping rail has been added, the freeing ports are done. The real boat has very pronounced reinforced weld lines along the chine lines. I added these with half-round styrene. Hull painted, sanded, filled a few times to get rid of any blemishes.
Time consuming but that is where any imperfections really stand out. Don't look too closely.
Started on the Kort nozzles.
Attempted to draw them up in 3D but ended up needing a lot of help, They printed OK but the surface quality wasn't as good as I had hoped. I'll have to try Shapeways next time, Patmat's results seemed much better than the local result.
The nozzle supports are brass and styrene, brass shafts with outer sheathing of styrene.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #5 on: September 17, 2015, 07:42:32 AM »

Finished the hull. The chine lines have very pronounced reinforced welding lines. I used half-round styrene for these. Fender housing from 1mm ply.
[/size]After a lot more sanding and a few layers of undercoat is was ready for painting. I kept finding imperfections after each coat of paint so the last round of filling and sanding took ages.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #6 on: September 17, 2015, 07:46:20 AM »

...and painted. I had made the bollards, deck vents, bitts, etc. between putting on the coats of paint. Also added some anodising plates to the mort nozzles. The real boat doesn't have them anywhere else on the hull.
Made the bow platform and stern roller from styrene.
I usually use enamel paint throughout but this time I used acrylic for the deck – hopeless. I won't try that again. Couldn't spray it so had to brush it on and it needed about 5 coats. Not that happy with the finish either but it's staying now.
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mermod

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Re: NZ Coastal Tug Koraki
« Reply #7 on: September 17, 2015, 08:28:54 AM »

That looks brilliant, nice work :-))


Phill
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Re: NZ Coastal Tug Koraki
« Reply #8 on: September 17, 2015, 09:45:39 AM »


Very nice work sir!   :o
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #9 on: September 23, 2015, 09:06:00 PM »

Thanks for the encouraging comments guys. I'm a long way from your standards yet. Picking up lots of hints about laser cutting from Mermod's posts.Had a bit of a breather after the hull was completed. I did make a start on the superstructure. The basic carcase is 1.8mm ply which I had laser cut with the deck and bulwark supports. Drawing up the parts for cutting takes a little time but makes assembly very quick and simple. Just slots together and gives a very solid base. This is the easy part.
[/size]The bridge/wheelhouse came together in the same manner – after some manual adjustment to the front window widths – forgot to allow for the thickness of the ply. Luckily, it didn't take too long to remedy and after a coat of paint you'd never know.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #10 on: September 23, 2015, 09:10:36 PM »

After filling, sanding and undercoating several times I was ready to add a few details.The portlight bolts were easier to do than I had imagined.I printed out a grid on clear film and used a pin to mark where the I deeded to drill.Then used a 0.5mm bit held in my fingers to drill through the ply. Needed a delicate touch.The rest is pretty easy to see from there photos. Styrene rod glued into holes and used a piece of 0.5mm styrene sheet to give me a height to sand down to. Don't know the correct name for the shade/rain visor/protectors above the windows but they were added from segments of styrene tubing that had been sanded to a fine taper.
The last image is the result. The glass is quite recessed in real life so I can simply attach it to the inside of the wall.And for the rivet counters – there are 14 bolts on the real boat's windows but I have only used 8.And that will haunt me to my grave.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #11 on: September 23, 2015, 09:12:23 PM »

Got the etched brass that I had been waiting for. Only 2 weeks from ordering from PPDL in Scotland to delivery in New Zealand. That's a pretty good turn around. As usual the quality is excellent however at the last minute I changed the brass from 0.7 to 0.4mm and didn't adjust the artwork, rendering all of the stanchions paper thin – and useless.Luckily I have enough from a previous build to make up the numbers.The name plate has the original name of the tug – SeaTow 21 (not very imaginative). on the real boat this has been painted over but you can still see a faint outline. I haven't decided if I'm building it as is or as it was in 1995. Any eagle-eyed members from Otago might spot a clue for my next project hidden in the sheet.
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Re: NZ Coastal Tug Koraki
« Reply #12 on: September 23, 2015, 10:43:57 PM »

Any eagle-eyed members from Otago might spot a clue for my next project hidden in the sheet.

Those are funny looking anchors!!  :-))
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unbuiltnautilus

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Re: NZ Coastal Tug Koraki
« Reply #13 on: September 24, 2015, 09:23:39 AM »

Very tidy looking build. Question, who is PPDL of Scotland? That etch work looks very good indeed.
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nivapilot

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Re: NZ Coastal Tug Koraki
« Reply #14 on: September 24, 2015, 12:14:53 PM »

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unbuiltnautilus

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Re: NZ Coastal Tug Koraki
« Reply #15 on: September 24, 2015, 01:06:57 PM »

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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #16 on: October 06, 2015, 07:11:56 AM »

Back to work…As the doors also suffered from the change to thinner brass I packed them out with 0.5mm styrene to give them some depth. The etched holes were the perfect size for the brass rod for the handles. Soldered them from the rear to cut down on excess solder to remove.Was also able to smooth out the joins in the bridge/wheelhouse. The visor is styrene and the corners are pretty much solid filler.A nice simple bit for the next stage – funnels.These are ply with a very thin styrene skin.Those ladder rungs don't look too straight in the construction photo. I subsequently replaced them. I tend to do that a lot. I usually end up making about 25% of the boat twice. No wonder they take so long to finish.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #17 on: October 06, 2015, 07:15:44 AM »

The basic superstructure was finished and primed/undercoated. I added a capping rail of thin styrene and recessed the brass stanchions into it. The stanchions were CA glued into place and then a brass rod rail was soldered onto the top of the stanchions. I made the top rail from 3 sections so that I could have more leeway when positioning them (and I couldn't get rod long enough to make the whole rail in one piece). I joined them at the stanchion. It worked out quicker and better than using 1 piece – too many curves to align.Finally, I used a left-over stanchion as a jig to hold the lower rails in place while I soldered them to the end post. Seems simple now but it took several evenings of soldering and filing.The vent bases are styrene as are the vent cowls that sit on spacers over the vent shafts. Didn't bother with any detail on the aft ceiling as you'll never get to see it.As you can see there are still plenty of rough spots to tidy up.
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Re: NZ Coastal Tug Koraki
« Reply #18 on: October 06, 2015, 09:19:42 PM »

Back to work…As the doors also suffered from the change to thinner brass I packed them out with 0.5mm styrene to give them some depth. The etched holes were the perfect size for the brass rod for the handles. Soldered them from the rear to cut down on excess solder to remove.Was also able to smooth out the joins in the bridge/wheelhouse. The visor is styrene and the corners are pretty much solid filler.A nice simple bit for the next stage – funnels.These are ply with a very thin styrene skin.Those ladder rungs don't look too straight in the construction photo. I subsequently replaced them. I tend to do that a lot. I usually end up making about 25% of the boat twice. No wonder they take so long to finish.

Only 25%? I've heard of a shipbuilder whose 'claim to fame' was making close to 30% of the ship twice!
But seriously, your build is looking fantastic! - Tom
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #19 on: November 07, 2015, 02:02:17 AM »

Thanks Tom.]
[/size]I've been slowly beavering away making lots of small, detail parts over the past few weeks. For a while everything I touched turned to custard: breaking bits off the model, dropping things, spilling paint and glue. I seized the airbrush compressor.
[/size]Usually I try to use paint straight from the tin, if I'm mixing a colour I mix enough to last the whole construction period. This time I didn't mix enough extra hull red oxide and sure enough when I needed to do some remedial work I had a "xxxxx" of a time trying to match the original. Same for the deck colour. Then I resprayed the upper hull but I had a dud tin of paint and what should have been satin turned out to be super gloss. More respraying. Very frustrating.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #20 on: November 07, 2015, 02:04:52 AM »

...and painted
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #21 on: November 07, 2015, 02:07:57 AM »

I did manage to complete the mast. It's quite small and complex and sorely tested my soldering skills. Lots of filing involved.[/size]It's much easier working on a complicated piece when you're using heat sinks – a couple of alligator clips proved to be very handy.Glad that's over, although I did manage to break the aerials off a couple of times – and one more time while photographing the painted version. Doh!No working lights on this model. The 'white' lights don't look so blue in real light.
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bassplayer1

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Re: NZ Coastal Tug Koraki
« Reply #22 on: November 07, 2015, 07:59:31 PM »

Fantastic work!!! :-))
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #23 on: November 11, 2015, 07:46:17 AM »

Thanks Bassplayer, I've been following your Greek ferry with interest.
[/size]I now have everything ready to install apart from the winch and ship's runabout. The winch is, as usual, quite complicated and I've been avoiding it. The dinghy is a tinnie with a cover so no major problems there.I've decided to show the Koraki as it was in the late 90s, when it was still owned by Seatow and just after they changed the name from Seatow 21 to Koraki. That was also around the time when the original bow fenders were replaced by tyres.I had initially hoped to find some appropriate rubber tyres on some toy cars and use them. Couldn't find any 1/50 truck tyres at a reasonable price (I needed 10) or a digger tyre either. So plan B, I used some laser cut disks to make them. The burnt edge sort of resembles tyre tread for the smaller tyres. Styrene for the digger tread. Several coats of almost black and I'm happy with the result. If you squint hard enough they look like old tyres.
[/size]Attaching them was another story.The real boat's truck tyres are bolted onto the hull/bulwark and only the digger tyre is attached by chains. If I glued the truck tyres into place it would be correct as per the real boat but it would look like I'd taken the easy option. So I used chain for them all. Very fiddly but looks much better.The hull is all complete now and only needs the name and hull markings applied. I always leave those to the very last job.
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Steve Mahoney

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Re: NZ Coastal Tug Koraki
« Reply #24 on: November 26, 2015, 10:53:12 PM »

Made quite a bit of progress in the past few weeks – barring a few days where I kept dropping things that had just been painted, losing small pieces and generally stuffing up everything I touched. The wheelhouse/bridge in now finished, painted and has all of its detail parts added.
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