1/72 Airfix Grumman Duck (Murphy’s War) – Build Log

23rd February 2014

Next up was to finish assembling the undercarriage and to fabricate an exhaust system and mount the engine…

The assembly of the undercarriage was ‘orrible…

The parts hardly fitted together, the two triangular pieces that make up the suspension arms had to be de-flashed and bent into shape in order to fit properly. Also the instructions didn’t really show which parts went where, which given the fact that the parts didn’t appear to fit in any configuration made it interesting to say the least 😉

Anyway, with the suspension elements assembled, painted and weathered it was time to fit the wheels.

For this kind of job where you need to put the glue on first and then mate the parts together I like to use Revell Contacta because it has a slower drying time than thin type cements. Using cements such as Mr Cement-S means that by the time you bring the parts together the glue has evaporated, Contacta stays wet for longer so gives you time to manoeuvre everything into place.

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With the wheels on, the undercarriage was attached to the fuselage – in the photo below I haven’t touched up the glue marks yet – I’m going to do all the touching up as a final step at the end.

For the hydraulic part of the undercarriage suspension, I brushed on a coat of Mr Metal Color buffable Chrome Silver and gave it a good buff with a cotton bud.

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With the wheels on, it’s time to work on the exhaust system. This kit comes as standard with an engine cowl, in the movie the cowl has been removed to expose the engine. Since the supplied engine was designed to only be seen from the front of the cowl it was of poor quality (see earlier in the build log for photos), so I chose to buy an aftermarket engine to replace it. There was no exhaust supplied in the kit either so this has to be cunningly fashioned…

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2b

 

I decided to make the exhaust from Milliput as it is easy to work and has a slow curing time.

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Milliput is easy to use, you just tear off equal sized amounts of each of the supplied putty’s and mix them together by kneading (rolling into sausages between your hands works fastest).

You then have around an hour to work the Milliput into shape before it cures.

Here I have made the main exhaust section out of a sausage of Milliput which tapers to be thicker at each end. Also I made up a load of small Milliput cones which I will use later to make the stubs where the exhaust attaches to the exhaust ports of the engine blocks.

The ends of the exhaust kick backwards slightly, so I rested the Milliput exhaust against a cocktail stick to keep it in shape while it sets.

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Once the exhaust has cured for about an hour I offered it up to the model and white-tacked the engine in place. This allowed me to tweak the shape to make sure it would fit just right.

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As you can see below the ends have been set to kick backwards as per the reference pictures.

 

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The exhaust was left to cure over night, when fully hardened I mounted it back on the model and marked the centre and ends with a green sharpie ready for shaping.

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Below you can see the ends have been sawn off to the desired angle and sanded.

The exhaust is then taped to the engine, and the first of the Milliput cones cut to length ready to be glued to the exhaust with CA glue (CyanoAcrylate AKA Superglue).

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Here’s the first exhaust port glued in place, the trick is to manoeuvre the Milliput cone into place, give it a dab of CA glue so that you have a bead of CA joining the exhaust to the cone and then give it a quick spray of CA activator spray (kicker).

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Another exhaust stub CA’d in place.

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And here we are with all the exhaust stubs tacked into place.

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The tape was removed to release the exhaust, and I gave each exhaust port stub a bead of CA and a blast of activator spray to blend it into the shape of the exhaust.

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The next job was to open out the ends of the exhaust. To do this I drilled a hole up the end of the exhaust using my smallest drill bit in a pin chuck and then reamed out the hole as large as I dare with successively larger drill bits. When the hole was as large as it’s going to get without cracking the Milliput, the rest of the hole was pared into shape with a scalpel.

Milliput is great stuff, but it’s very weak for small parts so you have to be extremely gentle when handling it. Later in the build I actually snapped the exhaust while buffing a coat of buffable metalizer paint.

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On the original the exhaust is in two sections, so I split it in two with a scalpel…

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And trimmed it as close to the exhaust port stubs as I dared. The next part of the shaping will be done with the trusty old Flory sanding sticks…

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The photo below didn’t turn out very well, but you can see the finished shape of the exhaust sections after sanding…

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The photo below gives a better impression of the finished exhaust shape…

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And here’s the engine components ready for a bit of paint…

 

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The engine parts were all sprayed with Mr Metal Color buffable metalizer, Aluminium for the prop and the centre of the engine block, dark iron for the rest of the engine block and exhaust.

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The engine block and prop had a coat of homebrew ink wash. The exhaust was highlighted with Tamiya XF-68 Nato Brown to give it a rusty look, and it also had a touch of Tamiya Weathering Master(Burnt red and oil stain).

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Here’s a shot of the assembled and painted engine…

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Next up was to attach the engine to the fuselage. Having CA glued the exhaust to the engine block, the engine didn’t fit quite as snugly to the fuselage as it should. It needed a small shim to pack it out in order to get it to sit flush. I tried various thicknesses of styrene sheet to find the desired thickness. To get it to stay in place while dry fitting I used good old “Pritt-stick” – or the Wilko’s equivalent the nippers use for their school projects.

 

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Once I worked out the thickness I needed I measured the diameter of the engine mount (7mm)

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And marked the diameter onto the styrene sheet with a sharpie ready to be cut out with scissors…

My circle guide is marked in radius values BTW hence 3.5mm radius.

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The styrene shim CA glued to the engine block, and the edge ahs been gone around with a bit of Tamiya flat black as I don’t want a bright white disc to be visible behind the engine…

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And as I near the end of the build, the engine mounted in pride of place at the business end of the aircraft complete with Milliput exhaust system…

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The next stage will be to do the rigging and then after a bit of a touch up and titivate it’s be time for the final reveal…

Thanks for visiting!

I write this blog for fun, to share what I've learned, and to share my builds with you. If you like what you see here please leave a comment, and head over to facebook and like my page!

Cheers - Rich



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