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Serkan Sen

Legendary Blackbird - Part 1: A-12 Oxcart (Italeri Conversion)

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5 hours ago, Graeme H said:

Interesting that the chine seems to be a straight line on the real one from probably about just aft of the cockpit.

It is "almost straight line" what I have seen from these photos.

https://www.airliners.net/photo/USA-Air-Force/Lockheed-SR-71A-Blackbird/5180735

 

https://www.airliners.net/photo/USA-Air-Force/Lockheed-U-2D/5451935

 

Serkan

Edited by Serkan Sen

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On 9/25/2019 at 9:14 AM, Serkan Sen said:

Another solution is to add an 6.15mm insert to the end of nose part and reshape only chine and nose cone. This requires reinforcements at nose and chine area from inside before starting reshaping.

Following the second option I have repositioned the drawings and kit parts to mark the chine and nose shape modification areas:

1063.jpg

1062.jpg

 

Next step is to start modifications.

 

Serkan

 

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Before the butchery starts the first step is to remove the pitot tube and put it aside before it breaks off.

1064.jpg

 

And then using drawing from previous post I have printed out a template to mark the area to be filled with casting resin. I use modelling clay to make temporary mold:

1065.jpg

 

And here the PUR was casted:

1070.jpg

 

And few hours later the resin was hardened enough to remove modeling clay:

1071.jpg

 

The clay can be easily removed without leaving any residual:

1072.jpg

 

To be continued 🙂

 

Serkan

Edited by Serkan Sen

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You probably already know, but Master-Model makes a very nice replacement pitot tube for the Blackbird. And, Metallic Details have a beautiful, if somewhat pricy, landing gear & gear bay set that I wish I’d had when I built my SR-71. 

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4 hours ago, billn53 said:

You probably already know, but Master-Model makes a very nice replacement pitot tube for the Blackbird. And, Metallic Details have a beautiful, if somewhat pricy, landing gear & gear bay set that I wish I’d had when I built my SR-71. 

Hi Bill,

Of course it would be nice to have these sets on my all scheduled builds but it is a bit more than pricey 😞.  It costs around 50-55€ per aircraft.

 

Maybe I can think about pitot tube replacement if I can get a good price from my supplier for multiple orders.

 

Serkan

 

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1 minute ago, Serkan Sen said:

 

Of course it would be nice to have these sets on my all scheduled builds but it is a bit more than pricey 😞.  It costs around 50-55€ per aircraft.

 

Fortunately for me, I only have one more Blackbird I want to build (YF-12) so my bank account won’t be totally devastated. 

 

Also, I was sent on a short notice business trip this week (I’m in Los Angeles now) and haven’t been able to get to the Space & Rocket Center for photos or measurements. 

 

Bill

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Now it is time for first "metal" cut...

Fortunately the parts are composed of plastic and resin instead of "titanium". Therefore I don't expect any problem with cutting and shaping tools 🙂

1073.jpg

 

The chine shape is marked with red line

1074.jpg

 

Here is the comparison of original and reshaped chines:

1075.jpg

 

The cross section profiles have to be corrected as well.

1076.jpg

 

The section shape has been corrected only on starboard side in the above right image.

 

Here is the view from inside:

1066.jpg

 

Serkan

 

 

 

Edited by Serkan Sen

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I would never have thought of using resin on the inside, now I have a new tool in my toolbox!

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48 minutes ago, billn53 said:

I would never have thought of using resin on the inside, now I have a new tool in my toolbox!

I use PU resin in kitbash very often. It has many pros and only one con:

+ one can fill larger volumes very quickly

+ has very low viscosity. Therefore fills any cracks or gaps (proper masking/sealing is necessary to avoid leakage)

+cures very fast (20mins to 3 hours depending on PUR type)

+ mechanically machining is possible (drilling, sawing, milling...)

+ with enamel paints (best with Humbrol paints) and others can be casted in any color.

+ with water clear resin the clear parts can be duplicated (see my Su-27IB)

 

- it does not stick the plastic well especially if the surface is smooth. But this is indeed also a "pro" because this lets creating positive and negative molds from existing kit. The chemicals may leave some residuals or etch the plastic surface but most of the time this is not significant. To glue the resin to plastic super glue does this well.

 

Serkan

 

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To check the modified contour shapes and the original form I have used thin self adhesive strips:

1067.jpg

1068.jpg

 

And here is the reshaped new nose versus the original kit one:

1077.jpg

 

The black part of the new nose looks like in YF-12 shape doesn't it? 🤔

 

Serkan

 

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Fantastic work Serkan.

 

AW

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28 minutes ago, Andwil said:

Fantastic work Serkan.

 

AW

Thanks AW,

I am trying my best to build these legendary, beautiful and unique aircrafts using the best material and reference available (of course with the help of all of you 🙂 )

Serkan

 

 

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Next step will be the lower surface mod and extending the upper part by 6.15mm

1078.jpg

 

Serkan

Edited by Serkan Sen

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Nicely done! I too would never have thought of resin inside. I always fill the inside with Miliput, which sticks well and is also sandable/drillable.

 

Ian

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1 hour ago, limeypilot said:

Nicely done! I too would never have thought of resin inside. I always fill the inside with Miliput, which sticks well and is also sandable/drillable.

 

Ian

Thanks Ian,

Yes Milliput putty is a great product to repair or fill and cures within few hours sets like "rock". Also it is highly adhesive to most materials.

 

On the other hand PUR is liquid with very low viscosity like milk and gets the shape of its mould with very fine details. It fills any gap or crack perfectly. It can be worked mechanically, drilling, sanding, frasing etc. It is also elastic as the injected plastic parts. But it doesn't stick to surface very well which is good for casting indeed. The casted part can be glued using cyano adhesives perfectly. Also it is cost effective. (I have enough amount of various resins for casting purposes in my workshop i.e. basement)

 

The only drawback of resin (especially PUR) is the limited shelf life (12 months).

 

The both products are great products and offers wide range of application options.

 

Serkan

Edited by Serkan Sen

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Aah, I guess my resin is no use any more then! I don't need it often, so it's at least 3 years old!

 

Ian

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On 9/27/2019 at 2:13 AM, billn53 said:

Also, I was sent on a short notice business trip this week (I’m in Los Angeles now) and haven’t been able to get to the Space & Rocket Center for photos or measurements. 

 

Bill

If you have any free time during your trip, be sure to stop by the California Science Center. It's not accessible for measurements but they have an A-12B on outdoor display - and the indoor exhibits include the sole remaining F-20, a T-38, and the space shuttle Endeavour.

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1 hour ago, limeypilot said:

Aah, I guess my resin is no use any more then! I don't need it often, so it's at least 3 years old!

 

Ian

I would not risk any work using it (you can ask manufacturer for its shelf life).

I had very bad experience with the old resin. After casting everything looks ok but when the temperature a bit increases the casted parts starts to "sweat oil". You can see here the complete story I had with old resin:

Serkan

 

 

Edited by Serkan Sen

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The upper nose half was extended by adding the rear part of another Blackbird kit:

1079.jpg

1080.jpg

1091.jpg

1092.jpg

 

Next I will start the nose lower half.

 

Serkan

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Here is the Revell/Monogram vs Italeri/Testors lower fuselage lower part comparison:

1093.jpg

 

Revell/Monogram kit has definitely better/much more realistic lower fuselage shape and nose landing gear well details than Italeri/Testors kit.

 

The lower fuselage was splitted through the panel line between NLG well and front camera bays.

1094.jpg

1095.jpg

 

The 6.15mm insert will be placed here.

1096.jpg

 

The Italeri/Testors kit NLG well will be replaced with Revell/Monogram one.

 

First remove the well from Revell part:

1097.jpg

 

Also remove the simple NLG well from Italeri part. Here is the result:

1081.jpg

 

The NLG well in above photo is from Revell kit.

 

To be continued 🙂

 

Serkan

Edited by Serkan Sen

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Not to be negative but I thought the A12 was shorter than the SR71 by 6 feet. A12 was 101 feet long, Sr71 was 107 feet long

Edited by neil5208

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1 hour ago, neil5208 said:

Not to be negative but I thought the A12 was shorter than the SR71 by 6 feet. A12 was 101 feet long, Sr71 was 107 feet long

This is a very good  question.

 

6 feet corresponds to 1 inches (25.4mm) in 1:72 scale. The tail cone extension is around 2/3 inches (17mm) in SR-71A. The difference is on forward fuselage area is only 1/3inches (8.4mm).

 

Before starting this kitbash I made first top and side view drawings based on photos available on web as I have already shared in my previous posts here. At the beginning I was really suspicious about the A-12 dimensions but now I am very confident with my drawings in 1:72 scale.

 

I believe that Italeri/Testors kit was based on A-12/M-21 reference materials rather than SR-71 at that time. Revell/Monogram kit is a bit longer than this one. I will find some comparison photos of both kits and post here.

 

All above conclusions are based on my engineering judgement (with the hope that they are not wrong) 😁

 

Serkan

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Just now, I have measured the overall length of modified model including the pitot tube and it is 430mm. When converted to full scale it makes 101.5 feet.

 

In other words 101 feet makes 427.6mm in 1:72 scale.

 

I need to shorten the front fuselage by 2.4mm 🤔

 

Or simply keep it as is?

 

Serkan

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2 hours ago, Serkan Sen said:

Just now, I have measured the overall length of modified model including the pitot tube and it is 430mm. When converted to full scale it makes 101.5 feet.

 

In other words 101 feet makes 427.6mm in 1:72 scale.

 

I need to shorten the front fuselage by 2.4mm 🤔

 

Or simply keep it as is?

 

Serkan

You are within about 1/2 percent, that’s very good. I say keep it, unless it starts to bug you. (That’s coming from someone who built Italeri’s B-58 Hustler, which is about a full inch too short)

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I didnt know about the exteneded tail section, your research is more in depth than mine. Just didnt want you to make a mistake on such a good conversion so far

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