CB-25J Mitchell

Started by George R Blair Jr · 230 · 1 year ago · 1/48, B-25J Mitchell, CB-25J, MATS, Monogram
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    Stephen W Towle said 1 year, 8 months ago:

    George R Blair Jr (@gblair),

    Glad your doing 1/48 maybe not the gentleman's scale but, you can have, hold and see what your doing. Monogram captured the look and soul of this a/c. One thing I learned about the exhaust systems is through reading restoration projects of B-25s being back dated to Warbirds. The give away or you know by looking at a Warbird that it was either a trainer or had been bought for agricultural uses or fire fighting by the exhaust set up. I can think of one museum that restored their aircraft back to individual pipes for each jug. One mag had a story on how you can tell a B-25 instructor from all the rest . They talk loud and are hard of hearing. Being stuck between two radial engines does that. I believe, North America went to individual pipes for the speed advantage, early C and D had the collectors. I will be following your adventure and discoveries in B-25 history and modeling with interest.

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    Walt said 1 year, 8 months ago:

    Nice work removing the armor plating, and exhaust fairings. Have you looked into the 3D printed decals for interior details? Although I like the idea of scratch building too. You are definitely making some nice progress.

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    George R Blair Jr said 1 year, 8 months ago:

    Thanks, Stephen (@stephen-w-towle). I have been doing some more reading on the exhaust systems. It seems that going to individual exhausts increased the drag and slowed the top speed almost 10 knots. They streamlined the exhaust covers and gained some of that back. I suspect that using a collective exhaust gave some of that speed back. I also read that the Canadians used a double collective exhaust system on some of their B-25s, and they had two large exhausts on the outboard of each engine. Now that I am clued into the different exhaust systems, I have been noticing that many of the warbirds have the modified exhaust system. I have read that many of the B-25 warbirds came from former trainers. I have the same hearing problem from flying C-141s for 20 years. My hearing in my left ear is much worse than my right ear, even though we always wore headsets that supposedly provided hearing protection.

    Thanks, Walt (@luftwaffe-birdman). I have enjoyed this conversion, so far. I belatedly decided to get some interior stuff, so I have an Eduard PE set coming, as well as an Eduard 3D set, and another 3D set from Kits-World. I didn't order them until after I had already started the conversion. I am stalled on the interior until I can see what each set has, then I can build up some of the interior with the sets as a guide. I plan to use one of them for this conversion, and save the others for later conversions.

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    Stephen W Towle said 1 year, 8 months ago:

    Found this on another form. Not modeling related but, it gives a rational for the individual exhaust set of some B-25s.

    "Those bumps are very definitely fairings over individual exhaust stacks, which is the correct configuraton for a war-time B-25. Most of the Mtichells flying today have been converted to the later TB-25 configuration, which uses a collector ring and single exhaust stack outboard, but they still retain the individual stacks on the inboard side. A lot of this had to do with getting carburetor heat, as the wartime birds simply opened a scoop on the top of the nacelle behind the two top stacks. This sure ducted warm air into the carbs, but it was a little shy on oxygen, so the resultant power loss was enormous. With the collector ring and the stack, carb heat could be obtained in a more traditional way with a muff over the exhaust pipe to heat ambient air."

    Which raises the question of the inboard single exhaust fairings placement on some trainers. I've included a photo of Miss Mitchell. I'll stop stealing your thunder (research) George.

    1 attached image. Click to enlarge.

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    George R Blair Jr said 1 year, 8 months ago:

    Thanks for the info and photo, Stephen (@stephen-w-towle). No thunder to steal. I think we are all learning the finer points of late B-25 exhaust at the same time. Notice in the photo that the individual exhaust fairings extend past the midline, so there is at least one and maybe two exhausts on the outboard side of the bottom of the engine. Seven of the exhaust fairings in the Revell kit are separate pieces, which should make it easier to add the fairings where they are needed.

    1 attached image. Click to enlarge.

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    George R Blair Jr said 1 year, 8 months ago:

    The Eduard interior set finally got here. It is designed for the HK B-25J, so it doesn't necessarily match the elderly Revell interior. I have been adding the interior structure using strip plastic, as well as working on the seats and instrument panel. I used some thick acrylic putty to form the seat backs, and removed the seatbelts from the bottom of each seat. Many of the interior photos of post-war B-25s show armrests have been added to the seats. We had similar armrests in the C-141. Some pilots preferred not to use armrests because they somewhat limited your arm movement on the yoke. On the other hand, an armrest allowed you to make very small corrections to the yoke, which made for a much smoother flight. I always preferred to use the armrest except during approach and landing, which sometimes required larger inputs due to the slower speed. Thanks to the work getting the interior spaces detailed, I try to limit my sessions on the interior to an hour at a time.

    9 attached images. Click to enlarge.

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    Spiros Pendedekas said 1 year, 8 months ago:

    Amazing job so far, my friend @gblair! The interior shines already with all the extra job being performed.

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    Tom Cleaver said 1 year, 8 months ago:

    The individual exhausts were adopted when the B-25s were used for night bombing in the middle eastern campaign in 1942. The single exhaust couldn't be shrouded and was so visible it gave gunners on the ground an easy target. The individual exhausts shrouded the exhaust so it wasn't so visible.

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    John vd Biggelaar said 1 year, 8 months ago:

    Great scratch building improvements on the interior, George @gblair
    Together with the Eduard set it will look impressive.

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    George R Blair Jr said 1 year, 8 months ago:

    Thanks, Spiros (@fiveten) and John (@johnb).

    Thanks, Tom (@tcinla). That makes sense. I have seen photos of B-25Ds with the individual exhausts, but the earlier versions seem to have had the collected exhaust.

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    capt. R said 1 year, 8 months ago:

    Great work on cockpit!

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    George R Blair Jr said 1 year, 8 months ago:

    Thanks, Bernard (@lis). Nothing too challenging, so far.

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    George R Blair Jr said 1 year, 8 months ago:

    I think I have all of the interiors ready to go. I added the inner framing to the cockpit and nose section, then added the boxes for the instruments. When everything was done, I wanted to use flat black as the starting point for painting the interior. I sprayed Vallejo flat black from a spray can over to bring all the different parts together. This will also serve as a good start for pre-shading. I hope to paint the green interior tomorrow. Cheers.

    5 attached images. Click to enlarge.

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    John vd Biggelaar said 1 year, 8 months ago:

    All those details look amazing, George @gblair
    Those cushions make those seats look very realistic.

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    George R Blair Jr said 1 year, 8 months ago:

    Thanks, John (@johnb). Acrylic putty is great. You let it dry, and then you can reshape it or remove it use water or alcohol. I discovered it to fill seams, but it works great for other stuff.