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YB-40 Gunship Project Started


ewahl
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Ever since I purchased the original Revell kit of the Boeing B-17F "Memphis Belle" I've been wanting to attempt its conversion to the YB-40 Gunship. I've accumulated references and aftermarket sets (unfortunately, they are almost all made for the Monogram B-17G). Paragon issued resin conversion sets in both 1/48 and 1/72 scales, so I bought them both in case I need or want to go to the Academy or Hasegawa B-17F for a 1/72 project.

 

The engine fronts and cowl flaps are resin from the Quickboost line for the Monogram B-17G. The pour blocks were huge, covering the entire back faces of each part, which required tedious sanding, scraping, and sawing to remove on the eight pieces. The Revell B-17F cowls had the flaps molded on, so I had to cut them off with the razor saw. The Monogram kit does not have the cooling flaps on the cowl piece.

YB-401.jpg

 

The four vent holes in the upper wing surfaces behind each engine are molded solid; you have to paint them black on the vertical surfaces. I decided to open them up with a #11 blade tip, dental scraping tool, and tiny files. To my great annoyance, the plastic is very HARD, which made the scraping and digging take much too long. Compare the before and after look.

YB-402.jpg

 

Of course I have to get the kit with the deformed, warped lower right wing. This is a major setback because the engine housings are tilted downward in addition to the wing itself having a sagging appearance. I don't know if any glue will completely absorb the stresses if I just try to squeeze and close the gaps all along the front of the wing and two engines. I could really use a replacement part (maybe Revell can ship me one).

YB-403.jpg

 

YB-404.jpg

 

Here the Quickboost resin cowl flaps are on the left wing's engine fronts. The green plastic has to be cut back to the face of the piece so the engine front can be glued on.

YB-405.jpg

 

The YB-40 was the first B-17 variant to have the staggered waist gunner windows, with each station boasting twin-50s. This is one feature of the YB-40 experiment that eventually wound up on the B-17G production lines. The Paragon instructions gave the precise measurement for moving the opening forward on the right fuselage. I masked and scribed through the thick plastic all around the new opening, and I used the removed plug to fill the old opening. The plug fit so well that I only used gap-filling super glue and some Mr. Surfacer to fill in the outline. Using the plug also has the benefit of matching the inside surface of the fuselage as well. I will have to add some interior structure to each fuselage half opposite the open windows. I tried to make the True Details Waist Gunner's set for the Monogram B-17G kit work here, but I am really dissatisfied with the quality of the fit of the resin parts as well as the texture of the resin material itself--too hard and brittle with awkward pour blocks.

YB-406.jpg

 

YB-4010.jpg

 

The second top turret from a Martin B-26 was added where the radio compartment used to be. The fuselage was modified to make it fit. The Paragon kit has the resin replacement part. The piece was sized to match existing panel lines on the Revell kit, so masking the cut lines was easy and correct. The piece will need shims in the edges to make a tight fit and to align the surfaces.

YB-407.jpg

 

Another correction is that the two large nose windows have to be closed up and replaced with the smaller windows. The YB-40 had the B-17E small nose windows, and some were later retrofitted with these bigger ones. There is an astrodome on the top that must be added, and the small top window near the cockpit must be plugged. I have the True Details sets for the cockpit and the bomb aimer's stations, but again both are made for the B-17G kit and suffer from the same poor quality resin and fit, not to mention that they are for the large front windows. Some new interiors will have to be scratchbuilt.

YB-409.jpg

 

This pretty well brings you up to date. Many more hours will go into this one.

 

Comments an suggestions are always welcome.

 

Ed

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Very interesting project, and some first class old fashioned modeling to get things started. Do you have a source for the twin .50s, or will you be kitbashing/scracthbuilding those? I look forward to seeing more progress on this!

 

GIL :smiley16:

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Very interesting project, and some first class old fashioned modeling to get things started. Do you have a source for the twin .50s, or will you be kitbashing/scracthbuilding those? I look forward to seeing more progress on this!

 

GIL :smiley16:

 

The Paragon conversion resin set has the twin .50s and dual ammo belts for each gunner. They are not very detailed, so I may add some to the gun bodies. The barrels throughout the build for all guns will be replaced from Quickboost sets.

 

Ed

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Ed,

Might seem stupid but have you thought about clamping the wings and letting it soak in a bathtub with hot water???? Also, if the Quick Boost set is designed for the Monogram kit and the flaps are spereate, why does Quick Boost include them in resin? Are they better detailed? Different number of flaps??? I have seen these and thought about getting them for my B-17.

 

:Smile_sceptic:

Edited by Mark Aldrich
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To my knowledge, no 1/48 B-17 kit includes separate flaps, or any other separate control surfaces for that matter. It's pretty easy to build them yourself, but I'm sure the resin flaps are more accurate and better detailed, if your willing to trade money for time! And ain't that almost always the case?

 

GIL :smiley16:

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Gil,

The engine themselves look so much more detailed in the pictures I have seen! I just didn't understand the purpose of the flaps. I could understand it if they were opened or maybe there were 18 flaps around and the Monogram kit only came with 17. That's the probelm with being a TreadHead.....not all the fired up about aircraft knowledge.

 

:Smile_sceptic:

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If you look carefully at the Quickboost resin cooling flap pieces in the first photo, you will see that I used a thin razor saw to cut between the cooling flaps along the scribed lines that originally separated them. Before I did the cutting, I shaved off the resin around the entire ring on the back side to create the look of thin sheet metal flaps (similar to shaving off/thinning the trailing edges of wings).

 

The Monogram B-17G kit combines the engine front with the ring of cooling flaps as a single piece, and the cowl does not have those flaps. The Revell B-17F kit is just the reverse--separate engine front and a cowl with cooling flaps. Regardless, the Quickboost engine fronts are much better than either the Revell or Monogram offerings, and the Quickboost cooling flap ring is a separate piece. It requires the surgery to use Quickboost engines and cooling flaps with the B-17F/YB-40.

 

Quickboost and Monogram both display the cooling flaps in the closed position; i.e., flush with the cowl surface. Revell molds the cooling flaps partially opened out, so they have a tapered cone appearance. You can see that from the flap rings in the top photo.

 

Mrs. Treadhead has the Monogram B-17G version, so the Quickboost set is recommended for improving what the kit provides without the need for any surgery. The real work is removing the resin pour blocks from the eight pieces. Do that work first before you attempt to paint and detail the parts.

 

Ed

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  • 4 months later...

Five months have now passed without much to show. I felt the Quickboost engine fronts calling me to add details. I was most concerned about the ignition ring and plug wires that were not included. I found a PE set in the old Monogram/ProModeler B-17G kit (part of the kit and not aftermarket), but I did not want to remove that PE from the kit and thus make it incomplete. At the Nationals I found an Eduard PE set for about $10, so I bought it. The fret includes the ignition ring, two wires per cylinder, ID plates for the front housings, and replacement cooling flaps.

 

In this photo you can see the four steps I used for the engines, from L to R:

1. Paint and detail the basic Quickboost engine front's cylinders and gear housings.

2. Add two pushrods per cylinder. The top and bottom holes are in the casting, but I used a drill bit on them to open them up a bit. The push rods are 24-guage wire from a spool.

3. Add the ignition ring and wires and ID plates from the PE fret. I gave the ignition ring some depth by super gluing an Evergreen strip to the front of the PE ring. Painting the ring, connectors, and wires completed the look.

4. Add an Evergreen strip around the perimeter of the cylinder tops to simulate the shape of the rocker covers that almost look like a solid ring when in place. This detail almost disappears under the cowling, so the "correct" shapes are not needed. Reference photos show the rocker covers in aluminum, black, and red, so take your pick. I chose aluminum.

YB-4012.jpg

 

This photo shows the result when an engine cowl and prop are placed over the detailed engine. The Eduard PE fret shows what I worked with. On engine #4, the cowl fits over the rocker cover ring like a glove.

YB-4014.jpg

 

The Quickboost engine front has a smaller diameter front gear housing than does the Monogram B-17G kit engine front, for which the Eduard PE is designed. This difference makes the ignition ring look slightly too large on the Quickboost engine. I'll have to live with it.

 

This is my first experience with detailing an aircraft engine, and I just am dumb enough to pick a model that requires four of them done identically. As you see, only one is completely done. It's time to work on the other three to finish them up.

 

Ed

Edited by ewahl
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I follow what you're saying Ed, and look forward to seeing the pics when you get the posting bugs out. I've used the Quickboost engines a couple of times, and decided NEVER again! The idea of buying something molded so nicely but without the push rods baffles me!

 

GIL :smiley16:

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I follow what you're saying Ed, and look forward to seeing the pics when you get the posting bugs out. I've used the Quickboost engines a couple of times, and decided NEVER again! The idea of buying something molded so nicely but without the push rods baffles me!

 

GIL :smiley16:

 

Hi, Gil,

 

Thanks for the comment. I was not aware that the photos did not attach properly until I read this. I went back into my post and deleted the photos (which I could see on my screen). It took two tries on each one to get them back in as edits. Yesterday, when I originally posted the whole thing, the Forum would not save the post. For ten minutes I looked at a message that said, "Saving post ..." This froze up the majority of the function keys, and I finally had to resort to going back to the Home page. That seemed to force the stuck Save Post command and put it into the thread. It was there when I came back to it.

 

If you do not see the photos now, please let me know. There would be something else wrong if all you see is the box with the red X.

 

Thanks again,

 

Ed

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