Official FlightLine 1600mm B-25J Mitchell PNP Thread

[davegee]

I did some more test flights on my B-25J today. Did one flight with a bomb drop of 4 printed bombs from a bomb rack designed by Fast N Light and another person he knows where the original idea might have started. In any event, this was the best bomb drop so far, the orange painted bombs dropping in a line in a very realistic manner, from what I could tell with my peripheral vision as I concentrated on not crashing the airplane from a pretty low altitude of about 20 feet above the ground in level flight. I was able to retrieve all four bombs afterwards, undamaged.

At some point, I'll probably have someone who comes out to the field who can take some photos of the bomb drop to better judge how they are doing. I'm thinking this setup is pretty realistic.

The next step is to work on a scratchbuilt replica of the venturi tube that goes underneath the forward fuselage of the aircraft. This tube helped remove gun gas fumes from the nose section in flight. I'll take some more pics as I proceed with it. Not much to go on, but I think I can come up with a fairly believable replica of this part that was on planes like Cactus Kitten that I am working on.

I wanted to improve my landings, mostly due to the Robart nose tire not staying on the printed scale wheel properly. Using more E6000 for one wheel, and clear Gorilla Glue for another nose tire, I think I have that problem licked, and touchdown and rollout is now much more realistic and less jarring to the plane than before.

[davegee]

This is the factory drawings of the fuselage that the cross sections are related to. I don't think it has been printed anywhere else before. If it had, the existing three views and profiles of the B-25 would be more accurate. For the H & J models the horizontal stab was raised 7" and the fuselage widened starting at station 558.

Those are a real historical treasure, Charlee! Thank you for sharing them!

Davegee

[Charlee]

This is the factory drawings of the fuselage that the cross sections are related to. I don't think it has been printed anywhere else before. If it had, the existing three views and profiles of the B-25 would be more accurate. For the H & J models the horizontal stab was raised 7" and the fuselage widened starting at station 558.

[davegee]

All the B-25Ds and B-25Js were built at the NAA Fairfax factory, ultimately reaching production of over 300 aircraft a month. The B-25's outer wing panels where made by Fisher Body in Memphis.
The tube has a visible break at the front of the nose gear door, with the rear section of the tube being attached to the door. The nose gear didn't retract straight back. It was angled so that the nose wheel rested in the right side of the fuselage when retracted, which is shown in section D-D below. That is why the blister on the door is off to the side.

Great info, Charlee! That confirmed my questions on how the venturi gun exhaust tube lines up per the period pic I have of Cactus Kitten and other good plastic model instructions I found online.

First, thanks for confirming the separation line of that venturi tube at the front of the nose gear door. Obviously, they had to have a break in it somewhere to work the nose gear and its door. So all that makes sense now.

Second, the blister molded into the nose gear door on the Flightline B-25 places it down the centerline of the aircraft, which is incorrect. That's what mystified me until you offered your explanation with supporting shop drawings that the nose gear wheel is canted off to the side of the airplane when the gear is retracted, thus the need for the blister on the side of the nose gear door. That allows for the venturi gas tube to line up nice and straight from beginning until it goes over that blister and the exit point of the tube.

I will modify another gear door that I am expecting to arrive from MRC later this week. It will be changed so that it is correct with the drawings and pictures.

Thanks again for the great info. I appreciate your offering your expertise on this historic aircraft. I was taken with the genius of the designers to use venturi tube action to clear gun gases out of the nose of the plane. To me, it's worth the extra time and effort to fabricate one for my plane.

Best,

Davegee

[Charlee]

All the B-25Ds and B-25Js were built at the NAA Fairfax factory, ultimately reaching production of over 300 aircraft a month. The B-25's outer wing panels where made by Fisher Body in Memphis.
The tube has a visible break at the front of the nose gear door, with the rear section of the tube being attached to the door. The nose gear didn't retract straight back. It was angled so that the nose wheel rested in the right side of the fuselage when retracted, which is shown in section D-D below. That is why the blister on the door is off to the side.

[davegee]

The Callie nomenclature seems to be pretty generic and is lacking many items, especially the aircraft data stenciled on the left side behind the cockpit. Norm "Jim" Avery was a good friend and a draftsman at NAA. He gave me a copy of the print used by the factory for placing the nomenmclature for the B-25H, which was essentially the same used on the B-25Js made in Kansas City.

Those are great, Charlee. I should be able to cross-reference your drawings with what Callie supplied me to get them in the proper spaces on the airplane.

I have a question for you regarding the venturi tube that you correctly told us was in that picture of Cactus Kitten during WWII. I know there is a long tube that starts near the front of the bottom of the fuselage, continues over the nose gear door, and then ends with a little curve over a blister near the back end of the nose gear door.

I'm assuming there must be a break in that tube, probably at the forward end of the gear door so that the door is free to move open and closed in sequence with the nose gear. Do you agree that there had to be a break in the tube so that the gear could cycle up and down with the gear door? That's the only way I see that happening unless you have another explanation.

Thanks for including your nomenclature files in Hobby Squawk!

BTW: In the late 1970s, I used to fly DC-8 freighters into the Kansas City Fairfax (KCK, if I remember correctly) where they used to build the B-25s. We were bringing in car parts for the assembly line of whatever they were building in there, but I think that is the same facility that used to build the B-25s in WWII. I had forgotten about that until I started working and researching this model project.

Cheers

Davegee

[Charlee]

Not at all. At the same time could you show them these for my PBJ?

[Elbee]

Charlee that is great stuff . Would you mind if I show these to Callie Graphics? Best, LB

[Charlee]

The Callie nomenclature seems to be pretty generic and is lacking many items, especially the aircraft data stenciled on the left side behind the cockpit. Norm "Jim" Avery was a good friend and a draftsman at NAA. He gave me a copy of the print used by the factory for placing the nomenmclature for the B-25H, which was essentially the same used on the B-25Js made in Kansas City.

[davegee]

Got four flights in this morning on my B-25J Cactus Kitten, making a total of 14 so far.. Today's flight was testing the feasibility of dropping parachutes from a low altitude. For this test, I found some toy paratroopers on Amazon, and put two of them in the bomb bay. Went pretty well. I'll do a few more tests with these "brave" paratroopers, but then will make up some somewhat scale looking white parachutes and a parafrag bomb as they used in combat missions on enemy shipping and airfields. I'll probably eventually drop about 6 of these out of the bomb bay at low altitudes, about 15-20 feet above the ground to simulate the height that the real ones flew from to drop these bombs.

The new tires and wheels worked pretty well, especially the main gear. The nose tire started coming off of the wheel, causing some erratic behavior rolling out on the runway. No damage done, but I need to take the nose wheel apart and add more robust glue to be sure that doesn't happen again. That's my bad, and we'll see how it goes next time.

I'll attach a few pics after the flights today. You can see the scale wheels and Robart tires which I love, and one shows the paratroopers posing next to the airplane after the event.

I have ordered some materials to make a fairly scale venturi tube that goes on the underneath side of the fuselage. This was to vent gun gases from the nose area due to four guns (or more, sometimes) being up there. The fumes were sucked through the floor into the venturi tube and then out of the airplane.

Last, if you look carefully on the front of the right wing, you might be able to see the scratchbuilt pitot tube that I made out of aluminum. Done a bunch of these on other airplanes so I can whip these up pretty quickly. This one is all aluminum construction and I was satisfied how it came out.

Cheers

Davegee

[davegee]

Dave, and that is all that matters. Best, LB

👍👍👍

[Elbee]

...agree with you! There is a satisfaction inside of each of us who endeavor to think outside the box a bit. Most people won't see the difference, but I WILL!

Dave, and that is all that matters. Best, LB

[davegee]

Dave, I, for one, have found 'artistic license' trumps 'authenticity' when cost is a major production consideration.

But it's fun to make the airframe your own by changing all the flawed bits and pieces that catch your eye.

That's scale modelling, right?

Great modification and looking forward to seeing how you handle it.

Best, LB

Hi Elbee: Totally agree with you! There is a satisfaction inside of each of us who endeavor to think outside the box a bit. This venturi tube was genius on the part of whoever designed and fabricated it for use with the B-25 gunships in the South Pacific in WWII. It is worth the extra time and trouble to add it, as best as I can do, to this model. Most people won't see the difference, but I WILL!

Cheers

davegee

[Elbee]

...drawings that confirm that Flightline designed the nose gear door with that blister in the wrong spot...the tube runs over that blister and exhausts out the back of the tube. A bit of a hassle, but worth doing since it is definitely on that photograph of Cactus Kitten.

Dave, I, for one, have found 'artistic license' trumps 'authenticity' when cost is a major production consideration.

But it's fun to make the airframe your own by changing all the flawed bits and pieces that catch your eye.

That's scale modelling, right?

Great modification and looking forward to seeing how you handle it.

Best, LB

[davegee]

https://www.youtube.com/watch?v=nLMDIlxUa58


Mitchell Mob,

Start up and take off scene of a gaggle of B-25s from the movie "Catch 22".

Big Fun if you are a fan of either the movie or the airplane.

Best, LB

Great scene!!!👍👍👍

BTW, the plan for the venturi tube underneath the bomber is starting to become a little clearer now. I found some drawings that confirm that Flightline designed the nose gear door with that blister in the wrong spot! That's why the tube wasn't lining up properly. So, I will have to modify that door, removing the blister, and taking another door cutting the blister off of that door and putting it over to the right so the tube runs over that blister and exhausts out the back of the tube. A bit of a hassle, but worth doing since it is definitely on that photograph of Cactus Kitten.

Cheers

davegee

[Elbee]

https://www.youtube.com/watch?v=nLMDIlxUa58

Mitchell Mob,

Start up and take off scene of a gaggle of B-25s from the movie "Catch 22".

Big Fun if you are a fan of either the movie or the airplane.

Best, LB

[Elbee]

Great details, Dave, and well executed. Best, LB

[davegee]

Hey Dave, It was Charlee not me that gave you the answer.. But it does make sense. Thanks, Charlee. Best, LB

Hi Steve: yes, my answer was directed at Charlee who answered the question for both of us as to what that tube was on the bottom of the Cactus Kitten. Makes perfect sense, now. If I can get a bit more info on that tube (dimensions, etc.) I might try adding that onto my model. Perhaps Charlee could furnish any info he knows about this interesting mod? I'll dig in myself to see if I can find anything more on it.

Cheers

davegee

[Elbee]

Wow, good answer! was this a "field mod": or did Mitchell's start being manufactured at the plants in the USA with these mods?

thanks for the answer Elbee and I had been scratching our heads over!

Davegee

Hey Dave, It was Charlee not me that gave you the answer.. But it does make sense. Thanks, Charlee. Best, LB

[davegee]

I got my main wheel tires in the mail today from Robart. They fit perfectly onto the printed wheels I got the STLs from Fast N Light. The moment of truth was when I put them on the plane and retracted the gear to see if they would fit! They did, no problem at all!

For some reason my order didn't include the scale nose wheel tire with the diamond tread, so I hope that will come in the mail in the next few days.

I'll attach a pic of a real B-25 (contemporary) I got off the internet, and my tires with the scale printed wheels. Just for grins, I made up a scale metal valve stem for inflating the main tires. I believe the red rectangle painted or taped onto the wheel/tire is to see if there is any slippage movement between the tire and the wheel while it is in service. If you see them off center from how they should be, that means there is some movement of the tire on the wheel, and the seal might be compromised or damaged. That's my take on it, anyway.