This is a list of helpful tips for the Top Flite 1/9th B-25 Mitchell ARF:
These are some of the things I have learned after building and flying my own B-25 on my own time after work. On my own time without deadlines, I am able to devote more time, use my creativity and let my ideas flow to come up with even more improvements and suggestions that may not be appropriate for or fit in the instruction manual without making it hundreds of pages long. I am sure many of you will develop many more ideas that we can all use:
1. Always remove the screw-in tail-gunner machine gun barrels and the nose-gunner canopy when carrying/transporting the model. This makes the fuselage much shorter so it is easier to handle and the guns cannot be broken off.
2. When at the flying field, place barriers (such as your flight box, Tx case, soccer cones, etc.) in front of the nose-gunner canopy and behind the tail guns. This will protect them from getting broken off when spectators or other pilots walk by or stand near the model.
3. For planes with retracts, never run the engines without the gear locked and pressurized. Otherwise, without pressure, engine vibration may cause the gear to collapse. Alternately, the engines could be run with the fuselage resting in the included stand.
4. The best way to carry this plane is while it is not in its stand. This way both hands will be free to hold the model. But to make transport even easier, purchase a second stand separately (TOPA1721, retail price = $9.99). Keep one stand in your vehicle and another stand on your workbench or wherever you store the model. Then, all you have to do is transport the model from one stand to the other without making additional trips to retrieve the stand.
5. It will be easier to add the “stars-and-bars” decals to the fuselage BEFORE gluing on the waist guns/waist gun windows.
6.
(Photo 1) Rather than permanently gluing on the top turret, use small wood screws to hold it on. This way, the turret may be removed if the guns or barrels ever require repair. #2 screws are suitable, but if you can find even smaller hobby wood screws those would be better. (Try
www.microfasteners.com)
7. For those using Robart retracts, in some cases the nylon clevis on the outboard pushrod for the main landing gear doors (photographed on page 18, step 16) may rub against the aft end of the air cylinder as the bellcrank lever rotates downward to pull the doors closed. If this is the case, the lever may be moved aft slightly (approximately 1/16” should do it) by placing a washer made from 1/16” plywood (or regular #4 washers) under the lever. This will move the lever—and the clevis attached to it—away from the air cylinder to provide the required clearance.
8. There are probably dozens of ways to enhance the scale appearance of this model. One way would be to cut the floor out of the tail-gunner cockpit. Then, more details may be added down inside the cockpit and inside the fuselage. If you don’t wish to do this immediately, but plan to add details later, rather than permanently gluing on the tail-gunner canopy with CA, tack-glue the canopy with a few dabs of R/C 56 or RTV silicone. Then, the canopy can be removed later when you are ready to add your details in the tail-gunner cockpit.
9. Another suggestion regarding the levers that pull the gear doors closed; The thin, plastic washers (step 5, page 16 and step 1 page 29) may not be required. Using the washers may increase the thickness of the bellcrank levers and nose gear door lever so that they do not “float” on the brass bushings. Try mounting the levers without the thin plastic washers first. If, when you tighten the screws that hold on the levers the levers rotate smoothly, leave the washers out.
10. When finally ready to fly your B-25, make certain you have COMPLETE CONFIDENCE in your engines. This will reduce the anxiety of your first flight allowing you to devote all of your concentration to flying the model without being distracted by the worry of an engine quitting. To get this confidence in your engines, make certain you spend plenty of time running the engines on the ground, on the model with the cowls in place (if you intend to make your first flights with the cowls). Synchronizing the engines is good, but it is more important to spend time making certain they both run reliably.
11. If switching to Robart wheels, use a 2-3/4” nose wheel and 3-3/4” or 4” main wheels. (4” wheels are probably closer to scale).
12. When mounting the top turret, the openings for the machine guns may need to be cut lower so that the turret can be fit over the guns after they have been glued to the fuselage.
13. A tube for guiding the elevator and rudder servo wires has been added inside the fuselage. The tube may not be large enough to accommodate both wires, so guide one set of wires (either for the elevator or rudders) through the tube and the other set of wires down through the fuselage.
14. There is also an antenna tube that has been added in the fuselage for guiding the Rx antanna--
15. When mounting the waist gun windows, glue only the top and bottom or only the sides of the windows to the fuselage. This way, if you ever break off one of the waist gun machine gun barrels, it will be possible to remove the windows for repair. Or, same as suggested for the top turret, use small screws to mount the waist gun windows to the fuselage instead of permanently gluing them on.
16. Note that the 1/4-20 x 2” nylon wing bolts that secure the outboard wing panels to the inboard wing panels screw in only about two turns. This is normal.
17. In several places the instruction manual reminds you to harden screw holes in wood with thin CA. However, this is not necessary for the four screws that mount the nose-gunner canopy. The mounting blocks are hardwood and already grab the screws tightly. Adding thin CA here could make it too difficult to remove and install the screws.
18.
(Photo 2) If you encounter difficulty when installing the throttle servos in the lower throttle servo mounting rails (step 1, page 11), you may cut approximately 3/16” from the end of the forward rail and support.
19.
(Photo 3) Drill 5/32” holes where shown to accommodate the 1/16” drill and a screw driver when mounting the throttle servos in the lower throttle servo mounting locations.
20.
(Photo 4) When drilling the aluminum wing tubes for mounting the inboard and inboard wing panels (step 5, page 33 and step 7, page 34), for perfection, use 1/8” and 3/32” brass tubes (available from K&S in 12” lengths) as guides. (The holes in the wings may first need to be drilled with a 1/8” drill so the 1/8” tubes will fit.) These “guides” will center the drill. But because the inside diameter of the smaller (3/32”) tube is only 1/16”, pilot holes will first have to be drilled with a 1/16” drill. After drilling the pilot holes, remove the panel you are mounting and the tube, enlarge the hole with a #43 drill for tapping, tap the threads, then mount the panel.
21. Keep the small scraps of MonoKote you cut from the fuselage sides when installing the side gun packs (step 5, page 39). These scraps may be used for minor repairs/patches if ever required.
22. When flying from paved runways, reduce the nose steering servo throw. Nose wheel steering is sensitive and if there is too much throw it will be too easy to overcorrect steering inputs during takeoff causing the model to veer too far one way or the other.
23. Also regarding nose steering, as the nose wheel is sensitive to steering inputs, it is a good idea to make a few practice takeoff runs down the runway and trim the nose wheel so that the model tracks straight. The wind direction seems to affect the model’s tracking during takeoff, so whenever the wind velocity or direction changes, the nose wheel may require trim changes so that the model will track straight. This is most important when flying from paved runways.