|Wing Area:||1036 sq. in.|
|Wing Loading:||46.5 oz/sq. ft.|
|Servos:||11 Futaba servos - see text|
|Transmitter:||Futaba 9CAPS with TM8 FASST module.|
|Receiver:||Futaba R608FS FASST receiver|
|Receiver Battery:||4 cell 4200mah Hydrimax|
|Motor:||Electrifly Rimfire brushless outrunner motors (42-60-480kv).|
|ESC:||Castle Creations Phoenix 80 controllers|
|Flight Battery:||Electrifly Power Series 3200 mAh LiPo batteries|
|Available From:||Great Planes distributors or your local hobby shop|
|Retail Price:||$649.98 - ARF kit only|
Top Flite touts this plane as "The most detailed B-25 ARF ever ó inside and out!", and they will get no argument from me! This airplane looks incredible, and has many of the scale details that one would not expect in an ARF model. Top Flite is known in the industry for designing and manufacturing aircraft kits that look and fly extremely well, and with the release of the Gold Edition B-25 ARF, Top Flite has taken the ARF beyond the next level.
The main kit box was shipped inside of another box for added protection. Inside of the main kit box, the sub-assemblies were also boxed and sealed in a protective plastic. The sub-assembly boxes are fitted in the main box with the precision of a puzzle. The airframe arrived in perfect condition except for one scratch on the right inside flap.
Although I knew the dimensions of this model before it arrived at my doorstep, itís hard to appreciate the size of this model until itís sitting right in front of you... or until your wife explains how she got it into the house from the doorstep!
The fuselage is massive but surprisingly light. The construction is traditional balsa and plywood with fiberglass, plastic and metal accessories. The fiberglass parts are pulled and painted with precision and are extremely tough. The Monokote on the fuselage and wings had the slightest amount of sag in it, but was easily shrunk back in place with the aid of a covering iron.
Additional items provided for this review and recommended by Great Planes:
The assembly manual is incredibly detailed. The pictures are large and clear and make it easy to pick out detail as explained in the text. My B-25 was one of the first produced, so the manual had a few small omissions and discrepancies that have been noted and updated on the Top Flite website.
Hint: During the construction of the B-25, Hex head screws are used often. I found out that garden variety hex wrenches, especially in the .050 size, are not up to the task. Save yourself some frustration and start with the good stuff from the beginning.
The wing is assembled from 4 separate sections. The two outer sections each include an aileron and a flap. The two inner wing panels each include a flap and eventually the subassembly that includes the motor nacelle and landing gear unit.
The first step in the assembly process is to hinge the flaps on the inboard wing panels. Pivot (pinpoint) hinges are used throughout the model to hinge the control surfaces, although different sized hinges are used for different control surfaces.
Before hinging any of the surfaces, the manual recommends that you add a small drop of plastic compatible oil to the pivot point of each hinge to help lube the joint, but more importantly to keep the Epoxy from adhering to the pivot joints.
The nice thing about hinging this model is that all of the hinge holes come drilled, and you donít have search for the holes because the Monokote covering is cut away from the hinge holes.
Take your time - it is easy to insert the control surfaces too close to the main wing assembly. Make sure the pivot point of the hinge is on the hinge line.
At this point, the manual recommends assembling the engine nacelle system, mounting the motors and fitting the fuel tanks to the inboard wing panels. Since I was converting my B-25 to electric and had yet to determine exactly how I was going to do that, I decided to skip ahead and do some servo installations while I mulled over the conversion possibilities. I skipped the servo installation for the inboard panels since I would be handling the inboard panel frequently during nacelle assembly, and began working on the outboard panels.
Each of the outboard panels has two control surfaces: one aileron and one flap. The flaps and ailerons are hinged with pivot point hinges in the same manner as the inboard flap although smaller sized pivot point hinges are used for the ailerons.
The flap and aileron servos are installed (screwed) onto mounting blocks that are glued to the back of the servo hatches. The hatches (all hatches) already have the Monokote removed from the servo control horn slot (also note that the screw holes in the hatch come laser cut from the factory). Little touches like this make building the B-25 a much more enjoyable experience. Each of the servo hatches are held in place in the wing with 4 small .050 allen head screws.
On many models (including scale models), the control horns are attached by sending a screw through the control horn to an attachment plate on the other side of the control surface. The result is usually a very secure control horn that looks terrible. On the B-25, the control horns are attached to the control surfaces with small wood screws that screw into hardwood plates embedded in the control surfaces, and the result is a very sturdy installation with no control horn retaining plates on the top of the wings.
The manual recommends making control rods that consist of a soldered clevis on one end and a nylon clevis on the threaded end. Since I have had a few issues with nylon clevises in the past, I decided to use 2-56 Dubro control rods with metal clevises on one end and Z-bends on the other to connect the servo control arms to the control surfaces.
The manual recommends jumping ahead to look at the "servo extension sketches in the back of the manual." These sketches do not show the proper orientation for the hatches, and the pictures are for extension purposes only. I got a little eager and followed the ones sketched in the back for the hatch layout since I had just flipped to it as recommended in the manual to look at extensions and ended up mounting the servos with the wrong orientation. The pictures on the main wing page in the manual (page 23) are correct.
I had finally decided how to approach the electric conversion. (Note: At this point in my build, Top Flite had not yet released a conversion addendum). The B-25 doesnít appear to be designed with electric power in mind. There is no central battery location with easy access, and in fact, there is no easy access into the center of the fuse without cutting it (which I couldnít bring myself to do) and limited access to the front of the fuse only after removing the canopy and cockpit floor (after completion). Without easy access into the fuse, I decided I was eventually going to make battery trays in each of the wood nacelles where the glow fuel tank would normally go. Unfortunately, the recommended battery packs are a little too large to fit all the way into the tank compartment. I decided to come back to this.
The wood nacelles are a combination of balsa and ply that are surprisingly light and tough. They are also fuel-proofed which is a nice touch for those who will be flying with glow power. Each of the nacelles is held in place on the inboard wing panels with 4 nylon bolts and a pair of nylon alignment pins.
I used the mounting template provided with the Electrifly brushless motor mount (medium motors) as a guide for drilling the mounting holes on the front of each firewall.
I drilled a small hole at the cross section of the template, and then used this to find the center of the firewall as viewed through the back from the glow tank compartment. After the template was centered and attached, I drilled the holes for the motor mount and repeated these steps for the other nacelle.
The Rimfire motor attaches to the motor mount with 4 screws. The X-mount supplied with the motor is not used. After the motor/mount system is assembled, the whole assembly attaches to the firewall with 4 4-40 bolts, washers, and blind nuts.
At this point, I still had not decided how I was going to fabricate the battery trays, so I moved on to the main landing gear (retracts).
The B-25 kit comes with fixed landing gear, but I installed the optional but highly recommended Robart retracts for this review.
The air line must be installed before mounting the retracts. I picked the purple air line that came with the control kit for the "up" line and used the pink for the "down" line. I made sure I followed that protocol for the entire assembly process. There is no guessing on the length of the air line needed; the manual gives the proper length to cut the air line. (Note: The amount of airline provided in the control kit was not enough for the entire build. I needed one more set.)
The air lines are run through the nacelles and then out to the inboard edge of the wing panels. Note: The "up" air lines for the retracts are run through a small hole in the back of the nacelle first. Make sure to center the retract plate on its perimeter in the countersunk mounting space before mounting the retracts permanently. The Retracts are mounted to hardwood rails in the wood nacelle with 1/2 inch Philips screws.
I wanted to get an idea of how the fuel tank opening (new battery tray area) would line up with the fiberglass nacelles, and I also wanted to see how much clearance I would have between the wood nacelle and the fiberglass nacelle to help me determine the best way to approach the battery trays and hatches. I skipped ahead just a bit in the manual and mounted the fiberglass nacelles.
The fiberglass nacelles simply mount to the inboard wing panels with washers and Phillips screws that are screwed into hardwood plates mounted in the panels.
With the fiberglass nacelles removed, I drilled 8 holes in the precut marks on the firewall and installed blind nuts on the back (if you hadnít noticed yet the fiberglass nacelles need to be removed and installed multiple times during construction). I reinstalled the fiberglass nacelle for the following steps. Next, I installed the four plywood mounting tabs (per nacelle) and the cowl rings.
At this point the manual recommends test fitting and cutting the cowls to fit the head of the engines. Yet another nice advantage of electric systems, nice uncut scale looking cowls!
In order to more easily work on the nacelles and cowls, the inboard wing panels are temporarily mounted at this point. The aluminum wing tubes simply slide into fiberglass sockets in the fuselage and then the wing panels slide onto the wing tubes. The included stand makes this and the rest of assembly easier.
I attached the fiberglass intakes to the top of the wing panels with 8 button head allen screws. The fiberglass cowls are now slid over the cowl rings and aligned with the fiberglass intakes. On my kit I had the sand the sides of the rings slightly in order to get the cowls to slide back to their proper location. With the cowls temporarily in place I attached the props to the motors and then adjusted the cowls for a better fit.
As noted in the manual, "due to the out thrust and down thrust of the engine, a compromise will have to be made between centering the propeller in the cowl and aligning the cowl with the nacelle cover." This was a bit frustrating: When I centered the prop hub in the cowl it made the cowl look extremely crooked in relation to the nacelle and wing. When I centered the cowl in relation to the nacelle, the prop was no where near centered in the cowl. At this point I was questioning why I didnít remove the offset thrust. Since I was converting my model to electric, the chances of an engine out situation are greatly reduced.
Back to the situation at hand, I decided to compromise (as noted in the manual), but I leaned toward making the cowls as close to straight as possible. After I was comfortable with the cowl placement, I tack glued it in place to the cowl ring.
Next, I removed the screws from the cowl rings and slid the cowls with rings attached away from the nacelles. I used thick CA to build a glue fillet on the front and rear of the cowl rings. Now that the rings were permanently installed, I moved onto the replica engines.
The replica engines are made from a fairly hard black plastic. Part of the preparation of the replica engines included attaching replica pushrods. Talk about detail! The pushrods are actually made from metal. Although it takes some time to attach the pushrods as described in the manual, the end result looks impressive.
I wanted to see if I had enough clearance between my replica engines and rotating outrunner motors so I temporarily installed the engines to the cowls with tape. After a quick test fit of the cowls, I could see that I would need to do some cutting to achieve the clearance I needed. I used a Dremel sanding drum to cut the holes larger in the front of the replica engines.
Before permanently mounting the replica engines in the cowls, I sanded the edges of the engines and the insides of the cowls for better glue adhesion. I used thick CA to attach the replica engines.
In order to screw the cowl rings to the mounting tabs I had to reach ever so gently through the replica engines back to the cowl rings while trying not to lose the washers from the mounting screws. After a few less than stellar attempts, I added a few small pieces of fuel tubing to the screws to hold the washers in place. I just so happens I wouldnít need the fuel tubing that came with the kit. After I had the cowls mounted, I went back and added the props and prop nuts.
Note: Before permanently mounting the cowls, I mounted the Castle Creations Phoenix controllers to the sides of the motor mounts with Velcro.
One end of the forward and rear aluminum wing tubes comes with a 4-40 hole already tapped, but the builder must drill and tap the other end of the tubes. This is not much fun but you must take your time when you do this. I took my time and still ended up with one center hole.
With the tube and inboard wing attached, one of the holes in the tube is lined up and secured through the pre-drilled hole in the wing panel. I marked the wing tube corresponding hole with the tip of the drill bit before I made the final decision to drill. I backed the wing panel off of the tube and checked to make sure I was lined up in the center of the tube and then drilled through the corresponding hole in the wing down through the wing tube and taped the opposite hole with a 4-40 tap.
A molded plastic oil cooler air scoop is mounted to each of the outboard wing panels (Monokote needs to be removed first). The air scoop serves two purposes: First, it looks cool and adds to the scale appearance, and second, It serves as the access point where a 1/4-20 nylon bolt is inserted to attach the outer wing panel to the inner wing panel... along with a 4-4- socket head screw. The outer wing panels are attached to the inner wing panels with the same method of drilling and tapping as used for the inboard panels.
As you might recall, the battery would not lay down flat in the tank compartment; it is just slightly too long. During the fit of the fiberglass nacelles, I noticed that there was a fair amount of space between the wood nacelle and the fiberglass nacelle. It appeared that it would be easy to make a slanted tray in the tank compartment that would fit the battery easily and still remain neatly tucked inside of the fiberglass nacelle. Luckily, about two days later Top Flite released an electric conversion addendum that shows a conversion process very similar to what I was planning!
With fiberglass nacelle removed, I first removed the top of the fuel tank trays in each nacelle. I realized that I could get the battery much further into the nacelle if I cut the tray. I attached one of the cut wood nacelles back onto the wing and made a paper template to represent a battery tray. I ran the template the length of the nacelle opening allowing the rear of the template to rest on the back of the opening and the front of the template to rest on the leading edge of the wing to provide the proper slant needed to allow the batteries to be inserted the deepest into the nacelle. After I was comfortable with my battery tray arrangement, I used the paper template to cut two permanent battery trays from light aircraft plywood.
I permanently mounted the trays to the nacelles and used hard balsa square stock as support for the bottom of the trays.
I used a strip of Velcro down the center of the battery trays along with a Velcro "seatbelt" to keep the batteries secure on the trays.
Now that I had very functional new battery trays, it was time to construct a way to easily insert and remove the battery packs. As with most of the parts, the fiberglass nacelles as provided are very rigid and are fabricated and painted with every bit of care and detail that any fine modeler would have put into them had they been building them from scratch. Now it was my turn to tear them up a bit.
Since the conversion addendum had been released, I used it as a reference guide for making the hatches but decided to make mine just a bit smaller than recommended. By making it smaller I could cut along the natural lateral break lines in the nacelle and still have plenty of room to insert the battery. After measuring to make sure the battery could easily pass, I outlined the hatch into the nacelle with a number 11 X-Acto blade. Next, I used a fine tooth Zona saw to remove the hatches from the nacelles.
After the hatches were removed I used small plywood tabs in the corners of the nacelle openings to keep the hatch from falling into the nacelle.
It was time to dig into my old box of leftover parts to see if I could come up with an easy way to attach the hatches. I quickly found a pair of latches that I had intended for another project. I made a small slot in each hatch to allow for the spring mechanism and then attached the latches to each nacelle with thick CA. One the other end of the hatch, I added a pair of plywood tabs to the hatch in order to keep the hatches from falling off when they are inverted. I did a quick install of my new hatch/latch system and found that it worked well but had just a little bit of slop in it. A small piece of plywood inserted into the main nacelle, where the latch pin fits, did the trick and made everything fit tightly. The hatches are easily removed and installed with the new hatch/latch system.
Gear doors are a must on a model of this caliber. The gear doors on this B-25 ARF are made of fairly heavy fiberglass and are molded separately from the nacelles but not cut from them, which helps to speed up assembly time and save on the aggravation of cutting them out from the nacelles. They donít fit perfectly, although they are very close.
The offset hinges are metal and consist of two main parts. The front half of the hinge (door hinges) has nylon ball links that must be connected to one end with some washers and a screw. The other half of the hinge (nacelle hinges) has the ball link ball that must be attached to it. The hinging action is provided by the socket connection between the ball and the nylon socket.
|Note: There are two different "types" of hinges used for the gear door installation. The rear door hinges have a slightly different orientation from the front. My kit included a hinge addendum that clarified some of the possible hinge issues with the manual.|
After the hinges are assembled, the bottom of each hinge mounting plate is sanded to remove the anodizing for better adhesion. I taped the fiberglass doors onto each nacelle in its proper position, then glued the hinges with epoxy and microballons to the back of the gear doors and nacelles. The process quickly got a bit messy even by my standards. I thought I could do more than one hinge at a time and keep it neat, but I was wrong, so I pulled the hinges out, cleaned everything up and started again. This time I did one hinge at a time using 5 minute epoxy and microballons. Much better!
This was the first time I had hinged anything using the method described above. I was amazed at how well it worked and how fairly easy it was to assemble.
The main gear doors on the B-25 are closed when the retracts come back and hit a bellcrank lever which in turn moves the pushrods that close the doors. The main gear doors are opened when the retracts release the bellcrank lever and a spring in turn pulls the bellcrank which pushes the pushrods that open the doors. Sound complicated? It might be if I had to figure out the geometries by myself, but fortunately for me it is all figured out and explained in the manual in perfect detail.
The first step is to mount the lever mount/lever stop to the back of the wood nacelle. The thin plastic washer is mounted to the bellcrank next. The bellcrank is then mounted to the lever mount with a brass bushing and a screw. The spring is then hooked between the lever mount and the bellcrank lever. This assembly is the main pivot point that provides the base for the door retraction. Inspect these pieces often! The retract comes back and hits the bellcrank lever fairly hard.
Following the template in the instruction manual, I bent the inboard door pushrods. On one end of the pushrod I added a nylon clevis. On the other end I added and EZ-connector and a control horn. The outboard pushrods are made from short threaded pushrods with a pair of nylon clevises and a control horn. One end the pushrods is attached to the bellcrank with the nylon clevises. The other end is attached to the to the gear door by gluing the control horn in place with CA.
After the pushrods were attached, I gently worked the doors up and down by hand (the retracts were not locked) as much as I could to see if the mechanism was working properly. It was working well, but not perfectly. I was having a small binding issue with my outboard pushrods, and I could see that the pushrods were hitting up against the side of the fiberglass nacelles. After reworking the bend in the pushrod, I had the nacelle working without binding. It was time to try my luck with some air. I put my hand pump on the up line of the right retract and gave it some pressure. The retract went back fairly quickly and pulled the doors closed. Unfortunately, there was a gap between the doors when closed. I went back and shortened the length of the pushrods a bit and gave it another try, and this time they worked perfectly. I needed to perform the same process on the other gear door pushrods as well.
A short screwdriver comes in real handy for the nose gear installation.
Before mounting the nose retract, I mounted a set of small ball-links to the sides of the gear strut on the steering arm. These will eventually serve as the mounting links for the pull-pull steering cables. This was a bit different than I was used to but the system works very well. The nose gear simply mount to two hardwood rails in the front of the fuselage with Phillips screws.
The nose gear door functions in a similar fashion to the main gear doors in that the action of the retract triggers the closing of the doors and springs in turn help open the doors. The difference is the spring action for the nose door is provided by the hinges that the door is mounted with. It seemed a little suspect to me during construction but has not proven to be a problem yet.
|The manual shows the installation of the nose gear door lever to the side of the front retract opening. Unfortunately in my kit a small piece of wood that should have been removed at the factory was still present causing a mounting problem. It was obvious from the picture in the manual that this piece of wood was not supposed to be there so I removed it.|
One end of the nose gear pushrod has a shortened ball link socket. The other end of the pushrod was connected to a control horn via an ez-connector. The ball link socket connects to a ball link attached to the gear door lever. The control horn is then glued in place on the gear door.
The air system hookup is fairly straightforward if you follow the B-25 instruction manual and the instruction manual included with the air control kit. The B-25 kit comes with a plywood air control mount and fill valve mount pieces that make the installation of the control valve and fill valve a breeze. For those that have previously made their own air control mounts you will really appreciate this. The fill valve and pressure valve are mounted to the side of the fuselage in factory provided holes (Monokote covering needs to be removed), while the air control valve is mounted to a laser cut etching of itself on the factory installed radio tray. The air control valve is operated with a standard size servo which I mounted to the radio tray.
I mounted the receiver to the radio tray with Velcro. The Velcro provides some vibration dampening but there isnít much vibration with those smooth running Rimfire outrunners. There is an antennae tube factory installed in the fuselage, but I chose to run my antenna along the bottom of the fuselage for better reception (before the maiden flight I switched over to an eight channel 2.4GHz receiver). The mount switch and charge jack were then mounted to the side of the fuselage. The whole installation looks very neat and is easily be covered by the cockpit floor.
The instruction manual recommends installing the air tank in the front of the fuselage in a mounting hole in the former. It makes for a very neat installation, but I wanted to use a slightly bigger air tank than recommended. The bigger tank would not easily fit in the front without some former modification, so I decided to mount the air tank above the fiberglass wing tubes in the fuselage. I made a small plywood tray and glued that to the top of fiberglass tubes with CA. I then mounted the air tank to the tray with Velcro.
Having two battery packs mounted in separate nacelles presented a little bit of a problem for me. I like to run my twins with the battery packs in parallel so each motor sees the same voltage. I knew I might be pushing my luck if I ran my system in parallel the way I normally do (battery wires coming to one common point) because of all the excess wire that would be needed. Many brushless controllers have some issues with overextended battery wires. Since I was running Phoenix 80 controllers, I wanted to see what Castle Creations response would be to the amount of wire I was planning, so I gave them a call.
I spoke with a representative from Castle who said he was in the same situation I was in except he was building a Tigercat. He had a method for running a parallel system without creating havoc on the controllers, and it didnít involve adding extra capacitors. It was simple: "just run a set of wires between the controllers...no need to run wires as a common point (battery) and back to the controllers." I set out to design a system that would do as Castle Creations described, and also be able to come apart if I need to remove the inboard wing panels and nacelles from the fuselage.
The cockpit floor on the B-25 sits up above the radio tray. I installed a set of balsa rails along the fuselage sides for the cockpit floor to be screwed into. The cockpit floor comes pre-painted in flat black. Next, I assembled the instrument panel from a set of decals that are applied to a wood plywood base that has the instrument gauge holes cut out. The "gauge" decal is mounted from behind the instrument cluster in line with the cutouts; the template decal is mounted to the front. The completed instrument cluster has a nice 3-dimensional look to it. I glued the completed cluster to the cockpit with thick CA.
The B-25 kit includes a set of pilots but they are not what I would consider "scale". They are flat plate wood profile cutouts. They will make good place holders until I can find a set of appropriate pilots. The decals of the pilots are attached to the wood bases. The bases have a small tab in the bottom of them that fit into a corresponding slot in the cockpit floor. I secured the pilots with CA. The pilots each have a green seat back that glues directly to the cockpit floor behind them. The last step in cockpit assembly is to glue in the yoke posts and control yokes. The completed cockpit probably won't win any scale static competitions, but it adds to the scale realism.
The nose-gunner canopy is constructed from a lower fiberglass piece to which an upper canopy window is attached. I scuffed up the contact areas with sandpaper to ensure a good bond. Thin CA is applied to the inside of the nose-gunner canopy bottom and allowed to wick into the joint. Take your time - the thin CA can easily make its way to the outside of the nose canopy if you add to much CA or rush this process. The assembled nose gun is installed through the hole in the nose-gunner canopy and is held in place with retention hooks and rubber bands. The rubber bands allow the gun to be "shock mounted" so that if it is bumped it wont readily break off.
I installed the nose-gunner cabin platform to the front former with thick CA. The bright green molded plastic cabin floor and cabin back are installed next (The floor is glued to the platform and the cabin back is screws to the front fuselage former). The nose-gunner ammo trays, ammo boxes, and bight orange kneeling pad are then glued to the cabin floor with CA. The completed nose gunner cabin looks very impressive; it adds greatly to the scale effect by giving the B-25 dimensionality.
I installed the four cell 4200 NiMH receiver battery to the bottom of the nose-gunner cabin platform with a Velcro "seatbelt". The nose-gunner canopy and main cockpit canopy are attached the fuselage with small button head screws. As provided, the cut lines on the canopy were not straight, and there were a few burrs along the side edges. There were also scratches on the window section of the canopy. The Main canopy attached easily, but I needed to trim away some of the nose-gunner cabin back in order to get the nose-gunner canopy to fit properly.
I assembled the top turret machine gun from a plastic machine gun base and two plastic machine gun barrels. This assembly is glued to the top of the fuselage after a small round black Monokote piece is added to the top of the fuselage for the machine gun base. The top turret canopy is set on top of the fuselage (around the gun base) and outlined with a felt marker. The outline is then used to trim away some of the Monokote to ensure a good glue joint when gluing on the top turret canopy. The finished top turret machine gun and canopy looks rather menacing!
The tail gunner cabin is made from heavy duty fiberglass and serves two purposes. It houses the tail-gunner pilot position, but it also serves as the cover for the aft end of the fuselage. The tail-gunner pieces (tail-gunner bulkhead, shield, mount, and tail-gunner pilot) are glued to the base of the cabin with CA. I chose to leave the tail-gunner pilot out of the cabin since the canopy would be permanently mounted to the cabin with ca and I didnít want a permanent profile pilot.
I attached the tail gunner cabin to the rear of the fuselage with a set of button head screws and the rear machine guns, which double as mounting screws.
The side gun packs are made from abs and include small wood formers on the inside which help the gun packs to maintain their shape but also serve as a mount for the machine guns. I taped the side gun packs onto the side of the fuselage in order to outline them on the Monokote beneath. The Monokote is removed to make sure that the glue joint between the gun packs and the fuselage is strong. I glued gun packs onto the side of the fuselage with thick CA.
The waist gun windows are glued to the side of the fuselage in the same manner.
The ADF football antenna is attached to the bottom of the fuselage with magnets. I glued the magnets into the fuselage after drilling small holes for them to fit into. The magnet system makes it easy to remove when transporting the model.
The horizontal and vertical stabs are made from balsa and ply and are built with an airfoiled shape. I attached the rudders to the vertical stabs with pivot point hinges. While the vertical stab hinges were drying, I moved on to the vertical stab. Two small plywood joiner mounts are each constructed from two smaller pieces of plywood. I then slid those mounts over the elevator joiner wire. The mounts are glued to the back of the elevator after the covering is removed from the glue contact area. Next I slid the elevators over the joiner wire and glued them to the stab with pivot point hinges. A small dowel rod is then inserted into the front of the stab. This small dowel rod locks into a mounting hole in the fuselage.
The vertical stabs have a small cutout that matches the shape of the end of the horizontal stabilizer. The horizontal stab "locks" in to the vertical stabs which are then held in place with 4-40 Philips screws. The rudder servos are embedded in the ends of the horizontal stab. The servos and control rods are attached using the same process as the ailerons and flaps.
The elevator servo is easily mounted in the top of the elevator. I attached the pushrod to the elevator joiner wire with a ball link and socket. I used a z-bend on the servo control horn.
At this point I mounted the horizontal stab to the fuselage with washers and 4-40 screws. Amazingly, the whole assembly is perfectly squared to the fuselage with the preset mounting locations. No need to bring out the triangle and tape measure.
Note: There is a tube installed in the fuselage to run the servo extensions from the rear of the plane to the radio tray.
The decals that are included with the B-25 are the best self adhesive decals that I have ever used. They even have a flat finish which matched the overall scheme of the B-25 perfectly. I used a glass cleaner solution to "float" the decals onto the model and then used a Mactac adhesive applicator pad to squeegee out the excess solution from under the decals. The decals came out perfectly without bubbles.
The instruction manual recommends balancing the completed model on a Great Planes C.G. Machine. At first I was a little apprehensive about putting a 21 pound airframe up on a C.G. machine, but it worked fine although the metal rods did flex a little. The balance point is 5 inches back from the leading edge of the wing where it comes in contact with the fuselage. With the receiver pack installed in the nose, I needed absolutely no extra weight to balance the ready to fly aircraft.
Next, I programmed the radio with the recommended control surface throws.
*From the manual - 1/4" of down elevator should be mixed in with full flap deflection to control "pitch-up" when flaps are extended.
With one 5 cell 3200 mah Electrifly battery hooked up the left motor (14x7 three blade prop) I was getting 536 watts at 28 amps. I donít know about you, but I am used to my models having a lot of power and seeing this reading made me nervous. Thatís only 1072 total watts for a 21 pound plane. I thought I might have gotten a bad reading so I tried the right motor and got a similar reading...538 watts. The electric conversion PDF supplied on Top Flite's website claims that this setup should be putting out 680 watts. I advanced the timing on my controller to get more power and came up with 567 watts per side.
I ran some numbers in Motocalc and came up with what I though would be an inexpensive solution. I swapped the 14x7 three blade props for 14x9 props to get more pitch speed and what appeared to be better flying numbers according to Motocalc. With the 14x9 props I am getting 580 watts per side and more pitch speed.
In the meantime I sent an email to Hobbico asking about the relatively low numbers for this setup. I received an email back from Greg Hahn telling me not to worry about a thing. He had been flying this exact power combination at a few events around the country and reported great success.
I ran different power combinations and figured out that six cells and the 14x7 props would also be a great alternative for higher power flying. A local club member put me in touch with a FlightPower Representative who expressed interest in helping me find a higher power alternative for the bomber. He sent a set of 6s 4270 EvoLite battery packs. With the FlightPower 6s packs I was getting 865 watts per side with the 14x7 props...much better. I was comfortable with this setup because Great Planes recommends 6 cells and a 15x8 two blade prop for .70 four stroke equivalence in their "brushless power system" literature.
I now had my lower power and lower weight setup (Electrifly battery) and my higher power but higher weight setup (FlightPower battery). I would try the recommended setup first then see later how much of a performance increase the six cell pack would be. I was now covered, but unfortunately so was the ground outside... with snow!
After waiting for almost five months after completing the airframe, I finally had a break in the weather that would allow for the maiden flight. I packed up all the flight gear and headed to the field on Memorial Day weekend. I felt it was a very appropriate weekend to fly the maiden flight on a bomber with such a rich history!
As soon as I pulled out the B-25J at the flying field it drew immediate attention from the club members and spectators. Although I would have liked to take credit for building this B-25 from a kit, I had to admit to the questioners that my B-25 was an ARF, and most were amazed at this revelation.
Assembly at the field does not take much time at all. I keep the inboard wing panels mounted all the time so all I have to do is install the outboard wing panels, fill the air tank for the retracts, and install the battery packs.
After the field assembly is complete I perform a range check. I always do a range check before flying, but I was especially careful with my range test for the B-25 maiden flight: I would be committing a fairly expensive plane to flight, and this would be the first time that I have used my 2.4GHz TM8 module system with my Futaba 9CAPS transmitter. Everything tested fine.
The B-25 looks incredible in the air. I personally have never flown an aircraft that held my attention as much as this B-25 does...and I have owned about 60 aircraft. I got caught up in just watching it fly. Although I was skeptical at first, The Rimfire motors provided plenty of power for scale flight. The B-25 is not overpowered but is definitely not underpowered. The Rimfire motors run very quiet with only a little noticeable whine, but the sound from the props is great and adds to the flight experience. I felt no urge to do anything except just fly the B-25 in front of me so I could see how great it looked, but I knew that I needed to test the airframe a bit for this review.
The B-25 tracks incredibly well with little to no tail waggle in the air. Although when the cross wind picked up the B-25 had a higher than average tendency to weather vein into the wind. The B-25 flies much lighter than the wing loading number would indicate. It never gave me that sinking impression and I never felt like I was on the verge of a stall even when I was turning upwind at about half throttle.
I used the recommended low rates for almost the entire flight. At one point I switched to high rates but quickly switched back because the B-25 felt more in control on low rates. The B-25 is very responsive during faster flight. During slower flight, the B-25 is obviously less responsive but maintains perfect control right up to its stall point. It does have a very minimal flight correcting tendency. It will very, and I mean very, slowly START to correct itself out of a turn, but it wonít return the wings to level. The B-25 is incredibly smooth in flight. I really didnít expect that it would be this easy to fly and also fly this well.
The rudders are surprisingly effective but not overly. I eventually used a small bit of rudder in the turns to help keep the nose down. Without rudder input, the B-25 will maintain a nose high attitude in the turns at lower flight speeds. At higher flight speeds the B-25 maintains a level attitude in turns.
The wind at the field was blowing slightly across the runway and was gusting to about 15 mph. I wasnít too worried about the wind because the B-25 has some weight to it and shouldnít be affected too much by the wind. I advanced the throttle slowly and taxied out to the runway. A quick hit of the throttle to about half showed that the B-25 would accelerate quickly. I taxied to the end of the runway, shut down the motors, took a deep breath, and then slowly advanced the throttle to get the bomber rolling. After I was comfortable with how it was tracking, I advanced the throttle to full and watched it accelerate down the runway. The B-25 picked up speed quickly but never seemed to get very fast on the runway. I kept the aircraft on the runway for about 400 feet and then slowly fed in some up elevator. The B-25 lifted gracefully off of the runway but was climbing a little steeper than I wanted for the first flight. I pulled the throttle back to about 3/4 and started a slow banking turn out over the grass runway at our field. I wanted to make sure there wasnít too much drag from the gear doors effecting the flight characteristics so I pulled the retracts up on my first pass. The B-25 picked up speed as soon as the gear was tucked away. I needed about nine clicks of down elevator and about 4 clicks of right aileron to get it to fly straight and level.
To prepare for landing I slowed the model down slightly and dropped the landing gear and flaps. With the landing gear and flaps down the model decelerated rather quickly so I fed in some more throttle. To deal with the slightly excessive flap to elevator mix causing a slightly nose down attitude, I had to hold in a little more elevator. The B-25 began to settle in nicely. On final, I accidentally let off a little too much on the elevator and the nose dropped. I pulled back on the elevator quickly and the bomber recovered perfectly. I was now lined up over the runway at just slightly under half throttle. The actual landing was uneventful. All I needed to do was hold back slightly on the elevator while slowly dropping the throttle. The B-25 set down on the runway smoothly with a slightly nose high attitude and rolled out perfectly under control. I taxied back to the pits and shut the motors down.
What is really special about the B-25 is how it flies, especially with the flaps down; it slows down to a crawl. Unfortunately the recommended flap to elevator mix provided in the manual gave the B-25 a nose down attitude with the flaps extended so I had to feed in some up elevator.
Aerobatics? Well, this is a bomber. It isnít going to be very aerobatic and its obviously not meant to be, but I did manage to sneak in a roll. The roll was not the most graceful thing I had ever seen, but it was easily accomplished on low rates with very little down elevator needed while inverted. I would imagine that the B-25 would have no problem doing a loop. It has enough power and speed at full throttle.
Although the B-25 is fairly easy to fly it is not for beginners. There are also some fairly complicated assembly steps and flight system that needs to be installed and operated precisely. A pilot with a few sport models and experience with flaps and retracts should have no problem with the B-25.
When I started this project I was excited about the possibility of having a showpiece aircraft in my fleet, and that possibility is now a complete reality. It is an incredibly impressive model that grabs attention whether on the ground or in the air. The Top Flite B-25 is the most detailed ARF I have ever assembled, and the 62 hours that it took me to assemble it is only part of the proof. This B-25 is loaded with scale details.
The only thing better than the way the B-25 looks is the way it flies. It is incredibly smooth and handles much easier than the high wing loading would indicate. The electric conversion proved to be a little extra work but was fairly easily accomplished. All of the electric components worked flawlessly. Top Flite has raised the bar on ARF scale aircraft. I can't wait to see what they come up with next.
Watch for flight updates with the 6 cell FlightPower battery!Last edited by kevin; Jun 03, 2008 at 10:15 PM..
Very well done. The way you wrote the review will certainly help anyone that wants to convert the TF B-25 to electric. I really liked the fact that you took the hard parts, like the gear door assembly, and detailed the construction with large size pictures. I also liked the fact that you used Master Airscrew 14X7 and 14X9 three blade props. Those are the same props that I used on the VQ P-61...the e-props would just look silly on that kind of plane and Master Airscrew props work just fine.
Hats off to ya. Maybe some of those phoney reviewers will learn from your approach, as most don't show any construction detail. It leads me to think that they didn't even work on the planes themselves.
Thanks for the compliments guys, this was a very fun project. I like to add the extra detail, i am glad you enjoyed it...you should have seen it before it was edited ....although i do like the edited version much better.
I am not sure whats next but i need a little break...i have over 160 hours logged on this project (building, writing, pictures, video, etc.......).
Hopefully Top Flite will send their next gold edition arf my way for conversion....and before you ask, i have no idea if they are even planning on anything at this point
if you have any question feel free to ask.
For some reason the sections published a bit out of order...i apologize and will look into this***********
Last edited by kevin; Jun 04, 2008 at 11:33 AM.
I was a bit concerned about the power level....just under 1100 watts on a 21 pound plane is a lower "watts per pound" rating than i am used to....but i do agree that in level flight it is a bit faster than i would consider scale. (i watched b-25's fly at the mustangs and legends gathering late last year). Although, when you pull the nose up it bleeds off speed somewhat quickly(scale). So the six cell flight will definitely not be made at full throttle, i want to see how the airframe handles the extra power while climbing and in turns..............and also if it can hover, you know all reviews have to talk about how a plane hovers
for those interested....i ran the motors on 6s and the 14x9 props yesterday... 995 watts (the batteries were slightly cold).
Last edited by kevin; Jun 04, 2008 at 11:32 AM.
That is a really nice ARF, and glad to hear you had success after spending your life savings on it. It took me a bit of arm twisting just to buy an EVO 4-cell, but they are worth it. I think I'd be afraid to fly anything on the large Electrifly I still have.
One question: Was the nose art made to distract enemy fighters?
Last edited by EDF30; Jun 04, 2008 at 04:29 PM.
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