A comprehensive guide to building the LX / Banana Hobby YF-23

[Arcangel]

For those of us out there that liked this ATF fighter over the F-22 Raptor, here is a build guide that is still a work in progress but should help all those who want to build this cool looking model. I first have to ask everyone for their patience and understanding. I only get the weekends to work on projects so I usually end up spending only a couple of hours per project. I'll try to pass on the things I have learned while building this model and try not to bore you too much.;) With that said, let's begin.

} For this particular model, I did a complete test of all the electronics and I was disappointed in their failures. I lost (1) of the stock ESCs and (2) servos. The retracts worked fine, but the brake controller was set too high and the brakes over heated and warped the plastic hubs on the main gear. The next thing I did with this kit was do away with all the electronics that came with it. I have never had any good luck with the electronics from a LX / Banana Hobby model and most of the other guys here that have built LX models will agree with me.

} The landing gear on this model are just crap. I noticed on mine that the compression springs in the main gear were so weak that the gear lost half of its oleo travel just from the weight of the model itself and I have seen other pics of this plane across the web showing this model literally dragging its butt because the main gear were completely compressed.

Side Note : by replacing the retract gear and doing away with the brakes and all the PCB boards to control them; you actually take 5.2 oz off of the total weight of the model.

} I have noticed that 80% - 90% of the YF-23's build can be done with just the lower half of the fuselage. Go ahead and glue the receiver box and ESC vent grills in the lower fuselage according to manual. [ Make sure to remove any of the paint from the glue areas ]

} Some of the mods I have done will go into the top half of the fuse, but most will be in the bottom half. From here on out we are pretty much going to ignore the instruction manual. We can go back to it when the steps become more critical to the build or if we need to reference one of the pictures.

[Arcangel]

The first thing you learn when building a LX / Banana Hobby model is that it is designed with the idea that the electronics will be permanently mounted in the model.

The first mod that needs to be done is putting in an access hatch for the ESCs and the motor wiring. This photo shows where I put mine and a quick look at the mounting parts. [see photos]

[Arcangel]

The mounting tabs are an extra set of the tabs used to hold down the EDF fan cover. [ see photo ]
You can pick them up under the spare parts tab for the YF-23 at the Banana Hobby web site.

Tape the hatch panel back into place, center the tabs in the cut away area, get them as close as you can to the hatch panel and then slice the foam in the fuselage and glue them in.

{ I mounted mine with the posts facing down toward the outside, but in the future I would mount them with the posts facing up into the model. That way would eliminate some issues I've had to correct and their location really does not affect your placement of the ESCs. }

[Arcangel]

To reinforce the hatch panel, I used some thin carbon fiber sheet to make patches across the ends of the foam panels. Make sure you glue the patches with the strands running parallel to the top and bottom edges. [see photo]
For the guys that mount the tabs with posts up.... make sure you reinforce both side of the panel not just the outsides.
{ I forgot to do this on my first set and mine cracked while I tried to drill them for the mounting tabs. } :Angry:

[Arcangel]

The next mod to do is the landing gear replacement. This one is big and it requires some extra materials. [ All of which can be found on MotionRC's web site under the spare parts tab of the appropriate model ]

} The main right & left landing gear retracts from the FreeWing 80mm F-5 Tiger
} The nose gear retract from the FreeWing 80mm Mig-21
} The 4.1mm retract shaft pins from the FreeWing ME-262
} The plastic landing gear mounting blocks from the FreeWing 90mm F-15 Eagle
} Some extra pieces of EPO foam blocks for fill-ins. I have found that the foam shipping cartons from FreeWing are made of an EPO foam that is not as dense as their models but still good enough for filler work

[ If you already have some 4.1 mm retracts left over from some previously lost planes then you just need the struts ]

Side Note : The retract landing gear on the YF-23 are different from the LX Mig-29, F-22, and F-18 models. They bare a closer resemblance to the F-4 model.

[Arcangel]

The first step here is to get the retracts ready.

} For the FW F-5 main gear, we need to replace the shaft pins in the retracts OR grind new flats in the pins to properly get the orientation of the wheels to the YF-23. Since I am a lazy kind of guy, I have found that the shaft pins on the FW ME-262 main gear are ground at the right spots to turn the wheels in the right direction. You may just have to do a little grinding near the flats to allow for the set screw clearances.

} Next is to pull out all the plastic mounting blocks for the LX stock landing gear. I found out on mine that the blocks came out rather easy due to a lack of glue on the surfaces of the blocks, which appears to be another fault that many others before me have discovered during hard landings. :Loser:

} Now its time to measure out the lines to keep the gear running strait on the fuselage. [ see photo ]
I used my calipers to measure the distance from the center line of the fuse to the back corner point of what would have been the main landing gear door. Next lock your calipers on that measurement and move down the center line of the fuse to a point far enough a head of the landing gear door area and poke a hole in the foam you can see { Noted by red circles in photo } and draw a strait line between the two points. Repeat the process for the other side. When you look at those lines, they may not look parallel to the center line but trust in your calipers they are.

[xviper]

Mine is the kit version, with no electronics. It sat for months before I decided to open up the box and start on it. I have the fans/motors from an old A-10 and I bought new ESCs. Servos all come from old, crashed planes, as are all the servo extensions. I have some old retracts that I will use instead of the stock ones that came with it.
I'll be following your build with great interest. Like you, I only work on this plane periodically as I have other projects on the go. I find the YF-23 kit version to be a tedious build and I get bored with it after a couple hours. Been tied up with some repairs from last fall's mishaps. Have a Bird of Time and Freewing 90mm F/A-18 OZ edition both still in their boxes that I'd like to get started on.

[Arcangel]

I hear ya xviper, This is model is definitely more difficult to work on than the Mig-29 or F-22 just because of its gear, but I like the model, so I will do the mods to make it better. :)

In this next step we need to prep the landing gear mounting blocks and the fuselage. [ see photos 1 & 2 ]

} There is a little nub on the bottom of the blocks near the back side as highlighted in red circle, you can grind or file this off as it has no use in this model and it gets in the way later on.

} The front surface of the block highlighted in green will be placed flush against the forward wall of the landing gear area.

} The forward surface of the block highlighted in blue will set the trace line for you to cut the fuselage for fitting the landing gear block [ refer to photo 2 ]

[Arcangel]

Now we are going to start fitting the gear blocks into the fuselage.

} First take note of each gear block as they are marked " L " and " R " corresponding to left and right. Make sure you trace the L gear block on the left side and the R gear block on the right side of the model.
Best way to make sure is that the gear blocks have (1) side that is strait and (1) side that has an angle-shift mid way in the block. The strait side should always be facing inward to the model and the angle-shift side should be facing out ward. [ see photo 1 ]

} I used an exacto saw blade to make the horizontal cuts and a new scalpel / exacto blade for the vertical cuts. [ see photo 2 ]
Make your horizontal cuts first, and use the original foam shelf of the gear area to act as a depth gauge for you cuts. Try to go only deep enough to reach where the vertical will be. You will go thru the model and into the air intake path, but if done just right, the opening will be minimal and in an area that will be covered by a plastic plate. [ see photo 3 & 4 ]

Side Note : I stayed with the original height for the stock landing gear which sets the main wheels sticking out below the fuselage about half the wheel's diameter / 23mm. The new retract gear and struts also raise your ground stance by 3/8 inch / 9.6mm from the stock location. You can lower your cut to set the gear block further in the fuselage and try to make the wheels flush with the fuse, but keep in mind that doing so will lower your ground stance and rotation angle.

[Arcangel]

When you are done fitting the landing gear blocks in the fuselage, we will need to do some more work on the gear blocks....

} Make sure your blocks are level. The outer corner of the block facing out ward from the model, highlighted in yellow arrow, should be flush to the curved surface of the fuselage. The inner corner of the block facing in ward to the model, highlighted in orange circle, should be set to a depth of 5.5mm from the bottom surface of the lower main fuselage. [ see photo 1 ]

} You will need to mark the tab, highlighted in the yellow circle, that extends into the air intake area and grind or file it off. [ see photo 2 ]

Side Note : On the out ward facing sides of the gear blocks, highlighted in purple circles, you can add foam to increase the surface area for gluing or just use more glue to fill in the gap. [ see photo 3 ]

[Arcangel]

Now that the mounting blocks for the main landing gear are fitted to the fuselage, you will notice that there is a BIG gap that needs to be filled. The FreeWing / E-Flight style retracts are not as deep as the stock Banana Hobby landing gear, so now we have to address their differences. [ see photo 1 ]

There are two ways we can do this :
1 } You can use extra pieces of foam laminated in the mounting area
2 } You can use spray in expanding foam and let it conform to the open space.

I chose to use the extra foam pieces because once you get done fitting the gear blocks, the inner walls of the fuselage are fairly thin and there is the possibility that the expanding foam could bulge or worse yet, burst into the air intake area.

At this point, I was able to place my retracts in the fuselage and asses how they're going to look and operate. I noticed on mine that the extended length of the struts moved the wheel back just enough to rub against the back of the gear bay. After several test cycles, I found it to not have any affect on the gear itself, but I decided to extend the back of the bays by 1/8 inch to give the wheels clearance just in case. [ see photo 2 ]

Side Note : I chose to mount my main gear with the wheels facing out ward as oppose to the scale location of them being in ward. I wanted to give my model the widest stance possible.

[Arcangel]

From this point, we are going to change steps in the build and do a forward fuselage reinforcement mod before continuing on to mount the nose gear block. It may seem to add a little confusion to the process at first, but it will make some of the other mods that will be done later on so much easier to complete; especially the nose gear mounting block.

This mod adds a 1/4 inch O.D. carbon fiber tube to the lower halves of the front and main fuselage pieces. { I have to apologize here as I forgot to get any " before " photos prior to doing the mod }

} You measure center on the lower lip of the front lower piece of the fuse and drill a 6mm hole all the way into the landing gear bay. On the lower main fuse, you measure center on the recess area for the glue joint of the forward fuse and drill the corresponding hole all the way back to the receiver box

} Now you can cut your tube and trim it to length. I started with a tube length of 8-5/8 inches and placed it in the main fuse section. I then fitted the front fuse section onto the main section and marked off how much of the tube extended into the landing gear bay and trimmed it off accordingly. { The tube should span the distance from the forward wall of the receiver box to being flush with the aft wall of the nose gear bay. [ see photo 1 ]

Side Note : You can get a better feel for this mod by watching the 2nd build video for the LX YF-23 done by the RC Informer on Youtube. Please keep in mind that for now, we are only doing the lower half of the fuselage pieces. I will address the upper halves later on.

} Now give the tube a lite sanding to rough up its surface and glue it in place. [ you can pick which half to glue it in ]

} Once the glue for the carbon fiber tube has dried, you can glue the lower forward and main sections of the fuselage together. By gluing the lower fuselage pieces together now, you can better align the forward fuselage piece to the main section and reduce the inherent gaps that form at the fuselage seams when assembling the " completed " front and rear halves of LX / Banana Hobby models. Also, there is a method to the madness here as I have stated at the beginning of this post. [ see photo 2 ] :)

[Arcangel]

The next mod to be done is for the battery bay [ see photo as referenced in the steps below ]

This mod lets you use (1) 6S battery instead of having to trouble with (2) 3S 4000 mah packs connected in series. When I originally did this one on my model, I used an old style Admiral 6S 5000 mah pack as my test subject for fitting.

} To start, take your exacto saw and cut away the foam block standing up from the lower front half of the forward fuselage piece as high lighted in the brown circle and sand that area flat to your liking.
A personal note, I did not like how the original velcro battery straps for the model were done, so I replaced them with a battery strap left over from a FreeWing ME-262 that I had previously lost.

} Now install the battery bay plywood floor and insert the battery strap after the glue has dried. At this point I went ahead and glued down my bead mat material, that anti movement stuff your wife puts in the kitchen drawers and pantry shelves. I used a piece that extended from the front of the battery bay / cockpit all the way back to the glue seam of the forward and main lower fuselage pieces. You can go back further to the receiver box if you like.

} Now you can dry fit the top half of the forward fuse to its lower half and secure it in place with a velcro strap or a lite bunjee chord. Here is where you begin to fit your battery of choice into the fuselage by sanding away the area high lighted in the lite blue circle.

} Once you are satisfied with the fit of your battery, you can now glue the top half of the forward fuse to the top half of the main section.

Side Note : The mold used to produce the top half of the forward fuselage is not quite of the same quality as the molds used for the rest of the model and you can see it clearly in the detail of the panel lines and with its fit to the top main section. I had to fiddle with mine a fair amount to get a good fit and align as much of the panel details as possible.

[Arcangel]

Now it is time to finish the forward fuselage reinforcement mod by adding the last two carbon fiber rods to the upper half of the model.

} The length of the rods can be 8" to 12" depend on your personal taste. Make sure you have enough rod to extend from the open canopy area back into the main fuselage side walls. [ see photo ]

} Now center the rods on the fuselage side walls and trace out their path and you can begin cutting away the foam to create a trough for the rods. [ You only need to cut deep enough to embed the rods flush to the surface of the foam. ]

} When you are satisfied with their placement, go a head and glue in the rods, you can use T-pins to hold them in place until the glue has dried.

[Arcangel]

From here we can finish installing the retract nose gear. This mod is a little more tricky from the main gear in that it is highly dependent on your personal preferences.

The natural curvature of the YF-23 model makes it difficult to plan out exact measurements for how to set the nose gear strut and tire. The original nose gear and mounting position in the forward fuse gave the strut a forward rake angle that was to say the least, pretty steep. I personally did not care for it, so I tried to tilt the nose gear back so that I could achieve a more straight or perpendicular angle on the nose strut. My choice of using the nose gear from a FreeWing Mig-21 also added some complications to the model as it uses a 45mm diameter nose wheel, which is now the same diameter as the mains. The increase from the stock Banana Hobby nose wheel at 33mm diameter to the now 45mm diameter will make the nose wheel protrude further down from the forward fuse during flight. The problem here is that the forward fuselage does not give you much room to carve away foam to try and recess the gear block into the model before you hit the battery tray floor and the battery strap.

} To begin I set the back wall of the gear mounting block flush to the back wall of the nose gear bay. [ Here you have to pay close attention to keeping the center line of the nose gear straight with the center line of the fuse ]

} I traced out my cut away area from the nose gear mounting block and then fitted the block to the forward fuselage. I set the front edge of the nose gear block at the original level of the model's stock location as noted in the light green circle and cut away / lowered the back edge of the foam for the mounting block to try and tilt back the nose strut to a more perpendicular angle as noted in the red circle. [ see photo 1 ]

} When I was done cutting the foam and fitting the nose gear mounting block, I ended up punching through the fuse into the battery mounting area and had to add some foam back in to fill in the gaps and give the mounting block something to stick to. The foam used ended up being from the " thin " side wall of a coffee cup or roughly 3mm / 0.118 inches as noted in the orange circle. The depth of the rear cut for the mounting block as noted by the yellow arrow is 5.2mm / 0.205 inches. [ see photo 2 ]

A personal note, the best I can say here is to eye ball the model's stance and try to find the best balance between the model's posture and its natural curvature. I am quite pleased how the measurements for my nose gear angle turned out, your mileage may vary.

[Arcangel]

The next few tid bits are not really mods but more like tips to make working on the model better.

} The first is adding some pull tabs to the EDF cover so that it is not a P.I.T.A. to remove. I used standard duct tape to make the tabs and attach them to the cover piece [see photo ]
If you trim them just right, they will be completely hidden by the EDF cover mounting tabs and no one will suspect they are there. :)

[Arcangel]

The next tip covers the routing of the servo extension wiring.

When I routed my wires back to the aft section for the elevators, I noticed something peculiar. If you run the wires in the areas specified by the manual as noted by the purple circle, it will create a gap in the seem near that area where the two fuselage halves glue together. [ see photo 1 ]

} To reduce that gap in the glue seams, I sliced the side wall of the foam in that area with an exacto knife and embedded the servo wire flush into the foam wall. [ see photo 1 ]

} When the all the servo wires make their way into the receiver area through the ESC bay, I stacked & glued the wires side by side each other on the fuselage inner side wall to help keep them from becoming a rat's nest [ see photo 2 ]

[xviper]

The next tip covers the routing of the servo extension wiring.

When I routed my wires back to the aft section for the elevators, I noticed something peculiar. If you run the wires in the areas specified by the manual as noted by the purple circle, it will create a gap in the seem near that area where the two fuselage halves glue together. [ see photo 1 ]

} To reduce that gap in the glue seams, I sliced the side wall of the foam in that area with an exacto knife and embedded the servo wire flush into the foam wall. [ see photo 1 ]

} When the all the servo wires make their way into the receiver area through the ESC bay, I stacked & glued the wires side by side each other on the fuselage inner side wall to help keep them from becoming a rat's nest [ see photo 2 ]

I've left my model at this stage and haven't been back to it since due to the daunting task of running all those extensions. Your pictures and hints are very helpful.

[Arcangel]

I was finally able to get some more time to put in on this project and made some good progress since our last visit.

Here is a simple mod to the nose cone that makes it more secure to the fuselage and help prevents it from flying off on its own. [ See photo ]

} Instead of using the (4) horribly weak magnets supplied with the kit located at the top and bottom of the nose cone & fuse, I opted to replace them with (8) stronger magnets from K & J Magnetics. These are the same size dimensionally, 3/8 x 1/4 x 1/8, and are listed on the website in the N2 strength class. Each magnet has a strength of 8 oz / 1/2 pound of lifting capability which should give the nose cone some pretty good mounting force to keep it attached during flight. The magnets are mounted length wise in the nose cone's side walls with their counterparts in the corresponding positions on the fuse.

Side Note : When you mount the first set of magnets, make sure you note their polarity and mark the mating pair so that when you glue them in you do not get any magnets trying to " push " away your nose cone.

[Arcangel]

I was finally able to remove all the paint from the fuselage and will be getting her ready to repaint with something more durable than the rubbery crap BH / LX used at the factory. [ see photo 1 ]
At this point I had to choose which color scheme I was going to go with for my YF-23, PAV-1 the Black Widow II or PAV-2 The Grey Ghost.

I chose to go with PAV-1 for a few reasons :
) The decals that come with this model are for PAV-1 and you can still get a new decal sheet from BH when they are in stock. Some of the decals on the sheet are not to scale in size or color, but if you have a color laser printer and a few sheets of water slide transfer paper, you can redo the inacurate ones and apply them OR just stick with the stock decals and be done with it.
) The YF-23 has an incredibly small / razor thin profile when it is coming at you or heading away from you and my eyes are not as good as they use to be, plus the U.S. Air Force tactical grey camouflage used on the actual aircraft would be very effective on this model. [ kind of like how the FreeWing 90mm F-15 Eagle is on an heavy overcast day ]
) I personally like the Black Widow II color scheme over the Grey Ghost and it is less of a hassle to repaint. :)

} To remove the paint I used Testors model paint thinner. It is the most effective paint remover for RC foamies I have found that does not require pre-prep work of the model or post work follow up to clean the model and it does not damage the foam in any way if applied with a gentle rub. The paint I am choosing to repaint with comes from a color match I had done for my FreeWing Panther. The dark grey is similar to the BH / LX original paint but a little darker in tone and without that purplish hue to it. You can see the difference in the paints when laid atop each other for comparison. { see photo 2 ]

A personal note, The method I use to remove paint is probably the most effective way but certainly not the " BEST " way due to its cost factor. Testors thinner runs $10.00 per 8 oz / half pint. :Scared: That makes this stuff VERY expensive and possibly cost prohibitive for some folks.

Side Note : I plan to to give the entire model (1) or (2) coats of Minwax Polycrylic to give the paint something better to adhere to and maybe offer a little protection to the foam against the heat and sun light