NMPRA

I will use the next series of posts to document the process I use. If you have any comments or additional details feel free to add to this chain.

I start with mounting the wing. The MFL has some counter sunk recesses molded into the wing. The front bolts are designed for 1/4-20 and the rear for 10-24s.

Fit the spar joiner tube by cutting it to the proper length and join the wing halves by sliding them together and taping them in place.
I have designed some small tools to aid with drilling holes consistently (at least that is the attempt). I use these guides to drill the pilot holes in the wing. I use a 3/16" drill bit for 1/4-20 threads and a #25 Drill bit for 10-24 threads. Drill the pilot holes in the wing.
Place the wing into the saddle and mark the bolt locations on the fuselage. The center line of the wing should line up with the center seam line of the fuselage and if lined up it will be perfectly straight.
Next install ply backing plates to accept the threads inside the fuselage. Normally, I use 1/8"-1/4" aircraft ply cut into 1/2"-5/8" square pcs and these are 5 min epoxied onto the existing ply plates installed when received. The hole marked locations can be used to make sure your blocks are centered over the best location for the threads.

MFL cont:

Next tape the wing in place. Line up the center line of the wing with the center seam of the fuselage and tape the wing down as shown. Once you are happy with the alignment, flip the model over and add additional tape along the fillets securing the wing to the fuselage. The reason for this is to keep the wing aligned during the drilling and tapping process. I start with one of the front bolts. Using my guide and the 3/16" bit, I drill through the wing into the fuselage and the ply plates. Next I tap that drilled hole and install a 1/4-20 bolt. I only do one front bolt at this time and switch to the rear bolt opposite to the first drilled and tapped hole. Follow the same process with the #25 bit and the 10-24 bolt for the rear before finishing the other two remaining bolts.

MFL cont:

Next I will work on the rudder horn and stab install. I use a long 3/32" drill bit (available from McMaster Carr) to open a passage through the hood molded into the fuselage. Once done I mark a center line for where the horn will be located using the drill bit and the bottom cut of the rudder for alignment. Next I prepare the supplied horn for installation. This requires some trimming and cleaning up. If you have a different method feel free to use it.

Next, I install the stabs and the elevator horn. Clean out the holes in the fuselage where the carbon rods pass through. I use a 3/16" bit backwards using my hand to clean out the holes. Don't get crazy here and use a drill, there is a small amount of flashing during the molding process that needs to be removed. If you have a 3/16" reamer this will work as well. Again install backwards and pull through the opposite hole to keep them aligned. Once the holes are free of flashing, I install both carbon rods. A slight bevel on the leading edges of the rods is helpful as well. These rods are too long in most cases and will need to be trimmed to length. I fit one stab 1/2 at a time. Install the carbon rods and work on one side first. Square up the root of the stab and the elevator clearance using whatever method that works for you. I use my 12" sander! A simple sanding block and some care should be used to obtain a good fit and enough clearance for the elevator to freely operate. Once the right 1/2 fits well I square up the left and then after both halves fit well I trim the rods. To trim the rods I fully seat the right 1/2 and push the rods through until they hit the stops molded into the stab. Only a small amount of force is needed here, don't push out the stops. Next slide the left stab onto the front rod only and measure the distance from the root to the fillet. This is the amount that needs to be trimmed off the rod. I use my Dremel and a cut off wheel to trim the carbon rods. Double check the fit before moving onto the rear rod and repeat the process for the rear carbon rod.

MFL cont:

Once you are happy with how the stab fit, move onto elevator horn. The previous post shows how I would like to see the stabs fit the fuselage fillets. You should do your best to make these fit as tightly as possible to prevent any undue wear caused by ill-fitting stab 1/2s. One exception to the above pictures is the clearance for the elevators. Normally, there is a small gap that will prevent any binding. With the stabs in place mark the locations of the elevator joiner on the fuselage and make the appropriate cut outs. I use a Dremel and small endmill. The cut-outs should be big enough to prevent and binding or limited travel and yet be small enough that they don't blow through the fillets on the fuselage.

Next I move onto the assembly of the elevator joiner. BTW, this was designed by Jerry Small and created by Dub Jett, for those that think someone else created this part. There is a correct orientation to the joiner and care should be taken to mark and install it correctly. The 4-40 screws that lock the joiner into the elevator are at an angle. And the angle is representative of the head of the bolt being parallel to the surface of the elevator. This is critical to having the bolts match the surface of the elevator.

MFL cont:

This space reserved for Firewall forward pictures.

MFL cont:

The following set of pictures show the process I use for servo tray assembly and installation:

I assemble the supplied servo tray by adding balsa support to the back side. Two long strips of 1/4" triangle stock are glued to the bottom of the tray along the long sides to provide a larger gluing surface against the fuselage. The wide side of the triangle is glued to the tray using MED CA. Next, I install balsa backing blocks to the area where the servo screws pass through the tray. Lastly, I soak the edges of the tray and the holes with thin CA and set it aside to cure. Tom has some installation tools available that allow for proper position of the tray in both front to back as well as depth. I will add pictures in the future, next time I build one. Before installing my tray, I mark it's position in the fuselage relative to the tool shown below. I sand the sides of the fuselage with 80 grit and wipe clean with alcohol prior to gluing the tray in. Lastly, I install some 1/16" adhesive backed foam under the tray to prevent chaffing of wires against the glass. I use Shoe Goo to install my trays. I have found that, epoxy or hard mounting trays allows for vibration to attack servos and servo cases. The Shoe Goo is next to impossible to remove. If you haven't tried it I recommend it.

NOTE: if adding a charge jack utilizing small holes, make sure it doesn't pass through any carbon. If it is located near carbon, allow for the entire charge plug to exit the airplane. IF not, a fire will mess up your day.

While the main tray is set aside to dry. I work on the wing. The aileron tray is handled in the same manner. Balsa screw supports are added to the under side and the holes and edges are soaked with thin CA, set it aside to harden. Next use the install tool to mark the servo location and cut out the wing to accept the servo. Add the vertical support to the servo tray as shown. This support is used to prevent the lower skin from collapsing around the servo. The tray is centered in the opening and glued in place using 5 min epoxy and microballoons. Once dry I move on to finishing the torque rods.

Mark the bottom skin and make a clearance hole for the 4-40 x 1.25" bolt to pass through. Add a hole near the end of the torque rod to gain access to adding JB weld to the torque rod during the assembly process. Clean up the top skin to allow clearance for a nut driver and a 4-40 nut. Install the screw and nut while the JB weld is curing. Make sure everything is tight and set aside to dry.

MFL cont:

One scary task is drilling pilot holes for landing gear. Scary, because if you have ever done it, you probably drilled through the top skin. Yep, I have been there did it. SO, I created a 3D printed drill block to act as a drill stop and place the holes in the proper place.

I use a #49 drill bit along with my 3D printed block to drill all the pilot holes for the landing gear.

Dan Kane invited me to chime in here on his Miss Foxy Lady build thread to illustrate a fuel tank “wedge and cradle” mounting system that some of us use. I’m not certain, but I believe this was originally conceived by Richard Beers and then adopted by Dub. Dub showed it to me. Because I have a CO2 laser cutter, I took the idea and ran with it reproducing parts and evolving the design over time. The main thing I like about this semi-rigid mounting setup is, simply, I just find it easier than the other ways of holding in a fuel tank such as Velcro and/or tape and foam. With this wedge and cradle, the tank is kind of locked into place. Initial installation requires more work and prep in the shop at home, but out in the field at the races it has been 100% maintenance-free. It’s also repeatable which may be good for the Jett engine because apparently, fuel tank location/height is more critical with the Jett. The height of the wedge has also evolved to position the tank at the correct height for the best runs with a Jett engine. At this moment, I’m not sure who out there is running this setup, though I know Dub is and all my MFLs are set up this way (for whatever that is worth). I have also made these parts for some others. I am not necessarily advocating this setup. It’s just what I use and Dan asked me to share it here.

On the MFL, first thing that has to be done is grind away the glue bead in front of the canopy. I CAREFULLY use a Dremel with a sanding drum followed with sandpaper by hand. I then reinforce the joint with a strip of lightweight glass cloth and resin.

Next, prepare the tank. Dub favors the Jett 6 oz. slim, round tank and that’s what I use. I wrap the aft end of the tank with a couple wraps of kapton tape, an anti-abrasive tape for electronics. I then glue together the parts of the wedge (comprised of two outer pieces of lite-ply and two inner pieces of 1/8” balsa) and use Shoe Goo/Zap Goo/E6000 to glue the wedge to the top of the tank (the sticker noting the top of the tank).

The cradle is shaped to fit the fuselage and position the aft end of the tank about 4-12” to 4-3/4” aft of the wing LE. This also allows the servo tray to be positioned about 1/8” behind the tank for tank removal/installation. Use more Zap Goo to glue the cradle into the fuselage temporarily setting the tank and wedge into place to perfectly position the cradle.

From Tim Lampe

Continuing with tank installation, cut some foam wedges to keep the front of the tank centered. Again, I use Zap Goo to glue in these wedges. One more piece of foam is used to hold the tank up when the wing is mounted.

Tim Lampe

Note: after grinding the seam away and sanding the inside of the fuselage, it is a good idea to add some clear tape to the outside of the fuselage to prevent glue from running out on the outside. I have learned the hard way, and now this is a common practice when grinding seams or adding epoxy to the inside of a finished fuselage.

Tim: Thank you for the awesome picts!!!

Dan asked me to comment on battery placement and fuel line routing. Well, battery location (and servo tray location) can very much help with C.G. to minimize any additional nose or tail ballast to achieve the desired C.G. I’ll let Dan talk about the recommended C.G. location, but I strive for about 2-15/16” to 3” (aft of the wing leading edge at the middle of the wing). With a Jett engine, this C.G. can be achieved by putting the battery (I use a 2S 6.6V LiFe) in the nose in the space behind the firewall and ahead of the cutout for the wing. I use epoxy to glue in a battery plate made from lite-ply and attach the battery with Velcro. The plate is sized to fit a battery while also being low enough to not interfere with the fuel tank or lines.

I’ll note again that, even I admit that some of the methods I use seem to be more complicated than necessary. I know other guys use a popsicle stick on the fuel tank or foam to stuff the battery in the nose, but also again, I don’t mind spending extra time in the work shop if it prevents issues at the races and this is what works for me.

Tim Lampe