Questor: The Modular Model Airplane Project

The following is a checklist of things to be done to complete my airplane. This checklist will be a living, breathing document, updated as needed to provide an indication of how far I have come and how far I need to go. Some details will likely be eliminated from the items I have completed thus far, since I am getting a late start on creating this checklist, but I will do my best to keep this in sync with my progress. After all, it will be the actual checklist that I work from.

Keep in mind that any notes here are notes to myself.

Horizontal Stabilizer:

Trace wiring pattern in upper laminate to produce a permanent record for future reference.
Lightly sand lower balsa laminates.
Sand lower center (plywood) mounting plate at a gradual angle to meet with the thickness of bordering balsa laminates.
Cut hinge gap recesses into lower balsa laminates.
Test spread of wood glue on scrap pieces to determine perimeter clearances for lamination. Use same press rig that will be used during assembly.
Define desired perimeter for wood glue and mark regions to be glued. Be sure glue will not interfere with contact points, LEDs, cut-outs, hinge slots or mounting holes.
Center laminate:
Perform work on "press rig" - heavy, flat wooden shelves...
Sand areas as desired for a good, flush fit. Create indentations as needed in lower laminates for wires, as needed. Sand fin slot stiffeners to ensure flush fit.
Position ALL pieces to ensure proper placement of center piece.
Pin or otherwise secure bordering laminates in place
Ensure copper traces are CLEAN (possibly pre-tin before laminating)
Remove center piece and apply wood glue to marked gluing regions
Place center piece in position and ensure proper placement while applying pressure - lots of pressure (within reason) until firmly seated.
Remove pins or other obstructions from bordering pieces, and remove bordering laminates.
Place upper pressing shelf on top of the assembly and allow glue to dry. Ensure the center of gravity of the shelf is placed directly over the center laminate.
Remove pressing shelf and inspect for overspill. Remove any residue.
Use thin CA glue to complete the lamination process around perimeters where wood glue did not reach. AVOID HINGE SLOTS AT THIS TIME. Avoid power contact access holes. Apply CA to mounting holes to increase rigidity and strength.
Remaining laminates:
Trial fit remaining pieces - adjust as necessary for a good fit.
One at a time:
Apply wood glue to marked gluing regions
Place piece into position and ensure proper placement while applying pressure until firmly seated - remove any unexpected overspill immediately.
Place flat pieces of wood, roughly the same size as the laminates (large enough to cover completely) on top of the laminates to serve as a seat for the press shelf.
Place pressing shelf on top of the assembly and allow glue to dry. Ensure the center of gravity of the shelf is placed directly over the center laminate.
Remove pressing shelf and inspect for overspill. Remove any residue.
Sand all edges to true the alignment of the laminated horizontal stabilizer.
Sand/cut the leading stabilizer corners to desired radius.
Sand the leading edge of the horizontal stabilizer to shape.
Use this CA glue to complete the laminate process around perimeters and inside cut-outs where wood glue did not reach. AVOID HINGE SLOTS AT THIS TIME.
Stab is ready for final sanding.
Possibly cut a couple large holes in structure to reduce weight
Final Steps:
Sand trailing edge straight - the harwood seat area is a tad oversized.
Precision sand fin tab slot for wider clearance for sealer and paint
Mask off balsa portions about 1/4" back from all hardwood joints - also mask off electrical connector
Apply black paint to exposed hardwood areas, including inside fin tab slot - allow to dry and lightly sand
If necessary, determine a means of supporting stab in a way that counters any warpage before applying sealer, if earlier moistening did not work
Apply spray-on polyurethane sealer to hardwood sections of stab - be sure to include tops of mounting bolt seats - allow to dry, lightly sand, repeat if necessary
Carefully sand fin tab slot for proper fit
Remove masking and carefully sand any raised edges down flush with balsa surfaces.
STOP! Test visibility of LEDs through orange Monokote to determine adequacy. This will determine covering design and method going forward
STOP! Determine if covering should include stab seat area
If seat area is to be covered, remove hot glue plugs over embedded electrical contact points before covering.
If seat area is to remain uncovered, apply hot glue or silicone plugs to embedded electrical contact points where the connector is attached.
Lightly moisten concave side of warp to get the warp to straighten itself out. I want to seal in some of this moisture, so work quickly.
Cover bottom section, first, being careful to seal closely around electrical connector (or leave seat uncovered)
If seat is covered, cut out holes through covering for mounting bolts before proceeding with the top
Cover top completely with orange Monokote. Carefully trim around fin tab slot for non-interference. Perhaps cut back to leave black harwood areas exposed.
Apply black trim as desired, being careful not to span LED pockets.
STOP! Complete preparation of stab seat on tail boom before proceeding.
Insert one stab mounting bolt at a time: screw down too far, then back off a little at a time until stab is able to slide firmly in place
Mark and cut hinge slots
Temporarily install hinges and check alignment - adjust as necessary
Sand elevator to shape, beveling leading edge for proper clearance - find sanding tool I used for the Eagle II
Cover elevator in orange Monokote. Apply black trim as desired.
Temporarily install hinges and attach to stab. Install control horn on elevator.
Permanently install hinges in stab and elevator.
Additional considerations:
  • Braces may be added to the top of the stab to support fin against lateral stresses.
  • Think of some way to plug the power connection access holes to protect from debris, paint, etc.
  • Consider whether solder should be applied to power access holes, before or after lamination. May be a good idea to do it before in the event the copper fails to hold up.
  • Determine how to seal perimeter of connection access holes without affecting contact points (i.e. how to mask the copper).
  • Trace all wiring patterns in the upper laminate prior to lamination of the horizontal stab so that I have a reference pattern in case I ever need to drill or cut into the stab for some reason.
- The copper traces are thin and the adhesive backing becomes unglued when heated excessively. The process of REMOVING a conductor from a connection point should be performed with extreme care to ensure the integrity of the copper is not compromised.

Vertical Stabilizer

Sand fin sides - remove about 1/64" thickness
Trim off stiffeners even with top of stab when fin is inserted
Trial fit stiffeners and trim as necessary for a good fit
Laminate stiffeners to fin sides using gap-filling CA glue - clamp together and allow to dry
Lightly sand stiffener surface, flat
Sand slot in horizontal stabilizer assembly for a precision fit with the descending fin tab
Sand slot in tail mounting plate for a drop-in fit with the descending fin tab (precision not as important here)
Cut 3/32"x1/4" basswood strips to length
Sand outer corner of basswood strips round, or at 45-degree angle
Glue basswood strips to sides of fin along marked line
Trim and sand basswood strips to proper shape
Mark and cut hinge slots for a snug fit
Possibly cut some holes to reduce weight
Sand fin assembly to shape - round tab corners and maybe lop off fin point
Set fin assembly aside until construction of tail boom
STOP! Complete tail boom assembly before proceeding.
Install flat hold down on boom in front of fin - support with additional hardwood block if needed
Cut nose section off front of fin below stabilizer rail to square off fin tab.
Extend nose with hardwood and/or plywood to extend over flat hold down
Mark and drill hole in nose for locking pin
Measure and cut steel locking pin and install in nose - secure with CA glue. Rough up glue end first.
Assemble tail and mark where fin tab locking pins will align with holes in rear of boom
Drill, cut and sand slots in fin tab to accommodate fin tab locking pins (to be installed)
Widen holes in fuselage to accept bamboo skewer for a press-in fit.
Install and cut skewers into holes - select strong skewer - cut slightly undersize - secure with thin CA
Cut slots in fin to accommodate skewer pins
Mark and cut hinge slots for a snug fit
Temporarily install hinges and check alignment - adjust as necessary
Sand rudder to shape, beveling leading edge for proper clearance - find sanding tool used with Eagle II
Cover rudder with orange Monokote
Install control horn and hinges. Ensure control horn is on opposite side of fin from elevator control horn.

Tail Boom

The tail boom consists of two main sticks, each a lamination of two 1/4"x3/8" basswood sticks, joined at the rear by the Tail Section. One of the main boom sticks will carry power conductors for lights in the tail, and the tail section will consist of a mounting plate for mounting the tail feathers, locking pins for securing the tail feathers, and a tail skid (no wheel).

The right-hand boom stick will carry both power lines for the tail lights.

Boom sticks - Right-hand side:
Notch out fuselage end of upper laminate stick for female connector
Trim a piece of 3/32"x1/4" basswood strip to partially fill notch
Mark the path of the wires along the upper laminate stick of the right-hand boom stick
Cut grooves with small router bit and drill holes to complete wire path
Cut two pieces of wire to approximately (at least) the required length
Solder wires to female connector
Install female connector into notch - hot glue it in place - and thread wires through track and holes
Glue (tack) wires in place from fuselage end down to before they enter the tail section
Cut another basswood strip to complete connector housing
Glue basswood strip into place and sand flush with stick
Determine and mark locations of copper strips for connectivity to tail section
Cut pieces of wire and create a "Y" branch for wires to exit at marked inside and outside locations
Glue (tack) all wires in place with CA
Clearly mark wire paths along and through stick
Re-work the mess I made out of the wiring on the tail end of the upper stick.
Lop off the upper boom stick at the rear of the fin seat line.
Laminate the upper and lower boom sticks together using epoxy - clamp together and allow overspill to bead up. Cut off epoxy bead from sides before it turns to stone - be VERY careful not to nick or cut wires!
Tape down wires extending from inner wall to protect them during tail assembly (they will not be completed here)
Mark location of copper strips for outer contacts
Cut copper strips and apply them to marked areas on outside (only!) of upper and lower boom sticks
Solder appropriate wires to copper strips in upper and lower boom sticks - make sure polarity is correct
Cut out cover plate for laminating over copper strips
Mark and drill holes in cover plate
Apply solder to connection points and test continuity in all wires
Glue cover plate in place with epoxy(?)
Trim cover plate and sand flush with edges
Boom sticks - Left-hand side:
Lop off the upper boom stick at the rear of the fin seat line.
Laminate the upper and lower boom sticks together using epoxy - allow overspill to bead up. Cut off epoxy bead from sides before it turns to stone
Tail section:
Build a two-pin female connector and install on horizontal stabilizer
Fill contact points with hot glue
Cut notches near fuse end of both boom sticks for formers to be installed later
Put sticks in jig and clamp tail ends of boom sticks together
Cut two pieces of 3/16" thick balsa to make laminated stab mount seat
Gut groove for wire path in lower laminate and glue in place
Drill hole in upper laminate, thread wire through and glue (laminate) in place
Make four-layer laminate of 3/16" balsa sheets to fill area between boom sticks in the tail end and glue in place
Make jig to support tail section on its side for drilling pilot holes for fin locking pins
Mount boom in jig and drill two small pilot holes for fin locking pins
Remove boom from drilling jig and place in (new?) building jig and draw STRAIGHT lines in proper alignment for cutting fin tab slot in boom filler
Carefully cut the fin tab slot into the filler block using the band saw
Carefully trim away any unnecessary filler block and sand fin tab slot to proper clearances. Keep (or add) filler as necessary to accommodate tail skid
Cut stabilizer mounting plates to approximate size and glue in place - devise appropriate technique to ensure proper alignment! Be sure to trim clearances for power connectors!
Use drill guide to mark holes for stab mounting bolts in mounting plate
Drill and tap holes in mounting plate, starting with tiny pilot holes
Insert bolts and mount the stabilizer - if done right, it should just fit! Experiment with bolt tension.
Plug male connector into female connector in stab, loosen mounting bolts, apply CA glue to male connector, slip stab over bolts and press down to glue connector in place
Remove male pins and add new pins to wires from boom to complete the connector, observing polarity.
Tack wires down flat with CA glue.
Test the circuit!
STOP! Complete horizontal stabilizer before continuing!
Use CA debonder to separate tail boom electrical connector
Prepare the area around electrical connector for re-attachment
STOP! Determine locking pin assembly design and assembly procedure before continuing!
STOP! Before continuing, make tail boom jig to properly flex the booms during completion stage
Determine remaining procedure (stab mounting bolts, fin locking pins, etc.)
Douse fin tab area with CA glue (maybe polyester resin is better?) to harden it up (and seal it). Sand fin slot back to proper clearances (grit teeth if you have to)
Trial-fit tail assembly - trim fin tab as necessary for flush fit, top bottom and rear
Tail Fin: Following final sealing and sizing of fin tab slot
Select dowel to use as fin tab retaining pin - cut to approx. twice the length needed.
Insert stab and fin assembly IN PLACE and use a center punch through rear pre-drilled hole to mark where to drill the fin tab
Remove stab and fin and drill through rear retaining pin hole to size for dowel pin
Drill through fin tab at marked location
Trial-fit the dowel pin and sand for snug fit. Remove dowel pin.
Remove fin and cut rear of fin tab to open a slot to the dowel pin hole
Insert dowel pin and install fin for trial fit - sand for smooth operation while retaining positive contact between slot in fin tab and the dowel pin.
Cut dowel pin to proper length & angle.
Insert dowel pin and glue in place with slow-cure CA glue: insert pin about 3/4 in and apply glue inside recess on other side and around rim on insertion side, then press in, align, and wipe off excess.
ENSURE glue is dry and no residue worked into interior.
Cut lower tail gusset to approximate shape and glue it in place
Cut small piece to cap off face of fin slot.
Fire up the Dremel and shape the boom's ass - lighten it up!
Set tail boom assembly aside until construction of fuselage (at which time holes for locking pins will be drilled)
Additional considerations:
  • Determine how control rods will mount to boom and mark all mount points and pre-drill any required holes and pre-cut any required grooves.
  • On finished airframe, CLEARLY mark wire paths on right boom (use pin striping).
  • Right-hand boom may not bend as easily due to additional epoxy in wire path - ensure symmetry when joining at the tail.
  • It was a fluke that the power lines for the tail wound up in the right-hand boom stick, but this is good, since the muffler is on the left and prop wash will carry any fuel splatter to the top of the right side of the vertical stabilizer, thus protecting the outer contact points somewhat.
  • Hot glue can be used to plug and protect unused exposed power connection points.



Landing Gear











I may have been myopic in my design considerations. Perhaps it is a bit late to consider any radical changes at this point, but due to the modular nature of this airplane, a new tail boom (and tail section) could be designed and built, independently, in the future.

Instead of drawing the tail boom sticks together to a point at the tail, they could be brought straight back. This would require only two thin plywood segments in the horizontal stabilizer for mounting, and mounting bolts could drive right into the boom sticks. Desiging a slip-in electrical connector would be simple. The only complex piece would be how to mount the fin to the stabilizer, and how to run the control rods.

Further analysis might reveal that this would actually be a more complicated design, but it might be worth pursuing in case there is a simpler solution based on the concept.

Items needed:

Don't use wood glue on balsa wood - I think it is water-based, and it causes the balsa to swell.

emry boards

CA glue - slow and fast

New alternator drive and alternator