*** Andy Steere's Alfa Mig-15 "Build" Page***

These pictures show the assembly of the Alfa Mig-15 Electric Ducted Fan (EDF) as it progresses.

Assembly Notes:

  • To provide cooling for the motor, which is otherwise completely enclosed, eight 9/64" holes were added around the perimeter of the housing. These were drilled at an angle so that air coming off the fan would enter.
  • To provide enough exit area, the back of the motor tailcone was hollowed out.
  • After hearing several reports of wing failures, especially with high-powered motors, I decided to strengthen them.
  • Looking at the wing root, the spar appears to be 3/8" thick, but in reality is only this thick for the first few inches. Once beyond the joiner wire, it is only 1/8" balsa.
  • 5/32" carbon fiber pushrods (tubes) from Central Hobbies fit the joiner wire perfectly, and required only a little drilling out of the first few inches of the spar. These are incredibly strong, quite light (the epoxy to glue them will weigh as much), and pretty easy to install.
  • To be effective, the CF tubes must be glued to the full length of the spare. I used 12" long sections of rod and 30-minute epoxy to attach them. Before installing, I dripped some epoxy down onto the spar itself, then put an eyedropper full of epoxy down the spar hole. I then coated one side of the rod (the side that will contact the spar) with epoxy down to where the 3/8" wood starts, fulling coating both sides for the last 3-4".
  • Once the epoxy had set, I came back and dribbled a little Gorilla Glue (polyurethane) down onto the cf tube, then sprayed a little water. This foamed up nice and surrounded the cf tube in several places.
  • Wing weights increased to 34.6g for the right wing and 35.7g for the left wing, including the CF tube and all glue, as opposed to 27.9g and 29.1g respectivly. Weight might be reduced a little more by going easier on the glue.
  • The most effective adhesive for metal rods into the CF tubes is a product known as JB Weld. This is basically a metal epoxy. There is nothing stronger.
  • Sand the joiner wire to remove the paint/coating. Coarse sandpaper works best. Sand it enough to slide easily into the CF tubes. Make the last sanding action around the circumference, instead of down the length, to give the JBWeld something extra to grip.
  • After experimenting with about every way to mount the aileron servos, ended up with one servo per wing half to overcome binding. Even tried a HS-81, but the ailerons wouldn't come back even close to center when the stick was released. Now it comes within a 1/16" of centering... and a touch of opposite aileron is necessary to stop a roll.

    Click on the number below each image for a larger version of the picture (larger number, larger version of the picture)


    1600 / 1024 / 640 - Cooling holes added.
    1600 / 1024 / 640 -
    1600 / 1024 / 640 - Modified tailcone for cooling.

    1600 / 1024 / 640 - Drilled square hole out to 9/64".
    1600 / 1024 / 640 - Central Hobbies 5/32" CF tubes
    1600 / 1024 / 640 - Will epoxy tubes to spar.

    1600 / 1024 / 640 - Extends joiner wire much farther.
    1600 / 1024 / 640 - Kevlar tissue epoxied to fuse.
    1600 / 1024 / 640 - Adds strength where joiner sits.

    1600 / 1024 / 640 - Joiner sanded, leaving grooves.
    1600 / 1024 / 640 - CF Tube epoxied into spar.
    1600 / 1024 / 640 - Gorilla Glue foams to enclose.

    1600 / 1024 / 640 - Wing joint sanded and poked.
    1600 / 1024 / 640 - Glue in fuse crossbars.
    1600 / 1024 / 640 - Gorilla glue here too.

    1600 / 1024 / 640 - Wing pinned to fuse side for gluing.
    1600 / 1024 / 640 - Both wings attached, allow to set.
    1600 / 1024 / 640 - Then came back with Gorilla Glue.

    1600 / 1024 / 640 - Glue set, ready for fillets.
    1600 / 1024 / 640 - Fillets attached.
    1600 / 1024 / 640 -

    1600 / 1024 / 640 - Kevlar tissue.
    1600 / 1024 / 640 - Layered up around joiner.
    1600 / 1024 / 640 - Attached with epoxy.

    1600 / 1024 / 640 - 08/06/2004 - Aileron servo
    1600 / 1024 / 640 - Tried various aileron methods
    1600 / 1024 / 640 - Dual servos help binding pushrods

    1600 / 1024 / 640 - Motor test fited.
    1600 / 1024 / 640 - Cooling for motor.
    1600 / 1024 / 640 - Test fit exhaust tube.

    1600 / 1024 / 640 - UHU Por foam glue for stab
    1600 / 1024 / 640 - Glue worked ok, but left gaps
    1600 / 1024 / 640 - Other stab half installed.

    1600 / 1024 / 640 - Time to apply decals.
    1600 / 1024 / 640 - Got carried away on purpose...
    1600 / 1024 / 640 - Silver models are hard to see.

    1600 / 1024 / 640 - Visibility higher priority than scale.
    1600 / 1024 / 640 - Elevator servo.
    1600 / 1024 / 640 - This worked out much better.

    1600 / 1024 / 640 - Added Gorilla glue to stab bottom
    1600 / 1024 / 640 - Elevator control is smooth.
    1600 / 1024 / 640 - Install battery tray.

    1600 / 1024 / 640 - Install RX and clean up wiring
    1600 / 1024 / 640 - Mount motor.
    1600 / 1024 / 640 - Temporary battery holder...

    1600 / 1024 / 640 - will do something lighter.
    1600 / 1024 / 640 - 2200mah balanced with no lead
    1600 / 1024 / 640 - Holds the battery securely.

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    ©COPYRIGHT NOTICE: You are granted permission to view these images while accessing these web pages, but I retain all rights to the images and they may not be used for any other purpose without my permission.

    Copyright 2004 - Andy Steere

    Last modified on 08/23/2004

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