Mountain Models SwitchBack Senior Assembly Instructions Manual Download Page 31

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Section 11: Installing the Motor

We recommend a brushless motor rated for around 200 to 300 watts. The prototypes flew

outstanding on the Scorpion 3008 and 3S at around 250 watts.

Installing the Motor

You will want to glue the mounts together with epoxy, rather than CA. Epoxy can handle the

vibration of a slightly out of balance propeller better than CA can.

Assemble the motor mount as shown in the photos. Make sure the parts are seated properly

to ensure the thrust angles are correct. All the parts are 1/8” Lt. Ply except for the 1/16”

plywood front doubler. The front parts have holes for the Scorpion motors. There are
additional ones marked with an X to help alignment if you are using a different brand motor.

Bolt the motor to the mount using the supplied 4-40 x 3/8” screws.

Bolt the motor mount to the firewall using 4-40 x 3/8” screws and the #4 washers.

Summary of Contents for SwitchBack Senior

Page 1: ...SwitchBack Senior SwitchBack Senior Specifications Wingspan 55 4 in Length 41 in Wing Area 597 sq in Weight Ready to Fly 34 to 37 oz Wing Loading 8 2 to 8 9 oz sq ft Version 1 05 March 3 2008 ...

Page 2: ...el than the original Sincerely Brian Eberwein sales mountainmodels com WARRANTY Mountain Models guarantees this kit to be from defects in material and workmanship for the original purchaser Since we have no control over the assembly of the final model we accept NO liability for any damage or harm caused by the final product resulting from the user By building this kit you accept sole responsibilit...

Page 3: ...x Elevator 1 ea HS 85 Servo Rudder 2 ea 6 Servo extensions 1 ea Y Servo Connector if using 1 channel for ailerons 1 ea Mini Receiver 6 channel for using 2 aileron servos without Y Connector 1 ea Scorpion 3008 32 Brushless Outrunner or 200 300 watt equivalent 1 ea 3S 2000 LiPo Battery or higher capacity 1 ea 35A Electronic Speed Control Tools You Will Need Smooth and FLAT work surface Plastic wrap ...

Page 4: ...od Housings 2 ea 1 16 x 24 Wire 2 ea 1 16 x 12 Wire 1 ea 0 047 x 9 Wire 2 ea 0 060 x 24 Carbon Fiber Rod 2 ea 1 8 Pre Bent Landing Gear Wire Plastic Vac Formed Canopy and Cowling Parts Bag o 8 ea EZ Hinges o 4 ea EZ Servo Connectors o 8 ea 4 40 T Nuts o 8 ea 4 40 x 3 8 Machine Screws o 2 ea 10 32 T Nuts o 2 ea 10 32 Nylon Bolts o 2 ea 2 DuBro Wheels o 1 ea 1 DuBro Tail Wheel o 2 ea 1 8 Wheel Colla...

Page 5: ...ected areas Removing the char will not increase the strength but will make it look better Assembly Instructions Experienced builders may notice that this building order goes against the normal building conventions We have found that fewer pieces get mangled this way since you are building the stronger pieces first For example the tail feathers are at the end of the build process instead of the beg...

Page 6: ...ch as shown below It is a fairly tight fit so work it back into position a little at a time Do NOT glue them together yet 3 Press the crutch from step 2 and the fuselage wing mount into the 1 8 balsa former as shown below Make sure the blind nuts are facing as they are in the image It s easiest to lay the former on your table and press the crutch into the slots Do NOT glue yet 4 Press the crutch o...

Page 7: ... and not upside down Also make sure that the parts are flush on one side Secure these parts with thin CA 6 Assemble the rear parts to the front 1 8 fuselage parts as shown below Place only a couple drops of thin CA at the joints Between the front and rear fuselage parts 7 Press the 3 32 balsa formers into the 1 16 balsa bottom as shown below The lasered side of the bottom goes up and the lasered s...

Page 8: ...ou should end up with an angle rather than a curve at the joint with the 1 8 balsa former Be careful to keep your fingers as far away from the glue as possible otherwise you might become a part of the model permanently If you do get stuck remove yourself as carefully as possible trying to avoid taking any of the wood with you Once separated remove the CA glue from your fingers using nail polish re...

Page 9: ...he fuse front sides 13 Press the 1 16 balsa sides in place with the lasered side to the inside of the fuselage You can use thick CA to glue these sides on or you can use thin CA after they are on making sure they are fully pressed into place Weights help make sure the sides are fully pressed into place as shown below Steel plate cut to about 4 squares makes GREAT weights for building They are usef...

Page 10: ...de Secure the sides with thin CA 15 Install the 3 16 rear spine into the formers as shown below Make sure it is fully seated and secure it with thin CA 16 Press the 1 8 plywood landing gear supports into place as shown below The lasered sides should face to the inside of the fuselage Clamp them or otherwise make sure they are fully pressed into place and against the sides while the glue is drying ...

Page 11: ...s shown below ONCE AGAIN making sure that the holes for the landing gear wire line up 18 Install the 1 16 balsa rear deck as shown below Make sure that it lines up with the front of the 3 16 spine The deck sits on top of the inside 1 8 longerons and inside of the 1 16 balsa sides You ll have to lightly bend the front of the 1 16 sheet to sit in the forward area 19 Glue the MAGNETIC washers to the ...

Page 12: ...es Sand the top front of the fuselage sides to follow the curve of the front 2 formers Line up the 1 16 top front balsa sheet so there is the same amount of material hanging off on each side Lift up one side and tack down with thick CA Then glue the other side with thick CA as well Sand the sides of the front top sheet to be flush with the fuselage sides ...

Page 13: ...ard part of the 1 8 balsa part just aft of the rear former so it is flush with the fuselage sides as shown in the top right image 25 Sand the front and rear bottom corners of the fuselage round the top rear center and round the top of the fuselage sides where they meet the top rear deck Test fit your canopy and cowling to make sure you have rounded the corners enough for the parts to fit properly ...

Page 14: ... had the front fuselage sides on it They have 1 slot at the bottom rear of the ribs Do NOT glue them yet 3 Insert the 1 8 plywood center front part into the ribs Do this a little at a time It will be necessary to spread the full ribs out of the way while you slide it into place as shown in the above right image After it s fully seated into the ribs press the full ribs onto it Do NOT glue it yet 4 ...

Page 15: ...ribs to get the tabs on the part into the ribs 7 Install the 1 8 Lt Ply rear center section as shown below Make sure the center section is square and secure the parts with thin CA Glue the 2 1 8 balsa parts into place using thick CA sh shown below making sure that the bolt holes are lined up 8 Press the 3 32 servo mounting area ribs into place These ribs have slots in the bottom to accept the serv...

Page 16: ...o the ribs along the wing then start at the center working out pressing in further Repeat until it is fully pressed into place 11 Press the 3 32 balsa T E supports into the 1 8 trailing edge as shown below The 3 32 parts were next to the leading edges used in step 10 LOOK AT THE PARTS One end has an angle on the 1 8 parts which goes toward the center section of the wing Set them next to each other...

Page 17: ...little bit at a time until all the ribs are fully seated and it is plugged into the center 1 8 rib 13 Press the outboard 1 8 balsa ribs into place These are on the sheet with the canopy frame 14 Slide the 1 16 plywood spars into place as shown in the images below Note that the top and bottom spars are different shapes Make sure they are flush with the spar and glue them in place with thin CA after...

Page 18: ... 16 leading edge parts onto the wing as shown below Make sure they are all fully pressed in place and lightly tack with thin CA 17 MAKE SURE that the wing panels are straight and all parts are fully seated and lined up After you are SURE secure all parts with CA double checking as you go to make sure the parts are still seated before you add the glue to an area 18 Install the top center wing sheet...

Page 19: ...sheeting is fully pressed onto the tabs on the ribs and sits flush with the 3 16 leading edge part 20 Weigh down the right side of the wing and make sure it is straight and flat Test fit the top wing sheeting Start by gluing down the front of the sheeting with thin CA with the back sitting up slightly as shown in the image below 21 You can glue the back of the sheeting with thick CA if you re fast...

Page 20: ...rvo mounts in the wing as shown below using thick CA Glue in the 1 8 balsa servo mount doublers on the inside of the wing on top of the plywood mounts with thick CA 25 Sand the leading edge to finish the airfoil shape DO NOT NICK THE plywood wing mounts in the center section Wrapping these with tape while sanding is a good idea A good approximation on where to sand is by starting out sanding tange...

Page 21: ... in the center of the wing so you can fish the servo wire out the wing after it is covered Tape the string in place just to the inside so you can get to it after cutting out the holes in the covering Section 3 Assembling the Ailerons 1 Build both ailerons at the same time to make sure you make a LEFT and RIGHT aileron 2 Press the 3 32 aileron ribs into the 1 16 aileron sheet as shown below The cen...

Page 22: ... aileron leading edge in place on the aileron as shown Make sure it is FLAT and STRAIGHT weighing it down while it is glued 6 Trim the Carbon Fiber rods to length and glue them to the trailing edge of the ailerons with thick CA Keep your aileron flat while you are doing this or you ll end up with a permanent warp 7 When done you should have a LEFT and RIGHT aileron as shown ...

Page 23: ...23 Section 4 Assembling the Stabilizer Elevator Vertical Fin and Rudder 8 Press the parts together as shown After the parts are assembled and flat secure each joint with a drop or 2 of thin CA ...

Page 24: ...zontal stab for the hinge line 13 Sand round the outside edges of the vertical rudder stab and elevators It looks a lot better round instead of leaving it squared off Shaping the Tail Wheel Wire and Attaching it to the Rudder Needle nose pliers work pretty well to shape the wire 1 Bend the 0 047 wire as shown below This drawing is to scale 2 Cut one of the CA hinges in half lengthwise Wrap one pie...

Page 25: ...s braces in the canopy base Press the 4 magnets into the holes making sure they are flush on the lasered side of the canopy base Glue in the magnets with thin and thick CA 2 Trim the canopy plastic so you have about 1 8 to 3 16 overhand on the front back and sides of the fuselage 3 Set the canopy frame in the fuselage and the canopy over it You ll need to slightly sand the front sides of the frame...

Page 26: ...red into the thickness of the wood The rudder gets 3 hinges one down from the top one just above the rudder horn slot and one way between the other 2 The elevators stab get 2 hinges per side one about in from the tips and one 1bout away from the dowel The ailerons get 3 hinges each one about 1 in from each end and one in the middle For the aileron slits cut them in the ailerons first and then lay ...

Page 27: ...ear of the stabilizer lines up with the rear of the fuselage and that it s perpendicular to the elevator Hold in place until the CA sets See image at top of page Position the three hinges into their slots on the rudder Slide the tail wheel wire though the hole in 1 16 plywood part on the back bottom of the fuselage Maneuver the rudder so that one by one the hinges can be lined up and slid into the...

Page 28: ...s and Control Rods 1 The tail feather servo holes in the plywood crutch are sized for HS81 size servos 2 Place the servos in the holes with the control horns towards the front of the fuselage Screw the servos into place and then remove the screws and servos Flow some thin CA into where the servo screws screw holes to strengthen the wood creating tough threads Allow the glue to dry completely and t...

Page 29: ...ctor with the screw 8 Trim off extra wire about 1 4 on the other side of the EZ connector 9 Thread the 24 1 16 wire through the pushrod housings with the Z Bend in the front fuselage area 10 Install an EZ Connector on the plywood elevator and rudder control horns 11 Slide the control wire through the EZ connector on the plywood control horn Place the Z Bend through the servo control horn and place...

Page 30: ...ough the bottom and then back out on the other side Pull them tight and trim off the extra as shown in the image below Slide the wheels onto the main gear and secure them with the Wheel Collars and set screws Slide the tail wheel onto the tail wire and secure it with some drops of thick CA on the end of the wire BE CAREFUL not to get CA in the wheel itself ...

Page 31: ... propeller better than CA can 2 Assemble the motor mount as shown in the photos Make sure the parts are seated properly to ensure the thrust angles are correct All the parts are 1 8 Lt Ply except for the 1 16 plywood front doubler The front parts have holes for the Scorpion motors There are additional ones marked with an X to help alignment if you are using a different brand motor 3 Bolt the motor...

Page 32: ... front to allow air to flow through cooling the motor ESC and battery 3 Place the cowling on the front fuselage and use the 4 2 screws to fasten the cowling to the cowling mounts Attaching the Wing Place the wing into the fuselage and secure it in place with the 10 32 nylon bolts Attaching the battery 1 The battery mount is the front section of the plywood crutch 2 Determine approximately where th...

Page 33: ... how the airplane recovers from a nose up or nose down condition pitch stability With the CG too far forward the plane will be quite stable but require a lot of up elevator to fly level This will result in an increased low end speed On the other hand too far back and the plane will be hard to control requiring constant input to keep the plane flying straight and level Start with the CG about 3 5 8...

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