B25 Manual

 


If you have not worked with foam before, it is strongly recommended that you read the How To section first.
Do not discard any foam pieces that came with the kit, until after the construction is finished.

The Wowplanes B25 is a builder's kit. We assume that the builder has at least an intermediate skill level in building RC flying models and has built kits and ARFs before in balsa if not foam. The objective of this manual is to illustrate the features and construction techniques that are unique to this model.

It is not the intent of this manual to show the basics such as installation of motors, radio, servos, linkages, etc. which are common to all models.

Wowplanes kits lend themselves to finishing the model in multiple ways. The model may be left as bare foam and painted with foam safe paint, or covered with low temperature heat shrink covering, or fiber glassed and painted, or sheeted with balsa and painted, etc.

Before you start building it is recommended that you decide what option you plan to pursue. Depending on the finishing option, you may have to alter the sequence of construction outlined below. e.g. if you plan to sheet the model with balsa, it would be easier to build and sheet the individual sub-assemblies before assembling the whole plane.


Contents
1.0 The Fuselage
2.0 The Wing
3.0 Attach the Wing and Fuselage
4.0 The Tail
5.0 Attach the Tail and Fuselage.
6.0 Motor Wiring
7.0 Center of gravity.
 


1.0 The Fuselage
The fuselage comes in 4 pieces. The front section, the tail cone, the wing seat cover, and the inner core.

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  • Glue the seams that run along the underside of the front section and the tail cone.
  • Insert 1/16" balsa at the leading edge of the stabilizer cutout, glue in place, trim and sand flush.
  • Glue 1/8" x 1" x 2 1/2" plywood in the channel on the underside the fuselage.

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  • Glue 1/8" x 1" x 1" plywood to the underside of the fuselage where the nose gear will be located.
  • Measure the distance from the front end of the fuselage and transfer this to the upper side.
  • Glue another 1/8" x 1" x1" plywood to make a foam sandwich.
  • Drill a 1/8" hole all the way through from the underside.
  • Glue the tail cone to the fuselage front section.
  • Using the inner core of the fuselage front section, draw lines as shown above. Use a sharp utility knife to cut along these lines.

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  • Glue the cut piece as shown to form the cockpit floor.
  • Trim the plastic parts for the nose section. Position in place and trace the outline on the foam.
  • Use a sharp utility knife to cut the excess foam. Shave thin slices of the foam until the desired shape is achieved.
  • If you use a sawing action and hold the knife edge almost flat against the foam, it is possible to shave tissue thin slices off, requiring minimal sanding. Finish with 300 grit sandpaper.

Nose Gear
Nose gear is located 4" back from the from edge of the fuselage.

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Enlarge the picture above to see details of how the nose gear is installed.

Battery Hatch
 

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Here is an idea where the battery hatch can be placed. You may choose to do it differently. This hatch is held in place by a tongue and rare earth magnets.

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The fuselage is done.


2.0 The Wing
The wing comes in 11 parts. The ailerons and servo plugs are taped in place. Remove the tapes.


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  • Line the aileron cut outs with 1/16" balsa. The liner on the servo side must extend all the way into the servo cutout.
  • Sheet both sides of the ailerons with 1/32" balsa using M77 spray glue and trim.
  • Sand the hinge face at a 15 to 20 degree angle as shown in the picture above.
  • Cap the hinge face of the aileron with 1/16" balsa.
  • Trim the aileron allowing 1/16" gap at each end when fitted.
  • Cap the ends with 1/32" balsa and epoxy, leaving a 1.32" gap at each end.
  • Do not attach the ailerons as yet. They can be hinged with tape or strip of heat shrink covering.
  • Draw a 2" radius circle at each wing tip. Trim and round the tips.

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  • Center the HS55 servo and insert it into the servo cutout. Route the servo cable along the spar channel.
  • Turn the wing over and glue the servo plug into the cutout, then slice the protruding portion of the plug flush with the wing.
  • Repeat for other wing.
  • Join the 5 wing sections end-to-end. There is no need to sand the dihedral angles, they are already built into the appropriate sections. Just glue each section to the next as a butt joint and the correct dihedral angles will come out automatically.

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  • Using 1/8" piano wire, make the main U/C to the dimensions shown in the picture.
  • Cut two U/C mounts from plywood 1/4" x 1.5" x 3".
  • Drill a 1/8" hole along the center line, 1/2" from the shorter side.
  • Attached the U/C wire with straps, and bend then in to compensate for the dihedral angle of the wing.
  • Using the plywood as a template, trace out the location of the mount. Lined up behind the spar slot and 2.5" outboard from the fuselage.
  • Make a 1/4" recess in the foam. Test for fit but do not glue yet.

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  • Cut two plywood spars from 1/8" plywood as shown in the picture above.

2.1 Nacelles

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  • Trim and sand the rear ends of the nacelles to look as shown. The front ends should not require any trimming or sanding.
  • Use the nacelles as templates to trace and cut the firewalls from 1/8" plywood.
  • Cut a slot as shown and dig out some foam to make compartments for the ESCs.
  • At this point you have to decide how you are going to mount the motors. If you plan to use the radial mount method for outrunners, mark and drill the four holes, install blind nuts from behind the plywood, and then glue the firewall to the nacelle face. Cover the blind nuts with tape first to prevent glue from fouling the threads. If you plan to build a motor mount box, then the firewalls can be glued first.
  • Bore a hole from the ESC compartment to the back and sloped down slightly and let it exit the Nacelle on its underside. This is for air flow to keep the ESC ventilated.
  • Bore a second hole up towards the wing to come out near the spar. This is to route the battery and throttle cables.

Click picture to enlarge

  • Place the U/C in position, and slide the Nacelle in from the wing tip end.
  • Mark the place where it hits the U/C wire and cut a slot in the nacelle.
  • Cut a channel along the spar to bury the battery and throttle cables. This can be capped with strip balsa later.

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  • The Nacelles outboard edge should be placed 1/2" inboard from the joint between the outer wing panel and the rest of the wing.
  • Make a mark at the wing tip at the spar slot such that it is visible from the top.
  • Make a second mark at the center line of the nacelle rear end.
  • Make a third mark at the center line of the front face. There is wire burn mark provided in the foam for this.
  • Make the dimensions X=X and Y=Y as shown in the picture.
  • The Nacelles are now perpendicular to the wing and parallel to each other.
  • Test by placing a straight edge along ten faces of the two nacelles. The straight edge should rest flat against the faces.
  • Make alignment marks on the nacelles and the wings before removing everything.
  • Using 30 minute epoxy, first glue the spars, then the U/C mounts, then the nacelles.

The wing is done.


3.0 Attach the wing and fuselage

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  • Cut a piece of plywood 1/8" x 2" x 1" and center it on the top surface of the wing directly above the channel provided in the wing bottom. Sand a flat spot and glue it in place.
  • Set the wing in the wing saddle of the fuselage. Make the dimensions X = X.
  • When satisfied, tape the wing in that position and turn the plane over on its back.
  • Drill a 5/32" hole at the center of the plywood that is already glued to the bottom of the fuselage. Drill as vertically as possible and all the way through to the plywood piece in the wing.
  • Remove the wing and install a size 6-32 blind nut on the plywood piece on the wing.
  • Mount the wing to the fuselage with a size 6-32 screw from the bottom.

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  • Cut 2 plywood pieces 1/8" x 1" x 1" and 1 piece 1/8" x 2" x 1".
  • Glue one 1" x 1" piece inside the tail cone as shown.
  • Glue the other 1" x 1" piece inside the wing seat cover as shown.
  • Glue the 2" x 1" piece over the 1" x 1" piece that you just glued allowing it to hang out halfway.
  • Set the wing cover in place, and glue it to the wing. Note the use of wax paper to prevent the wing from becoming glued to the fuselage.

4.0 The Tail

The tail is made from 5 pre-formed foam parts.

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  • Glue the 3 horizontal stabilizer pieces end-to-end.
  • Fill the wire cut in the vertical stabilizers by gluing pieces of 1/16" balsa.
  • Round the corners of the vertical stabilizers to shape. Tape then together and do both at the same time to get identical shapes.
  • Dry fit the vertical stabilizers to the horizontal stabilizer ends. Sand in a taper in the leading end of the slots to mate with the taper in the horizontal stabilizer.
  • Cut the elevators according to the dimensions shown in the picture.

5.0 Attach the tail and fuselage

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  • Dry fit the horizontal stabilizer in place and make the dimensions X=X and Y=Y
  • Sight from the rear of the model to see if the elevator is level with the wings. Use balsa shims if necessary.
  • When satisfied, mark the position of the elevator, remove it and using 30 minute epoxy, glue it back in place.
  • Check the X, Y, and level and let the glue cure.

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  • Slide the vertical stabilizers onto the ends of the horizontal stabilizer.
  • Sighting from the rear of the plane make the dimensions X=X and Y=Y
  • The vertical stabs are now aligned parallel to the fuselage mid-line and to each other.
  • Mark their positions and glue them in place with 30 minute epoxy.
  • Cut of the horizontal stab ends to be flush with the vertical stab surface.
  • If you like to fly rudder, these can be added by cutting the vertical stabs just behind the horizontal stab.
  • Cut a piece from the scrap foam that came with the kit, glue it to the end of the tail and sand it into a tail cone end shape.

6.0 Motor Wiring


7.0 Center of gravity

  • The Center of Gravity is located 2.75" back from the leading edge of the wing measured at the root where the wing enters the fuselage.
  • The model should be balance at this point after all the equipment and finish has been applied. This must be the final step. Use the battery location to achieve the balance.

HAPPY LANDING !!