34" span Chipmunk- House of Balsa- build.

[Frank v B]

Solarfilm hinges.*  How to make them.

This is a hinging technique I use on smaller planes (less than .10 size) and it works wonderfully well.  Not good for high speed yank-and-bank planes but good for reasonable speed models... even though my 150 km/hr Nooner uses this on the elevator and ailerons....no problem.
Description: Covering is done on one side.  When the surface is covered on the other side, the two glued sections at the hinge will fuse and become the hinge.

Advantages
- for thinner stabs/rudders where it is hard to cut a slit in the balsa for a CA hinge.
- gapless.  Improved turning.  There is no gap for air to leak from the high pressure side to the low pressure side.
- no cost, no out-of-stock situation.

Steps
1) Cut/sand a bevel into one of the surfaces.  Usually the elevator.  The angle allows the deflection.
2) Cheat! I place 2 small strips of celluloid tape to hold the surfaces together.  See photo 14.
3) Cover the bottom of the stab first while the elevator is folded double (180 degrees full "up"). See photo 18. Attach the stab covering then work up the hinge area and then the bottom of the elevator while folded 180 degrees.  Photo 19.
4) do all the detail work (edges, tips, etc.)
5) Do the top sheet.  I did it in 2 halves.  Attach to the stab first, then while holding it in maximum deflection, attach the covering to the elevator.  Make sure to heat the hinge line so the covering will fuse glue side to glue side (top to bottom)
6) Do all the detail work.

Photo 22- full "up" deflection.
Photo 24- full "down" elevator.

Frank

* the name comes from Solarfilm which is/was the brand name of the film of choice in the UK.  Their version of Monokote.

[Frank v B]

Faking it.

Here is how to not waste time trying to make something symmetrical.  The black nose of the fuse needs to look symmetrical.

Step 1- cut a piece long enough to cover the area.  Make sure it has a straight edge.
Step 2- follow the lines of the black around one side of the fuselage until it looks good.
Step 3- cut slits across the nose so it can overlap to form a curved surface across the top of the fuse. When attaching the covering, start at the back and work forward.  This way the overlaps are down wind.
Step 4- Cut the opposite side. It does not need to be accurate. Note inaccuracies at the right side of 26 (left side of the fuse).
Step 5- Cut a strip with at least 1 straight edge and make the curve to cover the ragged edge. Photo 27

Enough to meet the 50/50 rule. Finished photo is 29

Frank

[Frank v B]

Final Details:

cover the nose hatches.
1) Fresh air!- drilled a hole in the front with a progressively larger drill bit.  Final opening with a Dremel sanding drum both from the front and the inside.
2) covering the two hatches with film.
3) faking the inside with Dollarama paint.  One coat worked fine. Photo 37

Frank

[Frank v B]

Mid-course correction

I did not like the way the turtle deck (curved fuselage top behind the canopy) was designed so I built ahead and am now forced to deal with it.

(Wrong) Original Approach- the plastic canopy was one piece all the way from the firewall back to the rudder fin.  The fin was to be glued on top of the flimsy plastic canopy as shown in the first picture.  I know the pilot who will be flying this plane.  It will not last...especially with 3 times the power for which it was originally designed.

New Approach- build the turtle deck out of balsa and cut the canopy apart as if it were a normal canopy.

The second photo shows the fin structure with balsa attached to both sides so the covering will stick to it.
The third photo is the fin structure held in place on the fuse.

Will have to fake the curve someway or somehow.  Stay tuned.

Frank

[GuyOReilly]

@Frank v B , concerning the "Will have to fake the curve someway or somehow."
How about 1/16 sticks to fake the curve.
Alternatively, 1/32 sheeting.
Other option, foam block shaved to shape.
I am running out of ideas...
Guy

[Frank v B]

Guy,

My options are still open..except for the foam* option..... "Don't make a decision until you have to".

Have started to build the ribs.  See photo.  Note that I build them without shape, let the glue dry, then shape them.

My first option is to use sticks because this is a compound curve (up/down, sideways). Will probably put covering film over the structure.
Sheeting can only handle one curve.

Frank

* foam, when sanded, has a habit of sticking to clothes, showing up on living room/dining room floors...leading to the wrong conclusion...."get rid of the model airplanes" as opposed to "stop using foam".  I can't win.

[msatin]

How about BBQ skewers or dowels?
Also - Why did you choose to cover most of the plane before building this section?
I'm finding that in the few kits I've built, that I sometimes don't understand the order the instructions are saying to build in.
I don't always follow those instructions, but understanding different builder's methods will help me make better decisions

[GordPayne]

How about a custom 3D printed turtle deck?  You'd get the shape you want and the infill could be minimal to keep it light. You'd just want it in something like ABS so it doesn't warp in the hot sun. I know plastic is sacrilegious to a true modeled, but it's also a solution😀. Your build is really great Frank!

[Frank v B]

re: questions:

Mark
- How about BBQ skewers or dowels? They tend to be heavy versus balsa.  Balsa is also easier to sand (read as : "easier to sand out errors")

- Why did you choose to cover most of the plane before building this section? Sometimes problem solving issues need to spin around my head for a while.  It is not really out of sequence because the top is covered last in the covering sequence.

Gord
- 3-D printing the back end?- You are coaching someone who uses a flip phone. 

20 minutes later the stringers are in place and drying over dinner.  No foam dust particles.  Will work out fine.

Frank

[GordPayne]

Geoffrey DeHavilland would be proud Frank!

[Frank v B]

Thanks, Gord.

Final assembly:
I always use the following 3 step method to attach the wing, stab, fin/rudder to get perfect alignment without needing to be an accurate builder.

Step 1 - attach the wing properly with screws and leading edge dowels.  Try to get it as true to the fuse as you can...by eye.  Let everything dry/cure
Step 2 - attach the stab/elevator so it matches the wing when looking down the nose (the airplane's, not yours!) with one eye.  I never measure from a desk-top to the wing/stab.  Let everything dry/cure.
Step 3 - Attach the fin/rudder assembly and tape a triangle to the stab/fin while the glue sets.  Photo 75.  Let it cure.

Note in the fin attachment I used toothpicks to act as a bit of a key into the stab. Photo 74

As long as the wing/stab/fin are in alignment, it doesn't really matter whether the fuse is straight.  This way there is no coupling* in any aileron/elevator/rudder movement....beyond the flaws in the airplane's design.

Frank

* "Coupling" is when surfaces are not parallel or square to each other.  A movement in one (pitch, roll, yaw) will cause a movement in another.  Example- A misaligned stab will cause some roll when deflected.

[Frank v B]

First photos... assembled!

Still have to do some details
- clean up covering
- attach pushrods
- make and install tail wheel
- install the electronics permanently

Cute as a button...with a snarly 300 watts* going through it! 

Frank

* Still have to weigh it with the electronics/battery in place.

Note: 300 watts is exactly .4 horsepower!  Yes, a little overkill.... because I can.

[msatin]

She looks beautiful Frank!

[Frank v B]

Thanks Mark.

Final details done:
- wigglers are attached to servos (rudder, aileron, elevator)
- faked a tail wheel
- installed the ESC (35 amp)
- installed the battery tray and Velcro
- installed the receiver

Interesting: the plane balanced on the CG without the battery.  Had to put the battery as close to the CG as possible.  Not in the forward hatch.

Done!

Frank

[Frank v B]

Final stats.

Plane weight 24 oz ready to fly.
E-Flite inrunner 6- Max power 400 watts
Watts per pound- 267

Original objective from my first post: "power- TBD but it will be "enough plus 25%". "
"Missed it by that much" on the good side.  Actual result: "Enough plus 50%!!

Conclusion- it will fly...vertically!!
May have to use the throttle.

Frank

https://www.youtube.com/watch?v=oPwrodxghrw