Winter Project- Graupner Kadett

[Michael]

@Frank v B clamps are on the right side only?!? 
I am puzzled...   

Probably already glued and dried on the left side.

Right, Frank?

[Frank v B]

Guy,

re: right side only clamps.

The plywood dihedral brace was glued to the left wing first until the glue cured.  Then glue was applied to the right wing and it was clamped and picture taken.  I always try to glue things one step at a time so it is easier to be accurate.
The other reason for doing this way- I only had the dihedral angle from the plans.  I had no way of knowing how high to block up each wingtip as is the normal practice.  This way I glued the dihedral brace to one wing half, then cut the main spars to the required angle on the left wing and make the proper angle in the leading, trailing edge and spars on the right wing.

Frank

[Frank v B]

The plans did not have centre wing sheeting.  I like it because it adds strength and it spreads the loads of the rubber bands evenly over a larger surface.  Added it to the top only. 
I wonder the name of the balsa supplier?    Notice the price stamp... $.96 for a 1/16" x 3" x 36" sheet.  That makes it period balsa for this plane.  It was started in 1974-ish.

Frank

[Frank v B]

How about another hatch.  This is a curved one on the top between the windshield and the motor.

Steps:
1) made a brace out of straight pieces of wood.  Glued two cross braces in place out of 1/4" balsa.  Objective- all parts of the hatch need to be at or above the curve of the fuse sides. Photo 82
2) after it dried, I sanded the curve into it.  10 passes of a sanding bar.  photo 85
3) take the pins out and pop it loose.  photo 86.
4) add 1/16" balsa to the curved surface and more death by 100 clamps.  Notice the cross grain on the balsa sheet so it curves easily.
5) sand the balsa sheet flush with the side.  Still have to do it once it dries (after lunch!)

Frank

[Frank v B]

The front top hatch (cont'd)

- sanded it flush on the sides.  When I installed it for the first time, the font end hit the bell of the motor.  Needed a circular cut-out.  Drew the circle around a Toonie. Photo 88
- test fit the hatch and.... it fit!  Photo 89
- Had to fit cleats at the proper angle and proper height to keep it flush with the curve of the fuse.  Cut two rails from strip balsa and installed them higher than their final position then pushed the hatch down.  It pushed the two rails down at the proper angle and proper height instantly.  Carefully removed the hatch (pushed it up with a pencil through the bottom hatch).  Photo 90
- clamped the rails in place so the glue could cure.  Photo 92  The finished hatch is resting on top of the clamps.

Frank

[Frank v B]

How to fibreglass a wing centre section.

This entire section took less than 5 minutes...because I used 5 minutes epoxy..... and took the photos all before it hardened.
The reason for glassing the centre portion of the wing is to wrap it around the joints at the leading and trailing edge.

Tools:
- Application tool- I cut a piece of foam, fold it double and tape it.  The folding is so there are no sharp corners to snag the cloth. I use it in a dabbing motion, not a brushing motion. Photo 93
- Strips of waxed paper.  This is put over top of the wet glass to allow me to squeeze the glass smooth with my fingers.  It also flattens any sharp edges and neatly transitions the glass to the raw balsa at the edges.  When the epoxy has cured and the waxed paper is removed it will be smooth as glass.  No sanding required. Photo 94.
- at least two pieces of masking tape at least double the width of the chord.  This tape will be wrapped around the wing to hold the waxed paper in place.

Step 1- dab the 5 minute epoxy over the area to be glassed.  I did it about 1/2" wider than the width of the cloth
Step 2- lay the cloth over the wet epoxy Photo 95
Step 3- dip the foam tool into the epoxy and dab all the glass down until the white of the cloth becomes "wet" with epoxy.
Step 4- lay the waxed paper strips over the area one side at a time.  Rub it until the glass surface is smooth. Apply one strip of masking tape all the way around to hold the waxed paper in place. Photos 97, 98.
Step 5- do the second half the same way.

[Frank v B]

Getting there.  It looks like an airplane.

F.

[Frank v B]

Covering.

Will start this today since I looked in the mirror and gave all my employees the day off.  My car is absolutely buried in snow.   Will pull out the snow blower later.

I will post everything concerning the covering of this model as a separate topic so members can refer to it when they are doing their projects.  Here is the link https://temac.ca/smf/index.php?topic=8213.0
Mark Satin is building one so here's hoping this will help him get to the finish line.

Frank

photo 1- my car after 30 minutes of digging
photo 2- "Frank, please set the table for lunch"

[Frank v B]

Covering is finished.  Final assembly is next.


F.

[Frank v B]

Steps in the final assembly.

Note: I cover the tail feathers first as separate pieces and then assemble them once covered.  When the stab is glued to the fuse, it has to be square.  Also the covering needs to be cut away from the bottom of the stab and the top of the fuse.

How to cut away the wedge-shaped covering from the bottom of the stab:
step 1) Using the bottom of the stab, find the middle of the stab by measuring the midway point of the stab/elevator hinge line and push a pin through it...right through the top as well.  Photo 844
step 2- take a plastic right angle from your child's geometry set, flex the elevator to hold full "down" elevator, push the triangle against the pin and the hinge line and draw a line.  This will be absolutely square to the hinge line and will be the center line. (black line) Photo 845 (angle has been moved away to show the black line).
step 3- hold the stab on the fuse so the pin hole is in the middle of the back end of the fuselage. Slide the assembly back about 1/4" and run a knife along the sides of the fuselage to mark the bottom of the stabilizer covering.  In photo 849, the knife point shows the permanent place of the leading edge.  The black magic marker line is how much I slid it back.
step 4- cut the covering away on the score line. photos 847 and 848.  Because you moved the stab back 1/4" when marking it, when you glue it in its proper place, the covering's edge will be hidden by the fuselage.  No bare wood spots will show.
step 5- lining up the stab with the wing.  The wing always gets in the way.  I put a skewer into the wing position and hold it in place with two rubber bands.  The stab will be lined up with this skewer when gluing it in place.  Photo 850

F.

[Frank v B]

A way to attach the stabilizer straight and level.  This is just one way to do it.

Step 1- put a pin in the center of the stab at the hinge line (trailing edge of the stab), put a pin in the center of the leading edge and one in the centre of the fuselage top just at the trailing edge of the wing.  When all 3 pins are lined up exactly, the stab will be square to the fuselage.  The pin holes in the center of the stab were arrived at in the previous post (with the triangle).  Push the trailing edge pin through the stab and into the center of the back end of the fuselage.  See photon 852.  I have skewed the stab to prove it is hinging on the trailing edge pin.
Step 2- add glue to the bottom of the stab and the top of the back end of the fuselage.  I used 5 minute epoxy...what else! photo 853
Step 3- Push the trailing edge pin into the back of the fuselage and get it reasonably straight.
Step 4- lay your metal ruler so it touches all 3 pins.  When they are lined up, push the leading edge pin into the fuselage.  The stab is now square to the fuselage. Photo 854
Step 5- line it up with the wing (the skewer).  The first photo (855) shows the stab was down on the starboard side (camera left).  I pushed a round toothpick into the left side (camera left) to raise it slightly.  The more you push it in, the greater the gap.  Photo 856 shows it is straight.  Let it dry.  Photo 857 shows the placing of the toothpick.  Break it off when the glue is dry.

The total time for this, including taking the photos, was less than the time the 5 minute epoxy needed to dry.

The skewer method works best with wings with a lot of dihedral like this one.  With a straight wing (no dihedral) I use the wing in place to line up the stab.
The traditional way to get a stab square is to measure from the stab tip to the middle of the fuselage behind the wing but when the stab is pinned in place it flops around.  My shop is small (only 6 feet wide) so the 3 pin, ruler and skewer method is easier in tight spaces.

F.

[Frank v B]

Last step- attaching the fin and rudder...straight.

I used the same 3 pin holes (TE of stab, LE of stab, Middle of the top behind the wing) to line up the ruler and draw the cut lines.

Cut the covering away on the fuselage top (photo 858) and the bottom of the fin where the glue is going to be applied.
Add glue, use two pins to hold the fin to the fuselage.  Then to make sure it is vertical, I taped my special triangle to the fin and the stab.
It is a plastic triangle with the right angle cut away so it does not touch the glue and become stuck.  The corner is also cut away since some models have tri-stock braces to strengthen the joint.

Let cure... and celebrate because the model is now finished.

F

[Frank v B]

Done. 

You'da thunk I could have taken sharper photos. 
I am a model builder, not a photographer.


Frank

[Frank v B]

Roger at John's Hobbies accepts the model on behalf of Randy who started building this model in 1974.  Randy was off the day I dropped by the store.

Note the 72 meg radio in keeping with the vintage theme. The radio is  about 35 years old.  Modern relative to the model's 1956 design date. It was designed as a free flight model.
The motor was from one of Malcolm Cullen's donations.

Randy will be invited to TEMAC this spring to see it fly.

Frank