YAK 3

15 June 2015

It has been raining for too many Sundays. I practised a bit of V911 in the morning. If there are a few V911 flyers around, we could have a slalom race around the columns.

At around 2-3pm, the weather was fine, and I contacted Thang to combat. No streamers (ground would have being too wet for crepe paper streamers), just try to ram each other.

 

By the time he got in the car, it started to drizzle. Very soon the rain wiper had to be turned on but we continued. Luckily, once north of the PIE the rain petered out and by the time we parked, it was windy but no rain. We made our way to the tree and the drops started falling and we only had a quick flight before we make off for the car. Due to the windy condition, Thang's BF 109 was momentarily disturbed and crashed. The BF 109 was grounded, the Yak 3 survived and therefore earned a cross.

 

The rain didn't develop it's potential and very soon we were flying again. Yak 3 defended the sky from P-51 until 5.30pm. No ram at all for about 10 flights. Spectators were amazed at the little fighters in such strong wind.

 

On a calm day, we shall try the streamer. Maybe 1m long on 1m long string.

2 June 2015

With Thang's 3 channel mustang. He didn't use the set I passed him.

And occasionally I park the Yak3 into this tree.

 

 

 

 

25 May 2015

Flies ok. Invert, rolls, yawing turns, loops and bunts are untidy.
Wong flew it twice. I knocked Thang's vector kite, mid air from behind 3 times.
I passed one set of the flight components to Thang, hopefully he will do something simple and we can do some formation and combat flying or just race against each other.

22 May 2015

37 gm AUW, hover at 50% throttle.
Added chamfer pieces.
Pushrods of CF rod, 2cm heat shrink sleeves, thin z-end wires.
Control horns from PVC sheet, aileron's with 3mm foam sheet.

 

 

 

 

21 May 2015

Normal stationery tape was used to reinforce the model. A piece was added to the underside of the wing, spanwise.
The geared motor glued to the fuselage with UHU.
The rudder was cut out, with chamfers at the hingeline.
Wing was scored, dihedral bent, then superglued to the fuselage, using the previous 11.5" model's jig.
Horizontal stabiliser and elevators was superglued to the fuselage.
Blenderm tape was applied to port of rudder, then to the fuselage.

I think I shan't do the chamfer reinforcement pieces now. If it is too weak, then I add them.

20 May 2015 (Making a 16" model)

Traced and coloured in canopy complete with pilot.
Paper template placed on foam sheet.
This time, the Stars and exhaust bank (a simple rectangle) is cut out.
I drew lines where I will insert strips of 3mm wide CF strip that Thang gave, I allowed some down thrust from an imaginary fuselage datum line, positive angle of attack for the wing and tail but maintaining decalage.
Paper template glued to foam sheet.
Marker pen to colour.
Foam blanks cut out to external shape.
At the fuselage, I cut out a slot for horizontal stabiliser and elevator and two 3mm wide CF strips are glued in.
Markings are transferred to edges of foam pieces.
Peel off paper template.
Draw in panel lines, etc.
Blenderm hinges and V slots for control surfaces. At this point of time, the rudder is not detached yet, which is the same as the last time.

1. It took me a while longer this time to come to this stage, slightly more than 2 hours at a leisurely pace, I drawn in the CF strips, incidences of the wing and tail and also the landing gear markings at the bottom of the wing. As for the horizontal stabiliser and elevator, they are only line drawn on one side. Line markings are different from the last time because in both instances, they were not based on any actual drawings to begin with. There's a slight natural bend to the foam sheet, so I arrange the components. Thus cut out, the fuselage should have minor 'built-in' side thrust and right rudder. The wings and tail had to be flipped over, so that the bend goes with the dihedral. I have also taped the leading edges of the wing and horizontal tail.
2. I didn't see any bleeding of the red Stars. I think it is because I applied glue stick to where I want the markings and I didn't linger the marker pen over the edges of the paper template/stencil.
3. I inserted CF strips into the foam because it will result in a stronger mount for the geared motor and the fuselage can be stiffer if I add in short strips or tape to bind the two strips and foam together.

18 May 2015

The rudder was detached from the fin, the aileron servo horn cutout prepared then the geared motor, board and aileron servo was glued onto the fuselage.
The wing was completed after blenderm tape hinge, hinge groove cut out glued, then the aileron horns was cut from the pvc plastic sheet and thin wire hooked up the aileron servo horn to the ailerons.
In the foreground is the wing and horizontal stabiliser jig. The wing was grooved on the centreline and glued to the fuselage with the jib. Reinforcing angled strips was glued to the fuselage and wing at the topside. Then the horizontal stabiliser was similarly glued to the fuselage with the rig and similarly reinforced at the underside. The rudder was chamfered, blenderm hinge attached to the rudder first before offering to the fin and fuselage. Thin wires and pvc horns were similarly used to connect to the board.

Ready to fly, it weighs 29.2gm and it took 3 hours to assemble and fit out the plane.

















Every plane must have a pilot. 10 minutes to draw, colour, cut out and glue.

Too much power! 13 cm prop and 29cm wingspan makes it uncontrollable. The first 2 had the model torque rolled, the next (and last) 2 test flights (lasting 3-4 secs) were at low throttle and slightest touch the model flicked.
CG was very forward, lots of 'up' elevator was needed. Ailerons were too effective, I have to reduce the throw by a lot, as it is, one touch and the model flipped over.

 

What I learned:

• It is nose heavy. My battery was placed as far back as possible to bring the CG as back as possible.
• 13 cm (5") prop on 29 cm (11.5") wingspan is asking for trouble. 44% prop to span.
• Assymetrical thrustline and offset weight is asking for trouble.
• My rudder pushrod is better than the elevator pushrod which was my 1st attempt on the model.

The original plan was 18". I printed all of it on a single A3 sheet. That is about 66%, and I used the outline for this model. I could do the full 18" span, but that would require 4 sheets of A3 paper. A reduction to 90% will have the plan printed on 2 pieces of A3 sheet and I think I shall do a slightly larger one from two A3 plan. This will result in 50% more wing area and 41% more span then the current one. 90%x18" = 16" span. I think that is quite good too. My aim is not to reduce the wing loading, my aim is to counter the torque better with the increased span and area, and the increased airframe weight will also lower the thrust to weight ratio slightly which will reduce the torque roll characteristics and enable the motor to be throttled up because all in consideration, prop to span ratio will then be reduced to a more manageable 31% as compared with the current plane.
I will also cut away the spinner portion of the fuselage and mount the motor nearer to the CG location. Then I wouldn't need to have the battery mounted so far back and the longer (and heavier) tail and fuselage can bring the CG to a more ideal location. Maybe I will do a foam spinner. With the increased length of the fuselage, I aim to group the gear closer together, The best scenario is with battery at cg, then I can use the different weight (slightly different) batteries without affecting the trim.

14 May 2015

Cut out paper patterns from plan.
Rub glue stick to the back of patterns and paste on 3mm laminated foam.
Cut out horizontal stabiliser.

Cut the foam through the pattern.
Transfer hinge line and centre line to the edge of the foam piece.

 3M Blenderm tape applied to the reverse side of the stabiliser.

Make V-groove to the hingeline.

Draw in the centre line by connecting the transfered lines. There is sufficient foam joining the two halves of elevator.

Trace the canopy outline on to a piece of clear PVC.

Cut the canopy and colour in the frame.

Cut out the fuselage and wing to the outlines.

Slot the fuselage for wing, tail, motor.
Cut out arc for elevator joiner.

Peel the paper pattern and cut out the markings and decoration.

Dab glue stick to the back of pattern and re-attach to foam blank.

 Remove paper pattern.

Add 3mm x 0.5mm carbon fibre strip to starboard side of fuselage.

The same process is applied to the wing.
Mark out where the ailerons will be.
Draw in panel lines.









In less than 2 hours, the major components are completed.









The markings thus applied, using marker pen and paper stencil, is quick but the edges are fuzzy because some ink will seep through the paper. A better job would be achieved if the stencil is treated beforehand, e.g. a coat of acrylic paint on the back of the paper would stop the bleeding through of marker pen.