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Author Topic: Pilatus PC-6 1:60 paper plane build  (Read 3473 times)
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cavelamb
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« Reply #25 on: December 20, 2013, 11:25:41 AM »

Such a cool thread!
Thank you all.
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slowfly55
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« Reply #26 on: January 07, 2014, 03:56:36 AM »

Happy New Year to all followers of this thread!

I started the new year building the wing. I dwell a little longer on this subject, as the wing structure of this PC-6 model is a specific paper structure - light yet nevertheless quite stiff. And as you all know it is the wing that makes a model a good or a bad flyer.

Wing construction doesn't follow the plan, that is for a conventional profile wing with upper and underside. I need only one side, the wing upper surface, that was printed on the sheet, and build it into a curved plate - probably the best indoor profile. Admittedly this is not scale, but with the Red Cross livery chosen for my model, where both sides of the wing are similar, this handicap should be tolerable.

When cutting out he 2 wing halves I added tabs 4,5mm wide on both edges, LE and TE. These tabs are formed into tubes by means of a 1mm dia steel wire.Glueing is with a Glue Stick and must be done extremly sparingly to avoid downward bending of the wing when it is finished. I apply glue with a toothpick and then press hard against the wire with a steel ruler as you see in the picture below. So I work for about an inch of the LE or TE and then go to the next inch. Once more when the tubes were finished I was surprised, how solid this very light paper structure really is.

Then I bent the symmetrical curved profile into the wing by folding them along the two lines. As you see in reality the profile is not curved but angular.
Also the immatriculation was added.

(continued)

slowfly55
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Re: Pilatus PC-6 1:60 paper plane build
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slowfly55
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« Reply #27 on: January 07, 2014, 05:21:30 AM »

Wing (2nd part)

Each wing has 2 ribs, made from light 0.6-0.8mm balsa. One at the inner end, where it is attached to the fuselage, the other at the point of the wing strut. I glued the ribs into the wing with the stick and then attached both wing halves to the fuselage using cement, so that they can be removed and relocated if necessary.That happens to me often, as it is a very delicate work to place both wings at the same angle of attack and dihedral.

Dihedral (5mm) on this model is not scale and I don't like it at all, as it changes the general appearance of the PC-6.I built a model without dihedral but couldn't get it to fly. I'll try again and hope to succeed one day.

When both wings were cemented to the fuselage I realized, that they were not in an straight line but slightly leaning backward. I had to remove them and add a thin rib, that was beveled to get the correct angles.

The wing struts are very important part of this model. They control not only the dihedral but also washin/washout of each wing. For this reason I build them solid by reinforcing them with a strip of very thin balsa.
The wing struts are also glued with cement, so that they may be moved later, if dihedral, angle of attack or washin/washout has to be adjusted.

I could hardly await the result on the balance. It was 2.020 g. And now I admit that I cheated by not using 50g/m2 but 40g/m2 paper for the wing. I felt that the model would turn out too heavy owing to the very solid landing gear and wanted to compensate this unwanted weight by a very light wing. The 50g/m2 wing I built first brought 100mg more to the balance.

At this point of the building I like to do a glide test that helps to evaluate the weight, that can or should be invested into the noseblock/prop assembly. This time the ballast needed for a perfect glide was an astounding little 270mg, very promitting and nursing the hope, that the finished model'll do without or with only very little ballast.

The last picture shows how I store my models. I hang them up with the wings.So the wings stay without warps even if there is much humidity.

slowfly55
Attached files Thumbnail(s):
Re: Pilatus PC-6 1:60 paper plane build
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Re: Pilatus PC-6 1:60 paper plane build
« Last Edit: January 07, 2014, 05:47:22 AM by slowfly55 » Logged
slowfly55
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« Reply #28 on: January 11, 2014, 03:10:01 PM »

There is not much to say about the noseblock/prop combination I built yesterday. The construction is not different from any stick and tissue indoor scale model. The pictures below illustrate some steps of this build.

If the prop shaft happens to be not 100% perpendicular to the nose block there is no harm done. On the contrary,
a slight deviation of 2-4° allows later to easily adjust the thrustline by simply rotating the noseblock.

The blades were made by the well-known procedure from small yoghurt pots. When the combo was finished the balance indicated 285mg. This is probably not enough to bring the CG forward to the correct point. The test flights'll bring it to light.

I forgot to mention that the prop has 94mm dia and 140mm pitch, i.e. a pitch ration of 1.5.

slowfly 55
Attached files Thumbnail(s):
Re: Pilatus PC-6 1:60 paper plane build
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Re: Pilatus PC-6 1:60 paper plane build
Re: Pilatus PC-6 1:60 paper plane build
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slowfly55
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« Reply #29 on: January 18, 2014, 05:41:38 AM »

With the noseblock/prop combination the model now weighs 2,485 g. So it should be a good flyer.

I prepared a 240mm loop of 0.72g/m TAN and made first test flights in the living room. These tiny paper models are so light, that bumps into the wall will not do any harm. The first flights were disappointing. I changed tailplane elevation, wing washout and used a lot of acetone. It didn't help, it was the prop, that produced too much flare .
I changed to one of the older props with less pitch and finally got a decent start in the living room. Next day in
the gym (6m height) the trimming process started from new. Best result at the end of the session was a 50" flight. I had some beautiful starts that would have produced 60+ flights in a better site, with the model climbing too high or too wide into the walls.
On the last picture below there is my Pilatus fleet with also 2 Pistachio PC-6 and a PC-21 test model (not yet finished)

slowfly55
 
Attached files Thumbnail(s):
Re: Pilatus PC-6 1:60 paper plane build
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Re: Pilatus PC-6 1:60 paper plane build
Re: Pilatus PC-6 1:60 paper plane build
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