3 cylinder model

17 October 2022

Over the weekend, I played around with the model and did this:

Mounting the Electric Motor (not the capacitor yet)

1. Cut one tooth pick into 2, about 2/3 long and 1/3 long
2. Glue the 2 pieces at opposing sides of the electric motor. I choose to have the wiring away from either picks.
3. Tape the picks and motor together.
4. Poke into the nose of the fuselage.

I didn't cut the reinforcing hard card base for the 2 picks. I think the base of the electric motor will not enter into the soft nose and also since it is 2 picks the lateral load should spread sufficiently.

The Engine

With the electric motor in-placed at what seems to be right, I proceed with the engine modelling:

1. Hot wire cut 3 pieces from drinking straw. I made a cube jig for this, the result is straightish but not really square, good enough.
2. Cover the tubes with silver tissue: 
1. Cap tissue: tissue over one end, gum it to the sides.
2. Cylinder tissue: tissue around sides, capturing the cap tissue ends.
3. Fin tissue: Draw black parallel lines, cut 3 strips, roll around the cap end.
3. Cylinder base:
1. Cut 3 strips
2. Cover with tissue on one side
4.  Assemble cylinder to base:
1. Glue 2 cylinders to one end
2. Glue last cylinder to middle
5. Glue the base onto the electric motor.

The Capacitor

This was left to the last because it can help to trim the model. I only did the casing for the capacitor to slide in. It is a section of a very large diameter straw with the piercing end, cut with hot wire cutter using the cube jig. The piercing/sloping end allows the slightly protrucing capacitor charging jack to rest and not to twist around. This tube was covered with silver tissue. The intention is to mount the tube like an underslung canister at the nose of the fuselage. It is not a scale feature but it is a fake feature and is convenient and easy. I don't have to cut slots in the fuselage for the capacitor. With the canister mounted, perhaps by a wire hook or just glued to the underside of the fuselage, the capacitor can be inserted or withdrawn, thus allowing the trimming of the CG.

Choice of having the capacitor below the fuselage is for pendulum effect and also thrustline.

Thrustline above CG will have a down thrust moment, thereby less angular thrustline will be required. The centre of drag should be nearer to the wing as that is the largest drag producer. Who knows, maybe the blocky undercarriage may also bring the drag centre closer to the thrustline and that would be ideal.

12 October 2022

Variation of yesterday's idea.

The engine will be the point of interest. Every pair of eyes will be drawn to it when they look for details. A bit more detail is needed.

Each cylinder is not a single cylinder but 2 cylinders, I can fit a bigger straw over a smaller straw. Or if I can't find 2 appropriately sized straws, split one to fit over the unsplit straw or maybe I should just wrap some paper/tissue on one end of the straw so that outwardly, it appears to be of 2 diameters. 

1. cut three identical length straw
2. cover with black tissue
3. strip of silver tissue with parallel black lines
4. wrap with strip of paper to bulk up
5. wrap with striped silver tissue over the paper rolled open end
6. roll the pre-striped tissue over the paper tube end, covering the tissue tabs of step 5 if any.  

The task now is to think how to make a mount that incorporates 3 tongues at the right positions (to glue on the above made cylinders), allowing electric motor to be centrally located fit and generally look like a crankcase. For durability, I want it to be made from flexible "EVA" foam.

3 prongs (120 degrees apart), hexagon (crankcase), rectangular (fuselage nose), motor pass through or insert through...

Ah ha! 

The electric motor with its two toothpick legs is to be inserted to the nose of the fuselage. As the fuselage is only white styrofoam, it would simply tear on each crash. I need to strengthen it.

The nose presented is a small rectangle. An idea is to cut a piece of rectangle from thick card and have  2 holes drilled/punched through to prevent the 2 picks from tearing away. This card has sufficient area as it covers the entire nose and does not interfere with the re-inserting of the picks (for down and side thrust adjustments).

The engine can basically be a piece of flat EVA foam with 3 tongues to which the 3 straw cylinders are attached. The foam piece is slotted at the bottom to clear the electric motor. This 3 cylinder engine is glued to a strip of EVA foam which is in turn glued to the hard card base. This strip need not be fashioned, it could be a 'U' shaped piece as its purpose is only to hold the engine to the nose. Yes, the crankcase is missing, but it's only a little bit. But if the visual bothers me too much, I can add thin card to slot over the EVA tongues before putting in the cylinders. The thin card is to cover the 5 sides out of the hexagon shaped crankcase.

Slightly more work is to cut and fold to make a hexagonal front cover, leaving the bottom and rear uncovered. The bottom is missing to clear the electric motor and the rear is missing to glue on the EVA mounting support.

1. Card nose
2. Insert electric motor, solder and mount capacitor
3. Test flight
4. Adjust CG and thrustline
5. no need to remove propeller and I can glue the engine and crankcase unit.

Oh!

Why bother with 3 tongued EVA piece? Just make the card crankcase and have enough gluing area to the base of each cylinder! No slots, no EVA piece and the cylinders can be glued staggered slightly! Just make the engine mouting EVA strip longer to support on the inside of the crankcase.

Hmmm...

Toothpick bound to the electric motor would be light and strong, but wooden toothpick is not bendable. How about something that can bend so that the thrustline can be adjusted?

Bind two wires (paper clip) to the electric motor? Or cut from stainless steel wire?

Another thought is matching the engine to the electric motor. The crank case would not fit snugly to the nose and the rear end of the electric motor would be offsetted from the centre of the fuselage.

Something to think about.

So, I will have to think how the engine can be glued to the nose (not the electric motor). Previous thought was a single looped strip glued to the rear of the crankcase cover, maybe I have to think how it can be glued to the rear of the engine (on the crankcase). The difficulty is how to fit foam mount to a hexagonal crankcase. Small short strips? Maybe inside of the top side of the hexagon behind the top cylinder and 2 stubs behind the lower 2 cylinders?

Oh! What if I glue a hexagon piece of EVA foam to the thick card motor mount? Then it is possible to locate the crankcase like a cap over this hexagon piece. 5 short straight strips can be glued to the hexagon piece to provide adjusting area as well as gluing area to the engine. 2 or 3 degrees off should not affect the fit since it is cardboard crankcase over EVA foam anyway.

11 October 2022

OK, I tried for an RC model but it was quite a lot of work for an untidy piece that I can not be proud of and I left it at that last year.

Now, for a 15" wingspan capacitor powered model, I think I will simplify a bit more so that it looks neater. The purpose is only to have something that suggests a motor from at least 2 metres away, and to consider that at the nose end, there will be knocks and bumps. Hey! My pilot is just an outline anyway.

At first I thought about doing up a single mould to make the cylinders by shrinking plastic tube. Then I drop this idea because any fins I put in the mould would unlikely be visible, much, since the shrinking will bridge over gaps and I am not going to try vacuum moulding. Paper tubes will look like paper tubes, so idea is dropped as well. Winding around with 3D pen was dropped because my experience was negative.

After much simplifying:

• mount is flexible foam to tack glue on fuselage's nose
• each base cylinder is strip of flexible foam with a slot to receive the cylinder top
• each cylinder top is just a piece of card paper glued at ninety degrees to the base cylinder

Frontal view is just 3 narrow rectangular strips equally spaced around, less disruption to the head-on airflow. Side and plan view will show some idea of cylinder tops. It should look the part from many angles when viewed 2 metres away, squint if necessary. 

1. Cut a card/paper strip and silver tissue both sides and draw in parallel black lines over the tissued sides. Cut 3 pieces for the 3 cylinder tops.
2. Cut 3 strips which has a slit/slot to receive cylinder top. If I don't want to cut a slit/slot, I could also leave it as that and glue the cylinder tops to its edge.
3. Cut a rectangular strip for the mount. Hot bend or glue strips to two opposing edge (for mounting to fuselage's nose). Hollow out for pass through or fit over of electric motor.
4. Assemble by gluing the 3 strips on the mounting piece, glue the cylinder tops to the 3 strips. 

After a while, I searched for Anzani engines and found photographs of actual engines. The cylinders is fairly uniform, the fins protruded only a bit. They were either black or silver. So instead of doing flat strips like steps 1 and 2 above, to improve the look, I revert to drinking straws:

• Draw parallel lines with black marker on silver tissue
• Cut a rectangular strip, the lined portion represents the fins, yes it is reversed, i.e. not silver lines on black tissue, but black oil based markers are cheaper and easily available.
• Glue tissue strip around a drinking straw and cut to length, repeat 3 times for 3 cylinders.
• Insert and glue the straw tubes to the 3 prongs of the flexible rectangular strips, with the strips at the back end of the straw for step 4.

8 June 2021

It depends what skill, tools, material and what size and weight of the model. In case of a peanut scale, my hexagonal crankcase is about 12mm OD and 10mm deep, and each cylinder is about 6mm OD and 10mm long.

The actual steps taken for the peanut model were:

1. Cut a strip of paper with tabs all-round, bend and glue together. Immediately place inside a circle template to adjust the hexagon shape.
2. Mark and cut from transparent drinking straw 10mm long segments with two slots, something like a 'E'. Two rings are next to each other on one end to simulate the finned cylinder, the last ring is at the other end and is the base of the entire cylinder to allow gluing.
3. Glue the cylinders to the hexagon.

Tips:

• Use circle template to hold the hexagon shape until the glue dries.
• Flatten the drinking straw to mark out the fins and base of the cylinder.
• Use scissors to cut the drinking straw to "E" shape.
• Open up the 3 loops and pass a small dowel through the 3 loops and finger roll to round the straw.
• Glue with UHU All-Purpose or POR, the near translucent cylinders and paper hexagon.

28 May 2021

To make something like the Anzani 3 cylinders in Y configuration for small aircraft models using bendy drinking straws in a fast and easy manner:

1. Crankcase is 6 sided. Cut strip of paper from photo-copy paper, mark 6 segments, crease on the lines, glue together and loop the strip around so that it is at least 2 ply thick to get a open ended hexagon. No need to make back or front to close because the motor will be there anyway and it is a very small engine model.
2. Glue small foam squares to 3 sides. Offset the squares so that when the assembled cylinders are glued on, the cylinders will also be offset in fore-mid-aft positions.
3. Extend the bendy portion of the drinking straw. Cut 3 equal length sections. Slit lengthwise if the bendy portion can not fit over the straight drinking straw.
4. Cut 3 lengths of the straight sections of the drinking straw. Slip the bending portions through one end, this allow 'exact' length of cylinders to be adjusted.
5. Glue the 3 cylinders to the foam squares on the hexagon crankcase.
6. Spray black, rub-in or dry-brush silver highlights.

Self-stabilised cylinders in case of crash?

1. As before.
2. Skip this step.
3. As before.
4. Where the cylinder shall meet the crankcase, leave a short 'tongue'.
5. Poke a slit through the crankcase to receive the tongues. When the tongues are at the rear, the cylinders can snap back and recover should they be knocked rearwards.
6.  As before.

Jedelsky style for small wings

11 October 2022

Respect to Mr. Jedelsky who came up with his jedelsky construction:

• thick balsa leading edge sheet (sanded to front-upper curvature later, making the leading edge stronger to withstand wing dings)
• thin balsa sheet rear of leading edge sheet (forming to the rear-upper curvature)
• identical ribs to maintain the airfoil (simplified one rib template for almost any wing planform and did you know that these ribs are longer then the wing chord for stable construction and excess protrusions shall be trimmed off after the top sheets are in placed?)
• if trailing edge at wing tip is shorter than wing root, washout results; vice-versa for leading edge taper and trailing edge taper towards wing tips. (automatically creating washout without causing stress to the wood components)
• when the wing tip is shorter than the wing root, the depth/thickness of the wingtip goes progressively lesser because the bottom of the ribs is trimmed off (automatically creating a tapered thickness across the span of the wing)

However, it is relatively heavier then a framework style wing construction, so it may be too strong (read "heavy") for small and very light wings because too much balsa is used. 

So the solution is to change this sheet construction to frame construction, but this loses some of its simplicity and adjustments have to be made and compromises accepted.

The first order of conversion may be using a rectangular section of thin balsa sheet to frame the trailing edge, leaving large area of wing that is rear of leading-edge sheet empty and to be covered by tissue. The front edge of this strip will present a slight bump air flowing underside, but this bump should not affect the airflow much because it is going to be used for a slow flying model and my priority goes to air flow over the upperside (and looks).

The second adaptation is to the ribs.

The jedelsky rib has the front as a straight slope and the rear as a curved slope to accept the trailing sheet. However, there is only a trailing edge strip in placed for a jedelsky frame-work styled wing, so the rear need not be curved. At the trailing edge receiving the thin trailing rectangular strip, it could be a straight slope as well. The original jedelsky idea is to leave the in-between proud of the rear edge of the leading edge and front edge of the trailing rectangular strip and when the glue has set, trim away in-situ to form that bit of curve for supporting the tissue covering. But each rib will be different for anything other than a rectangular wing planform because the leading and trailing strips are not paper thin. So this is not going to work, as I cared more for looks upper surface.

The compromise to make identical ribs possible is to make each rib to comprise of a lower main rib which is largely triangular in view for the gluing of the leading-edge sheet and trailing edge strip, and then an upper rib to support the tissue covering. These upper ribs are not identical, they have to be customised to each distance between the rear of the leading-edge sheet and the front of the trailing edge strip. It is not a cap-strip of consistent thickness; it is a trapezoidal extension on top of the lower main rib that is measured and cut to the actual distance.

   

Now, some checks for consideration.

It is going to be used for small, light, slow flying models. I would probably use 1/32" balsa sheet for the trailing edge sheet. This means the bump is equally small and on the scale of things, what is that over a mere few inches of wing chords? Maybe simple triangular ribs will be enough. If we view the model from 2 metres away, I think the 'bent' airfoil would look ok.

The main strength of the wing is dependent on the leading-edge sheet. Since the intention is to use 1/32" trailing sheet, the leading sheet should be slightly thicker, maybe a minimum of 1/16" for super light and upto 1/8" for rough and tumble. 

For 1/8" leading sheet, I think it is neater if the rear end is shaved to 1/16" or thinner for minimal sanding and better looks. So a simplified 'blank' for the 1/8" leading sheet is to have the rear edge shaved/sanded down from the middle of the strip to the rear end at 1/16", 1/32" if I am daring.

All the above is just thinking about it. When doing up for real, I may realise something I overlooked and adapt accordingly. 

Tethered flying

10 October 2022

There's a couple of ways for tethered flying.

Whip

Unpowered gliders is tethered to a string and then the other end of the string is tied around a long staff. I have seen this in magazine.

RTP (electric Round-the-Pole, Round-the-Pylon)

The power source is supplied to electrical twin-core through a commutator type contact at the pole/pylon to the electric motor in the model. By varying the voltage, the power variation cause the electric motor to spin faster or slower thus causing it to climb or glide. I have never tried this before and I'm sure I'll encounter many problems.

CL (Control Line)

This I have experience in my youth. One gets giddy by rotating around oneself. I have seen electric powered CL models, usually they carry the Lipo on board, but it is possible also to transmit power through 2 single core wires. 

CL will have longer lines then Whip and RTP.  Now if I were to fly indoor, it would only be the Whip or RTP. Whip means I would be in the centre of the flying circle and flying it all the way while RTP means I am positioned away from the circle.

Single tether flying

Now if I do a free flying model (an electric capacitor powered Farman Moustique comes to mind), I could insert a straightened piece of paper clip through the fuselage as a tether point. Then the other end of the line (can be any line, no need to conduct electricity and not care about electricity resistance of line) can be as long as the indoor venue allows, letting the model fly around a heavy base.  

Why?

• Basically it is just to tie a string to the wing or fuselage
• It will just fly under its own power around a pylon/base or you can hold on to the line if you wish.
• Tethered line can be long, short or anything in between. 
• No need for gears such as a pair of equal and exact lengths wires to pass electricity, wanting lower air resistance but also wishing minimal resistance to electricity flow. No transformer/adapter, no freewheeling contact points and matching pole, no controller (rheostat)
• Remove the tether point and model reverts to a free flight model.

Large field flyers

4 October 2022

There's a beach front with sprawling rough out front and across the road there's a large sandy field with clumps and scattered trees destined for future construction work. Both are unfenced and there's no flying restrictions.

Long and sleek flyer like a glider would be the best choice for air time and windy conditions.