Pistachio Scale

14 May 2024

The fuselage construction of 1/2"x1/32" rubber motor mount is sheet construction that'll serve as anchor points for cabanes and undercarriage. The top and bottom can just be pre-formed tissue, but pure tissue won't hold as it collapses easily. 

9 May 2024

Hey man, about that Douglas wing? After you minus the centre section, each wing halve is less than 6", you sure you want to spend the time to construct as per 9 April 2024?

If the whole wing is 30 sq inches and is 1/32" thick balsa of 9lbs/ft3, the entire weight is only 2.21grammes. Maybe the construction following 9 April 2024 would be 1gram. If 1/8" expanded foam is used instead, it will be 1.48grammes, now if the expanded white foam is sanded to airfoil, I think the weight is only 1 gram.

Therefore, use expanded white foam and ditch the construction method of 9 April 2024!  

To have a wing loading of 1 oz/sqft and only 30 square inches, the flying weight would need to be 5.91 grams.

 

18 April 2024

Summary of how to mark and prepare all the parts to build the fuselage of a 10" wing span U.S. Army Douglas Observation YIO-43 from a reduced print of a 22" wing span plan from Outerzone.

Drawing the profile of the fuselage

1. Trace the profile of the fuselage from the reduced print. We're re-designing the construction method, much details will be ignored, but some would remain.
2. Transfer the datum line to the tracing.
3. Draw a parallel line to the datum, at the cockpit line. Draw another parallel line to the bottom of the datum line. These 2 lines indicate the rubber housing sides.
4. Draw perpendicular lines to these 3 lines. They indicate the chosen formers' position and where the profile outline intersects, indicate the depth of these formers.
5. Measure the formers' width from the planform of the fuselage and indicate them on the tracing at each former's location. 

Fabricating the formers by drawing onto a 1/16" balsa wood sheet.

1. Draw a centre line along the grain.
2. Draw perpendicular lines to the centre line to indicate the datum of the formers.
3. Draw parallel lines and perpendicular lines; fuselage's depths and widths at each former, the constant side housing.
4. Use a circle template and draw circles in the datum line of the formers to clear the rubber motor.
5. Use circle template and draw half circles to the top and bottom of the formers so that they become radiused rectangles.
6. Trace the radiused rectangles on the inside with a thick pen if the side housing and plankings are from 1/32" balsa. If any is from 1/16" or thicker, then you have to trace an inner outline with the same width, free hand would do. 
7. Cut rough and sand until the pen marking dissappeared. Cut and sand the central hole that clears the intended rubber motor.
8. Reinforce the formers if their edges are lesser than 1/8".

Rubber Housing Sides, draw on 1/32" balsa wood sheet

1. Draw 3 parallel lines with equal spacing to indicate the width of 2 housing sides.
2. Draw perpendicular lines across to indicate the formers' positions.
3. Optional: glue in 1/16" reinforcement or former stoppers at intermediate former positions.
4. Cut the whole housing sides but don't split the sides yet. Make it 1/8" longer at the nose.
5. Chamfer the tail end of the 2 housing sides so that they can meet together when the tail is brought together according to the planform.
6. Split the 2 housing sides to left and right pieces.
7. Optional: curl/bend the nose ends of the separated housing sides so they can approximate the planform at the nose and can wrap the nose former.

Notes on the removable nosepiece

1. Cut the removable nosepiece from 1/16" thick balsa sheet or the very thick cardboard (about 1.2 mm thick). It is a disc because the real aeroplane example has a spinner. 
2. The nose end of the housing sides are capped with 1/4"x1/16" thick balsa strips, the grain runs perpendicular to the grain of housing sides. If the removable nosepiece shall be much larger than the nose end of the housing sides, add additional 1/4"x1/16" thick balsa strips to the top and bottom capping.
3. Sand the cap-reinforced nose end of the housing sides to match the removable nosepiece.
4. Add 1/4" strips of the very thick cardboard to a 1/16" x 1/16" balsa strips, equal length. These are tongues that are glued to the removable nosepiece and fit inside the top and bottom capping strips of the nose end. The tongues prevent the removable nosepiece from spinning with the propeller and allows fine adjustment to the thrust line by adding shims between the removable nosepiece and the nose end of the housing.
5. Add in the plastic thrust button (re-purposed from the end cap of Pilot G7 ink tube) to the removable nosepiece, a snug-fit is good enough.
6. Fabricate the shaft from a straightened paper clip. One end is bent 90 degrees, it is bound to the underside of the propeller with thread and superglue. This avoids making a hole through the propeller. The other end is then fed through a glass bead and then the plastic thrust button on the removable nosepiece and finally a rubber hook of either a round or diamond shape is bent and the excess wire is snipped off.  I am thinking that a diamond hook is better for the house-hold/office rubber bands.

Since the removable nose piece is simply a disc, you can make many removable nose pieces with different propellers, e.g. different diameter, pitch, shape, 3 blades, with hook for winder, with engaging ramp for free-wheeling or when the original piece is broken beyond repair.  

Assembly

1. Choose the widest intermediate fuselage former and use white glue to glue it to the rubber housing sides. Before the glue sets, glue the tail end. Place the housing sides on edge, over a table edge so that the former cannot interrupt the placement This is important to make sure the positioning of the housing sides is as accurate as possible. Set to dry before proceeding with next step. If superglue is at hand, use any combination of tape, clip/peg, or rubber band to hold the 3 pieces in position, and then use superglue to set in position.
2. Glue in the nose former (or frame), allow for thrustline angles.
3. Glue the remaining formers.
4. Cap/plank the formers with 1/4"x1/32" balsa strips. The strips may be curled or bent if necessary.

Covering

1. Finely sand to prepare the fuselage for covering.
2. Cover with overlapping tissue to the housing sides, caps/planks etc. Covering makes the individual components act as one. 

17 April 2024

Laminated formers is possible but is more work and due to spring back, not that accurate. Remember that simplicity is less or easy work, and we wish to have that for our pistachio/grapenut scale model airplanes. Formers cut from sheet material are accurate and stable, they do not have springback.

Sheet formers may be cut or sanded from balsa, EPS, XPS or depron-like sheets.

Yes, you will have to make a 1/2" hole for the rubber motor to pass through and perhaps reinforce those formers where the material is less than 1/8" width.

For ease and accuracy of assembling the fuselage, glue to the 1/32"x1/2" motor housing sides pieces of 1/16" square strips at the formers' back/front positions. This forms the backstop (or front stop as the case may be) to the formers and eliminate the alignment mistakes.

  

16 April 2024

Fuselage formers

Where the fuselage's bottom profile has a significant compound curve, use 2 ply lamination for the bottom formers. Ideally, a 3 ply lamination of 1/32" balsa is stronger and more stable. A 2-ply lamination will also work to some capacity which will be sufficient for a pistachio scale plane. Glue them to the motor housing and they add to the strength and integrity of the motor housing. Cap the bottom with a curled 1/32" balsa strip to lock it all in place. If there is a main undercarriage, use two of such former to achieve stability and put in extra strip across these 2 formers to provide a base for the main undercarriage. A matrix of the housing sides, the formers, the bottom cap piece and the side pieces confers much structural strength. It is simpler to have laminated formers. However, if there is no internal clearance requirement in the fuselage, EPS foam block could be used (but consider the difficulty in sanding). You could use hollowed out XPS foam block and that will sand easily and because if it is weighty, it is useful weight because it is at the nose end, all considered though it is still a lot of work for little to no strength if it is glued to the motor housing. Where the members are non structural and only need to be supporting the tissue covering, then simple formers cut from 1/32", 1/16" or 1/8" balsa sheet is ok, you could also use formers made from foam. 

Making a laminated curved balsa piece (single curved surface, relying on the induced stress of the balsa wood)

1. Pull and tape wet 1/32" balsa strips to a pre-shaped former until dry. The former can be made from Depron type of foam sheet.

2. Pin wet 1/32" balsa strips along the plan until dry. Do not pin directly against the wet balsa strip as it will cause kinks rendering it useless, use scrap balsa pieces to spread the force on the balsa strips.

3. Make an adjustable jig so that the wet balsa strips can be clamped together. Ideas : on a sturdy base, fit discs, rollers, flat strips. 

15 April 2024

Simplify the fuselage construction for a Pistachio Scale Plane

Earlier, I mentioned shortening the motor housing, today, I think the motor housing should be the length of the fuselage because the rear end of the fuselage needs to be supported and it is easier to obtain the correct fuselage planform. 

The idea of the motor housing does not change, it is just integrated fully into the fuselage and minimise the effort to make a correct planform. The additional weight is small, especially when 1/32" thick balsa was used as the motor housing sides.

Anyway, the main difficulty is maintaining the space between the housing sides. You cannot place any balsa members in the centre to space out the housing because that's where the rubber motor runs. You could glue pair/pairs of balsa members to the top and bottom edges of the housing, but this is only possible if the depth is 3/4" to minimise the interruption when the rubber motor rotates.

And so, to simplify the housing, use depth of 1", it will be more durable.

The fuselage planform as identified from the nose to tail: The nose former, a pair of 1/4"x1/32" spacers, the motor peg former and finally when the two housing sides are brought together.

Form a slight curl by wet bending the nose end of the housing sides and V-cut or >-fold the housing edges if necessary to blend to shape, Glue the peg former, bring the tail end to close, bring the nose end to wrap around the nose former and glue to the top and bottom of the housing sides, the pair of 1/4"x1/32" spacer. 

Ultra-Simplified Pistachio Scale Fuselage with Integrated Motor Housing

Here's an even simpler approach to your Pistachio scale fuselage with the motor housing built directly into the structure:

Materials:

• Two balsa sheets (1/32" thickness recommended) - slightly larger than your desired fuselage size
• Wood glue suitable for balsa
• Sandpaper
• Razor blade or balsa cutter
• Water (for wet bending)

Steps:

1. Fuselage Sides:

   • Cut the two balsa sheets into rough rectangles, with a width slightly exceeding the desired fuselage width and a length a little longer than the planned fuselage length (including the motor housing).

2. Motor Housing and Fuselage Shape:

   • Wet the balsa sheet near the nose end (about 1/3 of the length) to make it more pliable.
   • Carefully bend this section upwards on both sides to create a gentle curve, forming the basic fuselage shape and motor housing pocket. You can use a dowel or rounded object as a guide for shaping.

3. Motor Peg Former (Optional):

   • If your motor requires a separate peg former for alignment, cut a small balsa piece to fit inside the motor housing pocket at the designated location and glue it in place.

4. V-cut or Folded Tail Closure (Optional):

   • To create a pointed tail shape, you can make a small V-cut at the rear end of the balsa sheets (before bending) and glue the cut edges together to form a point. Alternatively, make a slight fold inwards (like a > shape) at the tail end to create a tapered look.

5. Joining the Fuselage Sides:

   • Apply wood glue to the top and bottom edges (along the length) of one balsa sheet.
   • Carefully place the other balsa sheet on top, aligning the edges and ensuring the motor housing pocket is formed correctly. The bent nose sections should meet at the front.
   • Clamp or hold the sheets together firmly until the glue dries.

6. Tail and Nose Closure:

   • Once the main body is glued, trim any excess balsa at the tail end to achieve the desired shape.
   • You can add a small, thin balsa piece to close the tail opening completely (optional).

7. Shaping and Finishing:

   • Sand down any uneven edges or imperfections after the glue dries.
   • Use a balsa stripper or file for more precise shaping if needed.

8. Motor Installation:

   • Create a small slot at the rear end of the motor housing to allow the propeller shaft to exit.
   • The motor can be glued directly to the inside of the motor housing pocket.

Benefits:

• Extremely simple construction with minimal parts.
• Integrates motor housing for rear support and easier planform shaping.

Considerations:

• This method relies on shaping the balsa sheet during the wet bend, so practice on scrap balsa first to get the desired curve.
• The 1/32" balsa might be delicate, so handle it carefully during shaping and construction.
• You might need to add a small reinforcement strip (like a landing gear mount) later if the fuselage feels too weak.

Additional Tips:

• Use a light but strong wood glue specifically formulated for balsa models.
• A light coat of clear dope after sanding can improve the finish and add strength (optional).
• Ensure the motor housing allows smooth rotation of the rubber motor without any rubbing.

This approach offers a very basic and quick fuselage construction. Remember to customize the shaping technique and add reinforcements if needed based on your specific design and motor size.

   

12 April 2024

Tiny Timbers, Big Fun: Building a Pistachio Scale Plane

Building a model airplane at pistachio scale is like creating a miniature masterpiece! But with such a small size (think 8-9" fuselage!), achieving complex details can be tricky. Here's how to keep things simple and hopefully, it'll fly:

• Think Big Blocks, Not Tiny Tweaks: Forget fiddly formers and delicate stringers. Instead, use solid foam blocks to build the fuselage. This simplifies construction and keeps your workload manageable. If you are doing the 'sticks and tissue' way, change it to "blocks, slabs, sticks and tissue". You only need to create a strong enough motor housing of 6" or less to handle the pull of the rubber bands (read on for my suggestion). Everything else is more for aesthetics, you can still add a few formers to pretty things up.

• Simple is Spectacular: At this scale, focus on clean and well-assembled construction design and techniques rather than chasing ultimate precision. Neatness will go a long way in making your plane look fantastic! Do less, don't do more and don't add too much detail to chase fidelity.

• Strength in Simplicity: Remember, even a tiny plane needs some muscle. The motor housing area within the fuselage is key. Make sure it's strong enough to handle the tension of the rubber bands. 2 slabs from 1/32" thick balsa sheet with cross-grained formers at the front and back is strong enough to handle the tension of the household rubber bands. Don't over-engineer and complicate, it's only 6" long!

Basic Fuselage Design

If the aeroplane subject is near flat-sided, you can use 1/32" balsa sheets to build up the fuselage. There won't be much weight savings if you switch to a frame construction. This is because longerons and spacers that uses strips thinner than 1/16" square will result in a lot of breakages during handling and the glue, even when applied sparingly, adds to the weight. 

If you must choose a subject that has large elliptical or curvaceous cross sections, you can use thin slabs of expanded foam suitably hollowed out and strengthened for motor housing. It will be very light, but the amount of fine sanding is going to get you.

For a subject that has moderate or even small elliptical/curvaceous cross sections, you can build a motor housing to the planform and then add bits of balsa or foam to make up the rest of the fuselage.

Motor Housing

This is the core of the fuselage. It is the structural component that handles the stress of the rubber motor and impacts, everything else is attached to it. 

Identify on the side profile where the rubber motor will run and how long the housing is going to be. You do not want to answer that it is from head to tail. Think of the final CG and the space limitation, and you'll find that the motor housing is only about 60% of the length of the fuselage. There are 3 main components: 2 lengths of 1/32" thick balsa (no less than 3/8" wide), 1 nose and 1 tail former of 1/16" thick balsa.  The nose former is set to the thrust line. If the nose former has straight sides, you can pre-bend the nose end of the housing sides to form a curved planform. If the nose former has to be small and round, remove a V wedge out of the nose end of the housing sides, close the V and you have an approximation that gives it both a bit of curve planform and because it is a slight V, it fits better over the nose former. At the tail end of the housing is the tail former where the tail end of the fuselage is framed up. 3/8" ahead of the tail former glue 1/32" short pieces to the 2 housing sides to provide bearing surface to the 3/32" bamboo motor peg. All junctures may be reinforced by gluing balsa and/or tissue pieces.

Fixed Noseblock with Motor Access - Pistachio Power!

Since the removable noseblock concept is a bit more work and weight, here's an idea for your fixed noseblock and yet with motor access: simply allow an opening at the bottom of the fuselage. When not flying, we rarely look upwards at the model, so the bottom slot is visually hidden. Optionally, cover with painted light weight tissue connection, just make sure it peels off cleanly without damaging the fuselage.

Remember, at this scale, functionality takes priority! The slight visual difference from the bottom is a small price to pay for the ease of motor changes. If you need further convincing, consider that the No-Cal version has the entire starboard side exposed!

9 April 2024

Construction ideas for 10" wing span U.S. Army Douglas Observation YIO-43, reduced print of a 22" wing span plan from Outerzone.

Removable noseblock

The whole propeller and spinner should come with a removable noseblock so that rubber band can be fed to the fuselage and hooked to the propeller.

The concept: To receive the removable noseblock, former 1 ("F1") shall be cut from 1/32" thick cardboard glued to the fuselage sides and the square hole reinforced with 1/16" balsa strip. The square hole is to receive the 1/8" thick square balsa/foam block that is glued to the removable noseblock. The removable noseblock is made from 1/8" thick balsa/foam sheet, and it is shaped when it is positioned to F1 and an oversized spinner disc ("SD1") in placed. Fit the thrust bearing on the removable noseblock, i.e. SD1. 

Propeller

1. Cut 2 pieces of spinner discs ("SD2", "SD3" which is a smaller version of SD2) from 1/32" thick cardboard.
2. Cut 3 pieces of blades from thin plastic cup, cut 3 pieces of blade support, 1.5"x1/8"x1/8" balsa strips with one end sanded to 45degrees, assemble and glue. 
3. Make a ramp from a short section of ink tube.
4. Fit spinner thrust button to SD2, insert ramp tube, glue the square ends of blades to the flat side of SD2, glue SD3 over all.
5. Straighten a paper clip, bend one end to a hook, insert straight end through the inner tube of the nose thrust button, through the spinner thrust button, bend to a loop so that it can engage the ramp.     

Fuselage

The key feature of fuselage construction is an integral horizontal crutch, everything else is built up from the basic key feature. There are two main members of the horizontal crutch, curved by putting spacers between 2 slabs of 1/32" balsa sheet. At the nose it is glued to a 1/16" cross member to receive the removable noseblock. Another feature is that the formers may be a combination of the traditional flat type and a simple wet/heat bent balsa strip 1/8"wide by 1/32" thick that is anchored to the key horizontal crutch.

Cabane and rigging

Use small diameter bamboo dowels to make up the wing cabane structure, the top rigging post and horizontal stabiliser support. Bamboo is used because they don't break as easily as balsa. Rigging is fine cotton thread superglued at rigging points, purely for show. Rigging points may be reinforced with paper discs cut from photocopier paper. Only the wing cabane is structural, it secures the wing's CS with the horizontal crutch, drill holes accurately in the CS with a template and let the dowel fit in small slotted cardboard pieces at the horizontal crutch for better gluing surfaces. 

Wing

This wing design prioritizes minimal weight and drag, similar to a sail. Here are the key features:

• Strong Leading Edge: A sturdy leading edge (1/16" x 1/8" strip) forms the front of the wing and provides stability.
• Optional Spars: For additional support, one or two spars can be incorporated:
  • Single spar: 1/16" x 1/8" strip
  • Double spars: 1/16" x 1/16" strip (each)
• Thin Trailing Edge: To minimize drag, the trailing edge is made from thin paper, avoiding the drag created by sanding balsa to a taper.
• Minimal Ribs: A small number of ribs (e.g., 4) made from 1/16" thick material maintain the wing's shape while keeping weight low.

This design concentrates drag on the leading edge and spars, keeping the trailing edge sharp and efficient. This approach offers a lightweight and efficient wing suitable for various applications.The key concept is a strong (1/16"x1/8" strip) leading edge, if single spar, 1/16"x1/8", if double spars, 1/16"x1/16", thin trailing edge of paper (avoid sanding balsa to taper and being less drag), all spaced out with minimal numbers of 1/16" thick ribs. Most drag will come from the leading edge and spar/s, the trailing edge is razor sharp. It is like making a wing sail. 

1. Cut a pair of the curved outline from thin photocopy paper ("outline").
2. Tape a silver tissue piece on a flat surface, decorate with lines of ribs and ailerons.
3. Flip over the silver tissue and glue the outline.
4. Prepare ribs ("R1", "R2"), dihedral template, spars and leading edges from 1/16" balsa sheet. Leading edge being 1/8" wide, spars being 2 pieces of 1/16" wide.
5. Prepare centre section ("CS") from 1/32" balsa sheet, wet to pre-curl.
6. Glue CS to angled R1, glue leading edges and spars to angled R1 and straight R2, prepare for covering.
7. Glue the prepared tissue to top of the wing frame. Complete the finishing with EZE dope.
8. Remove wing from board, cut and sand the dihedral joints through the CS.     

Stabiliser

Use the same method as the wing. The horizontal is first glued to the fin and then the fin is glued to the fuselage.

Canopy

The concept: Creating a canopy for your miniature aircraft is crucial, but keeping it lightweight is equally important. This method tackles that challenge by transforming clear parcel tape into a realistic greenhouse canopy. The beauty lies in its simplicity. Since the model is so small, the tape itself provides enough rigidity to act as the frame. By adding thin black lines directly onto the tape, we can mimic the intricate frame structure of a real greenhouse canopy, achieving a detailed look without adding weight.

Simplified Construction but it'll smudge: 

1. Draw a developed plan of your canopy's individual panes on a separate piece of paper. Tape this blueprint down to a flat surface. Secure a sheet of clear parcel tape over the blueprint, sticky side facing up.
2. Cover with another layer of clear tape, sticky side down. Gently press to remove any air bubbles.
3. Draw with a sharpie or permanent marker the frame structure.
4. Cut out the entire canopy shape from the double layered tape. Fold it along the creases to form the 3D structure.
5. Wait until your model's fuselage (body) is finished and painted. Trim the canopy for a snug fit with minimal gaps on the fuselage. Secure it with spot glue and camouflage any remaining gaps using small pieces of silver tissue paper. You can also re-trace with sharpie/permanent marker.

Experiment: Try using sharpie, permanent marker, paint pens to shade a piece of transparent parcel tape to determine which pen works satisfactorily. 

• The ideal pen will leave a visible, well-defined mark without smudging or significantly reducing the transparency of the tape.
• Based on your experiment, choose the pen that offers the best balance of these factors for your project.

Construction:

1. Canopy Frame Creation:

   1. Draw a developed plan of your canopy's individual panes on a separate piece of paper. Tape this blueprint down to a flat surface. Secure a sheet of clear parcel tape over the blueprint, sticky side facing up.
   2. Take a small piece of paper, color one side silver and the other gunmetal. Cut this into thin strips and color the exposed edges with a black marker. Carefully lay these strips onto the sticky tape, mimicking the frame structure you see on your blueprint.

   Canopy Shaping and Attachment:

   1. Once the frame with the strips is complete, cover everything with another layer of clear parcel tape, sticky side down. Gently press to remove any air bubbles. Now you can carefully cut out the entire canopy shape from the layered tape and paper. Fold it along the creases to form the 3D structure.
   2. Wait until your model's fuselage (body) is finished and painted. Trim the canopy for a snug fit with minimal gaps on the fuselage. Secure it with glue and camouflage any remaining gaps using small pieces of silver tissue paper. You can even add a touch of paint for a flawless finish.

Undercarriage

Making a functional and stiff undercarriage complete with wheels that spin would either require a lot of work and increased weight. The anchor points have to be reinforced and thin wires or steel pins have to be used.

An alternative is to make up a simple main landing gear from balsa. The wheels are made from depron foam and cannot be spun. If it is necessary to reduce friction, glue small fishing line to the contact points. so that they can slide on hard floor easily. At the fuselage juncture, the attachment is thin rubbery foam glued to the fuselage reinforcement rails of 1/16" sq balsa. It would be durable because the soft mounting will give way on impact and spring back to its position.

The tail gear is just a piece of 1/32" cardboard cut to shape and coloured accordingly, because it measures less than 1 cm in dimensions. 

Air scoop, radiator, exhaust, machine gun and rail, venturi, pitot tube, step plate, spreader bar

These are non-functional and can be modelled from paper, card, foam and balsa.  

8 April 2024

The fuselage will house 2 looped pieces of house-hold rubber bands. Bear in mind that if it is a motor stick, a 1/8"x1/4" balsa is stiff and strong enough. Make up the fuselage sides of 1/32" balsa sheet. Each side has a doubler of 3/8"x1/32" balsa strip. This long rectangular doubler piece is glued to the inside of the fuselage sides, once at the nose end, once in the middle with a 3/8"x1/4"x1/16"thick spacer and finally at 1/8" pass the motor peg. Note that only the middle of the doubler has the spacer piece, this is to create a gap between the fuselage side and the inner doubler, and by tensioning over a form, the fuselage has a curved planform. For the motor peg location 1/16" combined thickness is sufficient, there is no need for a cross-piece of 3/8"x3/8"x1/32"thick reinforcement plate.

Trim the nose ends for thrustline. Glued top and bottom cross pieces 1/4"x1/16"thick to the doublers. Then it is a simpler matter for a removable noseblock with 1/8"x1/8" cross piece to house over the reinforced fuselage sides. What remains is to glue the tail end of the fuselage sides together before adding top and bottom formers to the fuselage doubler. This horizontal crutch construction is then readied for stringers and reinforcement pieces. 

In the photograph are 2 pieces of plastic salvaged from the ink cap of "Pilot G-2 07" pens. I think this will have multiple uses, first things that come to mind are nose buttons and wheel hub as is. As can be seen in the photograph, it fits a paper clip. It is light, the wobble is slight and the surfaces glide over each other easily. The outer ridged tube can be pared off if necessary. The top lip's diameter is 1/4", the inner tube's OD is about 1/16", the overall height is 3/16" and the 1/4" lip is about 1/32" thick.

A removable nose-block and propeller is essential for my model, without it, I cannot change the rubber bands. The nose-block can be made from sheet balsa, minimum of 1/16" thick, but 1/8" overall thickness would be preferable for easy handling. I could make one from the very thick cardboard of 1/32" thick because unlike balsa, cardboard's strength is all-round. An idea is to have a 1/16" balsa base topped with the 1/32" cardboard. To locate the removable nose-block means I have to provide sufficient depth for at least a single dowel peg, preferably two. So when constructing the nose end of the fuselage, add 1/8" balsa to the rear of the nose end. I can cut 2 identical pieces of 1/16" cardboard formers, one will be fixed to the fuselage and the other to the rear of the removable nose-block.  I would just make 2 spinner back discs from the 1/32" thick cardboard, one will be fixed to the front of the removable nose-block and the other spinner disc accepts another end cap and propeller. Making 1/16" diameter holes through balsa and cardboard would be easily done by using pins to insert through follow by a drill bit to widen. The Douglas aircraft has a spinner, but at pistachio scale this is too fiddly to do well. After the propeller is secured and working properly, then think about beautifying it. At pistachio scale, 1/8" square balsa shaft seems huge, but anything smaller is not suited for propeller turning.

Douglas is a 3 bladed propeller, for ease though, a 2 bladed propeller can be substituted. The paper clip would weaken the 1/8" balsa strip too much. Instead, slip in endcap and spinner disc, bend 90degrees and tie and cyano'd to underside of a thin bamboo dowel. Only then glue the propeller blades and a flat rubber piece to represent the spinner cone.

To make a 3 bladed propeller, rely on 2 spinner disc to capture the 3 blades, and in this case, the 90degrees bend is over the top disc. Similarly, a triangular flexible foam piece can be glued to the top disc to represent the spinner. At pistachio scale, it would be acceptable, only with larger scale type will the spinner be focused upon.  

5 April 2024

Pistachio scale refers to a rubber-powered miniature replicas of real aircraft and have a wingspan of no more than 8 inches (20cm).

Are they suitable for me? No, while they use simpler construction techniques and require few parts, they demand precision and care when working with small parts and lightweight materials, and flying is tricky as they are sensitive to wind and air currents. They are not a good option for beginners. However, if anyone is interested in a challenge, this is one. Once you manage to build one, you will bream with pride and confidence especially when your modelling friends are surprised by your handicraft. Getting the miniature craft to fly requires dedication and practice, so be forewarned and be mentally prepared. If you like tinkering and problem solving at minimal costs and space, this may be for you. Looking for something easier, try Walnut scale. 

According to Gemini:

• Pistachio Scale: Up to 8 inches (20 cm) wingspan. These are the smallest type of free flight model, known for their extreme miniature size and delicate construction.
• Peanut Scale: Up to 13 inches (33 cm) wingspan. These are also quite small and simple to build, making them a popular choice for beginners.
• Walnut Scale: Up to 19 inches (48 cm) wingspan. These models offer a bit more complexity than Peanut scale while remaining relatively manageable.
• Sport Scale: Typically larger than 24 inches (61 cm) wingspan. These models are more detailed and require more experience to build and fly.
• Coconut Scale: Greater than 36 inches (91 cm) wingspan. These are the largest and most complex free flight models.

OK, I printed out a a 22" span model on A3 paper and it turn out to be 9" wingspan, close enough for my pistachio scale. The aircraft chosen was a Douglas YO-43, a complex aircraft. I could have chosen a simpler cabin civil airplane. Douglas YO-43 challenges: Parasol with cabane and rigging, 3 bladed propeller, free-wheeling, horizontal tail in middle of fin, oval cross sectioned fuselage.

1/32" balsa sheet, bit of 1/16" balsa sheet and card, depron foam, guitar wire, rubber bands, photocopy paper, tissue, bamboo/wood, plastic tubes from used pens, aluminium from soft drink can.