Scale RC Model Airplane Design

1. Decide which airplane to model and the aim of this modelling project
Do you want it to fast, leisurely, sportive/aerobatic?
Do you want simplicity, lightness, smallness, durability? It is easy to have complex, heavy and large design with many structural weakpoints and take a long time to assemble or even change a battery.
2. Decide on wing loading of model
Find the wing loading of similar flying models that has the flying characteristics you can accept.
8 oz/sq ft is fast for a small model and as wing loading goes higher, the more difficult the flying.
3. Guess the flying weight of model
Gather as many of the equipment and weigh them. This means the motor, esc, battery, receiver, servos, horns, wheels.
Guess the weight for additional components that you didn't weigh or have to fabricate, e.g. pushrods, landing gear.
Guess how much your airframe is going to weigh.
Add all up and the total is the target flying weight of the new design.
4. Decide if the model will have sufficient thrust
Obviously, more thrust is better than marginal thrust.
you got nothing to fear if the thrust to weight ratio is 1:1.
5. Work out the wing area required for the model
Since you have the target flying weight, you can find the target wing area and in turn the target wingspan and such parameters.
6. Decide if you can build the airframe to the target weight
If it will be heavier, either resize it upwards, consider changes to the equipment if necessary, or use alternate construction design.
7. Visualisation of model
Visualise the construction method of airframe, mounting of equipment and components and make changes to the construction design if necessary. Crashes are inevitable, but some durability is always good.
8. Draw out the design if that helps or just start building

Generally, keep to a specific range of size, this way, equipments can be used interchangeably.

Convert HobbyKing's X22 to RC electric

Build

HobbyKing's X22 chuck glider looks like a F22.
The wingspan is approximately 12".
Here's a photo with a 4.5" prop placed atop.

I sliced the fuselage to remove a section of the fuselage and to make a propeller slot.

The removed section is further sliced to form top and bottom slices. The bottom slice is glued back to the fuselage and the upper slice is fixed with a knuckle hinge and restrained by 2 wire hooks. Blenderm tape is applied to top of both horizontal stabilisers and then both elevators is shapened. Motor is screwed onto the 2mm ply firewall and the assembly glued into slots at the sides of the fuselage cutout. 2 rectangular holes are cut out from the sides for the 2 servos and the 2 servos are glued in placed by squeezing CA onto the mounting holes. The foam directly facing the rear of the propellor is carved to an angle to lessen the drag. Pushrods and runners, receiver, esc, 'velcro' are then glued in placed. So far, 1 afternoon.

The model is completed for test flights.

Tests

First Tests
1. Crash with left spiral.
2. Added 5 gm weight to back, but still crash in left spiral.

Second Tests
3. Total of 10 gm weight to back, carved the foam to rear of propellor. Exhibits more thrust, flew in left hand circles.
4. Doesn't like to turn right at all. At slow speed, moving stick right has the model continue drifting.

Third Tests
5. Taped port wing to reduce washout, readjust elevons. Now it can fly in left and right directions.
6. OK, getting used to the characteristics (limit). Nice power zoom, but not unlimited.

Fourth Tests
7. Steam warp the port wing to remove its washout, removed all 10 gm of weight, 'flatten' elevator. Flies ok, smooth flyer with a bit too much stability, doesn't roll axially and in high alpha attitude at slower speed.

Flying

Have had multiple flights.
Does not fly inverted, ran out of elevator.
Barrel rolls, non-axial even with maximum elevator throw in the inverted segment.
Large loops.
Clean stalls (relatively).
Occassional tail wagging, no more since removal of 10gm weight.

Crashes

A few tumbles and slam crashes. Have broke the nose in 3 places, the nose now has a hooked beak look. Discovered 2 metal screws concealed by rubber nose during one crash, have since removed.
Reinforced with flat carbon fibre flats to the 2 ends of propellor cutout, and at top and bottom of wing.
Weight is ca 100gm.

Plus and Minus points

Good size to put in motorcycle carrier box.
Fuselage cutout is quite cavernous for RC gear.
Flies level (nose up attitude) at about 50% throttle.
X22 weighs 38gm when new, quite heavy.
Washout incorporated at both wing tips for stable glides but it means tweaking is necessary for RC flights.
A guy at the field said he has bought one from HK to try.

Suggestions

• Move prop cutout rearwards slightly to have a more rearward CG
• Remove 2 screws concealed by the rubber nose to lighten nose
• Steam warp both washouts for faster flights (leave some on starboard wing).
• Make the elevons area bigger
• Instead of a pair of CF flats to each end of propeller cutout, maybe rearrange into T-section for stiffness.
• Insert knuckle pin hinge closer
• Trim the foam more drastically before assembly. The fuselage cutout, the angled foam rear of propeller (maybe make it to a point?).
• Draw the panel lines before assembly. Spray some colour.
• Try a different 6A ESC (current Turnigy 6A Plush)

Jig for Gussets

Actually...(27 June 2014)

Since my intended gusset material is 1/16" balsa and I don't want to sand the cut/chopped gusset, I shall simply mark the angle against the grid markings of my cutting mat and use that as my jig for marking and cutting gussets. Simple, really.

I have made 1/8" gussets from a balsa strips. I positioned the strip against the grid markings of my cutting mat, this gives reference points at 90 degress intersection. A bit of slicing is required, slicing from the 90 degrees angle towards the 45 degrees angles to prevent bits of balsa breaking off if slicing the other way round. I used a new 11 blade, because it is stiffer than my NT cutter. The problem is not getting the slices perpendicular to the mat. No matter how lightly (and carefully) I sliced, it is not perpendicular. The skew is only a fraction of a millimetre but I can see it and it is more evident when using thin (non-gap filling) CA.

The previous thoughts of using a jig (below) is useless, because it doesn't ensure slicing accuracy and I don't need anything more to know where to slice the strips.

 

Uses

Gussets can be used to position formers, longerons and anything that needs to be set up at a specific angle. It is also very useful because it distributes the stress to a larger area if it is glued in placed. Used wisely, the resulting frame could be made strong yet light. A good examples of gusset use is at the trailing edge and rib juncture, a small contact surface can be enlarged.

There are times when multiple gussets are to be used throughout the frame. Aesthetically, it is pleasing if the gussets are identical. I don't like varying sizes and shapes of gussets when they ought to be identical.

The goal then is clear, to have a jig prepared for marking or cutting identical gussets.

Design idea 

A small base plate (also serving as a chopping board) marked with various angles, i.e. standard 45 degrees and 30 degrees and specific angles of model requirements crossed by the X and Y axes lines. By placing balsa strip of the desired width, place ruler over X or Y axis to cut once, and using the other axis to cut again and repeating the procedure will result in identical 90 degrees gussets with the right proportion of length and width. Skewering one of the axis will result in angled gussets of the same amount. Small blocks may be glued to the base plate to provide positive tactile feedback in case of failing eyesight and guide to the placement of balsa strip and ruler. Guides for balsa strip to be no higher than thickness of strip and the guides for ruler to be higher than the strip. Place them away from the cutting/chopping line of motion.
The limitation to this is that the gusset material has to be easily cut, not too thick, not too hard. When the gusset material is too thick or too hard, then maybe it ought to be sanded.

I don't suppose I will want to sand the gusset edges, but to adopt the same gusset chopping board into a gusset holding jig for sanding, have the edges of the base plate parallel to the X and Y axes, mark the angle line towards the edge and mark a parallel terminating on the other edge.

Construction

I think a 2" x 3" baseplate is big enough for my purpose. Material for baseplate may be thin ply, acetate, formica or even cutting mat. Material for guides is balsa, so that it may be scrapped away if need to.

Field sightings 12 Apr 2014

Spencer built and flown a foam mini cub on rudder, elevator and throttle.
The remarkable aspect is that the wing has no dihedral (practically), although he insists it has because he bent the wing upwards.
I wouldn't have tried to fly a high wing cabin monoplane without dihedral but he did it.

The other interesting aspect of his model, is the carved airfoil wing.
He said he used a chopper to pare down to approximate airfoil before sanding to final profile. His wing was made up of an upper and a lower foam blanks.

Model is very light, about 100 grams, is about 22" span.

Obviously rolls are out, and his 19g motor cannot do pull outs, inverted looks a challenge. It flies best when wind is only slight.

I think I could try his wing construction for my Blackburn Monoplane (original flat wing without ailerons, or with ailerons (logic being that given time and opportunity, the original Monoplane might subsequently be fitted with ailerons).

And on this day, I pass the soldering tip to Andy and a P-36 to Wong (foam/ply, ca 29" with HobbyKing Donkey motor and 7"x4" prop).

Blackburn Monoplane

Trimming Flights

Nothing extraordinary, I slipped the 2s500mah battery rearwards and it's fine. I didn't bothered myself to adjust the down and side thrust lines.

It looks slow when flying into wind. This will be last entry and here are the cropped snapshots.

Completing after Test Fly

The flights tell me that there is sufficient power from the Turnigy 2204-14  1700kv spinning 7035 propellor on 2S 500mah. It is flyable but not slow enough, after removing the 20gm noseweight I think it is still slightly noseheavy. With maximum up elevator trim, the model points upwards and requires full throttle to fly at approximately level altitude, I would think the CG is around there and would try a 8" prop next time.

Before the rigging, I did the pilot. The pilot's head and hands is from a clay that hardens after baking in oven. I got the clay online from www.banggood.com , cheaper than going to ArtFriend. The body arms and legs are from ArtFriend, a softish white bouncy substance called Super Dough (Paulinda). It cannot be detailed like a firm clay but can make folds and creases to the outer surfaces.

Do not put Super Dough in oven!

Starting with a bald head.

 

Then I added hair and made his pair of hands, baked them and joined all up in Super Dough.

 
 


Then I added the wings' rigging using thin nylon monofilament thread. The rigging is close to the real arrangement and the thread is practically invisible. I made hooks and such from soft wire to tie the thread and then used a black permanent marker to accentuate the rigging wires.

I folded pre-printed paper and glued on to the undercarriage wire to give the appearance of timber. It would be easier I think, if I attached the pre-printed paper to the main 'U' wires first, then insert the soft wire for the upper and lower cross bars, cover them with pre-printed paper, and finally do up the riggings. This way I would not need to make loops for the rigging at the lower cross bar and the timber look will extend to the bottom, looking neater. I did the hook design and installed above the lower axle because I was afraid that some lower rigging would bind the wheels.

For the side frames that were evident in photos of the real plane, pre-printed paper was glued to card, cut out, glued on.

I cut out and rolled two cones from pre-printed paper and glued them to the wheels, covering the ply disc and aluminium tubing.

Two yakult's drinking straw were heat bent, slitted and glued to the bottom of the "U" undercarriage wire, then with the same black marker pen, coloured to represent the skids of the real thing.

The rest of the framework at the nose were painted with the black permanent marker. This includes the firewall as far as I can reach it.

Components should be pre-coloured as much as possible, e.g. firewall painted installing the motor, framework painted before the cardboard side frames, skids painted before gluing to undercarriage, etc.

The model still lacks rigging between the nose and wing, the stabilisers, the cross bars, and some representation of the exposed portion of the 7 cylinders engine.

Test Fly

After flying the WBP-1, I was thinking the Blackburn Monoplane might be too heavy. Instead of completing the model with rigging, pilot and painting, I decided to test fly the model, even though it wasn't completed.

I added the pushrods and wheels. I could remove the entire undercarriage, but I do not fancy belly landing this model and the model would appear wierd.

Mass was approximately 210 gm, but the balance is at beyond 1/3 of chord so I added 10gm leadweight to the nose. The propeller is a 7035.

A Turnigy 2204-14 turn is installed. With a 2S500mah battery at storage voltage, the model could not hang from the 7035 propellor.

From HobbyKing:
Model: A2204-14
Cells: 2-3
Kv: 1450rpm/V
Maxx Eff: 74%
No load Curr. .3A
Max Current: 7.5A
Weight: 19g
Int. Resistance: 550mh
Dimensions: 27.6 x 11.5mm
Recomended Model: (3D 220g or less)
Recomended prop: 8040/2S or 7035/3S
This is similar to the AXi 2203/52 or 2204/54
Use a 10A ESC with this motor.

It should be sprightly.

History

This is how I would tackle this project.

From www.outerzone.co.uk download the peanut plan of a Blackburn Monoplane (Model Builder October 1975).

I wish to use my existing 2S500mAh batteries, Turnigy 2205 motor driving an 8" propeller and micro servos. The model is 4 channels (2 ailerons, rudder, elevator, throttle).

The pdf is upsized with a photocopier about twice.
The amount of enlarging depends on how many tiled pieces of A3, I don't like to tape too many A3 sheets but want something close to 26" wingspan.
This turns out to be 190% on four A3 sheets.

Physical work done with, comes the dreaming phase, i.e. the Design Phase.

It seems logical to lay the battery flat on the fuselage top, i.e. on top of the top longerons concealed by plastic/card/balsa conical cover. To suit my 2S500mAh batteries, the fuselage has to be widen slightly. It has to be wide enough to seat and strap the battery in placed. This means a new set of formers to be created.

I have experienced one too many dangling battery to have my flight battery unsecured, I shall strap it down by passing a loop of double sided Velcro like strap (or other means, maybe a band of elastic?) through the top longeron position. This means the fuselage has to be wide enough to provide the necessary clearance or else the top cover won't hold.
Meantime, I have to search for this illusive double sided hook strap. If I can't find it, then a loop of elastic band such as those for making clothes should be ok.

Horizontal Crutch

A 1/8" balsa horizontal crutch shall take the place of the two longerons and cross members for simplicity and ease. The top profile of the fuselage, including the bulging nose cowling, shall be drawn onto a 1/8" balsa sheet. A centerline is drawn, the new width marked out and formers position lines drawn perpendicular to the centre line, first to mark out the lower fuselage and then to transfer the lines around the balsa to mark out the top formers positions.

Firewall

 A short length of 10mmx 10mm aluminium angle will be epoxied (hotglue does not work well on ply surfaces) onto the back of a ply firewall and the other flange will be bent opened slightly, ca 3 degrees to provide downthrust. (or closed, depending on 2 things, it's position against the firewall and whether it is mounted to the top or the bottom of the horizontal crutch). The Turnigy motor will be screwed to the plywood with some spacers (because of the motor wires). And then this assembly will be epoxied to the horizontal crutch after the cowling is made and then the motor screwed in. Most likely, the horizontal flange will be epoxied to the undercarriage hard point, and the vertical flange pointing up.

Undercarriage

Fabricate from 3mm aluminium tubing two pieces of axle fixing device. For each piece, start by grinding down on one side of the tubing to approximately 2/3 of the way.
Cut off the tubing piece about 6mm each end from the slotted tubing.
Bend tubing at 90 degrees onto itself, forming a "U" shape.
Coax the slot with needle nose plier so that the two ends are brought in again and forms an omega shape.
Tape, with masking tape, two lengths of 1.5mm piano wire.
Slid an axle fixing device into each wire.
Tape again so that the axle fixing device is in the middle of each wire.
Hold the two lengths of 1.5mm piano wire in a plier and bend them to a 'U' shape.
Unbend the 'U' to the angles shown on the side view.
Tape the pairs of free ends, using masking tape, with one edge at the point where the next bend shall occur.
Slit the tape between the two wires so that the wires separate but each has a tape marking on each end.
With the side jaw of the plier at tape's edge, bend the ends at ninety degrees.
Cut off excess wire from the ends, leaving 1/4" which is sufficient and remove all tape.
Unbend the ends to the angles shown on the front view.
The two wires should be more or less symmetrical and the legs are slightly longer, which is more or less correct given that the splaying out requires slightly longer legs in the first place.
Other wire pieces are then bent and cut to shape.
The two top separator pieces is soldered and the remaining is soldered during the final assembly stage.
An alternative is to use heat shrink tubing, it ought to be sufficient though not as robust.

Lower Fuselage

Make the undercarriage hard point and ply doubler from 2mm ply.
The width of the ply doubler is 1/4" smaller than the horizontal crutch to accommodate the foremost formers.
Two lengths of 3mm aluminium tubing to the width of the ply doubler is bound and epoxied in placed to receive the undercarriage primary wires.
Offer the undercarriage primary wires to the tubing before the tubing is epoxied in place.
Two servos (rudder and elevator) is glued after the rear tubing. Leave to one side.

The dimensions of the formers for the lower fuselage shall be measured against both the horizontal crutch and the side view of the plan and drawn onto 1/16" balsa sheet. The formers to be glued perpendicular to the horizontal crutch.
For the foremost formers along the ply doubler, they are constructed of 1/8" square strips and made into triangles (an inverted "A"). These A frames are necessary to accommodate the ESC, receiver and various wires.

The lower fuselage is nearly completed after the single bottom longeron is glued to the apex of each triangle and the assembly sanded down.

Glue the two pieces of paper/cardboard to the lower fuselage. To reinforce the servo spindle output hole, paper reinforcing rings are affixed on the inside of the rear paper/cardboard. Trim the paper/cardboard, locate the holes for the undercarriage primary wires and the lower fuselage is complete.

Upper Fuselage

Check that the position lines of the formers are complete on the horizontal crutch of the lower fuselage.

Prepare a set of the rear formers for the rear turtle deck from 1/16" sheet, mark the stringers position.
Glue the first former to the rear of the cockpit opening perpendicularly to the lower fuselage.

To make the removable battery hatch, either,

• make a set of front formers with side rails and tack glue the assembly in position, cover it with pieces of paper/cardboard, slit it free and install locating magnets to secure in position, or
• to pull a pvc sheet to shape with a male mould from blue foam, and install locating magnets.

 In either of the above, a former at the king post position has to be glued to the hatch.

Glue the remaining rear formers perpendicularly on the horizontal crutch and then the 5 stringers. Sand down, and the turtle deck is complete.
Epoxy the firewall assembly to the ply doubler and the entire fuselage is ready for covering.

Perhaps a pvc sheet can be pulled over a mould to form the front cowl and deck? The resulting one piece plastic will be easy to place and replace in the field while changing batteries. Concerns are at the front where the plastic has to be pulled tightly, the pinched area where the cowl meets the deck and the lowered decking where it meets the rear turtledeck.

An alternative is to shape front cowl from blue foam, and pre-printed paper for front decking.

Covering the Fuselage

The fuselage is covered with pieces of tracing paper, except for the removable battery hatch which is ready to receive finish.
Dissolve white foam with thinner and apply solution to fuselage to prepare the balsa, paper/cardboard, tissue surfaces.
Spray the fuselage with colour of cream (slight yellowish white?).
Paint in the wooden features, i.e. the exposed balsa and paper/cardboard and the cockpit area, including the back rest.
The battery hatch may be finished with shiny silver/aluminium vinyl sheet or sprayed silver. King post glued on after painting at the final assembly stage.

Wing and Tail Feathers

Wings maybe built up from balsa or cut and sanded from compressed foam sheet.
Wings may be of 1/16" ribs, twin 1/8" balsa spars if 3/4 depth (to have unobstructed top surface), 1/8" trailing edge, 1/4" leading edge, 1/8" wing tips.
A more involved built up:

• Ribs may be separated into upper and lower ribs, lower ribs being 1/16" sq, upper ribs being lamination of two 1/16" sq. In this case, the trailing edge would be either 1/16" or 3/16" thick, depending how the laminated rib is glued on to the trailing edge and lower rib. The wing tips follow the same thickness. Taper the strip or tips to 1/16" before use. There is no spar to obstruct the top and bottom surfaces.

Add the aileron servos, lead the servos wire to the centre of the wing.
Cover wing with tracing paper, I may use glue stick or UHU glue.
Seal the tracing paper with the solution of white foam and thinner.
Spray the wing with the same colour as the fuselage.
Add post-shading details.
Install horns and linkages.
The wing is not removable, it is glued to the fuselage.

The horizontal stabilizer and elevators is constructed out of balsa and carbon fibre rods.

• My carbon rod is ca 2.5mm, I will use it as the hinge edge (and trailing edge) on the fixed stabilizer and a small length as torque rod to the horizontal elevators.
• The leading edges, sides and trailing edges could be made from 1/16"x1/4", but I think I will make them from 1/8"x1/4" strips, with each strip planed to a tapered section before use. 
• The internal cross struts to be 1/8"x1/8" strips (could use 1/16"x1/8").
• The leading edge of elevators to be 1/8"x1/4", slotted for torque joiner.
• Pin the span-wise elements (spars, hinge, leading edge of elevators, trailing edge) on the plan. Cut the chord-wise elements and glue to the span-wise elements. Align the leading edges, trim the span-wise elements and glue to the span-wise elements. Glue the diagonal elements. Remove from plan, cut the centre piece out of the trailing edge, and trim all edges.
• Hinging will have to be figure 8 threading after covering but before painting.

The vertical stabilizer and rudder is constructed out of balsa.

• The same size of strips as the horizontal stabilizer to be used for the leading edge, sides and trailing edge; either 1/16" x 1/4" or 1/8" x 1/4".

Follow the same covering, sealing and painting process.
Glue the vertical fin perpendicular to the horizontal stabilizer.
The tail is not removable, it is glued to the fuselage.
Install horns and linkages.

Final Assembly

Glue the ESC to the underside of the ply doubler in the open framed structure.
Connect up the receiver and stow it in the paper/cardboard covered A frame space to the rear of the ESC.
Spring open the undercarriage to guide it over the tubing holes, release and solder the remaining wires.
Solder the inner retaining washers, slide the wheels in, solder the external retaining washers.
Make up and glue the landing gear struts to the undercarriage wires.
Screw the motor in place.
Slit an aperture on the battery hatch at the king post position, insert the finished King Post from the insider of the hatch and glue the King Post to the balsa former.
Tack glue the fake rigging wires, they will probably be ripped off in flight and handling anyway.

How I did mine, two at a time

I am doing two at a time because although it will take a bit longer, the time taken will not be twice as long, I get more practice, the additional airframe can either be a spare or a gift.

Horizontal Crutch, lower fuselage and upper fuselage

I have found some thin double-sided hook&loop strips and they should not require widening of the fuselage if used for battery strap. These straps will not require slots in the horizontal crutch, a dab of hot glue should be ok for the light battery and so much the better for doing less.

Measured from plan, the fuselage is ca 1.5".
I cut a 2mm ply sheet to 1.5" wide for the ply doublers to the two models, and from two 18"x2"x1/8" wide balsa sheets, the horizontal crutch for the two models.

A technical protractor set square was put to good use to mark the perpendicular lines (position lines of formers) and the 2 degrees firewall offset on the lower side of the ply doubler and both sides of the horizontal crutch. It is not necessary to mark all the lower lines on the horizontal crutch because any lines on the forward half will be covered by ply doubler.

The plan view of the model was marked on the top side and the horizontal crutch cut out.

White glue was spread thinly to the mating surfaces of both ply and balsa and with spring clamps (clothes peg), they were adjusted to final positions and left aside to dry. Both ply reinforced horizontal crutch were glued one after the other, but clamped together to dry, since they were identical. The top sides mated each other.

Offcuts from the balsa sheets for the horizontal crutch were ideal for the pair of formers at the front cowling position. These were cut out with 2 degrees right thrust and glued to the balsa crutches. They were cut into triangular shapes without the front cowling radius, as they shall be finally sanded to the correct shape after the nose ring former is glued in placed.

Progress photograph:

The position lines for formers indicates the front of the formers. There is no position line for former 9B, the rear if the last former would simply be placed along the end of the horizontal crutch.

Undercarriage

I bent the undercarriage primary wires from what piano wire I had. The chosen wire was a bit thicker than 1/16" and closer to 2mm. The pair of U-shaped wires that I bent were identical in shape, but the wire was too strong for my plier cutter. I couldn't cut the wire, so they were abandoned because I think it would be easier (for me with existing tools) if I cut them from 1mm or less wires. 1mm is too thin, but I think they can be made functional and durable if I stiffen the undercarriage by heat shrinking over carbon, ply or even balsa strips.

Horizontal Stabilizer and Elevators

• Start with taping span-wise, scotch tape over the plan, covering the gluing areas. With the plan prepared, position over cork board.
• Pin two lengths of 2.5mm carbon rods over the plan. These are the hinge edges.
• Pin a single 1/8" x 1/4", over-length, over the trailing edges of the elevators. The centre piece will be cut out later to have 2 elevator halves.
• Turning towards the leading edges, trim a slot from 1/8" x 1/4" to receive the carbon rods. Match the angle where the leading edge joins the trailing edge of the elevators. Glue and pin over plan.
• Trim the two 1/8" square spars to fit the leading edges. Glue and pin over plan.
• Fit the remaining elevator edges, the lengthwise and diagonal braces. Glue and pin over plan.
• When the glue has dried, lift the resulting triangle shaped tail feathers from plan.

Wing

From a 4" wide 1/16" balsa sheet, I drew parallel lines 3mm apart, cut them to lengths for the top ribs and the bottom ribs.
I drew a datum line and marked where the leading edge begins and trailing edge ends and the top curvature of the airfoil on end of a thin ply that is longer than the wing's chord.
I snipped the template to approximate shape and sanded the template.
My leading edge is a piece of 1/8" x 1/4" and a 1/8" x 1/8",  arranged as an angle.
My trailing edge is a piece of hard 1/8" x 1/4".
My wing tips is made from 1/16" balsa.
The top ribs are sliced from the 1/16" prelined sheet balsa.
The trailing edge end of the top rib is further sliced along the line so that it may seat flatly.
The bottom ribs are simple 1/8" x 1/16" sliced from the other 1/16" prelined sheet balsa.
Assemble and CA LE, TE, tips and bottom ribs over plan.
CA the top ribs at the leading edge first.
Slice (chop) the trailing ends so that the top ribs seat onto the bottom ribs and TE and CA in place.
(My CA is very watery and does not stick instantly. Even though my joints are fairly tight, I think thicker viscosity would help because excess CA spreads too quickly to the underside of the pieces that I am gluing to. I think my CA may be stale because it doesn't set fast enough, even with CA accelerator applied.)

Next is to make up the dihedral, I think a single 1mm balsa sheet between the two spars is good enough. Crack the sheet at the dihedral and douse with CA. In the end I used 1.5mm bass sheet wood.

Finishing ideas

Print A4 sheets on the office copier in the following colours:

• Cream
• Aluminium
• Wood brown
• Rust brown
• might as well try drab, beige, khaki, buff or various different shades of cream, wood brown and rust brown, or even patterned type.

The conical covering of wheels
E.g. if height is 10mm, and the radius is 30mm, the compass should be set to square root (10square+30square), which is 31.62mm.

Wheel making
To make a single wheel:
Cut out single disc from thin ply (thick ply is difficult to cut with the compass cutter. Probably I cannot cut out the disc just using the compass cutter, so I shall use my snips/scissors to trim the ply disc.
Cut out two disc from 1/8" balsa, similar fashion.
Source or fabricate two large flat washer, with inner hole the size of my aluminium tubing. Washers need not be round.
If the wheel axle is too thin and I find the wheel too wobbly, then insert sleeves of plastic tubing. No tubing? Roll up paper tubes.
Use a jig to glue the washer disc, balsa facings and ply core together.
This jig is just a flat surface with a length of wire sticking out perpendicularly.
Spray the wheel assembly black.
Using compass cutter, cut out a disc from cream printed paper, to the radius where the supposedly tyre begins.
The conical covering is similarly cut out after the radius is determined.

What do I want to try next?

I am bored. The last excitement I had was the first flights of FMS FW190, which wasn't much after the torque is compensated by ailerons trim and a GWS 8x6 DD prop swap.

I shouldn't be building anymore planes.
With so many models flyable (or only requiring slight repairs/replacement and giving the Fokker Triplane to a new home), I shouldn't be building.
Would I be flying more often if I have a model that I like to fly repeatedly? And so much so that I shall not buy, build or fly another model?

This model shall:

• Use existing motors, esc, propellers, prop savers/adapters, servos and receiver which I have a lot of.
• Be interesting either in looks or flyability or difference.
• Be durable (crashable).
• Be quick (and simple) to build, finish and install.

Blackburn Monoplane: 1912 flyer with rounded top triangular bottom fuselage. This may be the ideal tissue cover balsa sticks with papier mache/ plastic moulding top and built up wings and tails? I think wing warping is too complicated and ailerons so far off, so it would be a rudder elevator throttle model. The wing planform might have to be simplified, then again, maybe not as it is distinct. Ought to be ideal for low wind condition (hardly any here). The attraction is to fly slow and low, and that means to build light because low mass promotes survivability.

Caproni Stipa: Novel ducted fan from the 1930's. Rolled up foam board with removable top. Internal ply structure for motor, esc, battery, 2 servos and landing gear. How will it fly? Colourful and full of character. Not so good chance to survive crashes.

Comper Swift: Lightplane from the 1930's. Popular with British modellers, especially for rubber free-flight and is known to be a good beginner flyer. The real plane's wing has no dihedral, so it is simple to construct although if following Veron's 18", the fuselage looks like a lot of strip wood, could be simplified to use 1/16" balsa sheet, but the struts is mandatory as the wing seat is narrow. Can add details like the Pobjoy engine or that depicted in Veron's 18". Colourful and full of character. Good chance of surviving crashes.

Flying Flea: This would be my second attempt. I can salvage the wings and maybe the tail from the first Flying Flea. Maybe a simple flat profile fuselage from 1" blue foam with cutouts for my equipment, but must have rigging wires. Can I make it fly (variable incidence wing design)? Good chance of surviving crashes.

Rockwell OV10A Bronco: I've not have a twin before. Can be made durable because the layout is simple and the wing has no dihedral (not only is it easier to construct the wing, the booms are easier too). The bulbous canopy would be an interesting challenge. Can be built simply with either foam or balsa and it has simple colour scheme and sufficient equipment space. Good chance of surviving crashes except for the high tail.

The Wittman DFA aka Little Bonzo is a homebuilt racing aircraft designed to compete in midget racing in the 1950's. Rectangular shoulder wing and no dihedral, flat sided fuselage and windscreen, so it is simple to construct. All yellow except for blue spinner and landing gear. The full size spans 15'4", so if the model spans 25.x", it is ca 1/7 scale, can add details in the cockpit! Flying should also be good with the low aspect ratio wing. Good chance of surviving crashes.

Sopwith Pup: Beautiful British biplane but too much work and least chance of surviving crashes.

Savoia S13: Schneider Trophy Racer, rise off grass? More struts than the Sopwith Pub. Least chance to survive crashes especially the motor which is mounted below top wing which would rip off the entire top wing.

Techone Sbach 342 -1100, Update 1

Update 1, 4 March 2014

I had trouble on Sunday, 2 March 2014.
I had new Turnigy 3S2200mAh, 60C lipo and crashed in the morning from a failed hover. Motor mount snapped, broke the propeller, enlarged the spar hole in the central spar box, rudder hinge torn.
Went home, fixed it up with hot glue, flew again in the afternoon.
This time I fixed up Eagletree Guardian.
Barely 2 batteries later, lost a servo horn screw (aileron's), hard landing, motor mount loose again, undercarriage needs glue, to perhaps replace one aileron servo.
Maybe I didn't setup the eagletree guardian properly, because it didn't seem to work in the air.

16 February 2014

How it all started

Chris is the one at fault for telling me last Saturday that he would like the TechOne Sbach.



Why is the 11"x5.5" propellor on mine a different colour from the box?
Could this be the reason that I can't fly the Sbach with my set of 3S1300mAh 20C batteries?

15-16 February 2014

Last Saturday, 15 Feb 2014, I rode my motorbike to Rotor to buy ca kicker and 2 digital servos (Hitec HS-A5076HB Digital Slim Programmable Servo Motor (Karbonite Gear) [Torque at 4.8/6V - 2.5kg.cm/3.0kg.cm][Speed at 4.8/6V - 0.14sec/60° / 0.11sec/60°][Bearing - Top Ball Brg][Dimensions(HxWxL) - 27.6x10.8x29mm] [Weight - 14.3g][For Park Flying Models, Indoor planes, Small Glider, Micro Heli, MAV]to replace those of my Techone Katana (the blue one)).

So far I have bought five Techone models. The first was a Su-31 (from Rotor, subsequently given to Wong and he must have destroyed it completely) and two Katana (from Jet Hobby, after destroying the red I got the blue but the fuselage carbon reinforcement aft of trailing edge must have snapped after a crash because of damaged Hitec HS-65HB Mighty Feather Servo Motor (Karbonite Gear) [Torque at 4.8/6V - 1.6kg.cm/1.9kg.cm] [Speed at 4.8/6V - 0.14sec/60°/ 0.11sec/60°] [Bearing - Top Ball Brg] [Dimensions(HxWxL) - 23x11x24mm] [Weight - 11.1g] [For Micro Helicopters, Electric park flyers, Gliders, and 1/18 scale cars use]), both types are 1000mm wingspan and all flew well and the final two are Mini-Popwings. I liked the Katana better but I think that the Swift, being larger, will be much better.

I was thinking of buying a Techone Swift, wingspan of 1200mm. I think it will fly better because it is much bigger.

It is safe to say I trust TechOne.

Rotor had an assembled Sbach, all needed was plugging in a receiver and battery. The price was good, since the kit itself was listed as $153 and the assembled Sbach had 4 (Hitec HS-81 Standard Micro Servo Motor (Nylon Gear) [Torque at 4.8/6V - 2.6kg.cm/3.0kg.cm] [Speed at 4.8/6V - 0.11sec/60° / 0.09sec/60°] [Bearing - None] [Dimensions(HxWxL) - 30x12x29mm] [Weight - 16.4g] [For smaller Airplane, Glider or Heli]), 40A Flycolor ESC and two 12" servo extension lead.

So I bought it and had to return home to drive out again to bring it home.

On Sunday, 16 February 2014, after  some re-routing one servo extension, I plugged in my receiver and battery and got the ESC to respond.

First flight was on my 3S1300mAh 20C battery. My set of batteries is quite old, because they were used in the Su-31 and the two Katanas. I had my Hobbyking X1 Wattmeter and it was drawing ca 27amps, ca 330watts and considerable voltage drop. Well, 27amp divide by 20 is 1350mah, at the limit of the battery. The model has great potential in flight, but it only lasted ca 3 minutes when the model loses power. On retrieval, the motor was warm, and the battery too warm.

Wong loan me his almost new 3S1500mAh 25C (Zippy?), and it was ca 5 minutes and battery still too warm.

Freddy loan me his old 3S1800mAh 25C and it was ca 7 minutes and battery still too warm. I shall have to check with him if his battery is still chargeable.

Battery Consideration

Come to think of it, that's about right! 27amp divide by 20 is 1350mah. 60 minutes divide by 20 is 3 minutes while the actual flight was a bit longer than 3 minutes (excluding maybe 20 seconds for Wattmeter full throttle testing). If I get 5 minutes for 1500mAh and 7 minutes for 1800mAh, I shall perhaps have 8.5 minutes for 2200mAh.

But having too warm a battery cautioned me that I ought to buy better discharge rated batteries. And while I am at it, bigger capacity too.

The Sbach listed 3S1800mAh (to 2200mAh) 25C as suitable battery. I chose 2200mAh, even though it pains somewhat to add weight to the model and found on HobbyKing, Turnigy Heavy Duty of 60C with listed price just below USD 20.00 before shipping. This is priced better than the 35C battery at SGD 38.00 from Rotor.

For a 2200mAh battery, divide by the amperage drawn, 27amp divide by 2.2Amp, equals ca 12C. Yes, the recommendation of 25C is probably suitable for 1800mAh, but unnecessary for 2200mAh. So if I use 3S2200mAh 60C batteries, they ought to be long lasting (my definition of long lasting is 300 flights per battery, because my 2S500mAh batteries have to be replaced after 25-50 flights).

With the latest HobbyKing order of five Turnigy Heavy Duty 3S2200mAh 60C batteries, I also ordered a low voltage alarm (and Eagletree Guardian, but that is beside the point).

With the aim of achieving 300 flights per battery, I promise to look after my batteries better, new or old, by adopting this practice:

In the field

• using the low voltage alarm in the Sbach;
• not flying to less than 11.1v for 3S and 7.4v for 2S;
• to discharge unflown batteries at end of flying day unless the next flying day is the next day

Back home

• to bring all batteries to storage voltage, until the day/night before flying day;
• to balance charge the batteries the day/night before flying day.

Flying time of Sbach

Using 2200mAh batteries that ran cool does not solve the flying time issue I have.
I think 8.5 minutes is too short for my practice flights, I would like 10 minutes (or is that wishful thinking?).
To extend flight time, (not by flying gently or at low throttle throughout the entire flight), how shall I reduce the amp draw and still be happy?

First thought that came to mind is the propeller.
To fly 10 minutes, the amp draw has to reduce to, 27amp/10*8.5, 23amps. The battery discharge rate will be closer to 10C now and might help somewhat to their lifespan.
I shall try different makes, type, diameter and pitch of propellers and static test them with the X1 wattmeter.
Hence the leading question of "Why is the 11"x5.5" propellor on mine a different colour from the box?".

Stunter 32

From the pair of 16" long and 5" wide foam core, perhaps?

5mm depron ailerons, 1/8" braced balsa tail, 4 x 9g servos, landing gear from P51, minimum 7" propeller.

Options for fuselage:

• 1" blue foam (heavy, profile like)
• 5mm depron keel with doublers and reinforced with tape (profile)
• 1/16" balsa sides with 1/8" doublers, framed with formers
• Folded 5mm depron sides over 2 planform pieces
• 5mm depron keel, left and right formers, balsa stringers or planked with depron

Tian Sheng Tailless; Two went up a tree; Tian Sheng Canard

Update 17 February 2014

Yes, both Mini Popwing (Orange) and the HobbyKing Mini DLG were returned to me on Saturday, 15 February 2014.
2 batteries overdischarged and are dead, but the models live on.

Together with the returned models is TianSheng Canard. I didn't trim the foreplane incidence and relied on elevons. It glides, but it is not a floater in this configuration, yaw stability appears insufficient and it is pitch sensitive.

If I trimmed the foreplane incidence of the Tian Sheng Canard, it ought to fly much better. Perhaps one central carbon fibre rod (adjustable) from centre of foreplane to front tip of fin will do the trick, allowing the reflex to be omitted and make it fly more efficiently.

Update 12 February 2014

According to Mr Wong, someone retrieved the models and he himself will pass me the Mini Popwing, Orange, this Saturday.

8, 9 February 2014

What an eventful weekend. I flew my Gee Bee Sportster on 3S (does not help with the fact that what I really need is a lighter wing loading), test flew the Tian Sheng Tailless, repaired and flew the Mini DLG, hung the Mini DLG and its rescuer, Orange, up on the same tree and converted Tian Sheng Tailless to Tian Sheng Canard, and received a pair of foam wing core.

I flew my Tian Sheng Tailless which was made from a Tian Sheng chuck glider and learned that:
1) it needs a much bigger vertical stabiliser; and
2) not to use 1/32" quarter grain balsa for stabiliser.

The CG is difficult to place. I made a slot on the top because with my original intention of having the 350mah battery inside the canopy, the CG was near about the leading edge. With the battery placed all the back to the fin, the plane first stalls and then tuck itself in. After many tries and getting the same result, I had to moved the CG forward along the slot and used massive up elevons. It flew in a fashion but is no good at all if its flying direction wanders slightly away from the wind when it goes into spiral dives. That's how I got to know about quartergrain being unsuitable and it needs a much bigger tail and tail moment to point it into the wind. As it is, the model is too unstable and control too sensitive.

On Sunday, I was exploring lift off the small slope (ca 2m high) behind the row of trees when my Mini DLG got stuck up high on a tree.

An hour or so later, I sent Orange, the lucky Mini Popwing which was returned to me, to fetch it and Orange went off to keep the Mini DLG company.

Each on a different branch of the same tree.

I had to do a lot of improvising to recover the 2 models. I used rafia string tied to a half empty bottle of water and had that bottled water stuck in the same tree. I did a lot of 'shotputting' too. It resulted in one of the best sleep I had in recent months. As of 10 Feb, the 2 models (with a water bottle hanging around) are probably still up there.

On Sunday afternoon, I made a canard out of the Tian Sheng Tailless. Original stabiliser and fin from the Tian Sheng chuck glider was used.

 I shall do some test flying this coming weekend.

There is this guy who gave me a pair of 16"x ca 5" hotwire cut foam core.
The airfoil is symmetrical, need perhaps 1/4" balsa to do up the leading edge and sub-trailing edge (I am thicking of 5mm thick compressed foam for ailerons/ elevons/elevator). Shall I make a longer wing, arrange the pair as a biplane or maybe even a tandem?

Using 1S lipo cell with or without voltage booster for DLG or similar application with Minima receivers, UPDATE 1

UPDATE 1, 4 March 2014

My Tiansheng Wing/Carnard works without voltage booster.

When the single cell voltage booster I bought from Hobbyking broke a wire, I plug the battery directly into the Minima in my Mini DLG, and it works.

I won't be using voltage booster anytime soon.

 

31 January 2014

I found on 29 January 2014 that a Minima works on 1 cell lipo without voltage booster, and so does the servos. Maybe I will have problems while in the air, only experiment and experience will tell.

I have 3 numbers of 350mAh 1S lipo which were for a Walkera helicopter.
I trim the connector by cutting off the lug/tab nearest the black wire and it can be plugged directly into a Minima.
A Minima receiver has 6 channels.
All the channels share the same + and -.
Battery plugged into a channel (not necessary Channel 6) will provide power to the receiver and the servos.
I then plugged in 2 Kingmax 3.2g servos and it works ok indoors.
I shall do a range check in the field.

If noseweight is required or if 350mAh is insufficient, I can double the battery capacity by plugging another lipo to another unused channel.
This will give me 700mAh with increased weight in the nose (or elsewhere).

This would not be possible if I use a voltage booster.
If the range and servos work for the model, I will not use voltage booster.
If there is a problem in the air or the range is not enough, then I will add a voltage booster to bring the voltage to 5V.
If the battery's capacity and/or voltage is insufficient, then I could use a larger 1S lipo and/or a voltage booster.
If multiple lipos are used, then they have to be of the same voltage, with or without voltage boosters. I think capacity can vary but I would think that preferably they are identical in all aspects, to have the same voltage throughout otherwise discharging among cells can occur.

Did some surfing on 31 Jan and found a thread on 1s without booster.
It has been done for years.

Boeing Bird of Prey

Spencer said he modelled the Boeing BOP and it was a failure. There was insufficient yaw stability. He wanted to try again and asked us to join in. Each produces his version and lets see whose gets to fly.

 

First off, it looks ugly. This is how I might do it.

Fuselage

This component will provide lift and house all RC gear and a Turnigy 1811 motor will be mounted as a pusher, driving a GWS 5"x3" tractor prop.
This will be constructed of a rectangular piece of blue foam: 28" x 5" x1" thick. Hot wire cut the section. Sand to shape, cut the slots, pockets or grooves.
Motor is mounted on 2mm ply, secured with nylon tie (don't intend to do any thrust adjustment), epoxied to a slot in the rear of the fuselage.
The battery, receiver, esc are mounted as far forward as possible and side by side if the wires are long enough.

Wing

A rectangular wing, acting more as a stabiliser, to be shaped and cut from 3mm balsa sheet or 5mm compressed foam (which then has to be suitably stiffened). Length of 30", chord of 3". Hinge the elevons, make score lines for the wing tips and fix that to 90 degrees. Cut out a V-piece from the inboard section and join the two wings into a swept back wing with dihedral.
Connect up to the 2 elevon servos in the fuselage, use wire in plastic tube.

Choosing a power system

I like this from Himax:

Choosing a power system:

Power system can be chosen based on the type of flying expected of the model and all up weight of the aircraft. Sedate flying from a hand launch requires 35 watts per pound (W/Lb). Taking off the ground needs approximately 50 W/Lb. Aerobatics and good climb performance, 75W/Lb. Anything more than 75W/Lb will result in excellent performance. Based on the weight of the model and the flying desired, the power required can be calculated. Select the voltage of the battery being used. It is best to use a loaded voltage of about 90% nominal. Now, calculate the current required. From the chart, pick a motor at the voltage you intend to use and find the prop that pull the required current.

Except, none of the motors I have, comes with its chart or the information about A and propeller size, and I don't have a wattmeter to test out the current draw on the propellers I use.

28/1/2014: Well, got to start somewhere, so I placed order for a Hobbyking's X1 Wattmeter

This from Hobbyking's website, much higher W/Lb is recommended:

A basic guide to Electric Flight

An under-powered model is a disaster waiting to happen, here is a rough guide to choosing the electric power train needed for various model types, bear in mind that over-powering is fine but the penalty is additional weight, and a good model is one that is balanced in terms of power, flying weight and build quality. This guide is as the title says, a ROUGH guide and offers a basis from which to choose a power train for your model, it is not intended to be a definative guide but will help to get you into the air with performance that will make your introduction to electric flight enjoyable and reliable.

 

MOTOR POWER CHOICE(base on reccomended AUW, or Flying Weight of model choice):

Vintage types and many non-aerobatic indoor flyers -

50w~70w per 1lb

Trainers, gliders and high wing scale -

70w~100w per 1lb

Sport flyer with general aerobatic performance -

100w per 1lb

Warbirds -

120w~150w per 1lb

Multi engined models -

100w per 1lb (thrust from Multiple props gives in effect, more than 100w per 1lb performance)

EDF Jets -

150w~200w per 1lb

3D, F3A and high performance Models -

150w~200w per 1lb

 

LIPOLY VOLTAGE CHOICE

Based on the above, we now need to work out what voltage we are going to need to use, generally, to keep Lipo's in good order, try and keep max amps to around 50~60% of the capacity/C rating of the Lipoly Pack, for example, if you purchase a 2200mAh 20c pack, then it is rated for 44A constant discharge, so keep the max amps at around 20A~25A IF possible, it isn't always! Choose the capacity of pack based on reccomendation for the model by model manufacturer and in conjunction with the size/weight data published with all our advertised Lipoly packs, for low powered models, choose 20c packs, for general flying choose 20c~25c packs, for high performance models 30c + packs;

 

Up to 50w:

1s~2s

up to 100w:

2s~3s

100w Up to 500w

: 3s (This is the practical upper limit for 3s Lipo's, so basically, models of 5lb AUW)

500w up to 800w:

4s (This is the 0.40~0.46 glow equivalent range favoured by many club flyers)

800w up to 1000w: 5s

• 900w up to 1500w: 6s (this is the 0.60~0.90 ic equivalent range)

8s~10s packs are for very large and generally specialised models.

 

 

MOTOR CHOICE - KV or RPM per volt

Which actually means, what prop size! If you are used to IC, the simple analogy is to treat low kv motors as 4 stroke engine equivalents and mid-high kv motors as 2 stroke engine equivalents, if you are not used to IC then we can give you some examples of the approach to take, this is an important choice as you can literally choose how your model flies, however, their are practical considerations, the most obvious is ground clearance. Please refer to motors such as the NTM range, which give you prop data as well as power, dimension and weight data.

Example 1:

Trainer/Sport Model, 1lb AUW, we want 100w motor (3s 20c Lipoly) mid kv for general flying, probably around 1200kv~1400kv, so around 8" prop

Example2:

3D/F3A Model, 1lb AUW, we want 150w motor (3s 20c~30c Lipoly) low kv, 1000kv or under, spinning 10~11" prop, highly efficient at low throttle openings giving lot's of prop wash over control surfaces at all times, high thrust for low rpm and low amps draw at higher throttle openings.

Example 3:

Warbird/scale Model, 1lb AUW 120w motor, kv choice, either of the above, it is personal choice

Example 4:

High Speed Delta type model, 1lb AUW, 200w motor (3s 25c~30c Lipoly) 2200kv~3200kv motor, 5"~6" Prop, high speed/low torque, low thrust at low throttle openings, high speed from high rpm at full throttle.

 

 

FINALLY, ESC CHOICE

You have decided on your motor, so look at the MAX AMPS figure given by the motor manufacturer in the data section and generally add 25% headroom, so, if a motor is rated to 15A, then choose at least an 18A ESC, better still a 20A and so on. Next make sure that the ESC voltage is compatible, in other words, if you are using a 4s Lipo, that the ESC is rated for 4s voltage. Next, check if it has functions you desire, if you are flying a glider for instance, you will want a brake facillity so that the prop stops when soaring un-powered, allowing the prop to fold by not windmilling, we strongly advise purchasing a programme card to make programming the ESC easier. Also look at BEC rating, the BEC supplies radio reciever power for servo's without the need for a seperate reciever battery, however, the can be limited in the number of servo's they are capable of powering, if the servo count is over 4, as it is on many models these days, then consider purchasing an ESC with a high AMP rated SBEC, or a seperate UBEC, OPTO type ESC's (they have no BEC, keeping the ESC seperate from RX suply) are reccomended for large models that require a seperate reciever power supply, they are also safer in high powered, large models as they will not arm until the RX is switched on.

 

This document is a work-in-progress. Check back regularly as we expand this document.

TURNIGY® Batteries explained

Zippy: Great value for money. Average Cycle Life* (100+) and minimal voltage sag under load.

TURNIGY Standard: Excellent value, Longer Cycle life* (160+) and very low voltage sag under load.

TUNIGY nano-tech: Unbeatable performance, Longest Cycle Life* (250+) and almost 0 voltage sag under load.

*Cycle Life results from discharging at full C rate to 3v. End of life when battery has 80% capacity.

        

And also from HobbyKing's website:

Lithium Polymer (LiPo) Basics
It can sometimes be difficult to know which battery is best for your application.
For R/C aircraft there is a huge variety of batteries available and while many may suit your application your ultimate goal is to purchase a battery pack that will;
-be within your budget
-have a long cycle life
-have the correct size and weight
-give you the longest flight times
-be able to deliver the correct voltage/amp (Power)
We hope this simple guide helps you understand the different types of LiPoly (Lithium Polymer) batteries and which is right for your model.

You may have noticed by now that batteries have different ratings, sizes, plugs, wire, charge rates and chemical makeup. Lets decipher;

Capacity (mAh).
This is usually the biggest number shown on the pack and is measured in mAh (Milliamp/hour) or Ah (Amp/hour). The capacity is the first indicator of the batteries size. To keep things simple, think of capacity (mAh) as the amount of fuel in your cars gas tank. A higher capacity tank will run your car for longer. A 4,000mAh battery will run for twice as long as a 2,000mAh battery.
A 2,000mah battery will (in theory) run for 1hr if drained at a constant 2,000 Milliamps.

Discharge (C)
Discharge is the amount of power the battery can 'push' out and the number shown '20C' is an multiplication of the capacity. For example; A 20C battery can discharge at 20 x 2,000mAh which is 40,000mAh or 40Amps.
This is an important number if you know your motor requires a certain power level.
In addition to this, batteries have a 'Burst' rate, which is the amount of power the battery can discharge for a short period, usually 10-20 seconds. A typical battery label may show 20-30C, this would mean a 1,000mAh battery can discharge 20,000mAh constantly or give a sudden and short 10-20 second 30,000mAh (30A) burst of power.
Tip: A higher 'C' rated battery will last longer if run at a lower 'C' rate. Example: a 30C battery run at 20C maximum will have a longer cycle life than a 20C run at 20C each flight.

Voltage (S)
All lithium Polymer cells in any industry have a nominal voltage of 3.7v per cell. When fully charged a LiPoly cell should be 4.2v and when discharged it should never be below 3v.
You will notice that LiPoly RC packs are made up of layers of multiple cells. If the battery's rating is 3S this means it is 3 x 3.7v which is 11.1v. It has 3 layers of 3.7v each. In other words, its a '3 cell pack'.

Weight/Size
For a battery to be right for your model it must fit within the models battery compartment and also balance the plane correctly.
It's temping to choose the biggest and most powerful battery your model can handle, but this will sacrafice flight performance and if your packs voltage is too high; destroy the ESC or Motor.
Check with your ESC and Motor specification to ensure you have the right voltage pack then check the models CG (Center of Gravity) to decide on the right battery weight.


LiPoly Charging
Always use a lithium Polymer battery charger and never charge the battery above 4.2v per cell. (example: 2S, never above 8.4v)
Never leave a charging battery unattended.
Never allow the battery's voltage to fall below 3.2v per cell. (example: 3S, never below 9.6v)

This document is a work-in-progress. Check back regularly as we expand this document to include battery chemistry, dig deeper into battery technology, battery sales tricks and production methods.

TURNIGY® Batteries explained
Zippy: Great value for money. Average Cycle Life* (100+) and minimal voltage sag under load.
TURNIGY Standard: Excellent value, Longer Cycle life* (160+) and very low voltage sag under load.
TUNIGY nano-tech: Unbeatable performance, Longest Cycle Life* (250+) and almost 0 voltage sag under load.
TUNIGY nano-tech A-SPEC: Competition level cells, strongest voltage hold in the industry.
*Cycle Life results from discharging at full C rate to 3.3v. End of life when battery has 80% capacity.

     

Thrust lines on Pushers

When the propeller's rpm is increased, the thrust is increased and the model will increase its air speed until the increased drag (that is the result of increased air speed) is in equilibrium with the available thrust.

All my models pitch up when air speed is increased (except my 3D model type, whose pitching tendancy are at the least). Downthrust is used to help reduce this pitching tendancy by keeping the nose down, thus when thrust is increased, so is the down thrust component.

The other observation is, when the propellor's rpm is increased, the model rolls to the opposite direction of the propellor's. I understand this to be the same as torque-rolling. It is especially evident when performing rolling from hover. I normally use tractor propellors, turning counter-clockwise. It is easier to allow the model to roll left by releasing both right aileron and rudder which were held when in an hover.

There is a difference though. My 3D planes have hardly any downthrust or right thrust, whereas my ordinary model has varying degrees of downthrust and right thrust. Especially obvious is the Red Triplane that was given to me. It has  ridiculous amount of down and side thrusts.

Even though it works, I don't understand how pointing the thrustline to the right help to balance torque roll. How could doing that create a rolling moment in the other direction?

Without understanding fully, I still like to consider the application on pusher models. If I have the propellor as a pusher, should I introduce thrust line deviations?

There are two possible deviations to the thrust line, whether it points upwards or downwards, and whether it points left or right. To understand the turning moment created by these deviations, the first thing I need to understand is, where is the pivoting point?

Is the pivoting point at:

• the centre of gravity; or
• the centre of drag; or
• the centre of area; or
• a combination of the above?

WBP-1 Flying Plank; modifying Tian Sheng's TS800; RC WBP-1

Introduction

I wanted to build and fly a WBP-1 after I built a 'Red Butterfly'. I tried to chop up Tian Sheng's TS800 but that wasn't successful, the CG, while always there, was difficult to catch. Under the 'History' is, well, history, under 'RC WBP-1', the flyable WBP-1 using lightweight gear.

RC WBP-1

History

I have flown the Red Butterfly. I gave it to Wong and he told me the reason he is not flying it now is because he has to replace his motor.

The Red Butterfly is a 4 channel flying wing. I could do a light and small scale model of some real planes.


A few inspirations from the internet.
The first 3 photos shown here is of the Al Backstrom's WBP-1. A profile rubber scale was offered in Aeromodeller.

Flying wing is long in the tooth.

It can also be sleek looking.

Perhaps I could do a quick-to-built the original white WBP-1, also called the flying plank. RET control, 5mm foam with 2mm carbon rod leading edge glued and taped on, Guardian surgical tape hinge, 1" blue foam pod either with integral canopy or seperate moulded canopy, fixed fins, Turnigy 6A motor and ESC, GWS 5"x3" propellor, 2S 500mah battery, 2 Kingmax 3gm servos embedded in the wing just behind the leading edge for the elevons. Span not exceeding 25" (original is 25'). Below the plans offered in Aeromodeller.

 

Step by Step Construction

1. Begin with the wing. Mark out the wing's outline (25"x5" or 20"x4"), the elevon's hingeline (we will use spanwise strip elevon, not the partial outboard elevons) and the centre line of the wing onto 5mm foam board. This will be the lower surface of the wing.
2. Cut out the single piece wing. The cuts to be perpendicular, at 90 degrees to the board.
3. Glue the 10mm x 0.5mm carbon fibre strip to the top of the underside of the wing. Leave approximately 2mm of the strip exposed from the foam's leading edge. This 2mm ledge is to accept the 3mm carbon fibre rod.
4. Glue the 3mm diameter carbon fibre rod against the foam's leading and carbon fibre strip.
5. Shape the top surface of the foam's leading edge. One way is to sand lightly, another is to depress the foam with a hard and flat object.
6. Big gaps between the foam and rod or the rod and strip may be filleted in. Leave minor gaps alone as it will be taped over.
7. Place the wing assembly upside down to mark out the two servos location. All servos I used has the servo lead at the end where the rotary drive is located. The rotary drive is where the torque will be, so place it close to the leading edge, but no parts of the servo should clash with the carbon fibre strip. I don't cut my servos' mounting lugs, place the servo flat on the wing, rotary drive to the leading edge and facing outboard, mark around the servo including the lug position.
8. Cut out two holes for the servos. Slitting is sufficient to accomodate the servos' mounting lugs. The cuts to be perpendicular, at 90 degrees to the board. Dry fit the servos, do not glue in at this stage.
9. Place the wing upside down on the cutting mat. Orientate the wing vertically so that your master hand can draw the cutting knife towards yourself. I am a right hander, so I position the wing's trailing edge towards the left and the leading edge towards the right and I place my 12" ruler on the elevons.
10. Seperate the elevon strip from the rest of the wing with the cutting blade at approximately 45 degrees, blade resting against the bottom edge of the ruler which is right on the hingeline.
11. Flip over the elevon strip so the two 45 degrees edge cut meets with a 90 degrees  at a continuous point. The resulting V-cut is at the bottom of the wing.
12. Lift up both pieces, flip the elevon strip and place it against the upper surface of the wing so that the 45 degrees edges meet to form a 90 degrees ridge.
13. Apply Guardian's 1" surgical tape over this ridge. This is the underside of the continuous hinge.
14. Cut a rectangular piece of self-adhesive vinyl sticker. The vinyl should be larger than the rectangular wing with hinged elevon strip by about 1".
15. Apply sticker over the top surface of the hinged wing, wrapping around the leading edge.
16. Make the radius corner, cutting the sticker and foam. Trim the sticker.
17. Temporary cover the servos' opening on the underside of the wing to prevent dust and debris from sticking to the exposed sticky side of the vinyl sticker. The wing is placed aside and attention is now directed to the fuselage.
18. The fuselage shall comprise of two parts, an upper part and a lower part. Trace the complete fuselage shape onto 1" blue foam. Mark out also the wing's position and thickness. With a ruler placed on the lower line of the wing, extend the line to the nose of the fuselage. This line indicates the separation between the two parts of the fuselage. The separation line and wing slot lines are transferred over to the other side of the fuselage. There is no need to transfer the fuselage outline.
19. Cut along the fuselage outline.
20. Round the corners, including the canopy, the nose, and the turtledeck. The separation line and the wing's position and thickness should still be visible on both sides.
21. Cut out the wing slot. As the foam is 1" thick, and some accuracy is required, this is not as easy as cutting the 5mm foam. If I have mechanical means, such as a jig saw, I would use it now. Since I don't, I shall use a 6mm drill bit and drill the blue foam with my Ikea screwdriver/drill. Then using a NT cutter with a sawing motion, cut out the slot. The sighting advantage for having both sides having the same lines drawn is now realised. Leave the fuselage to one side and focus on making the motor assembly.
22.  On a piece of 2mm ply, mark out the outline, vertical centre line (not allowing any side thrust), points of the mounting holes, and the centre point of the firewall. The mounting holes shall be positioned in a 't' manner, and the motor wires will pass on either side of the lower part of the 't'.
23. Using a pair of shear, cut out the firewall.
24. Bond this firewall to a piece of 8-10 mm rubber foam. The markings should not be obscured. Trim the rubber foam to the outline shape of the firewall.
25. Drill the ply and rubber foam firewall. Use 3mm drill bit for the mounting holes, 6mm for the motor shaft clearance centre hole. The slot for the motor wires will be dealt with later.
26. Install four 2.5mm blind nuts on the ply side of the firewall.
27. Install the motor mount with four 2.5mm x 12mm long hexagonal bolts. Thread the motor wires and secure the motor on the motor mount with the set screws. Install the prop-saver on the motor shaft and band on the propellor. The motor mount is against the side of the firewall that has the rubber foam.
28. Take out the wing and the fuselage and mark where the firewall will be bonded to. I don't know how much of thrustline deviation to allow for, so it is set initially as zero-zero and flight testing will dictate how much is needed. A line for the firewall position is marked on the top surface of the wing. This is the line along the ply face. The set back required is when there is 10mm clearance measured between the propellor tips and the trailing edge. This clearance is for the compressibility of the rubber foam, the side thrust if necessary, and the forward flexing of the GWS 5"x3" propellor.
29. Slot the fuselage over the wing, if the fuselage is not flush with the trailing edge, lengthen the wing slot by sanding away the portion where the leading edge of the wing meets with the fuselage.
30. Transfer the firewall position line to the fuselage. Remove wing, keep it aside and extend the two ends of the line over and around the top of the fuselage.
31. Cut the fuselage along the transferred line and then the separation line. I now have a top half and a bottom half.
32.  Glue the firewall to the top half of the fuselage, the ply side towards the blue foam and the rubber foam faced motor side towards the rear. Remove motor, but leave the motor mount on and sand the junction of the firewall and top half to remove big bumps.
33. The motor mount is arranged with a pair of its arms vertically and the other, horizontally. There are two diagonally set-screws to hold the motor in placed, If the lower set-screw is on the left, the three motor wires will pass on the right, and vice-versa.
34. Plan and mark out, on the bottom of the fuselage top: the motor wires' route, the pocket to the ESC (whether horizontal, vertical, on edge or any angle in between), the routing to connect to the receiver and the battery. The motor wiring uses 2mm bullet connectors, make it so that the ESC, with its bullet connectors and the plug to the receiver, can be removed. If it is possible to have the receiver located in the fuselage top, so much better. Decision will be based on: having the ESC (and Receiver if possible) as far forward as possible; a neat and direct routing of wiring(even if the wires have to be doubled/tripled back on itself and be located in a pocket or a slot); ESC and receiver to be removable from tight fitting pocket/s or slot/s. It maybe possible that individual pockets can become a larger slot in the fuselage top; so long as it can be covered with vinyl sticker and is not too much out of shape, it is fine. There is not going to be much issue with weakening the fuselage top, leave at least 1/2" length of foam at the rear to provide buttress to the motor and it should be fine. Remember that the servo plugs of the two elevon servos will passed through the wing if the receiver is mounted on top and if the receiver is mounted on the bottom, the ESC plug will pass through the wing. If receiver will be located on the bottom, then a pocket/slot at the bottom fuselage piece will have to be planned.
35. Plan and mark out the vertical slot for the 2S500mah battery. It is located at the nose, as far forward as possible, leaving at least 1/4" foam in the corners and avoid the location of the nose gear. Check that the battery plug of the ESC is long enough; if the plug can be pulled through the slot and has sufficient length to be finger gripped, it is enough. In operation, after plugging in the battery to the ESC, the length of wire is doubled/tripled and stuffed into the slot. If the receiver is to be located at the underside of the wing, then the pocket/slot and groove for the receiver and its wires has to be marked out. 
36. Cut/saw/hollow the fuselage's various pockets, slots and openings. Trial fit of all components, temporary plug in two elevon servos and check that it functions properly. Also check that the motor rotates in correct direction.
37. If optional nose gear is desired, a wheel pocket is hollowed out from the lower fuselage half. The nose gear is built with a rectangle piece of 2mm ply, slotted to accept the wheel. The wheel is inserted into a L-bent wire and another bend locks the wheel in placed. Then the wheel assembly is glued on either to the top or bottom of the ply piece, and the nose gear glued to the fuselage. 
38. From the photographs, there is a single main wheel in the fuselage, but two main wheels are seen in the later photographs. If desired, fabricate the main gear following the steps for the nose gear. And if the twin-wheel main gear is desired, just modify the ply plate into two slots and add a pair of fairings.

Tiansheng TS800

TS800 Specification No motor required
Material: EPO Foam (Crash-resistant)
Length: 490mm
Wingspan: 600mm
Take-off Weight: 62 grams
Discard rear half the tail boom, insert central fin, install RC gear and a flying wing similar to the flying plank results.
Or cut off at trailing edge, install twin fins, motor and RC gear and a power model results.

Yesterday I toyed with the RC gear I have.
I have Kingmax 3.2g servos, Hitec Minima, and from a Walkera helicopter, a 1cell lipo mains charger and 3 numbers of 150mAh 1S lipo.
I googled if it is possible to operate the RC gear with only 1S, turns out it has been done but with larger capacity.
The lipos for the Walkera has a white connector and it cannot be plugged into the Minima.
I thought of soldering on a servo plug to the lipo, but then I noticed that the position of the sleeves is very close to that of the Minima's pins.
I don't know if the sleeves will mate with the pins.
I took one lipo, trim off the lug/tab nearest the black wire and discovered it can be plugged into the Minima.
The Minima was blinking red and green.
So I bind the Minima with my new 9X and it works!
Plugged in 2 Kingmax 3.2g servos, program the 9X and it works out ok.
The nose of the TS800 has a very small cross section, limited space to mount the receiver and battery.
I placed both lipo and Minima together to save space and make the cutting easier and minimal.
The nose of the TS800 is also very short and the 10cm servo plugs is long enough to be routed to the wing.
I need not use extension wires.
At first I thought I could glue on the canopy for strength and cut out grooves in the bottom to access the RC gear, but I think it is neater to have removable canopy.

Holding the airborne RC gear in my hand, I find it very light and compact.
If servo is 3.2g a piece, Minima is 4g, and the 150 mAh lipo is about 12g, total weight is only approximately 22.4g. I think it is perhaps the same weight of the stainless steel ball bearing nose weight that I removed from the canopy of the TS800.

So if the chopped up TS800 with new fin weighs 30g, and my hinges, horns, pushrods and tape weighs 10g, the total flying weight of the flying wing TS800 will be 62.4g, very close to the original TS800!

Some weight might be necessary to add to the model in order that the CG can fall within its allowable range, and this would be determined on the field, but the prospect is good indeed.