DH_1A

3 April 2017

Seems to the right size for pilot/gunner

In better light

Dihedral cheat area

Pose on motorcycle carrier box after 1st successful flight.

Poise and ready

The propeller chopped the trailing edge of the top wing.

1/33 Lewis gun.
Hot glue on tubing and line.
Canister is from 7mm motor back end.

Thang did it in 2 hours for me.

Very light.

Sunday sortie. BD 5, 2 Flybear and a DH.1A.

To toss this model, spread out the hand, hold it by the bottom of the booms, curl on the undercarriage to hold it proper. Very easy!

1st set of test flights was a failure. I tossed 3 times with power on: the first 2 times the model rolled towards right. I trimmed left and on the last time, the model did not roll anymore but did not level up before it reached the ground. By now some struts came loose, so I brought it home for repair. The pull pull lines were elongated too. To tighten the lines, I twirled it around a pin and superglued it to the horns. The loose rudder was tighten up and the control was much better, now it would only be 6mm off centre after left command. Having 4 lines for elevator is good. Even though the lines were loose, there is no loss of control! Each deflection either way is positive since the line is pulling while the other lines were relaxed. Seems I have stumbled on duplicity safety.

I changed the propeller to a 65mm and removed a 10 cents noseweight (only a 10 cents noseweight left in placed). The struts were hotglued and I headed out for the 2nd test flight session. This time, the model flew. It can fly left and right but it doesn't hold the bank for most of the time, so the flight was wavering. Then I heard some chopping noise in the air and I brought down the model. The motor had came loose from the epoxy bed, the 65mm propeller had 'trimmed' some of the trailing edge of the top wing. I had to bring it home. I superglued the motor on the epoxy (must buy UHU POR).

Next morning, I flew it again. At the transmitter I set exponential for Channel 1 (which is master to Channel 4) and had a good flight. The model was handlaunched and it was easy, no dropping of wing, a smooth climb out. It climbed respectfully too, no struggling with getting it going up and poise in the air was nice. The 260mah cell didn't last too long, I didn't time the duration, but I think it was 4-6 minutes before noticeable power drop. The 65mm prop gave the model much needed thrust. The cell showed more than 3.7v.

On the 2nd flight, I almost got the hang of this model but the motor powered down and cut off when it was perhaps 3-4 minutes into a flight. The cell showed more than 3.8v.

For the 3rd flight, it didn't happen. I thought there was an interference issue because the motor didn't spin and I was controlling Mr. Lim's WLToys F959 instead. Weird, so I let Mr. Lim fly his round before attempting my 3rd flight. The model was bound to my transmitter, I have rudder and elevator but the motor still didn't spin. (Incidentally, Mr. Wong's F22 had the same problem when he tried his).

I think the brushed speed control on the board is burnt. Maybe the 65mm is too much for the 8.5mm motor, and when the motor gets hot (motor shrouded by the paper Mercedes engine), the amp draw increased to burn out the fet. I was also flying the Bede-5 which has a 8.5mm motor but on 56mm propeller for maybe 6 flights and there was no problem.

To re-use this damaged board, I think I can connect the signal of the channel 1 and the + and - of the power to a brushless esc. I can swap in a new board but I am still waiting for their arrival and I think it is too much work and not enough fun to swap the board, set the lines etc. Maybe I will just keep the DH.1A as a display and souvenir. I have did what I set out to do: a biplane, pull lines, a pusher and an open boom, this shall be the last entry on this topic.

Ramblings

How to toss this?
Nothing to hold onto behind the wings.
Landing gear obstructs smooth launch if pinched at the nose.
Only ROG and discus launch!?

• Right thumb and forefinger (or forefinger and middle finger) on lower wing tip, swing and let go.
• Right palm up on lower port wing, horizontal chop.
• Right palm down fingers around upper starboard wing near propeller, elbow across chest, elbow chop.
• Left thumb and forefinger on wheel axle ends with palm inwards, right thumb and forefinger pinch bottom of boom near rudder, two hands send off at eye level. Need transmitter strap or launcher.
• Right thumb and forefinger on wheel axle ends with palm outwards, left thumb and forefinger pinch bottom of boom near rudder, two hands overhead send off. Need transmitter strap or launcher.

27 March 2017

Setting the undercarriage.
I cheated by moving it forward.

After rudder is stringed,
the stabilizer is hotglued.
2mm plywood wheels.



Left doesn't return to centre, right returns to centre.



The simplest, lightest pull pull I can think of.



Less than 38gm. With 260mah.



No rigging, no tail skid.



Need radiator grille.



Maybe I will swap the 56mm prop with a 65mm prop.

View of truss booms.



View of the 2 bay biplane.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I threaded heat shrink sleeves to the valley of the 2 V-shaped bamboo pieces, add superglue and shrank the sleeves. Seems very strong.

I threaded a bigger piece of heat shrink to grip the axle bar. A bamboo dowel was held in place so that the heatshrink sleeves can be canted at the correct angle.

I offered one Vee (with the bamboo angle), against the plan's side view to mark where it would enter the pod, then cut it with about 10mm allowance for insertion lengths. The other Vee takes the measurement from the first Vee.

The pod was marked for the exit points of the V legs and a bamboo piece was used to pierce through the pod's bottom at an angle. Hot glue was pumped into the 4 holes, the two Vee held temporary with the horizontal axle, was inserted into the holes. Adjust so that the two Vees are at the same angle and the horizontal dowel is parallel to the wing's leading edge top and front.

I made cuts with my pair of shears on the deck that covers the rudder servo. The line goes into the slit, pass round the mid strut and back to the rudder horn. The rudder horn was made from plastic tubing from a cotton bud.

After the control line for the rudder is installed, I hot glued the horizontal stabilizer to the top of the booms. Then with 2 shorter horns superglued, I installed the control line for the elevators.

I super glued plastic tubing to the plywood wheels, cut the undercarriage axle to length, scraped and sanded the ends so they can slip into tubing, install the wheels with smaller tubing superglued to hold them in placed.

Then it is weighing time, AUW of less than 38gm. 15" wingspan and the full size is 41'. This mean my model is 3% scale, or about 1/33 scale.  Tail skid, rigging, radiator grille, lewis machine gun, wind screens, foot hold are missing. But I think I will do minimal and get it to fly first. CG is about 1/3, maybe some weight will still be necessary, only test flights will tell. Dihedral seems to scale, but if it is not enough for this model, I can add transparent panels to the outerboard wing struts to add dihedral effect and bend the lower wing's trailing edge at the wing tips for washout to correct some roll effect. Control wise, rudder left will bind resulting in rudder held in left position while rudder right and up/down of elevator is fine returning to centre. The prop rotation direction will mean the model will turn right, so it might still be ok even with the sticking left rudder. Still hoping the binding will go away after some time when the coarse spots are improved.

Rambling

CG is too far back at this stage!
I made a pair of wheels. I started by drawing a circle on 2mm ply (CG too far back, so I can afford some weight here), marked the centre, snip to disc with pair of shears, drill the centre holes with a moto-tool and all the holes slipped. Boo.
So I re-started by drilling 2 holes on 2mm ply, bisect the hole with X and Y axis as accurately as I can, draw the circles using a circle template, snipped to discs. Assembled both discs with a bolt, 2 washers and nut, clamped it in my moto-tool, clamped moto-tool to vise, sanded to proper disc with 100 grit and finishing with 240 grit.
Then I thought I could just paint on the tyres. I offered a black pen to the spinning discs, but couldn't get ink on some portion of the discs. I thought it was because the pen is too stiff, so I applied acrylic paint. But it still did not work. There will be splattering but it wasn't successful. I painted the tyres only when I clamped the bolt to an electric screwdriver. The much slower speed allows the painting.
The holes drilled in the 2mm discs are too big for even the bamboo, but if I insert cotton bud tubing, the bamboo are too large to fit in. Since wobbly wheels are not acceptable, I shall install plastic tubing hubs that projects beyond the discs. I could use pins or thin wires as axle.

The initial idea for the undercarriage is to use bamboo. Either 4 straight pieces or 2 pieces of U-shaped.
I tried the U-shaped undercarriage. I soaked a pair of bamboo sticks for about an hour. Clamped a soldering iron to my vice, and heat bent the bamboo with constant re-dipping in water. Both bamboo developed longitudinal splits, regrettably but it should be expected. They are still usable though, I could reinforce the split with heat shrink sleeves and CA. To connect the axle to the main undercarriage, I think I can make use of heat shrink or silicon tubing. I will insert an end of the bamboo from one end of the sleeve/tubing, exit and re-enter at the middle and final exit at the other end, then the sleeve/tubing is snaked to the U bend portion of the bamboo undercarriage (which already has the heat shrink reinforced sleeves in place). The axle can be inserted through the hollow between the U bend and the sleeve/tubing. Silicon should be more bouncy and the sleeve is more compact.

The 2nd idea is to develop from flat plastic, this way the undercarriage does not look wiry. Bended undercarriage from flat plastic means I have to find the right thickness and stiffness first and adding stiffeners are extra steps which leads to inconsistency. So I think I will cut the undercarriage out of a single piece of flat plastic, bend it, pierce holes at the bends, tack glue to pod, insert 4 bamboo pieces.

If I use the U-shaped bamboo, they will be inserted and glued to the pod, separate left and right undercarriage of flat plastic will be glued over them.

23 March 2017

The taped steel ruler is the template for all the struts.
The struts are cut with the pair of snips.

4 cabane struts trial fitted and removed.



Stationery tape and toilet paper were used as mask before spraying primer paint.
Cardboard sprays great, but the foam areas are not good. So I repainted with acrylic.



A whole board was sprayed.
What wasn't visible became highly conspicuous.





Didn't like the patchy brown, so I rubbed green
acrylic with a piece of washing sponge.



Drew the many rib lines
with a colour pen.



Cut to wing shape.



4 roundels on tracing
paper.



Horizontal tail and
elevator.

Glued booms and struts.

Rudder hinged to booms.

I sprayed anti-rust brown on a yellow board and the pod. Didn't like it so I painted over it. Now the board would sometimes seems to be green and sometimes brown.
Measured the dimensions of the wings and marked out on the yellow side, a large rectangular piece with spar lines and key points: centre on leading edge, all 12 struts. Drew extension lines of the rib lines on the plan and place the rectangular piece, painted side up, on the plan so that the extension lines will guide the straight edge in order that rib lines can be drawn over the coloured foam. I used orange colouring pen. I cut out the wing tips out of the plan and pasted them over one set of wing, and stack this set over the other set and cut through both sets at one go.

I didn't want to paint the roundels directly on the foam pieces because I wasn't sure if I will be satisfied with the result, I may want to paint the bottom or repaint the top. I placed tracing paper over the plan, traced the roundels with blue and red colouring pens. The little red central dots is only red colouring pen, but the blue ring is with acrylic hand painted because I don't want to run out of colouring pen. I couldn't decide if I should invert the roundels or maintain it paint side out. Finally, it was decided to be paint side out because that is how the very tail and pod are and I think it is better for the wings to be consistent with the rest of the airframe.

Apply paste to the wings and not the roundels. When applied to the tracing paper roundels, they curled up easily. When applied to the foam wing, I used a small card to swipe inside-out the roundel and had better success in achieving a neater appearance.

The horizontal stabilizer and elevator was done by pasting a tracing that was done over the plan onto the underside of the tail. The horizontal tail was cut to shape. I glued the elevator joiner, which was a short piece of bamboo, to the elevator with superglue before making the hingeline. Then the tracing paper was removed and the rib lines drawn with reference to the wings' riblines. To reinforce the hingeline, small rectangle strips of tracing paper was superglued to the stabilizer and elevator.

I measured the longeron pieces for the booms to be 6.25". So I drew on a piece of paper, a line of 6.25", extend perpendicular lines at the ends to match with the strut and the rudder height, and the 2 intermediate boom uprights. I failed twice with superglue on bamboo before getting it right the third time. The glued pieces broke off easily. Since it is brittle, I glued small pieces of tracing paper to reinforce the bamboo joints. I am glad that I glued the longerons of the booms to the supporting struts. If I didn't do this, I think I will have a frustrating time positioning and gluing the booms after the wings and struts are in placed.

The dihedral to the wings were set with a hot air gun with the wings over a table's edge. Not so accurate, but it was my first try and I think it is good enough.

To set the wings at 3 degrees, the trailing edge has to be packed down about 3mm. I glued a piece of bamboo. Then I realized that the lower wings won't sit perpendicular to the pod! I specifically remembered while slitting the pod that I reminded myself I must have the struts' positions slitted very accurately. So the holes in the bottom wings were elongated and the lower wings glued in placed with superglue.

This was followed by boom supporting struts. I raised the pod and end of the booms for what I imagined to be the right poise. Then the remaining struts were glued in, no jigs or anything, just eyeball judgement and delicate manual adjustments.

After the struts (and booms) were all glued to the lower wings and the glue has set, I put drops of superglue to the struts' holes in the bottom of the upper wings and placed the upper wings over the struts. Only a strut or two may have lined up properly, so I proceeded from one end of the wings, nudging the struts so they sit into the holes, holding them in position with one hand and then proceeding with the next set of struts until I complete all the alignment. In this case, my superglue's slow setting time is useful. My superglue sets supposedly in 5-10secs, but it ended up much longer either because it was stale, or I was heavy handed in my application since I wanted some gap filling too.

I decided that the vertical tail shall have a protrusion pivoting in the holes of flat pieces that are glued to the rear ends of the top and bottom booms. A tracing was pasted, The other side was grooved for the short narrow bamboo pivot. Painted on the tracing side, pasted another piece of tracing paper over the other side of the rudder, and painted. Stationery tape, with reduced stickiness, works well as masking tape. For the pivoting flat plates, I find a piece of plastic, make two holes, trim to identical shape, glue one piece on the booms. Insert rudder, fit the other pivoting plate over the other protrusion, glue the other pivoting plate to the other pair of booms.

Another short piece of bamboo was glued to the top pivoting piece to raise the rear end of the horizontal stabilizer after judging with reference to the top wing.

Rambling

PC 10, what colour is that ("Olive Drab", "Khaki")? Is it green or is it brown? PC 12 is more brown than green. I don't know if DH.1A was in PC 10 or PC 12. Could read more, but why bother.They have to be applied to the top of the wings and tail, and one internet colour rendering suggest that the some parts of the pod too!

I will use yellow foam sheets for the wings and horizontal tail and the vertical fin (I'll use white foam for the rudder because it has to be coloured blue-white-red).
And because I'm me, I am going to consider that the yellow colour is close enough for 'creamed' or 'doped linen'.

What of PC 12 then? I see 2 options:
1) cover with green or brown tissue; or
2) spray paint with the closest colour available in cheap spray cans.

Option 1 has me thinking of glue sticks, and then tissue coming undone, or too heavy coat of adhesive and wrinkles. I like tissue for the consistent finish. But I want the process to be simple and quick and the finished product to be light and durable. I imagine applying white glue on tissue will probably end up not well. The process is simple but it will be longer than option 2. How about spray adhesive? No, because it is expensive, the smell is bad, I may get clumps, it's a one time operation with the tissue and I don't think left over spray adhesive is good for future use.

Option 2 is very appealing and it is lighter. Water-based paints are not suitable for foam surfaces, so I will buy aerosol spray can. Against this idea is the hunt. I have to visit a few stores to find the colour and price that I am happy with.

Or maybe I should just forget it and keep my dh.1A unpainted, at least until it got  flying? By then the struts will be there to obstruct tissue laying, spraying will involve lots of masking and it won't be easy to spray the lower wings. I'll just tell the guys that the particular DH1A I have modeled was a prototype before they decided to paint it.

If I leave it unpainted for now, I can continue to build the model.



I was out for my lunch and on another errand and found this spray can of paint for $3, so I bought it.

I found this spray can of paint for $3, so I bought it. "Anti-Rust Brown", "防锈底漆" which means it is a primer. I will get a whole sheet of the yellow foam sheet, tape and cover one side, place it in a cardboard carton and spray. That will give me a two tone foam sheet. With the carton out, I should also spray the pod.

13 March 2017

Made a new paper template.

Tape template to cardboard and cutout. Pod slitted for cabane struts.



Cardboard cutout wet-formed and dry weight noted.



Here, the decking is glued on, motor is epoxied, dummy engine and radiator block placed.

Larger view of the pod with cabane struts inserted.. 

Two new paper templates were drawn and cut: a decking to fit the pod and a radiator housing. The decking was an adjustment of the first template, I lowered the decking height and extended the aft section. These were taped to a piece of cardboard, in this case, the cover flap of a box of Japanese tea satchets, and cut out. I have side tabs on the decking so that it can be glued securely to the foam pod.

The cabane struts positions were marked on the foam pod and slits were cut into the foam pod. The bamboo struts can be forced flush to the foam pod.

I taped the decking over a round cardboard tube which is about the same width as the pod onto a piece 1" thick foam. Water was applied on the curved portion and the decking was left to dry. When dried, the decking adopted the curved shape required and this was then superglued to the foam pod.

I marked the locations where the front struts will protrude from the decking. This is easy because the struts are perpendicular to the pod, and it is a simple matter to dot the location with reference from the slits at the bottom.

To make the openings on the decking for the front struts, I cut two inverted "T". By pushing the tabs inwards, it forms triangular openings and the cardboard forms around the bamboo struts.

To make the 12 struts, I taped a scrap piece of cardboard to a steel rule at the 58mm mark and use the edge of the cardboard as a stop end for the bamboo strips. The interplane struts were to be about 55mm. I snipped all twelve struts in this way with a pair of shears at the edge of the steel rule. Since I am using a pair of shears and not a cutter, the overall length should increase by a millimeter or two. I think it is ok, greater distance means less interference between wings and better efficiency. I just have to remember to set the booms wider apart and use longer boom struts.

I epoxied the motor with side thrust and then discovered it doesn't work! I had to prise off the motor and epoxy another motor. Thankfully I was able to remove and re-attach the motor plug to the receiver board with fine nosed pliers and a bamboo stick. I should have done a last minute check before gluing on the decking, even though I had tested it before. Boo boo 1.

I noticed the pilot's cockpit opening does not give straight access to the two servo screws. Yes, I have adjusted the cockpit opening "slightly" when making the template. The compromising solution was to cut away a tab and have the radiator block obstructing the view. I should have laced up the servo horns with control lines before I glued on the decking. Boo boo 2.

Rambling thoughts

Setting up booms, rudder, struts, wings:

The 2 booms are required before the wings can be assembled.
Work out the true length of the booms, draw it out on paper, and make two sets of booms.
Temporary glue the front ends of the 2 booms to the correct spread and proceed to do the rudder.

To hinge the all flying rudder, glue 2 short pieces of bamboo to act as pivots to the rudder.
Make 2 bearing surface from aluminum material scrounged from a soft drink can.
Drill the holes first and then cut with a pair of snips.
The aluminum bearing surfaces join together the ends of the two booms by glue.
Slightly spring apart the top and bottom booms to insert the rudder.
Now rig the booms.

Make 2 vertical foam templates for the positioning of boom tubings at the rear inner struts.

Setup: thrustline 0° (to horizontal datum line), tail 0°, therefore wings at 3° for 3° decalage.
Setup: thrustline 0° (effectively -1°, relative to tail line), tail 1°, therefore wings at 4° for 3° decalage.
Setup: thrustline 0° (effectively -3°, relative to tail line), tail 3°, therefore wings at 7° for 3° decalage.

The 2 pairs of centre cabane struts shall be perpendicular and of the same length but the front pair shall be higher than the rear. Distance between front and rear pairs is 25mm (width of my steel rule), therefore height difference is 3° of 25mm, which is hardly discernible and the difference can be made up by glue thickness.
All the wings' struts, 6 pairs (including the cabane struts) shall be cut to size, allowing 2mm protrusions into the wings.
The 4 pairs of wings' struts shall be taped to the strut templates which has the 3° incidence marked. Not much difference but it's there.
The pair of inner strut templates, where the struts join the booms, shall be handed.
Glue 6 pairs of mini-disc washers to the struts. These can be made 6mm in diameter by using a hole puncher.
Glue the 4 paper/heatshrink/plastic tubing on the inner pair of rear struts to receive the already made booms by using the 2 foam templates.
Glue the 2/4 control lines guides to the inner pair of front struts to accept the control lines. The location has to be sighted, aim for near horizontal control lines passing through the servo holes. Having the control lines raking backwards is acceptable.
Complete the rigging on the 4 pairs of struts.

Cut 2 identical wings with holes for the struts and dihedral jointline marked.
Dress up both wings and bend wings to the same dihedral. Reinforce the dihedral joint with small strips of aluminium salvaged from aluminum soft drink can.
Glue the 2 pairs of cabane struts to the foam pod.
Glue the lower wings, since this is about 2.5" wide, note that 3° is less than 0.5mm, just pack down the trailing edge.
Glue the 4 pairs of wing struts (with its strut templates) to the lower wing.
Apply glue on the 6 pairs of struts and bring the top wings on them. The mini-disc struts will help to position and strengthen the glue joints.
Complete the rigging of the wings and remove the strut templates.
Insert the rigged booms into the tubings on the inner rear struts.
Some adjustment by sliding the booms should be possible.
Check that the top booms are parallel and the rudder is vertical before gluing in.
Add horizontal tail, short fin, rigging and control lines, cover/capsulate the pod to complete the model.

Aluminum from soft drink can
Can be used at rear of boom, tubing for booms, straight line guides for control lines.

2 methods to dress up the pod:

Covering the pod

1. Slot the pod to receive the 2 pairs of cabane struts.
2. Cut 2 strips from the wall of an aluminum can and form 2 hoops to support the pod covering. The fore hoop is wider. Glue the 2 hoops in place.
3. Fabricate the pod covering. (choice of covering: cardboard is heavy, paper distorts easily, plastic requires forming)
4. Mark the inside of the pod covering where the front pair of struts will run through, using the slots in the pod as guides. Drill the 2 holes.
5. Glue the cabane struts to the pod.
6. Remove pod covering, paint, cut into a fore and an aft piece. Glue aft piece threading through the cabane struts and gluing it on the 2 hoops. Trim the bottom of the aft covering.
7. The front piece of the pod covering is secured by small pieces of double sided tape attached to locations at the front hoop and at the two lower sides of the pod. Trim the bottom of the fore covering.

Encapsulating the pod

1. Slot the pod to receive the 2 pairs of cabane struts.
2. Make a male mould, cover this with shrink wrap.
3. Make a papier mache of the male mould, the compound nose end can have an extra layer of paper. To ease the removal of the moulded papier mache, leave the bottom of the male mould clear except for perhaps 3mm of lipping. When dry, sand smooth.
4. Trace and cut the openings, paint the moulded cover and separate the moulded piece into a fore and aft pair.
5. The aft piece is drilled for cabane struts as per step 4 of 'covering the pod'. It is slip over the cabane struts and 'clipped' to the foam pod if lipping was moulded. Glue is still needed.
6. The fore piece "caps" on the foam pod. It is secured by the slight dimensional differences between the pod and the moulded cover (springing action on the part of the cover). Additionally, I can make small grooves in the foam pod to accept small key pieces that are glued to the moulded cover (which is like a nose cone, except it includes the gunner's cockpit decking.

The good thing about making the fore piece 'cap' on the pod is that the capping action is simplified and does not require further taping at the field. Now that I've hotglued the receiver onto the foam pod, I have to make another male mould if I want to try the encapsulating method. The main advantages over the first method are: 1) simple remove and attach procedure without taping at the field, 2) stronger nose cone now that the gunner's cockpit is included with the nose.

 7 March 2017

Sizing up the decking

A view of pod with board, cell, motor,
paper decking and engine.



I can't have both servo arms pointing in one direction, this is what happens at maximum throw

The number of servo splines must be an odd number,
so I resorted to subtrim after trying by swapping a few servo horns.

F929 939 is Rudder and Elevator. I use a mix so that the Aileron stick will turn the Rudder servo.



New motors and props from Banggood.
Bigger 3" prop but the 7mm motor heats up too much.

I tried with the 3" prop with a 8.5mm motor, but the 8.5mm motor also heats up too much. Reverted to Hubsan 56mm prop and it's ok. Next time I may try 65mm. 



(L) 3" prop, (R) 56mm prop



This is how I want to place the gears.



It seems the gunner/observer's cockpit is large enough to slip in the cell.



This is the motor connection on the board.

I noticed that not all motors have the same plug orientation. I determined that the one on the left matches with the board, so the one on the right needs to change.



So I swapped the wires to the motor on the right.



 

 

Without paper decking, it weighs 20.4gm

previous thoughts and actions

I blocked up the pod from 10mm white foam and it weighed 5.1gm before shaping. I estimate the pre-finish empty pod will weigh 3gm and the radiator engine subassembly will weigh 1 gm.

What catches my attention when blocking up the pod, is the size of it, it is so small! I have enlarged the width to 1.1/8" to accommodate the width of the receiver board. I find that the space available to mount the receiver board and the Turnigy 1s is barely enough after gluing the 1" nose block and 1" motor mount. I will need to shorten the battery connector at the receiver board. Should I have a removable battery hatch to access the 1S cell? The observer/gunner's cockpit doesn't seem big enough to slide in the 1S cell. Maybe I should insert the 1S cell from one side (starboard) of the pod and have my hatch at the side.

I want to try pull-pull for the elevator and rudder. I can't place the servo horns facing one direction because they are too close together and will clash with one another in extreme positions. If I place them in opposing directions, there will be two pairs of exit points. I can't have the servo screws accessible at the pilot's cockpit because that will interfere with the cell placement. Therefore, the control lines have to be secured to the horns and there will be no adjustment to the servo horns because the top wing will get in the way.

The forward pair of control lines will exit at the pilot's cockpit and the rear pointing servo horn will exit at the engine block. The curved decking at the pilot cockpit has to have exit holes for the forward pair of control lines. As the rear pair of control lines are at the engine block, I think I will first produce a profile of the engine block from 10mm foam, with a cutout for the entire rearward pointing servo horn, then I will detail the engine block's six cylinders and paint it before gluing it to a radiator block. The entire radiator engine assembly will then be glued to the top of the decking that is rearwards of the pilot's cockpit. Since I have to thread the control lines through the deck or engine block, I will finish the pod and radiator engine before threading and gluing them together and to the lower wing.

I have to think how I want to do up the decking. I think the current pod construction is too heavy.

The result is in! See photos above.

24 February 2017

The pod strength should be at the bottom where it is glued to the lower wing and where the landing gear is attached.

Interestingly from the internet, I also gathered that that's where the 'armour' against ground fire is for the real plane! And as for bullets from behind, that's what the great big spinning propeller does double duty! Maybe the nose is portion also gave some protection from the front. But I don't think there's protection from the sides, because the sides seems to be stringered fabric.

My idea is to use the base as the structural piece and anything above it is just a cover. The structural piece can be the 1cm thick foam I have from Daiso. The following's an idea for the cover using rolled paper construction, it was done 'free-hand', i.e., no measuring, calculating except estimation and done quickly. The top of the nose in this Airco DH.1A is flat, the nose kink is superfluous, I did it just as an experiment to see what I can get.




Looks like the pod?

Flat construction of pod.
The centerline is just so that I can have two identical sides when I cut it with a pair of scissors.

I introduced a kink at the front
and the top of the nose appears radiused.

Less rake at the nose.

Development of the less raked nose.

To develop the paper construction template accurate enough, 1) I can take measurements, or 2) I can repeat and make adjustment by trial and error or 3) I can make a mould and then trace out a template. Both will probably take about the same time to complete.

After giving it some thought, I think I can proceed like this:

1. Cut out the structural bottom piece.
2. Tack glue two or more formers. I think two is sufficient: one behind the pilot's cockpit, one between the pilot's and the navigator/gunner's cockpits. Perhaps a third one at the rear, in front of a permanent glued former for the motor mount.
3. Wrap paper over the formers, trim it to the bottom of the pod bottom and cut out the two cockpits as what we have done in the previous step is to make a mould.
4. Flatten and transfer to intended cover material, which could be foam sheet or paper sheet. Colour the cover material, curl and glue to the tack-glued formers but not the pod bottom nor the permanent glued motor support former. Release (e.g. cut loose) the tack glued formers from the pod bottom and we get one finished pod cover which is stiff enough to maintain its shape.

A few options to mount the receiver board:

1. Exposed: Through the top wing; use direct pushrods or pull spring to elevator and rudder, acceptable structural mounting.
2. Exposed: Just under the top wing glued on the dummy engine block; use direct pull spring or pushrods (unlikely) to elevator and rudder, weak structural mounting.
3. Hidden: Somewhere under the cover glued to the structural bottom piece; use indirect pull-pull or pull spring because of the propeller arc, strongest structural mounting. Note the width of the board is wider than the pod, so some cutaway at the pod is necessary.
4. Exposed: Through the pod bottom or just glue it right under the pod/wing; for lowering CG and indirect pull spring to elevator and direct pushrod to rudder, strongest structural mounting.

22 February 2017

1s, 8.5mm motor pusher with Hubsan 55mm prop, WLToys board, RET, pull pull or pushrod for rudder and elevator.








Make twin booms from 1.8mm bamboo dowels to connect to rear interplane struts. To position the interplane struts accurately on a biplane so that the wings can be positioned correctly relative to each other.

1. Draw the connecting points of the struts onto a piece of paper/card with any undercamber or top camber and cut as many exact copies as needed. (if the wings are flat and distance between wings is constant, then a single paper/card with connecting points on two parallel lines is sufficient.)  
2. Make as many identical prefinished struts as is necessary, tape/blutack them against/over the connecting points on the paper/card. Struts can be made over long so they can be inserted into the wings. (If there are cross-over wires between struts, they can be glued on now.)
3. Make slots/holes on the wings to accept the ends of the struts. Glue the struts to the bottom wing first, follow by the top wing. The paper/card will position the top wing accurately. Remove the paper/card from the struts and complete the rigging, if any.

Make two pairs of wings from 2mm foam sheet. Make pin holes for interplane struts. Bend and reinforce for dihedral, cut rectangle hole for servos on the top wing and glue the receiver board so that the servo horns are exposed above the top wing. Glue all the interplane struts.

Pod can be made from a block of foam. The tandem cockpit can be made removable to access the 1s and attached with magnets. Make a profile engine block from foam and use plastic tubing for exhaust. Radiator and engine cover from foam/paper/card glued to removable tandem cockpit. Motor is glued to the pod with propeller attached. Slide the pod between the two pairs of innermost set of interplane struts (cabane struts) and then the motor lead is plugged to the receiver board. Glue the pod to the cabane struts and lower wings.

Fabricate and glue the undercarriage to the pod.
Glue the elevator and rudder to the tail booms.
Make the pushrods and connect them to the servo horns and control surfaces horns.