6 February 2017
Wong asked me to give him a WLToys receiver board so he can build a 1S F22 and fly it with his Flysky transmitter. He wasn't detailed in his request, because he would also need a matching pusher motor and prop, some suitable 1S cells and at least a simple 1S charger with the correct connector. All of these, does not have.He also received from Thang the F959 2s version with folding prop and thought of putting it on his F22 board which is maybe 8-10" only, 5mm foam with transparent tape both sides. Thang and I both think it would be too heavy and small. From the F5 experience, it would be difficult to fly with 8.5mm motor let alone a 2s motor which seems to be double the diameter of the 8.5mm.
He's an old man. On one hand, it would be good if he can start building, on the other hand, would that be too much to expect of him? Perhaps I can build another 'Mirage' (as he called my delta) just for him. This time with the following changes: 1) prop slot instead of tail pusher because I don't have long wires and he prefer prop slot, 2) take Thang's suggestion to cut off the 'nose cone' tip off the hubsan prop, this way I will not have to drill through and waste a few props along the way, 3) I could tie the motor to a short CF flat bar cross-wise or a wood strip with cotton thread and then hot glue the assembly onto the plane.
Another idea is to thread tie motor to one end of a stick and hot glue the receiver board to the other end. This assembly is then hot glued to either the top side or the bottom side of the plane and then the 1s cell is on the other side to reduce the vertical displacement of the CG. Yet another idea is to have the motor and prop as a tractor but that idea has other limitation.
To concentrate equipment weight at the front for short nose subjects: epoxy geared motor prop to servos of receiver board.
16 January 2017
I said goodbye to this pusher jet yesterday when it went out of sight.
It was flying great, spins were entered with the CG back and elevator and aileron stick to extreme, recovery was to level aileron and push elevator down with throttle.It didn't glide like a glider but it was stable and quite good.
On the last flight it was following two eagles and suddenly it entered their thermal, and it went very high up. Then it went too far, probably encountered down draft or updrafts (major turbulence for such a light plane) and it disappeared.
Wong was impressed with it, he flew it a few times, once with his own Flysky transmitter too. Wong wanted to do one but he doesn't have the foam or the right gear. I didn't create any paper plan so it won't be possible to give it to him.
The 8.5mm motor has enough zoom even on my tired 1s. Flying gently it can fly about 8 minutes or more. I think pusher with hubsan prop is great. Thang had a small 6mm prop slot, flies good but it was underpowered even though it was lighter because he used dsm2 all in one. Maybe I shall do another pusher jet because it was a durable, easy to repair reach-to-plane (compared with Sakura and Flying Flea). No matter how badly wounded, it would still fly.
26 September 2016
Skycolor flew again with my single aileron modification. In effect, there is not much difference and I supposed that the single strip aileron is too narrow. Skycolor turns left quickly but turns right hesitantly. It would be better to have equal response in both directions. Since it glides straight, much more right thrust is required.Nothing broke and Skycolor can still be improved, but it's kind of boring now, maybe I shall choose a new target.
19 September 2016
The $10 plane is "SkyColor", it says so right there on the wings although I prefer"Lefei". The chuck glider was about 37.4gm. I got it from Rotor Hobby. $11.00 before 10% discount.
Later that afternoon, I sliced up a slot underneath the wing so that the battery can be slide all the way back. I soften the hotglue supporting the motor mount with my hotglue gun and set more right thrust.
On the morning of 18 September 2016, it flew better and it can glide, but it was still nose heavy. I could glide for about 2 minutes and the power is now sufficient for looping from straight and level since I have reduced the elevator drag considerably. Because I have the battery located at the CG, I should be able to use a wide range of 1s cell battery and not affect the CG too much.
The model is tame, the rudder works but this plane is better flown with ailerons because it takes a while for the rudder to change the direction of the plane because of the minimal dihedral.
Pretty good for a $10 plane.
To improve glide and control:
- I could remove the geared motor and install a direct hubsan propped pylon to reduce the drag that was caused by the wheeling propeller.
- Trim the canopy to fit over the receiver board (don't move the receiver board back because of clearance and length of pushrods but I have to find an extension for the pylon motor) to streamline the model slightly. If necessary, to make a removable battery hatch at the bottom if the canopy has to be glued.
- Make an aileron at the port wing, connect it to the pushrod so that it has a single aileron coupled rudder.
13 September 2016
- Remove canopy (and ball bearing weight). Make a moulding of the canopy. (Less work then gouging it out to avoid the receiver board.) Make it into a battery hatch.
- Hollow up the exposed cockpit to make battery space.
- Hot glue WLToys receiver board to cockpit, over the battery space, check that battery can be slipped under the board.
- Modify the tail surfaces to make them operable.
- Connect receiver board to tail surfaces with wire pushrods running in short lengths of tubing or wire loops, which are in turn anchored to the fuselage's exterior.
- Mount a 7mm or 8.5 mm motor with hubsan prop to the tip of a pylon, insert pylon through the fuselage's top through the wing to anchor.
Some more ideas
- If I can figure out how to make small accurate tunnels through the fuselage then the pushrods can be concealed better. The usual serrated tubing advice apart, I found from RC Groups, a poster who wrote that when they had to make lead-out holes in foam wings for control line planes, they set up a jig so that a piano wire runs vertically up and down. The wing is positioned below the lower end of the piano wire. The lower end of the piano wire is heated up and allowed to drop through the foam wing.
- From elsewhere, another modeler described that when he makes lightening holes in foam wings (before they are covered with veneer), he first cut a slit in the foam with a straight edge and sharp cutter, then he insert the hot wire into the slit, fix up his root and tip templates and proceed to hotwire out the core.
- Instead of a direct drive hubsan propped pylon mounted motor, I could also mount a WLToys' geared motor on the nose.
- If I want to use pull-pull with a WLToys' board (and I can make accurate tunnels in the foam fuselage), I can mount the pull pull conversion to the cockpit but this would mean that I cannot insert the battery from the top. In this case, I can make the battery hatch at the bottom of the cockpit floor so that I can swap battery from the bottom of the fuselage.
- Or perhaps I can mount the pull pull conversion levers at the back of the cockpit against the 'fuselage former' infront of the wing.
- Single aileron wing is a possibility.
7 September 2016
Wong is saying I am flying this delta too much. Actually it's only a month, but I have let him and a few others tried and I have flown it for dozens of flights. Tight turns, low passes, easy flying!I have moved the CG backwards and increased the elevator throw until it spins easily. It still didn't manage a proper "down-elevator" maneuver, there's still forward speed. But with the rearwards CG, I can loop from level when the battery is fresh.
I went to combat mode and managed to whack Kasim's flying wing, bringing his down but mine also as I had dislodged a pushrod. Got a creased wing tip as my medal.
I could do a micro skysurfer type, or how about a powered 'Alula' wing type?
18 August 2016
I brought the model out for a flight on 16 August 2016. It flew but I had to apply elevator and aileron. The trim was upset. So yesterday I replaced the pushrods with a pair made with 2mm wooden rod and the 0.55mm soft wire. The previous all-wire pushrod was 0.4gm, the new pair is 0.8gm; a weight gain but noticeably stiffer. The soft wire ends were heatshrinked to the 2mm rods. When I have the flying setting, I shall apply CA to lock them in position.I also brought the CG back by cutting 1cm of the foam spine aft of the battery location, this way the battery/cell can move 1cm back.
9 August 2016
Last Sunday, 7 August 2016, woke up too early. I had a slow breakfast at a hawker centre and changed the F5 planform to a delta type, maybe a drakken/Eurofighter or something like that. I ripped off the F5 planform and although I wanted a simple small delta of 9" span, that would mean throwing the remaining foam (300mm width), so I made the span to the full available width of the foam sheet. Then I looked a bit and decided it was too large ("drag"), so I trimmed the planform to reduce the wing area slightly. Larger elevons, instead of the tiny tailerons of the F5 was built in this time. The tail fin seemed a bit too small, so I used the offcut and made a new fin, bigger but small in relation to the new wing area. The fuselage is of course the same F5 Fuselage and keel. Very quickly the recycled model was assembled and I went to the flying field.A bit of reflex (by curving the soft wire pushrods) to the wing, at mid-throttle, a toss and it was away for its first flight. The torque problem is gone, the CG and reflex combination is right and the model is flying for perhaps 10-15 minutes on its first outing (not bad considering I'm using 3-4 years old single cell) including failed loops which I shall call stall tumbles, rolls and inverted flying.
There is insufficient thrust to overcome the drag for a loop from level attitude. Next flight had less reflex (battery shifted minutely aft), and I think it flew faster. After that, I could go over the top for a loop from a dive but it was untidy because I don't have enough thrust control. If wing area is trimmed a bit more, flying might improve. Being so light, crashes hardly mean anything. It turns tightly and doesn't spiral in, it would be possible to fly this in a small space. It glides safely, but not like a glider. At one time I got it into a spin, and that was kind of fun. I tried replicating but wasn't successful in my attempts even though I increased the elevator throw mix. It was windy, but the model flies ok because it wasn't as draggy as the Flying Flea or the little birdy.
25 July 2016
It was very top heavy and the torque was difficult to overcome. It managed 2 flights with one into a tree and the other in the thistle bush on Saturday; short darts, upside downs darts and right rolling darts notwithstanding.Still at the field, I heated my cutter with a lighter and used the heated blade to soften the hotglue at the motor and set in some side thrust. The propeller was causing the model to roll to the right, so I pointed the propeller to the left side. The idea is to make it yaw left to counter the right roll. This newly introduced side thrust combined with the down thrust (propeller pointing down), makes the model screwy on tap. It was even more difficult. Ah... maybe less side and down thrust and more wing area?
Back home, "fuel tanks" added and the battery was relocated to the bottom.The fuel tanks will give it some area at the tip to counter/resist the torque. I also added a replacement fin because the original fin was missing.
Then I put in a profile canopy because that area now looks too vacant and the TV programme was not engaging.
Thus modified, I went back on Sunday. I could throw it further away but after a few tumbles, I noticed the wing has a tear developing and has buckled. All those darts and tumbles has taken weakened the foam wing. Too bad the F5 Tiger has to end now.
If I get back this Saturday, I will strip the F5 Tiger wing planform and glue on a Dassault Rafale wing planform, which is basically, a right angle triangle with tiny canards to give it some pointy bits. More wing area will help to resist/counter torque.
18 July 2016
I drew the planform on 2mm foamsheet, approximating from a F5 Tiger picture off the internet.
Temporary weight was added to the wing piece (less the pointy nose) to check the approximate balance for a short glide. Yes, tested without the vertical fin, so the glide will easily slip and fall off to one side but should be good enough.
A cotton bud dipped in alcohol was applied to the glued surfaces. The glue was picked at and peeled away. For the carbon fibre strip, a piece of tissue was employed to rub away the glue residue.
After that, the horizontal fuselage piece was recessed to accept the WLToys F949 receiver board. The motor slot was grooved to accept the bottom plastic ring around the 8.5mm motor.
the horizontal fuselage
The rest of Saturday afternoon was spent experimenting with making 3D objects from foam and plastic.
The wing piece was hotglued at several spots to the bottom of the horizontal fuselage. Then the nose piece and the white keel piece was spot glued.
Then the salvaged pushrods were straightened and re-used on the F5 Tiger. The wires were first straightened approximately by hand, then I rotated the soft wire while withdrewing it bit by bit through the opening and closing long flat jaws of a long nosed plier. I carried out and passed the stiffness tests of the pushrods. This involves pushing the pushrods against the table and feeling the amount of force it took to bend the pushrods while
When sizing up the pushrods, I realised I could have saved myself some trouble if I glued the white keel piece after I linked up the pushrods. Because with the keel piece in placed, I cannot place the wing and tail flat on the table. I had to raise the model by sandwiching one side of the wing and tail between a steel ruler and a base which is high enough to clear the keel piece. In my case, my base was my TV remote controller which was placed upside down over the table and because the steel ruler was too light to cantilever the model by itself (the battery was still strapped to the model). I used my mobile phone portable charger to weight the steel rule down. If I could place the model flat on the table, I would have skipped all that.
A point to note is that the servo horns were raking rearwards when the pushrods were bent to length. The idea is when the servo horns are re-positioned to their respective 90 degrees positions, there will be 'up' tailerons. I think it is necessary for the F5 Tiger to have a forward CG and plenty of 'up' tailerons because of its size and weight.
A piece of scrap grey foam was cut and curled to form the top nose piece (and wind shield) and glued to the fuselage. Another piece was glued to the front of the receiver board. I wasn't sucessful in my attempts on Saturday, but I could still use one of those pieces to impart some notions to the model.
Finally, the fin was hot-glued to the fuselage. Only two thirds were glued, this is so I can tweak the fin during test flights. I kept telling myself that I must glue the fin after the pushrods were sized that I omitted to consider the effect of gluing the keel piece before sizing the pushrods.
No sandpaper was used in the process, salvaged parts and hot-glue were used throughout. The only new resources used were the foam sheets and tape.
Nose heavy, so more up tailerons would be required.
This is already 15 gm lighter than the BD 5 but the wing is much smaller.
If I used a lighter cell, and I should because I don't need so much capacity, it will weigh much lighter. If a 200mah is used instead of the 520mah, the AUW will reduce to 29gm.
As it is, the thrust at full throttle is not enough to push the model up.
It feels heavy for its size, I can imagine it will have to fly fast so I will have to throw it quickly to bring it to flying speed.
I shall bring for test flights a screw driver for adjusting the servo horns and some sub-200mah cells if the 520 mah is too much.
34gm AUW (if using 520mah cell), Span 7", Length 12", 8.5mm dc motor with extension wire, hubsan propeller fitted as pusher, WLToys F949 receiver board with elevon mix at the Flysky FS-i6 transmitter.
Will it be a useless dart or a flying model? I held the model lightly pointing upwards and full throttle on a lighter 1s cell (@4.0V after the experiment) and I think thrust to weight is around 1 to 1, but the model wants to roll to the right because of the torque reaction. I adjusted more 'up' on the left taileron and of course it has no effect, it surprised me for a while until I realised that the model was not flying so there can be no airflow over the taileron to roll left. I was thinking of adding wing area or wing tips to lengthen the span, but I should try it as it is and see how it is. If I get this flying, the rolling right will be a blur to the eye. Prop to Span is 55mm/175mm = 31%, not ridiculously high, like the Doraemon and the Flying Flea, not low either since the wing area is so tiny. The torque increases with throttle almost instantaneously and the resistance to roll by the wing and tail can only increase proportionally with an increase in flying speed. My initial launches should be at half throttle with the F5 Tiger banked to left as it leaves my hand. And if that is successful, not to jerk to full throttle once it is flying until I discover the F5 Tiger's quirks. The CG is high, so if the model turn turtle frequently, I can also consider mounting the battery below the wing. The keel piece gives me confidence that it will withstand a few nose dives while I discover the quirks.
In any case, modification is definitely possible, for example, I can re-use the fuselage and fin and attach them to a new delta wing which will give more than twice the F5 Tiger's wing area.
15 July 2016
Quick to build and yet it flies, that's the theme I am after.The BD 5 with its wings clipped to fit my motorcycle box, wing span supported by a CF strip, the vertical fin and rudder clipped (adverse yaw, ie, yaw became aileron) and a few grams added to the nose to bring the CG forward floundered for the last time on 3 July 2016 when the nose snapped on impact and my patience ran out. It would be a simple procedure to glue it back on but getting it flying will not be that easy because the CG still appeared to be too far aft. Oscillating purpoising movements developing into sharper and sharper stalls indicated a rearward CG. I don't think it will develop into a "nice" flying model unless more modification and adjustment is committed, so I'll just pass. I gave up on the BD 5, and will re-use all the components for a 'quick to build and yet it flies' pusher jet.
Salvaged parts will be: motor, prop, motor lead extension plug, receiver board, velcro, soft-wire pushrods, control horns and the magnet and metal screw used as noseweight.
Last night I used my newly arrived Flysky FS-i6 and tried its Elevon mix and reverse functions on the BD 5 and it works. I am therefore ready for an elevon equipped plane using the parts from the BD 5. But I should record the AUW of the BD5 before salvaging them. Although the propeller is small, there is sufficient thrust to fly the BD 5. If I make a small pusher plane, the same motor and 55mm prop could possibly zip it around in a fast fashion. A model for a mid mounted motor will need a shorter nose than if it is rear mounted but I think that's where it will be structurally weak too. If I want to motor rear mounted, the nose has to be longer than what was with the BD 5 which I had to use nose weight in the form of the magnet and a large metal screw.
So I came up with the idea of a flat horizontal fuselage of 10mm foam or whatever material handy. To hot glue the pusher propped motor to the rear and receiver board midway, connect the motor to the receiver board with the motor lead extension wire, then hot glue the velcro strip to the front. Then I shall make a hinged pair of tailerons and hot-glue them to the rear, at the bottom of the horizontal fuselage and below the motor. The tailerons shall be connected to the receiver board with the control horns and soft wire pushrods. Then I will place the battery onto the velcro, and find the balance point. I will make a pair of wings, find its 25% point and glue the wings to the bottom of the horizontal fuselage, coincide the 25% point and the previously found balance point. Sure the overall CG will move backwards slightly, but it ought to be ok.
If I feel like it, I can also cut and glue on the vertical fuselage profile. Within limits, smaller wings are lighter, fly faster as they have less drag, and perform kinetic aerobatic moves, bigger wings are heavier, fly slow but they are draggy and get carried away by the wind easily, they are also more sluggish and cannot perform kinetic moves. I am thinking of a F5e Tiger.
No comments:
Post a Comment