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Jul 26, 2018, 04:35 PM
Registered User
Please post some video up if/when you get a chance. I have similar plans for a smaller plane (400mm) using 2 x 1102 8000kv & 1s. It's going to be a close proximity fpv cruiser. Would love to see how yours handles.
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Aug 31, 2018, 02:57 PM
"its not a hobby its obsession
jiggz's Avatar
Just picked up a couple of these for rc pss
I have 2x umx p40's which will be the donors with as3x
Sep 15, 2021, 04:47 AM
jofro
I got also two of these couple of weeks ago, ending up converting both to EDF jet power.
Sep 16, 2021, 11:24 AM
Proud of Brushless Sprouts
Commander Clumsy's Avatar
If you're living in Belgium, I've got some new ones for sale!
Sep 16, 2021, 12:44 PM
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edwen303's Avatar
Any new flight footage to share? Can't find them in the US any more
Sep 16, 2021, 07:03 PM
jofro
Quote:
Originally Posted by Commander Clumsy
If you're living in Belgium, I've got some new ones for sale!
They are avail everywhere, just ordered the 3rd. one to fit the spare motor I got laying around. Lot of fiddle to transform, took me some 60 hours + each to convert.
Sep 16, 2021, 08:49 PM
Proud of Brushless Sprouts
Commander Clumsy's Avatar
Quote:
Originally Posted by jofro
They are avail everywhere,
I don't know where you live but they have disappeared in my part of the world, except for Banggood with ridiculously high prices.
Sep 16, 2021, 09:23 PM
jofro
Under $25- Austr. down here, retail price from hobby shops. Not too bad for a chunk of foam.
Oct 03, 2021, 04:01 AM
jofro
For anyone interested in reading. Enjoy.

"Alpha" jet, micro EDF conversion.

Last couple of years, my main interest in RC modeling was focused on EDF jets, with a great variety of new micro size power units available on the market. In the past years, the most common units were 64, 70, 80, 90 and rare 120mm EDFs, but it's nice to see these days coming onto market a great variety of 30, 40 and 50mm, multi bladers, some available even with counter rotation impellers, a good news for multi engine powered jets to minimize the torque effect as I have recently documented in one of my 4 engine 50mm "2B2" Delta EDF creation.

I was always most fascinated by any sort of micro size models, a rarity in jets department, so I have in the recent years created a good dozen of my own design, 'delta types' for its simplicity, mainly using 30 and 40mm EDF units as hand launchers, tho, not my favored way to get airborne. From my experience I have found the smaller the more handful, however a great experience and learning curve.

One of my recent fun experiment was also fitting a 40mm EDF unit to a kids foamy chuk glider, (reject bargain) I have found in some junk shop for a mere $5-, and converting it to RC. The high RPM power unit was running only on 2S, but rather inefficient to power this larger 5 feet w/span model, so it was swapped with the more effective prop power and the 40mm one used in a mini size Delta jet, moving like a missile for a rather very short flight times of less than 3 minutes with well managed throttle.

After some search, I came across this FMS micro foam model of "Alpha" jet, as a kids toy glider, to throw around in the parks. Pretty, little scale model judging by the pictures at some 25 bux, so I have ordered couple just in case, to see if I could convert it to RC as a scale looking micro jet. I'm pretty accustomed flying couple of larger, 64 and 70mm EDF, "Alphas", so I was looking forward to see this micro version on my work bench. On its arrival, after opening one of the boxes, the tiny model (22nd. scale) at 47x60cm (S/L) comes in 3 parts, the fuse, main wing and small elevator stabilizer, both easily slide inside the fuse slots and ready to play with. There's no glue required, as there are some moulds and cavities for a firm fit. Basic instruction is included and couple of sheets of decals to live it up in scale colours, if one desires.

Extremely light at only some 60 grams AUW, the first thing I have noticed was a bad warping of the main wing, being of very thin profile, with its tips twisted to the point I would find it just about as un-flyable! After check of the spare box, the same thing! I knew immediately it will have to be well reinfoced with carbon fiber spars. Model is being made of EPO foam, to make it more durable for crash landings, but this type of bubbly foam is not the most practical for crafting, especially in this micro size. The trialing edges on the wings are only about 1.5 millimeter thick, with out any strength so they will have to be totally redesigned for moving control tabs in both Ailerons and Elevator functions. I have immedialely realized this will be a great challenge little model to build as RC.

Before adding the 1.5 and 3 mm carbon fiber spar tubes to the main wing and Elevator stab, I have placed both under the heavy press and let it be for couple of days hoping to straiten it up somewhat. The black painted canopy made as a separate part bonded to the nose fuselage section, was carefully removed with the sharp hobby knife, and I have discovered inside the cavity was placed a 20g metal bar for the CofG balance correction. Great thing, after its removal the AUW of empty frame was only some 40 grams now.

The first job was starting to cut, dig and dremmel the foam from inside of the solid block canopy, using the sharpest hobby knives to give me an idea what to expect when I get into the fuse to create an internal duct. Pretty messy job with extreme care to be taken not to only avoid cutting your fingers but to remove as much foam as possible with out any damage to the outer skin, and still leave some thin foam layer which was later reinforced from inside with numerous coats of PVA glue between some fine sanding to get just a bit of extra strength with the minimum amount of added weight. The finished canopy ending up at one gram, great start to keep it light!

Next job, after close fuselage inspection and precise marking with the use of the ruler was to divide the part of fuselage along the center line of the intended air duct, and again cut out with care using the sharpest long knife blade to separate the top from the bottom sections, between the air intakes and the slightly shortened twin exhaust outlets. After its removal I have found just a small internal cavity making the cutting slightly easier, but it took extreme care to cut out rounded fuselage air intake and efflux openings into the solid foam blocks.

Dremmel tool fitted with the various grounding disk came quite handy in this exercise. After some enlargements of internal duct I have marked position as far back as practical for the 30mm EDF power unit, leaving just enough space for fitment of short twin exhaust thrust tubes, and started very delicate cutting into the top and bottom halves for a perfect air tight fit of the EDF shroud when both halves were placed and closed together. Again, an absolute nightmare of the job with the rather course EPO foam. The 30mm fan with its larger bell mouth opening (37mm) was just about the limit in size to install in this small fuse frame leaving only one mill of foam body on the bottom halve. To make it really air tight, the fan unit had to be bonded in permanently with the use of silicon when both halves were later joined using Epoxy. Unfortunately not removable, after further placement of X-ray film made up, tapered thrust tubes, which also had to be well secured with the silicon in this small air tight pressure chamber and exiting through the foam rear cut out holes. For the optimal performance I have used some math to create both thrust tube combined outside diometer outlet, some 15% smaller than the fan sweped area. To perfectly align the both short tubes with the fuse, I have made up 30 cm long mock ups fitted inside to exit rearward while waiting for the 5 min. Epoxy cure time. Fuselage air intakes are pretty large so there won't be any issue of power unit's air starvation. But unfortunately with the twin exhaust and only a single fan there will be some loses in performance, a common thing of EDF power in this configuration.

Weight minimization will be the main key for the success of this model with rather limited thrust of this tiny fan and the considerable weight of 3S lipo battery to run it. The smallest 30A, ESC was soldered directly to the shortened leads of the power unit to eliminate any extra weight in gold bullet connectors and the unit was placed and well secured in the air flow of the inner duct with the power leads exiting through the cut out opening to the marginal carved-out size battery compartment under the canopy. This opening tunnel is also used for all the servo power leads to the micro receiver placed as far in the nose of the model as it was practical. The tiny 6ch. Spektrum receiver has got couple of 35mm antennas sticking out sideways, and after being used in some earlier models the constant bending of the 'whiskers' during handling must have caused the wire futique at the solder joint, breaking off one side, during placement into the fuse. Bugger, tho good thing, because after closer look the opposite whisker was holding only on couple of fine wire strands! So, another micro surgery to replace the both under the strong magnifying glass, re-sealed and this time placed inside the nose section not by bending the new antennas , but cutting out slots in the fuse and after placing it in re-bonding the cut out parts, with touch of putty and finished off with the touch of matching paint. While cutting out a small cheater hole (5cm2) covered with the alum mesh in front of the canopy it alloves some extra air flow sucked by the fan over the battery to keep it cool. The battery compartment was carved out as far back as I could and still leave very thin wall, separating the internal duct with the hope to achieve the correct CG balance.

There was a lot of thinking to work out what would be the easiest Elevator operation, 2 servo system was out of the question due to an added weight, so the only way was to re-design the sweped back Elevator stab, by cutting the rear into a strait line and re-join the 2 separate moving tabs by piano wire made up joiner. The rear end cone had to be cut open to be able to install it into the fuse slot after the whole new plane/moving tab was ready to be fitted with 4 Dubro micro pin hinges for precision and reliability. The micro servo to operate the function was another fun to install, with out any open cut into the outer fuse skin to run the servo lead through. Another bit of nightmare with the use of all sorts of long Philip head screwdrivers to drill a cavity hole with just about impossible access to push the thin 32G signal lead through. Success at the end, with the servo fitted deep into the rear part of the fuse before being re-soldered to the power/signal lead.

Aileron servo leads were also run through the prepared cavities to be re-soldered after the main wing was fitted. Few days after the clamping of the main wing, it came up slightly more even, but the thin outer tips were not up to the job. 3 mm carbon fiber spar tube was well epoxied and finished off with liquid nails into the carefully cut out grove along the full length of the wing and left cured overnight under the heavy load in perfect level. After the cure there was a huge improvement but there was no way the stock line-marked Ailerons could be cut out and used as a moving tabs. With the trialing edge only some 1.5 mm thickness I have decided to run along the edge 1.5mm CF rod, well epoxied to the finely cut out grove and finished off with high strength plastic tape to secure it further. This addition finally made the whole wing firm and stiff for safe operation. Additionally extended Ail. control tabs were laminated out of thin balsa sheet and 0.5mm marine ply and shaped up to a slight taper, later fitted to the CF lined wing TE's by special hinge tape. There was some 60mm gap between the Ail. moving tabs and the fuse, filled up with more laminated and shaped up sort of fixed flaps.

This Ail/Flap/El. extension, gave me all up some extra 'dm2' of flying area, which will be a great reward to minimize the wing load of this marginal powered micro jet. Don't forget, the smaller the model the wing load increases as the air can't be made any thicker, 'scale-wise'. Before the Aileron tabs and servo installation, the main wing was carefully slotted inside the fuselage cavity with some liquid nails secured along the joining gaps. The smallest 4.5 gram micro servos I could find in my spares box were installed into the cut out wing cavities closed/sealed off on the top surface with the thin layer of 0.3 ply-veneere. Servos were secured with the double sided tape and further secured by fiber tape. Prior to installation they were programmed and set as 2/6 separate twin channel operation. The small channel cavity was cut into the thickest part of the wing's LE for the servo leads to run along after the micro soldering to the pre-installed leads from the fuselage. Sealed off with the fiber tape ready to be painted and sealed off with the clear laquer.

Aileron servos in place, the next job was installing the moving tabs with carefully applied special hinge tape from the both sides, top and the bottom, making sure it moves nice and freely. Using tiny allum control horns with miniscule quick links, controls were hooked up and test run with the 3 way toggle D/R set up at 40, 50 and 60% TA. Didn't take long, and "bugger"! Spanner in the works! Right hand servo got stuck at full deflection at only low D/R. After further re-set it worked shortly, but not returning properly to Neut and got stuck again! Thank God, it happened on the bench, not in the air!
Bit of the nuisance, so I had to rip it all out and upgrade both servos to the next size up with more torque for safety. It took only a slight enlargement of the cavity in the wing and a bit of micro soldering to re-join the new power leads to hook it up again. All good this time, with more precision travel of both moving functions.
As mentioned earlier, I have never enjoyed hand launching EDF jets, especially one handed on my own, so for safety I have decided to convert it also as a mini sling shooter, by adding a tiny ply skid hook under the belly with couple more skids at the rear to protect the fuse, and fitting a short CF extension rod to the tail cone for easy hold of the model while under light bungee catapult tension. This one will need only very light bungee pull of about one to one, after making up 2 meter long light rubber cord attached to further one meter light nylon string for safe and steady rotational speed rather than akwardeness of hand throws. Even at such a light AUW as 280 grams, it simply feel heavy while holding it in hands, from my experience, so a good head speed start will be a good plus. "Don't forget, the smaller the more handful!"

Before finishing off few minor details, I have cut out identical extenders to tape up to my other stock model and took it out to an area with very high soft grass to check the effect of the added flying surfaces, compare to the stock. Firstly started throwing the model into the light breeze, as out of the box with only wing improvement of added spar. It is designed as slight nose heavy, so needs to be released some 10-15% positive, and with a good throw it seem to climb somewhat, before gentle nose down glide to a crash landings. Rather boring for an RC pilot, but it has to be done!

After half a dozen of chucks I have marked the perfect CG spot, added the made up extensions to the main wing and Elevator with the tape and off it went again. Immediately noticed the huge lift improvement, it went up like a rocket at some 45-60 degrees so the CG had to be moved some 22mm backwards to obtain an ideal result. Back on the bench, I have marked the new balance point to the new RC creation, with model being considerably nose heavy using the 3S/850mA pack, so for the first flight I may use lighter 3S/650 or even 3S/500 to start with.

There were few minor mods required to secure the battery in place with the CF rod pushed through the fuse so it can't slide forward as Velcro isn't practical in this scenario. Canopy is secured with a single self tapper screw to make sure it can't fly off, and the tiny El. stabs were fitted to the Rudder fin to make it more scalish. The whole model was gradually painted during its construction to give it some livery and finished off with few decals and colored matching vinal tape. The final clear, seal off coats I'll leave after number of test flights, and the next chapter to continue.
Enjoy, Happy and safe flying, Joseph Frost.
Oct 08, 2021, 06:07 PM
Registered User
Quote:
Originally Posted by Radek74
No, thrust of both engines is identical. The permitted engine voltage is only 7.4 V. 3S are certainly faster. But low weight allows also slow flight and soft landing. I am satisfied with the speed and flight characteristics. I currently have no flight video. R.
I havé those motors on a quad with 12a esc. I eventually use triblades 4020. Why changing ? Not for performance but DEAD silent flight. You Will get more air flowing around the wing as well. Drawback is for the launch but i just hard throw and use throtte after
Oct 10, 2021, 03:32 AM
jofro
Quote:
Originally Posted by Radek74
2x brushless 1104 6500KV, 5,5g,
prop. 3x2 or 2,5x3
2x ESC 6A
Li-po 7,4V, 550 mAh
2x servo 3,7g
micro receiver Graupner
weight 124g (without battery) 152g RTF

This engine position allows safe throwing of hands (versus to the pushing arrangement). According to the catalog is the thrust of one engine 95g. Swiftly flies to 50% of the gas. Control is only by using a horizontal tail (elevator) in the delta mix. Flight time up to 6 min in economy speed. Tips for next time: Area of elevator may by smaller of 20%, batteries with larger capacity (more weight 10-15g will be no problem).
Cauky Starec, s makym "R". LOL. Uz si skosil namontovat EDF? Akurat cakam na tretej model este viac vylepsit. Cauky z jihu. Frostak.


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