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Old May 01, 2013, 11:14 PM
looking up down under
scruffy1's Avatar
Australia, NSW, Fairlight
Joined Feb 2008
1,375 Posts
Mini-Review
mini DLG (aka Unique DLG)

well, i haven't got started on the binary 900 (yet...); very remiss of me, but as a stimulus to actually overcoming the inertia of what seems a dauntingly concise build, i have procured one of these

as stated in my blog entry regards the model :
for those interested, the "new" version is presently on backorder at hobbyking, listed as mini DLG composite discus launch glider, but i bought mine (the older version) from stella via aliexpress.com listed as mini DLG glider (or more verbosely "New! Standard Mini DLG glider yellow Balsa Radio controlled RC model airplane 2 servos pre-assembled removable fuselage head "); she stocks the "new" version too

the commentary on the plane will refer to attachments (below) where appropriate

first up - thumbs up to stella at aliexpress for not only fast mailing, but also for intelligent and rapid replies to any queries i had about her wares - you can see in photos 1 & 2 that packaging was ample, and the glider arrived intact wrapped in soft foam paper inside a solid 2 part cardboard box which itself was wrapped in even more cardboard, packing tape and 3 plastic straps

the next 2 photos are simple views of my actual model (3, 4)
worth noting at this point that hobbyking list the "new" version which has some subtle differences - notably a slightly smaller wingspan due to the tips being rounded at the rear rather than more oblique line of the original; it also sports carbon rib capping and supposedly superior "oracover" film, which appears to be translucent white versus transparent yellow on my version
stella has that same version listed here - more expensive than hobbyking, but includes an extra pod and a dedicated airborne lipo battery pack that has inbuilt usb charger - well worth considering for convenience if you don't have any lipo gear yourself already

specs :
Packing size: 103cm x21cmx23cm
Length: 750mm
Wingspan: 980mm (950 - new)
Weight: 115g (120g - new)

the minimal online documents are linked here

build quality is excellent - there were a few small wrinkles in one wing on mine, and a degree of twist, both cured with a simple application of covering iron and counter twist - easy for me but perhaps again not so simple if you don't possess the necessary tools already; the fin and pod showed some weaknesses in use - more later on that

construction such as required consists simply of threading the elevator horn on the rod, and sliding the surface under a locking tab and screwing the lock screw into the pre-drilled hole
the wing is similarly pushed onto its mounts and two 3mm nylon bolts secure the deal - although it takes a bit of jiggling to seat it initially

the pod comes complete with 2 mini-servos and all linkages - you just need to add a receiver and battery (or just a receiver with the new version from aliexpress)
i initially used an extension for the battery pack, but then rediscovered the possibility of attaching the battery jst plug direct to the receiver - make sure to plug it in correctly (don't ask, but reverse polarity heats up the receiver enough to melt plastic - no apparent harm done); omitting the unnecessary weight of the connector was good, and the components fit so well that i can later consider a less "bulky" canopy to cover the pod and streamline the fairing over the servos and onto the wing, to minimise frontal area
a small wad of foam (per my gram scales it is weightless ) holds the battery in place quite firmly (pics 5-7)

components i added were orangeRx r410 weighing in at 2.5gm, and the turnigy nano-tech 600mah 1s lipo weighing 16.2gm; the all up weight after some modifications to the airframe was 111gm - yes folks that's 3.9 ounces, with enough power for possibly 10 hrs of flying given someone else reports an hour flying on a smaller 1s consumed 56mah
airframe plus servos by my calculation are just over 92gm

i am still not sure on cg measurement; the dozen or so launches i tried yesterday (before the wind came up far too brisk, today is equally uninviting) shows me that with my setup i need a little down trim, as the balance seems to be a little tail heavy
if i could get a battery with similar capacity but more cuboid, i could manage perhaps a better balance with no additional weight by moving the mass into the nose further - i have a 2s nine-eagles i got for the binary, but hobbyking's lightest appropriate ubec to tone it down to 5v weighs 7.1g without a jst connector attached

issues i have encountered are probably common

the tail was cyanoacrylate glued, but was a straight plastic film to slot joint, and the tail skewed on the second landing - not up to catching it yet, as the trim is still not perfect
field fix was to just jam it back and that worked fine for several more throws, but on return to base i removed the fin (easiest to undo the servo arm and you get the slack required to unthread the link at the rear), and trimmed off the covering as required on both sides, and used a tiny smear of 5 minute epoxy and a fillet of the same as reinforcement - solid as a rock now (pics 8 - 11)

the very rear of the pod got a hairline crack - i am not sure if this was down to unreasonable pressure when i was fitting the wing, which required a fair amount of force to align initially, or perhaps as a consequence of the leverage of landing
the fix was a smear of epoxy and a small patch of carbon fibre tissue internally (pics 12, 13), but for good measure i also added a small patch of reinforcing tape and the pod now feels significantly more firm for almost no additional weight

so, my thoughts so far are :
  • this is a fantastic introduction to mosquito class discus launch gliders
  • the quality of the kit is very high, and the price is great value
  • it has a rather delicate structure that may benefit from some pro-active modifications as documented
  • this is not a plane for windy conditions at all i think, though experience may alter that assessment
i'll post back here once i get in some more flying time with it
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Last edited by scruffy1; May 02, 2013 at 07:31 AM.
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Old May 01, 2013, 11:15 PM
looking up down under
scruffy1's Avatar
Australia, NSW, Fairlight
Joined Feb 2008
1,375 Posts
well, the day dawned sunny and almost calm but it took me till around 1100 to get to the field

on this occasion heeding the counsel of the product guide, i had added some weight to pull the cg forward, as per my discussion over at the unique model RC DLG thread which has been running for ages; my comment is on page 13 if you are looking there

"currently 12mm ahead of the front of the rear pylon, which is 64mm from the trailing edge, or 88mm from the leading edge

suggested cg is 80mm on the online assembly manual; might add a few grams at the nose and see how that helps - found a nice big hex nut that weighs 4.6gm which sits firmly inside the canopy using the magnet as "security", and cg is ~ 82mm

i'll start hunting for a 5gm ferromagnetic semicircle

found a 5.6gm ring (washer?) auw is 115.7gm on the accurate (0.1gm increment) scale - versus 111 without ballast on the kitchen scale (does only 1gm increments)"

sadly i failed to recheck the cg with plan b in situ, but i am guessing pretty much where the guide says, at 80mm back from the leading edge

and so...

with the ballast it flies so much more consistently than the tail heavy sortie yesterday

launches are easier because the added weight adds to the inertia of my hoisting; the controls are nice and crisp, and have good authority with adequate airspeed

the lateral balance is off due to the launch peg's weight - but it seems to make no great impact on tracking; the launches were easy and almost vertical, with the only inconsistency being due to my lack of experience; i didn't have any presets for the launch phase - what i throw is what i fly, and it tracks predictably true

i can't judge height, but suffice to say i think maybe 60-70' on the better attempts

the air was variable, as shown by the flights being from a single circuit to on a few occasions several circuits taking i would guess close to a minute to land

except one ! after a cumulus swept past the sun i launched pretty much straight into the light very nicely, nosed it down as before, and it went up like a balloon

three or four circuits later it was easily three times the launch height, and sitting in formation with a local swallow sharing the same lift

by the time i finished going woot ! i thought to look down at the timer, and guessed i had already been at least 30 seconds - the eventual flight time was around 3 minutes, and would have been longer except as i drifted downwind and ever higher i got a little paranoid about penetration should it really start to open up, and so pushed it back upwind but sadly failed to strike gold a second time... i recall that the bonsai has caught thermals on the same field, so when the lift is there it can easily get pelicans rising, and this thing is very lightly loaded

not too bad at all for my first "real" DLG session

between yesterday and today i spent at least 90 minutes (75 minutes today alone on the dx8i timer set for "stop watch"), the residual charge was 4.07v and recharge to capacity took 100mah, so the prediction of 6 hours safe flying time seems conservative, and means charging between sorties is optional; you could get a week of flying out of it unless you go out several times a day (then again, you might ! it's a lot of fun )

the down side ? the fuselage pod opened up the same crack as before, although the carbon tissue and tape prevented complete separation - this is definitely the weak point in the design, as the plywood end where the crack occurs; i note that the starboard rear glue join to the plywood has failed here too, which is quite possibly what has allowed enough flex for the failure - would be worth a tiny fillet of epoxy and microballoons as insurance for those yet to fly one ?

i intend to reglue it but this time using ultra lightweight glassfibre cloth as the grain in the weave is far superior to the carbon fibre tissue for "crossing" the split

given the weight distribution and likely impact on all up weight, i would be very inclined to actually glass the entire pod externally, or at least from the rear to the servo area - i may order a new pod and do that pre-emptively

the tail fin laughed off every landing, but about half of them were catches rather than grounding

the photos below are pretty self explanatory - the ballast ring was perfectly stable relying on the canopy magnet alone, even though the locking tab actually levers it up at the aft part - a D shaped ferromagnetic item would be the perfect choice (but where to find one ?)

hope that info is useful to any potential or current owners

feel free to chime in with questions or suggestions; my (major) work here is finished

i'll update with further modifications as i get around to them
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Old May 03, 2013, 12:09 AM
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Joined Feb 2008
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so i fibreglassed the rear of the pod internally

in doing so, i note that the carbon tissue was easy to delaminate from the interior of the pod, and thus was probably incapable of reinforcing it like i intended

problem hopefully solved by (easily) peeling it off the inner surface of the pod, and then keying the surface with a lot of scratching with a #11 x-acto and then some 120 grit sandpaper

one layer of glass perpendicular to the fuselage, and then another at a 45 bias to complete the deal, using finish cure epoxy in place of the 5 minute stuff for the carbon fibre

it is a real shame they skimped on the pod , as a thin shell of fibreglass would have been a much more durable choice

i figure i'll trace around the canopy for inspiration, and consider a slightly longer but glassed pod for a replacement project, if the current split recurs - my moulding skills are non-existent, but a balsa shell will suffice, plus i can modify the canopy to a much more aerodynamic shape if i desire
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Old May 03, 2013, 08:38 AM
looking up down under
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Australia, NSW, Fairlight
Joined Feb 2008
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the fibreglass at the rear has done the job - that and smaller separate pieces of the fibre tape externally, and it's good to go; took the opportunity to put the thinnest of smears of finishing epoxy on the elevator pylon to waterproof it

the pod now feels rock solid, but the truth will be revealed when i get to use it for a few more sessions

moved the elevator connection to the middle hole; the rudder is already at max throw from the refit (can't recall which hole it arrived in, but i have the servo set to 125% travel in addition, as i prefer tiny stick movements once i get familiar with flight behaviour)

upgraded the big ballast washer for a slightly lighter hex nut, as i soldered a jst connector to a spare servo lead for the battery to make it impossible to plug in the wrong way, and used double sided foam tape to secure the receiver to the pod floor so the aerial can run straight forward without getting bent by the battery pushing it into the nose when i fit it

all up pushed the weight to 117gm, but the nose weight might lose a few grams once i get more courageous at trying the cg a little further back
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Old May 03, 2013, 04:03 PM
Registered User
United States, OR, Portland
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Looks great! Tempted to get one myself
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Old May 03, 2013, 07:26 PM
looking up down under
scruffy1's Avatar
Australia, NSW, Fairlight
Joined Feb 2008
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Quote:
Originally Posted by fallingdown View Post
Looks great! Tempted to get one myself
for the money you can't lose

and stella is an excellent vendor

my only complaint today is that the discomfort in my right shoulder and right hamstrings attest to my lack or previous use

edit : and a further 45 minutes of launches this morning didn't help my aches at all - but i can confirm that fibreglass and tape have rendered the pod much more capable of surviving inelegant nose first returns to earth
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Old May 04, 2013, 04:48 PM
Full Scale Piper Cub Driver
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Joined Nov 2008
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Question about dealing with Aliexpress

Aliexpress does not accept PayPal. I don't want to sent credit card info. Who are these people that don't deal in PP?
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Old May 04, 2013, 05:40 PM
looking up down under
scruffy1's Avatar
Australia, NSW, Fairlight
Joined Feb 2008
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it's paid via escrow through a usa based company - i was brave enough

if you aren't keen, email stella and ask for an alternative

someone else on another thread managed to do the $ via paypal i believe, so it's possible to not give details

"Well aliexpress wrote me back, and gave me a Paypal address with which to pay for the yellow glider. I think that saying I'll just go order at HK made them sit up and take notice. So it looks like the original yellow order is on its way, plus the HK one, lol. I'll report back my thoughts on both when I get them.

I must say though, been vary happy with the communication from aliexpress so far. Might have to order more from them."


personally i'm not so paranoid - my card is covered for fraud anyway
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Old May 05, 2013, 08:45 PM
Full Scale Piper Cub Driver
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Got my order placed with Stella for the new improved model. She did an end-around so I could use PayPal. So far, so good...
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Old May 05, 2013, 09:12 PM
looking up down under
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Australia, NSW, Fairlight
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Quote:
Originally Posted by Piper J3 View Post
Got my order placed with Stella for the new improved model. She did an end-around so I could use PayPal. So far, so good...
you won't be disappointed

but a pre-emptive tail mod and fibreglass to the rear pod will be time well spent
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Old May 06, 2013, 02:22 AM
Full Scale Piper Cub Driver
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Quote:
Originally Posted by scruffy1 View Post
you won't be disappointed

but a pre-emptive tail mod and fibreglass to the rear pod will be time well spent
I'm going to copy your build and use the HK 1S LiPo.
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Old May 07, 2013, 05:58 AM
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a further 75 minutes of fun today - best flight 90 seconds thermal lift in 5-10 knot breeze

residual battery 4.07v

the pod repairs withstood a ground loop and quite a few fairly brisk landings and shows no injury at all - gotta recommend fibreglass in the rear area as a successful modification
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Old May 07, 2013, 08:24 PM
I'll Gladly PayU 2sday 4a DLG
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Old May 08, 2013, 03:35 AM
looking up down under
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Australia, NSW, Fairlight
Joined Feb 2008
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so, another session this arvo, and a few new discoveries

the most important was a reaffirmation that flying across the sun will likely ruin your ability to track the plane with potentially disastrous results

that, and sharing a field with soccer players and dogs, when it's too late for any lift (an hour to sunset in mid autumn...) is not really very intelligent, although gotta fly when you can

as it was i managed whilst blinded to fly the right wingtip into a star picket, but did minimal damage with a ding in the leading edge that thankfully buffed out using my trusted technique of pricking the covering with a #11 xacto and ironing the area while placing a wet tissue over the holes, and then using the covering iron - can't see it now

i noticed that the radio had lost its binding at some stage, and the servos were a bit feeble, but back home the battery read 4.04 (appropriately 404 like the binding )

anyways, dug in my bag of tricks and dug out a 1s voltage booster and plugged it between the battery and receiver, and the servos seem much more enthusiastic to swing

given that the big ballast washer is 5.5g, the hex nut is 4.7g, and the combined booster and battery lead is 4.9g (albeit situated a tiny step further aft), i am keen to replace ballast with similar mass plus the benefit of 5v - measured at 3.98v on the 1s gives 4.99v on the boosted output

this will doubtless diminish the duration, but on current readings (sorry for that pun) i think it will still last longer than my arm for flying sessions

photos tomorrow when the light is adequate, and hopefully good air to test out my further modification

other damage assessed :
  • the elevator platform "hook" had come a bit loose - again, victim of paucity of glue like the fin i think, and fixed with a minuscule hit of 20 minute finishing epoxy
  • i discovered a longitudinal crack in the carbon boom between the wing mounts, a result of torsion from the ground loop i would think - again, 20 minute epoxy to the rescue, which i let seep into the crack by twisting the boom to open it up; wiped off the excess and let it cure (still at it) crack down to let it exude onto the outer surface if at all
from my research epoxy is the best adhesive for carbon fibre, but anyone who knows better can post suggestions for everyone's benefit

more updates on my punishing testing regime as they eventuate
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Old May 09, 2013, 12:14 AM
looking up down under
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and the testing continues...

today was another 75 minutes in very light breeze; took out the digital anemometer and completely forgot it was in my pocket ah well, it was almost calm anyway

a single storm petrel (i think) caught a thermal just as i arrived, but he / she was higher than i could sling the plane, and downwind by the time i was ready to launch anyway

i note that the previous few sessions and some testing had drained the battery to just under 4v, and it took 135mah to return it to the full 600mah capacity; today's 75 minutes using the voltage booster managed to dip the post flight volts to 4.10v - i realise the transmitter is also burning electrons, despite the 4000mah lipo in my dx8 - beats the crap out of the nimh that came standard for duration even so

after around 3/4 of an hour with the new setup, i reinserted the 4.7g washer up the nose, bring auw to 120.2g with the volt booster and extra wiring (see photos); the volt booster won't fit in the bottom half of the pod, but some have suggested it heats up, so it sits unsupported in the upper part under the canopy - didn't get vaguely warm after an hour and a quarter of my use

epiphany ! the extra mass and slightly more forward cg transformed it from an indecisive floater to a much more grooving and only marginally faster flight pattern, but the real kicker was it hit an apogee easily 20% higher i still can't judge height, but waaaaay (!) up there compared to unballasted; the cg is now at ~78mm from the leading edge, and i will hunt for a 3g nut to see if that tweaks the trim

seems to me that optimal flying weight is > minimum possible, but maybe with a battery further up front and cg at 80mm you'd do a slightly better (as in slower on the same ratio) glide at the expense of a lower launch height

launching technique gets maximal height with maybe only half a pirouette and follow through; certainly the half turn and a gentle heave is both more consistent and routinely higher than an underarm swing alone (and far less tiring)

run up may help, but not that i've seen yet - i may just be too timid to really wind it out, but that can wait for the binary 900 which is more suitable to the stresses involved

transition from a good launch as described above is amazing - even without control input it just sort of falls nose down at apogee and grooves from there, akin to a good old chuckie launch

no thermals hooked, but several flights where i managed 2-3 large circuits before touchdown
and my arm and leg no longer complain after a session (or the next day) - improvement

repairs :
  • the crack in the boom is solid with the finishing epoxy, and the pod remains perfect despite some clumsy landings, and one sideslip into terrain on a too slow turn on approach... all good from that point
  • the only other finding was a small crack in the leading edge of the lower fin, that i intend to dribble some cyanoacrylate into for reinforcement - doesn't appear to have any effect on flying
pics below of the various injuries and repairs, and the latest power train

stay tuned
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