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        Build Log Horejsi Q11, 2m Composite Build Thread

#1 AndrewBurns Jan 11, 2011 04:17 AM

Horejsi Q11, 2m Composite Build Thread
3 Attachment(s)
So I'm now the proud owner of a Horejsi Q11, a 2m wingspan bagged foam and glass electric glider. The Q11 is a 'full house' bagged wing glider built much like a DLG using the famous Drela AG 44-46 aerofoil sections, used in Mark Drela's Agea glider and part of most DLG wings.

The primary thing that attracted me to the Q11 is its weight, at 300 grams empty it is essentially impossible to find a lighter weight 2m electric glider, especially with the accuracy of a composite skin wing. I already have a heavyweight 2m electric glider for high wind conditions so I'm aiming to make this glider at around 550-600 grams RTF to give me an edge in light to moderate conditions.

The first thing that struck me was how well the model was packed and shipped. I purchased the glider from Modelflight in Australia (I'm in Sydney) and it was wrapped in about 3 layers of strong cardboard and bubble wrap. The wings and tails of the glider were in bubble wrap sleeves and looked immaculate. The finish of the flying surfaces of this glider aren't your usual shiny molded surface, they have a dry matte finish which simply shows the lengths Horejsi have gone to with reducing the weight of the glider. The fuselage is very thin and lightweight, strong enough without being too strong. Similarly the wing spar feels quite strong to me, don't expect it to take a winch launch or any severe pull-ups but I can't think of anything you could do to it during normal flight to damage it. My component weights are as follows (all in grams):

Left wing = 94
Right wing = 93.1
Left tail = 9.4
Right tail = 9.4
Fuselage = 44.2
Tailboom = 17.3
Accessories bag = 30.1

Total airframe = 297.5 grams (10.5 ounces!)

I'm planning to kit it out with Hyperion DS09 servos and a lightweight power system.

The majority of electric glider competitions I've flown in have been LEG (limited electric glider), a limited motor run based event in which very high power to weight ratio is important for ~5 second motor runs however the prevailing wind in the electric glider world seems to be towards height limited events which favor more sensible power levels. I'd like to choose a power system with enough grunt for my LMR competitions but which won't leave my glider so porky that it would struggle in height limited events. The stock power package recommended by the manufacturer produces roughly 140 watts and weighs about 120 grams (motor, ESC and battery). I think I'd be aiming for around 300-400 watts at hopefully not much more weight. Two options I've considered so far are:

1) Neu motors Neutron 705 7400kV motor with a 4.4:1 gearbox on a 2S 900mAh pack and with an 11x4 prop. Estimated performance 280 watts out, 1.6Kg thrust at about 162 grams power system weight.

2) Hyperion GS2218-10 on a 2S 900mAh pack and an 14x8 prop. Measured 315 watts at a system weight of 166 grams.

It should be noted that the second system when put into the calculator I used for the first yielded significantly lower power than measured (via Hyperion's website) and so the first system is estimation is likely to be on the low side in power output. Does anybody have any experience with power systems like these or other higher performance power systems in the power and weight range that I'm interested in?

#2 Alex VK2KR Jan 11, 2011 04:55 PM

Hi Andrew

I see that you got a blue one, mine has red tips.

Made a mistake with mine, thought the firewall was to flimsy
(it is not) and backed it up with 3mm light ply. Spent a day
finding a place that stocked 10mm long 3mm screws so that
the motor could be mounted. Should have left it alone.

Where did you obtain the Neu motor/GB ? other than import
from OS cannot find a local source.

Good luck with the assembly



#3 AndrewBurns Jan 11, 2011 05:03 PM

Don't have the power system yet but last time I bought a Neu motor it was from Esprit model in the USA. The neutron is a fairly new series though so I might have to buy it direct from Neu motors.

Another motor option I was looking at this morning is a Hacker B20 12L with a 4:1 gearbox, looks similar to the Neutron but significantly more expensive and slightly lighter.

#4 Alex VK2KR Jan 11, 2011 10:48 PM

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Originally Posted by AndrewBurns (Post 17074956)
Don't have the power system yet but last time I bought a Neu motor it was from Esprit model in the USA. The neutron is a fairly new series though so I might have to buy it direct from Neu motors.

Another motor option I was looking at this morning is a Hacker B20 12L with a 4:1 gearbox, looks similar to the Neutron but significantly more expensive and slightly lighter.

Hi Andrew

Cannot find your Neu motor selection on the esprit website, but there are other
350 watt options there - at a price - grin.

The motor options I was thinking of are in the picture attached, these are for
the HL comp and therefore lower power 100-150W.

One on the left is a HC Hacker clone, then a slightly more powerful HC
KDA 28-15 (28-20 optional) and the 3900Kv version of the HC inrunner
with the Modelflight 3.3:1 planetary gearbox (most powerful option for me).

Been busy watching the floods on ABC24, Junior is OK but his workplace
next to the river in Brissy is underwater now.

Back to the build shortly


#5 AndrewBurns Jan 18, 2011 03:04 AM

I've decided on talking to Steve Neu to go for the Neutron 705/2Y motor with a Maxon 4.4:1 gearbox swinging an 11x4 or 12x5 prop, should be able to get the 300-400 Watts I want without much of a weight penalty. My battery will be a Hyperion G3 65/90C 900mAh 2S lipo, speed controller will be a stripped down castle creations ICE lite 50 (ICE because I want the logging capabilities, stripped down because it will be too heavy otherwise) and my servos will be all hyperion DS09's. All of this stuff is on order now and I'm waiting on most of it so I can do some trial balancing, hopefully I won't need to add weight.

Any ideas about what system you'll use to control the V-tail? I don't really like the included carbon pushrods along the outside of the boom, I'm thinking that a pull-spring system might be adequate but not sure if the hinges of the V-tail can handle the stress. Otherwise I could go with thin steel rods in bondable teflon tube outside the boom, should be less weight and drag than the big carbon ones.

#6 robh Jan 18, 2011 08:58 PM

Looks interesting Gents! On the LapDancer that I built, the carbon pushrods ran down the outside of the CF boom and worked quite well! I'd never built a sailplane before that had that setup, and was pleasantly surprised how well it worked.

Following with interest,


#7 AndrewBurns Jan 27, 2011 04:00 AM

Just a quick update, more pictures when there's actually more building to show (only just got back from a competition so I'll have more time now).

Received 6 x hyperion DS09 SCD servos, a Hyperion G3 45C 900mAh 2S lipo and a Castle Creations ICE Lite 50A ESC in the mail today. I've settled on the Neu motors neutron 705/2Y with the 4.4:1 maxon gearbox and either an 11x4 or 12x5 prop (the ICE speed controller with its data-logging capabilities will let me know which is best for my application). I'm going to use Aeronaut CAM carbon props and a 30mm 'cool-nose' spinner.

The hyperion servos are a snug fit into the servo cut-outs in the wings and my next step will be to sort out my linkage geometry and glue them in. I'll wait until my motor arrives before I cut the nose off the fuse and install the firewall, in case the bolt pattern of the gearbox differs from that pre-cut into the firewall. I also want to do a dry install of the electronic bits to make sure I can balance the plane.

Still unsure about the receiver, it needs to be at least 7 channel and compatible with my 2.4GHz JR DSX9 radio, I'm thinking either an AR7000 or AR8000, the 8000 has a channel I don't need but it looks smaller than the 7000.

#8 AndrewBurns Jan 29, 2011 12:49 AM

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This afternoon I glued in the plywood reinforcements for the wing bolts, attached the wing and glued on the tail boom.

The kit supplies you with two pieces of cut plywood to be used as reinforcements for the 4 plastic wing bolts. You're supposed to glue them into the fuse at the front and rear of the wing saddle. After you do that you're supposed to drill and tap them for the M4 screws. Before drilling the holes I dry-fit the boom and used a piece a string from the end of the boom to the wing tips to make sure the wing was on straight, I messed up one of the 4 holes as the drill bit 'walked' a little before biting but otherwise the wing went on well.

After I drilled and tapped the plywood I soaked the threaded hole with thin CA and tapped again, this helps reinforce the threads so that they last longer. They don't specifically tell you to do it in the instructions but I've seen it before in a hand launch construction video and it made a lot of sense.

Finally I fitted the v-tails to the boom and glued it to the fuse using epoxy, having the tails and the wing attached gives you something to align against.

#9 Alex VK2KR Jan 30, 2011 12:35 AM

Spinner size
2 Attachment(s)

Mounted the hacker clone motor in mine - finally
and only had 2 choices for spinners, a 29mm and a 32mm

The 29mm one allowed a lip on the fragile fuselage that would
scoop dirt on landing, or chip away, so used the 32mm
one. It is to large and looks worse in the image than

A 30mm spinner would have been perfect.

(waiting on the epoxy to set on the wing mount plywood

#10 Alex VK2KR Jan 30, 2011 05:21 AM

Red One
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Mine is red (not pink) and slowly being assembled.

Still waiting for the FrSky 2.4ghz module and receivers
from HK for the JR Tx.

Put in about 2 deg downthrust on the motor and a
smiggen of right as well - probably not a factor
with only 100 watts, it is just in case. I have to get
this finished in a fortnight ready for the postal comp.


#11 AndrewBurns Feb 08, 2011 02:26 AM

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My AR7000 and Neu motor arrived today, my life has become very busy again but I hope I'll get more building time in a week or two.

The first thing that struck me about the Neu motor neutron 705/2Y/4.4 is just how small it is, the motor really is way tinier than I was expecting! The Maxon gearbox hanging off the front is also positively miniature.

I weighed the motor and gearbox and they tipped the scales at 50.6 grams which is a lot less than I thought it was going to be, turns out this is because the Maxon gearbox listed on the Neu motors website is a larger gearbox for their larger 11XX series motors. Unfortunately I also bought my prop based on the data on the website and while that gearbox has a 4mm shaft the one that came with the motor has a 3mm shaft. This means that I'll have to get a 3mm shaft spinner, no big deal really just annoying. The gearbox is also far smaller than the supplied firewall was designed for and so I'll need to make a custom one (glad I waited for the motor before gluing it in).

So I'm happy with the motor, with the decreased weight I'll likely be able to get the plane flying around 550-575 grams!

#12 Neil Stainton Feb 08, 2011 05:17 AM

Thank you for your interesting build log Andrew.

The motor looks very nice, even if it is not exactly what you were expecting. BTW I guess the gearbox ratio of the box actually supplied is 4:1, not 4.4.


#13 Neil Stainton Feb 08, 2011 05:19 AM


Originally Posted by Alex VK2KR (Post 17254203)
Mounted the hacker clone motor in mine - finally
and only had 2 choices for spinners, a 29mm and a 32mm

The 29mm one allowed a lip on the fragile fuselage that would
scoop dirt on landing, or chip away, so used the 32mm
one. It is to large and looks worse in the image than

A 30mm spinner would have been perfect.

FYI Vladimir makes (and I sell) a very nice 30mm spinner


#14 lebenj Mar 31, 2011 08:07 AM


i have several questions about this glider.

- does someone can tell us how it fly??? :D

- i would also like to know if hyperion DS09 would feet in this glider (they are quite higher than other servos of this weight.

- is it easy to feet everything inside?



#15 AndrewBurns Apr 09, 2011 10:20 PM

5 Attachment(s)
Welcome back thread! Sorry I had to abandon this build for a while, pulled into other projects and my work life has become increasingly more frantic (I haven't found the time or energy to fly anything since the start of the year really).

Today I had some spare time so I decided to hop back on and get the servos into the wings. Now that I had my receiver I could properly set their neutral points and cut up the servo arms before gluing them in. You may notice in some of the pictures that the flap servo arms are trimmed with a 25 degree offset rearwards, this is to allow greater positive (down) flap travel for braking.

I had a little trouble getting the servo wires down through the holes cut in the wing so I drilled a hole in the wooden rib at the end of the wing segment to make it easier (I probably could have avoided this if I had more patience). I ran a thin metal rod down the hole and used it to fish the wires through the wing. After I had the servos hooked up I had to enlarge the servo cutouts a bit to fit the Hyperion servos which fit almost perfectly flush with the surface of the wing.

I haven't glued the servos in yet but I'll do that today. I need to figure out how to plug the wing halves into the receiver too, normally you'd use a 6 pin plug but that doesn't work for a 2 piece wing and I don't want to be plugging 4 cables directly into the RX every time I want to put the wing on...

Next step is to probably build a new firewall that can fit the tiny neu motor and glue that in, then I can try to do some preliminary balancing to get a feel of where I need to put the rudder and elevator servos.

Benjamin :

I hope the DS09's fit as that's all I'm using (wings and fuselage), I don't think it will be too hard as the fuselage is fairly deep and roomy but we'll have to see. They fit into the wings without much difficulty.

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