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Feb 12, 2019, 10:35 AM
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Harri Pihl's Avatar
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AD/HD - A very simple delta for indoor flying, combat, pylon, FPV and more

I don't remember exactly anymore how the original idea of the AD/HD came around... Anyway, we have been flying indoor combat here for years using many kind of designs like Depronker and others. Sometimes I was wondering if a pusher type delta could be a better concept offering simplicity of the construction combined with the motor in the safer place at rear. The idea never really materialized until some other stuff appeared in my hands... One day I bought a very cheap, less than €10, V9XX FlySky compatible brick from a chinese online shop, just to test it in a somekind of airframe. The Brick featured two servos and a brushed ESC and it was suitable for 1S LiPo batteries. Sametime I had a small QX90 size quadcopter which came with two spare 8,5x20mm coreless motors. Combined with the Walkera 55mm blades, this motor looked like good combination with the brick for a small pusher delta.

In the basic design I had just two goals, firstly it should be as simple as possible and secondly it should still fly well, like a profiled wing. Choosing a delta planform was an obvious choice given I've always admired sleek lines of deltas (starting from late 70s, models like the Graupner X1200 or Robbe Lanzet) and deltas tend to have good lateral and longitudal stability. However, to keep it simple, I was destined to make a sheet type wing and generally I don't like how the flat plate airfoil behaves. Now, my Friend Pekka Kangas made few years ago a series of higly cambered flying wings called "Kumma Lätty" (literally translated as a "Odd Plate" or "Strange Pancake"). The Kumma Lätty wing was basicly a depron sheet bent to have large amount of camber and in the trailing edge there was some reflex, there are several other similar models but it was Pekka's one which gave me the inspiration. So to make flat sheet behave a bit like a profiled wing I just added some camber, not as much as in the Kumma Lätty as I was not interested about high alpha flying. And to keep it simple, no reflex but control surfaces few mm up instead, this is also good strenght wise as camber makes wing stronger. In the delta planform the result is decreasing camber as well as increased local angle of attack towards the wing tips. However, there is no need to afraid tip stalling because the delta shape and vortices. I avoided sharp and vulnerable wing tips by by cutting last few centimeters off. The fuselage shape gives the camber to the wing and I also designed fuselage so that there was some space between propeller and the trailing edge to avoid noise. Lastly I added a relatively large vertical stabilizer to reach good directional stability.

Building the prototype for test gliding without equipment took less than 15 minutes and I aproximated centre of gravity and control surface reflex by test gliding. Actually original idea was to have somewhat rounded corners in the wing to reduce vulnerability but during cutting I just thought"#### it, easier to cut when the lines are straight". The prototype wing and vertical tail are depron (esktrupor) and fuselage EPP. There is only one glue joint in the basic construction ie the wing fuselage joint, the vertical tail goes to a slot. The elevons are taped and control horns and pushrods are from carbon rod with heat shrink tube joints and z-bends in the servos. After test gliding I installed the gear; brick, motor and 1S 150mAh lipo battery (took something like 40mins), proto came out at all up weight 27g. Total costs of the all materials including brick, motor, prop and battery for the proto were less than €20.

So then it was time for the first flights... After few gliding attempts the test glided CG proved to be too far back and couple screws were added to nose, few attempts more and after little forming of the wings by hand it suddenly started to fly. And it did fly well, lively, agile and fast but still surprisingly stable in all axis. Later I moved the brick forward to correct the CG and the rest is history; others were impressed how the little thing was flying and they started to build their own variants... Also that time I once talked with my fellow modeler Vesa Jokinen about life, flying and Zen and I got an idea call this little delta as ADHD due to it's hyperactive characters while Vesa followed with an idea to write it as AD/HD to distinguish it from the mental disorder (and because the AC/DC too...).

Now, two years after the first flight of the proto AD/HD, tens of variants have been built locally at various sizes varying from 40cm to 125cm and even bigger ones are planned. It has been used indoor, outdoor, combat with streamers, pylon and particularly for FPV, I've even flown a 60cm variant at the slope... Construction is very simple and wide variety of materials as well as large variation of gear has been used on various incarnations of the AD/HD, more about that later. The small variants are by far the most durable indoor models I've seen, you can litterally hit directly to the wall without major damage. The developement of FPV variants is mainly done by Mikko Turunen and Hannu Rutanen and Hannu will post about FPV variants later in this thread.

I think that the AD/HD is my best design so far. There is nothing really original in it, however, I consider the AD/HD as a sound combination of various proven ideas and also as a good platform for experimenting new ideas. It's not rare to see ten or more AD/HD related models in our indoor flying sessions in Laukaa and overall it has given whole new breath of fresh air to our modeling community.
Last edited by Harri Pihl; Feb 12, 2019 at 11:01 AM.
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Feb 12, 2019, 02:45 PM
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First post to here ever.
Hi everyone! I'm Hannu, a friend or Harris' and a fellow AD/HD pilot and I've been a hobbyist since the year 2000. I remember the time when Harri flew his prototype at Laukaa gym hall some 2 years ago
Harrin pieni delta (2 min 0 sec)
(not sure if I was there that day). But it sure left a mark in me which grew onto me eventually.

It was only last autumn when we had opened out indoor season in Laukaa yet again. I was kinda busy then, so asked Harri to make an ARF for me. Since I was using FrSky Taranis and wanting to use the internal module I had to resort other gear than the brick. Thougth to go with FrSky VD5M 5-channel micro reveiver, HK-282A servos, TURNIGY MULTISTAR BLHELI_32 ARM (with 1A BEC to run the servos on 5V) and for motor TURNIGY A1309-7500KV with GWS 3020 propeller, 2S 180mAh for battery, all components lightened ( scrapped stickers, changed wires to save weight etc).
Unlike Harri I sanded the leading edges and beveled the trailing edges to reduce some induced drag. I ended up taping the leading edge to strenghten them since they were really prone to snap and twist on sharp impacts (ie. door frames, table legs, you name it). Putting some time and effort on the leading and trailing edges gave me one small improvement; inbuilt EXPO! It flew on rails and responded gently but sharp on control inputs. No much trimming needed on the maiden flight either. Other differences with the proto was shortening the tail fuselage to match with the end of the wing enabling less nose weight to be used, even you'd fit the gear to fit you CoG. My first one was 45 g when it was finished, all ready to fly.

It was about the same time when Mikko had made his first AD/HD variants and put a 4 gram FVP-camera-VTX-combo to it. Being into FPV for a few years already I had to follow and taped a 4 gram Cam-VTX-combo into my fresh just maidened AD/HD . Boy was I exited, newer had I had such a fun experience. Light micro indoor FPV-platform with a wide envelope to play with! We had flown gates and tracks with TinyWhoop-drones earlier and had a track with a few gates that time too so obviously I had to try to pass a gate! AD/HD 50 FPV weighted now 50 grams.
AD/HD-FPV Indoors (8 min 2 sec)

On the next Saturday evening we were flying through the corridor because it just had to be done both ways! Corridoring starts at 4:30
ADHD FPV indoor flying in Laukaa (7 min 59 sec)

Group flying! The more the merrier!
ADHDt salissa (12 min 59 sec)

And having a head tracker module on your FPV-goggles of course you need to have pan&tilt for your camera on your AD/HD! 60 cm with 2S 300mAh battery with AUW of 85 grams it behaves quite like the smaller ones, only milder. Pan servo is fixed to the fuselage with a plywood piece to the servo arm and pitch servo is glued onto the plywood piece. Camera is fixed to a piece of carbon spar which is attached to tilt servos arm, super simple.
AD/HD's with head tracking (10 min 23 sec)

Flying other models sure made me miss rudder so I gave rudder another try on my seconds AD/HD. Like in the earlier I glued a 1.9 g servo in front of the fin and cut and hinged a flap for the rudder. The first version of the rudder was way too powerful, had to cut the throws down to 66% and it still was very effective inputting a great deal of roll to it.
The second version I made the moving part 1/3 smaller than on the first one, 15mm on top and 20mm on bottom, and it worked out quite well! It still induces some roll on slow speeds but on greater speeds it works just fine. and makes aiming in those narrow spaces much easier!

Harri's been known for his special; inverted low between own legs. AD/HD flies as well on its back like normally, though on FPV it's another story, really confusing. Maybe I'll pull out his special on FPV one day

Harrassing some local tinywhoopers at their session
Among the Mobulas (3 min 58 sec)

If you haven't tried an AD/HD, you should. No excuses, you should! No matter if it is 40, 50, 60, 80, 100, 125 or your own size go and make one! Or several!

Edit; added the fixed plan.
Last edited by Keppis; Dec 05, 2020 at 05:55 AM. Reason: Fixing image description errors
Feb 13, 2019, 05:42 PM
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I’ve followed this on YouTube for a bit.. these look like sweet fliers! I wanna make one to bash around the yard!
Feb 14, 2019, 01:13 AM
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Harri Pihl's Avatar
Thread OP
Some limbo with the proto AD/HD loong time ago:
Feb 14, 2019, 03:44 PM
flyin' fool
goldguy's Avatar
Wonderful design, will post link over in the scratch build forms.
Last edited by goldguy; Feb 14, 2019 at 03:51 PM.
Feb 14, 2019, 05:01 PM
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Harri Pihl's Avatar
Thread OP
Thanks goldguy, I really had a difficulty to decide which forum is the correct one for the AD/HD. Eventually chose this but scrath build or indoor forums would had been just as good.
Feb 15, 2019, 04:50 AM
Registered User

Let's build

Thought to add in a some sort of building log and more detailed instructions.

Materials needed:
- for 40cm and 50cm versions 3mm foam board (aerofoam, debron, EPP), 6mm for 60cm and bigger
- 0.5mm*3mm*440mm carbon strip (can be 1mm*3mm*500mm too), 40cm version does not necessarily need the carbon spar
- 15mm foam for fuselage (packing foam sheet, EPP, similar)
- 0.8mm or 1.0mm plywood (or similar) for firewall and control horns
- 0.8mm or 1.0mm carbon fiber rod and 0.75mm or 1.0mm pianowire ans small heat shrink tube for pushrods
- good tape, colored or clear for hinging and reinforcing the leading edge and covering the whole thing if desired.

Electrics suggestions:
- around 2 gram servos (HobbyKing HK-282A)
- around 2 gram receiver
- lightest possible ESC: TGY Plush 6A (lightened to less than 4 grams after changing the wires), Multistar or Yep 7A with separate BEC 1A minimum (Camera-VTX, receivers and servos might not be able to handle direct 2S current)
- around 3 gram motor (AP-03 4000-7500kv) easy to install and replace or similar
- 3020 GWS- style propeller or similar suitable one
- 2S 180mAh battery, 10 to 14grams. Or a 2S 300mAh battery.

Optional FPV camera-VTX-combo 3.35 to 5 grams.

All up weights:
- original 40cm (~15.7") 25grams
- 50cm version (~19.6") from <45g and around <50 grams on FPV-version, full taped wing 60g or more.
- 60cm version (~23.6") starting from 85grams on 2S 300mAh battery (FPV with 2 additional servos for pan and tilt)

Let's build!
Measure and cut the wing out of sheet but do not cut the elevons out yet. Glue in the carbon spar into a slot with Gorilla glue or UHU-Por (or similar) and ensure straightness. Leave to dry and cut another wing for a friend while you wait
Sand the leading edge rounder and taper the trailing edge of the elevon surfaces from the bottom side, you can also squish the leading edge and trailing edges making the foam a bit denser. Add thin coat of glue (Uhu) if needed to make the tape stick better around the leading edge. You can also use Zagi-tapes for color. Cut out and bevel the elevons and hinge with tape, also add a carbon reinforcement and tape on the center part on the back of the wing preventing the non-elevon part from snapping along the line later. Also cut the hole for fin extention.

You can slap everything on the fuselage either after gluing the wing on or making a cleaner installing by hiding the wires into the fuselage, it's completely up to you.
Cut the fuselage in shape. Place the servos in front of the CG, the point where the tail fin starts.
I like to make a groove on top of the fuselage for the wires and for the ESC so they're in nicely. You can make a small hatch on the side of the fuselage for motor wires. Some like to solder them straight on the ESC pads, some like to make connectors ie. from female SIL socket row or a servo connector or a similar. As long as it is light. This makes it also quicker to switch motor if it happens to break.
Make a slot or a hole for the receiver, which connects with the groove for the wires. After the wing is glued on (it's important to bend the front part of the wing for both strenght and aerofoil) screw or glue the motor in the plywood firewall and glue it on. Check CG by placing your battery and receiver and possible FPV gear to their supposed places places and make fittings.
Note that the firewall needs to be glued flush with the wings top surface so it lines smoothly with it, also add a carbon reinforcement to the bottom part on the fuselage, this prevents it from twisting.
The battery can be installed in a hole on the fuselage or you can make a slot for battery on the bottom of the fuselage and glue side cheeks and make a battery bay. Tight fit or secure in place with tape, which ever method suits you best.
Note that the motors thrust line should be almost straight with the fuselage. If you made your fuselage with foam it's easy to adjust, just gently bend it to correct position.

Make pushrods from 0.8mm or 1.0mm diameter carbon rod with L-bend wires, secure with heat shrink or small tube and a droplet of cyano. You can use Harri's heat shrink tube method or Z-bends too if you like, EZ-connectors are heavy.
Make the control horn end first, easier to start with the control horn not glued into the elevon. Glue horns to place, check symmetry on the control horns. Preset elevons on half of the thickness of the foam (well, about 1mm) up while servos and servo arms are centered. Add a small droplets of CA to the to the heat shrinks on pushrods to fix them to correct lenghts and elevon positions.

The vertical fin goes into its slot, it stays put even without glue. If it gets loose you can secure it with a a bit of tape.

If you did not sand the leading edges and trailing edges you might want to add in a bit of expo, but if you did you're totally fine without it.

Rudder mod!
AD/HD turns well with just its elevons but rudder takes it to a whole new level.
You can easily add it later on your AD/HD, just take the fin out, cut out the rudder (20mm on bottom, 15mm on top or a bit smaller), bevel and hinge it. Make a small control horn and glue iton. Slap a servo (HK282A or smaller)on the wing in front of the fins position and make a small hole for the servo wire. Make the pushrod and you're done.
Last edited by Keppis; Feb 15, 2019 at 04:57 AM. Reason: Typos
Feb 15, 2019, 09:29 AM
flyin' fool
goldguy's Avatar
Hummm? Hyperactive and can slope too. Ya' got me.

We cancelled our indoor tonight because of the weather, so another week to turn one out.

Too many projects on the go already, but this design is a 'must have right now'.
Feb 15, 2019, 09:37 AM
flyin' fool
goldguy's Avatar
Snow is a rarity here in the winter and we got over 50cm of it in two days. I'm sure in Finland you take in all in stride.

It's a total disaster if we get even 10cm.
Feb 15, 2019, 10:56 AM
Registered User
Originally Posted by goldguy
Hummm? Hyperactive and can slope too. Ya' got me.

We cancelled our indoor tonight because of the weather, so another week to turn one out.

Too many projects on the go already, but this design is a 'must have right now'.
I know the feeling, but I somehow tend to find the time for the most fun projects so I bet you'll find yourself doing a few pretty soon

And about snow, it's currently melting due a warm wave, we just had some 50 cm of snow but it doesn't stop the society from working but it makes some people hot headed, since you cannot find place to shove the snow into and then it snows even more
Feb 16, 2019, 02:57 AM
Quad and foam adept
Hermani's Avatar
Originally Posted by goldguy
Snow is a rarity here in the winter and we got over 50cm of it in two days. I'm sure in Finland you take in all in stride.

It's a total disaster if we get even 10cm.
Two snowflakes meet up in the sky. One asks: "What are you going to do?" "I'm going to all our friends in Austria and have a ball. And what are you up to?" - "I am going to Holland, fall down and have a lot of fun spreading panic"
Latest blog entry: WoodQuad
Feb 16, 2019, 06:01 AM
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Harri Pihl's Avatar
Thread OP
Originally Posted by goldguy
Hummm? Hyperactive and can slope too.
I did fly my 60cm variant in slope, I could easily stay in lift without power and make rolls and so but given the weight, about 75g, there was basicly no inertia for any vertical maneuvers. However, we are planning to make a 80-100cm EPP variant with carbon spars, laminate film covering and weight somewhere around 300-500g. The AD/HD glides surprisingly well so it might do fine on the slope with relatively vertical lift but don't expect it fly like a dedicated slope wing.
Feb 16, 2019, 05:20 PM
flyin' fool
goldguy's Avatar
Well, I sloped a cardboard NutBall and it flew amazingly well. But, it took big wind and a load of lead ballast.

To be fair, at this location you could slope your lawn chair.
Feb 17, 2019, 05:14 AM
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A bit larger one flying in sports hall of Laukaa.
ADHD 125cm (0 min 30 sec)
Feb 18, 2019, 05:57 AM
Registered User
Others go for bigger, I thought the opposite way Thought to give a try for 30 cm version because why not.
I finally got a brick that works with my Taranis (Oversky MXL-RX62H V2), thanks Harri
Goal is to get this around 20 grams in FPV. Gotta think of replacing the battery too, 250-300mAh HVLiPos weight around 6 to 7 grams a piece, could easily save a few grams here.

Got parts cut out, got some sanding to do, 6 days till next indoor session.
3 mm Aerofoam for wing and fin and 6mm EPP for fuselage. Or should I change the wing and fin for 2mm EPP sheet too, though foam is more rigid here.

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