The X-Ray

(X=Manta, Rocket, or Blade)

aka electric Mongo Jr

Electric Flying Wing with Pan and Tilt Color Video Transmitter plus Audio

Rocket Ray

The Rocket Ray was created to expand the range of space that I could fly aircraft in. Normal R/C flying requires that you be able to see the aircraft attitude at all times. I wanted to go beyond that. The Rocket Ray is the brushless motor version - climb out is more like a rocket! The Manta Ray was the first version and was inspired from earlier development of the vidcam xmtr on an electric Zagi (before Trick came out with the Zagi 400). I wanted something that could stay in the air longer and could carry a heavier payload.

Blade  Ray

Blade Ray - The Latest version. Double carbon spars in each wing wth 1/16" ply bridge pieces inboard and outboard - ultra stiff wing. Weight with MaxCim motor, 18 - 1800 maH cells - 106 oz. This version has slightely wider span - 78". I used the TU-03A spars for the top, and a K75 Glaspar tube for the bottom (got at Tap Plastics in El Cerrito). I recommend the TU-03A's for BOTH top and bottom. The bridge pieces are 1.7"x4"x1/16" ply (make 2) on the inboard and 1"x3"x1/16" (make 2) on the outboard. Spars are centered in the wing. I cut the slots in the top and bottom by marking, slotting with a knife, then gauging out with a needlenose plyers. Then epoxy in the spars. Use a hack saw blade to cut slots on either side of the spars inboard and outboard. Coat the ply pieces w/ epoxy and shove into the slots. Used 2 more 1.7" tubes of the Glaspar, mounted 1" and 3-1/2" from the inboard edge of the wing, on the frontside of the ply piece, as guides for the center bolts. I used 3 pieces of 2" wide bidirectional strapping tape, one down the middle over the spars, then the other two forming an X (opposite corner to opposite corner) top and bottom. Then installed servos, antennas, rcvr, then covered w/ red packing tape. Put the Al foil on last, after you heat shrink the tape. Then do the elevons. Watch out when drilling the front holes - don't drill through your electronics!

Span -75"
Wing Length - 16.5"
Velcro folding tiplets for easy transportation (none on Blade version)
Detachable wings
Modular construction
Area - 1120 sq in (including elevons)
As you see it top image above fully loaded w/ vidcam xmtr, 18-2000maH cells - 116 oz.
Without motor,batteries,payload - 32 oz
Wing loading - 15 oz/sq ft
Rocket Ray
Thrust w/ 13.5x7 prop, MaxCim MaxN32-13D w/ Maxu35B-21 controller, 3.7:1 gearbox, 18-2000maH cells - 94oz (from Motocalc)
Rate of climb full throttle - 1152ft/min @ 36degrees
Battery time full throttle - 2:01
Typical flight time no wind - 15 minutes
Cruise - 37 mph
Max level speed - 62mph
Amps - 59A
Prop speed - 8260rpm
Thrust w/ 12x8 prop, Aveox 1406/3Y, 3.7:1 gearbox, 18-2000maH cells - 78oz (from Motocalc)
Rate of climb full throttle - 900ft/min @ 27degrees
Battery time full throttle - 3:23
Typical flight time no wind - 15 minutes
Cruise - 36 mph
Max level speed - 54 mph
Amps - 35.5A
Prop speed - 8400rpm
Manta Ray
Thrust w/ 12x8 prop, Speed 600 Turbo BB 12v, 3.6:1 gearbox, 18-2000maH cells - 43 oz (from Motocalc)
Rate of climb full throttle - 380 ft/min @ 11 degrees
Battery time full throttle - 7:44
Typical flight time no wind - 15 minutes
Cruise - 35 mph
Max level speed - 40 mph
Amps - 15A
Prop speed - 6300 rpm
Thrust w/ 15x9.5 prop, Speed 600 Turbo BB 12v, 3.6:1 gearbox, 18-2000maH cells - 57oz (from Motocalc)
Rate of climb full throttle - 620 ft/min @ 19 degrees
Battery time full throttle - 4:53
Typical flight time no wind - 11 minutes
Cruise - 35 mph
Max level speed - 50 mph
Amps - 24.6A
Prop speed - 4700rpm
Stall - 18 mph
Min sink - 188 ft/min @ 5.7 degrees
Video Transmitter with Audio specs:
115 degree wide angle color CCD
5V 80 ma
Weight approx 1 oz.
Panning range - +/- 120 degrees operated by modified S3003 servo on flap trimcontrol
Tilt range - 80 degrees operated by standard HS-80mg servo on rudder control
Cartridge mike w/ opamp preamp
Freq range (xtal controlled) 420-450 Mhz (70 cm ham band)
Power output - 1.2W @ 14V (min - .5w@ 9V)
Range: Rcvr system dependant, but roughly 1 mi w/ just ground plane antenna (See pix below).
Preamp adds 10 db, 5 element Yagi (plans included w/kit) gain 9-10db
Two coaxial 6.3" antennas mounted at right angles with Minicircuits PSC-2-960-1W power splitter
2 - 9V 150mah NimH - weight 3 oz or
12 cells 300mah NiCd - weight 5.5 oz
Power- 270 ma @ 14V
Typical - 10-15 minutes on Nimh (warm)
45 minutes on 300 mah NiCd
Weight of entire pod with SIG CM14 canopy - 10 oz.



The Rocket/Manta Ray is made from the Mongo Jr flying wing by BASH Enterprises. I've made a few modifications, including carbon/glass spar tubes down the top center of each wing half. These are TU-03A 0.4" tubes from Aerospace Composites. If you read the original posts, you can hear the amusing stories of how the Manta Ray got its name. Ok, the short version is - when I put it in a dive (this was with weight of 96 oz) after about 2 hrs of soaring and powered flight on a warm day, it started flapping - "whap,whap,whap" - I was able to pull it out, but one wing was clearly "bent". On final approach, the plane entered ground effect, but as it was still going too fast, I raised the nose, flew over several pilots head, where it again "flapped", then shoved the nose down for a "perfect" landing. After that, I put in the spars. I also use BASH's 2D strapping tape (this is the 3M stuff) (fibers run in both horizontal and vertical directions - comes with kit) to completely cover both wings.

I've tried a number of motors in the Manta Ray. For low cost, the Manta Ray is powered by a Speed 600 BB Turbo 12v motor, with a Model-Air Tech H-500 MKII 3.6:1 gearbox. NOTE: This should require re-timing of motor, but I've found it doesn't really make much difference, so I don't bother anymore. I've invested more effort in putting an aluminum heatsink/bracket around the motor (not seen in these views). I've also used a Master Airscrew 3.5:1 gearbox (MAT3035G - Hobby Lobby) which doesn't require retiming (since gearbox reverses direction), but they typically only last about 5 hours flight time.

Rocket Ray

For sheer power and MAX fun, I highly recommend the MaxCim MaxN32-13D w/ Maxu35B-21 controller (includes BEC) and the MaxPlanet 3.7:1 gearbox. The power is AWESOME. The MaxCim controller will also drive Aveox brushless motors. The big plus of this controller is current limiting. No more burned up motors - no more burned up controllers. The limiting prevents any prop combination from overdriving the controller, which you can tell by an LED on the controller. I've also used the Aveox 1406/3Y with the 3.7:1 inline gearbox and a M160 controller. I bought mine through Tom Hunt at Model-Air Tech and saved 15% off list.

With the brushless motors your flying a rocket ship. I'd swear the angle of climb is more like 60 degrees. Flight gets a little yawy at these high angles of attack. I have to keep the stick forward a bit at max throttle, or the bank angle gets steeper and steeper until it's climbing straight up, stalls, and flips over. With a big enough prop, thrust>weight, so you may be able to overcome this, but watch out for overdriving the motor! The 900 ft/min is WAY conservative. Setting the vidcam to point at the prop I've watched climb outs and would swear I've climbed 1000 feet from take off in 15 seconds - yes that's 4000'/min! Well, ok, it's really more like 1500' but hey, watch the video and decide for yourself!

Prop is either a Aeronaut 12x8 folding prop (HLAN3450)or a 15x9.5 (HLAN3470) for higher thrust (but more drag when soaring). Motor, blades, yoke (HLAN4222), and yoke adapter (HLAN2411) from Hobby Lobby (exceptional service, ask for Tommy Smith) and Franciscan Hobbies (415-584-3919) for motor and Ultraplugs and Sheldon's Hobbies for AstroFlight speed controller 204D, although I could have used my 217D. Sheldon's also has a pretty smokin deal on the T6XA sets, which come with 4 S3003 servos and 7 ch rcvr. The tiplets are velcroed into place, both for transportation and for flight. I also often fly the Manta Ray with 18-1100mah cells, which reduces the battery weight by half (knocks about 1-1/2 lbs off weight). Flight times are also cut in half, but on thermally days, or with any lift, this gets extended greatly, and often I can fly power off for long stretches. Landing speed is reduced, too. The larger prop tends to always spin, even at the slowest speed, generating a noticable amount of drag. But the smaller prop will stop and feather, so it's ideal for soaring. The brake on the brushless controllers stops the prop REAL fast, so this isn't a problem with the brushless.

I use a Hitec CG-335 to charge my batteries.

Manta Ray in transport mode

Manta Ray in transport mode with tiplets velcroed down

The wing halves are held together by 2 pieces of 1/16"x12" wide birch ply, the bottom piece having the engine mount in the rear. There is a 2.5" gap between wings for the speed controller and the motor batteries. The first versions of the engine mount were birch ply, with fiberglass cloth and epoxy over the entire mount. Now I use a piece of sheet aluminum, bent around the motor and bolted to the base with 4 6-32 screws and nylock nuts. I also have an additional piece of copper sheet under and around the motor, but I don't think this is really helping much. The motor is attached to the belt drive (Model-Air Tech H-500 MKII). Make sure the motor is TIGHTly coupled to the plane. I've had it fall out on me 5 times already from not attaching it firmly or using a wire safety. Battery access is through the nose or "mouth" and is velcroed. The payload pod is also velcroed into place, and the canopy is velcroed onto a sheet of 1/32" ply 3.5"x12". Lately I've been flying the plane without the canopy. The view is MUCH clearer.

Vidcam pod

Wide angle color video camera with pan and tilt servo, 440 Mhz xmtr, microphone w/ preamp, batteries

The camera is a Panasonic GP-CX151-15 color CCD camera from Industrial Vision Source (800-627-6734 ext 6614 Phillis) with a 115 degree wide angle lens, mounted on a modified Futaba S3003 servo. I have also a small stock of these cameras available - so e-mail me if you want one. I cut the top and bottom servo pot lead traces on the PCB and inserted a 4.7k resistor in the high lead (not ground) and 2.2k in the lo (ground) lead. I used 1/8w resistors. This increased the travel to +/-120 degrees. I use a Futaba T6XA transmitter, and set the travels for 86% for the +120 degrees, and 73% for the -120 degrees. If you go more than about 120 degrees, the servo will keep turning, grinding the plastic notch on the servo pot. Reduce the gain to prevent this.

Lately I've added a tilt servo using a HS-80mg mounted flat against the pod, with a circular servo arm clipped and taped to the panning servo. I now use the flap trim knob to control panning, and the tilt servo is connected to the rudder. I set the rudder so that with trim full over and rudder full over, the servo aims the camera straight forward. With the rudder back to center position, the tilt is about 30 degrees. With the rudder trim this can be moved up to about 50 degrees, then rudder full over extends it to about 80 degrees. I find the 30 degree view is ideal.



In flight

Velcro tiplet detail

Receiver setup

Receiver set up

Receiver system:

Receiver is a portable 13" Panasonic PV-M1367AD w/ built in VHS recorder and 12v DC or 120 AC operation. DC power draw in typically 6-8A. I use a 14Ah 12v Lead Calcium (weight 14 lbs) battery in the red carrying case behind it. I cut a hole in the box corner so that an extensible pole can mount right to the box. The bottom of the pole fits into the corner of the foam in the bottom of the box. I also cut some carrying handle holes and put some velcro on the lid. I also have a set of black plastic glare guards that velcro to the TV made from a piece of 14"x48" thin plastic (Tap Plastics). The extensible pole goes up to 11' in 3 sections. The simple ground plane antenna was made from a BNC connector, brass sheet and 3/32" brass tube - plans from North Country Radio (also source of miniATV xmtr). (ground plane antenna and pole not shown)

Although the simple ground plane is simple and quick to set up, the best configuration I've found so far is using a pair of Yagi 5 element antennas (design also supplied by NCR). They are made with 3/32" brass rod and PVC pipe, oriented so that each antenna is 90 degrees rotated from the other, and their signal is mixed together with a signal splitter (Radio Shack or video supply). The antennas are connected together with the PVC pipe and mounted on a camera tripod. I point the antenna either straight up or angled generally in the main direction I'll be flying. The 5 element Yagi still has a wide capture range - you'll still get signal when the plane is 90 degrees off axis. But it has MUCH higher gain in the forward direction - you'll get a much clearer signal. This setup is what is shown above. Shot taken at the Berkeley Marina.

Transmitter system:

The transmitter is a kit made by North Country Radio, the miniATV and is designed for the 70cm (440Mhz) band, which conveniently is the only ATV (Amateur TV) band that has channels which coincide with cable channels on regular TV receivers (cable channels 57-60), so if you have a portable cable ready TV, you're ready to go. It puts out up to 1.5w (at 15v). A 9V alkaline battery will work, but a NiCd 9v (really 7.2v) is too low. I currently use 12- 330mah cells (to 6 cell packs in series) to get 14-15V. With the camera, this will last about an hour. The output of the transmitter is routed via RG-174 cable and SMA connectors through the carbon spar on the right wing out to two coaxial 6.3" antennas mounted at right angles with a Minicircuits PSC-2-960-1W power splitter. One is run along the leading edge, the other up the winglet. By having the two antennas, I get pretty much complete 360 degree signal coverage, despite power being cut in half. I also ordered ALL the available crystals - it's quite likely if your in a metropolitan area (like here in the SF Bay Area), that one or more of the channels will be in use at any time, so with the xtals you can change the channel - just make sure you use a connector on the xtal so you can switch them.

In the plane pix you'll notice the aluminum foil - this is important! The foil covers the servos and servo leads on both wing halves. The top clamshell piece also is covered (on the bottom) with Al foil. This creates a shield to reduce the interference between the xmtr and the R/C rcvr. It's not perfect, but it GREATLY reduces the interference. MAKE SURE YOU CHECK FOR INTERFERENCE BEFORE FLYING! Do the first tests WITHOUT THE MOTOR BATS CONNECTED!!!! Turn on the R/C xmtr, the plane rcvr, THEN the ATV xmtr. If you hear a click-clicking sound coming from the servos, and they are hunting (wiggling) - you've got too much interference. Try moving the antenna cables around. Check to make sure there is electrical connection between the top clamshell and the wing halve foils.

Everything on small luggage cart for hauling to launch site

Luggage carrier wheelbase is really too narrow - but it was one I had around.

Launching from Vollmer Peak


I have the R/C xmtr hanging from the supplied strap, hold the xmtr in my left hand and the plane by the motor mount end in my right hand, holding the plane overhead. Usually take a few steps and give it a good shove at about a 10-20 degree angle. Then shove the stick to full throttle. (It's REALLY important to throw first, THEN hit the throttle). Launches usually go a LOT smoother than with the electric Zagi of my design. Watch out for warm days, no wind! It gets a LOT harder to launch. I suggest a high-start for no-wind days.


I've flown it up to 3000', out as far as 5000', (at this point it's pretty much a speck), and flown by video at these ranges. It's easy enough to fly by video - if you've ever flown in the cockpit of any aircraft you'll immediately make the leap. The scary part is when you loose video (from interference, usually) - then you have to reacquire the plane by sight and it's easy to loose track of where that is in the sky (even though you may know where you are in the frame of reference of the plane!). I usually just take my hand off the stick and wait and scan the sky - and the image comes back usually in a few seconds. Having a spotter to always keep an eye on the plane is ideal.

Loops are a piece of cake - just don't try to make them too tight, or one wing will stall and it'll snap around. Rolls are done just like without power - they're just easier WITH power. Inverted is relatively easy, but watch out for exit maneuvers that get the plane in a steep dive. Do inverted flights the first time with PLENTY of altitude, and over somewhere that you can recover the plane. Power off attitude is just like with power - there's none of the nose dropping problem I had with my electric Zagi. The brushless motor generates so much lift the angle of attack will increase until the plane will flip over by itself after a few seconds unless you keep the stick forward at full throttle. I usually use 1/2 throttle for climb outs.

In general, in flies like it's on rails - hands off flying for turns or straight ahead flight. Thermals easy - tracks the cores without falling out once your dialed in. There is some tendency to wrap up tighter in turns in thermals - this is actually ideal for handling stronger thermals, but you'll occasionally need to "high side" it for weaker thermals. High wind days are no problem - it even makes the launching easier.

WARNING! If put in a steep dive for a long time and then suddenly shoved negative (ie an outside loop), the wings may still go into oscillation with the single spar version. I've done successful outside loops, but have also had several catastrophic failures. If you want to do the full range of aerobatics possible with flying wings, go the Blade Ray version.


The Manta Ray fully loaded comes in pretty hot when there's no wind. There's no flaps or spoilers, so my favorite approach is to get down into ground effect with pretty good speed, bleed it off, then lift the nose quick to stall it and slow it down, then shove the nose down. Not as hard as it sounds.

The VTR is great to watch the flights later too - watching the loops while looking out the wing - yeow, what fun! Or setting the camera straight back for those Rocket brushless launches...

NEW - Video clips

Some additional construction tips and warnings!

Running the Speed 600 12v with 18 cells is really pushing the limits of what this motor can do. I've burned out 5 of them already. But what I've found is motor lifetime has a lot to do with how well heat can be carried away from the armature. With the Model-Air Tech H-500 MKII belt drive, I've drilled two 3/8" holes in the upper corner, and two 1/4" holes in the lower corner of the mount to facilitate airflow. I've also added some copper sheet on the 4 sides of the engine mount box, with pieces wrapped around to the outside of the box to conduct away heat. Without the pod, the airflow over the wing is right into the engine, so it stays a LOT cooler. But WITH the pod, the airflow is poor. I've even added ducts around the pod to move the air in better (these changes are not in the above pix).

Also, the strapping tape is NOT designed to be directly exposed to UV for a long time. Cover the strapping tape with the colored plastic tape or some other tape with low UV transmission.

The Aveox is also pushed pretty hard. I have been using an M160 controller, and it's been burning up TOO often for my taste - usually it's hot days that cause the problem. Aveox says to limit it to 14 cells. So I switched to the Maxcim motor/controller - have about 15 flights on it now - and it just passed the acid test at Diablo Valley - HOT day (90+), no wind, 6 blown launches that broke 3 sets of props, had to substitute a 15x12 prop (too big - it went into current limiting, so had to keep the throttle down). Still runs great! Oh yeh!

Cost estimates

I've put together an Excel spreadsheet of the estimated costs of the Blade Ray version. I've probably left a few minor things out, but hopefully not more than a few bucks worth. I usually carry 3 sets of the 18 cell packs (made out of 3 6 cell packs). The option A configuration uses a simple portable TV/VCR for the display and recorder - it's a bit on the heavy side. For portable use - ie, carry everything on a backpack but the plane, I've put together the option B system. I use the camcorders LCD to view. It's NOT very bright and needs a sunshade. The TV works much better for watching the view and flying the plane by the video. But the digital camcorder records a cleaner video than VHS.

Acrobat pdf version cost estimate

Excel spreadsheet version.

Updated 1/7/2000

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Hang Gliding Pix

Some other links of interest:

New York Blimps

BASH Enterprises

Aerospace Composites


Model-Air Tech

Hobby Lobby


Sheldon's Hobbies

North Country Radio

B&B Electronics - another source for the cameras

Tower Hobbies