Review of new wing ( the Terni )
I recently purchased a kit from a model designer and fellow Ezoner Corndog (Mike) for a new speed-400 class flying wing, the Terni (http://www.rcgroups.com/forums/showt...ighlight=terni ). As promised, here is a brief review:
The Bottom Line: The TERNI is a solid performing speed-oriented wing at a very reasonable price.
- Reverse-timed 6V Speed 400.
- Packs used: 8-cell 600AE, 8-cell HECELL, 8 and 9-cell KAN 1050
- HS-81 Servos
- Full-size Tower-Hobbies rx with the outer housing removed (about .25 oz heavier than a Hitec 555
- GWS micro mixer
- Wattage 15 amp esc
- 12.25 oz w/o battery (a little heavier than plans due extra packing tape, Coroplast ‘cockpit’ and use of full-size rx + on-board mixer).
- 17-19 oz AUW depending on pack used
What it would run you minus radio gear
- Kit $25 + shipping
- Motor: $8 including shipping (Ebay)
- Battery (8-cell KAN 1050) : $20 (got to love cheapbatterypacks.com)
- ESC: $20 ( on sale, Hobby People )
- Tape (Packing + Strapping) $7
- Total minus radio gear = aprx $80. Compare that to $100-130 for a similarly equipped Zagi Razor or Wedgie and you’re looking at a reasonably good value.
- Having already built a couple of wings, I managed to throw this one together in a little over three hours. There really isn’t much to say about assembly other than it’s very “Zagi-like”. Basically, if you’ve built a Zagi before you can pretty much jot down the CG point, note the battery placement and ‘wing-it’ without the instructions.
- For someone without experience building wings, however, the instructions are probably a little sparse especially in the areas of covering the wing and mounting the elevons. Mike could probably clear this up with a simple covering diagram and picture illustrating his elevon mounting method (which works very well by the way).
- In any event, the contents of the kit are first rate: The cores are very cleanly cut and mate up with little to no finish sanding. The winglets are sharp and already matched. The included balsa and hardware are all of good quality. I’m especially fond of the motor mount design – it’s simple, durable and allows for good air circulation around the motor.
- I honestly can’t remember what the recommended throws are with the TERNI, I’m currently at about ½ inch each way and get pretty snappy performance without feeling out of control.
Deviations from plans:
- Used full-sized Rx. Although I have an extra Cirrus MX-4 micro receiver lying around, we know how quickly a hopped-up wing can blow through 900 ft (the range of the Cirrus). Rather than spend $60 on another Hitec 555, I simply opted to lighten a full-size 7 channel Rx I had lying around. With the outer housing removed, I got it down to around .95 oz, about .2 oz heavier than the 555. The range should be over a mile.
- Added a small electronics box. Because I like to be able to easily swap power systems and receiver crystals, I don’t usually build receivers and ESCs directly into my planes. For this one, I just built a simple little box out of 2mm Coroplast into which the receiver secures with Velcro. The lid is also held on with Velcro. It provides easy access to the receiver plus the ability to extract the complete power system (esc, motor and wires) by simply unscrewing the motor from the mount and unplugging the ESC.
- Went a little heavy on the covering materials. As I built this plane for combat and general motor abuse, I went a little overboard with wing reinforcement: As well as the recommended ‘criss-cross’ of packing tape on top and bottom of the wing, I added a nice wide strip on the leading and trailing edges. For the final covering I used a combination of heat-shrunk packing tape and low-temp film ( Oracoat ). The resulting wing is VERY stiff, but probably a full oz. heavier than it needs to be. For more casual flying, you could easily get by with no fiberglass strapping tape at all, a small CF spar and thin packing tape as covering.
- In the rapidly widening spectrum of Speed 400 flying wings, the TERNI seems to sit somewhere between a stock Zagi and a Wedgie in terms of speed and maneuverability. It doesn’t quite have the speed of the Wedgie in the stock sp-400 configuration, but could probably handle larger motors and packs a little better due to its additional wing area.
- Just as Mike claims, the Terni is faster and more maneuverable than a Zagi. Side-by-side my TERNI out turns, out runs and out rolls my 400x running the same power system. The trade-offs are of course, stall speed and the ability to thermal.
- With a timed 6V Speed 400, Gunther prop and a 9-cell pack of KAN 1050s I estimate my level WOT speed to be around 60 mph (given a slightly heavier-than-intended wing). Loops from level flight are no issue and vertical performance is good (although not exactly ballistic with my set-up). I’m sure that with more expensive (BL) components, unlimited vertical could be easily attained with this wing.
- High speed stability is good, probably due to the wing profile. Once trimmed out for WOT, high-speed passes 3-5 feet off the deck are very doable and almost hands-off on relatively calm days.
- With the throws cranked up loops are very tight and roles can be pretty quick. Sustained inverted flight is possible, but a little tricky due to the flat-bottomed airfoil.
- Given the higher wing loading, the TERNI is obviously less stall resistant than a ZAGI. You really couldn’t expect anything else. As long as you keep the throttle up it’s very controllable, you really need to watch it in low speed turns though – as you would with any similar wing (like a Razor or Wedgie) – or you can easily find yourself in a spin-stall .
- Landing is relatively straightforward although a bit faster and harder than with a 48” wing. When flying dead-stick this little bird looses altitude pretty quickly so you really need to plan your landings to avoid ‘slamming her in’ or cartwheeling. Then again, it’s a pretty tough little plane and seems to handle my crappy landings well enough. Although I have tried hand-catching with the Terni, I wouldn’t exactly recommend it.
- As far as batteries go, I think the 8-cell Kan 1050 pack is the best balance of power, weight and run-time for my motor selection. With the 1050s and poor throttle management I’m getting 5-8 minute run times (which would translate to about 10 minutes of not flying like a complete idiot). A 9-cell pack of the 1050s is a real hoot, but a little hard on a lowly SP400 power system (after 2 min WOT you start to smell burnt toast).
- In terms of required piloting skills, I’d say this is most definitely an intermediate’s plane – a little more difficult to fly than a stock Zagi but not quite as slippery as say a Speed 400 pylon racer. Although it would frustrate the snot out of a beginner, someone with a bit of wing experience should have no trouble with it at all.
- Also better than a Zagi. With a little extra reinforcement, the TERNI is practically indestructible. With the battery Velcro’ed to the bottom of the wing, it can easily tear free in really nasty crashes and take most of the plane's kinetic energy with it. Best of all, there’s no canopy to shatter.
- I was initially a little hesitant to use the included Depron winglets. I figured that I’d have them broken within a few flights. Well, guess I was wrong – they’ve proven to be pretty tough so far. Then again, if you wanted, you could easily replace them with 2mm Coroplast in a matter of minutes.
Room for improvement:
- Aside from lacking more explicit instructions for covering the wing and mounting the control surfaces, there really isn’t much room for improvement in the Terni kit. It basically does every thing its supposed to and is a more than decent value. I’d recommend it to anyone with a little flying-wing experience.
Assembly in pictures:
What you get in the kit (not bad for less than 30 bucks):
thanks for the excellent, informative, review. i will work on the instructions to see if i can increase the clarity on the covering. i will try to have a prototype of the 36" twin speed 400 wing waiting for you when you return from vacation. at only 36" its gonna be a rocket!!! i hope your ready!!! the twin kit will cost $39 and include basically the same parts as the TERNI kit except i will add another aluminum motor mount and a carbon spar. what do think about a TERNI biplane? has anyone tried a flying wing biplane? the bottom wing would have all the electronics. linkage the elevons. put motors on both wings and upgrade the battery. might be kinda neat?!?!?!?
Can't wait to beta the twin - with your relatively thin airfoil it should be WAY over powered (that’s a good thing). I’ve dug up some lighter electronics and am planning on really building this one for speed. As we have a couple of cops in the family, I should be able to con someone into taking a radar gun to this new bird.
I’ve never flown or tried to build a biplane wing, although I’m certain it’s feasible. It would probably be far more appropriate for slow tumbling than flat-out speed but would, in any event, turn some heads at the field.
By the way, when I cut out new Depron winglets for the Terni (after about 20 abusive flights I did finally manage to tear one), I extended them about an inch past the bottom of the wing. This seems to buy a little more stall resistance at lower speed turns without adversely affecting top end. I’ll post some pictures later this week.
Talk to you later,
PS - yes that is a spar on the terni in the picture (with the servo wires laid on top) - at this point I have to admit that it might have been overkill to add it.
the hs-55 are acceptable on the terni. they have just enough strength but, easily strip gears. there is no way the hs-55's will work with the new twin 400 kit. although it may be interesting to see one fail at 80 mph!!! i may be able to help you out with the servos. i have a couple on new gws park servos i may be willing to donate to the cause. those are actually pretty decent servos. they have more than enough strength, pretty smooth, reasonably fast, and only 12.99 from aeromicro. your twin 400 beta kit may be a little late. im trying to put together some kits for the local swap meet this saturday. next week looks good for the twin 400 progress. ill post some pics and rough flight report. i also am making some changes to the terni kit. its getting a thicker airfoil and will gain an inch or two in wingspan. i want to make it a little more user friendly. if people want crazy speed, they can buy the twin.
No rush on the twin, just don't make it too much like a Zagi - I already have one of those and am actually very fond of your "go fast" airfoil.
The Terni modifications sound like a good idea if your intent is to trade a little speed and agility for better low-speed performance (less stalling). You'll probably end up with a wing a little less "floaty" than a Zagi, but just as easy to fly. I'm sure they'll be popular, the current design is already a hit at my local field.
Once you get the bugs wrung out, I'd like to buy a set of the new Terni cores from you - after one too many collisions with inanimate objects, my 400x cores are getting pretty mushy and need to be replaced. I like the idea of keeping a mellow flyer around, as I'm about to add another speed demon to my hangar.
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