Mini Viper (oz6300)

 

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IIRC, the Viper was thought as an electric racer, not an IC model. A good look at the plans will show NACA cooling ducts on both sides of the fuselage, a battery pack beneath the wing and a knock-off fuselage top for a quick battery change. Love your homepage!
Rudy - 14/06/2015
A photo of my Graupner Mini Viper [main pic].
Dieter Fritsche - 08/06/2024
After a long and judicious perusal of the Oz site, I finally decided on the Mini Viper as my first foray into speedsters [pics 005-007].
The plane is so small that most builders can make it from scraps. That said, this plan is not for beginners. The original Mini Viper was a kit, so not all parts are drawn, further, building the wings requires some skill, and accurately aligning the flying surfaces is critical - as the maiden flights will attest. On the plus side, it doesn't require an expensive powertrain to get it humming, and this bird can hum! I fitted an Emax rs2205/2300kv motor (£10), shod with a 5045 prop, married to a 30amp esc and either a 3s or 4s 1000mah battery. Performance with the 3s is fast, with the 4s... you may require a change of underwear!
The maiden flight was a disaster, I had no control whatsoever. The Viper is very twitchy, and I had far too much throw on my ailerons, which made it all but impossible to control. Worse, my CG was slightly behind the recommendation. Don't go there! The flight lasted 48 seconds, and the only reason it didn't end sooner was the colour scheme, which did its job of helping me orientate the plane. The more top/bottom contrast you can design into your colour scheme the better. You will thank me: this wee beast disappears very quickly!
Having substantially dialled down the throws and sorted the CG, the second flight could be described as better... but also as the most intense five minutes of my aeromodelling life!
Remember my warning about the building and alignment of the wings? I am a competent and conscientious builder, and I used a jig to align the wings, but somewhere there was a gremlin hiding... The result was twofold: the plane wanted to dive and roll hard to the left. These inclinations were so severe that in my struggle to control the plane it became almost impossible to retrim it. Eventually, I succeeded using my left hand, but only just. Trust me when I say this plane is fast and twitchy, and takes barely seconds to cover your flying landscape before it disappears from view. If you have a trusted friend who can operate the trims while you're flying, that would be a good idea. This is not a docile park flyer!
Having established some vague semblance of stability - a rather relative term in this case - I ran a couple of high passes, then brought her in to land before it gave me a heart attack!
I walked away from that flight alive, but only just, and needed a stiff dram just to stop my teeth from chattering. I probably aged a month in that five minutes. I dialled down the controls even further, and adjusted the linkages to the new trim. The next flight was... magical!
The Viper leapt out of my hand, and shot straight into sky like an arrow. It's a sleek ship and flies almost silently, she cuts through the air effortlessly and responds with alacrity to every input from the controls. Surprisingly, you can slow her right down and turn her on a sixpence, the stall is surprisingly benign and easy to catch. (I did sand in some washout to the tips.) Full throttle resulted in a steep climb - a tendency that was eliminated with a washer of downthrust.
If the performance with a 3s is respectable, on a 4s it is terrifying! It will eat up your landscape like a screaming cruise missile, and look fabulous doing it. As for vertical jollies, let's just that the Viper has yet to acknowledge the existence of gravity. The Space Station is well within reach of this wee beast!
In conclusion, the Viper is a fabulous plane for the intermediate builder and flyer. It's as cheap as chips to make, flies on rails when trimmed and, for one YouTuber, hit 174mph! Mine is probably close to 100mph. You can also fly it in the wind, which will help to slow it down for docile landings.
If ever a model deserved the monika of 'pocket rocket' this would be it. I'm 64 years old, but I come away after every flight giggling like a naughty schoolboy! However, never forget, it's not called the Viper for nothing: treat it with unwavering respect and it will reward you, anything less, and it will bite you.
I love it!
Justin Baldwin - 02/07/2026
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