I have a Cox Hyper Viper that I've only flown twice, and those were not enjoyable flights. I have to admit that the engine ran great right out of the box. In level flight the plane is just too fast with the stock prop, a 5x3. I flew it on the stock dacron lines that came with the plane which look to be about 35 ft long. Anyone else got any experience with the Hyper Viper?

Just out of curiosity, what is the dry weight of the Hyper Viper?

Robert

The Hyper Viper was designed by Mike Pratt, a very good designer of all types of models from Slope Soarers to competition CLPA models.  Also a heck of a nice guy!  The Viper needs a bit more power than the stock engine provides, but you can get it by drilling out the venturi.  Pull the spraybar out, and you will see that there are a couple of flat molded restrictors in the venturi.  Drill it out to be round, and you gain lots 'o rpm.  The spraybar is installed at the factory with the fuel jet pointed straight toward the reed valve.  You can improve fuel draw by moving it to either side about 15 degrees below straight accross the venturi.

I agree that Spiderwire is the way to go.  It is way thinner for less air drag, and less stretchy.

Overall, a really pretty and smooth flyer capable of most of the stunt pattern.

The surestart engine provided will indeed benefit from extra nitro!!! 35% if you can find it (maybe Va. hobbysport still has some) will surely "pump up" the surestart, which IMHO is a great little engine for the price.   

...The spraybar is installed at the factory with the fuel jet pointed straight toward the reed valve.  You can improve fuel draw by moving it to either side about 15 degrees below straight accross the venturi.

Thanks Larry, it never occurred to me that those spraybars might have a "sweet spot".

George

i have one that has a profi .049 i use a pen bladder tank stuffed in the fuse. it will not provide a stunt run, a all out screamer but i like to fly fast.

It seems that, like the Me-109 before it, the model gained about an ounce between prototype and production.  That is a HUGE difference in performance potential.  Unfortunately, the later, solid foam wing Me-109s gained yet ANOTHER ounce over the originals.  Amazingly, it still could stagger through every stunt in the PAMPA pattern! Not good, but better than the 10 point minimum (11?  12? at least you could recognize it).

I put a (real) Killer bee in a Hyper Viper with a balloon tank, on .008 steel lines, and it was good fun.  Not competitive in our area, but quite acceptable as a trainer/practice model.  (Our competition models push 500 points flown against "the big guys")

The original Killer Bee had the "Killer Crank" which has a cutout around the crankpin and the pin with a hole drilled down the center.  The cylinder had slit exausts, but the lower exhaust slit was wider to allow sub-piston induction.  The cylinder also had an extra "flute" in the bypass on each side to induce a swirl to the mixture as it entered the cylinder.  Finally, the bore and piston were taper honed for maximum performance.  A real Killer Bee would turn an APC 5.5 x 2 prop at 22,000 rpm on 30% nitro.  The needle valve had to be lightened up to keep it from backing out at peak rpm, thus the yellow plastic extrusion extension.  Later, Cox just renamed the basic, garden variety product engine "Killer Bee" and roped in a lot of suckkers.    Buyers beware!

Yes I have the same backplate mount (I think I got mine from Texas Timers) and (if my memory isn't completely bonkers  ) I used that to mount the Norvel onto the aluminum plate that "somehow" is mounted in the Hyper Viper. I should really look at it. The plane is in the attic and I reached over it to grab my "1/2A" electric-Canard-pusher-Sig-Skyray on Monday.

Today I get to recall at what point I left the R&D of the Canard at from last year! .