Hyper Viper early report

Generally, it is a beautiful and well designed model. It has the potential to be competitive at least at PAMPA beginner level with a few modifications.

As provided, the following problems showed up:

1. The engine goes rich in the air. Cure - shave the angle on the filler and vent tubes down from 45deg to 15 deg and reduce the pressure build-up.

2. The lines, of course have to go. Dacron is fine for very casual sport flying, but not if you want to get serious. Mikey recommends 42' of .008 cable, and if you punch up the power, I am finding that he is right on the money. If you don't modify the engine, you probably better not look at over 35' of .008. Don't even dream of trying to fly with .012 lines, unless you just want to climb, dive, and fly level. I also found that I needed extra tipweight (everyone seems to be finding the same), and it has now been added.

3. Power. I did manage to squeek in some large loops and lazy eights, but it was a near thing with the stock engine on 39' .008 lines and the RSM/Renger handle. Again following Mikey's recommendation, I pulled the engine and removed the screen from the venturi. Lo and behold, the venturi is molded with a serious restrictor. When the heck did that happen, and why??? I do like the cylinder porting, it is better than the old Black Widow's.

The original engine is sitting on the bench until I have time to mess with it. The model now features an original Killer Bee, Norvel Freedom plug (6!! gaskets) and APC 5.7x3 prop (Again Mikey recommended). At present, I have only flown on 39 foot lines, and definitely want the extra length recommended. However, using Aerodyne 350+P fuel, running somewhere around 20K, I was able to do all the maneuvers in the pattern. Somewhat oversize, but with potential for further improvement.

4. With the extra speed and vibration, the canopy blew off. Goop adhesive to the rescue (Totally fuel proof, and clear)

Further stuff left to do - Go to the longer lines, play with handle spacing, cover the open rear of the fuselage with clear tape, or something ( Maybe CA tyvek to the fuselage and one thin coat of epoxy for a permanent fix?), Then experiment with more props.

One negative that we ain't a gonna cure, the model has a high wingloading. You absolutely need to keep the speed up, and that especially includes landings. But what the heck do you want for 1 hour's work and under $50?? Extreme power and long lines, definitely the way to go.

Recommendation - get at least one (or two, and learn monoline flying)

Thanks Mikey - a job VERY well done!

Hi Larry,

Great report. I did not have any problem with going rich on my HV as reported by some people. I ran the stock engine with a Cox High Compression Head with 3 gaskets. With an APC 5.5 X 3 is almoust hit 15.5K.

However, one major problem I had was the Warped wing and C.G.
If a kid you didn't know any were to fly this model and carefully set it up accordding to the instruction, they would still have a problem.

The leadout location on my HV came out infront of the C.G. which is disactorist for someone who did not know how to check this. Mine C.G. balance on the 3rd hole, and Cox instruction said to put the leadout in the first 2 holes.

I will try your idea, and add a Killer Bee cylinder/piston to mine.

O K, Couldn't resist the urge so I ordered a Hyper Viper over the weekend. It arrived today. The first thing I did was put a little Zapa dapa goo on the inside of the fuse where the canopy plugs in. Luckily I have an early version of the Killer Bee to put in it. Might be a few weeks before I can take it out to play though. We have a Collecto this Saturday and VSC is coming up soon. We don't have a paved circle so I will probably not use the gear. Hope the wing can hold up reasonably well to grass landings.

Larry, what is best method to increase bore on intack? I opened mine a little with axacto knife. The spray bar is in the way and looks like a press fit. Thank you,Dan.

I never tried opening up the venturi without removing the NV body. Why bother. It is very easy to press the body out and back in by hand. Just use a wooden dowel or pencil eraser so you don't ruin the threads. Slip the black nylon seal off the needle end, and push it out from there. When re-installing, be sure the spray hole points straight at the reed-valve.

Ok, I'm ready to try it again with a Killer Bee engine installed. I only took tye airscoop off the orignal and installed it on the KB.

Will try this weekend on 42' X .008.

What kind of Cox motor is in these?

i bought 4 of these KB about 3 years ago to be use for mouse. I was able to reach 19K on a 5 X 3, but the dirability of the crankcase shaft is questionable. The engine only ran about 20 runs before the crankshaft broke.

Was that the new or old version, "these" could refer to either in the preceeding post.

I only ever destroyed one real KB crank, and that was running as a diesel. Pushed the crankpin toward the center of the shaft about a 1/64 " without breaking it off. Very strange.

That's why I like the old, first gen Fox .049, and I'm not talking about the FAI version.

19K on a 5-3 with only 15% nitro is no problem.

Flew the Hyper Viper this morning with the KB mods. First tried is with the High Compressino head with 3 gaskets. It was too over compressed and would not hold a needle setting. Went back to the standard Cox head. The best I could do was 16.8K with the APC 5.5 X 3.

Flown it on 42 X .008 line, but still not enough speed to do an kind of vertical manuevers.

I think I just about had it with the Cox engine. I'm going to mount my Norvel on it.

>Flew the Hyper Viper this morning with the KB mods. First
>tried is with the High Compressino head with 3 gaskets. It
>was too over compressed and would not hold a needle setting.
> Went back to the standard Cox head. The best I could do
>was 16.8K with the APC 5.5 X 3.
>
>Flown it on 42 X .008 line, but still not enough speed to do
>an kind of vertical manuevers.
>
>I think I just about had it with the Cox engine. I'm going
>to mount my Norvel on it.

The Norvel isn't a bad idea.I have a few of the pre Revlite models and feel that they would be better then any of the current cox motors.They are certainly less fussy about break in. However the motor that I'd rather put in it is one of my V.A MK 1 049's these were always exceptional runners for me. I still have a few new examples of the roll your own timing and can easily set one up for this plane
Dennis

Be sure and check the fuel tank before installing it. Like Rob on ssw, my tank was totally clogged from the inside. I called the guy at Estes and he is sending me a new tank. To check it, see if you can blow through the tank when you close off the fill/vent tube. Nothing goes through the outlet to the motor on my tank. Also, had to cut some excess plastic from the fuselage around the elevator linkage to allow the elevator to move without clicking/sticking.
I am waiting for my new tank...
Nick Vanmatre

thanks nick ill be sure to check for that

Larry,

Did you ever find out what that venturi diameter should be?

Thanks.

Yup, and mentioned it in two different places, but just for the record, it is .185. I am using 11/64, which is very slightly smaller to get a bit better fuel draw. The original Killer Bee was intended to be a nostalgia free-flight engine, and fuel draw not much of an issue.