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!:7

I have 2. A TD .051 in one after Tucson.

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.

The backplate is the main thing limiting the power, not the piston and cylinder! I will look up the correct diameter to drill the venturi tonight. (It has been 8 years or so since I did the design, so the number is not in main memory);)

Definitely a KB or TeeDee cylinder and piston will help, but not much until you do the venturi. Then you will have a beast on your hands.

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

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.

got mine today im going to fly it stock out of the box ill let you know how it goes.

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, 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 :7

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.

Ron Young

Hi Larry,If you need a good engine for your Hyper Viper let me know,I still have all the good engines that we use to do the flight demos with when we worked for cox.I have tested all of them and they turn a 6x3 cox nylon prop on 15% 16.000 and these are doubble ported engines.

How do you guys get a Tee Dee or a Norvel to fit inside of the Hyper Viper? If it doesn't require major surgery I would like to give it a try.

Jay

Jay,
Hmmm? I haven't tried it. It seems interest in the Hyper Viper was strong when they came out, but sort of fell off. Mine is in my garage, getting hangar rash...
Sorry I can't help you.
Nick Vanmatre
San Diego, CA
AMA 19201

>How do you guys get a Tee Dee or a Norvel to fit inside of
>the Hyper Viper? If it doesn't require major surgery I
>would like to give it a try.
>
>Jay



First get a Texas Timer backplate to mount on the TD or Norvel. The Norvel is preferred as it has more grunt. this automatically gets you out of having to fabricate a mount for your motor. I prefer the pre- revlite Norvel for this plane as it doesn't require so much removal of material to accomodate the cylinder.I'm not looking at mine right now so I forget what else I did, but it wasn't a whole lot more. I will say that my Norvel with the Texas Timer mount was about the same length as the Cox motor installed in the HV.and the CG was about the same.
Dennis

After a 20 year absence from modelling, I bought a hyperviper this summer to get back into C/L. Seemed like a real tank because of how heavy the tail parts were. After I bought the airplane, I found SSW.
With some time on my hands, I made several mods to the hyperviper, including adding a TD .049. Now, let me caveat this by saying that I have not flown this airplane to date - it is ready to fly, but I found a Ringmaster Jr. with a Fox .15 in the attic, and have been flying that instead.

Here are the things that I did:

> Replace the tail group with 1/8" balsa sheet. Hardest part was finding a 1/2A flap horn. Thanks Jim T!

> Scraped the entire fuselage with a curved hobby knife. Took off a pile of plastic. Same trick as lightening plastic props for Free flight airplanes. This idea came from MA in their series about modifying a cheap sleek streak for high performance (20 yrs ago?)

> Traced the inside dimensions of the firewall by laying solder wire in the corners - then transferred the dimensions to 3/16 sheet plywood.

>Cut the bottom cowl behind the firewall and permanently glued the front of the cowl and the new plywood firewall to the upper front fuse. Now the wing can be taken off without having to remove the engine.

>Used a texas timer mount, mounted the TD .049 sideways just as the original engine was mounted. Since the front is now solid - I removed the plastic around where the venturi would mount, and just left it open here. Sealed everything with white RTV.

>Removed all decals on the wings (they were wrinkled badly anyway) with a hair dryer. (Lesson learned - after the decals come off - use denatured alcohol to remove adhesive. I didn't do this, and wasted a lot of time trying to sand the adhesive away.)

>Filled the bottom groove with spackle - and painted with Rustoleum waterbase spray paint (Says 'NEW' on can, and came from Lowe's), followed by topcoat of varethane clear).

>Added a nickel to the tip weight, covered with monokote trim tape.

>Sheeted most of the open rear of fuse with 1/16" balsa. Then covered the part over the control horn with trim tape.

> Used a carbon fiber tube for the pushrod with a ball link at the bellcrank and a metal clevis at the elevator horn.

> I plan to fly the plane with 20# test spiderwire (braided,green in color)

That is what I remember that I did - I would be curious as to how much an original Hyperviper weighs - to compare with these mods. Does anyone have that information?

I will try to post pictures of the mods tonight when I get home.


Best Regards,

Darrel

Designman wrote:

"...4. With the extra speed and vibration, the canopy blew off. Goop adhesive to the rescue (Totally fuel proof, and clear)..."
========================================================
Being somewhat too lazy to do my own research, Larry, could I prevail upon you for a short description of this "Goop" adhesive, as well a bit of a hint where one might find it?

Thanks.

Having the canopy loosen in flight is the only real, but minor, problem I've seen with the three HyperVipers I've seen fly here in Alaska. Perhaps your hop-up was a good idea, as your canopy left the airframe , while the one canopy that has worked loose here tends to hang up on the rear tab, thereby becoming almost perpendicular to the fuselage and acting as a giant brake, although the pilot of that particular plane did continue his flights enjoyably at a slower speed.

The Old Sourdough
Beer Can Cove, Alaska, US of A

I flew my Hyper Viper for the first time yesterday. The first thing I notice is that the paint in the cowl is not fuel proof. I should of wiped it down right away but didn't and it ate thru the paint.
I flew it on 35' .012 lines and it would barely stay in the air.
Thankd for the report with pictures Darrel. Sure is nice to see what you did to make if a flyable plane. Not sure if I am going that far but will try a few mods.

For all you guys that are thinking of getting one it might be a good idea to get one now. Never know when they will stop productions.

http://www.coxmodels.com/prodinfo.asp?number=006020

Here is the link for the Texas Timer mount. I ordered 2, one for the Tee Dee and one for the Norvel. Thought it might be a good idea to have one of each.

http://www.texastimers.com/accessories/enginemounts.htm

Jay

Jay....I didn't know that Brodak sold them paint?

See Ya

Peabody

I am not sure if Brodak sells them, but Tower used to. The link is to the Cox site. Not sure who else is selling them.

Jay

Thanks for the kind words about the modifications I made to the Hyperviper. I hope to fly it for the first time this weekend. I remember now that I made two other modifications that I forgot to mention earlier:

First I scraped a LOT of plastic off the fuselage - so much that when I hold it up to the light I can see shadows from the molded bulkheads inside the airplane. Then, to counteract flexing around the belcrank post area - I glued the canopy onto the fuse all the way around the canopy's periphery. Made the whole assemly much stiffer in this area.

Second, based on advice from users on this forum, I bought several types of glow plug adapters for use in the TD. I now have four different glow plugs to try out -
- Galbreath head/Nelson plug
- Mecoa unit that adapts a standard (long) glow plug
- Norvell head and glow plug
- Of course,the Cox high compression head too.

I'm pretty sure that the Galbreath head/Nelson plug will be the best combination from what I've read on the forum. However, at $10.00 apiece for the Cox units, well...

Although perhaps not the best in terms of RPM, I'm hoping that the Mecoa unit will work too, since I can then use the same battery connector as for larger engines.

When I get a tach, I will report RPM numbers back to the forum for these heads and various prop/fuel combinations.


Still looking for a weight and c.g. location for the stock unit...

Best Regards,
Darrel

Jay,

I don't know about your atmospheric conditions or altitude, but I will say that the three of us that fly them together here have had only minor problems. The stock plane flies well, with good line tension throughout the flight hemisphere. We are using the stock engines running Byron 1/2a fuel (25% Nitro, 20% all castor, 55%methanol) and using the supplied Cox prop, although we all have several of the Cox recommended APC props to try. The three of us are all using the supplied dacron lines and handles, as well, but all of us have 35'x .008" cables that we'll be using soon, as the dacron is becoming oil soaked and sticky. The only modifications (?) we've made are:

1. Add a Nickel (5¢) to the weight hole on the bottom of the outboard wing for a bit more tip weight and cover the hole with a piece of 2" wide clear tape.

2. Install the leadouts one hole to the rear of the position suggested in the plans.

The other problems we have had are:

1. Two of the three fuel tanks were improperly joined to the point that air would not exit the tank when blowing into the fuel outlet. Cox/Estes replaced the tanks with no problem. We were not the first to have this problem, and we checked the tanks before assembling the planes.

2. One plane lost its canopy on every flight until the owner taped the front to the fuselage. We're going to find some "Goop" to fix that problem permanently.

We decided, contrary to the stereotypical male image, to read and follow the directions that came in the box. The only reason we installed the leadouts/lines about 1/16" to the rear of the position indicated in the directions was that one of us already had a HyperViper and had flown it at his winter home in Reno (at a much higher elevation than here) with good results. He found that variance to be worthwhile while flying there. He also discovered the advisability of that Nickel more tip weight at that time.

We also broke the engines in a bit, again following the break-in instructions with the plane, by running three tanks on the ground, leaning the mixture on all three runs until the engine would hold a strong, high RPM. None of us are engine gurus or designers, but this process works!! The engines have continued to gain power with additional runs while flying.

On none of the flights I've watched or flown have I seen any of the problems you and other folks have described. We are not expert level fliers, but we do know a fairly decent airplane when we see or fly one. While I'm certain that the mods done by Larry and others will provide better performance, the plane does pretty well stock.

Did you read Larry Renger's review? It's the first post in this thread. In it, he wrote, "...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 tip weight (everyone seems to be finding the same), and it has now been added....." This might be your biggest problem so far. Has your engine been properly broken in?

I admire the excellent TD .049 installation shown here as well, but I'm not convinced that it is needed. As far as replacing tail feathers and sealing the bottom of the fuselage with balsa, I would ask, "Why?" If one is going to all that trouble, why not go all the way and throw away everything but that foam wing and possibly the landing gear and build the rest of the plane from appropriately sized balsa. That's what I would do if I wanted the ultimate in performance from that wing.

Finally, as I wrote previously, I'm not an expert flyer who would be able to obtain the performance you might be seeking, but for my money ($40.00 at the LHS) the HyperViper is a good machine as it comes from the factory. I have 1/2a planes that I've built that fly much better, as they are larger and much lighter, but when I consider the cost of balsa, finishing materials, tank, engine, wheels and all the other bits required, to say nothing of my time (if I considered it as a cost), those probably cost at least double, if not considerably more, the price of the HyperViper.

The Old Sourdough
Beer Can Cove, Alaska, US of A

The Tower Hobbies web site say they have been discontinued. They sure didn't last long. [photo not recovered: shocked.gif]

Ron,

They're still there. They're just not available through Tower any more.

http://coxmodels.com/prodinfo.asp?number=006020

The Old Sourdough
Ruksakinmakiak, Alaska, US of A

I have purchased one of these earlier this year from Cox Models too.

I followed Larrys instructions and drilled out the restriction in the venturi to 3/16" and drilled a few 1" holes in the bottom of the fuse and wings to lighten it a little. We have flown it dozens of times and had a lot of fun.

Have done wingovers, inside and outside loops, lazy 8s and inverted no worries. So I can tell you they fly very well here in Australia at Sea Level.

Here's a couple of nice pics of mine in flight.

Warren Leadbeatter
Sydney, Oz

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Photos are shown below, in no particular order. Hope this helps...
-Darrel

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Nice mods; and very nice pixs to let us see what you did. So.... How does it fly?
Nick Vanmatre
San Diego, CA
AMA 19201

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.

Attachment #1, (jpg file)

What kind of Cox motor is in these?

Currell

The Killer Bee isn't going to run right with the original HV engine backplate, the venturi is too restrictive. The Killer Bee backplate without the added pipe works just fine, or you could add the pipe to the KB backplate, and that will work too.

Also, I see your KB has a plain aluminum finish crankcase, which means it is one of the new ones, and no different from the engine you removed. Sadly, C*x castrated all their performance engines some years ago. ONLY Killer Bees with yellow anodized crankcases and the plastic extension needle valves run the way it was designed to run. Sorry, but that's just how it is. :'(

The original engine in the HV is the basic ready-to-fly one. I think it is completely stock.

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.

Currell

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