Cox Hyper Viper in Stock

While checking on the ST listed before I happened to check the status of the Cox Hyper Viper. It is in stock!

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXDUT1&P=K

Jay

Hey That looks cool does it have a reed valve engine? how much does it weigh? Scott

From my recollection of input from Mikey (Mike Pratt, now back at SIG, I think), who did the main design and development work, it is about 165 sq.in. and weighs just over 9 ounces. It has a full stunt tank and a reed valve engine. The airfoil is 15% and similar to the one used on the Pathfinder series.

As such, it should be superior to any RTF ever done, including my own Me-109 design. I can't wait!

Is this thing flapped or not? Can't figure it our from the picture.

Thanks,
--Mike

I am pretty sure it isn't flapped.

As a follow-on to the ME-109, I prototyped a Crusader with the folded foam wings and 1" flaps added. WOW did that thing fly well. Wonder whether anyone saved those old prototypes from destruction.

Hah bout time they got them in stock. I didnt even get email notification yet. I got me 2 of them One for me and one for my daughter.

Woohoo, mines on the dock waiting for UPS pickup! Gonna fly that sucker next week.

Interesting
Does anyone make a conversion for the head to take
a standard glo Plug please?
Might encourage me to buy one
Vincent

>Interesting
>Does anyone make a conversion for the head to take
>a standard glo Plug please?
>Might encourage me to buy one
>Vincent

http://www.the-printer.net/DookCat.html

Nelson Head for Cox, AME .049**
Head $10.00
Nelson Heavy Duty Glow Plugs $3.25

Website for Doug Galbreath, who sells what you are looking for.

MECOA makes a converter for standard plugs, so does Norvel. I think the MECOA uses "long", and the Norvel "short". Plan on using "Hot" plugs unless you are running really high nitro.

Norvel plugs go onto the C*x engines, and actually improve them! They are priced relatively low too.

If you use the Galbreath head, plan on an extra gasket or two!

Mecoa also has those RJL diesel converters for Cox engines too.

My HyperViper has been shipped.

MECOA makes a converter for standard plugs, so does Norvel. I think the MECOA uses "long", and the Norvel "short". Plan on using "Hot" plugs unless you are running really high nitro.
Norvel plugs go onto the C*x engines, and actually improve them! They are priced relatively low too.

If you use the Galbreath head, plan on an extra gasket or two!

Larry Renger
think S.M.A.L.L.

Larry,

I may be behind the curve here, but during development of first VA 049 I tried virtually every alternative to Cox glowheads out there; and this was way before the pricing went through the roof on replacements.

We never found **any** conversion head--including the MECOA units--which utilized standard 1/4-32 glow plugs to work. Even some tasty experimental bits the Russians came up with. While I cannot at this moment refer to my notes, my recollection is that we are talking not hundreds of rpm, but thousands. Not only substandard performance for contest work, not viable for even sport flying.

Again, I do not claim to be current on 1/2A stuff, but Galbreath's head with Nelson plug was found to easily be the best, whether on a Cox TD 049 or a VA 049. We of course copied the head shape, made minor changes to the exterior. The Ruskies could not come up with a better unit, and they tried.

Your caution as to head shims is exactly correct: It is all too easy to over-compress a 1/2A engine with the Galbreath head; in this regard they are not a direct bolt-on. The good news is the engine will run better with extra head clearance and plug life will (nearly) become a non-issue.

I also found that while Galbreath's head is real good, the standard Cox 1702 glowhead is still the benchmark. The design of that sucker was either a fortunate accident or pure genius, I have never known which.

I absolutely agree that the performance with a standard glow plug conversion is awful. I have seen and tried 3 or 4, and they were all down a minimum of 1500 rpm. If you want to fly a sheet trainer with a Tee Dee, they would be OK, but that is about it. Sorry if I failed to emphasize the loss of power they cause.

Recieved the plane in todays mail.
Replaced Sure Start engine with a Black Widow using the Sure Start mount,switched the stock prop for a MA 5.5x4, and added lead-outs.
See how it flys this weekend!
Rob Johnson
Orange,CA.

LAST EDITED ON Feb-21-04 AT 09:09 AM (CDT)
 
Rob,

Can you (or anyone) remind me what the difference is between the Sure Start and BlackWidow (excepting the tank of course)?
Thanks

none, actually. The Sure-start uses the same twin bypass cylinder and piston. If you want a hop-up you need to go to the Tee Dee cylinder and piston, and a high-compression head with a couple of extra gaskets.

But why bother? If the Sure-start is broken in right, it should fly just fine as is.

I got my HV, and it is gorgeous. I plan to use the stock setup except for lines, which will be .008 cable.

If you want more performance, use more nitro.

LAST EDITED ON Feb-21-04 AT 01:27 PM (CDT)
 
I'm no Cox expert, but what I've learned by playing around a bit with them is that the main differences are breathing, compression and mounting.The Sure Start has some really small exhaust ports. The venturies are different, but I'm now using the Sure Starts venturi. The Sure Start uses an external fuel tank and the Black Widow uses a radial mount fuel tank. The Sure Start also uses a prop stud and nut where the Black Widow uses a prop screw and has a cool little spinner. Also, one thing that has gotten me several times and has also put a number of my friends Sure Starts out of service is the plastic intake tube. It breaks at the mounting holes when crashed a couple times and I have not been able to find replacement parts. What I've been doing is ordering Black Widow tanks, converting them to stunt tanks and mounting them to the Sure Start crankcases. Of course, this changes the engine to a radial mount, so the plane has to be converted. My flying buddys have been giving me there broken Sure Starts and I now have quite a few Sure Start/Black Widow hybrids waiting for a plane.
I've attemped to upload a pic of a Sure Start engine and a Black Widow to show the difference in the exhaust ports... see if it works. Sure start is on the left.
Rob Johnson
Orange,CA.

So far as I know, there is no real rpm difference between the two exhaust versions of the Black Widow and the Sure-start. The real place to look for potential power is in the bypass ports and the taper of the piston and cylinder, the fit of the crankshaft and the size of the venturi.

The key to the performance of the Venom and original (forget the current version, it is a Sure start) Killer Bee is the use of a Tee Dee style bypass and a taper ground piston and cylinder. Similar to an ABC engine, the piston and cylinder have a .005" or thereabouts matched taper ground in, so that as the engine reaches running temperature, it straightens out. The running friction and compression are optimized, and you get the best performance.

Once you do that, you can drill out the venturi to allow better breathing. When the engine can easily reach high rpm, it can draw fuel better and handle the wider opening. If it is rpm restricted elsewhere in the design, wider venturi only gives you lousy fuel draw. Everything has to be matched.

Now, if you want to make your own "real" Killer Bee, get a Davis Diesel crankshaft, an old but unused anodized crankcase, and a pre-1997 Tee Dee piston and cylinder.

Clean everything and leave it dry. Fit the crankshaft to the case, and give it a twist. It should spin over several times with a nice snap of the thumb and forefinger. If not, cut the head off a 5x40 bolt or use a C*x prop stud; chuck it into your drill. Do a "shoeshine" kind of polish with 1500 or 2000 grit w/d paper soaked in oil over the crankshaft until it spins really freely in the crankcase. NEVER get grit into the crankcase, you want to preseve that thin layer of anodizing inside the crankshaft bore!!! This is REALLY an important point. Do NOT lap the crank to the case if it is anodized.

You can drill the venturi out to the next drill size, or even two, if you don't care about fuel consumption. Use the stainless steel reed if you can get it. I really don't like the plastic reeds. They warp after a few runs.

The best head is the Galbreath/Nelson plug adapter. After that, the Norvel "Feedom" plug is really good. A couple of extra gaskets will be needed with either one.

Now, you have a "Killer" indeed.

I look at the smaller exhaust ports as a restriction, much like using a throttle sleeve to control the speed of the engine. I can "hear" an RPM difference, but have not shot an engine with a tach to be sure. I'll see if I can do that Monday at work.
Didn't get to fly the Hiper Viper today. It is raining here. Never rains untill you have a new plane to fly!
Rob Johnson
Orange,CA.

>I look at the smaller exhaust ports as a restriction, much
>like using a throttle sleeve to control the speed of the
>engine. I can "hear" an RPM difference, but have not shot an
>engine with a tach to be sure. I'll see if I can do that
>Monday at work.

Might want to pay close attention to what Larry is telling you - he was chief cook and bottle washer for Cox before they became Estes and he has run more of these engines than the rest of us put together!

I think that the current crop of "Black Widow" engines uses the same cylinder as the Sure-start. Plus no anodizing, no stunt venting.
similar downgrade to the "Killer Bee". This is one area where the "good old days" really were better.

Except, of course that you can now get Norvel and VA engines that will blast any C*x engine out of the air

Oh, someone asked about diesel conversion. Diesel fuel will definitely destroy the wing foam, and possibly the plastic fuselage. This is one of the rare times that high nitro glow fuel is less damaging than diesel!

I'm listening, and learning. Don't want to seem argumentative, just posting what I have seen playing around with these things. Just Having fun with a plastic plane on a string!
Rob Johnson
Orange,CA.

Dan,

probably pure genius! I have read somewhere that the original Rossi .15 speed style headbuttons of the early 1970's were machined from Cox TD .15 heads.

Any pictures of the completed Hyper Viper yet besides Tower hobbies site? What is it made out of? Most cox planes are made from plastic and some have foam, not are built up and will just go around in the cirle? Will this Hyper Viper do the entire Pampa pattern?

The wing is a hollow shell of bead foam. The fuselage and tail are hard plastic, but the walls are thin and the plane weighs 10 ounces finished with a 165 sq.in. wing.

I doubt you can do a true pattern, the limiter being the vertical maneuvers, which will likely be oversized. It certainly should do all the basics, and probably is competitive for beginner stunt!

Mine is supposed to get here Wednesday. I'll take photos for ya. Larry could post some completed pictures, hopefully mine will look pretty much like his.