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Cox Hyper Viper - 3/6/2005 5:33:59 AM   
green river rc



Posts: 861
Joined: 6/18/2002
From: Raywick, KY,
Status: offline 		My son won it new at a swap meet last weekend. It's suppose to do all kinds of AMA stunts but we couldn't even squeeze a loop out of it. Maybe we are doing something wrong? We are only semi-experienced CL flyers but this is not what we are use to.

The main problem was that we couldn't keep the lines (35' dycron) tight enough. If it got up more than 20 or 30 deg. elevation, the lines went limp and I had to step back to save it and sometimes it would crash, luckily it won't go fast enough to break it. We also tried .008"X35' cables but it would have no such thing, they were to heavy! They recommended other props for better performance, will they make they much difference? Extra wing tip weight didn't help either, any suggestions?

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With the parts left over, I'm going to build a motorcycle.
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RE: Cox Hyper Viper - 3/6/2005 2:42:51 PM   
Clean



Posts: 990
Joined: 4/19/2002
From: Parkville, MO, USA
Status: offline 		Use 14 pound test Fusion Syder Wire, this is the knit type wire, not monofilement and is available at Kmart and Walmart in the fishing section. Lighter, cheaper to replace than cable and less draggy than the white stuff. The engine in the Viper is the cause of your problems, it needs an upgrade. Take it off, take it apart and start working. First, reset the ball on the piston, mine was loose from the get go, tighten it up and you have more power. There is not supposed to be much difference in power between the two slit exhaust and the open exhaust, but if you have a cylinder that is open and has the two port feed, swap it. I've heard someone knows how to pop those slits open, but I can't see me doing it successfully. There is a post over on Stuka by Larry Fernandez http://www.clstunt.com/htdocs/dcforum/DCForumID1/13027.html and he has taken the backplate off the motor, modified it and JB welded it into the back of a Norvel engine, then mounted that sucker into the Viper. More power than you'll ever need that way. I have swapped out a Blackwidow base with TeeDee .051 piston/cyl assembly and bored the mount breather hole for better flow, it screams pretty good but now I get fuel foaming problems from the tank, will switch to a balloon tank to get rid of those problems. When it has power, the viper flies fairly well, but you have to work the engines over for it.

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William Crane (aka Mr Clean) Rever Brother #168 Time Man of the Year

(in reply to green river rc)
       Post #: 2

RE: Cox Hyper Viper - 3/6/2005 2:55:00 PM   
dennis



Posts: 1285
Joined: 1/7/2002
From: Minersville, PA, USA
Status: offline 		Throw the motor away and get a Norvel 061 and a texas timer backplate mount that you replace the Norvel backplate with. This is an easy conversion and is easily installed onto the Hyper viper without butchering the whole front up. It would be nicer if you had a pre revlite Norvel as the cylinder isn't so large around. Reduce the angle cut on the plastic tank to about 30 degrees or fit a sloghtly bigger on in. I use a bladder on mine. I know that that motor is going to run at top end till the fuel is gone.
The Norvel 061 is light years ahead in power without having to do diddly to it, compared to the slag Cox motor that they sell you

< Message edited by Lightfoot -- 7/31/2005 2:46:49 PM >

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       Post #: 3

RE: Cox Hyper Viper - 3/7/2005 2:06:58 AM   
green river rc



Posts: 861
Joined: 6/18/2002
From: Raywick, KY,
Status: offline 		Yea, that Texas mount is a nifty looking mount, I would hate to spend a dime on a Cox plane. I do have a new Norvel .061 though, might try the other thing.

So I guess the Cox .049 aint gona happen? I didn't think so, how dare them to sell a plane with such bold claims as flying the AMA pattern, and wont even loop. Sometimes I wish Norvel would buy them out, bulldoze the factory and plant it in corn!

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With the parts left over, I'm going to build a motorcycle.

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       Post #: 4

RE: Cox Hyper Viper - 3/7/2005 4:30:43 AM   
Bill Rademacher



Posts: 257
Joined: 12/31/2001
From: Rineyville, KY, USA
Status: offline 		Hi Dave,

I had the same problem. It wouldn't loop very well, and we had intermittent runs on the motor.

Fine a large port cox cylinder, for one thing. I may have on I'll give you. I'll check.

After you get the motor running, it will loop, etc. but a norvell is probably the way to go in the long run. I don't know why they ported these motors down, other than it makes them quieter.

Also, try 20- 25% nitro. It seems to work the best. 35% is too much for this particular motor. It will sieze up temporarily. It's kind of funny.

Hope this helps.

Bill R.

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       Post #: 5

RE: Cox Hyper Viper - 3/7/2005 8:05:15 PM   
kdheath



Posts: 1275
Joined: 11/9/2002
From: Rochester, MN, USA
Status: offline 		Couple of easy things you can do include drilling out the venturi as much as possible. I'll have to look and see if I can find the size it will tolerate again, but the info is out there. Then find a dual port (TeeDee) piston/cylinder set. Try smaller props like a 5/3. A balloon tank is probably the best choice for consistent running. And be sure the piston ball socket is snug. Use a reset tool if it isn't free of slack. Still won't be as good as a Norvel, but much better.

Edit: I thought I could find it. Here's bunch of good stuff about the HV.

http://www.clstunt.com/htdocs/dcforum/DCForumID1/11216.html

< Message edited by kdheath -- 3/7/2005 8:14:34 PM >

(in reply to Bill Rademacher)
       Post #: 6

RE: Cox Hyper Viper - 3/8/2005 12:03:14 AM   
Clean



Posts: 990
Joined: 4/19/2002
From: Parkville, MO, USA
Status: offline 		By the way, Cox/Estes is selling the product engines along with thier glow plugs which are pretty cheap at 4.99. You can go to the website and find the link.

I still think they're overpriced, but it's the cheapest price on the glow heads I've seen for quite a while.

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From Somewhere near Parkville, Mo.
William Crane (aka Mr Clean) Rever Brother #168 Time Man of the Year

(in reply to kdheath)
       Post #: 7

RE: Cox Hyper Viper - 3/8/2005 1:58:44 PM   
gcb



Posts: 2385
Joined: 10/24/2002
From: Port Ewen, NY, USA
Status: offline
quote:

ORIGINAL: kdheath
Couple of easy things you can do include drilling out the venturi as much as possible. I'll have to look and see if I can find the size it will tolerate again, but the info is out there.

Bear in mind that the larger the intake the less the fuel draw. Of course you can run a baloon tank for pressure.

quote:


Then find a dual port (TeeDee) piston/cylinder set.

I do not yet have my new ones, but one from the Nabu Fighters already has two port transfer, including the boost port found in the TD. It has the two slit exhaust ports with no sub-piston induction.

quote:


Try smaller props like a 5/3. A balloon tank is probably the best choice for consistent running. And be sure the piston ball socket is snug. Use a reset tool if it isn't free of slack. Still won't be as good as a Norvel, but much better.

I would also suggest 25% nitro, various props (perhaps a 6x2 might be good for that plane), vayious quantities of head shims, especially if trying the TD (fluted?) head. I think Cox still makes two other heads, the conical (standard), and high-performance (smaller cone with squish band). You may also want to try the Norvel head/plug and the Galbreath head/Nelson plug.
That's a lot of testing for an RTF, but some of it will probably make your Viper Hyper.

George

(in reply to kdheath)
       Post #: 8

RE: Cox Hyper Viper - 3/9/2005 2:21:36 AM   
green river rc



Posts: 861
Joined: 6/18/2002
From: Raywick, KY,
Status: offline 		I may try the Norvel .061 that I already have, all those mods sound costly.

_____________________________

With the parts left over, I'm going to build a motorcycle.

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       Post #: 9

RE: Cox Hyper Viper - 3/9/2005 12:36:10 PM   
gcb



Posts: 2385
Joined: 10/24/2002
From: Port Ewen, NY, USA
Status: offline 		gr,

Bottom line is that many have been successfully flying the HV. I would suggest a search for any mods.
Things to do that are not costly:
Make sure you are using 25% nitro fuel with 20% oil, mostly castor.
Break-in the engine.
Try different props.
Try a high-performance glow plug...or the one from your Norvel.
Try varying the number of glow plug gaskets (shims).
Check the tank for proper fuel flow. Some Hyper Viper tanks were defective.
I would suggest the steel lines.

Good luck,
George

(in reply to green river rc)
       Post #: 10

RE: Cox Hyper Viper - 3/11/2005 1:14:18 AM   
gcb



Posts: 2385
Joined: 10/24/2002
From: Port Ewen, NY, USA
Status: offline 		green river rc,

There was a discussion on the Hyper Viper at SSW on 3/6. Apparently they are still having problems with the HV tanks. You can contact Cox and they will send you a replacement.
They seem to fly OK with the supplied engine once the tank is replaced.
If you decide to go with the Norvel .061, that should REALLY make it Hyper.

George

(in reply to gcb)
       Post #: 11

RE: Cox Hyper Viper - 3/11/2005 8:52:52 PM   
green river rc



Posts: 861
Joined: 6/18/2002
From: Raywick, KY,
Status: offline 		I wonder what is wrong with the tanks? It would be great if we could use the supplied engine and save my Norvel for a real plane. ("real" as in balsa) I'll look them up this weekend.

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With the parts left over, I'm going to build a motorcycle.

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       Post #: 12

RE: Cox Hyper Viper - 3/12/2005 2:18:50 AM   
gcb



Posts: 2385
Joined: 10/24/2002
From: Port Ewen, NY, USA
Status: offline 		I think I read that the problem is caused by assembly glue blocking the line, but that may be wrong.
Some good planes for your Norvel might be some of the Dick Sarpolus sheet wing profiles that were originally powered by TeeDee .049's. Flying Models has an online list, I think.
Another possibility would be any of the Golden State 1/2A planes with built-up wing and profile fuselage.
Also, the Brodak 1/2A Flite Streak would be good. I think most of the other Brodak 1/2A's are for Bee type engines.
I build about 1/2 kits and 1/2 from plans.

George

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       Post #: 13

RE: Cox Hyper Viper - 3/17/2005 4:43:29 AM   
Aeromaniacs



Posts: 4
Joined: 2/4/2003
From: CA
Status: offline 		Wing is warped! I had to glue a trim tab on the outboard wing on mine, to get it to fly level. Look to see if the outboard wing is high or low.

Add more tip weight. Put the leadout wire on the last 2 hole. Make sure the leadouts are a little behind the C.G. Mine was actually ahead.

Video of stock Hyper Viper does some basic manuevers on my web page: www.aeromaniacs.com

(in reply to green river rc)