Engine basics > Engine set up tips

Cobra Fox35 setup

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Dennis Toth:
In a post on FB they had the February 1971 American Modeler with Steve Wooley's Cobra. In the article Steve gave some information about how he setup the Fox. Basically, he added one head gasket and OS NVA. He says not to reduce the diameter, (assume this puts it like an ST NVA). He also recommends using 20% nitro fuel, a 10x5 prop (in the photo's it looks like a Rev-up fairly wide blade) and a long reach Fire Ball cold plug. His reasoning was that with the larger diameter spraybar you get better fuel draw and the higher nitro gives you back the power. He does not say what run style he prefers but it is the 70"s do likely 4-2-4. Maybe someone can add to this.

Best,    DennisT

Air Ministry .:
Well , if you throw the muffler away , and get a cold long reach fireball plug off of brodak ( I just tripped over them , just previous  - from the plan wtd. thing in C'fied here )

youll soon know , provided your engines run in right .

Intresting the Cobra 7 , Juno , Bob Hunts derivitives etc , stemed from this . Youll get a vicious circle with a muffler , tho titanium might help .


He mustve known something , my finishes are good for Six Months !  :(

The Talka   7 / Akrobat 7,  is a Fox .35 ' development '  a .42 . A bit taller & longer - so it sits a bit further back , helps the C.G. if you had one ? .

He could be being cunning & witholding information . Might be a 11 x 5 T/F , with the ends gone . Trimmed . Tho I think your right & its one of those extra wide things .

Dennis Toth:
The Cobra setup kinda goes against what was/is considered to be maybe not etched in stone but at least etched in balsa - hot plug, higher compression head, 10% nitro (more seems to break crankshafts with stunt props). Did anyone else fly with Steve and use his Cobra setup on a Fox35/29, how did it do?

Best,   DennisT

Steve Helmick:
Who's got the diameter specs for the stock Fox .35 Stunt and OS .35S (I guess we have to assume that's the one) spraybars? I know both are smaller than the 4mm/.156" Super Tigre (etc.) spraybars that I like to use. The Fox .35 has a huge venturi...around .300 > .305, IIRC. More than big enough for a .60 or .75.

I don't see a good reason to lower the compression of a Fox .35 Stunt, run a cold glowplug, or run a Fireball glowplug for that matter.  D>K Steve

EddyR:
 I saw Steve fly quite a few times. I never saw him fly the one that always shows up in pictures. He must have had several over the years. I saw him fly one that had a bubble canopy. None were the light green color. These contest were at Buffalo and i would time my visits to my regional office there so as to go to watch contest. I think a Fox .35 in a Cobra is stretching the Fox to the limit. Some years later i built a cobra and started with a very good ST .35 but soon put in a ST .40. That was a great flying combination and very easy to fly in any conditions.
 A lot of people back then were running the Fox at it’s limit as models were getting larger. Many were using the McCoy .40 red head motor.   
EddyR

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