Fox 35: How much nitro for what sized ship?

[Chris Gilbert IRL-1638]

Guys,

the Fox/25LA thread got me thinking (always a bad thing). One of the posts remarked on running a Fox 35 in a 600 square inch ship with high Nitro.
Assuming we have a box standard Fox 35, how much nitro do/were people using for a given wing area - all other things being equal, and assuming we're talking about aerobatics not racing/combat.

e.g.

400 sq in or less
500 sq in or less
550 sq in or less (Nobler sized)
600 sq in or less
greater than 600 sq in

Chris

[Andrew Hathaway]

I use to run 5% in all my Fox 35s, but a few years back I switched to 10%.  Seems to work better all around.  I still wouldn't try to make a Fox fly a 600sq in plane.  That's just asking for trouble.  Over 500sq in I'd use the OS 35S, closer to 600 I'd probably be thinking G21 .46 or G51. 

[Ralph Wenzel (d)]

Steve Wooley (Cobra) is supposed to have used around 25% Nitro in that Fox .35 to get it to pull that huge (for a Fox .35) plane.

[wmiii]

Actually it was a Fox .29 with 2 extra head gaskets.

Walter

[Phil Coopy]

I've used up to 25% in a profile Ringmaster......it doesn't make a whole lot of difference on a plane that light.  Maybe it's more noticable on a heavy plane.

Phil

[John Stiles]

Actually it was a Fox .29 with 2 extra head gaskets.

Walter

WHUT You mean to say, that a Fox .29.......with two extra head gaskets.....let that Fox engine run 25% nitro, powering a bigger than recommended sized plane, effectively and not detonate the piston? I'm amazed....what did the extra gaskets do, besides lower the compression ratio? Help me understand this....I may experiment with a certain older engine or two I have laying around.

[Brett Buck]

WHUT You mean to say, that a Fox .29.......with two extra head gaskets.....let that Fox engine run 25% nitro, powering a bigger than recommended sized plane, effectively and not detonate the piston? I'm amazed....what did the extra gaskets do, besides lower the compression ratio? Help me understand this....I may experiment with a certain older engine or two I have laying around.

   I would be surprised if you would have a severe problem with detonation running 25% with stock compression, at least in a 35; I'm not sure about a 29, it may be higher. The 35  (and a lot of similar stunt engines) are nowhere NEAR the limit on compression, quite the opposite in a lot of cases. Running more nitro makes a *dramatic* difference in the power on a 35 - I ran 5% for years until I ran out one day, and ran some Cox "Blue Can" 15%. It really woke the engine up - and, oh, by the way, I ran out of fuel about 1/2 way through the pattern . One thing you can notice right away, particularly back in the good old days with no muffler, was that it is *much* louder with a much "sharper" exhaust note. If you still use a stock crank, might want to carry a few spares with you, but you can really get a lot of performance increase with nitro.

      A little bit of inside information - even on pretty high compression TP motors lots of people run as much as 20% nitro with no changes to the rest of the engine. And they are a lot closer to the edge than Fox 35s.

    Brett