Fuel for fox 35 - RC Groups
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Feb 06, 2013, 04:14 AM
alf.g's Avatar

Fuel for fox 35

I was very fortunate enough to purchase a NOS fox 35 (50 anniversary edition) and a vintage TF gieseke nobler. (1978) what fuel is recommended to run the fox and will commercially available fuel be suitable for that particular ie; synthetic fuel blends.
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Feb 06, 2013, 08:56 AM
Registered User
The usual recommendation is 0 -10% nitro, and 25-29% castor oil. I have been running Sig Champion 10% nitro, 20% oil, half synthetic and half castor. This is below what most experts will recommend, but it is working fine for me.
Feb 06, 2013, 10:33 AM
I am 5' 8" the Taube is 7' 4"
Clancy Arnold's Avatar
The safest thing is to call FOX and order it from them.
Feb 06, 2013, 01:16 PM
Old Timer
The Kiwi's Avatar

There is fuel, after all, and there is FUEL

As anyone visiting here regularly surely knows by now, I got to be George Aldrich's friend when we were both in our 20s (of course, at different ends of that decade of life). I took an engine to him for some work after I had moved away from here, and was only seeing him at contests around the state.

I don't think it was a Fox, but under the skin, a close cousin; as I recall, it was one of the first of my several OS Max-S 35s (cloned from the Fox 35, with higher quality, except the con rod). Whatever engine, it was one with a steel liner and iron piston. He asked me what fuel I used, and I told him K&B 100, original type.

He remarked that the K&B only had 20% castor, so what was I doing about the "other 8-9 % of oil" it needed? I wasn't doing anything at all, at the time. I got a lecture about making engines last, and he pulled out a couple of his own old Foxes, with some caked on brown-black burned on castor (he said it gave them "character" or something) and put props on them, then showed me how good the compression still was, after thousands of hours of running.

When mufflers were becoming common in the 1970s, I tested my older engines, like the Fox Stunts, McCoy 40, and Max-S 35s on most of the readily available aftermarket mufflers of the period, and they all ran "poorly" on those. However, I included some tests comparing fuels when running mufflers, and was happier by far with "High oil" percentage mixes.

Getting good engine runs had been problematic on fuels with less than 25% oil. The needle settings were much less critical, rather like how added Nitro helps broaden the needle range, and with the really restrictive early mufflers, 15% Nitro instead of the usual 5-10% was actually cooler running somehow (I think that I figured out why, but can't recall what I deduced back then).

Incidentally, several of the more modern Schneurle ported motors that I have used for sport and stunt wouldn't run cool enough to empty a fuel tank without running faster and faster as they warmed up further, making the last quarter of a stunt pattern badly stretched across a lot more sky than I wanted. But add enough Castor to whatever fuel, to reach 25%, and they suddenly were perfectly happy to run the same for the entire seven-eight minutes.

Long story coming to an overdue end, I use a mix of Castor and Synthetic oils, half and half, 25% as a percentage of volume, not of weight, for almost all my sport and stunt motors (including every iron and steel dinosaur engine I might use).

Feb 06, 2013, 03:49 PM
Registered User
You really can’t go wrong adding more castor oil for an old glow steel engine.
More oil may trade off a little top end power and leave more “goup” on your model, assuming you don’t overly lean it out. I can’t remember for sure, but I think the old Fox fuel was 29% castor oil.
I used to add at least an extra 4 to 6 oz of castor per jug of glow fuel.
A friend of mine once gave me a gal. of rancid castor oil he was going to throw out. I diluted it 1:1 with methanol, shook it up and re dissolved the solids into solution and also used that mix at 8 to 10 oz per jug in a K&B .61 R/C which is still fine and run able to-day.
Better to worry about not enough oil (castor) rather too much.
Feb 10, 2013, 06:48 AM
warrenlead's Avatar
I've always run my Fox 35 in my '57 Nobler on 29% Oil (50/50) and 10% Nitro and it has always been good to me.
Feb 11, 2013, 06:02 AM
alf.g's Avatar
Thanks for all the replies gents. Seems like Fox engines like to run on high percentage oil. point taken.

What would be the correct break in procedure?

Building of the Nobler is proceeding well. !
Best regards to all who repled
Last edited by alf.g; Feb 11, 2013 at 06:13 AM. Reason: break in procedure
Feb 11, 2013, 06:26 AM
warrenlead's Avatar
Some good Fox 35 tips here... http://www.webring.org/l/rd?ring=con...2FFox_35%2Ephp
Feb 11, 2013, 07:03 AM
alf.g's Avatar
Originally Posted by warrenlead
Bingo !
Answers all my question!
Many thanks
Feb 11, 2013, 02:28 PM
Registered User
If memory serves, Nitro detonates cooler than alcohol burns.
Feb 12, 2013, 11:13 PM
Registered User
downunder's Avatar
Nitro detonates at roughly 1/3 the compression that methanol can handle but nitro burns hotter than methanol. This extra heat of the gas in the cylinder gives more pressure on the piston and so gives more power. Basically .
Feb 15, 2013, 11:14 PM
Registered User

Fuels for C/L

Let me recommend the Brodak 10-29 fuel. I and my friends have really been pleased with the product and we've been flying beginner stunt moves with Fox .35's, and OS 40FP's for the most part.
Feb 16, 2013, 06:48 PM
Barnwell, SC
Originally Posted by propaplace
Let me recommend the Brodak 10-29 fuel. I and my friends have really been pleased with the product and we've been flying beginner stunt moves with Fox .35's, and OS 40FP's for the most part.
I agree. This fuel works very well in the Fox .35.
Feb 16, 2013, 07:45 PM
Old Timer
The Kiwi's Avatar

All-castor fuels

That's eight tanks' worth. I remember buying only quarts, when I was fourteen, and only pints, when I was twelve, but when I reached seventeen, although I actually flew less frequently (cars, sports, girls, and homework reduced my modeling time), I still was buying gallons at a time, not quarts.

I stopped buying all-castor fuels when I was about 35. For Iron pistons, I still want half castor out of 25% by volume.

The K.
Feb 16, 2013, 08:21 PM
alf.g's Avatar
Thanks to all. I have just located some high percentage castor only fuel with 5% nitro content. I would however like to get my hands on the brodak fuel but would be hard to find a supplier here in Australia.
Motor is mounted in plane now but will retrieve it for running in procedure.
On another note my gieseke nobler is almost complete and is ready for covering. I must add that the kit has not been a favourite of mine and have changed quite a few things. Early kit I realise (1978) but am glad build is almost over. !!

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