fox 35 fuel

[philip metzner]

I have been involved with model airplanes for about 40 years, but not with fox engines. My experience with them began about 2 years ago and I have been plagued with terrible performance. I was running home brew fuel made by starting with a quart of Backyard Basher 20% and adding methanol and Castor to make a gallon of 5%-29% all measured by volume. Last week I ran out of fuel and borrowed some from my son. It was 10%-23% from brodak. I figured it was lite on oil but tried it anyway. Man what a difference. None of my three fox engines have ran that good for me, just perfect. I made up some more fuel out of the basher, but made it 10%-26% and it runs great. So my questions are, do fox 35's not run good on 5%-29%, or is there something wrong with mixing basher fuel like that? Even though my math was checked over and over on that mix, is there some reason I wasnt getting the percentages I thought I was?

[kenneth cook]

           I personally use 5% - 10%  11 / 22 GMA blend Powermaster for my Fox's. I  personally never look back at using high percentage all castor fuel. Everyone in the Philly Fliers that runs Fox .35's use this fuel and they're run hard. I've never witnessed a failure due to this fuel and this has been going on WEEKLY for 10 years. Myself and others fly year round. I want to know why our engines haven't gone KAPLOOEY!!! as all others claim. I see this fuel being used in older Fox's as well. Ken

[Robert Zambelli]

What Ken says!

I have been running Powermaster 10-22 and Brodak 10-23  (both perform the same) in ALL my glow engines, mostly Fox 29s & 35s.
I have run very old high-time Foxes as well as breaking in brand new ones with these fuels and NEVER had a problem.
People have told me that if I run these fuels in an old Fox that has had nothing but Superfuel run in it previously, it will ruin the piston/liner fit.
I consider this to be total nonsense since I have never experienced any sort of performance degradation in the last 10+ years of use.
Something that I did find most interesting is that with the newer fuels, I have seen much less wear on the front bushing.
I runs some of my Foxes screaming lean with small props, others in more typical classic style stunt (2-4 break) runs.
My Stunt Rocket has a plain bearing ringed Atwood Triumph. I broke it in from new with Powermaster and after well over 300 flights, the fits are like new, including the front bushing.
The fuel works perfectly.

Bob Z.

[Dick Pacini]

I have been involved with model airplanes for about 40 years, but not with fox engines. My experience with them began about 2 years ago and I have been plagued with terrible performance. I was running home brew fuel made by starting with a quart of Backyard Basher 20% and adding methanol and Castor to make a gallon of 5%-29% all measured by volume. Last week I ran out of fuel and borrowed some from my son. It was 10%-23% from brodak. I figured it was lite on oil but tried it anyway. Man what a difference. None of my three fox engines have ran that good for me, just perfect. I made up some more fuel out of the basher, but made it 10%-26% and it runs great. So my questions are, do fox 35's not run good on 5%-29%, or is there something wrong with mixing basher fuel like that? Even though my math was checked over and over on that mix, is there some reason I wasnt getting the percentages I thought I was?

That is strange because the recommended fuel for a Fox 35 is Fox Superfuel which is 5%/29%.  You didn't indicate if the engines you started with 2 years ago were new or used.  If used, you can't be sure what fuel they were fed.  The other issue might be with the home brew fuel.  I don't know if Superfuel 5%/29% is measured by weight or volume.  It is my understanding from reading Randy's sticky that the method may vary from vendor to vendor.

[kenneth cook]

                       Hello Dick, just for the record I'm not starting a dispute of what and what doesn't work. I'm sure this thread will eventually turn out that way. I'm just conveying my findings. Yes, I'm aware of what Fox states in the instructions. Fuel has come a long way in the past 40 years.  I've personally seen Bob Zambelli's Fox's run and I've seen some of his 60 yr old vintage running on the same fuel as I stated above. Bob also has several collectible vintage engines. They've all run on Powermaster GMA or Brodak 50/50 fuels.  These engines also have the same old school  metallurgy like the Fox and they run flawlessly on GMA Powermaster. I've witnessed many other vintage engines running on this fuel. If this fuel is so harmful, I need an explanation as to why the engine didn't self destruct. These engines aren't just run one time on this fuel either. I see these planes run daily. I've seen engines and I have Fox engines from the 50's that I've switched over to GMA Powermaster. The consensus will say you can't do that as it will remove all the varnish off of the piston sleeve leaving you with an engine that has no compression. I subscribe to the show me theory. I hear it constantly and it's just that hearsay. We run Fox's hard whether it may be sport flying or Foxberg racing which your brutalizing the poor engine. It hasn't ruined my Foxberg racer. I also have taken my best Fox's to participate in the event using the fuel I'm describing. I can only suggest to follow what you feel is correct for you. I'm not telling you to run out and purchase this fuel. If pilots feel they need 29%, so be it. If your looking for steady reliable and useable power from your Fox.35, I would suggest trying Powermaster GMA fuels. This topic is readily discussed on here and I would like to know how this fuel (Powermaster GMA 11/22) has harmed their engine. My tests have been with new and also used engines and I've yet to see the destruction that some claims is going to happen. Ken

[Dick Pacini]

Hello Ken,  I am not trying to start a dispute either.  I responded to the original question in an attempt to help.  I can't speak from experience with fuels since I am a retread from 37 years ago.  I haven't run a Fox since the 60's.  My last engines were OSMax 35's.  I used to run Superfuel in them but switched to K&B 100.  I used that until my modeling retirement in 1975.

That being said, I have been on this forum for a few years, posting some and reading lots.  Fuel issues have been brought up many times.  I have read and re-read Randy's post on fuels and engine life/performance.  Lots of data there but he cautioned against shorting any old technology engine on castor oil.  He also described the problem with mixing oil by weight vs volume.  He also offers suggestions of other fuels suitable for old tech engines.

[kenneth cook]

                       Dick, I agree with what Randy says as well. I'm not suggesting that you shouldn't run the high castor fuels. I personally don't mix my own fuel. The results that I experience with this particular fuel is the same from can to can. I've never experienced a fuel related problem. I truly believe homebrew mixing just isn't worth it to me. I'm just letting you know what to expect in the future of repeated runs using high percentage castor fuels. I'm also stating that GMA Powermaster 11/22 works and it doesn't have an oil content of 29%.  I honestly got tired of bringing two different fuels with me to the field. I used to run Sig Champion 5%-25%. I had good results using this fuel until one day the engine just didn't seem to have the power it once had. After several more flying session attempts I recognized how the engine now had a bind in it. This bind was a direct result of having to much varnish and carbon in it. This isn't a just a simple task of taking the engine apart and just wiping it off. I generally run muffler pressure and the high castor fuels will totally cake up the pressure fitting as well. My initial experiments were done with a 1980's version Fox .35. Let's face it, the Fox by no means is an expensive engine. A new Fox can be purchased today directly from Fox for slightly under $50.00 with any old engine in trade. My thoughts were if something bad in fact did happen, trading it for a new one would be my choice. My engine has been running fine and I never needed to replace it. Leaving a Fox dormant for months can also glue the rod to the wrist pin. I've had to replace backplate gaskets, during this process I'm just amazed at how free the rod floats back and forth on the wrist pin with engines run on this fuel. Ken

[Bill Little]

Hi Guys,

I am totally sold on what Randy says in his post at the top of the section about fuels.  I used to run all castor, 25% to 29% in all my old engines.  He recommends a blend with the total oil about 25%.  Adding about 4 or 5 ounces of castor to Sig Champion gets the oil up to those recommendations.  Some castor is important for cooling and high heat protection, but all castor isn't needed.  Things HAVE changed since 1948..........

(Plus, I add an ounce of Randy's "Snake Oil" to all my gallons of fuel)

BIG Bear
RNMM/AMM

[Jim Thomerson]

I've been running Sig Champion 10% nitro, 20% oil, half and half in all my glow engines for about the past 20 years, and I am quite happy with it.  I have put several hundred flights on one of my 1977 Fox stunt 35's recently with this fuel, and it has fine compression and starts and runs to suit.  I put one lean run on it such that it heated up and stopped in flight.  No harm that I can tell.  I am pleased that there are other heretics out there.

[L0U CRANE]

To all,

I have seen rare bad results from all- or half/half synthetic/castor fuel blends. The worst was when eternally dependable K&B fuels went all synthetic, some time in the mid-late 1970s. They still carried the traditional all-castor K&B 100, 500 and 1000 blends, but hyped their new miracle X2C oil vigorously.

Zero castor.

I'm not the only one who commented on near-destroyed innards. Usually a new sleeve and piston brought the engines back, if you then used a some-castor fuel.

As to "cleansing" the coating off well-baked Fox iron engines, there was another 'miracle' goody that worked right when used right, but not on lapped iron in steel Fox engines. That was Microlon, early 1980s. It was a system type of thing. You dribbled in a measured number of cc's while the engine was fully hot, two-stroking. A chemical cleanser in the Microlon 'stripped' all varnish or residues off the sleeve and piston, then a hi-tech polymer (also a component) burnished-into the working surface.

You could hear the RPM bog while the cleansing and burnishing occurred, then there'd be a several hundred RPM rise. This was claimed to be a 'durable' surface treatment for several hours of use. Seemed to work OK with ringed piston, chrome or hardened sleeve engines, and possibly with ABC or similar, but didn't last very long. I had to rebuild the varnish on several "mature" Fox 35's...

I later heard that full-size dragsters and hydroplane racers found it useful setting up for each run. That was years ago. Haven't heard much about it lately.

As several have found, for one thing - Mfr instructions do work. For another - Other approaches also work. IMHO, initial break-in can affect engine durability and dependability, whether scrupulously going by the mfr instructions, or consistently with another proven fuel blend and manner of using the same engine type.

A well-broken-in engine with several hours on it is probably much less likely to be damaged by one over-lean run - the fits have had ample time to 'learn' each other...

[kenneth cook]

                        Lou, please don't take offense to this. Your providing me examples of products that are 30-40 years old. I'm directly speaking in regards of one currently available product in particular, Powermaster GMA 11/22 fuel. Jim Thomerson has expressed his results as well using Sig 50/50. Were explaining our results with our oil contents. In both cases, our fuels are NOT 100% synthetic but a blend of castor and synthetic.  Philip asked whether or not the 29% oil made the engine run better. My answer to that would be no. I personally would've used the fuel he initially started with without mixing any additional oil or other fuel to it which was Brodak 10-23. I do have experience using Brodak 10-23 running in a Fox.35 as this is one of the contest provided fuels available at Brodak's. You have a choice of contest provided 50/50 or all castor fuels for the racing event. These engines are now being exposed to lean runs for the duration of the race.  I prefer Powermaster myself and the majority of my engines have spent there lifespan consuming it. Ken

[philip metzner]

  Thanks to everyone here for your input. It has been a big help. The way I see it now is, if fox stunt engines in general will run well on 5%-29% superfuel, then there was something wrong with my fuel mix. The methanol I bought from the drag strip may have been bad or the percentages of the basher fuel I used for the base are not correct. At any rate I wont be trying that mix again.

[Steve Helmick]

                       Lou, please don't take offense to this. Your providing me examples of products that are 30-40 years old. I'm directly speaking in regards of one currently available product in particular, Powermaster GMA 11/22 fuel. Jim Thomerson has expressed his results as well using Sig 50/50. Were explaining our results with our oil contents. In both cases, our fuels are NOT 100% synthetic but a blend of castor and synthetic.  Philip asked whether or not the 29% oil made the engine run better. My answer to that would be no. I personally would've used the fuel he initially started with without mixing any additional oil or other fuel to it which was Brodak 10-23. I do have experience using Brodak 10-23 running in a Fox.35 as this is one of the contest provided fuels available at Brodak's. You have a choice of contest provided 50/50 or all castor fuels for the racing event. These engines are now being exposed to lean runs for the duration of the race.  I prefer Powermaster myself and the majority of my engines have spent there lifespan consuming it. Ken

Doesn't Powermaster still make GMA 5/29 and 10/29 all castor? They usta make GMA 15/29, but not sure if they still do. It is a proven fact that those iron/steel engines will survive ok if broken-in on an oil blend, but not happy if changed from all castor to blend. The varnish is removed, and that is either creating the seal, or else when the varnish residue is run through the engine, that chews away at the metal. Your choice. I like newer engines with good, bolt-on mufflers, and they happen to like synthetic oil alright. I still use a mix of synthetic and castor, not always 50/50.  Steve   

[Arlan McKee]

I runs some of my Foxes screaming lean with small props, others in more typical classic style stunt (2-4 break) runs.
My Stunt Rocket has a plain bearing ringed Atwood Triumph. I broke it in from new with Powermaster and after well over 300 flights, the fits are like new, including the front bushing.
The fuel works perfectly.

Bob Z.

Not quite what you said here....   http://stunthanger.com/smf/index.php?topic=1651.msg11129#msg11129



"My only complaint on both was that they did not exhibit the classic Fox 2-4 break. On a whim, I ran some 5% nitro, 29% straight castor in the newer engine, which was then mounted in a Nobler. Instant classic 2-4 break – exactly as I remember. 
Switching back to Powermaster, the break went away.   
 
Anyone else have a similar experience? By the way, I still have both engines and they have excellent compression.  I would not hesitate to put either in a classic or old-time plane.
 
Bob Z.”

[kenneth cook]

                   My point regardless of run style is the fact that this fuel isn't going to degrade or ruin your engine. I believe strongly that what said is going to happen is a fallacy. It hasn't happened to me and I know for a fact it isn't going to happen. My results are strictly with Powermaster GMA fuel.  My Fox 35's not only have survived the concocted fuels I ran on them 30 years ago when they had a strict diet of dirt from ground pounding and whatever commercial fuels were available. So the theory that older engines are going to be ruined is proven negative on my end. I've purchased many 1950's large bypass Fox's that I've subjected to this metal degrading piston ruining fuel. Maybe I just own some of the hardest iron pistons and crank bushings that Fox ever produced. The mystery of whether or not 29% all castor fuel is NEEDED  to run your Fox.35 once again continues. Ken

[L0U CRANE]

Ken to your #10 and #14...

No offense taken. There was a post that included the thought that there never was any harm to an engine from lower total % and blended castor/synth oils. My comments, I'd hoped, made clear that there were a few - repeat few - occasions in the distant past.

They did happen, way back when, and in the K&B X2C fuels example, it was a big disappointment...

We may understand better how to use our engines  these days, and the quality of manufacture has improved a lot, too, in both fuels and metal.

I'm still leery of running a simple engine like a Fox Stunt on a modern CLPA fuel; old habits die hard. Most comments stress a good quantity of castor, occasionally even adding castor to a modern half and half fuel - to bring the total oil % up a bit.

It's a bit of added fuss, but castor is still very good at what it has always done. The newer oils are great, and I did close my earlier post with the thought that a well-broken-in engine with decent time on it will be less susceptible to damage from an occasional over-lean run.

What's the oil package in PowerMaster GMA? Total over 25%, more castor than synth? (I used to know, but it may have changed since I last checked.) It is a good fuel for iron-in-steel engines. 

We still have a hobby activity here. I think that includes some freedom to do what we choose, and accept that not everyone does it our way.

[Robert Zambelli]

Hi, Arlan - you are 100% correct in stating that post from August, 2006. I ran the engine for the rest of the season and into 2007. Midway through 2007, the engine started to become very tight and difficult to start. Removing the engine I noticed not only was the the exhaust port partially blocked with carbon but the piston was black. The plane did not fly again until the fall of 2008. Since I had another brand new Fox 35 (same model), I decided to give it a try. I ran it in on Powermaster 10/22 and noticed that it required around two hours of running before it performed well. After a number of flights, I tried Brodak 10/23 and it performed well. I now have around 300 flights on the second engine and it runs extremely well. I never experienced the unacceptable runs that I had on the original Nobler engine using the Powermaster fuel. The runnning characteristics were fine so I'm still running the same setup.

Bob Z.

[Terrence Durrill]

WHAT IS THE SOURCE FOR POWERMASTER FUEL?......ANY SUGGESTIONS ON FINDING A CASE OF 10/22 FOR MY FOX .35's.        

[Arlan McKee]

What Ken says!


I have run very old high-time Foxes as well as breaking in brand new ones with these fuels and NEVER had a problem.
People have told me that if I run these fuels in an old Fox that has had nothing but Superfuel run in it previously, it will ruin the piston/liner fit.
I consider this to be total nonsense since I have never experienced any sort of performance degradation in the last 10+ years of use.

Bob Z.

Hi, Arlan - you are 100% correct in stating that post from August, 2006. I ran the engine for the rest of the season and into 2007. Midway through 2007, the engine started to become very tight and difficult to start. Removing the engine I noticed not only was the the exhaust port partially blocked with carbon but the piston was black.
Bob Z.

So which is it? Never had a problem or removed a very tight, hard to start, carboned up, black piston engine?

[larry borden]

Powermaster was bought by VP Racing Fuels. VPracingfuels.com   powermasterfuels.com

[L0U CRANE]

To Bob Z., post of Aug 15...

...With apologies, Kenn... 

Mid-2000's, eh?  I had a similar incident in the 1980's with a SIG fuel. That was long before the castor oil quality flap, which quieted down long before your incident.

Fuel still came in metal cans when mine occurred. I didn't much look at the fuel until after the flight when sparks came shooting out the exhaust and the (Fox 35) sounded very strained. Mine was also coked heavily in the exhaust stack, and the engine was "rather hot" when it came down, seized.

Near as I could figure, the castor oil had "turned". The fuel was black and opaque. I'd added about 5 fl oz to a new gallon of  a SIG sport blend, and found that the entire gallon of castor I'd picked up to fatten sport fuels for Stunt 35s had 'gone.' Later, I read somewhere that castor oil CAN turn into a very dangerous form, highly flammable and dirty burning - or did I imagine that?

I did rescue the engine, but that flight sure wasn't fun. Fortunately, I was flying on a paved parking lot. No wildfire.

Today, we can see the fuel color through the plastic bottles. That was the only time I'd had a problem with SIG's AA Castor, and I still use it to brew up diesel fuels - as long as it is champagne clear... Diesels don't coke-up like glow fuels may, but I'm still thinking of trying some synthetic in the oil fraction...

Other fuel producers have had rare problems in the long distant past - like a batch of RC fuel that had no oil in it. Ah, history...  worth learning so that we don't repeat its worst events...