Filtration

[Randy Ryan]

Just reading through the fuel filter thread and a thought came to mind. We filter our fuel before the tank, after the tank and sometimes we filter the air going into the engine but one thing we seem to neglect (at least as far as I've observed) is the tank vent air. Our tanks suck in anything that's in the air, dust, lint, pollen, feather down, etc etc. Anyone else ever considered this? Thinking about it, it seems to become clear too me that despite my efforts to keep the fuel supply clean, I invariably end up at some point having to remove the needle and removing some chunk of swarf and wondering where the heck it came from. It must be coming from the vent air and it has only one way out, right through the NV. I think I am going to start filtering the vent air.

[Russell Shaffer]

Someone posted about doing that after he removed a bug from the NV.  It's a good idea that would be very easy to do. 

[Randy Ryan]

Someone posted about doing that after he removed a bug from the NV.  It's a good idea that would be very easy to do. 

That could also happen while the airplane is hanging on the wall. Another good reason for filtering the vent air or at lease covering it between flights.

[Jim Thomerson]

I have a KK one way valve in my uniflow vent.  It has a tiny hole.  I remember at a contest, one of the guys slow rat had the tank full of small insects.  Needless to say, he was unable to race.  Capping an open vent is a good idea.

[pipemakermike]

I started this fuel filtration topic because during 2009 it seemed that every flight I had was spoilt by engine problems.  I struggled on for all the competitions that year and spent many days trying different things. New tank, Thunderbolt plugs, new fuel, different engines (3 different ST 51s 1 Eyna 45 and 1 LA 46) with little improvement. In 2007 and 2008 I had generally good to very good engine runs but performance was dropping off by the end of 2008. The failure of the paint job in the replacement Legacy 40 to be powered by a Rustler-Merco 51 was the final straw and I gave up and went back to music and locomotive design.  Now, the locomotive work is coming to an end (the locomotive is well on the way to completion and my work should be finished at the end of March). Now I want to get back into stunt competitions so I am starting again. One thing that came up in conversation with an active competitor friend was that a number of UK flyers had suffered with similar problems and these were traced to some sort of contamination in the fuel and most probably in the castor oil.  Looking at the stuff found when fresh fuel was filtered using a fine stainless steel filter it seemed that there was an accumulation of tiny thread like particles and it is possible that I was suffering from the same problem. I know that my friend takes enormous pains to filter his fuel and I plan to do the same.
In order to start from a clean sheet I washed out the tank I was using for my last flight in 2009 when the engine stopped inverted and the landing stuffed the vent full of earth.  I was astonished how much muck I removed.  The pictures show the first 2 of the debris filtered out of the tank.  I half filled the tank with methylated Spirits shook it well and poured the result through a kitchen towel filter before repeating with the filtered spirits.  I repeated this until no debris was found.

[Lauri Malila]

Mike,

I have had the same problem many years ago and the cause was in bad castor oil. I don't know what the actual reaction is, some chemist might know.. I guess it's either oxydation or something to to with UV rays or storage temperature. Or just bad processing at the factory.
Anyway, we found out that the oil formed small "fibers" that were floating in the fuel. When fuel was filtered, they soon appeared again which means that once this reaction starts, it's not possible to stop it.
The only solution is to get rid of that oil and get some better quality stuff.
Knowing you, I think you are smart enough not to make tanks from brass sheet. Brass can also cause some weird green stuff form inside the tank.

Lauri

[Garf]

They had a bad problem when they changed the extraction method to solvent extraction rather than pressing at one point. 

[Steve Helmick]

Bruce Hoffman ("HOFFO") sent me a homemade air filter for the uniflow inlet, along with payment for the Saito 72 I sold him.  I haven't found his filter in my 'stuff' yet, but if I can find it, I'll use it. Otherwise, if I find the Master Airscrew plastic fuel filters, I'll plug one of those on. They're not trustworthy for fuel filters, apparently. But they're small and light, and I think they'd be perfect for uniflow vent air filters. Might need to flush them out once in awhile.  Steve

[Brett Buck]

They had a bad problem when they changed the extraction method to solvent extraction rather than pressing at one point. 

  Red Max had a bad problem with it, no one else did.

    Brett

[Peter Grabenstein]

Mike,

I have had the same problem many years ago and the cause was in bad castor oil. I don't know what the actual reaction is, some chemist might know.. I guess it's either oxydation or something to to with UV rays or storage temperature. Or just bad processing at the factory.
Anyway, we found out that the oil formed small "fibers" that were floating in the fuel. When fuel was filtered, they soon appeared again which means that once this reaction starts, it's not possible to stop it.
The only solution is to get rid of that oil and get some better quality stuff.
Knowing you, I think you are smart enough not to make tanks from brass sheet. Brass can also cause some weird green stuff form inside the tank.

Lauri

Hi Lauri

Sure you got some old and wrong stored (sunlight) castor oil.
Not to forget, I allready mention this in an another thread,
copper tubes also builds up corrosion in and outside which tiny small particles can blockade the NVA.
Thats why I allways use 2 filters inside my tinplate fuelcan.
One filter at the Syringe and one filter between tank and engine.
Never had problems with unstable erratic engine runs.
I prefer "Reely" fuel filters.
They are smallsize and reliable.

Peter GER-1223

[pipemakermike]

Mike,

I have had the same problem many years ago and the cause was in bad castor oil. I don't know what the actual reaction is, some chemist might know.. I guess it's either oxydation or something to to with UV rays or storage temperature. Or just bad processing at the factory.
Anyway, we found out that the oil formed small "fibers" that were floating in the fuel. When fuel was filtered, they soon appeared again which means that once this reaction starts, it's not possible to stop it.
The only solution is to get rid of that oil and get some better quality stuff.
Knowing you, I think you are smart enough not to make tanks from brass sheet. Brass can also cause some weird green stuff form inside the tank.

Lauri

Hi Lauri
Yes that is what was found in Brians fuel and probably caused problems in others fuel.  Brian thinks that the problem has gone away now as he hasn't seen the problem for a year at least and I plan to mix fresh fuel for my return to stunt.
One thing that I have remembered is that I have brass mounting tubes in the tinplate tanks but the cleaning process didn't show any green verdigris just the brown muck shown on the filters. I think that this is most probably the result of the inverted landing plugging the air inlet pipe with mud and, as I just connected the feed tube to the inlet pipe to seal the tank and it had the best part of 3/4 of a tank of fuel trapped in it, I guess that some of the mud had been dissolved by the fuel in the tank while it was hanging on the wall.

[Randy Ryan]

Well, so much for that question