Fuel-tank power-flushing

roddie Sun Apr 02, 2017 9:01 pm

I had an idea today.. while posting in Bob's "Sacrificial Wen-Mac Kingcobra" thread.. for flushing old fuel-tanks. While some would ask; "why not just replace the tank?".. Sometimes a replacement-tank isn't available.. or the tank may be integral to the model.. (as in a plastic ARF) Regardless.. if it's been used and set-aside.. and possibly left that way for years (you probably have such tanks..) you know just how bad this can be.

Many of us flush-out our tanks with solvent.. and if we're "good".. we flush-out all of our used-tanks at the end of the season.. I'm not good.. Laughing

We all have old fuel tanks hanging-around. I have a glass jar full of old-used wedges that have been soaking in thinner for years. Occasionally I'll get my fuel-bulb out and flush them with the thinner they've been soaking in. The crap that "still" comes out of them, settles to the bottom of the jar. This is Roddie-overkill.. Laughing

but that's how I roll.

How about building a fuel-tank flushing-system! I've soaked my small wedge-tanks in solvent and flushed them with a fuel-bulb. That's nothing new.. but how about using a pump? I suppose that a crank-style pump could be used.. but how about an electric fuel-pump? Maybe a small manifold could be made for flushing several tanks at a time connected in a closed-loop. Power-flush the tank(s) outdoors for safety. Maybe install a pressure-regulator and even a cycle-timer. Just connect the flush-tubing in a loop.. and plug any remaining vent-tube.

The "tank-flushing-station" could be made using a Tupperware/Rubbermaid container with a snap-on lid to contain any solvent leakage.. with the pump being external.

Surely.. continuously-circulating solvent would clean better than a soaking.. wouldn't it?

roddie Mon Apr 03, 2017 6:44 pm

Thinking about this today; I realized that I forgot to mention the inclusion of a filter in the loop. Rolling Eyes

I'm not sure what type of pump would be best. I guess it would depend on the flushing-media. Maybe an automotive fuel-pump and regulator would be up to the task of pumping more aggressive thinners.. as well as having a continuous duty-cycle.

Making a compact system wouldn't be difficult. It could be powered by your field-box battery/power-panel; which already has the 12V fuel-pump connection and an on/off switch. A solvent-reservoir/vessel need only hold a few ounces of thinner.. and could possibly be made using a clean-spare fuel-tank.

If you wanted.. you could incorporate a "filter-bypass" into the plumbing. This would allow "reverse-flushing" via the panel's fuel-pump polarity (in/out) switch.. which might clear more debris from the subject-tank. After the forward/reverse flushing-cycle(s).. pump the solvent thru your filter. A see-thru filter would be ideal.. as this Sullivan #187 or similar.

Ken Cook Tue Apr 04, 2017 4:14 am

Roddie, while your idea would work, many of the old tanks have issues. I've posted many many posts on tanks. All I can say is just go for it. The problem with many old tanks is not going to go away and flushing isn't always the fix. Many of the tanks manufactured in the 60's-70's and even ones currently built are never properly cleaned after assembly. Flux eats away the plating, solder joints are compromised etc. I mention this all the time, NO PERFECT tanks have their pickup tube soldered internally. No you can say well I never had a problem with one, keep flying it and you will. This is more likely to be problematic to tanks that have been laying around, dropped on the floor, tossed in a box. Pipes get pranged, solder joints become loosened. Tanks especially older ones can be taken apart and repaired without wasting valuable fly time easier than the methods you want to procure. I can have a tank apart, soldered , cleaned and properly repaired in less than an hour.

KariFS Tue Apr 04, 2017 4:59 am

I have a couple of old wedge tanks that I would like to clean up. I was thinking about taking a heat gun to them to melt the solderings and then take them apart. Dremel and wire brush, or maybe citric acid or something to remove the rust and then re-assembly.

One (well at least one) question still remains: Should I protect the de-rusted areas with something? Originally the steel plate is tinned, I suppose I could try to re-tin it Huh...

Or would just some light oil (SAE10) be enough?

rsv1cox Tue Apr 04, 2017 6:51 am

Food for thought, but I never really had much of a problem with fuel contamination, maybe I have just been lucky or maybe I just run my tanks dry. A couple of months ago I resurrected my old scratch built "flaps" plane after years of rest, fueled her up (Enya .15, Perfect wedge tank) and she took right off. It's been my history. No in-line fuel filters either.

But, my (someone else's) "sacrificial Airacobra" perhaps was not so lucky. I thought I had flushed the tank out enough with hot Simple Green and hot water followed by a compressed air blowout but when I used wire as a guide to seat the fill/vent/supply nipples I noticed that when I removed the guide wire, a sticky gunk came out along with it.

So my plan is to just fill the tank with some Cox 25% and let it sit for a few days, then flush it out. A pump would be good here but I don't think the repaired nipples would stand the strain. If this was a serious effort rather than a "sacrificial" I would replace the tank, seems like one of Kim's 35mm film containers cut down would fit nicely in there.

getback Tue Apr 04, 2017 6:52 am

I have recently boiled one that was beeing stubborn in anti-freeze , and that fixed it up for what was testing , never had one apart should do it sometime just to see what the looks are inside / Smile

roddie Tue Apr 04, 2017 6:01 pm

Ken Cook wrote: Roddie, while your idea would work, many of the old tanks have issues. I've posted many many posts on tanks. All I can say is just go for it. The problem with many old tanks is not going to go away and flushing isn't always the fix. Many of the tanks manufactured in the 60's-70's and even ones currently built are never properly cleaned after assembly. Flux eats away the plating, solder joints are compromised etc. I mention this all the time, NO PERFECT tanks have their pickup tube soldered internally. No you can say well I never had a problem with one, keep flying it and you will. This is more likely to be problematic to tanks that have been laying around, dropped on the floor, tossed in a box. Pipes get pranged, solder joints become loosened. Tanks especially older ones can be taken apart and repaired without wasting valuable fly time easier than the methods you want to procure. I can have a tank apart, soldered , cleaned and properly repaired in less than an hour.

Lots of great comments here.. and yes; I've noted your advice and experience regarding the poorly-soldered tubes within the metal tanks. I saved your writings as Word docs when I was building my little Speed-tanks.

What's your method of off-season storage for your used fuel tanks?

Ken Cook Tue Apr 04, 2017 8:01 pm

For stunters, I really don't do anything. The combat and high performance speed stuff, I use air tool oil or ATF. I don't over do it. I put some in a syringe, pump it in, roll it around and that's about it. I know a few people that cap off their tanks and fill them with ATF, but I never found the need to do that. I've been using Powermaster 11/22 for 18 years now and since I've switched, I haven't had issues associated with all castor fuels. After a tank repair, I plug all vents and fill with all castor fuel and let it sit. When I get to the field, I flush it out and I've found that castor oil does a terrific job at keeping the metal internally protected.

**Cribbs74** Tue Apr 04, 2017 8:16 pm

Tanks that I have received from Ken are covered in oil inside and out. My guess is that is how he stores them.

While it may seem a tank is fine you never know until it is apart.

I see Ken posted before me....lol

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