Flush new fuel tanks?

[Nathaniel]

Just a question about the composite tanks. Read about fibers clogging up fuel filters and carbs. Anyone have an opinion on pre-flushing the tanks either before or after install? Get the loose crap out?

[SkyPirate]

my experience with the composite and fiber tanks ..every 10 hours or less I had to replace the filters,.this was after about 4 dead stick landings due to lack of fuel flow,..I figured out it was the fibers,...so pre flushing it I don't think would eliminate the problem totally,.until I coated the tank internally ,..then I stopped getting fibers,..I cut every filter after replacing it and let it dry out to inspect for fibers,..before the coating ,.I can't say I got less with every new filter,..they are hard to see until you dry out the filter,..

I just want to add ,..these tanks were not on a kitfox aircraft,..I know John has addressed this issue concerning the kitfox tanks.

Chase

[Nathaniel]

Okey dokey. Missed that in the other posts. So, just to be clear, the tanks supplied by Kitfox are, for lack of a better word, fixed? Thanks!

[SkyPirate]

Nathaniel ,.. I know the issue was addressed from reading previous posts concerning the tanks,..you need to contact John concerning your tanks to see if they are pre or post the tank issues

Chase

[DesertFox4]

Nathaniel, Unless John McBean tells us otherwise I would assume that even the new tanks may have some friable or loose fibers in the tank just as a part of the building process. These are very high quality items and professionally made but I would still error on the side of caution and rinse the tanks before installing in the wings. There after during the initial flight testing, change the fuel filters frequently to make sure you are keeping full fuel flow to the engine. I'm saying change the filters after ground taxi tests and gournd engine full throttle run ups but most importantly right before your very first flight. Then change them again after 5-10 hours of flight testing. Each time take apart the used filters, let them dry as Skypirate indicated and then the glass fibers will be visible. You will not see them even in a see-through fuel filter as they become invisible when wetted by the fuel. If fibers are found stay vigilant for them until you no longer find them in the fuel filters. They should stop showing up after a few tanks of fuel. I still take apart my fuel filters even now after 700 hours but I haven't found glass fibers after I had approximately 20 hours on the plane and they were reducing in quantity rapidly before that. I will state that before I installed my fuel tanks in the wings I DID NOT pre-rinse them. That might have reduced the glass fibers but I'd never assume the rinsing is going to get them all.

P.S. - There are also finger strainers in each wing tank that should be checked periodically for obstructions. I think the glass fibers will pass through these strainers but the fuel filters will stop them from reaching the carbs. I use Napa see through in-line filters in both of the fuel lines between the fuel tanks and the header tank. They are both positioned so I can see them during flight.

[Nathaniel]

Email from Randy -

All fuel tanks produced for the last several years are made with vinylester resin and are ethanol-proof. John McBean has tested a tank for 2 year with straight ethanol in it, no problem. You're good to go.

You may have heard about folks "sloshing" their tanks back in the day. You do NOT want to slosh your tanks, there's about a 75% chance the slosh will later come loose and clog the system, not good.

[RandyL]

Nathaniel, ditto DesertFox4's comments. You have the latest tanks... rinse them once before you mount them in the wing while it's easy, check them carefully before your first flight, and stay on top of them during your eary hours.

[Slyfox]

One of my tanks was replaced when I did the wings. The left one, had a 6 gal. I put the new tank on, did nothing to it. I did get debris in the filter. What I did was this. I did many checks of the drain. Found fibers. Installed filters just off the tank, changed those every 50hrs. Every 50hrs, I blew reverse into the tank when changing the little filters. To make sure the screen stayed open. I now have over 900hrs on this tank. I still get junk through it. I just watch the filters and change them often. Every oil change. Never had a problem. I only have one filter now, and that's just after the fuel cut off. I can reach under the panel and flick it with my hand and check real quick if it has junk in it. When it gets to much I change it. Always at oil change time.

I will say, get one of those low fuel sensors, saved my butt many times from a tank that all of the sudden goes dry, if you know what I mean, and if one tank desides to slow up and need a back flush of the finger strainer.

[Dorsal]

OK so here is an idea I have been kicking around that reads fairly directly on this thread. Has anyone put a pressure sensor in the header tank? If my math is correct it should read ~1.5 lbs if there is fuel in the tanks and the filters are not clogged. If the supply to the header tank is starved for any reason (empty tank or restriction in the flow) the pressure will drop to zero or less depending on the fuel pump. This would of course be true for normal flight conditions as it would be effected by relative Gs.
Comments?

[Slyfox]

I tell ya, that is not really needed. If you have the fuel sensor in the vent line. As soon as the flow is cut off the fuel goes out of the vent line and than the sensor picks this up and a red light goes off. Get the fuel flowing again and the fuel goes into the vent line, thus filling the sensor and turning off the light. Good system. Recommend it for everybody. I've had mine go on many times. Mostly because I'm in lala land flying along and forget about the fuel. All of a sudden on goes the light. Thing is, sometimes if I'm low on the old tank, pickup at the back of the tank, and on final and only half tank, the flow is cut off, thus the light will come on. No big deal, I switch the left one on. But, it happens. Why don't I have both on. I guess fuel management, first, I want to make sure I get rid of old gas first, ya right, I fly every day. Second, the RV can only run on one tank at a time, so keeping up on fuel management is a good idea. I'm trying to keep things as close to the same on each airplane as possible. things like airspeed, knots in the RV, mph in the kitty. Just makes sense to me.