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Nathaniel
05-16-2009, 07:03 PM
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
05-16-2009, 07:09 PM
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
05-16-2009, 07:53 PM
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
05-16-2009, 08:12 PM
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
05-16-2009, 11:40 PM
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
05-17-2009, 07:43 AM
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
05-18-2009, 08:11 AM
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
05-18-2009, 10:17 AM
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
05-18-2009, 11:27 AM
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
05-18-2009, 12:22 PM
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.

Dorsal
05-19-2009, 03:48 AM
Steve,
Good point, the vent line is a perfect 1.5psi header tank pressure gage that is not affected by relative Gs. What do you use for a fuel sensor at the top of the vent line?

Slyfox
05-19-2009, 06:43 AM
I actually have the little tank with a float sensor. Mounts right on top of the header tank with hose connections to the vent just off the header and than the vent hose connects to the other side. The vent hose goes to the right tank. When the fuel empties in the line so does the little tank, thus the float sensor drops and makes contact. I than went to carquest and got a red light and mounted it to the panel.

Dave S
05-19-2009, 03:37 PM
Hi Nathaniel,

I'd like to get back to your original post regarding opinions about flushing new fuel tanks.

There are probably as many opinions about this, particularly as to how to do it, as there are builders - so please take my comments and opinions as only this builder's opinions/comments.

I believe there is enough data in the NTSB records to substantiate that experimental and certified aircraft suffer fuel contamination incidents resulting in engine stoppage in sufficient numbers that this subject should be considered seriously. Some of the incidents/accidents do not work out very well for either the plane or pilot. The incidents/accidents can be filed under two categories - either the contaminant(s) was/were not cleaned out of the fuel tank before the system was put into service; or, the contaminant(s) was/were introduced into a perfectly clean tank/system.

I think the answer about what to do is going to be more than evident if each of us thinks about the absolute most inconvenient time on the first flight to have an engine puke - but that is just me.

In my opinion, the builder needs to flush the tanks before assembling of the tank(s) into the wings; and, verify that the flush has been completely effective - verify - don't guess. It is way more difficult to flush after assembly.

My choice was to plug the tank fitting holes - introduce 5 gallons of water and detergent - close the fuel cap hole - then vigorously - even violently agitate the tank (a lot) in all positions including upside to dislodge as much junk as possible. Subsequent multiple clear water rinses to get rid of the soap and crud. If there is still crud - repeat till there is none.

How do you verify that the job is done? Use a coffee or paint filter to filter the water as you drain it from the fuel tank - I did the wash/rinse/repeat thing till three consecutive filter papers showed up with no crud.

Once the detergent is all rinsed out and it has been verified that no more crud remains (meaning three consecutive filter papers showing up with no crud) then the tank should be rinsed with isopropyl alcohol to remove the remaining water (since water is a contaminant also) - again - filtering the stuff when it is poured out because solvent may dislodge crud hat the detergent did not dissolve - good enough reason to do detergent AND solvent rinse. If any additional crud shows up - go back to the detergent and follow with rinses/solvent till there is no crud left.

Once the tank is spotless on the inside - allow it to air dry under controlled conditions so the isopropyl goes away and it is certain that no bugs or other debris are re-introduced into the tank. Then seal it up and store it away till it is ready for installation in the wing.

The upshot? I did the same with the header tank - the fuel lines and did a reverse fuel wash only of the filter to be installed in the fuel line...AND... when it came time to replace the filter - cut it apart to look for crud and found the filter was absolutely clean. There have been no fiberglass strands in the daily fuel samples/filter/header tank or anywhere else - ever.

Each one of us probably has a different opinion about this - I go back to comparing the effort to clean the tanks to "what if" on first or subsequent flights.

Sincerely,

Dave S
KF 7 Trigear
912ULS warp drive

Nathaniel
05-19-2009, 04:19 PM
Good post Dave. Since I know now that I have the "new" tanks from Kitfox, it is still a concern, but not as much. I plan on doing a pre-install flush, like you say. And replace all filters before the first flight, and during flight testing. By then, everything should be worked out of the system.

jdmcbean
05-20-2009, 08:00 AM
Nathaniel,

Think I responded directly to you.. but for reference here is a page from the manual.

Mark
05-20-2009, 08:04 AM
After flushing the tank, be sure to wipe the fuel inlet dry, dry, dry! It is very susceptible to rust almost immediately with any bit of moisture.

Nathaniel
05-20-2009, 08:05 AM
Straight from the source. That settles that!

Nathaniel
05-20-2009, 08:07 AM
After flushing the tank, be sure to wipe the fuel inlet dry, dry, dry! It is very susceptible to rust almost immediately with any bit of moisture.

Perhaps dry it and wipe it with a little WD40? Displaces moisture, that should help.