Access to fuel finger strainers

[jiott]

Do the fuel tank finger strainers need to be pulled out and inspected at 100 hour or annual inspections? If so, I am having trouble getting enough clearance with the #1 wing rib to allow the strainer and its 90 degree fitting to be unscrewed from the tank. The SS7 manual says to relieve the #1 rib capstrip enough to allow rotating the fitting, but I find that I will have to also cut away most of the rib web in this area to allow the fitting to back out far enough to remove. You guys must have also run into this issue?

Jim

Also, even if I could get clearance with the #1 rib to rotate the fitting all the way out, it would interfere with the fabric on the bottom of the wing. Looks to me like the fabric would have to be cut or an access plate made for this area in order to inspect the finger strainers. Maybe nobody does this; that would answer my question.

Jim

[Dave S]

Hi Jim,

Really good point.

During our build, I decided if it has threads - I should be able to un-screw it. :D

Here is what we did - 1) Cut enough relief off of the rib to allow the fitting to un-screw; 2) made an aluminum reinforcing plate for the fabric similar to what you do for the lift strut attach points on the wing to attach the fabric to; 3) made a small access plate which covers the hole and has a short screw on each end which goes into the reinforcing forcing plate the fabric is attached to.

One photo attached which shows the access hole when the wing was "in the suede" during the painting process. Not a real close up - but you can magnify the photo on the detail spot. Also don't have a photo of the cover plate but that isn't very complicated - just a little rectangular aluminum piece.

This permits both easy inspection and removing of the fitting and finger strainer. :)

Sincerely,

Dave S

[HighWing]

This is a most complicated area since the Series V. The V I am helping with had the same issue. The original builder - 1995 - put straight barbs in for finger strainer removal. I don't know where he thought the fuel line would run, but it simply would not work. He also snugged the fuel tank up to the #1 rib so there was minimal room between the rib web and tank side. Our solution was similar to Dave, but I would strongly recommend a polycarbonate doubler as Rans uses. You can make the cover plate of aluminum and it screws to the polycarbonate with quarter inch pan head sheet metal screws.

A tip to those still building, use the space between the tank flanges and the capstrips of ribs #s 1 and 2 to maximize the space between the tank's side and the web of rib 1 - snug the tank up to rib 2.

I understand a "street elbow" will work, but what we did is modify the elbow in a lathe essentially cutting off the threads, then taking a bushing and modifying it so we could silver solder its threads onto the elbow in a more snugged up location. A lot of trouble indeed, especially after everything is finished.

Yes the tank will tend to unport on a descent if the outlet port is positioned as it was for the first 10 years, but that is why we install low fuel indicator systems, but, for Skystar to design no provision for finger strainer inspection could in the long run be more problematic.

Lowell

[jiott]

Thanks for the suggestions. Still wondering if finger strainer inspection is a routine part of 100 hr/annual inspections? I am leery of regularly removing and reinserting threaded fittings in a fibreglass tank. It is so easy to damage the tank threads and get a good seal without overtorquing.

Jim

[HighWing]

Whether it is a good reason to remove it pariodically? With my first IV Every drop of fuel loaded at home was auto fuel and run through a Mr. Filter. Numerous cross countrys and lots of avgas. One time at an annual when I always removed the finger strainers, I found a chunk of rubber about the size of my pinkie fingernail hiding just below the finger strainer. I presume it came from a card lock facility where the hoses had been recently maintained. That in 900 hours. I plan on doing it again each annual, but I guess to each his own. I don't know anything about the high tech thread sealant guys are using now, but I use Fuel Lube as a sealant and it stays soft and didn't have seepage problems with the periodic removals. Consider ten times in ten years not a frequent event.

Lowell

[rogerh12]

Regarding the strainer in the tanks, I bought a model 2, which was about 10 years old. Fuel from one wing tank basically didn't flow (from a practical standpoint), the other was slow. I don't know what was plugging the strainer, but I could not remove the strainer, as it had been glassed in. So, yes, I think you should inspect it, or at least check your fuel flow from the wing tanks (though all filters and fitting would be best).
On mine, to clean the strainer I drained the tanks best I could and removed the filler cap. I blew a few quick burst of 10 PSI air though it to back flush the strainer, then siphoned out the remaining contaminated fuel. Added a bit of fuel, and repeated until I could not see any solids in the sucked out fuel.
I am sure it didn't remove 100% of the contamination, but it did restore full usable fuel flow and I didn’t have to repeat it again over the next year
Hope the helps
Roger

[Dave S]

Jim,

For the record, I do not routinely remove the finger strainers - I do flow test the fuel system at the annual condition inspection and compare flow rates with previous inspections. The finger strainers are designed to catch the big lumps and chunks that would plug the line and the finger strainers don't stop the smaller stuff that normally (if there actually is a "normally") clog up the finer filters. I can see where a person would think about this frequently if the tanks had an internal seal coating which might come loose and could clog the finger strainers - otherwise there should not be anything that will interfere with fuel flow - nuts, marbles and grasshopper heads will stop at the finger strainer but won't plug it.

There is a thread on gascolators ( http://www.teamkitfox.com/Forums/showthread.php?t=2598 ) which, although is not directly related to finger strainers - has some useful information considering that the fuel system has to be seen as a complete system where the weakest link becomes the problem - then trying to figure out what the weakest link is in a persons particular build. Again - that is why I do a flow test annually - it's an estimate of the total fuel delivery system up to the carburetor. My sense is that plugged finger strainers are not normally what bites one in the tochous - it is usually something else in the fuel system.

Again - I want to be able to get the finger strainer out if I need to - The need is not likely to occur very often.

Sincerely,

Dave S
KF7 Trigear
912ULS Warp

[chefwarthog]

Would it be right to do the inspection of the finger strainers with a inspection mini cam like the Dewalt instead of dismantle the all thing (the mini cam can reacord on SD card for datalog.)

Or it as to be take off for a eye inspection?

http://www.dewalt.com/tools/cordless-instruments-inspection-cameras-dct411s1.aspx

Have a good week end!

Eric

[rogerh12]

Dave;

Just to let you know, that you "do not routinely remove the finger strainers" has been duly noted and sent to the FAA for recording on your permanent record .

Ok, just kidding, but the stuff clogging my finger screens I think was slosh, or possibly release agent. I have also heard putting fuel tank cleaner, or fuel with alcohol in it can cause “stuff” to be released from fiber glass tanks.. Whatever it was, I didn’t expect to find it there.

I have a submersible camera probe, I got it at home depot or something like $130 bucks. I love it, it works great and I use it for aircraft inspections, and to find out how my renters plugged up the plumbing again. Everyone should have one, especially as cheap as have become.

Hope this helps

Roger

[jiott]

From what I've heard here, I think I will do whats necessary to allow unscrewing the strainer (relieving the #1 rib capstrip & web, installing the tank as far away from #1 rib as possible, installing an access window reinforcement in the fabric) but not cut the fabric thru the window until I need to. I like the backflush idea and the fuel flow test idea, so may not need to actually unscrew the strainer until later.

I don't think the mini-cam idea will work because there are at least two baffles in the fuel tank between the strainer and the filler cap on the other end of the tank.

I wish John McBean would chime in; I wonder what they do on the factory SLSA?

Jim

[Jfquebec]

what do you think about that fitting from Phenix industry....the pipe thread side are swivel....so with that you dont need to make an acces under the wing to remove the 90 elbow....

6182

[jiott]

I think that is a great idea, but I wonder if they make that swivel pipe thread with a hose barb on the other end instead of the 37 degree flare.

[Slyfox]

I think it's a good idea. what I do is fly one tank until it's as empty as I can get it. I have the low fuel warning. plus I have ball valves on each tank. when one tank is done. I of course switch to the other. back at the hangar I remove the fuel check drain. than I remove the strainer and check for junk, blow it out anyway and reinstall. than I fill that tank and go fly on that one to make sure all is well. than I do things all over for the other tank. works for me.

[Jfquebec]

good method Slyfox...do you have normal 90 degree elbow with acess under the wing...i try to find something to eleminate that acess....for phenix fitting they have a lot of stock...ll'e show you what i think that what we need...
6194
you can going with barb like that and put your favorite hose on...lol
6191

or...what i find very cool and easy to install is that compression fitting like that..
6192


with black braided hose....
6193

[Slyfox]

I have a model 4, the area with the rib I just cut it out so I can get in there. I didn't do it last year because I don't have a problem with it. so I can't remember if I close that wing and go for it. I think I do. I'll have to look at it. I have a fitting with rubber hose, blue stuff, hooked right to it. I take the hose off and put a socket on it and unscrew it.