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Installing finger strainers on Catalina fiberglass tank? Options?

18 posts in this topic

Posted

I'm redoing N157AB's fuel system end to end after a fuel flow test only showed 3.8GPH.   Likely causes included lots of 1/4" barb fittings that had < 1/8" orifices on them, and plenty of varnish and gunk in the elbows at the tank outlets.   

 

I'd like to add standard finger strainers to the tank, but the bungs on the Catalina fiberglass tank are only large enough to accommodate a 1/8" MIP fitting.  Nowhere near large enough in diameter to allow for 1/4", much less the 3/8" MIP that all the common finger strainers seem to be.  

 

Has anyone heard of a 1/8" NPT finger strainer?  Or had luck improvising one? 

 

 

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Posted (edited)

Leni posted an inline clear glass filter a while back, probably in technical posts - he uses it instead of the tank filter, I think.  He said he could clean it easier than the tank filters.

I have a copy, if you cant find it.

EDMO

I looked and didn't find it in technical posts, or General Hanger, or in my files - PM Leni about it.

ED

I found the reference and site listing from Leni in "NEW HEADER TANK FOR AVID"  it's the site for Summit racing, I think, and Akflyer's comments are also in the thread.

Ed

Edited by Ed In Missouri

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Posted

Leni uses SPECTRA  2369 from SUMMIT RACING, at local auto parts dealers.  It comes with adapters for 3 different sizes of fuel lines, slip-on fittings. About $10

EDMO

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Posted

Thanks guys- I've got a couple of those exact filters laying around.  After seeing the junk that had settled in the elbows, I'm somewhat set on having finger strainers of some sort to protect the intakes and the elbows.   

 

I found the other thread that discussed snipping the strainer off the 3/8 NPT Aircraft Spruce part, and soldering it to a standard 1/8" elbow.  I think this is the way I'm gonna go. 

 

I did find these: http://tinyurl.com/p3ncddr  (ebay)    It seems several riding lawnmowers use a 1/8" fuel tank bung, and the common part includes a finger screen and a screw valve.   I ordered one to check it out for flow rate and quality, but I doubt it will pass muster. 

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Posted (edited)

If you could get rid of the elbow and use a straight fitting, you might get by with the in-line filters, otherwise you are probably making the best choice by adding the finger screens. 

Let us know about the tractor fitting.

EDMO

Edited by Ed In Missouri

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Posted

If you're talking about the wing tanks on the catalina, I had the same concern, and drilled and tapped mine to a larger size- I'm thinking 3/8"  There's an aluminum plate buried in the fiberglass on my tanks (125AB) around the outlets,  which came as a relief.  I *carefully* drilled and tapped mine with NPT threads, which had NOT had any fuel yet..  I don't have a center tank.

 

Since you've fueled yours, I'd ventilate it for a while- maybe a LONG air hose running off a compressor at 5-10 PSI for a while..  before messing with anything like drilling/tapping/making sparks.

 

I *think* I sealed threads with permatex #2, build logs are alsewhere.  No leaks thus far.  I used the smallest  strainer I could get from AirCraft Spruce.  I also set up shutoffs for each of the tanks prior to the filters.  Had fuel running out of tanks too often in the MK IV when parked on uneven ground, or when folding wings.  I tested at 12 GPH on each tank, and run both open when flying.

 

I also sat in the plane, and installed fuel senders when I realized there was no way in heck I could ever see the fuel level on the left wing root through a "window".  I used the falcon capacitance senders and gauge.  I also modified the murle williams header tank with low-fuel warning, and installed it behind the third seat on the pilot side- I have a Hirth F30, which has a fuel return from the mikuni SBN carbs with built in pump and regulator (as well as an an-line facit, which helps prime and clear air), so needed a place to return fuel.  Warning light gives me ~10 minutes of time to panic..  as well as a quick reminder should I be so silly as to attempt a takeoff with both tanks off.  It also acts as a gascolator to catch water- which I thought usefull in a seaplane.

 

If you do set up dual shutoffs to tanks, I only close one valve to prevent cross-feed when parked.  To shut off both might create a pressure issue, depending on where you plumb in your vent line (mine has an on/off valve).

 

$.02

 

Jack

Austin TX

Catalina 125AB  Hirth F30  (27.5 hrs)

MK IV/Bandit  Jabiru 2200

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Posted

As expected, the tractor fuel pickup/valve (like these http://tinyurl.com/p3ncddr ) was crappy enough that I wouldn't want it anywhere near the plane's fuel system.  If it was just a finger strainer and 1/8" fitting, I would have considered working it over a little bit, but the needle valve seems barely adequate quality for lawn equipment.  

 

I've gone with soldering my own.  I'll post pictures and my process in a bit (I settled on hot air soldering after a few nasty attempts at other methods)

 

My Catalina has only the center tank, and the tank bungs are unreinforced and too small to drill out to anything larger than 1/8", so I'm definitely stuck with this approach.  

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Posted

When I picked up the Avid last month I was talking to John Larsen about this thread. It seems I also picked up somewhere around four new finger strainers for the plane in the spare parts I got with it. After asking him about where they came from he said they are common thing up there at the tractor supply stores. Something to check into I guess. I didn't see any part numbers on the ones I have but when I sort through it all I'll see what I can come up with. Maybe I'll find a part number in there somewhere, I believe one or two were still in a little bag.

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Posted

If you have a finger strainer plugged up, the only solution is to drain the tank.  Leni does not use them.  He uses a clear glass filter with replaceable inserts between the tank shut-off valve and the header.  Just shut off the hose, remove filter element and clean or replace it, and keep on flying.  Works for him?

EDMO

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Posted (edited)

 I sense some confusion on the purpose of finger strainers.  The purpose of finger strainers is to prevent a large object from plugging the fuel tank outlet port or getting into the fuel line of fuel valve.  They are a large mesh that will let small debris pass on to be caught by the fuel filter where you can see it or remove the filter to check without draining the tank.  Finger strainers are removed at annual inspection time to check for large debris.

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Edited by tcj

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Posted (edited)

Your are correct - and they work well in aluminum tanks - but there have been cases where the FS have clogged up by stuff from the fiberglass tanks.  Shit happens!  Guess if you made them twice as long, you would cut the chance of that by 50%?

EDMO

Edited by Ed In Missouri

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Posted

Reports of tank sealer pealing off in the fiberglass tanks is the reason I installed finger strainers.  A small flake of sealer has a good chance of covering the fuel port without a finger strainer.  I check them each year at annual inspection and have found no debris.  My tanks are 20 years old and came with the Kitfox factory sealer applied.  It is still tight and looks like new.  I'll keep the finger strainers in. 

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Posted

I think the plugging of the finger strainers was not so much from the tank sealer in big pieces, but from the fibers in the tank delaminating when you put moonshine in the tank,.  Those hairs plugged off a few finger strainers and bad things happened.  Guess what, you take the finger strainers out and those hairs just get lodged someplace else.  So far, I have not had this issue but we don't have moonshine in the gas up here either.  I am comfortable not using finger strainers where as others are not.

 

If you can, spend the money on a fuel flow meter.  This is the VERY first indicator that your having an inflight fuel restriction!  It has saved my ass a couple times when I noticed fuel flow getting lower and lower.  I was able to hit the electric back up pump and keep the engine running long enough to get to a suitable lake and set it down for a filter swap.  If I didn't have that fuel flow meter I would have flown along fat dumb and happy till the engine quit over some terrain that would have led to a heli flight and total loss of the plane.

 

:BC:

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Posted

That's a really good case for having a fuel flow meter that I hadn't thought about.

 

I also realized that if you are below a certain level of fuel in the tank you should be able to just fold the wing(s) back to access the finger strainer without losing fuel. I had to replace a sump on the left wing tank because it wasn't shutting off. I just folded the wing, puled it out and threw another in that I happened to have. Seems the one that was leaking just had a piece of Teflon tape in between the o-ring and valve. I pulled it out and put the valve back in my tool box as a backup. Seems the same could be done just as easily on the strainers since they are actually a little higher up in the tank.

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Posted (edited)

I have been looking for flow meters - I found a 1 1/4 UMA meter, 0-8 gph in Spruce, for about $180 new, but you have to buy the Floscan or another brand of sender, and I think these cost about as much - so, $360 plus tax/shipping is best I have found.

Kenneth, good point about swinging wings instead of draining tanks - Duh!  :lol:   I would say that a good safety way would be to install finger strainers, and then put the clear glass filters in the line just after the shutoff valve, like Leni has, then if no gas is in filter, your finger strainer is plugged up.  Again, others don't like a filter before the header tank?

EDMO

Edited by Ed In Missouri

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Posted

I fitted the homemade finger strainers, and am pretty happy with the results.  I added inspection covers directly under the fuel tank bungs so that they will be very easy to remove and inspect.  If there is residual fuel in the tanks because the lower part of the strainers are clogged, these inspection covers would make it very easy to catch the pour when the fittings are removed.   There's an inline fuel filter on each side before the fuel lines join together and go to the fuel pumps.  

 

Ditto the thoughts on fuel flow gauges.  When I'm able to watch both fuel flow and pressure, I feel like I have my finger right on the pulse of the fuel system.  Very comforting. 

 

I added an electric standby pump in parallel with the Mikuni pump, with external check valves after both pumps.  Given that there's a completely redundant fuel path, I was comfortable putting a fairly cheap gear-based gas/oil flow meter in line with the main pump.   I would *not* put such a meter in the only fuel path.  

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Posted

Thought I would add my fancy fuel diagram to illustrate my description.   Since I spent so much time on it, I want to show it to someone :)

 

IHBhTno.png

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Posted

If you are talking about just a normal fuel pressure gauge and sender, I found the gauge and sender at Van's aircraft was the cheapest I could find. The price for both together was below $100. I use it on my Starduster Too and it works great! It would be better if it had a light that got your attention when dropping below 3 or 4 PSI...I lost my mechanical fuel pump for I don't know how long before I realized that needle was low.

Anyway, here is the link for the gauge and the sender.

https://www.vansaircraft.com/cgi-bin/store.cgi?ident=1396329171-362-327&browse=ei&product=vans-fuelpres

Cowlove, nice diagram! Handy to have!

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