Eagler's Nest

General Category => Off Topics and General Interest => Topic started by: Murray Randall on December 22, 2014, 05:47:30 PM

Title: FUEL TANK
Post by: Murray Randall on December 22, 2014, 05:47:30 PM

 I'm getting my act together for wing bay fuel tanks.  My thinking is 1/4" Divinycell,  7781 weave glass cloth, Dow 411-350 Vinylester resin.   I would appreciate recommendations and advice on the subject.   Many thanks   Murray

Title: Re: FUEL TANK
Post by: mmorrison123 on December 22, 2014, 08:37:42 PM

That's how I made the tank for my Pietenpol and it was the worst building experience I had. My first attempt was to put 2 layers of cloth plus resin between 2 sheets of polyurethane and squeegy out the resin, then peel off one piece of plastic, lay the cloth on the foam, and remove the other piece of plastic. This did not leave enough resin in contact with the foam and when hard the fiberglass easily peeled off. Next I brushed resin on to the foam and tried to lay fiberglass cloth on to the wet foam. It went on crooked ant there was no way to reposition the wet, sticky cloth correctly. I had wet cloth strands on every part of my body as a result of trying to get the cloth on straight. Finally a friend gave me the solution. You cut your cloth pieces to size, position them on the foam, then roll them up and just off the edge of the foam piece. Now paint the resin on the foam and unroll the cloth into the correct position. Add more resin to saturate the cloth. Just that easy! I hung in and finished the tank, but I think I would opt for a riveted tank next time. 

Malcolm Morrison
wienerdogaero.com

Title: Re: FUEL TANK
Post by: Murray Randall on December 23, 2014, 04:42:05 AM

Jeeze     thanks   oh dear    I had doubts before but now I'm damn near terrified.    Trouble I see in the alumin tank is that the Pro Seal is no more fun than the resin.     I TIG welded a tank just once and the most beautiful of welds showed blue 100 LL stains every six inches or so on P testing.        Took hours of grinding, rewelding.     No matter which way I turn I get into personal skill set limits.   Have to face it, one of the stated purposes of experimental aircraft rules is built for education.

Title: Re: FUEL TANK
Post by: Sam Buchanan on December 23, 2014, 06:15:03 AM

I consider a riveted, prosealed tank to be the easiest route to a leak-free tank.

Title: Re: FUEL TANK
Post by: Murray Randall on December 23, 2014, 06:46:05 AM

That's exactly what Steve said

Title: Re: FUEL TANK
Post by: PropMan on December 23, 2014, 06:58:04 AM

Proseal isn't that bad,  it's the way I'm going.  Get everything set up before you start.

Title: Re: FUEL TANK
Post by: Murray Randall on December 23, 2014, 07:26:05 AM

.030?   

Title: Re: FUEL TANK
Post by: Sam Buchanan on December 23, 2014, 08:23:26 AM

Quote from: Murray Randall on December 23, 2014, 07:26:05 AM

.030?    

0.025" and a box of gloves. Have a coffee can with MEK in it to drop your clecoes in as you pull them. Lots more info on sealing tanks here:

my RV tanks (http://home.hiwaay.net/~sbuc/journal/tanks.html)

Title: Re: FUEL TANK
Post by: Murray Randall on December 23, 2014, 09:18:28 AM

What great batch of advice Sam. Many thanks. I hope the other Eagle builders that also have minimal tank building experience get to see that material!!!   

Title: Re: FUEL TANK
Post by: Alan Waters on December 23, 2014, 10:22:33 AM

I have had the thought of manufacturing an alum. pressure tested,TIG welded tank. I contacted Sam Buchanan to inquire about a pattern for his XL which he no longer has. If anyone is interested, create a poster board paper pattern for your individual aircraft and send it to me for an estimate. I would guess about $300.00 material and labor.
Contact me at alanelizabeth@gmail.com    Send your phone number or I'll send you mine. 


 About me. Certified welder employed by General Dynamics Corp. Have a shop at home. Have LE, LEXL and DE plans. Leaning toward the DE.

Regards to all, Alan Waters

Title: Re: FUEL TANK
Post by: stevejahr on December 23, 2014, 01:18:13 PM

Composites do not have to be hard... but like any material you need to understand their tradeoffs and techniques.

The strength comes from the fibers not the resin nor the foam.  The primary function of the foam is to serve as a form to hold the flexible composite in shape until it cures and hardens.  The secondary function of the foam is to provide separation between structural layers to improve strength with less composite material.

The normal function of the resin is merely to hold the fibers from sliding against each other and it does not take much to accomplish this.  And from a minimum weight perspective you want the least resin with the most fiber.  But for a fuel tank... here holes matter so you want extra resin compared to most applications.  The fabric has some spring to it so what I would recommend here is resin up the glass (or carbon...) cloth being a bit liberal with the resin.  You can do this right on the foam actually and an old credit card makes a decent squeegee for spreading resin.  Placement on the foam which should not be critical because you *did* cut the fabric over-size ;-)  And follow up with a 6 mil plastic sheet on top.  What you are doing is almost like vacuum bagging.  You work the resin under the plastic and the plastic will compress the fabric fibers and keep them from popping back allowing air into the composite.  Oh and do not wait until full cure to remove the plastic... remove it while the resin is still just a bit green and it will come off much easier.  When removing the plastic do not pull up, peel pulling across.

The technique I have seen most often involves making flat panels separately and then gluing them together with a glass reinforcement of the corners.  Note that the glass does not like to bend sharply so put a fillet in all corners... or the glass may make its own fillet with air entering the composite.

Adding the last panel... and having it sealed... tricky no matter what the material is.

Title: Re: FUEL TANK
Post by: Murray Randall on December 23, 2014, 01:28:55 PM

Attached is a sloppy sketch I drew up to see if anyone would quote a bladder.  I put the inlets on the front in the sketch by mistake.  They certainly should be on the inside!    $300 sounds like a good fair price, that I can't afford for two tanks or maybe I'm just stubborn and want to grunt thru it.  But email me at aeroads@comcast.net (aeroads@comcast.net) if you'd like. I can sharpen up the dimensions on the sketch it would help you. I only put one rib inboard and did not run a compression piece thru the fuel bays. So my dim's are different than the plans.  But that's a lot of work and expensive alum for $300 and I'm not talking cheaper.  That's fair as it is!!!

Title: Re: FUEL TANK
Post by: CHARLES DEBOER on December 23, 2014, 09:15:40 PM

Does anyone have a weight on the fuel tank as built for the LE or XL.  I have found a weight for the minimax tank (6 lbs. 9 oz.) that will fit into our wing.  Trying to find out if it will be a weight increase.

Title: Re: FUEL TANK
Post by: Murray Randall on December 24, 2014, 06:47:40 AM

If you made one tank of .025 6061 the tank, less seams caps flanges outlets would be on the order of 1.5 lbs by napkin calculation.  What mtl are those MiniMax tanks?   

Title: Re: FUEL TANK
Post by: CHARLES DEBOER on December 24, 2014, 08:46:43 AM

Quote from: CHARLES DEBOER on December 23, 2014, 09:15:40 PM

Does anyone have a weight on the fuel tank as built for the LE or XL.  I have found a weight for the minimax tank (6 lbs. 9 oz.) that will fit into our wing.  Trying to find out if it will be a weight increase.

I can only guess the material is a Poly.... .. something.  Whatever they use in one of those rotomolding machines.  It looks like a fogy yellowish white.  (think really bad yellow teeth)  About .125 thick.
ANYBODY KNOW WHAT THE LE XL FIBER GLASS TANK WEIGHS?

Title: Re: FUEL TANK
Post by: Murray Randall on December 24, 2014, 10:24:43 AM

I have stored on my computer from two sources that tanks weighed 3.5 lb. I didn't record the sources but I bet one is Steve K. He's got good records.  My approx. calcs say 583 sq in, the divin at 3#/cubic ft comes to .25 lb, the 811 cloth at 9 oz/yd comes to 1.5 lb.  So 1.75 lbs before resin fittings.  Sounds doable at 3.5 lb. Is in the same ball park as alum, but not lighter.

Title: Re: FUEL TANK
Post by: Bob S. on December 24, 2014, 01:03:32 PM

I BUILT a Cledgecell/Glass tank but it leaked so bad I went with a plastic one.... I'll get it down and give it a weigh later this week....

Title: Re: FUEL TANK
Post by: Murray Randall on December 25, 2014, 05:02:13 PM

Where can you buy a fuel filler neck and cap assy to inbed into a glass tank.  

Title: Re: FUEL TANK
Post by: Bob S. on December 25, 2014, 05:38:49 PM

As per the plans by Leonard, he uses a piece of 1-1/4" Drain pipe with a threaded homemade "cap"....

Title: Re: FUEL TANK
Post by: Steve on December 25, 2014, 05:40:56 PM

Quote from: Murray Randall on December 25, 2014, 05:02:13 PM

Where can you buy a fuel filler neck and cap assy to inbed into a glass tank.  

http://www.fueltankparts.com/fuel-tank-parts-accessories.html?gclid=Cj0KEQiAiO-kBRCNxtaJp4-En6sBEiQAnkvW30dcGAjhTh2AkX6hPyBUreDKGJnju-vZEiqrvLoD_6QaArut8P8HAQ

http://www.fueltankparts.com/aluminum-bolt-in-threaded-cap-assembly.html

Title: Re: FUEL TANK
Post by: Sam Buchanan on December 25, 2014, 05:46:16 PM

Quote from: Murray Randall on December 25, 2014, 05:02:13 PM

Where can you buy a fuel filler neck and cap assy to inbed into a glass tank.  

I used a PVC adapter and cap from Lowes. The adapter was epoxied to an aluminum flange.

Look at the last three photos on this page:

http://eaglexl-58.com/tank.htm (http://home.hiwaay.net/~sbuc/legaleagleXL/tank.htm)

Title: Re: FUEL TANK
Post by: Sam Buchanan on December 25, 2014, 05:47:07 PM

Quote from: Murray Randall on December 25, 2014, 05:02:13 PM

Where can you buy a fuel filler neck and cap assy to inbed into a glass tank.  

I used a PVC adapter and cap from Lowes. The adapter was epoxied to an aluminum flange.

Look at the last three photos on this page:

http://eaglexl-58.com/tank.htm (http://home.hiwaay.net/~sbuc/legaleagleXL/tank.htm)

(https://www.eaglersnest.com/forum/proxy.php?request=http%3A%2F%2Fhome.hiwaay.net%2F%7Esbuc%2FlegaleagleXL%2Ftank-19.jpg&hash=c84bdba3992c374dddf0fe3c0497f2d451bb1404)

Title: Re: FUEL TANK
Post by: docmatt on February 03, 2015, 08:31:46 PM

Has anyone built a steel tank?  I have been successful with welding up motorcycle tanks.  Rust does not seem to be a problem if it is kept full, or coated on the inside.  I would think .024 would be strong enough.  Weight may be a bit more than AL or fiberglass, which for me, is the biggest drawback.  I am being obsessive about weight.

Title: Re: FUEL TANK
Post by: scottiniowa on February 04, 2015, 07:46:10 AM

Quote from: docmatt on February 03, 2015, 08:31:46 PM

Has anyone built a steel tank?  I have been successful with welding up motorcycle tanks.  Rust does not seem to be a problem if it is kept full, or coated on the inside.  I would think .024 would be strong enough.  Weight may be a bit more than AL or fiberglass, which for me, is the biggest drawback.  I am being obsessive about weight.

  Doc,
   a few observations:   With steel, as you say, weight will be your number 1-worry, but this is easily calculated by the provided weights of sq ft of material. So you will know before you start.  
2nd worry- always wondering if you get to hear the silence of NO fan, when flying due to foreign material going down the line. Certainly should be able to screen it with fuel filter, but…. always the worry.

But anyone with the ability to build with steel has the capability to do the same with alum. (and get a clean-light weight tank)   One simple but extremely effective way for fuel tank building the alum. way, is to use the TIN MAN’s methods (Kent White) google him gas alum welding- Very simple to learn, and extremely strong when your done.  Of course you got T I G as an option, but that is a whole different can of worms.

Best of success.  I know I didn’t give any clear answers but maybe some food for thought.

Scott

Title: Re: FUEL TANK
Post by: docmatt on February 04, 2015, 08:57:58 AM

Thanks for all of your thoughtful answers Scott,
I do not have TIG, but I could sure use an excuse to get it;).  I actually spent the better part of three days at Oshkosh one year at the Tin Man's booth, learning everything I could from him.  I got some of his AL flux and 1100 welding wire.  I was never able to make anything but a barely acceptable weld when I got home.  Short seams pretty good, but anything longer would end up with a hole or blob.  On the other hand, when I weld thin steel, it looks like a machine did it and it holds pressure with no problem.  I wonder how thin one could safely go with steel on a fuel tank?  You are right about the flakes left from welding inside the tank though.  A riveted and sealed AL tank may be the way for me to go.  Maybe I'll buy some sealer and try making a reserve tank for a motorcycle and see how it works out.

Title: Re: FUEL TANK
Post by: Murray Randall on February 04, 2015, 11:56:11 AM

I TIG welded one aviation tank and the most beautiful of welds would show a blue stain when I put in some 100 LL. Very discouraging!   TIG welding up a neighbors heavy wall farm irrigation pipes is a snap.  .020 alum is something else.   So this time its fiber glass and vinyl ester resin.   And man that is tedious.  Aviation fuel tanks are a bitch!!!    Murray

Title: Re: FUEL TANK
Post by: Dan_ on February 04, 2015, 06:00:00 PM

Quote from: Murray Randall on February 04, 2015, 11:56:11 AM

 .020 alum is something else.     Aviation fuel tanks are a bitch!!!    Murray

Try .050 3003 or 5052 on your next tig welded aluminum tank...

Title: Re: FUEL TANK
Post by: scottiniowa on February 05, 2015, 02:47:32 AM

Quote from: Dan_ on February 04, 2015, 06:00:00 PM

Quote from: Murray Randall on February 04, 2015, 11:56:11 AM

.020 alum is something else.     Aviation fuel tanks are a bitch!!!    Murray

Try .050 3003 or 5052 on your next tig welded aluminum tank...

Dan is spot on, that would be the standard recommendation for fuel tank building…  .020 alum NOT so… And though it has not been said,  there are somethings you just don’t want to try with certainly alum. types.  and .020 tanks would be one of them of any type.

Bungs and fill holes are all readily available from race supply houses,  side fittings for sight glass for a no-weld way is available from Rans Aircraft. 

Best of success.

Title: Re: FUEL TANK
Post by: Tom H on February 06, 2015, 06:10:43 AM

I've built several tanks for LEU Treehugger and DE Stubby.

The first LEU tank I tried to make was made by shaping a stack of styrofoam insulation boards, sealing w/ plastic film and tape, and covering with fiberglass and vinylester resin.  Unfortunately, the resin vapors seeped through the plastic and started melting the core.

Next I used urethane foam as a core, spread a thin film of RTV to be a release agent, then covered w/ FG and VE.  Cut a hole in the top and removed the foam.  It turned out fine, and we used it for a while, but then found gel in our carbs.  We think it was from the VE resin.  VE is supposed to be good for auto fuel, but maybe ours was out-of-date or the RTV screwed it up.  This tank weighed 5 lb 1.6 oz.

It was replaced with an alum tank that I made from 0.040 3003 sheet, tig welded.  I used 0.040 because I made some samples with 0.025 alum and found I had too many "errors".  3003 was used because it bends well, does not tend to crack and is often used in tank construction.  I did weight it, but can't find the numbers.  I do remember being surprised that it weighed nearly the same as the FG/VE tank. 

I made two other tanks for the DE.  I've attached two pics, one showing the internals, one showing it in the wing.  All the alum tanks were tested by pressurizing with 1.5 psig air, blocking off the air supply, checking w/ soap solution, and monitoring the held pressure on a pressure gauge.  After several repairs of pin holes, they eventually held pressure for over 20 hours.  No leaks in the airplane, so far.