Dated Sources of Information: Example – Fiberglass fuel tanks
I am now about to demonstrate my commitment to the risk management of today’s homebuilders, by “Touching the Third Rail” of homebuilding, I am going to say something that strongly disagrees with a man who since his passing has been elevated to infallible sainthood in homebuilding, Tony Bingelis. This will certainly generate hate mail, but that’s OK it just keeps the Christmas card list short.
Before people get up in arms, let me make several statements: Tony Bingelis was a real homebuilder, He made about 10 planes, he wrote a lot of useful articles, particularly in the era when many homebuilts were plans built, and the plans lacked a lot of finishing details. Critically, while his writing didn’t include phrases like “I might be wrong about this” no where did he claim to be infallible. That aspect of his legend came later, not from people who appreciated his books (like me) but from people who wanted to have an infallible saint to follow, who’s comments were often vague enough to seem to support their particular personal myth they wanted to believe.
Want an example? In his book on power plants, Bingelis’s advice on prop length is “Keep your prop as long as possible, as long as possible” Sounds like a witty clever idea, but doesn’t constitute any learning, testing or experience. It is just a catch phrase that countless people have used as ‘evidence’ that their belief that props turning over 2200 rpm are inefficient, and any prop smaller than 72″ makes no thrust. Let’s compare an actual data point, from a contemporary of Bingelis: Steve Wittman. get a look at this story: From The Past: With Steve Wittman 20 years ago today. I went flying with him, his prop was a Cessna 150 prop cut down to 62″, and when we were doing 195mph, it was turning 3,600 rpm. Anyone who understands anything about the life’s work of Wittman knows that if the plane would have been 1 mph faster with a 63″ prop, it would have had one. My point is that Bingelis published a lot of great detail design stuff, but when he didn’t have first hand experience, he resorted to vague hangar mythology statements like his one on props, that later generations would treat as some kind of religious body of wisdom, which is a bad concept, in a field where we are supposed to Learn Build and fly.
One of the first things people are going to say is that Bingelis’s book has a disclaimer in the introduction. It does, stating that none of the information is guaranteed to work. Actually this is one of the things I dislike about his writing. Go back and read it with a fresh set of eyes. Nearly every chapter has a subtitle disclaimer in it saying ‘this may not work for you, you should ask around. Read his comments on tank sealers: he will not come out and say “Don’t use it” he kind of says it but has a CYA, statement about how you should “ask around for yourself. ” If that was how one was to get information, why was the book written?
What is wrong with a Fiberglass tank in the fuselage? First , It is the least crash worthy of any tank material. Second, they put stuff in fuel today that was not even dreamed of when Bingelis’s book was written in 1986. The stuff can even be regional, and it might be in the tank of fuel you get on a cross country, after years without issue. Third, fuel tank sealers that worked great 15 years ago, don’t reliably work against the ethanol content in fuel today. Fourth, I have done a lot of high end composite work, and most home made fuel tanks including the one pictures are brittle pieces of crap, because the guy who laid them up had no training, and put about twice as much resin in the weave as desirable.
So what is the real lesson here? I had a guy tell me that he is building a Pietenpol, and his Piet buddies, told him that Bingelis’s books are “timeless” and that he didn’t need anything other than the plans. I pointed out to him that I own an original set of 1930’s flying and glider manuals, I love them, they worth more than $1,500, but I am not going to build a Pietenpol tank out of soldered tern plate, just because that is what is shown in the plans, and 1930 or 1986, it doesn’t matter, dated information is dated information. Books on aerodynamics structures and physics of flight don’t change, however, books on materials and process do, and only a foolish person would restrict himself to information 30 years old.
Today, there are lots of sources for proven information. There are modern day Steve Wittmans, and you should follow them, because their suggestions are based not on quaint sayings, but on tests you can study and understand.
Above, a fiberglass 12 gallon aux tank that flew for several years in the passenger compartment of my friends Caviler, a wooden low wing plane with a 60mph landing speed. The book is one of Bingelis’s three, immensely popular books. In this one, it details all the attributes of making this kind of tank, even on planes where the tank is in the fuselage, with narry a word about the kind of risk this is. The book was published 30 years ago and Bingels has been dead for 15 years. Perhaps if he was alive he might revise his recommendations in light of modern opinions about such tanks.
If you or your buddy have such a tank in your plane, I am not suggesting that it is “Un-airworthy” , but I am asking you as an intelligent human being to do some research and consider things. If your buddy says, “It’s been in there for years, I have seen plenty of them. besides, it is in Tony Bingelis’s book” Then he is just the kind of mythology spreader I am speaking of, and it is a waste of time to try to get him to think, he just wants an infallible source to cite as validation for him being too cheap or lazy to change it. Please read carefully: If you have seen my story:Steel tube fuselages, “Safe” planes and 250mph accidents, and you decide that you still are ok with this kind of tank, because you have given it open minded thought, I am ok with that, that is actual thinking, not validation.
Above, dull hatchet, half hearted swipe, and it is right through. Aluminum would do much better, and I doubt any human could put a dull axe through a rotationally molded plastic tank. There are countless plastic tanks, look at SummitRacing.com and search “Fuel Cell” Yes, they are cheaper than the materials in a fiberglass tank.
I have been an aircraft mechanic for 25 years. If I was doing an inspection on a 70 year old plane, but only used the AD’s written up to 1986, under the justification that it was a “classic” plane and the information about it couldn’t have gotten any better since 1986, the FAA would take away my License, period. If some one was hurt in the plane because it was not compliant with a post 1986 AD, then I would be looking at a complementary vacation at a federal gated community. Experimental aircraft don’t have AD’s but the logic of using up to date information is exactly the same.
Why this stuff matters to me: I have been burned over 40% of my body. I have written very plainly about the experience, and written articles like this: Pietenpol Fuel lines and Cabanes but quite frankly, I think most people don’t really care. Improving the fuel lines in a Pietenpol could be done for about $100 and four hours work, yet, years later, 75% of the planes still have hard fuel lines on them. Some people don’t care, others don’t like me personally and will not improve their plane, just because the suggestion came from me. I write this knowing that the great majority of people will not take the information seriously. I am OK with that, I don’t base my happiness on the actions of others.
To read about the contributions of Tony Bingelis to Homebuilding follow this EAA link:
14 Replies to “Dated Sources of Information: Example – Fiberglass fuel tanks”
I know what your thoughts are on gas tank locations (you wrote an article on this subject a few years ago), and I concur with them 100%. I don’t care what the plans say… I refuse to build a plane with the gas tank sitting in my lap. At a minimum, the tanks need to be in the wings and outboard of the fuselage. My personal preference is tip tanks, though I will admit that that preference is driven just as much by aesthetics as safety.
In Oct 2011 at the Copperstate Fly-in, I got what turned out to be a one-on-one briefing from Mick Myal on his then new book on the design and fabrication of tip tanks. Since I wanted to have the option of using mogas, and given that in Arizona at least, it is easier to find 80/87 avgas than it is to find alcohol-free mogas, the first question that I asked him after he finished his pitch was what kind of resin to use to fabricate the tanks with that would stand up to the attack of alcohol in mogas. He answered that I needed to use either vinyl ester or polyester resin. This statement is reiterated in his book, though the book does not state that the reason to use either of these resins is to combat mogas additives. Since that time, I have looked several places for confirmation or contradiction of this statement. The general consensus of the sources that I could understand (I freely admit that chemistry is not my strong suite) is that yes, polyester and vinyl ester resins are resistant to alcohol and other, similar solvents. But alcohol-resistant may or may not be the same as alcohol-proof. So, my plan is to make a test tank, fill it with high-test mogas, set it on the shelf, and keep an eye on it for a year or so while hoping for the best. My question for you is…Are you aware of anything that confirms or contradicts this?, or are you aware of a better alternative short of spending a year or two getting good enough with an English wheel and aluminum welding to attempt to make a matched pair of metal tanks?
In concept, Mick was correct, that ester resins have a better track record than epoxy on tolerating ethanol in fuel. For your test tank, consider filling it with E-85. There are a number of composite designs which use wet wings, and I would look into what current thinking is on ethanol tolerant sealers among Lancair builders and people in the Long EZ community. Aluminum tip tanks would look very nice however. -ww.
Both of those suggestions are excellent thoughts.
Had you not advised me on not using plain rubber fuel hoses in my plain, I would have because that is what came with the kit, not now, on your advice I’m running braided lines, not just because you said not too, but because you backed up your statement with reason and proof of why not to. not following the advice of experience is both dangerous and foolish. Dan-o
Okay. I have recently turned my attention to the construction of fuel tanks. I am scratch-building a CH750, just started the wings.
The tanks from Zenith are kind of pricey, so I was considering building them from scratch also. I don’t know how to make reliable welds and am disinclined to hire someone to do that…besides it probably would cost more than buying the tanks from Zenith.
In some of the stuff I read using solder (for aluminum) would work okay. Also, close pitched rivets also would work, with appropriate sealer. I wondered if rivet, solder, and sealer would be a reliable way to go.
Any comments and insights? And, if you have written about this could you point me to your articles?
Also, any comments and suggestions from the readership would be most appreciated.
The price on concrete here in Florida is running $110 per cubic yard, pricy, but it is reflecting the return of the building industry. I could either pay it, or I I could decide that I was going to build my hangar on a foundation of wet newspaper. Note that the actual cost difference isn’t between the concrete and newspaper, nor is that the newspaper would make the whole hangar worthless, the actual issue is that you might have the hangar fall down on someone who was standing in it.
Please let me know the name or source of any person who even remotely suggested that ‘soldering’ an aluminum tank for an airplane is acceptable. Given any lead on them, even an email address on a webgroup, I will have friends track down their identity, and I will make them the public whipping boy of my 2017 campaign against stupidity in homebuilding.
I have several square feet of very ugly skin graphs on me. If I made some shitty fuel tank, solely to save money, after experts warned me not to, and then I had a passenger, someone’s kid or wife in my plane get the same kind of burns and scars I have because the tank failed. I would write their family a very honest letter of apology, and then I would walk out in my backyard with a .357 and demonstrate that I was actually sorry for my stupidity. There are mistakes that are honest, and there are ones that proper atonement for starts with self elimination.
Just buy the tanks from Zenith.
Well, William, thanks for the insights and valuable technical information, and for the wonderful morality lesson.
I did read a number of articles, none of them suggested that the modern, post WWII method of fabricating fuel tanks included just soldering. I doubt that such an approach would be acceptable today.
But it seems that in pre-WWII, aircraft fuel tanks were sometimes fabricated using rivets, Such tanks were leaky, but accepted.
In Bingelis’s article “How About An Aluminum Fuel Tank?” he does mention the use of rivets with a pitch of 5/8″ along with the use of PR-1422 sealer. However, in another person’s article it was suggested that the use of an internal sealer should be regarded as a form of temporary patch used to correct a basic flaw in the fabrication of the flanged joint.
In any event, in all of the resources I have, and on the internet, I did not come across an article that showed in detail the use of solder alone, only in the context of repairing pinhole leaks in airconditioning units etc.
I won’t bore you with the whole list of references I have, but amongst them were:
FAA article on welding, chapter 5
There was also some information from Muggyweld as I recall. Interesting info on their products, and a variety of many other articles and videos on YouTube etc.
But generally rather meager offerings. That’s why I wanted to tap your possibly great knowledge on the subject.
I mentioned soldering, and should have included mention of silver soldering and brazing, my bad. The idea that soldering takes place below 875 degrees Fahrenheit, well below the melting point of aluminum, and brazing somewhat higher, and that aluminum abrubtly melts when it reaches it’s melting point of 1221 degrees F, seemed to offer a lower risk method for a homebuilder to make his own fuel tanks. According to Muggyweld, as I recall, the solder paste used would turn color at the melting point of the solder and safely below that of the aluminum.
But, I considered the combination of riveted joint and solder to provide structural support, with the solder to also provide a sealing/gasket effect (similar to the lead strip used on the riveted gas tanks of pre-WWII) and internal PR-1422 compound mentioned above. I hoped that you would have had some technical insights to share here. Oh well,..I suppose not all gurus should be expected to know it all, eh?
I will have an opoportunity to discuss bonding of joints for fuel tanks with an aerospace engineer next month. If anything of interest occurs I will let you know if you like. Perhaps we both can learn something.
Which brings up a question I have: You are the “Corvair Authority”, and I thought primarily an educator. Should I not have asked such a question of you? Did I seem one of the stupid ones? If so, I am so sorry.
Oh, and yes. I most probably would buy the tanks from Zenith. That would be the most prudent thing to do. I just wanted to, how shall I say, survey the field to come up with the best solution based on knowledge, price, time, and reliability. However, I am building from scratch more as an educational exercise, and do have a Champ and gliders to fly, so what the heck.
The first important division is the tank not being in the passenger compartment. A fiberglass tip tank is a very different story than one behind the instrument panel.
Second, 25 years ago I met the guy who invented the “Lumi-weld” process that appears to solder aluminum. His daughter went to Embry Riddle. The process can fix an old pot metal car door handle with a crack, but it is way too brittle for anything like a gas tank. The process works on alloying Zinc onto the repaired part. Has no place in aircraft. Neither does anything else that involves ‘soldering’ aluminum.
Plenty of planes, like 9,000 flying RV series aircraft have riveted fuel tanks (in the wings) that are sealed with PRC. This is how airliners work also. There are forms of sealer for riveted tanks that are fine with ethanol. People who make these tanks who pay attention to detail like scuffing and cleaning the aluminum, have success.
I know a lot about silver soldering. Look at any Corvair engine with our valve covers on it, and the copper vent lines are silver soldered onto the steel valve cover. Again, has no place in fuel tank construction, requires a lot of skill, if you can’t gas weld like a mad man, you will not be able to do this.
Engineers are great, my family is full of them from the finest schools in this nation, but I have found a number of ‘engineers’ who don’t hesitate to condemn fabrication concepts in homebuilding that have flown on 5,000 planes, and a moment later propose a solution that could only be performed by a Skunk works craftsman, in a space craft quality clean room, with DARPA level funding. Unless your guy say “I have built 20 tanks like this, run them with the same fuel for years, and made them in a shop like yours with your level of skill” than he might as well stop offering advice that could kill people.
Between the wars, OXY-Hydrogen was the way to weld aluminum fuel tanks. I have done work on DC-# tanks, and they were made that way. Having done it, I will gladly tell you that 90% people who write about it in books have no first hand experience, and you have to be good, and have very young eyes that pick up shade differences. It is 20 times harder than TIG welding.
Local people who claim to know how to TIG weld don’t have the thin metal experience to weld tanks, and above all else, they will pull bullshit like using the wrong rod (because it looks prettier than 4043) and you will not know you have a brittle tank until it bursts on a hard landing.
Just buy the tanks from Zenith.
Thanks for the feedback.
I didn’t mean to suggest that “my guy” the aerospace engineer gave me any advice at all. What I would expect of him is that he would listen to my question, think about it, apply what he knows to the issue, tell me, and then probably give me one of his “looks” as if to tell me to get lost. He is a tough guy, with very high integrity. One of our tow plane pilots, a glider instructor, and one of the good guys.
I did appreciate your comment about a person who may claim knowledge about TIG welding but may not know much about building tanks. This has been on my mind. In fact I do know a really great guy who does TIG, but I would not put him on the spot since I would grill him on his background. I would expect to see some kind of certification for his work.
In any event, as I said, I ask the question mostly as an educational matter, just trying to reduce my ignorance a bit.
I don’t like just throwing money at a problem, but yes, I will most probably “Just buy the tanks from Zenith”.
Again, thanks for the response,
And, end of discussion,
Thanks for bringing up questions a lot of people probably have, but don’t mention. It is a chance for a lot of people to learn. I am tense about the issues of fuel lines and tanks, because I can’t get more than 25% of the people to listen, even after I speak about what it cost me to learn this stuff.
There’s a quote out there somewhere that says “Just because it’s always been done that way, doesn’t mean it’s not an incredibly bad idea.” It’s accompanied by a picture of people running with the bulls in Pamplona. You don’t have to be a builder to understand your message. I see it every day at work… And I’m in marketing. BTW, when am I going to get a Christmas Card?? 😉
Snell recommends that you replace your motorcycle helmet every 5 years for several physical reasons as well as: “…experience indicates there will be a noticeable improvement in the protective characteristic of helmets over a five-year period due to advances in materials, designs, production methods and the standards. Thus, the recommendation for five-year helmet replacement is a judgment call stemming from a prudent safety philosophy.” This foundation has been testing composite structures since 1956 and have boiled down advances in materials to a 5 year interval. I just went and pulled my first dirt bike helmet out of the shop that is about the same age as when Bingelis published that book, it still looks fine, but I’m not about to put it on my son’s head and send him riding! So why ignore current testing and superior modern products? If you need to build a composite tank, build it. Just don’t build it using 30 year old information… Please.
Thanks for all you do,
The single seat aircraft design I decided to build features a fiberglass tank behind the seat and that was a NO-GO item for me. It lead to my efforts to merge that single seat design with a two seat design from the same designer which did feature fuel in the wings. I have the background in aeronautical engineering to take on such a task intelligently but most would either accept it or find a different design to build. I hate to say that it scares me to think what will happen if one of the aircraft of the type currently under construction ever has a crack-up. That tank is a death trap waiting to spring on the unknowing pilot in my own humble opinion. I follow WW when it comes to safe fuel system designs and hate to even bring the fuel lines into the cockpit to switch tanks, there just aren’t any good remote tank switching valves are out there.