Mail Sack, 7/13/14

Builders, Here is a sample of the mail:


On the story of: Zenith 601/650 Motor mounts, P/N 4201(A)

Zenith 601XL builder/flyer Phil Maxson writes:

“I think you may be a bit to hard on salespeople here.  You may not like them, but most businesses find them very useful, or they would get rid of the sales department altogether to save costs.  That doesn’t seem to be happening.

One of the jobs of a salesman is to understand the customers needs and supply that need.  What’s unethical about that?  Of course there are unethical sales people, and in a highly specialized industry like aviation, an ethical salesperson has to be very well informed.  I’ve found many a very helpful sales person in aviation businesses.”

Phil, My negative comments about salesmen are directed to raise the ‘buyer beware’ element in people new to homebuilding, and make them aware that journalists, in the role of consumer watchdogs, effectively do not exist in experimental aviation. Example: 10 years ago, “Daytona Cub” was a new cub marketed by people based at Spruce Creek, my airport where I was president of EAA-288. The man selling the kits knew nothing of building planes, but he talked a good line, that was often repeated verbatim by the press that he wined and dined. He publicly said many times “Our fuselages are made of .057 wall tubing which is 10% heavier but 40% stronger” Several obvious lies starting with they don’t make tubing in that wall thickness. Yet, I was the only person who ever pointed out that he was 100% used car salesman and 0% homebuilder. Look them up on line, plenty of people offer glowing testimonials, yet they were out of business in a few years. They often co-promoted a turbine called an ATP, which also got great reviews from journalists that had never seen it run. This engine investment later becomes Innodyn, collects investors and goes bankrupt. Today you can buy the URL “”for $25 and restart the whole scam all over again. I am quite sure that “journalists” would fall all over themselves to write good things about it as long as it was shiny and had a grey haired guy in a polo shirt to stand in front of it and spout ‘facts’ they could put to print. There is nothing wrong with knowledgeable people promoting good things, even if they are speaking of or selling things that they personally can not make with their own hands, just as long as the things they are saying happen to be true.

Some homebuilders believe that they are not likely to be targets of the rip off people because they have modest incomes and small budgets to spend. Let me correct this misunderstanding now.  Many rip off people know that if they came out with a $450,000 kit for the uber-wealthy, that if they didn’t deliver, the wealthy have lawyers on retainer, and will use them. Conversely they know lifting $4,500 from 100 times as many people requires more work, but most people with this kind of budget have never hired a lawyer in their life, and will walk away from that size  loss, and in most cases, will not even mention it to anyone else because they feel stupid for getting taken. If you think I am wrong about this, let me point out that Jim Bedee is still alive. Look up ‘Dream wings” and learn about this tactic. I was with Steve Rahm at the Dream wings presentation at SnF 1995, and Steve politely pointed out that the claimed stall speeds, g-loadings and Va speeds mathematically could not work, and he asked which one of the three numbers wasn’t right. Answer: Physics didn’t apply to their plane. The journalists present like the answer and called the design ‘ground breaking’. I guess that is the correct description for any plane that physics doesn’t apply to. This stuff is in high gear at Oshkosh. A few years ago, a new S-LSA  amphibious aircraft from Europe shows up. I was in the booth next to them. Plane arrives on trailer the day before the show; At the press conference I watch 20 journalists be told that it ‘flies great, flew in without problem, flight testing going great’. Gus Warren looks at it from 40 feet away and says, ‘That’s funny, it has no N-numbers”. Neither did it have an airworthiness cert. If you knew anything about aircraft building it was easy to see that it had no brake lines and many other details. But they did have shiny paint and salesmen, and this was all it took to fool journalists, who had never built a single aircraft part with their own hand that had ever flown. Offering these warnings is of little effect, because people rarely heed them, and the backlash is that I am often painted as a malcontent for doing so. The industry doesn’t like people that can’t ” go along to get along” and keep their mouth shut, and for the most part, neither do the majority of homebuilders who want to believe that physics defying airplanes exist simply because they want one.-ww.

International Aviator Tom Graziano writes:

“William, I’ve had more than one salesman try tell me their welding is done by an “FAA certified welder”. The look on their face when I informed them that no such animal exists was priceless  I’ve also had several pilots and A&Ps (who should know better) try to tell me about “FAA certified welders”….I politely spell it out for them – A W S

Builder Pete Chmura writes:

“Coffee Stout will change your life.”


On the story of: Randy Bush’s Pietenpol hits 500 hours.

Ken and Pat Caldwell write:


DAR/ builder Jon Ross writes:

“Dear William: I have never met Randy Bush but I have met a few like him as I travel around doing DAR work. Although I would rather be working on my own projects, I realized that I enjoy the DAR work because it gives me a chance to meet people like Randy. As you know, few people undertake airplane projects, and the chance of meeting special people such as you describe in Randy is greatly increased when traveling as a DAR. The special people are out there, and I try to stay in touch with them long after my job is done as a DAR because I am simply interested in where they want to go next…

Your philosophy with respect to creating things with your own hands is just as I have found it to be. I have a shop that is 45 minutes from where I live, but only 10 minutes from where I work. Naturally I spend a great deal of time in the evenings working in the shop. Sometimes, after a stressful day I have difficulty getting started. But I force myself on those days to change into my work clothes and get to it. It is never long before I am completely content working away at whatever the task at hand happens to be. Weekends are sometimes tough, because I am often called upon to assist friends with their airplanes, which I do with the full realization that I am really enjoying what I am doing. I am a loner, and a few years older than you (57 now) and I realize that for the most part I simply want to be left alone to work in my shop. When I travel around, I realize that there are people nearby who feel just as you and I do, in fact, many more exist than I once thought. I really do hope that these philosophical discussions will convince some of those sitting on the fence to get started on a life changing airplane project. Best, Jon Ross Northport, NY”

Zenith 650 builder Becky Shipman writes:

“William, Thank you for this thoughtful post.  I really identified with your last statement.  I have faced some very down times in my life, and difficult decisions.  Lately I think more about the times when I feel happy, and they have to do with certain types of experiences.  Flying does that for me – the combination of using knowledge and experience and physical feeling to feel competent.  I have felt that way winding up mountain roads on my bike at high speeds, and shaping metal on mills and lathes.  And there are times when I get into a groove when I’m building the plane, and feel competent and creative.  I occasionally feel that at work, but it’s more and more rare.  Sometimes I feel that when I get a concept across to one of my kids, like when I taught my son to drive stick.  The biggest thing I learned in some of my more extensive changes in life is that it is OK to take a calculated risk.  That’s what flying and homebuilding is to me.  I  think I will be happier when I feel I can move on from the breadwinner role to a life where I can make and teach and fly.  I turn 55 in a couple of months – burning my hand and having my back go out have given me the feeling that life is finite – and I want to have my experiences while I still can.  So for all that you feel you are flawed, we all are, and your example of pursuing your dream is as much a gift as your development of the Corvair airplane engine.  I’m guessing that might be part of what Grace sees in you, and ScoobE will always tolerate you as long as Grace does….Becky”

builder “Jacksno” writes:

“Excellent FC philosophy and model thereof.  Do  look forward to more than a story if possible,  Something more like at least a 5 part story in 100 hour (50 much better) increments that documents the history of decision making, results analysis, decision making, etc. This would be invaluable for us tychos. Go Fly Corvair.”


On the story of: Pietenpol Box Spar Construction, 6/27/13

Builder Allen Oliver writes:

“William: I can see where people perhaps may be misled concerning spar placement and loading by not examining all the variables.  On a moderately cambered airfoil straight and level in a low-speed environment, the center of pressure MIGHT be around the 40% chord.  If the aim is to even out the spar loads, placing one at 15% (-25%) and the other at 65% (+25%) could at first glance seem to do the job.  The pitfall is that the actual center of pressure location is highly variable, according to the airfoil shape.  More than that, IT MOVES.  As the angle of attack increases, the center of pressure moves forward.  This puts more loading on the forward spar. In addition, the lift loads are no longer perpendicular to the original bending axis. Just some extraneous thoughts for the mix. Regards, Allen Oliver”

Builder John Edwards writes:

“On the subject of spar loads, you do not need to be an engineer, nor have a degree in aeronautics to know the front spar carries most of the load. Just a little common sense.
Stick your hand out the window of your car and play airplane. You can feel most of the load is up near the front of your hand by your fingertips. It is that simple.”

Pietenpol builder Harold Bickford writes:

“William, Just for the exercise I calculated out the weight estimates of the various spar types (full span) for both Douglas Fir and Spruce. I used 34#/cu ft for DF, 28#/cu ft for spruce and 15# for a 4′x8″ sheet of 1/8″ birch ply. Actual weights of course can vary. The numbers below are for Spruce and Spruce/ply for the UK type In terms of weight the 3/4″ solid plank runs about 40lbs for front and rear sets. The routed 1″ beam would be about 2# lighter (calculated) while the UK type spar would be calculated at about 2# heavier. Clearly fabrication of the 3/4″ blank is easiest and it works. The cost differential was around $140 for materials. It is hard to beat what has been tried and proven though a properly engineered box spar or the extruded aluminum type is interesting to consider. -Harold”

Builder Doug Wright writes:

“William,It has been awhile since I have studied the subject, but one of the things I remember that has not been mentioned in the discussion about the design of Pietenpol spars is the distribution of pressure on the wing.  As I am sure you are aware, these pressures vary with angle of attack and are used in the calculations to determine the worst-case loadings on individual spars.  Why I mention this is because another variable that affects spar design is that these pressure distributions will be different from one airfoil to the next.  With both Mr. Pietenpol’s original design and the Riblett 612 airfoil being popular these days, a few years ago I ran the profiles for both through X-Foil and, as I recall, the pressure distributions were similar but not exactly the same.  Based on these software-derived numbers, I remember that after performing the calculations for the front spar worst-case loadings, there is a 4-5% difference depending on which airfoil is used.  Something like 75% of total load for one compared to 80% for the other.  Don’t ask me which was which or even if these numbers are accurate because I don’t have the calculations in front of me.  Would this make much difference in the load factor of a wing?  Not much, but I think it is important builders know there is a difference and if they choose to experiment with some other airfoil it may make a significant difference.

In looking at the cross sections of the traditional Piet spars and the PFA approved Jim Wills design there is not much difference in the moment of inertia of the solid portion of the spars where the lift struts and attach/cabane fittings connect.  Where a form factor must be applied when performing stress calculations on the rest of the spar, that is a different matter.  But, it looks to me that Mr. Wills moved the lift strut attach points outboard to reduce the length of the portion of the wing that is cantilevered.  This, of course, would reduce the bending moment on the wing at the lift strut attach points and would allow for the PFA approved 1200 Lb. gross weight with the same load factor as Mr. Pietenpol’s original, lower gross weight design.  Mr. Pietenpol’s empirically derived design was absolute genius but Mr. Wills must have recognized that people now days are a lot heavier and want to carry more fuel thus the airframe should be modified to accommodate those facts.  If someone builds Mr. Pietenpol’s original lift strut attach point design, they need to be cognizant of the fact that the load factor of the airplane is reduced at the heavy gross weights people are flying them. Doug Wright Stillwater, OK”


More mail on various topics:

Zenith builder in Haiti  Howard Horner writes:

“Hi William. Just wanted to drop a note to let you know I have entered the game, but must confess it is not exactly as you recommend. (1# bad.) I bought a1963 145CU IN core complete with turbo that I cannot use, for $150. (#2 bad) Traded it to a happy Corvair guy for a big basket of “cherry Picked” 110HP block parts and 95 heads with smaller quench zone. (Interested in the Avgas option w/ possible future turbo or Supercharger.) He promises to provide any incidentals we may have missed and I am anxiously waiting to receive your disassemble manual to learn what I did wrong and correct any deficiencies. The vindicating circumstance is that the turbo motor came in an antique red wagon that is selling on Ebay for $150-$300 plus shipping, so this transaction actually works in my building budget… basically zero! Be assured I am diligently studying your methods and as a result will no doubt benefit from a superior assembly, but equally important, I am 100% committed to supporting you guys that have invested so much by purchasing the Dan bearing, Falcon head work, and all the Gold parts.  Thanks, Howard”


Parting Shot, from Zenith 650 Builder Brian Manlove:

“William – I am finally back in my shop working on the 650.  I have read all of your posts and the one that prompted me to respond was the one about your brother.  I have a similar, but different, take on this – my *younger* brother Magnus.  In the last 25 years, we have not seen each other much, him with 3 kids, me with 3 kids, always living 1200 miles away from each other, and both of us always too busy with work. As you know, I was in a pretty bad motorcycle accident this past December 2.  I was in ICU for three weeks.  Magnus came to Austin to see me in the hospital – and because he was staying at my home he saw what I called “my workshop.”  I remember him coming to the hospital to see me every day for a week – but I don’t remember saying much other than “hello.”  I was in pretty bad shape and on a lot of pain meds.   A couple of days after he went home I went into an episode of A-fib.  The doctors found clogged arteries and scheduled me for a triple bypass operation, as soon as I “recovered” from my other significant injuries. When I got home, it took another month to recover enough to get the bypass operation. That happened on Feb 8 and it took another 2 months to recover completely from that. My workshop is a double garage that had been converted into a recording studio by the previous owner.  There was a wall that split the space into 2 rooms.  I had knocked out a span of wall wide enough to get a workbench in there for wing building – but with all of my tools, parts, shipping crates, and way too much accumulated junk, it was really not functional at all. When I got home from my heart surgery, Magnus called me and told me he was going to come down to Austin for a week in June to help me “fix the workshop.” Magnus came and spent a week.  What he did for me was absolutely fantastic.  He spent 16 hours a day working… and pushing me… we ripped out old walls, we re-wired, we built shelving, we built workbenches, he helped me decide what to toss and what to keep, and then the final touch – he surprised me with a beautiful epoxy paint job on the floor.  He gave me a gift that is beyond words. I now have an absolutely fantastic first-class workshop. All he wants in return is to see me finish my airplane. There is nothing like a brother. – Brian Manlove”

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