Tailwind builder and host of CC#17 and #25 Arnold Holmes wrote:
William is exactly correct on this. Both spars in a two spar wing DO NOT CARRY THE SAME LOADS! I do not have my copy of “Design of Light Aircraft” by Richard Hiscocks with me at the house but I know that author has written almost an entire chapter on exactly this issue. As a side note, think of a cantilevered wing (one with no struts) if both spars carried the same load then you would expect them to have similar construction and sizing. You can clearly see that they do not. The rear spar is normally designed to pick up the torsional loading of the wing and react it inside the fuselage. It also provides a place to hang flaps and ailerons. The torsional load is much smaller than the bending load of the main beam. Do not follow the engineering example of this spar design. I will follow up after I get to the shop and research the issue. Arnold Holmes
Builder Steve McDaniel wrote:
You are so right in this, it screams ! I am a licensed structural engineer of 40 years in private practice, and wince when folks work outside of their knowledge base, then publish it like they know what they are doing. I used to wonder why us design engineers are not allowed by Codes to use the full strength of materials, usually two-thirds or less. Call them load factors, safety factors, or strength reduction factors – I’m glad we have them !!
William, I sent Spenser $100 as I know he will use it wisely. This truly is a great group of people banging these engines together. I also am thinking seriously of building the Panther engine, as I love the billet crank, and 120 HP would provide some maneuvering power and reserve. I am going ahead with the Fokker D.XXI as my choice, and have found some help in beefing up the airframe VERY carefully to allow an LSA cruise of about 125-135 MPH. I’d start from scratch, but an engineer I am not, and your three “friends” would be waiting for me if I bleeped up the math…..:-) So I’ll start with the Loehle P-40. I am much more comfortable with their wood airframe, but I will get assistance to make the structure as strong as possible. The theory turned out to be easier than I thought – now I must become a craftsman….. I am looking forward to CC#28 in Tejas next year.
Waiex builder Greg Crouchley wrote:
Remember The Titans’ movie…. “Attitude reflect leadership”. Thank you to both you and Grace for leadership in humanity.
I wonder why aviation oils like shell don’t have zddp? Aren’t most flat tappet engines? For what it’s worth I bought a 1966 Corvair with a 140 engine after buying your conversion manual. Anecdotally I after switching from shell rotella to amsoil amo 10w40 my lifters don’t clatter at start up. Oil pressure down 5 psi at idle , no temp change.
Jim, Lycomings have steel cams and mushroom base lifters with different metallurgy. I also have a ’66 Corvair with a 140 engine. Lifter clatter on start up in older car engines is often a lifter without a full 3/4 turn of preload. It gets within operational range as the engine warms. In other cases slightly sticking lifters can be shut up with fresh thin oil. Neither of these happen in fully rebuilt engines. The lower idle pressure is expected, the thin synthetic can get around the pressure regulator piston a lot easier when the oil is cool.-ww
builder William Emidy wrote:
William I couldn’t agree more. When I was just a new A&P I worked for a guy in Utah whose favorite expression was “oil is cheaper than engines”. This was first told to me when I had asked why he had us change the oil in the company owned aircraft. That among lots of other bits of knowledge passed along to me by people who have “been there,done that,bought the t-shirt”. When someone you know has the knowledge,and is willing to pass it along. LISTEN
Merlin on floats builder/flyer Jeff Moores wrote:
Hi William, I’ve been running Shell Rotella T 15W-40 oil plus ZDDP from Clark’s as per your recommendations since the first start of my engine. Changed after the first hour break in run, then after 10 hrs., and after 5 flight hours as per the Flight Ops. Manual. Now it gets changed every 20 hrs. This oil is available here out in the sticks from several auto parts stores. I by mine at NAPA who also stock the filters. Why anyone would want to use anything else is beyond me. The price is certainly not an issue.-Jeff Moores Corvair/Merlin 100+ hrs
Pietenpol builder Mark Chouinard wrote:
I too would like to say thanks in advance for CC#28. Like Vic, I am looking forward to completing my engine at this event. As for wearing shorts in Texas in March… it is also quite possible to need a heavy coat that time of year (re: CC#22… brrr).
Also, thanks for the oil article. As you know, oil is one of the biggest hot button debates on motorsport web sites (motorcycling, trucks, you name it), and most of the commentary, while mildly amusing, is a complete waste of time. I’ve never used Rotella T products, but will make it my oil of choice in my Corvair based upon your research and reporting. Thanks again for helping us to properly build and maintain these awesome little engines.
As for the points on people’s character, another good read. I’ll be sharing that one with Tyler (my 9yo son). He already demonstrates pretty good character and common sense, but it helps to hear these things from others as well.
Zenith 750 builder Blaine Schwartz wrote:
William, Thanks for your guidance regarding oil. While I still have the break-in oil in the engine, I will soon be changing it. As you know, I built my engine at CC#22 and it ran flawlessly. I keep a picture of the completed engine (with yellow sparkplug wire, braided stainless hoses and Niagra cooler) on my phone and show it off when I get in the company of any motorhead!
Zenith 650 builder Becky Shipman wrote:
Many hours of time have been spent on oil discussion, particularly in motorcycle forums. Many motorcycles have both a gearbox and a wet clutch bathed in the engine oil, so it is doing double duty. My local A&P who does some work on Rotax engines, worries about lead buildup in the oil and in the gearbox (Rotax has a gear reducer). More frequent oil changes w/ 100LL than with high octane mogas. The manufacturer recommends not using 100LL with the Rotax, but if you must change the oil and clean the gearbox more often. Yet another reason I chose the Corvair over the Rotax – most airports I fly to have only 100LL available. Oil change is easy and cheap, there is a need to flush lead out of the system, so I really don’t see a downside to using an oil that is highly tolerant to lead and changing it often. I use a different oil in my Yamaha Virago (wet clutch and gearbox – Amsoil 20-50) and my BMW R1100RTP (Mobil 1 40 – dry clutch and separate gearbox) and different oil in each of my cars. The BMW oil is on the recommendation of a former Vietnam A&P who has been restoring BMW’s for 30 years. Sometimes I go with the manufacturer’s recommendation. Seems the manufacturer, based on data, is recommending Rotella. No problem for me. Jed’s a Millionaire – kind of dates you, eh?
builder ‘Jacksno’ wrote:
“Your engine is your personal masterpiece. You should be tempted to pull the cowl off and just marvel at it for no reason. You should drag passers-by at the airport into your hangar and proudly say “LOOK! I built That!” With an arm gesture that magicians use as they say “TAA-DAA!”” – I love ‘Art’. BTW, this article contains ‘high WW prose’ throughout. AND cracks me up! Dead (read Living) Serious + Humor = FlyCorvair.
I wrote the oil story at 4am after drinking too much coffee. They turn out more entertaining at that hour.-ww
Builder Bob Lee wrote:
William, You are right on about not using synthetic oils in Corvair engines. Synthetic oils were developed for jet aircraft engines so naturally everyone would think that it is good for a piston engine too, but that’s not the case. One of the characteristics that makes synthetic oil so good for jet engines is that it rejects heat. It does not pick up heat as well as regular oil does. This is a great thing for jet engines, but not for a Corvair. The Corvair is an air/oil cooled engine. If you change to synthetic oil in your Corvair and see a reduction in oil temperature, that is because the heat is staying in the engine. You have lower oil temp and higher internal engine temps. Synthetic oil should never be used in Corvair engines.
Bob, My preference is for Rotella and frequent changes and good inspections. For fans of synthetic, it is important that they at least choose one that is compatible with 100LL. I have heard some of the things you have said relating specifically with air-cooled engines and synthetic oil, but I have flown both, and didn’t have a major issue with either. Outside of Corvair flight engines, I have had some pretty good experience with synthetic lubricants in gear boxes and modern engines like the LS-6 in Graces’s Caddy. BTW, both Grace and I learned to fly a long time ago at a grass strip in central florida named Bob Lee Airport. It is still there. -ww
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