Pietenpol Products, Motor mounts, Gear and Instalation Components.
November 8, 2012 4 Comments
Below is a series of photos explaining some of the parts we make for Corvair powered Pietenpols. The photos span more than 15 years. I am not a new arrival to the Pietenpol fan club. I can make a very good case that Bernard Pietenpol is the patron saint of homebuilding, the original man who championed the cause of affordable flying for the working class. I have done a lot of work with Pietenpols over the years from building and flying to the weight and balance project, to making several pilgrimages to Cherry Grove. If experimental aviation is supposed to develop your craftsmanship, practicality and self-reliance, following the life work of Bernard Pietenpol has to be the best compass course ever.
My work is Corvair powered Pietenpols has developed from first hand experience over a long time. There are many people who have flown or built a Piet or even two. They probably like the way theirs was set up, people tend to like the plane they know. Very few builders can say they made as many changes and comparatively tested them, had many different pilots fly the same aircraft and offer independent evaluations. Most people have seen photos of Bernard’s personal aircraft: I have performed weigh and balance work on them, my wife has flown the last original, and we later rebuilt the engine on it. I have gone on to make parts that have flown on dozens of Piets. I have even personally studied the results of Piet accidents to learn design detail information. My only allegiance was to what tested better. I am not suggesting that I am some kind of special expert here, I am just saying that I have invested a lot of time and work, it was a labor of love, and I am confident in the data presented. If builders can use the information, good. If it treads on anyone’s differing perspective, they are free to ignore it.
Above, our master welder and side kick Vern takes Bob “Earlybuilder” Dewinter’s motor mount out of our Piet Jig. Bob is picking this up at CC#24 after we have it powdercoated. This is what I call a high thrust line mount, as the thrust line is 3″ higher that a stock BHP mount. Later photos will show the difference on the plane. This mount has a overalll length from the firewall to the prop flange of 32″. This has plenty of room behind the engine, but most important, it is the beneficiary of all the weight and balance data we collected by measuring 30 different Piets on the same electronic scales. Piets have a chronic aft CG problem caused by heavier pilots, light engines and no planning. This mount is part of a very well-developed plan for Corvair Piet builders to follow.
Above is the same mount bolted on a Corvair with our standard intake an MA3 carb and a rear alternator. All of our components are integrated to work together on this.
The above photo shows how our Gold oil pan or our welded oil pan clear the diagonal brace at the front of the mount. Putting it in this position makes the mount very rigid, and gives plenty of room for an uncluttered carb and air filter. The mount is very well-built and 100% TIG welded out of US made 4130 tubing. Dan Weseman stopped by, checked it out in the jig and pronounced that he would fly a snap roll with it. The mount weighs slightly over 5 pounds. It could have been built to weigh 3.5 pounds, and been fine for the way most people fly, but in my judgement, this is the wrong place to look for a 26 ounce weight savings on a plane.
Above, My Pietenpol at the last hours of Sun n Fun 1996. From L to R, Gus Warren, Steve Upson and yours truly. The photo was taken by Mary Jones, the EAA’s editor. We are all smiles, but in reality we were nursing brutal hangovers from drinking “Muzzeloader” (moonshine) at the ultralight party the night before. Note the test cowl that functions like the air box on the test stand. At this point, the plane still had a stock thrust line and stock short landing gear legs. If you look at the cowl there is a 6″ wide filler stripe of aluminum in it. That is due to the motor mount being extended 6″ in one shot to test different CG locations. It flew much better with the CG forward. There are far too many Piets flying at the aft end of the CG range. It only feels acceptable to a pilot who has not flown one with the CG where Bernard intended it to be.
Above, Grace and I stand with my Pietenpol in 2000, the day before Corvair College#1. This is the same airframe after a large re-work in 1998-99. Get a good look at the height difference in this photo and the one before. This has two factors, first the thrust line is 3″ higher on a new mount and the landing gear is completely re-made from scratch and is 6″ taller. Note that it has die springs. Get a good look at the camber angle of the tires with the plane unloaded. This is by design, it gave the plane excellent ground handling. The plane had a large muffler under the belly.
Above, side view of the plane taken the same day at Spruce Creek Fly-in, our airport from 1991-2003. My Piet had a short fuselage. No one should build a short fuse plane today, there is no reason to, it is a complete myth that they have a better CG situation. Notice the new deck angle on the plane. With more angle of attack the plane could be three point landed at 10 mph slower. Look at the axle location of the gear in relation to the LE of the wing. This gear was set to be slightly ahead of the wing in level flight. The brakes on the plane were 6×6 Cleveland hydraulic drums off a Tripacer. This combination of slow landing speed, forward gear and good brakes meant that the plane could actually make landings in 200 feet. Maybe you don’t plan on flying like that, but every year at least one builder who blindly built his landing gear 7″ behind the LE in accordance with the 1933 plans, puts his aircraft on its back. Planes in ’33 didn’t have brakes and always landed at “Airfields” where you landed directly into the wind. Cross winds and brakes mean it is best to have the gear on your plane where BHP migrated his to in the 1960s, near the leading edge of the wing.
Above, BHP’s last original, Corvair powered of course. This plane has 800 hours on it today, it lives at Brodhead and belongs to our friend Bill Knight. We did the weight and Ballance on this plane two years ago and overhauled the engine last year. On the outside it looks just like BHP made it, but inside it has a nitrided crank, Arp bolts forged pistons and one of our Black prop hubs and hybrid studs. Look closely and understand that BHP kept the thrust line low because he had the stock automotive blower fan on the engine, which sticks up higher than our electric starter set up. Running no fan is what allows us to move the engine up. BHP’s Corvair Thrust line was very near the location of the Ford’s thrust line. It was a familiar location, but if you look at most classic planes, the thrust line is closer to the top longeron. In a parasol, there are aerodynamic reasons why it is better off higher on the fuselage. There are also practical reasons like having more room under the engine for the carb and airfiler, and not having these items too low and prone to damage in an accident. Note that the last original has the main axles far forward and it has die spring in a tube gear like we made the last week for Bob lester’s Piet.
Above, another look at the 2000 version of my Piet. Long gear leges and a high thrust line contribute to the plane having a ‘jaunty’ look. The empty weight of this plane was 734#. Not bad for a plane with electric start and brakes and a wet center section of 18 gallons. The rail under the tank is a fuel manifold moulded into the bottom of the center section that would drain all the fuel out of the wing at any angle of climb or decent. My mistake was plumbing it with hard lines instead of braided steel hoses. It could fly in CG with any pilot from 128 pounds to one that weighed 290. It logged about 350 hours in this configuration. Grace produced the cowl by using 2″ scotch brite pads on a radial arm drill press to ‘machine turn’ the cowl. The curve in the paint was traced from a garbage can lid. I dislike a hard paint line between the fuselage and the cowl, a simple curve does a lot to improve the look. Same idea has been on countless classic planes including the last original.
A look at the front end of the plane: The spinner is an 11″ aluminum. I had problems with it cracking and have never had an issue with a fiberglass one. The prop is a 66″ warp drive. Cowling was hinged on the bottom panel to open up in minutes for full inspection. Boxy eyebrow cooling ducts were interconnected in the back by a 3″ scat hose. They were intended to be a quick test made of scrap aluminum, but we had enough fun flying I never got around to changing them.
If you are a Pietenpol builder and you need a motor mount, spring gear, and intake or exhaust, just drop us a note, we will be glad to help.-ww