Mail Sack, 10-19-12, Piet and Wagabond notes.

Friends,

Here are some of the letters sent in. On the topic of Pietenpols;

Pietenpol builder Harold Bickford writes:

“Thanks for posting this William. The article certainly adds to the information base re: a Piet with Corvair. I’m assuming the Lycoming weighs about what a Continental 65 weighs, i.e. 170lbs. so about 55 of the 95 lbs would be from the Corvair. The performance and CG advantage for the reasons stated are incentive enough to use the Corvair.. I am curious at what gross Bob’s Piet is operating given that the typical gross per Pietenpol is 1080lbs. As an aside enough 1/4″ x 1/2″ was processed over the last two days to make the ribs for our Pietenpol. A band saw, planer and Aerodynamics for Naval Aviators are three useful tools/items that I’m glad are in the shop. – Harold”

Harold, the photo below is our Pietenpol at Brodhead 2000. We flew it up from Florida in 14 hours. We stopped about every 2 hours to take a break and gas up. The empty weight of the plane was 734#. On every one of the loaded take offs the plane was leaving the ground at 1270 to 1280 pounds. At other times we flew the plane as high as 1360 pounds. It was really limited by space, not weight. In air cargo slang it “Cubed out instead of grossing out.”

 

Bobs Piet in the story is 739# empty. He has an 18 gallon fuel system. The 8oo fpm number refered to the plane with full fuel and two 180 pound people in it on a 70F day. The piet is a very strong plane when it is well built. The traditional 1080# gross weight is a number that was based on a Ford engines climb performance limitations. Bob’s previous gross weight was limited to 900 pounds or so on a very hot day for performance reasons, and maybe 1100 pounds on a very cool day with a long runway. These types of limitations on his aircraft are effectively removed by the Corvairs power.

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Builder Sonny Webster writes:

“Saving weight to increase climb is like saving money to increase profits – eventually you run out of places to cut. To increase performance in a sustainable fashion you will eventually need to increase power/revenues.”

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On the temps article with the Wagabond picture;

Builder Jerry Mcferron writes:

“Would you please post the real world cruise, climb, and useful load numbers for the Wagbond?-Jerry”

 

 Jerry, the picture above is just after Gus did the first flight in the plane, he is shaking hands with Dave. You can’t tell these things in pictures, but both Gus and Dave are about 6’3″ and they are both built like NFL defensive linemen. The empty weight of the plane was 804 with a 2700cc Corvair. The plane didn’t have a 5th bearing, but it had the heavier pre-gold oil system. It also had a full panel of vacuum driven gyros. We arbitrarily set the gross weight on the paperwork at 1320# to make it light sport compliant. We did a test flight at 1625 pounds during phase one. I was not worried structurally because we used a PA-22-108 colt airframe as the basis of the plane (this is no long legal under the current FAA guidelines for homebuilts) which has a gross weight of 1650 pounds. The lift struts are off a 160 hp tripacer with a 2,000 pound gross. If you study the gross weights vs the gross climb rates for all the PA-20 and -22 series of pipers, I believe that they set the gross at a number that still gave 500-600 fpm on a standard day. In short it was performance based, not a structural issue. If you are working from the Wag-aero plans and working with wood spars, it would pay to go back and not assume the information to be interchangeable metal spared planes.

The plane is not a speed demon. its fair to say that it will do 100 mph on 5 gallons per hour. It 100 hp climb rate at 1320 pounds is about 700 fpm on a standard day. It is a good all around aircraft, but not an outstanding performer on any single front. We are currently redoing the plane with some detail work intended to clean it up and repower it with a 3000cc Corvair. I am shooting to bring down the empty to 780 pounds or so. We will have more data in a month or two. If you would like to see a video of the plane in flight, look at this link to you-tube, it has 7,000 hits:-ww

http://www.youtube.com/watch?v=B7XhuWmqcPw