Piper & the USA-35B

[RAVC]

Can anyone tell me why this airfoil results in higher speeds for the Pacer/Tri-Pacer then the other aircraft that use it?

[PACERGUY]

It is not the airfoil it is what is attached to it. PA 18 tend to be very draggy with all that exposed gear and controls. DENNY

[RAVC]

Okay, cleaner aerodynamics of the aircraft. Would you expect to see much in the way of increases in cruise speeds for earlier, low hp aircraft like the Colt, Clipper or, Vagabond/Wag-A-Bond if they were equipped with higher output power engines? These aircraft appear to be quite similar aesthetically to the Pacer. I think the Vagabond/Wag-A-Bond may be limited to the use of much smaller engines - I do not know why. I've actually seen a few examples of a Super Wag-A-Bond that looked interesting.

[dgapilot]

Gilbert Pearce has a 160 on his PA-16, his cruise speeds are right up at red line. You are working excess power vs structural limitations.


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[Gilbert Pierce]

I sure love seeing the rate of climb needle quivering at 1100 to 1200 fpm at 80 mph.

[RAVC]

Yes, but is this a question of differences in the wall thickness or diameter of 4130 or is 1025 used in these lower power aircraft? Several of the Short Wing pipers look so similar it suggests the distinctions are internal. I guess the structure of the frame, rather than its composition might also be a factor.

Gilbert - That's a lot to handle in a small airplane. Do you have a relief tube installed?


I intend to look into these examples of the Super Wag-A-Bond for the learning exercise. In general, I would prefer a larger plane but this intrigues me. One of these, C-GKGX experienced a fatal accident last spring. Not the kind of story you want to learn about but I was looking into this airplane at the time and stumbled onto the accident report. Apparently, the pilot forgot to return the flaps to neutral after takeoff so they remained at 40-degree down.

[Steve Pierce]

The structures were increased as the airplanes models progressed. Higher Vne and gross weight.

[blue44]

seems like the reduced wingspan of the swp would account for the speed difference in aircraft using the usa-35b ? More discussion on supercub.org - here - (https://www.supercub.org/forum/showthread.php?36076-Why-USA-35B)... :)

[dgapilot]

There are some structural differences, but like Steve indicated, most were due to increases in gross weight and Vne speeds. Even the PA-22-150 is primarily 1025, not 4130. Piper was a business that was all about the bottom line. In the '30s, 40's and 50's, 1025 tubing was less expensive than 4130 so where applicable the lower cost material was chosen. In a truss structure, the majority of the elements are under compression, and there is no difference in strength for column buckling between 4130 and 1025. Looking at the evolution of the PA-16 to the PA-20 to the PA-22, the primary differences is the forward fuselage of the PA-16 has a fuel tank in the nose, so the front structure needed to account for that. With the PA-20 and the wheel controls, that forward structure was upgraded for those changes. There were also changes for the structure between the spar carry through structure, but otherwise was the same as the PA-16. As the gross weight of the PA-20 increased, a couple tubes got bigger, but very few. The biggest changes came with the requirement for individual seat belts, and the tubing to attach the center attach for the belts increased. The cabin overhead changed as well to provide for additional head room for the rear seat, but the majority of the fuselage structure remained 1025. Wing changes again were dictated primarily by GW and Vne, but also by the removal of the fuselage tank from the PA-16 and a wright wing tank on the PA-20. THere are a couple spar stiffeners that art bigger on the PA-20, and the forward strut has an insert to increase rigidity. The later PA-22s added another rib to each wing to allow for the higher speeds. Hope this gives what you are looking for. Oh. yeah, by the 1980s, Piper went to all 4130 for the SuperCub, but not for a strength issue, for a cost issue. By the 1980s, 4130 was cheaper than 1025.

[akflyer]

AOA on the wing is another big one. Look at the difference between the PA12 and the PA18.

Speed and rate of climb has a whole lot to do with drag. My pacer is a lot slower than one with wheel pants, tiny tires and covered gear, but I go in and out of places that the tiny tired pacer will only go into once and be helicoptered out of. It is not as much a function of the airfoil as it is every other mod that has been done to the various models.

[RAVC]

Yes, all of these responses help. The letters I sent to owner's of these aircraft have largely been ignored as I have received no responses. I can honestly say that I am not completely surprised at this. I was hoping the owner's of these aircraft could place me in contact with the builder so I could understand how they accomplished the modifications they implemented. For example, the few of these I have learned of added flaps and were also on floats.