Waco YPF NC-15700 (S/N 4375)
Waco NC-15700 was one of two model YPFs built by Waco Aircraft Company. From the dates it appears that these two, serial numbers 4374 & 4375 were built concurrently. These were the first of the “new” style “F” models, commonly exemplified by the later and more numerous UPF-7. The design exhibits several advances over the previous F series, notably:
- An all new fuselage design.
- A dramatically new and more sophisticated empennage design, which was originated in 1935 with the new Custom Cabin (YOC & CUC).
- An “improved” Clark Y airfoil.
- The introduction of the “Coupe Top” option for enclosing the pilot’s cockpit. (It should be mentioned that this feature does not alone define the YPF/ZPF series. This was an option on these as well as all subsequent “F” models. All YPF/ZPF aircraft produced had this option, hence the myth that it was an exclusive feature of the type.
The natural question arises today regarding similarities to the more common and prolific UPF-7. On the surface it appears that it is a UPF-7 with a canopy and a bump cowl. Since NC-15700 was the prototype, this is a natural conclusion. But “there’s more to the story”:
- The landing gear is similar to the 1935 Custom Cabin, both in structure and tread width. It is also attached to the fuselage in a different manner.
- The fuselage, whereas generally similar in design to the UPF-7, is simpler in detail and lighter. It is also 3 inches shorter, all in the rear cockpit bay.
- The center section is considerably lower, accommodating the 2 degree dihedral of the upper wings. Also, it has the traditional tapered cutout vs. the wide cutout specified by the government on the UPF-7. The first few UPF-7s, which were built for civilian consumption, also had the lower center section and cutout.
- The trim system is cable driven.
- The fuel tanks are individually plumbed and valved.
- The torque tube geometry gives the YPF a different aileron feel…more like a Custom Cabin.
- The engine. ATC 586 covers the Jacobs powered YPFs and ZPFs. The 220 Continental did not appear on this “new” F model until 1937 on the UPF-7. The UPF-7 is actually covered under ATC 642 despite the similarities noted in the type certificates.
And, of course, the Bump Cowl. This aircraft was the last production Waco with a factory installed bump cowl. Subsequent YPFs and ZPFs all had the later design smooth cowls, concurrent with the Waco Cabins of the time. The original cowl was with the project when acquired, but a new one was replicated by D & D Classic Restorations, Covington, Ohio.
Miss Johnston’s order
Waco NC15700 was delivered new to its original owner, Miss Connie E. Johnston, on November 5, 1935. Having been special ordered by Miss Johnston, it was fitted with the most deluxe equipment available at the time, and finished in a most opulent manner, all to her specific requests. Waco’s Engineering Dep’t Airplane Order (enclosed) documents the detail and scope of Ms. Johnston’s order. Some specifics:
- Colors: Although quite unusual, the Purple and Blue was in Waco’s palette of available colors. It appears that they were reserved, however, for quite special airplanes.
- The logos and stripes: This design was actually submitted by Miss Connie Johnston for application on the airplane. It is her initials, C and J, lying horizontal. This logo was specified on the fuselage sides, cowl bumps and wheel pants. In addition to the engineering sketch (enclosed) we obtained factory photos to assist in the layout (enclosed).
- The Chrome Struts: These were also specified in the engineering order, as were the stainless wires. Painted steel wires were the standard of the day.
- Landing lights: These were factory installed Grimes retractable. The original mounting plywood was still in the upper wings which were subsequently remanufactured, of course.
- Wheel pants: Yes, folks, they are ALUMINUM! As a matter of fact, they are original Hill Aircraft Streamliners. Take a look at the original manufacturer’s plate on the left pant.
- No Waco logo? Miss Johnston specifically requested this. See line 6 of the October 9 amendment to the original sales order.
The project airplane was quite complete, but in a substantially disassembled state when it arrived. Further disassembly down to individual parts was accomplished. Some repair was necessary to the fuselage account wear points, but it was essentially a usable assembly. The gear attach points were removed and new ones welded in which required extensive fixturing.
A complete new wing set was built using all new parts and materials. The extensive wood fairing stringers and formers were all replaced with new. New fuel and oil tanks were fabricated. The empennage was reconstructed using new wood parts.
The landing gear was completely rebuilt using newly manufactured internals. The brace strut system was all reconstructed with new parts and materials. The tailwheel system was remanufactured as well.
New interplane struts and center section struts were fabricated and chrome plated as called out in the original factory order.
The numerous fairings were usable as patterns and all new sheet metal was fabricated. The coupe top structure and windshield were remanufactured using some original parts and factory drawings.
A new engine cowl was fabricated using the original cowl as a pattern. The cowl was beautifully reproduced by D & D Classic Restorations. The original latching hardware was refurbished and reused.
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