N5045K, a Highly Modified Salvay-Stark Skyhopper I, Rev. 2

 
Copyright 2006, Doug Robertson, posted on 2006-11-17

After the end of World War II in 1945 there was resurgence in general aviation flying due to the great interest in airplanes. General aviation flying had been curtailed during the war, and returning military veterans had much interest in either learning to fly or to continue the flying they had learned in the stunning success of the Civilian Pilot Training Program started in 1939, the U S Army Air Corps or in the U S Navy and U S Marine Corps Flight Schools for their military service as war pilots. The G I Bill for Veterans for a time even paid tuition for learning to fly and get the Private Pilot Certificate. This G I Bill policy was soon dropped and changed to only pay for advanced flight training after the veteran funded his or her own primary training leading to earning the Private Certificate. Thus, an aviation career-minded veteran could get paid training for the Commercial, Instrument and Multi-Engine tickets and other flight endorsements using the G I Bill within a specified time limit.

A  huge interest in building one's own airplane also grew in this postwar time. After the Civil Aeronautics Authority had effectively stopped homebuilt aircraft construction in 1938, leaving its regulation to the states, only Oregon passed a law permitting construction and registration of homebuilt aircraft designs. After the war, the Federal Aviation Agency (forerunner of our present Federal Aviation Administration) quickly rectified the CAA's oversight, recognizing homebuilt aircraft under a category of Experimental-Amateur Built aircraft. A homebuilt experimental-registered aircraft had to meet the 51% rule; more than half the construction had to be performed by the owner-builder. Construction had to be monitored and signed off by an FAA inspector or a Designated Engineering Representative for sound and safe building principles and practices. Yet, some ingeneous but bizarre designs were built and flown, including one that utilized a war surplus aircraft drop (fuel) tank as the basis for its fuselage. Many of the homebuilt designs both before and after the war were small, single place aircraft of modest power to keep down costs, yet they yielded a gratifying flight and piloting experience. Not all of the designer/constructors made their plans available for others to construct aircraft from. I am sure the liability issue was foremost in some minds, and it must be remembered that the designers/builders were their own test pilots, for the most part. There were those who did not survive the flight test period alive.

There were even some efforts to see who could design and successfully fly the "World's Smallest" fixed wing aircraft.  A homebuilt biplane Ray Stits design, the Sky Baby by Ray Stits' son Donald with 7' 2" wingspan was credited with that title, and the first flight was made by a U S Navy test pilot on NAS Point Mugu's 11,100 foot duty runway 21 in California, only flying the aircraft in ground effect above the runway a short distance for documented proof. Many of these small, single place low or mid-wing aircraft resembled racing planes of the pre-war era, having a small wing area with high power loading, and as taildraggers took some skill to fly safely. They were generally less flight-forgiving than the seasoned general aviation production aircraft built to Federal Aviation Regulations standards and in approved production facilities.

One of the very early homebuilt design efforts after the war was advanced by E. M. "Gene" Salvay and George A. Stark who formed the  Skyhopper Aircraft,  Inc. firm in 1945 in Kansas City, Kansas specifically to design a light aircraft and sell its plans to home constructors. Their "Skyhopper", design of which started in 1944,  prototype NX41770 was a small, single place cantilever low-wing taildragger monoplane of mixed contruction with an open cockpit powered by a 50 horsepower engine. The goal was a plane that could be built for $1,000, and be affordable to many eager aviators in 1946. The prototype Skyhopper NX41770 first flew in 1946.

(I have just received an email regarding the prototype Skyhopper from A-D member Bill Larkins, who has been a prominent aircraft photographer since 1934. He kindly enclosed a picture he took of NX41770 in Culver City, California at the Culver City Airport on May 23, 1946, and I thank him for that). So, I have added the X to the prototype's N number. My references all called it N41770, not NX41770, which Bill's picture clearly shows. It also shows the prototype with an enclosed cockpit. Prototype aircraft usually go through many changes, perfecting the design. Bill's photograph of NX14770 also shows differences in the main gear from the Skyhopper I plans release model. The Culver City Airport, originally called Baker Airport, served the several motion picture studios then in Culver City but no longer exists. It looks in the photo that the field was badly in need of some weed control.

The developed revised plans-built Skyhopper I used a Continental A65 65 horsepower engine and had an enclosed cockpit, with a small built-up back and head rest fully enclosed by a small, tapered clear bubble plexiglass sliding canopy and curved low windshield. The plans version Skyhopper I single place aircraft was a handsome, well engineered design with NACA wing root airfoil 23015 and wing tip airfoil 23012. It had wide spaced fixed, short main gear strutted from the wing spars with streamlined wheel pants and a small tail wheel. A mini-fighter appearance of the Skyhopper 1 with fully cowled engine and sleek small canopy was not hard to visualize by the proud Walter Mitty* plans builder for boring holes in the sky while having the time of his life. A two-place Skyhopper II was also offered by Salvay and Stark, by widening the fuselage just fourteen inches and using a somewhat longer wing. The A65 engine used a two-blade prop with spinner, furthering the mini-fighter image.

A number of subsequent Skyhopper amateur constructors modified their Skyhopper build using various other engines of higher horsepower. The Skyhopper design was described in a feature article in the September 1957 Vol. 6 No. 9 issue of the "EXPERIMENTER" magazine of the Experimental Aircraft Association (EAA) that had been formed in 1953 in Milwaukee, Wisconsin largely by the efforts of a former WW II USAAC pilot, Paul Poberezney and a local group of designers and builders who had been meeting in Paul and Audrey Poberezney's basement. The homebuilt aircraft movement advanced greatly with the formation of many National Chapters of the EAA. I attended some of their meetings at SZP's EAA Chapter in the early 1970s with an EAA  member friend who formerly owned and flew an ERCO Ercoupe. This was before CMA became a General Aviation airport about 1975 or '76, where now the EAA Chapter 723  has their own handsome buildings, Hangar 1 and work Hangar 2 adjacent to the Commemorative Air Force Southern California Wing's two new large hangars.

Gene Salvay went on to make quite as name for himself in leading the North American Rockwell B-1B bomber design team and doing very instrumental international work on the Israeli Aircraft Inds. KFIR (Lion cub) C1 air superiority jet fighter.  Please read my article on the IAI KFIR C2 also in the Airport-Data site, under Warbirds. My understanding is the Salvay family in California is once again offering the original plans for the Skyhopper homebuilt experimental models.

*Walter Mitty-{<"The Secret Life of Walter Mitty," a short story by James Thurber} an ordinary, unassuming person who dreams of being heroic, successful, perhaps a Fighter Pilot like the Red Baron? 

Please click on the upper large photo to see the N5045K Aircraft Profile page with more photos, including inflight. 

 

Design Specifications of Skyhopper I 

 

Engine: Continental A65 65 Hp opposed four cylinder air-cooled

Wingspan: 25' 0"    (Skyhopper II 26' 4")

Wing area: 100 sq ft

Wing loading: 11.7 lbs/sq ft

Power loading: 18 lbs/Hp

Length: 18' 10"

Height: 5' 3"

Weight empty: 650 lbs

Loaded weight: 1,170 lbs

Fuel: 13 gallons 

 

Measured Performance of Skyhopper I 

 

Max speed: 130 mph

Cruise speed: 120 mph

Stall, power off: 42 mph

Initial rate of climb: 800 ft/min

Range: 300 miles, no reserve 

 

The featured Skyhopper of this article, N5045K was first photographed by me last spring 2006 at SZP during a first Sunday Aviation Museum of Santa Paula Fly-In.  I saw the plane again at SZP on 5 November 2006 during another Museum Fly-In as a visitor fly-in and had the opportunity then to speak with the friendly and proud pilot owner while getting more photos. I think my first words were something like "That Skyhopper's sure an older design!" The aircraft designed in the 1940s was first registered as a 1986 experimental aircraft by the original builder named Rosenhan. The present owner purchased the aircraft from the Boy Scouts of America for just $800! It may have been a donation project aircraft. Substantial restoration and modification from the original plans has taken place in this Skyhopper I, yielding a very handsome airplane that turns heads and probably raises the inevitable question-"What is it?"

N5045K is now powered by a Continental O-200 100 horsepower engine, using a McCauley 69X50 clipped tip prop originally from a Cessna 150. The cockpit enclosure clear framed canopy and windshield differs substantially from the original design, being higher, longer and not tapered from the windshield frame aftward. The new cockpit enclosure is roomier, larger and is not completely clear plexiglass as was the original smaller, tapered clear bubble design. The canopy mod more than anything substantially changes the appearance from the original Skyhopper design, but it is undoubtedly less claustrophobic and more comfortable, my opinion. The cockpit is well finished and an excellently filled instrument panel is provided, as shown is the just above photo. The main landing gear are totally changed, with main gear struts tapering out and downward from nearer the fuselage-wing root area, instead of short straight struts wing-spar mounted.  The main gear mod is best shown in the upper picture to the right. My compliments to a nice salvage and restoration of a great homebuilt design, that benefitted from highly professional design beginnings and a caring present owner.

 

Performance of N5045K with Continental O-200 100 Hp, (Owner's figures)

 

Static runup: 2,300 rpm

Max speed: 140 mph at 2,800 rpm

Cruise speed: 120 mph at 2,200 rpm

Stall speed power off: 45 mph

Climb rate: >1,500 ft/min at 2,000 ft altitude 

 

I thank Ken Wang for creating an Experimental category to accommodate this article's aircraft.

 

 

 


 


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