Sword 1/72 Vought V-173 Flying Pancake
Being an old guy I read the Obituaries and Passages sections of my daily newspapers along with the news, editorials and comics. On Sunday, May 12, 1996, I read with interest that "Charles Horton Zimmerman, 88, an aerospace pioneer at NASA's Langley Research Center died May 5, 1996, at Hampton, Virginia." That's all it said. Well, if you dig av history, you'll know a bit about Mr. Zimmerman's "aerospace pioneering." You'll know, for one thing, that the concept and design of the airplane that is the subject of this review were his.
While employed by the NACA Zimmerman experimented on his own time and with his own funds with low aspect ratio* flying wings. Spurred by an informal 1933 intra-NACA competition for the design of a "safe" light plane, Zimmerman refined his ideas, focusing on that objective. His design won the competition. It featured large diameter, counter-rotating** propellers at the leading edge tips of a wing with an aspect ratio of about 1. The left hand prop rotated counter-clockwise, viewed from the rear, and the right hand prop rotated clockwise to "unscrew" the efficiency robbing vortices that spiral off the tips of any wing in forward motion. High-pressure air from under the wing spilling over the tips into the low pressure area above the wing creates these counter-rotating vortices, which spiral downstream in the wake of the wing. The tip vortices spiral clockwise at the left tip and counter-clockwise at the right tip. You will notice that Zimmerman's propellers counter-rotate in an opposite sense to the rotation of the wing tip vortices. Suppressing the wing tip vortices increases the efficiency of a wing. The "Winglets" that you see on the wingtips of modern jet airliners are a mechanically static means of partially achieving the same objective. In Zimmerman's design the wing tip vortices, in the process of being mitigated, also straighten out the prop wash of each propeller. Propeller placement and wing form thus produce three benefits: 1. A more efficient wing due to greatly diminished tip vortices, 2. A wing almost completely buried in straightened prop wash providing both lift and positive control at very low air speeds and very high angles of attack; and 3. More thrust from the near straight prop wash.
Zimmerman won the competition, but NACA considered the design too radical for acceptance by industry or the public. Two other designs from the competition were released to industry for development. Fred Weick's became the well-known Ercoupe and the other became the little known Stearman-Hammond Model Y-1 Safety Plane. Zimmerman continued work on his own with models to prove, and further refine, his concept.
Chance Vought took an interest in Zimmerman's ideas in 1937 and invited him to join the Vought firm as a consultant. The first fruit of this union was Vought Model V-162, an electrically powered captive part-scale flying wing. Model V-173, "Zimmer's Skimmer" was proposed to the US Navy's Bureau of Aeronautics in 1939 as a vehicle to study the STOL and general flight characteristics of an airplane of this configuration. BuAer, following their review and approval of drawings and data, executed a development contract with Vought. BuAer assigned s/n 02978 and work started in Stratford, Connecticut on this flying saucer. It has a wingspan of 23 feet, is 26 feet long and is powered by two Continental Model A-80, 80-hp, six cylinder, horizontally opposed, air cooled engines swinging 16 foot diameter counter-rotating propellers. It is of traditional wood and fabric construction.
BuAer gave Vought (now merged with Sikorsky to become Vought Sikorsky) a Request For Proposal (RFP) in January 1942 for a STOL, carrier fighter based on the unflown V-173. Vought Sikorsky assigned model number VS-315 to this project, which ultimately became the XF5U-1. But that's another story and another model - by Hasegawa in 1/72nd scale - for another time.
V-173 first flew November 23, 1942 in the hands of Boone Guyton, Vought's Chief Test Pilot. Maximum speed was only 138 MPH as V-173 was woefully underpowered. In still air V-173 required a mere 200-foot take off run and a landing roll of only 50 feet. It was fully controllable, under power, at angles of attack up to 45°. As the plane was pitched up it did not stall; it settled very gently under full control about all three axes. The pilot balancing thrust and pitch could control the rate of this settling quite easily. It could not be made to spin while under power.
V-173 made (sources vary) either 171 or 190 flights, accumulating 131.8 flight hours through its last flight on June 30, 1947. It was stored intact, and occasionally shown, at Naval Air Station - Norfolk and was later removed to storage for the NASM at Silver Hill where it awaits restoration and display. Boone Guyton made 54 of V-173's flights. Richard Burroughs, another Vought test pilot, along with a number of Navy pilots all flew V-173. Colonel Charles A. Lindbergh is reputed to have made flight number 34, but one of my sources disputes this.
S. Fleicsher did the accurate and attractive rendering on the top of Sword's standard flimsy, end-opening, crushable box. The bottom of the box has color profiles of the airplane in its two slightly different main configurations. The first sans wheel pants and with white star-in-blue roundel national insignia. The second has wheel pants and blue outlined white bars added to the insignia.
The box contains one tree of 14 very good looking parts injection molded in a medium hard, styrene of medium gray color, 18 well cast resin parts, two vac-formed clear parts - the windscreen/hood and the lower nose glazing, a small well printed decal sheet with, inter alia, the two styles of national insignia and a single folded European A4 size sheet of instructions. The instruction sheet has a brief historical note by Chris Hughes, a parts map, a four-step assembly sequence, a painting guide for the airplane in its final configuration; a color guide and a color key.
All four injection molded wheel pants parts in the review kit had easily filled sink marks in their outer surfaces. One of the resin parts was broken as usual. I have never reviewed a Czech kit in which at least one of the resin parts was not broken. Come on guys - quality control is the name of the game these days. Careful packing into stout top-opening boxes would reduce breakage. Hint, hint.
If you assemble your models out-of-the-box, this kit will be a quick build for you. The only correction required for a very accurate model is to shorten and widen the slots in the spinners for the prop blades. If you suffer from AMS, you'll need to add the small fixed fairing on each main landing gear leg that blends with the diagonal struts when the oleos are extended in flight.
Un-panted wheels are not included for the first configuration of the plane illustrated on the back of the box so if you choose to do this configuration, you'll have to raid your spares box for appropriate wheels. You'll also have to rescribe the "ailevators" to add separate elevators and you'll have to delete the big elevators in the trailing edge of the wing proper.
The prop blades, being hinged, coned backwards quite a bit when the airplane was parked. This is best shown in the photo at the top of page 7 in Steve Ginter's book, referenced below.
I like this kit. It's simple and almost dead-accurate out-of-the-box and it is certainly an interesting oddball type. It is my kind of airplane. Remember to check your references very carefully if you choose to deviate from the configuration provided in the kit. The differences were few, subtle and important. Score another hit for Sword. Good on you lads.
Naval Fighters Number Twenty One - Chance Vought V-173 and XF5U-1 Flying Pancakes: Steve Ginter, Steve Ginter Books, Simi Valley, CA, 1992, ISBN 0-942612-21-3.
Aviation History Magazine, September 1997: Stan Soloman article - When A Pancake Flew.
Scale Aircraft Modeler Magazine, Vol. 3, #2, Fall 1975: Wayne Moyer article - Flying Flapjack.
Historical Aviation Album, Volume 8: Arthur L. Schoeni article - Vought XF5U-1 Flying Flapjack.
Air Enthusiast Magazine, June 1973: uncredited article - The Untossed Pancake.
Wings/Airpower, Issue unknown: Francis J. Allen article - The First Flying Saucer.
Time/Life Aviation Series - Designers And Test Pilots.
The Aircraft Treasures of Silver Hill: Walter J. Boyne, Rawson Associates, New York, 1982, ISBN 0-89256-216-1
Aeroplane Monthly Magazine, November 1975.
* ASPECT RATIO = The square of the wingspan divided by the wing area. Thus the greater the wingspan in relation to the wing chord, the higher is the aspect ratio and, conversely, the less the wingspan in relation to the wing chord the lower is the aspect ratio. Some sailplanes have aspect ratios in excess of 15, while Concorde, and some delta-winged fighters, have aspect ratios of less than 2.
** COUNTER-ROTATING vs CONTRA-ROTATING: Things are counter-rotating when they rotate in opposite directions on parallel axes. Things are contra-rotating when they rotate in opposite directions on the same axis. The P-38 and P-82, for example, had counter-rotating propellers, whilst the Boeing XF8B-1 and Westland Wyvern had contra-rotating propellers.