Bushby's"LONG MIDGET"

By George Hardie, Jr.

,. .*:

E ver since designer Dave Long brought out his "MidgetMustang" (see SPORT AVIATION, July, 1959) there

have been many homebuilders interested in building onefor themselves. Several have been built and some are nowunder construction. Bob Bushby of Dolton, 111., EAAmember 26, recently completed his "Midget" and now hasover 28 hours of flying time on it.

Bob was working as "line boy" at the Joliet airportlate one night in 1952, talking with Dr. Francis Torreyof Villa Park, 111., about prospective designs to build.A Piper pilot on a ferrying flight stopped in aboutthen and revealed that the estate of the late DaveLong, including jigs and parts of his "Midget Mustang",was about to be disposed of. "Doc" Torrey lost no timein contacting Mrs. Long and obtaining the "Midget"material. Almost immediately construction was startedon two aircraft, using some of the parts already com-pleted and making up others from the jigs.

Bushby undertook construction of one of the ships,working in a garage located on his parents' farm. Af-ter about a year the wing panels and fuselage shell hadbeen completed, when Bob decided to take a job inSan Antonio, Tex. The parts of his aircraft were takenover by Dr. Torrey, who with some of his helpers work-ed on it spasmodically for the next two years. ThenBob returned from San Antonio and made arrange-ments to take over the project again on a co-owner ba-sis with Torrey, who was to furnish the material andBob the labor. The aircraft was completed under thisarrangement.

Bob had one advantage in working on this "Mid-get" — the bulkheads were those from the Long col-lection (although he later formed several more forother projects). He also had the original Long for-mica jigs to work with, forming the aluminum by handusing a plastic mallet or hunks of lead. The ribs are of.025 and a shrinker was used to complete the bend.On the bulkheads, made of .032 aluminum, the edgesare crimped as described in Jim Graham's "Tin Bender"articles, since the greater thickness precludes use ofthe shrinker. First 24 ST was tried, then SO, formingit and having it heat treated. This method produced

warpage, so blanks were cut to shape from 24 SO, thenheat treated and kept in dry ice for approximately18 hours, and then formed before they hardened. Bobfinds that he can make a metal rib in about one third thetime it takes to make one of wood (counting varnishing,etc.).

Wing skinning was no problem. With the helpof an inexperienced friend one panel was covered ineight hours. Thickness of .025 was used and the ri-vet holes were dimpled. Bob says an easier methodwould be to use .032. use smaller rivets closer together,and countersink.

Dimpling by hand causes problems in lining up therivet holes. Other design changes he'd recommendwould be the use of a piano hinge for the elevators,eliminating the tedious problem of lining up hingesat the time of assembly. A trim tab should also beinstalled to ease the work of cross country flying. Abungee system would probably be a useful substitute.

The fuselage requires an accurate jig to hold thebulkheads in place and presents probably the mostdifficult job on the whole aircraft for the amateur. The"tail cone", the section from the wing trailing edgeto the rudder post, is made first. Sheet stock wasused without prior forming, since a bending brake ofthe required length was not available. Burlap strapswere used to draw down the aluminum as it was ri-veted. This produced a satisfactory job, says Bob,but preformed skin for wing leading edges and fuselagewould cut down the labor considerably.

Wing leading edges used on Bob's ship were pre-formed at Piper Aircraft for Dave Long. They differfrom the drawings by having a larger radius. Bobthinks this gives better stall characteristics to hisship, although it affects the speed. He says he flewanother Midget built with leading edges formed ac-cording to drawing specifications and found it fasterbut it had a quick stall with little warning. Evidentlythis larger leading edge radius was a modification by

Cantinued on next page

Bob's "Midget" and a PA-17 at the farm.SPORT AVIATION 5

BUSHBY'S . . . Continued from preceding pageDave Long that was never incorporated into his draw-ings.

After completing the wings and fuselage of theship, Bob claims the work is only half completed. Thecontrol system was not shown in Long's drawings soBob and his partners had to design one. Cessna rudderpedals were used. Ailerons are connected differentiallyto counteract drag. The cockpit is quite roomy - 22 in.wide, and the instrument panel is mounted about 29in. from the seat back, giving plenty of leg room.Bob wears a back-pack chute with plenty of room. Thewindshield is from a PQ-14, and although it is some-what larger than necessary, it worked out very well.The rest of the canopy is hand formed, and is hingedon the right side. It is designed for a tight fit tothe windshield and at the cockpit rear bulkhead, andis operated by sliding rearward one - half inch andthen flopping over to the right. Visibility is excellent.

The cowling and spinner were adapted from an-other ship in hopes of saving time in order to makethe 1959 Fly-In. However, trouble with constructionof the gas tank delayed completion and the initialflight did not take place until September 9. The shipis heavier due to the large canopy, the oil tank is of ironinstead of aluminum, and the cowl is larger than shownon the drawing. The engine cooling baffles are some-what unique in that the engine cooling is entirely in-dependent of the cowling. This simplifies cowl con-struction to a great extent and works very well. Atthe Fort Wayne air races Bob had to wait over 30minutes, idling the engine. The oil temperature neverexceeded 140 deg. and the cylinder head temperaturenever got above 225 deg. F.

Landing gear is of spring steel, mounted on a torquetube connected to the rear spar. Bob says it's a bitstiff and if he was to make another he would use ¥4 in.stock rather than the % in. called for. Narrowingthe strut would also allow a softer gear. Ideal wouldbe a Wittman tubular type mounted off the enginemount ahead of the firewall. This type would saveabout 15 Ibs. of weight and provide a simpler, softergear.

The flight characteristics turned out to be muchbetter than expected, says Bob. The plane is com-paritively easy to fly, and is similar to a Culver Ca-det in handling. Test flights were made from Mor-ris airport off the concrete strip. High speed testruns made on Bob's farm sod strip resulted in losingclips out of his Goodyear brakes caused by the vibra-tion. He's not had this trouble since, although hehas been flying it off the 2000 ft. farm strip. Take-off distance is approximately 600 ft. and climb-outat 90 mph indicated is steep. With no wind a 400 ft.altitude can be attained by the time the end of thestrip is reached. Rate of climb checks out to be 1750fpm.

Aileron rolls can be performed with both feet onthe floor. The stall characteristics are very good -power off stall speed without flaps is 63 mph, whilestall with full flaps is at 57 mph. There is amplestall warning in the form of tail buffeting at 5 to 10mph before the actual stall. Recovery is very quickupon relaxing elevator pressure, or applying power.The flaps are very effective and give the plane a niceglide. The procedure Bob uses is first or second notchunder 100 mph and full flaps at 80 mph, with an ap-proach speed of 70-75 mph. Without power the ap-proach is like that of a loaded Tri-pacer, so Bob likesto hold a little power to flatten it out. Three pointlandings are always made.

1. Bulkheads, spars, flaps and aileron. 2. Landing geardetail. 3. Cockpit and panel. 4. Tail wheel and rudder postdetail 5. Wing panel ready for top skin. 6. "On the gear"after one year's work.

Cruising speed is not as good as expected - 148 mph,but Bob thinks this is due partly to the propeller heis using. It is a cut-down metal prop which he classesas a "climb" propeller. This does not provide theideal speed range and Bob feels that a two-positionprop would provide what he wants. Fuel consumptionis 4.2 gal. per hour, which indicates a low power out-put. The present propeller turns up 2250 rpm at take-off and 3000 rpm full power in level flight. Sincehe has plenty of take-off and climb performance, a

Continued on Page 286 MAY 1960

FACTS ON AILERONS . . .From page 16to be rather stiffly made to take all the control andair loads at its pivot point and distribute it without de-flection. In short, tip ailerons and their controls canwork out to be heavier and more complex than plainailerons, and the problem grows more acute with in-creased span.

A tip aileron is of course an extension of the wing,and normally would have the wing's airfoil if a noticeableand objectionable discontinuity is to be avoided wherewing ends and aileron begins. Given any commonly usedwing airfoil, the center of pressure of a tip aileron willhave that airfoil's normal amount of center of pressuretravel with varying angle of attack. This quirk leadsdirectly to problems of control linkage and leverage.NASA found that tip ailerons usually resulted in ap-preciably heavier control stick loads—up to three timesas great for plain ailerons giving the same amount ofrolling action. If the pivot point is located reasonablyfar back on the tip aileron, there is of course a greateraerodynamic balancing effect, which would be usefulin reducing control loads if it were not for one thing . . .it appears to aggravate tip aileron flutter problems. Youcan stop flutter by moving the pivot point forward, butin so doing you reduce aerodynamic balance and increasethe control forces. The use of aerodynamically efficientlong, narrow tip ailerons leads to a reduction in struc-tural stiffness and an increased proneness to flutter. Toget away from this by going into short, wide tip aileronsleads to increased control loads because an airfoil ofgreater chord and consequently greater center of pres-sure travel is obtained.

In the end, the lightest, simplest, best-performingmethod of minimizing adverse yaw effect proved to bethe Frise type aileron, and retention of aileron controlwell into the stall is now obtained by wing twist, whichmakes the root stall first and the tip stall last. Tipailerons mess up the wing tip vortices and add drag, theyspoil climb, they are structurally heavy, and pose somuch of a flutter and control force problem that theyseem a profitless path for designers to follow. This isnot to say that they won't work or can't be made to work,but that since it is possible to gain the desired advantagesmore easily and reliably by using Frise ailerons andtwisted wings, the fellow who wants to get into the airwith minimum effort and maximum safety would dowell to stick to common aileron forms. After all, commonfeatures of today's airplanes are used not because of thedesigner's lack of imagination but because they are theresult of many decades of work to find the most practicalways of making airplanes! Q

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BUSHBY'S "LONG MIDGET" . . .From page 6 'higher pitch prop would give an improvement. A con-trollable pitch prop would of course be the best.

The ship turned out to be heavier than the 525Ibs. empty weight of the original built by Dave Long -Bob's weighs 572 Ibs. empty. Additional weight isdue to the canopy, cowl and thicker spar stock usedin the wing. Wing loading works out to about 10 Ibs.per sq. ft. The ruggedness of the ship is evidencedby the 7% G's registered in flight test.

Bob is completely sold on the superiority of metalconstruction over "tube and rag". He says the actualhours required for construction are no more for metalthan the more common fabric job, if everythingis counted. He figures that it's possible for the averagebuilder to build a "Midget" in about two years ofspare time work if he's not held up by a lack of capi-tal, an overly-demanding full-time job, etc. Durabilityof metal over fabric, with economy of upkeep as an add-ed feature, makes the former extremely attractive.He says he was comparatively inexperienced at the startbut close study of CAM 18 and the assistance of availableinformation helped a lot. In particular he found the"Tin Bender" articles by EAAer Jim Graham (seethe EXPERIMENTER for July, September, October andNovember, 1957) to be very helpful.

Bob works in the research department of SinclairOil Co., and is a licensed A & E mechanic and a com-mercial pilot with flight instructor's rating as well.He does A & E work part time, and his "spare" timehas been devoted to the "Midget" project. He hasoffered to assist other "Midget" builders in EAA -his home address is 14612 S. Edbrooke Ave., Dolton,111. A

Error in "Tapered Wings"An unfortunate typographical error appeared in

John Thorp's article "Tapered Wings are for Birds -and Very Large Airplanes" in the April issue of SPORTAVIATION, which changed the meaning of one sen-tence. On page 7 at the bottom of the center columnthe sentence should read "The maximum lift coef-ficient of a wing section is a function of its local Rey-nolds number".

Author John Thorp is preparing other factual andeducational articles which will appear in future issuesof SPORT AVIATION. Next to appear will be "WhichAirfoil Section?" in the June issue. "How Much As-pect Ratio?" and "Performance at a Glance" will betwo in the series to follow. We indeed appreciate theopportunity to present this valuable information author-ed by one of aviation's outstanding aircraft designers.

ONEMAN

HELICOPTER• True copter, no belts, chains or power plant shortcuts.• You build from our drawings.• Parts available.• Send $2.00 for photo, 3-view drawing,

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H E L I C O P T E R R E S E A R C H C O .BOX 121

LA MIRADA, CALIFORNIA

28 MAY 1960