Models of Frank Smith's Miniplane have been built and flown by scores of modelers over the decades. Homebuilt planes are popular scale projects partially because the level of detail necessary to faithfully reproduce the full-size airplane is less that with a production plane. Sig Manufacturing introduced a radio controlled kit model of the Smith Miniplane back in the 1970 that is still available for purchase on their website today. This article from a 1961 issue of American Modeler includes plans for a .29-powered control line version of the Smith Miniplane having a 34" wingspan, along with some history on its development.
Frank Smith and His Lightplane Legacy
Story, model and plans by Tom Henebry
Frank Smith in his Playboy; a machinist by trade, Frank learned to weld so he could build the ship.
All model builders do not end up manufacturing airplanes, but most of aviation's creative minds first found an outlet for their aeronautical ideas by hacking away on a chunk of balsa wood. Take Frank W. Smith for instance, he followed the same path as many successful aviation enthusiasts. His name is as well known to amateur aircraft builders as the bearded Smiths, "Trade" and "Mark," are to the buyers of cough drops.
Starting back in the roaring "20's" with the old solid scale models (replaced now with today's "plastics") he progressed to gliders then to rubber models in the classic pattern of the day. Models in the 20's were far from roaring, no tender-eared citizens complained to the local constabulary about the gliders and rubber jobs making too much noise. Then Frank got a taste of flying in a Curtiss Junior; the models just had to wait. Flying from a barnstormer's strip in Missouri the Junior convinced Frank that this activity was for him. Unfortunately 1929 was a bad year for almost everything so Frank took Greeley's advice and headed West.
Smith spent the next decade outside of aviation physically but not mentally. While he was working in a machine shop, or later when he was starting his own shop, there was usually a flying or model magazine within reach. During the war years, although working long hours, Frank's interest in models was reborn. Gasoline engines fascinated him so he began making control line speed models. Engines were hard to get and most of the ones available were pretty sad, so he promptly made his own engines.
The power of Frank's mills was proven when an airplane-engine combination built by Frank and flown by Rolf McPherson walked away with a big contest in the Los Angeles Coliseum during 1943. The model weighed a whopping 8 lbs., was powered by his homemade engine of .59-.60 displacement. To prove it was no fluke the same 8 lb. monster was flown at 105.75 mph for a new record that held up for several years. Along with his very successful models and engines the energetic Mr. Smith developed the first wet cell battery for ignition engines and one of the first storage battery powered starters seen on the West Coast.
Mrs. Dorothy Smith and her son Don admires Henebry's model Miniplane.
Frank Smith taking home some hardware from a model contest in 1943. He had designed and built both the plane and the power plant.
Models were fine but the old flying bug bit again and in 1949 Frank got his pilot's license. The ink was hardly dry on this precious document when he bought the remains of a Travel Aire 12 W. This was a real basket case that he rebuilt from the tail wheel up. Powered with a 145 Warner the slicked-up red and silver ship helped Frank pile up some hours in his log book, but it was too big and bulky to suit him.
With Ray Stits and a few more interested people he helped form E.A.A. Chapter #1 in Riverside, Calif. Ray was building the prototype "Playboy" and Frank followed the progress closely. Delighted with the original Stits Frank built the first Playboy from Ray's plans. This was a true sport plane and Smith logged many hours in it. He still had a preference for biplanes; when one voice in a group of hangar flyers suggested he build another deck on the Stits, he countered with a sketch drawn on the hangar floor. "That's what it should look like," he said, "and I'm going to build it." Eight months after he made the sketch on the hangar floor, the first Smith Miniplane was rolling down the runway on its maiden flight. This is a fantastically short period of time to build an airplane even from a set of plans, and to start from scratch on a new design, it must be some sort of a record.
The Miniplane was all Frank wanted in an airplane; stressed for 9 G's it could do any maneuver in the book. With a husky 100 HP Lycoming roaring in its nose, it made the proverbial home sick angel look like she was dragging her feet. The perky little bipe was a crowd stopper on the ground as well as in the air. Anytime it was on the field it attracted crowds of admirers and it wasn't long before Smith started getting requests for plans. Lee Wainscott took on the job of drawing up the plans while Frank started building another Miniplane very much like the first but with a few minor changes. The second ship was about seventy percent complete when tragedy struck. Without warning Frank Smith died of a heart attack. His family and friends were stunned and grief stricken. For a long time the second Miniplane stood in mute silence under a mantle of dust.
With the help of friends and her son Don, Dorothy Smith, Frank's widow, decided to see Frank's work carried on. Lee Wainscott and Howard Terrill finished the second Miniplane and the plans were made available to builders everywhere. Tom Messick flies the Miniplane to fly-ins and Don follows in the family Piper Vagabond. Don, who holds a student ticket, has piled up many hours in the Vagabond. He far exceeded the cross-country requirements for his private license with a tremendous 4,200 mile round trip flight to the 1960 EAA Fly-In at Rockford, Illinois. Don's itching to get his hands on the Miniplane but the FAA requires a private ticket to fly an experimental aircraft and until he's 18 Don will have to be content to remain as a student pilot on the Vagabond.
Present at every regional or national Fly-In, Dorothy Smith is interested in all homebuilts but especially Miniplanes. She intends to keep low-cost plans available to anyone who wants to build the plane. To date there are 7 Miniplanes flying, over 30 in various stages of construction and more than 100 sets of plans in circulation. There will be more Mirriplanes and certainly for many, many years they will serve as a flying tribute to Frank Smith:
Control Line DSA Miniplane
Big and little Miniplanes, below.
Full size drawings for the Miniplane are a part of Group Plan #161 from Hobby Helpers, 1543 Stillwell Ave., New York 61, N. Y. (85c).
One of the best of the newer homebuilt biplanes is the late Frank Smith's "Miniplane." Called the DSA (Darn Small Airplane) it is by no means a midget in performance. Stressed for 9-1/2 G's the stubby 17 footer will outclimb and out stunt most contemporary designs.
The 2" to the foot scale model described in this article inherits all the get-up and go of the prototype. With the symmetrical airfoil and a hot .29 the DSA will stunt as good as many models designed for aerobatics alone. For the scale builder who wants to load up on detail the flat bottom scale airfoil and reference to Jim Triggs scale drawings in the March 1960 American Modeler should produce a contest winner.
The model was built from plans for the real airplane and differs only slightly from the original Miniplane (N90P). Since all the airplanes of this type are homebuilt, each one reflects changes desired by the individual "manufacturers." Because each one is different the only real yardstick of scale can be the original designer's drawings. Plans for the full sized airplane or further info on the Miniplane can be obtained from Mrs. Frank Smith, 1938 Jacaranda Place, Fullerton, Calif.
Construction begins with the upper wing. Your best hard balsa should be used for spars and all ribs. Except for two shorter center ribs, cement all in place. Place 1/8" x 1/4" in back of each spar in center section as a spacer and cement another piece of 1/8" x 1/4" from the last full-sized rib on one side of the center section to the last full-sized rib on the other side. The two center section ribs may be traced from the plan in the fuselage side view. These two ribs are cemented in place and top spar, wing tips and leading edge covering added while wing is still flat on plan. Mark position of 1/4" x 1/8" strut sockets but do not add them at this time. Remove wing from plan, add 1/8 " sheet gussets at wing tips and smooth up complete structure with sandpaper wrapped around a block of wood. Both bottom wing panels are made in same manner but let. the 1/4" x 1/8" spars extend past root rib about 2 1/2". Strut socket centerlines should be marked on lower wings while wings are still on plan.
The fuselage is started by stripping off two 3/8" wide strips from 3/16" sheet and pinning them in position over top longeron. Fit large piece of 3/16" sheet that extends from nose to cockpit area and cement to top longerons. Build up rest of side structure from 3/16" sq. With both sides positioned accurately one above the other, drill 1/8" dowel hole thru both sides and slot both sides for 1" wide piece of 1/8" plywood that will hold bellcrank. If you intend to rig airplane with flying and landing wires drill two 1/16" dia. holes at lower forward part of fuselage that call for 1/16" O.D. aluminum tube. Make sure front of fuselage is square with top longeron before separating sides.
Cut formers F-1 and F-2 from 1/8" plywood, position them as shown. When they are aligned drill engine mount holes and fuel line hole. F-2 cements in position as first step in building fuselage. Use temporary cross pieces of 3/16" sq. in bottom forward part of fuselage and build up basic fuselage box structure. Split 3" length of 1/2" sq. diagonally and cement it in both comers of fuselage and F-1 as a gusset. Pin firewall, gussets and side together with dowel about 1/2" from top and bottom of both sides. This will give added strength to the joint to absorb engine vibrations and impact loads.
Slip 1/8" dowel cross piece and 1" x 1/8" plywood bellcrank platform thru their respective slots, cement and cut off flush with outside surface of 3/16" sheet. Bend landing gear parts from 3/32 wire and install in place. Bind rear strut to piece of 1/8" dowel and coat with cement. Cement 1/8" plywood pieces shown in fuselage side view securely in place around gear. The top of main landing gear strut should be flush with top longeron and at right angles to sides. Bend 1/16" wire cabane struts, place front cabane strut directly over front landing gear strut. Wrap the two wires together with soft copper wire and solder. Cement 1/16" x 1/8" x 6" at top of both cabane struts; when dry place them in slots in wing center section. Check wing for zero incidence; it must be at right angles to fuselage. Make any adjustments by slight bending of cabane wires. Add notched piece of 3/16" sq. across fuselage under rear cabane struts, wrap with strong thread and cement. With wing pinned in position, bend and install diagonal cabane struts. The fuselage is now a box with landing gear and cabane struts firmly attached.
Bend and drill engine mount; drill tin can stock slightly larger than flat part of engine mount to match mounting holes. Solder four #6-32 nuts in position on tin and attach firmly to back of former F-1. Assemble engine mount and former F-1 and screw in position with #6-32 screws; when all is in alignment remove screws, coat former F-2 with cement and reassemble. Using "Perfect" #10 or similar tank solder extensions of 1/8" brass tube on all outlets, place tank in position. Shim tank with scrap balsa until it is level, cement in position.
Flight shot by Howard Levy during E.A.A. "Fly-In" at Rockford last summer.
Cut and form tail surfaces from smooth warp-free 1/8" sheet. The elevators are joined by a "V" shaped piece of 1/16" wire forced into the" elevators; a "Perfect" #258 hinge is wrapped around this wire and pressed into center of stab. Install other two sets of hinges, check for free movement. Bend push rod; position tail assembly so it is level with bellcrank in position shown. When stab is cemented in position formers F-5 through F-8 and 1/16 x 1/8 turtleback stringers are added. The vertical fin extends down to top of elevator; it is braced on both sides by soft balsa blocks shaped to fair in with turtleback. The same type hinges are used in rudder to carry out the scale effect but are soldered stiff.
After attaching lead-out wires and making sure that everything inside fuselage is in order, cover front section with 3/32" sheet. Cut nose pieces of cowl from 1/2" sheet, cement it in position by mounting it on temporary blocks attached to firewall. Carve and install cowl cheek pieces. Put strip of masking tape around fuselage at cowl line, fill in area between nose piece and F-1 and area from F-1 to cowl line with scrap balsa. Shape and sand cowl so it is a straight line from nose piece to thickness of the masking tape at cowl line. You will note that F-1 acts as template to keep surface aligned. Split cowl from former F-1, carve out inside. Small blocks of balsa cemented to firewall will position cowl while simple hooks and rubber bands run thru the cheek piece will hold it snug. The engine is started inside closed cowl by attaching short lengths of wire to glow plug and ground and running them out cowl cheek piece on right side. Alligator clips on battery leads will speed starting procedure.
Position lower wings by slotting fuselage bottom in proper location to take two 1/8" x 1/4" spars; locate bottom wings at zero incidence and with 1" dihedral at tips. Cut two interplane strut assemblies from cardboard, fit in position by marks made on wing spars. On the upper wings lay 1/8" x 1/4" balsa on each side of strut; cock them to correct angle so they lay flat against top of strut. The bottom strut sockets are installed the same way but use 3/32" sheet wing ribs that are cut oversized and chopped off at the front spar. Check alignment from every angle; remove interplane struts to sand tops of lower wing flush with rest of wing. Unless your work is exceedingly accurate there will be a slight difference in the cardboard struts and the ones shown on the drawing. Use cardboard strut as templates and cut each strut from one piece of 1/16" plywood. Cover each side with 1/4" strips of 1/32" sheet, sand to airfoil shape. Lay struts aside, do not install until after wings are covered and doped.
The original model was covered with Silkspan which was given two coats of clear butyrate and four coats of pigmented butyrate. The colors of the Smith aircraft are '56 Ford Yellow, Stearman Red trim and gloss black lettering.
After the first two coats of dope, lower wings may be cemented in position and finished along with fuselage. The top wing is completely finished, then slot cut in covering for interplane struts and cabane structure. Lower wing covering is slotted for interplane struts and they are cemented in place. Lay top wing in position and rig airplane with 1/2A control line wire. If you installed 1/16" O.D. aluminum tubes in fuselage you can run flying wires from top of one strut thru fuselage to top of other. With all rigging in place top wing may be removed, slots filled with cement and reassembled.
Weighing in at 3.5-lbs model is a little on the hot side with a good .29 swinging a 10"-6" prop. The bipe could be covered with silk and more detail added and still perform well on a .29 but for the wild ones a .35 powered version with a symmetrical airfoil and a heavier finish should be quite a handful. One word of caution, if the lifting wing is used, don't forget they are lifting wings - be prepared for a sharp climb from take off. If you are expecting the climb-out everything is fine but if it comes as a surprise the results could be disastrous. Once in the air, the model is sensitive but not tricky; it will groove if you hold just a little nose-down to counteract the lifting section.
Control Line Smith Miniplane Plans
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Posted April 8, 2017