Buhl Pup (oz6736)

About this Plan

Buhl Pup. Radio control stand-off scale model. OS Max .25 shown.

Quote: "Al Wolsky's Buhl Pup.

The Buhl Bull Pup was a small light sport plane of the 1930-1932 era. Not more than a hundred were manu-factured when the company fell victim to the Depression. It was powered by a 3 cylinder Szekely engine of 45 HP. This Pup model could be called Stand-Off Scale since no attempt was made to duplicate the real Pup in every detail. Power the model with engines in the .25 to .29 size range.

Wing: Cut the tip outlines from 1/4 in" sheet and glue the pieces together over the plan. Cut (2) 1-3/4 x 26 in from 1/16 sheet (need (2) 1-7/8 x 26 x 1/16 for top leading edge) and (4) 1 x 25 from 1/16 sheet. Lay (1) 1 x 25 x 1/16 and (1) 1/16 x 1-3/4 x 26 over the plan. Mark the center lines of each rib on the sheet. Cut the 1/4 x 1/16 capstrips and glue the lower ones in place. Glue the tip outline in position. Note that the latter goes over the lower 1/16 pieces. Glue in the lower 1/4 in square spar. Now glue all ribs in place.

The top spar is next. Taper and blend in the tip outline where it meets at the trailing edge. Glue in place the 1/4 x 1/4 leading edge and the 1/16 x 1 in trailing edge as well as the 1-7/8 x 1/16 leading edge. Now glue in the top capstrips. Oil the plan and use the reverse side to build the other half. When both panels are finished, cut and glue dihedral braces in place and complete the center section.

Empennage: The tail surfaces are constructed of 1/4 sheet and 1/4 square balsa strips. Note the plywood insert at the center of the elevator.

Fuselage: From the top view construct a crutch of 1/4 square balsa. To this add the formers as noted on the plans. Form the main landing gear from 1/8 wire and mount it in place on the No. 2 ply former. At this time glue the lower keel 1/4 sheet strip in place. Now take (2) 1/8 x 6 sheets and glue in place along the crutch. When this is dry wet boils sheets and bring down to and glue to the keel, holding in place with pins, masking tape, etc.

Cut out firewall No. 1 and the 1/4 plywood nose keel and epoxy these in place. Tack glue 2 - 2 x 6 x 5 in blocks in the nose area and shape and sand to shape. Fit the wing in place and add the formers.

Plank the top back to the tail block with 1/8 x 1/4 strips. Remove the two nose blocks and hollow out, then glue back in place. Fill in any cracks in the planking with filler and sand the entire model gradually working down to fine sandpaper.

Give all wood areas two coats of sanding sealer, sanding between coats then cover with your favorite material. Mine was covered with Silray and finished with dope.

The wings were painted yellow and the fuselage red. Add scale details as desired. Adding wing walks, a windshield, and two dummy cylinders 120 degrees from the glow engine would add to the appearance. When mounting the gear cut pieces of plastic sheet and insert between the gear and the fuselage to protect the finish.

Flying: With the gear set up to track straight, the model should lift off with no problem. One thing to remember though is that both the rudder and elevator are large surfaces and the model reacts to the slightest stick movement, so limit that movement by using long horns, etc, and take it easy on initial stick movements.

The Pup pictured is the author's second prototype and both present no problems whatsoever. Any three channel digital system will handle the Pup. As mentioned, two models have been built and have been powered by the new Fox .25 RC engine. This engine has ample power for the Bull Pup. Good Flying!"

Supplementary file notes

Article, thanks to JHatton.

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