Andreasson BA-7 (oz12391)

About this Plan

Andreasson BA-7. Radio control scale model.

Quote: "America's Newest, Most Exciting Home-Bilt. Andreasson BA-7, by Bob Blakie.

The scale modeler is always on the lookout for new airplane designs that can be scaled down to produce efficient, good looking models. A new home-built, the BA-7, has the distinctive appearance, proper proportions and crisp lines that interest the scale model fan. Designed by Bjorn Andreasson, internationally known aeronautical engineer, the BA-7 is an all-metal, two-place, sport plane of simplified construction and excellent performance.

Our .15 powered radio control version inherits the simple structure and desirable flight characteristics of the full size prototype. Landing gear placement on the model is just right for fully controlled landings and take-offs. In the air the ship responds quickly and smoothly and its stall recovery is a joy to behold. The fuselage is roomy and accessible enough to handle any combination of radio gear the builder may choose.

The model could easily be built from the drawings alone, but there are always a few comments and hints that even the most experienced model-er should read and heed. Construction should begin with the wings. The sim-ple double spar construction presents no problems but does call for a little extra care in the installation of the 1/16 plywood tongue which secures the wing to the fuselage. It is wise to cut the slot in rib R-5 and use this slot as a template for cutting the slots in all the slotted ribs. Proper alignment of the wing tongues is very important as they control the incidence angle of the wing panels. The 1/16 sheet balsa covering shown is used on the top surface of the wing only and should be cemented in place after the wings are completely done. The nut for the outer strut connection should be firmly anchored to the small square of plywood before it is installed flush with the bottom of wing panels. Select soft, light balsa for the tips and cement them in place after they are roughly cut to shape, final shaping to a symmetrical rounded shape is the last step in the construction of the wings.

The plywood and balsa sandwich that is used, to anchor the wing to the fuselage should be constructed next. With the top layer of plywood removed, block up the wing joiner with some scrap pieces of 3/16 sheet and place it on a smooth flat surface. The wing panels are then inserted in their respective positions and checked for fit and 1 in forward sweep. If any corrections are required to obtain the correct forward sweep, sand the slanted edges of the joiner and when all is as it should be, cement the top layer of plywood to the sandwich and set it aside.

The stabilizer should be next in the order of building. It is built much the same as the wing except the 1/16 sheet balsa covering shown is used on the bottom and the top surfaces. The stab should be covered and doped at this time.

The fuselage is built by cementing up the nose section of the firewall, formers F-1, F-2, F-3; the 1/16 ply-wood doublers and the engine bearers into one unit. The lower piece of 3/32 x 3 sheet balsa siding should be cemented in place with the top edge exactly in line with the top of the plywood doubler, this establishes a workable center line. With the lower side pieces cemented in place the tail plug and all the formers should be cemented in and checked for align-ment. The cutout for the stabilizer should be made and with the stab in position; check for zero incidence and lateral alignment. Because of the small size of the stab it can be safely ce-mented in at this time. Before adding the rest of the fuselage sheeting the landing gear should be mounted with 'J' bolts and the escapement and its components installed and tested. The upper sheets of 3/32 x 3 sheet balsa are then cemented in position and the completed wing joiner box installed.

Before proceeding any further with the fuselage sheeting place the wings in position and check the forward sweep with the centerline of the fuse-lage. Install the wing struts and adjust the outer fittings until 1-1/4 in dihedral is obtained in each wing. A #4-40 screw is used to attach the struts to the wing and the fuselage end is placed straddling the main landing gear and bound together with rubber bands. If everything checks okay sheet cover the remainder of the fuse-lage. The rounded areas of the fuse-lage are planked with Berkeley 1/8 x 1/4 rounded edge planking and sanded to a smooth contour.

The nose cowling may be built up with planking and 1/4 in sheet as shown or it can be carved from a block. The carved cowl is lighter but the built up version is much more durable. The plastic canopy is made from a block balsa form that is carved in place on the fuselage. The shaped block is carefully sanded and given several coats of sealer and dope and a sheet of heated plastic drawn down tight all around it. We heat the plastic to about 400-F in the family oven for about 15 minutes; if it doesn't form exactly right the first time we put it back in the oven for another 15 minutes and try it again. Trim the plastic and cement a 1/4 in wide strip of plastic to the inside edges of the canopy as a reinforcement. Weldwood contact cement is ideal for this purpose. The canopy is retained on the model by plastic strips cemented to the fuselage at the front and sides of the cockpit area and by drilled dowels and a removable piano wire pin at the rear.

A simple 1-1/4 sq x 2 in fuel tank was used on the original model but there is plenty of room for a pressure tank if the area between the plywood engine bearers is cut out and the tank extended back between the bearers. Engine offset is easily obtained by bending the aluminum engine mount; 3° right and 2° down were found to be correct on the original.

The model is covered with nylon or silk for best results and given at least half a dozen coats of butyrate dope. The color scheme is a deep yel-low with dark blue numbers and wing tips.

Original model used a CG RT-1 single channel tone receiver with quick blip exhaust engine speed control. If a Bramco throttle is used some modifications will have to be made to the cowl. The original model (now flying in Honolulu) is to be fitted with a Marcy twin-simul for rudder, elevator and full off-on throttle control. "

Andreasson, American Modeler Annual, 1960.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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