Avia BH-9 L_BONG 1/72 KP

In 1924, the Avia factory produced a special aircraft with serial number B.9.11, designed for record-breaking flights. It was built from the beginning as a single-seater with enlarged fuel and oil tanks. Their size was adjusted over time, meaning the aircraft was essentially in a state of constant modification.
Some of the record-breaking flights included:

• A long-distance flight of 1,200 km in 1924
• A flight from Prague to London in 1925
• A nonstop Prague – Paris – Prague flight of 1,300 km in 1926

Later, the aircraft was converted into a standard two-seater, used at the aviation school in Cheb, and then transferred for civilian use in Pardubice. Compared to the standard BH-9, this aircraft had extended wings, differently mounted wing struts, and a reinforced landing gear.

The basis of my model is a kit from Kovozávody Prostějov, which offers a version for the L-BONG registration. This is the version from the Prague – Paris – Prague record flight that I wanted to build.

The model requires several modifications, so I will describe at least the basic ones. The good news is that only one cockpit (the rear one) is required for the build. From the kit, the bulkheads, seat, and part of the floor could be used. To create more space for depicting the internal structure and equipment, I thinned the fuselage sides by almost 1 mm on each side. A plywood trim needs to be added to the upper part of the cockpit.

The fuselage must be extended by 1.5 mm at the rear to allow the tailplane to fit precisely; otherwise, the slot for it would need to be deepened. The rudder requires sharpening of its upper front corner.

After returning from the Coppa d’Italia competition, L-BONG received extended wings by two sections. I cut off the last section and added a 9 mm extension.

The ailerons also need to be extended to reach all the way to the wing struts. I mounted the wings to the fuselage using hypodermic needles, so that I could leave a gap between the fuselage and the wing while maintaining a strong connection.

The inserted wing section lost its ports during sanding, so I recreated them using 0.4 mm tape. The wheels have the correct diameter, but their discs are too flat. The outer side has a slight cone shape (though too small), while the inner side has none. I cut the cones for both sides from a 0.2 mm plate and glued them onto the wheels. The landing gear axle is made new with a hypodermic needle.

The engine from the kit is unusable. However, nowadays, there are two replacement options: a 3D-printed engine from MH Model and a cast engine from Radial Engines and Wheels. Each has its pros and cons, but both are highly detailed. This specific aircraft had a streamlined engine cowling, which is not included in the kit. It is up to each builder to solve this issue. I made a mold and formed it from a 0.3 mm plate. The upper front fuselage requires additional details, such as fuel and oil tank caps and ventilation. The fuel caps have tubes leading from the exhausts, of which the model has two, positioned on the front wing struts. A Pitot tube is added to the left strut.

After assembly and in the surf, the model looks like this:

This was a military aircraft that received civilian markings for record-breaking flights.
For this reason, the kit includes two decal sheets – one with military registration (national insignia and regiment markings) and one with civilian markings. The military decals are of good quality and appropriately thick, adhering well to the surface. The civilian decals should ideally be sealed with an extra layer of varnish, as they are very thin, tend to curl, and tear easily.
The size of the “L-BONG” letters for the wings was designed based on the upper surface, which is longer due to curvature. They fit well on the top but are very tight on the underside. The “ONG” letters need to be spaced further apart due to the wing extension, and the underline must also be adjusted.
The wing struts should be attached only after applying the decals – the decals align with the attachment points and positioning them with the struts in place would be nearly impossible.

The colours used are Tamiya and Gunze C paints, with Tamiya varnishes.
Painted by brush.