Jiro Sugimoto is one of the true master craftsmen of Free Flight scale. His models have been featured in the famous (but now defunct) Model Builder magazine, several of Bill Hannan’s “Modellers and Models” series as well as several internet sites (do a Google search for Jiro’s name and you can see lots of examples of his craftsmanship). So when I had an e-mail from Jiro saying he was building my plan of the Amethyst Falcon, I was thrilled!

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The full-scale Falcon is a single-place ultralight homebuilt, designed for low-cost fun aerobatics. As far as I’m aware, only one has been constructed, in Queensland, Australia. It’s constructed from welded tubular steel and covered with fabric. The cowling and wing-tips are fiberglass. The unique notched centre-section of the upper wing (with the inner trailing edges curling down to meet the fuselage) is a signature design trait of the Falcon’s designer, Bill Whitney.

The simplicity of the Falcon’s layout (with both wings attached to the fuselage and only a single inter-plane strut struck me as a great candidate for my first rubber-scale biplane, so I got to work with my CAD program and drafted a plan for Peanut scale model, as well as a larger 22” span version.

Working from a downloaded copy of my Peanut scale plan, Jiro initially asked a few questions regarding scale details and requested some more pictures of the full-size plane. I updated the plan to add the details and make it clearer. As he progressed with construction he forwarded several uncovered construction shots, which are included here. Not only is Jiro a magnificent builder, he is also a great photographer!

After several e-mail exchanges, I finally received the news that Jiro’s Falcon was in the air:

“I already finished Amethyst Falcon and took her to Ichinomiya gym for first flight. Put some weights into a nose socket and checked CG. She turned right with just circle. I did not check weigh of her and turns of rubber now, so I send a report again.”

In a departure from the plan, Jiro constructed the lower wings in 2 pieces and glued them to the sides of the fuselage. The plan shows the lower wing in 1 piece, then glued under the fuselage. It’s a minor difference, and most experienced builders will follow their preferences.

Jiro always builds a lot of lightness into his models, and he meticulously weighs the components. Here’s what is uncovered framework weighed:

Wings (both upper & lower): 1.5g
Tail plane, fin & rudder: 0.3g
Fuselage: 1.9g
Tyres: 0.4g
Un-covered total: 4.1g

Based on the weights measured at the pre-covered stage, Jiro predicted a final weight of his Amethyst of 8.5 to 9.5 grams. This was a good estimate, since the final weight of the model (including rubber) turned out to be 10.2 grams!

One of Jiro’s secrets is to use light weight Gampi tissue and airbrush his models with very light coats of paint. To achieve the silver doped finish, Jiro mixed 50% silver + 45% white + 5% black acrylic paint.

Jiro took 3rd place in the “Modern” class at the Nagoya Nuts peanut scale contest (held every 2 years) in August with his Falcon. 32 club members entered 76 models (in 6 different classes, both indoor and outdoor) at Ichinomiya Hall and Shonai Park in Nagoya. The Falcon scored 91.5 scale points and 76 flight points (with a longest flight of 59 seconds).

-by Derek Buckmaster

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