Fulmen (oz14707)

About this Plan

Fulmen (Sokol S-496-D Fulmen). Free flight power model. Wingspan 1.35 m.

Note this is not a full size plan.

Direct submission to Outerzone.

Quote (translated): "Contest powered model plane for Atom 1.8 ccm engine. Sokol-496-D 'Fulmen' (1949) by Bronislav Sokolicek.

The model earned the name from its fast powered flight, when it was nicknamed as 'Lightning' by my friends, who witnessed maiden flights. Lightning translates to Fulmen in Latin, hence the name. Even such things, can be sins of youth. I especially like to remember the times, when I flew models with my friend Mirek Pospisil at places, which have been taken by concrete blocks of flats over the time, creating a human anthill. I remember how we used to start up and tune the engines together - Atom 1.8 ccm, simultaneous take offs and laying in the grass next to each other, looking up and silently watching our models circling, gaining height. We never suffered a neck pain and even today, more than long sixty years since, I can still remember the smell of a blossoming meadow. The only thing I regret today is the fact that I cannot attend flying sessions with the oldtimers, but I still like to remember those days, spent with aeroplanes, either real ones, or models.

Fuselage: The model is built from domestic material (spruce, ply, etc.). First, two sides are built up from spruce longerons 3x3 mm, which are then connected by cross braces, forming a complete fuselage. Engine and landing gear are attached to fuselage former, made from 5 mm ply. Pylon has a support "backbone" from 2 mm ply, with both sides covered by 0.8 mm ply, top side is formed from 0.8 mm ply. "Tailwheel" is made from 1 mm steel rod.

Rudder: Built up from spruce 2x2 mm and 2x5 mm, flat plate airfoil with trimming plate attached.

Horizontal stabilizer: Symmetrical airfoil NACA 0008. Ribs are made from 0.8 mm veneer, plated from both sides with light paper. Leading edge is made from spruce 2x4 mm, main spar 2x4 mm and trailing edge 2x8 mm, thinned to 2x4 mm at both ends. Wingtips are made from cork.

Note: when the replica was built, the airfoil was changed to flat plate from spruce 3x3 mm, 3x5 mm and 3x8 mm.

Wing: Built as two pieces, connected by two steel rods 3 mm and 2 mm in diameter. Wing is attached to the fuselage with rubber bands, held by 3 mm bamboo pins, glued into the pylon. The airfoil is NACA 6409, center ribs are made from 1.5 mm ply, all other ribs are from 0.8 mm ply, with lightening holes. Leading edge is from spruce 4x4 mm, main spar two 2x5 mm above each other and trailing edge 3x12 mm, thinned to 3x6 mm at both ends, sanded into a wedge. Wingtips are made from cork and dihedral points are reinforced with 2 mm ply inserts.

Covering: The complete model is covered with paper (Diplom), glued with casein, tightened with water spray and finally 3 layers of dope are applied.

Flying:
Center of gravity is located 105 mm from the leading edge of the wing.
Wing incidence +4.5°.
Horizontal stabilizer incidence +1°.
Engine Atom 1.8 ccm (diesel).
Thrust offset - 2.5° down.
Powered flight - right circle, glide - right circle."

Update 29/7/2023: Added (probably better than mine) transcripts in both English and French, thanks to JMP.

Quote: "Hello, Herewith translations of the original article into French and English. I used: https://www.onlineocr.net/ to convert the image to a text file, and https://www.webtran.eu/czech_english_translator/ to translate the text file to English, then also to French. A little editing later the French and English translations were done.
This is quite an attractive model, thank you Tom! Best modelling regards as always,
Jean-Marie Piednoir."

Update 9/6/2026: Added translation, thanks to Jan.

Quote: "Hello Steve, attached is the translation of the original article, I hope it is better than Google translate ;-)
Greetings from the Czech Republic,
Jan"

Supplementary file notes

Planfile includes article.
Transcripts (En, Fr).
Translation (En).

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