Sicroly

A young Hanno Prettner posing with his Sicroly, a truly elegant classic pattern model

1. Some background

The Sicroly is an RC1 pattern model airplane designed around 1970 by Hans and Hanno Prettner. This was way before Hanno started accumulating his Word Champion title successes, so it is not as well known as his later models. The Sicroly is the predecessor of the Super Sicroly with which Hanno participated at the 1971 and 1973 World Championships. His first win was with the well known Curare in 1977. Later he would win more titles: 1981 with Magic, 1983 with Calypso, 1985 with Supra Fly, both 1987 and 1989 with Supra Star and finally in 1993 with Mystic 60. Hanno Prettner has inspired generations of RC builders and pilots and still does today. His more popular designs are shown below.

Super Sicroly (1971-1973), Curare (1975-1977), Magic (1981) and Calypso (1983)

Supra Fly (1985), Supra Star with Ayrton Senna (1987-1989) and Mystic 60 (1993)

The Sicroly is indeed much less known. I first came accross a photo of the Sicroly in an advert for a kit of Radu Balea's remake model which has a slightly altered shape (in the first place to facilitate fitting retracts). The box lid showed a picture of Hanno's original and that stirred my curiosity. A search on the internet didn't reveal a lot, so I contacted both Radu and Hanno to know if any more photographs or drawings did exist. Both gentlemen kindly sent me some information on the background of the model, but unfortunately, no drawings had been preserved. I did learn however that the Sicroly was the follow up design of the Acroly and Wicroly from the second half of the sixties.

Hans and Hanno with the original Acroly

Hanno with the Wicroly and some early trophies (circa 1967)

2. Sicroly project

Below are the only two photographs I have found of the Sicroly. The elegancy of this model struck me from the first time I saw it. I liked the looks so much that I decided to add the Sicroly to my list of projects (the Topp Comet II is awaiting further building). I could of course have bought the beautiful high quality kit manufactured by Radu Balea, but in my opinion, his interpretation compromises somewhat in elegancy and doesn't fully capture that elegant look. That's why I decided to make my own version (which in all honesty won't be 100% authentic either).

Hanno preparing the Sicroly for flight (still in initial finish)

Hanno posing with the Sicroly (now with some added graphics on wing and fuselage)

Sicroly kit manufactured by Radu Balea

Sicroly model as built from the Radu Balea kit

So I decided to redesign the model to make a one off model of what I think is a more authentic replica of the over fifty years old design by Hans and Hanno Prettner. Below is my attempt at this in the form of a 2 view drawing.

2 view drawing with my interpration of the Sicroly

At time of writing (February 2026), the construction drawings have well progressed (see sample below). The drawings of all the balsa and plywood parts have been converted in usable files for CNC cutting which is now also complete (see phots below). It's now a matter of assemling the kit I made for myself. I want to emphasize that I do not intend to commercialize the kit. It is a pure retro fun project as a tribute to Hanno Prettner. As soon as there is more progress on the project, this page will be updated.

drawings almost done (only plan #1 is shown: fuselage and stab)

first balsa parts being CNC routed (wing ribs)

all wood parts are now CNC cut, so construction work will be following shortly

to be continued...

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