Eolo Retro (oz16329)

About this Plan

Eolo Retro. Radio control glider model. Wingspan 3m.

Quote (google-translated): "The look is decidedly vintage, but the project dates back no more than two years ago. A large RC glider with vintage lines for fun building and then relaxing flight on flat land or slopes. Eolo Retro, by Vincent Besancon.

You undoubtedly remember the Elektro Retro (oz16073) that large electric vintage model presented with its design in MODELLISMO 122. I wanted to build a towed glider in the same style. The Eolo Retro is therefore a rustic glider with a vintage look that can be towed with a simple tow bar or launched fearlessly on a slope in any conditions. A lightly loaded glider, capable of evening flight during restitution.

The wings are deliberately attached to the fuselage with large 200 mm rubber bands so they can be released or rotated without causing breakage. With the dihedral specified in the drawing, the ailerons can be removed if desired, further simplifying construction and reducing the weight of the model. A second steel bayonet with less dihedral allows the ailerons to be appreciated. The fuselage cross-section is triangular for a touch of originality, and its rounded shape recalls that of the Elektro Retro. The goal was to remain below 30 g/dm2.

The 3 m span allows for easy transport and quick assembly, and a generous 320 mm chord provides 90 dm2 of surface area, which leaves a build margin of up to 2700 g, easily achieved. I won't go into too much detail about the construction, as it's a classic, but you can refer to what I wrote for the Elektro Retro.

The glider was built in less than a month, including the design and cutting. The airfoil used is the good old Clark Y, easy to make and thick enough to create a sturdy wing. The wing has no D-Box, in keeping with the vintage spirit. The wing and stabilizer planform are elliptical, without adding too much complexity to the construction. The ailerons are protruding to add a touch of originality. The frame is made of Diacov, a product I prefer for its transparency and, above all, its solidity. The painting only concerns the outer edges of the various surfaces.

The flight On June 15th, we went to Pic du Vissou and arrived around 6 pm, as we usually do at this time of year. It was truly pleasant to stay until late at night on top of this slope with temperatures approaching 30°C. Sea breezes die down around 7:00 PM and until sunset, warm air rises from the valley, and flying with lightweight models has something magical about it. I built this glider specifically to take advantage of the evening return conditions, when flying with vintage glider replicas would be too risky. For the first flight, not wanting to take any risks, I launch while there's still about 20 km/h of breeze.

The Eolo Retro is climbing, and to move forward I have to dive hard. After considerable acceleration, the wings almost flutter, so I decide to slow down. I suspected these conditions would be too severe to fly with such a lightly loaded model. Finally, 8:00 PM arrives, and then the flight is completely different. The glider glides gently through the air, oscillating at the slightest current. The ailerons are very ineffective, which is normal given the dihedral, and I could have done without them.

The sensitivity on the pitch axis is excessive, so I significantly reduce the travel, especially when diving. The glider dives too much when I push on the stick, a sign that the centering is too far back. To be safe, I prefer to add 100 g of lead and place a 3 mm shim behind the stabilizer to slightly increase the longitudinal dihedral. The ailerons immediately become more effective, the flight is more precise, but it departs from the more relaxed vintage style.

It's certainly not a model that can compete with an F3J or an F3K; you can feel the drag from that thick profile and such a large fuselage, but it remains a pleasant glider to fly, always ready to get out of difficult situations to test a slope or to fly under tow on the plains or with a catapult. The considerable wing area easily supports the overload of a small camera or a Go-Pro, without any impact on the flight.

Warning: The prototype was built with red cedar main spars for the lower surface and balsa for the upper surface. This was definitely a mistake I made simply because I wanted to save some weight, but while flying on a slope in very strong conditions I broke one of the main spars..."

Direct submission to Outerzone.

Update 18/10/2025: Added CAD version of this plan (full scale) thanks to KurtWolfram.

Quote: "Hi - long time no see. Attached are two cad drawings for Eolo Retro - Wing and Fuse. Scaled up X 2 - there's some text in Italian that explains the size reduction was due to publication restraints. Didn't change anything - just moved what was there into layers for organization and visibility. Hope somebody somewhere can use these.
KW"

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