Sonoma (oz15527)

About this Plan

Sonoma. Radio control electric powered sailplane. Wingspan 78 in, wing area 533 sq in.

Direct submission to Outerzone.

Quote: "Sonoma - 2 meter electric powered sailplane. In 1998 I designed a electric powered glider called the Wolf. I had some trouble designing the wing ribs at the wing tips because of the fully sheeted Hirth wing plan. Other projects took precedence and I forgot about the model. It was one of my first models designed in CAD.

In 2023 I decided to create a new sport glider, and I remembered the Wolf design. I decided to incorporate the fuselage and wing planform into the new model which I call Sonoma. Recent experience showed that top and bottom sheeting is not required for a 2-meter light weight electric powered sailplane. This made the wing design much easier since I didn’t need to worry about top and bottom sheeting. I used the stab and rudder from the Electra-Dyne. It is easy to combine elements using CAD.

The fuselage is a very traditional slab-sided affair. The one difference from most models is the forward bottom hatch. I find that this is very easy to build and works great. It provides easy access to the motor and the battery. It also allows the fuselage top to be carved and sanded to a nice, streamlined shape.

The wing, stab and rudder are simple assemblies. I built the laminated wing spar over the plan as the first step in wing construction. It is pretty easy to add the trailing edges, ribs and leading edges.

When the basic wing structure is completed, I fit it to the fuselage. I use a couple of long rubber band around the fuselage to hold the wing in position while the wing hold down dowel is epoxied in place and the wing bolt threaded hole is drilled. The last step in wing construction is adding the center section top sheeting.

The model is covered in white and fluorescent red transparent Ultracote. This color combination is the most visible to me.

The wing uses a hybrid flat bottom airfoil. Believe it or not, it was developed from the undercambered airfoil used on the 1949 Wally Simmers Dynamo. With this airfoil the model has a nice flat glide and a seed range that allows flying in windy weather conditions.

The first version was built with a sport wing without spoilers. It proved to be great at thermaling. I decided to redesign the wing with spoilers to make it competitive in my club’s ALES contests. A second wing was built and fitted to the fuselage.

The Sonoma Is powered by a Cobra BA 2217-20 by Innov8tivedesigns.com and an Graupner 10x8 folding prop. The model flies with a 3s 800 mah Lipo pack.

The Sonoma uses a CAM altitude limiter. Typical launches include full power with some down for the first 20 seconds. This is nearly straight up. I reduce power for the next 10 seconds until the motor stops to ease into the glide.

You can fly this model with a 2S pack with a more conventional climb.

Specifications:
• WING SPAN: 78"
• LENGTH: 35.6"
• WING AREA: 533 sq. in.
• WEIGH RTF: 21 oz. with 3 cell 980 mah Lipo
• WING LOADING: 5.94 oz./ sq. ft.

Jim Zare"

Supplementary file notes

Build notes.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction