Goat4 Page The Goat4 is my latest monoplane airchair design.   Last update: May 22, 2008

The Goat4 is a home built ultralight sailplane which first flew in March, 2007. It combines the cable braced wing of Goat2 with the nose section and tail of the Goat3, hopefully retaining the best characteristics of the two designs. For those who are interested in some technical details, see Goat Notes. I have posted the Goat4 drawings for Web viewing and as a download (see "drawings" on the BUG home page menu).

 

Goat4 on the truck, ready to travel

Goat4 parts laid out for assembly

This season I'm busy with a new biplane, but last season I was more active in Goat4. I kept my glider at home, loaded it on my truck for transport to the mountain top setup area, and then launched by rolling down the hillside. In the air I first got some altitude by thermalling as high as I could, typically one to three thousand feet above launch, then I went for an air tour of the local country side, using lift where I found it, or I might have followed another glider, or a bird, or a cloud, or something. Eventually I came down to the local landing zone, a small clearing in the brush, where I deployed the drogue chute and landed on the wheel, using the nose skid as a brake if I needed it. After retrieving my truck and trading stories with the other pilots, I took the glider apart, loaded it up on the roof rack, and drove home.

Goat4 launching from a mountain site. The launch slope here is barely two wing spans long, but with a normal afternoon wind it will give me plenty of takeoff airspeed. You can see where the cleared area ends and the bushes begin just under the rudder.

 

Looking down at the launch from Goat4 I''m flying at my local weekend site, looking down from about a thousand feet over the ridge. This is the necessary photo to demonstrate that the Goat4 really is a soaring glider. I rolled off that little hillside clearing (see photo above), from right to left in the photo, then thermalled up to take this picture. The black area is my knee in a flight suit. A paraglider canopy can be seen laid out on the ground on the launch, and two hang gliders are facing downwind in the setup area.

This design seems to be a good airchair for my purposes. Goat4 is essentially the same as Goat1 except that the wing is cable braced instead of strut braced. The cable braced wing is lighter and has no bulky struts to deal with, so it's easier to transport. If I were flying at an air park and could just leave the glider in a hangar or tied down, I'd probably prefer struts since I'd expect them to have less drag and they are quieter in flight (the cables make a lot of wind noise).

Goat4 was created by adapting the Goat2 wings to the Goat3 nose and tail section, and making the king post (those struts above the wing that hold up the landing cables) removable so it could be stowed in the nose section. The Goat2 wings are used mainly because they have a large area (providing a wing loading about the same as a hang glider) and allow me to slow down and stay up in weak, small thermals. In addition, they are light and easy for one person to load onto a vehicle. The Goat1 wings, with attached folding struts, each weighed forty two pounds or more, and in hot, windy conditions, when I was already tired, lifting and handling that heavy wing was too much for me.

The Goat3 items that I liked and wanted to retain were the fixed seat and belts (always in place and not requiring any attention during assembly), the larger aileron torque tube (stiffer for a more solid feel to the ailerons), and the shorter tail boom tube. It also uses a lighter, smaller tire than Goat1, and punch button automotive seat belts.

 

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