I recently built a new set of nine-foot heavy lift wings for my Senior Telemaster that I use with a 32cc Ryobi gasser for glider towing duties. I wanted to incorporate fowler flaps in the wing construction to help slow the plane down during steep descents from altitude and to help with landing this 18 pound airplane. I was unable to find a suitable commercial hinge that was large enough for this wing so I built my own. I did not originate this idea, but rather copied it from the Internet.
I used Du-Bro 601 nylon control horns bolted together to form a hinge as shown in the photos. I then used a small 90 deg. control horn connected to the flap servo to operate the flap. Be careful to get a small control horn and note that the servo direction becomes opposite since a push towards the flap lowers and extends the flaps.
The effects in flight are quite pronounced
and it was definitely worth the effort to include
fowler flaps into the wing construction. I hope this tip helps
if you need to build flaps in your next airplane!