Friday, December 2, 2016

Building the Retro Gnome FF Hi-start Glider

How I decided to build the Retro Gnome hi-start free flight glider has a rather round about history. As my interest in free flight models has increased so has my desire to experiment with different aspects of free flight, in this case it was dethermalizers (DT).  My start with DT’s was with the viscous type which although lightweight, suffers from accuracy issues especially as the temperature changes. I had used the plastic clock windup mechanism that I purchased from Hank Nystrom in water rockets to deploy the parachute and it had worked well. Normally this mechanism runs through rather fast but it is possible to slow it down by putting very small weights on part of the mechanism that vibrate quickly and slow down the unwinding. Some people build their timers like this but I purchased the Micro DT from Hank.

Retro Gnome Farmework

Small Weights on Plastic Clock

To test out the Micro DT I decided I would install it in the free flight hi-start glider that Hank had shown on his website with the timer, the Retro Gnome sold by Retro RC.  I met Mark Freeland (Retro RC) at the 2016 Nats and he showed me a sample of the glider. 

Kit Components

Building the kit is relatively easy as it is laser-cut and there is an instruction manual, in some places the plans and pictures are a little small so I used a magnifying  glass, not going to say I am getting old. The wing seemed like it was not very rigid before covering so I used a technique Dohrman Crawford uses of using some reinforcing tissue strips over the structure before covering with tissue. The finished wing feels plenty rigid.

Wing Structure Before Joining

Fuselage and Stab

This glider uses a simple autorudder that  is pulled to the right by a small rubber band and to the left by a monofilament  line with a pin holding the tension until the pin is pulled out as the tow hook releases and the tow line pulls the pin out. As this is a hi-start glider a very thin rubber strip and line with a small flag make up the hi-start launching system, I purchased this from Retro RC also.

Kit and Launcher

My hope is to do some glide testing of the Retro Gnome this weekend and take additional pictures but no hi-start launches. The glider must be adjusted so that it goes up on tow straight, when the pin releases it should turn right because of the autorudder.  The design includes adjustment screws for rudder movement, stab incidence change, stab tilt, and a tow hook that can be positioned in multiple  locations.

Almost Complete

Stay tuned for future flight reports.

Bill Kuhl

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  1. I have a very small stick built kit called a Pioneer. I have intended to launch with tow line. Now giving confederation to a light high start. My thought now because I have a course sand and rock field is to use a small bungee cord. The problem is the weight on the line. The lift of the glider may not carry the line up. I have come up with a idea which I have never seen reported in any book. Using a small turn around pulley like used with larger winch launch gliders, I will leave the bungee on the ground coming back toward where I stand to launch. Purpose is the small glider only lifts a light line.

    1. The rubber in the hi-start line is only 1/16" wide so weight probably isn't a problem. My understanding is it goes up very slowly. I did some glide tests and the glide was straight ahead so I think it is ready to go up on the line.