THE COLVER SKYSAIL
My son Matt and his friend Ernest Feher built the bamboo and plastic glider (Richard Miller’s Bamboo Bomber) that was at the 1st Otto meet, May 23, 1971. After the meet I started designing my Skysail with inspiration from Richard Miller’s Conduit Condor. After testing a scale model (which I still have), actual construction on the Skysail started on November 5, 1971 and the wing was taken to the field for the first time on January 22 of 1972. I sold many copies of plans for a model of the Skysail but never for the full size version, due to liability worries. If someone scaled it up that was their choice.
After I quit flying the Skysail it was donated to the San Diego Aerospace Museum where it burned up in the fire that destroyed the museum.
THE COLVER HANG GLIDING VARIOMETER
The first aircraft instrument manufactured specifically for hang gliders.
A variometer is a more sensitive form of the rate of climb / decent instrument used on most aircraft. It is used for gliding aircraft to detect when rising air currents are entered and lets the pilot maneuver the glider to stay in the lift and gain altitude or to avoid sinking air to stay up longer.
Various types of variometers have been in use since the days when balloons were man’s only way to “leave the surly bonds of earth”. Most have used some method of detecting when air was entering or leaving a container. The very earliest types used “sight tubes” where bubbles could be observed as air went in or out of an insulated bottle.
Now “fast forward” to the new sport of modern hang gliding. In early 1970’s hang glider pilots were transitioning from just launching of hills or mountains and landing at the bottom to attempting to climb in thermals and stay up longer or even land some considerable distance from their launch point. They started adapting the variometers used in sailplanes with brands like Cambridge Instruments or Ball Instruments.
In the fall of 1973, to the best of my knowledge, the first ever commercially sponsored hang gliding competition was held at the Sylmar CA hang gliding site. It was sponsored by “Annie Green Springs” a maker of soda pop style white wine being marketed to the younger crowed. This was an invitational competition and my son Matt was invited to compete. He was not experienced in thermal flying and I knew he would be up against those using the sailplane variometers. I wanted to build him a vario that would beat the competition’s instruments. I had been experimenting with making variometers for RC model sailplanes using thermistors as “hot wire anemometers” to detect air moving in or out of a closed container. However, I didn’t like the delay time that the thermal mass of these devices introduced even though they were very tiny.
A “hot wire anemometer” detects the resistance change in a device heated by current passing through it when an air current cools it. I decided to use the filaments of tiny low voltage incandescent light bulbs with their glass enclosures removed. I built a sensor using two filaments positioned next to each other and placed in the air stream of air entering or leaving an insulated plastic bottle. Air flowing one way would cool the filament close to it more than the one directly behind it and my circuit would measure the difference in resistance between the two. Two tiny nozzles directed the air against one filament or the other depending on flow direction in or out of the bottle.
So, to give Matt an edge in the competition, I kluged together a variometer based on two tiny lamp filaments. I “bread boarded” my detector circuit and built a sensor. This also used a transistorized pocket AM radio for the amplifier and speaker it contained. This kluge consisted of two packages, which needed to be duct taped to his control bar, with wires running between them,.
I don’t remember how Matt did in the contest, he was up against the best that hang gliding had to offer at that point in time. What I do remember is how the other competitors recognized the superiority of my vario compared to what was being used. Other pilots begged me to sell them this kluge right off my son’s control bar. Fortunately, I had the good sense to not do that. I loaned it to Taras Kiceniuk that afternoon to fly his Icarus V. He eventually used the vario to find sink so he could get down after a long flight had tired him out.
After the meet I started to work on making a producible version of the vario. Since I was holding down a full time engineering job this meant spending many late night hours. One irony was that I had trouble duplicating that first hot wire sensor until I figured out what was different in my subsequent versions.
The rest, as they say, “is history”. I produced the variometers under the one man company name of “Colver Soaring Instruments” selling them wholesale to various hang glider manufacturers and dealerships usually in lots of five. I didn’t want to sell in bigger lots because I wouldn’t be able to satisfy the demand. After a number of years I turned the whole product over to Wills Wing who had become the prime distributer for the instrument. I still continued to make the hot wire sensors, for Wills Wing, because it took a watch makers precision and care to build.
The Colver Vario’s internal components were also used inside the “Chad” hang glider instrument dash board.
I estimate that over the product lifetime about 5,000 units were sold. Still to this day I occasionally hear stories of epic flights made possible by my varios. The variometers on the market today have far surpassed my product in smaller size, weight, and features, but absolutely none have the sensitivity and fast response time of the “Colver vario”. I challenge any of them to respond to the pressure drop in a room when a toilet is flushed and the water goes down the hole. Or to react to the pressure changes when someone bounces up and down on a wooden floored room. If the “Colver” was moved up or down an inch or two it would indicate the rate of change in atmospheric pressure, due to that altitude change.