Notes from other experimenters-- spoilerons on flex-wing hang gliders

Notes from other experimenters-- spoilerons on flex-wing hang gliders

August 8, 2007 edition
Steve Seibel
www.aeroexperiments.org

Notes from a telephone conversation with Larry Smith, October 2003. Larry is a Colorado pilot.

Larry Smith has put spoilerons on 4 sensors and a few Wills Wing gliders. Larry noted that he showed his spoilerons to John Coyne at a meet in Telluride. A flight in Minnesota, with no gloves, in powerful, widespread lift that he could not escape, provided the original motivation to work out the spoileron system.

The spoilerons were activated by a simple system--a bungee was used to provide a closing force on the spoilers--a pulley was attached inside the wing to a nylon cord which joined the sail at the point where the double surface ended--the 1/8 inch diameter actuating line was simply draped over the top of the keel--the smooth curve with a large radius eliminated the need for a pulley at this point--the actuating line ran down to plastic sliders made from PVC pipe on the base tube.

Larry said that if he built a next-generation design the spoilers would probably operate automatically with the pilot's weight-shift inputs, via a connection to the hang strap.

Deploying the spoilerons increases the amount of effective reflex in the wing which increases the wing's pitch stability.

Larry recalled that John Coyne's spoilerons were larger (in span?)--Larry's were 4 inches (in chord)--Bob Trampenau took an interest in the concept as did Rob Kells but others at Wills Wing were less enthusiastic.

The spoilerons give a totally "coordinated" feel to an entry into a turn, there's no adverse yaw and no real sense of the glider yawing in any particular direction, just a smooth roll in the desired direction. They work fine with the VG on or off and there's no reversal of the roll effect of the spoilerons in any part of the flight envelope. Larry stated the ease of roll control, and the extra glide path control, made flying with the spoilerons a real pleasure.

Photos from Larry Smith of spoilerons of his own design and construction (note that the position of the spoilerons varies from glider to glider). Photos courtesy of Larry Smith. Photo #1, #2, #3, #4.

Notes from a telephone conversation with John Coyne, October 2003. John is a Colorado pilot living in the Denver area.

John used to fly a Fledge, and also has accumulated a lot of time in a Swift. He flies in areas with very strong conditions, and has encountered lift up to 5000 fpm on the 20-second averager in wave. In these strong wave conditions the spoilerons are very useful for boosting the sink rate as well as for roll control. The spoilerons are also great for precision landings.

John said that Terry Reynolds was one of the early pilots to put spoilerons on a flex-wing hang glider--Terry put small spoilerons on a HP.

John put spoilerons on three different Sensors, using a slightly different spoileron design each time.

General notes--the spoilerons were deployed by sliders on the base tube. The gliders could be flown in the normal manner without deploying the spoilerons, or by using the spoilerons for roll control, or by deploying both spoilerons at once to boost the sink rate--an extra 1000 fpm of sink could be created to yield a total still-air sink rate of 2000 fpm--useful for escaping wave or strong glassoff. The roll control was so effective that sometimes John just left the VG full on for entire flights in strong thermally conditions. The higher the airspeed, the more effective the spoilerons. There was no reversal of the roll effect of the spoilerons in any part of the flight envelope--they always rolled the glider in the direction one would expect. Depending on the exact location of the spoilerons on the wing they could have a pitch-up or pitch-down effect--the third glider had the spoilers optimally placed for no pitch effect.

John activated the spoilerons by sliders on the base tube, which are much more comfortable to the pilot's wrists than were the twist-grips used on the old Fledge. The spoilerons were activated by very simple systems involving a pulley at the top of the down tube inside the sail, and a pulley sewn inside the sail near the spoileron.

John's first spoileron design involved spoilerons of 400 square inches each--4" chord by 10" span--made of 60 thousandths inch thick aluminum, shaped to fit the airfoil and lie down flat on the wing. The spoileron ran out to the tip wand and extended inboard to 1" short of the outboard-most curved rib (batten). During the manufacture of the glider, John had the manufacturer sew a dacron hinge under the leading-edge fabric so it protruded aft from the seam between the leading-edge fabric and the rest of the sail. The protruding portion of the dacron hinge fabric was 5" in chord so glue could be spread over the entire spoiler to join it to the hinge, and then the excess inch of hinge material was hot-knifed off. The glue was 3M80.

The far outboard position of these spoilerons created a slight pitch-up moment when deployed. They provided very effective roll control and also greatly boosted the sink rate when both were fully deployed, especially at high speed.

John usually flew the glider in the normal manner without using the spoilerons but if a strong thermal tried to tip the glider out, John would grab the slider on the base bar and deploy a spoileron. In situations where penetration was needed John would launch the glider with the VG full on and use the spoilerons for roll control. John won the '86 nationals in this glider, and flew it with the VG full on for a whole meet at Chelan. May have been a Sensor 510C.

John's second spoileron design had the spoilerons moved inboard by 2 bays. The control horns were blind-riveted in for a smoother finish. Although they were further inboard, they still provided very effective roll control, because they were located at a portion of the wingspan which was generating more lift than the outermost tip portions would be. They were also more effective at boosting the sink rate than were the more outboard spoilerons were on the earlier version.

The '94 USHGA calendar shows a picture of this glider; with a close look one can see the location of the pulley inside the sail, and the actuating cord.

John's third spoileron design, on a Sensor 610F, had the spoilerons located midway between the positions used in the previous 2 designs, i.e. between the two outermost curved battens. These continued to give good roll control, and a good increase in the sink rate when both fully deployed together, and no nose-up or nose-down pitch effect was created. During the manufacture of the sail, John had Bob Trampenau sew in a pulley attached to 550 cord, right next to a rib (batten) so that it wouldn't pull tension on the fabric. The pulley was located inside the sail at the extreme aft part of the double-surface portion of the wing, near the spoileron. A method was devised to avoid problems with the pulley turning over on it's cord as sometimes happened with the earlier designs.

Unlike John's earlier 2 Sensors with spoilerons, the 610F didn't need any high-siding in a thermal with the VG full on, so John would routinely leave the VG full on for entire flights, using the spoilerons for roll control.

Discussion:

The results of my own experiments with aerodynamic yaw controls on flex-wing hang gliders (see the related article on this website entitled "Experimental results and interpretation: yaw experiments with a controllable rudder and wingtip-mounted drogue chutes on flex-wing hang gliders" suggest that an aerodynamic surface that creates a yaw response on a flex-wing hang glider, might also create a "wrong-way" roll response, especially at low angles-of-attack (i.e. with the bar well pulled-in) and especially with the VG loose. Anyone experimenting with spoilerons should be aware of this possibility, and should be prepared to ease the bar out to increase the wing's angle-of-attack if a "wrong-way" roll response does arise. However, Larry Smith and John Coyne emphasized to me that they did not experience a "wrong-way" roll response to the spoilerons in any corner of the flight envelope. This suggests that the spoilerons' primary lift-killing effect overpowered any "wrong-way" roll torque that may have been created by the interaction between the yaw from the spoilerons and the gliders' anhedral geometry.

It seems to me that spoilerons constitute a simple, useful addition to a flex-wing hang glider.

Copyright © 2004 aeroexperiments.org