Mk IV Yaw String

(Inc. 20% VAT)
(£8.13 Exc. VAT)

General Description

The MK IV “high tech” Yaw String - is the only Yaw Strig with a clear turbulator base. Do not be fooled by imitations. This is not your ordinary yaw string. The clear base raises the synthetic yarn 0.038″ above the canopy eliminating scratches and reducing static charge. We use premium synthetic yarn and if the Yaw String needs to be removed, it leaves behind no adhesive residue.  Each yaw string is meticulously handcrafted through a 28-step proprietary process done under a magnifying glass which produces the best quality and clarity. After production, each Yaw String is inspected under a magnifying glass again by quality control.


About the Yaw String

The yaw string is the most effective, yet least expensive, slip/skid indicator. It is made from a piece of yarn mounted in the free airstream in a place easily visible to the pilot. The yaw string indicates whether the pilot is using the rudder and aileron inputs together in a coordinated fashion. When the controls are properly coordinated, the yarn points straight back, aligned with the longitudinal axis of the glider. During a slipping turn, the tail of the yaw string is offset toward the outside of the turn. In flight, the rule to remember is simple: step on the head of the yaw string. If the head of the yaw string is to the right of the tail, then the pilot needs to apply the right pedal. If the head of the yaw string is to the left of the tail, then the pilot should apply the left pedal.

Installation instructions

Determine the ship's true centerline for mounting the MKIV base and included an optional center index dot. A good method is to stretch a string from nose to tail. Tie or tape one end of the string to the glider nose and the other end to the top center of the horizontal stab or vertical stab. Stand away from the front of the glider and sight down the string to be sure it’s straight and on center all the way from nose to tail. You may need to lift and move the string from one side or the other where it crests the curve of the canopy. Place a piece of masking tape under the string just forward of where you will install MKIV and mark the centerline on tape with a pen. Move the string off to the side and clean the area for MKIV with denatured or rubbing alcohol and a soft cloth (I recommend microfiber). Move the string back to the center.

Make a paper template guide to ensure an easy and accurate installation. Cut a strip of paper approx 2″ (50mm) wide by about 8″ (200mm) long. Position the MKIV base at the center of this strip so that only the curved portion at the back of the base is off the paper (align the two corners of the rounded base with the edge of the paper). Trace around the pointed front of the MKIV base with a pencil (no ink) to form a “V”. Cut out a “V” with scissors and discard. Place template with “V” cutout under string (apex of template “V” cutout facing forward – open end facing aft). Sight down on the template strip to ensure it is perpendicular to the string, tape ends in place.

Yarn is supplied long, cut length to suit, and tie a simple overhand knot ¼″ (6mm) from the end to prevent fraying. If using an optional center index dot (this is the reflective dot located loose in the MKIV package) temporarily place the MKIV base in template “V” and gently stretch the yarn aft. Mark the desired dot location with tape on the outside of the canopy. Dot will be installed on the INSIDE surface of the canopy.

With the “V” template and center mark in place, remove the string. Clean the inside canopy surface where the index dot will go with denatured or rubbing alcohol. Hold the index dot between finders and bend one edge gently away from the reflective side to loosen the dot from backing (do not crease). Use the tip of a clean utility knife, or other small knife blade or sharp tweezers, to lift the edge of the dot from the liner. Then using a knife tip or tweezers, position the dot before smoothing it down with your finger. Use caution to avoid scratching the canopy with a knife blade. With the dot installed, close the canopy.

Hold the MKIV base only by edges or yarn and remove the red adhesive liner by lifting a rear corner edge with a knife tip so you can grasp the liner and peel it off with tweezers or fingernails. Reattach about ¼″ (6mm) of the pointed tip of the removed liner to the back center of the base adhesive to form a temporary “handle”. CAUTION! do not touch the exposed clear adhesive surface with anything but the removed liner or allow yarn to contact it as this will impair the optical clarity of the base. The adhesive is very tacky and once it touches the canopy plastic you will be unable to reposition the base without damaging the MKIV. Steady your hand against the canopy and hold the base using the “liner handle” in position over the “V” template cutout. Maintain a slight and even gap on both sides of the “V” cutout and base. Do not butt the MKIV base tightly into the “V” or the adhesive may overlap or touch the paper template.

Okay, the goal is to get it on straight and with no bubbles under the adhesive, take it slow and this will be easy. Touch the pointed end of the base to the canopy first while holding the back of the base up a bit, away from the canopy using the “handle”. Use a smooth object (retracted pen tip etc.) to slowly work the base down while watching the adhesive progressively make contact with the canopy, this is easy to see and looks like water between two sheets of glass. Before getting more than half the base attached, and while bending up the back of the base to keep it off the canopy, grasp the rear of the base by edge corners and gently remove the red liner “handle” by peeling off ( twist “handle” slightly and pull in line with canopy surface, not in line with base surface – so as not to stretch adhesive). Work the remainder of the base down. With a finger, firmly press the base down for several seconds. You may fly immediately, but please don’t wash or disturb the MKIV base for 24 hours to allow full adhesive strength.

After several years of exposure, you may wish to replace the MKIV as the yarn wears or fades. To remove the old base lift edge and “roll off” with finger pressure. Or use a fingernail, knife blade, or similar tool to lift an edge of the clear plastic top layer using caution not to touch the canopy with any tool. Grasp the edge of the base with fingers or needle nose pliers and slowly peel off. Any remaining adhesive residue will cleanly roll off with finger pressure.


Another type of slip/skid indicator is the inclinometer. Like the magnetic compass, this instrument requires no electrical power or input from other aircraft systems. The inclinometer is influenced by centrifugal force and gravity. Mounted in the bottom of a turn–and–bank indicator or mounted separately in the instrument panel, the inclinometer consists of a metal ball in an oil–filled, curved glass tube. When the glider is flying in coordinated fashion, the ball remains centered at the bottom of the glass tube. The inclinometer differs from the yaw string during uncoordinated flight. The ball moves to the inside of the turn to indicate a slip and to the outside of the turn to indicate a skid. Remember the phrase, “step on the ball” in reference to the inclinometer; it helps coordinate the turn using rudder inputs. The long glider wing tends to increase the adverse yaw effects from the ailerons and requires more rudder control than many aircraft. Source –Glider Flying Handbook.