This section illustrates what some of us have done to enhance our beloved S10.  They are neither certified or approved by Stemme AG, so if you implement any of them, you do so at your own risk. Readers are encouraged to send their own enhancements for inclusion into these pages.


A new high aspect ratio blended winglet has been developed by Axella Aero Engineering for the S10 series.

Three seasons of use have shown significant improvements in roll response and authority and final glides are consistently above that experienced prior to fitment. Especially noticeable is control response in turbulence at landing. Thermalling performance at steep bank angles and high wing loading is exceptionally good, compared to other sailplanes. The glider will sustain thermal climbs hands off.

These winglets are not certified, or approved by Stemme AG, so may only be fitted to non-type certified S10.  We understand that there is another design from Austria as well.


The right hand cooling inlet duct directs air to the top of the engine, intercooler, oil cooler and finally the air filter plenum chamber.

If the flow to the aforementioned plenum chamber is blocked, it provides an increased flow through the oil cooler, reducing the oil temperature by approximately 10 deg C during full throttle climbs.

A separate NACA duct introduces air to the air filter plenum chamber.


Have you suffered a punctured tailwheel on an away trip?  A convenient solution is to carry a complete spare tail wheel mounted just behind the main battery.

This is the area used by the S12 for a luggage bay, so in case other light items are placed together with the wheel, a light plastic bonded mesh net was pop riveted with washers across the face of the next bulkhead to stop anything migrating down the tail boom.

Talking about loose items dropping down inside the tail boom, have you ever dropped your oil cap inside the tail boom whilst checking the oil tank level?  We soldered a washer onto the side of the cap, and tied a string onto it, securing the other end to a steel tube cross member. Now when we check the oil level, we let the cap hang outside the cowling.

The photo shows a battery to replace the original auxiliary tail battery.  It is mounted onto the plate which used to support the very old Becker transponder. The wires going to the tail were cut, an in-line blade fuse added and some compensating lead tail ballast was bolted onto the bottom of the fin in the position recommended by the factory.



Ventilation noise on the S10 series is relatively high.  The huge moulded NACA inlet shape underneath the footwell culminates in an air dam and relatively small duct distributing air to the cockpit. This air supposedly exits in a convoluted route under the centre console next to the control push rods.  Would a lot of smoke in the cockpit exit easily? A new exit duct, as used on modern high performance sailplanes, hopefully takes care of this.  The whispering noise during flight indicates that it is working well, and helping to lower cockpit pressure. Next the huge NACA inlet was reduced in size using a moulded piece with a smaller duct, and glued into place. This new duct had a smooth exit into the plenum chamber.  The cross section area of the duct is a better match to the tube up into the cockpit.  The result of these two changes is lower vent noise, with no perceivable reduction in air flow.


Several owners have reported coolant dripping from the rear end of the coolant radiator. This leak is from a weak point in the plastic header which was tapped to accept a metal pipe fitting, leaving only a few mm of plastic wall thickness, where it cracks. When gluing failed, and when no drop-in replacement radiator was available any more, the plastic headers were removed, aluminium ones fabricated using most of the existing fittings and then welded onto the core ends.  If you try this, make wooden dummy header tanks first, to check clearances. The photo shows one error, where the top left corner should have been bevelled to accommodate the inlet duct, which in this case was modified instead.


If you have a hangar deep enough, you may be able to move your S10 in sideways, without folding the wings. The photo shows a one-man hangar dolly which works very well. It has since been improved with a 12v “caravan mover” replacing the arms shown on the right hand side.


Bumper in the USA, sold his S10 many years ago and offers the use of the tool he made to service the bearing at the top of the fork.  The “tailwheel anti-shimmy” upper bearing applies friction to the tailwheel fork’s vertical tube when the wheel is on the ground. When in the air, the tailwheel drops down a small amount to remove this friction so it doesn’t interfere with the rudder.

The tailwheel friction bearing is made of brass and is fixed at the top of the fork tube housing with adhesive. There’s a threaded center shaft that holds the tailwheel fork in place. The fiction bearing will fail due to wear, the top end of the fork tube cutting into the brass in use. The bearing can also break loose from the adhesive. If the friction bearing needs replacement, it’s important to remove the old adhesive, this tool is designed to do that.

The tool consists of a flat, washer like surface that is welded to a hollow shaft for clearance on the tail assembly center bolt. Self adhesive abrasive paper is attached to the upper surface and this is then put inside the tailwheel tube housing and spun with a hand drill to clean the surface so a new bearing can be installed.

If you contact Bumper, he will send you the tool, and after using it, you keep it until the next owner needs it.  Use the Contact page to send your request.