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Apr 06, 2014, 10:37 AM
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Build Log

Multiplex quarter-scale Ka6e detailed restoration

A few weeks after the last post concerning my unrestored Multiplex Ka6e adjustment flights (with the pictures of the windhose mishap to the real glider), I got in touch with the photographer and the owner of the glider at the time of that mishap (2010). I got a good selection of more detailed pictures and was surprised about the extent of the damage. The detailed cockpit interior pictures proved an invaluable source of necessary data, and I also got the word the glider is lingering around “as is” in a hangar at St Hubert airfield, in the hands of a well-known Belgian restorer with no progress having been made at the end of 2013.

Mid October I decided to ground my secondhand model after a total of 10 adjustment flights so I could start the restoration. After elaborated searches I had obtained pieces of yellow vinyl, fire-orange and cub-yellow Oracover, which all seemed to match the original colors rather well. The owner of the real Ka6e running a van modification shop, just mixed colors till they looked good, but didn’t take notes so getting them off the shelf with RAL numbers was not an option. Oracover also exists in the so called “scale” variety, which is completely opaque, but the catalogue warns this was obtained by a thin layer of aluminum which incidentally also tends to block RF signals towards internally mounted antennas.

I first experimented with the Oracover and vinyl to see how opaque these would be, and how much they stretched or could be shrunk to follow the contour lines of the nose. Following picture shows a stretch of yellow vinyl on the white original old cover of unknown brand, but allowing the thin black outboard wing mark to show through, both in color and slight step. The fire-orange Oracover then was ironed on a dented portion of the horizontal stabilizer, and another strip over itself, then via the white old cover onto the yellow vinyl. The dent in the surface got even more visible. The orange covered well on all colors, but on itself the overlap remained too visible for me.

Scale Oracover had already been eliminated from the possibilities, and both standard cub-yellow and fluo-red allowed color differences from the surface to show through. I thus opted to use yellow vinyl to cover the stripped relatively flat wing and tail surfaces, and have the complex curved GFK/GRP fuselage painted in exact the same yellow by a professional antique and custom car painter, who happens to be a club member. The nosecone being the most difficult to cover, I experimented with pieces of Oracover over the unprepared white nose, and intentionally patched half elevator before risking it on the later finished surfaces. Probably my limited skills with Oracover also played a role, but I found it easier to stretch the vinyl (even cold) over the nose, and that completely eliminated Oracover from this project. Although it took a while to get it to contour properly, I believe a more motivated application would allow me to stretch the orange vinyl over the round nose without creases or seams at a later stage.

The tailplanes

I used my small HK Iron at a high temperature to remove the old covering of one tailplane half. The temperature proved too low to remove all the color and glue, so I purchased a digitally controlled high capacity heat gun for the wings. After sanding off the last bit of glue from the elevators, I was surprised the base was balsa instead of the much more solid Obechi wood, which explains why it showed so many dents and creases. I filled those with wood from tubes (Polyfilla being the best substance, but the wrong color, and Soudal the best color, but poor working substance) and sanded the surfaces smooth again before applying some coats of pore filler. After sanding those, I wanted to apply the yellow vinyl, but a small surface test revealed the different wood and filler colors showed through too much. I then tried light grey primer but that didn’t hold on the two layers of smooth sanded filler. Sanding everything off again, I then roughened up the surface but almost completely eliminated the strong filler. Parquet varnish to harden the assembly would have been perfect, but was translucent and wouldn’t even out the wood shades. I thus reluctantly applied a coat of pale yellow lacquer as a base for the vinyl. It smelled like hell and according to the label took 16 hours to dry under the kitchen smoke extractor.

During that lull I removed the rudder so it could be taken care of the same way as the two horizontal tailplane halves. Having not been happy with the play on the control cables, I cut all of them through so I could remove everything for the fuselage spray. After removing the rudder covering and sanding filler, I discovered a major gap in the inside foam, just above the actuator horn. I suppose it had been fastened with a kind of foam eating glue, and I first recreated structural integrity before proceeding further on the rudder preparation.

Only after lightly sanding the dry elevator portions did I see how uneven those surfaces still were, and the relatively thick yellow lacquer layer gave me a good indication of where to sand or fill. First using 180 grit paper on a block sander, later 400 grit in the hand palm, produced the desired smoothness after hours of dirty work on the terrace. I really had no choice because the high gloss finish of the thin vinyl would amplify any imperfections in the basic surface.

With so much of the balsa unprotected again, but only light color variations, I opted to apply a few coats of hard parquet varnish so these delicate surfaces would not get dented so easily anymore in the future.

The fuselage and servos

The other side of the rudder control cables and wooden elevator pushrod were connected to 70’s large Simprop Contest 60gr servos, three abreast mid-high position just forward of the cockpit rear part. This might have been easy to install, but protruded so much into the pilot seat area that he had to be seated too far forward. These servos stood in the way for a scale cockpit (as can be seen on the various model cockpit pictures in my initial Ka6e blog). I thus took those 3 servos out, and Dremeled off the servo mount plate, keeping just the extreme starboard section on which I cut off the servo recess deeper so the elevator servo could be mounted almost flat against the fuselage. This was the only possible solution because I could not modify the elevator pushrod (completely enclosed in the inaccessible fuselage) and thus had to maintain its original length. The servo and actuator are now well out of the way and will be hidden under the pilot’s right arm and shoulder.

The middle servo commanded the Bowden rudder cables, those could be shortened by making knots in the cords, so I modified and epoxied part of the removed servo plate perpendicular to the fuselage as close as possible to the cockpit back, to gain pilot space. That servo will be hidden under the pilot’s back. I thus was able to keep the (70’s) period original servos (desirable for such an authentic old glider model), and although hidden with the pilot in place, they are easily accessible for maintenance. The third servo used for nose hook release was completely removed from its illogical position, and figuring out it had seen little use in the past, I substituted it as the elevator servo, the latter being kept as spare for the two active ones. Compare following picture of the works in progress to the ones in the beginning of this project, and see how much pilot space I gained (elevator pushrod just lays on rudder servo position but will be connected later on the other side) .

A modern 2,5kgcm analog servo for the towhook release was then installed in the nose, just behind the original multiplex hook, with just a short stub being pushed in and out. To install that small servo in the middle of the nose required the fabrication of a removable plywood half-frame member, to which I glued the servo support blocks. Being deep in the nose, the servo had to be screwed onto the block before the assembly was mounted as a whole with two horizontal screws onto the frame member, incidentally also keeping the lead in the nose tight. On following picture you can see: the plywood frame resting against, and prior to being bolted on the existing nose frame member, the servo already mounted on its dedicated support blocks, the lead in the nose with the hole for the tow mechanism, the foam blocks with magnets and bottom supports for the instrument panel which will completely hide the deeper modifications.

Some real Ka6 gliders even didn’t have a nose hook connection, but only one hook at the bottom left side for either towing or winching. For towing this made life more difficult for the pilot, because the glider veered to the right and wanted to climb. Most owners ordered or later modified their glider with a nose hook, but the detailed cockpit pictures I have of OO-ZDR show no separate hook release knob or handle, nor a cable running to the nose. Model towing would be extremely difficult under such circumstances so I kept the nose hook, but reduced the aperture with epoxy as much as practicable too keep the pure nose shape intact. The nylon loop gets inserted through the bottom half of the aperture, and then slides up when pushed deeper. The servo then pushes the pin forward through the nylon loop, and comes to rest sticking out just a tad in the small remaining opening over the horizontal fixed strong bar. This allows for a super strong connection without any force to the servo, which only needs a minimum force to retract the pin out of the nylon loop to disconnect from the tug.

On that picture you also see the new flush mounted vertical reinforced balsa panel for the back of the cockpit area. I have cockpit pictures of 3 different Ka6e aircraft, and all show just a cupboard type of shell for the pilot to lay in, all have that rectangular open hole to the wing assembly compartment, and a kind of headrest on top of that. Compared to older more basic Ka6s, the E model (besides having a full flying tailplane) also has a much lower fuselage and flatter blown Perspex canopy. Whilst in older Ka6s the pilots were seated, in the E version they almost laid flat, thereby reducing the frontal area and increasing the glide angle to 1:34. That was a respectable figure for a basically wooden glider more than half a century ago. I suppose the pilot parachute takes care of covering that hole during flight, but haven’t found evidence of that so far. On following picture you can see how after the wings have been bolted on, a yellow GRP fairing is mounted on top over the grey curved headrest. The dayglo strips resting on the pilot cushion and sticking through the access hole, are dismantled wing spoilers.

I wasn’t happy with the friction between the very tight wheel well and the 75mm diameter tire. It would have been easier changing that wheel into a stock Graupner 70x25 wheel, but the original was a good condition Kavan 75x3 on an aluminum 3-screw flat rim with the tire marked W-Germany, a proof that tire was from the era before the fall of the Berlin wall. Wanting to keep as many original kit parts as possible into the model, I thus started carving out the GFK and plywood well until the wheel fitted and rotated freely. Neighbors must have thought a dentist started to practice in our building. Most other modelers might not have cared for such details, but to me it’s all part of a thorough restoration project. Whilst working in that area with the model upside down in a cradle, I also removed the ungainly winch hook which would have complicated sanding, and would see no use anymore because being towed by another aircraft is much more rewarding. I then lightly sanded the complete fuselage to improve the primer adherence, and discovered the many traces of mishandling during the past decades. I used strong epoxy instead of filler to repair all holes, dents and nicks on the GRP hull. I also used plywood strips to minimize the play of the floating wing spar through the fuselage, and enlarged the holes used for connecting the wing by rubber bands, to allow for installation of a stronger carry through spring. I preferred the latter system to be sure my fixed Multiplex wing connectors would not loose contact after slight wing movements (dragging the ground during the initial takeoff). Canopy rail and wing fuselage join area needed lots of attention to get them flush and flowing.

The cockpit interior

Preferring not to take risks damaging the fuselage paint when further detailing the interior, I elected to complete the interior before having it painted. As you can see on the above picture, the real cockpit is formed by a multitude of frames and wooden panels, and the seat and map pouch had recurring names of four French wine regions on grained fabric. I first made frames by cutting out each one from paper templates I made. Their length, curves and shapes vary for each one, but after a basic cut in Depron, they could then be bended a bit to be glued in the fuselage. The 4 forward frames were made of light plywood because each time the pilot would have to be seated (after a battery change or charge), his feet would have to be pushed in the narrow space around the instrument panel, and completely past the first frame row till resting against the recently constructed hook-servo plate (in a real Ka6 the feet go all the way into the nosecone). Depron would not have been sufficiently solid to withstand such repeated rubbing. I also made a plywood footplate in the portion between the nose and the second frame (that would support the instrument panel). I then used 2mm plywood again to make a removable assembly to contain the battery, Castle Creation 10A BEC and Deans plug, plus serve as a channel for the wiring towards the main electrical switch on the instrument panel, and between the tow servo and the receiver behind the cockpit. This assembly became a kind of coffin where the 2S2100 battery could be slid forward or back to make CG changes, and form the base for the removable seat (to access the battery). To increase position rigidity and stability, a plywood footplate was made forward of the more elevated seat rails. The back of those rails slide around the wheel arch under the repositioned rudder servo. Following picture illustrates how little space the displaced servos now take in the scale cockpit, and the Depron and plywood custom-made structures.

I then used 1mm balsa strips to make the elbow level cockpit sides. I could have used stronger 2mm balsa for the two angled parts on the starboard side, but the port side being a single curved wooden panel dictated the smaller thickness. After those strips had been glued to the Depron formers, I used balsa and Depron to duplicate the bow details between the canopy opening and the large vertical fuselage separation panel. The headrest was carved and sanded out of a piece of foam, and slides under the top arch, to be held in place against the wing dowel by a magnet. It has to be removable because my receiver, satellite receiver, all the electrical wiring, and rudder Bowden cables will be installed later in the center of the fuselage. I then glued additional foam blocks against that back wall, to make a support for a magnet held curved cover plate over the servos. That cover plate forms the back of the seat support, and totally hides any model mechanics from view when installed. Compare the following picture to the one of the interior ones after the purchase, and see the improvement

Just as in a real Ka6e, the (scale) pilot is a tight fit in the narrow fuselage, and I often had to trial fit him to reshape items like the seat frame, seatback, instrument panel cut, stick and spoiler handle position etc.

With the fuselage paint probably adding even more weight behind the CG, I knew flying would always have to be done with the pilot in place. The seat covering thus would become mostly invisible, but prominent If on static display without pilot. I then punched all places in the cockpit where the original glider shows traced of screws to hold things together, then after varnishing to solidify everything, I painted the interior in a grey/blue. The unique seat print was impossible to reproduce in scale, so I opted to scale-down pictures of the real seat and pouch, and with a patchwork of multiple layers, obtained a realistic result that was glued on simple acetate sheets. This had been chosen because it was easy to cut and bend in shape, and once affixed to a slightly wider balsa rail, had a tight fit over the battery box. My pilot already coming equipped with a harness on, the ones on the picture just had to be adapted a bit to run along the seat pan and the back. I used the same photo system to make the map pouch, and reduced an aviation map advertisement on the internet to insert it in the pouch (photo glued over a shaped piece of foam). I cut some scrap aluminum to make the strip that holds the pouch up on the side panel, and also made the metal serial-number plate for the back of the cockpit. A few more details such as piano wire for the rudder cables, and a microphone along the pilots right arm, plus some detailed bits and pieces around the headrest, tremendously enhance the scale aspect.

In the front of the cockpit, I glued a slide-in support for my custom-made plywood instrument panel, held in place by magnets glued on foam blocks along the fuselage behind the fake instrument panel bolts. Instead of just gluing a complete fuzzy picture on the wood, I elected to copy higher quality pictures of the exact same instruments and fuse types for sale on the internet. After gluing them on the satin black vinyl-covered wood, I surrounded the relevant instruments with rubber (plumbing type) O-rings to create depth. I then found an automotive small on-off switch for which I drilled a hole at exact the same place the real glider has his main switch. I then made all labels on my pc, just exchanging the real glider owner’s name and telephone number by mine, so people finding my glider after a mishap can call me to get (the pieces) back. Placing the mandatory info with your name/address/telephone number/national modeler number (in case of accident or lost model) is never obvious in a full scale model. In case the model is found in one piece, hiding the plaque somewhere inside would render it unusable because other people have no idea how the dismantle the model. Opening the cockpit is obvious and straightforward so I figured printing all my data on the back of the loose scale-map in the pouch was the best option. Sooner or later, people finding the glider would take the map out of curiosity, and discover my data on the back, providing them contact information to get my glider back.

Next came the stick, which I custom produced from a multitude of scrap parts, and the towhook release handle on the seat made of a wooden dowel and some cord. The spoiler handle was bought with the mike and other quarter-scale glider parts, but mounted on a flexible aluminum lever because it has to be capable of being inserted in the model pilot’s hand, just as the stick. The white spoiler actuator rod is a piece of hollow plastic control-actuator sleeve. The overall result is very pleasing, but only clearly visible without the cockpit in position because the panel sits rather deep under the nose fairing.

With the pilot installed for actual flying, much of the work becomes hidden, but I still prefer that to seeing a glider flying around without pilot. On following picture you can see how tight the fit is for his feet and legs, and hands around the controls (the green trim lever was straightened-out later)

In the meantime my special-order vinyl adhesive arrived in the desired colors, and I started covering the tailplane so my painter could match the fuselage paint to it. I also had received the quarter-scale opening cockpit window, which I affixed in the canopy without actually making the large opening. I opted for that solution because I didn’t want to spoil the aerodynamic qualities by an incidentally open sliding window. Mounting it flush with the six conical copper 1mm screws was already a big enough challenge, but well worth the cosmetic result. I also experimented covering the spoiler parts with vinyl and that proved feasible. The dayglo vinyl is much thicker as the standard colors and is more difficult to apply if it has to follow tight bends. When my professional car painter called I could bring my fuselage, I just removed all my prefabricated interior parts and handed him the 95% prepared fuselage and canopy for finishing. Here you can see the prefabricated bits and pieces we talked about so far.

Before delivering it to the paint shop, I made further experiments trying to stretch vinyl over the unpainted nose, using a heat gun and different material thickness’s, but with disappointing results. I was able to create a bulge in a flat sheet, but not over the depth I wanted, and always ended-up with undesirable crease lines. Maybe painting the nose will be the only solution, one I wanted to avoid because of the delicacy of matching the dayglo paint to the rest of the decoration, and the tendency of that paint to pale-down when exposed to the sun.

The wings

With the fuselage in the paint shop for a while, I started on the wings. To obtain a near perfect finish, the only solution was to use my powerful temperature-adjustable heat gun to remove the cover-material that had been applied decades ago. I still have no idea what it was: Monocote? Oracover? Solartex? Using 120°C exhaust air gave the best results to remove not only the plastic foil, but also lift the paint and glue with it in one go, from the Obechi covered wing. The protruding aileron servo covers on the underside of the wing got replaced with thinner ones, who were countersunk as much as possible to obtain a nearly smooth flat intrados with minimum aperture for the servo arm. Ailerons were removed, filled, and covered separately with an overlap at their invisible front

After my problems getting the tail surfaces smooth and straight before vinyling, I opted for a different approach on the wings. Obechi wood being stronger than balsa, I didn’t need to reinforce the surface with varnish so I could peel back to reposition the vinyl during the application (on such a large compound curve surface). The bottom of the wing was convex at the front and concave at the trailing edge, and the wing tapered along its entire width, and the trailing edge had a kink. Applying a single huge piece of flat vinyl covering both sides in order not to have a joint at the leading edge, and applying shoulder to shoulder joints with the dayglo panels, was a very challenging task requiring excellent surface preparation. I used two jars of Hobbico Hobbylite balsa-colored filler, and multiple sanding passes before obtaining a consistent smooth wing profile without depressions. I then started with the application of the wide dayglo panel around the spoiler area, using a ruler and 90° triangle to get that perfectly aligned with the flight direction. Although the vinyl is self-adhesive, it is thick (and therefore stiff) to be opaque for the material to be covered. Joining them at the thin trailing edge would be problematic, but previous mishaps during applications learned me it sticks extremely well to itself. If you ever allow the two sticky sides to accidentally touch, you better discard that complete panel, because separating them stretches the vinyl to such an extent that you will have enormous problems applying it over a flat surface again. On the other hand, having a few millimeters overlap with the sticky side over the shiny side, provides sufficient holding power to get the end to stick solidly even after a 180° bend.

With that in mind, I started applying the vinyl from the trailing edge of the bottom part, then to the front, around the leading edge, and back via the top to the trailing edge, then around it before sticking it over the start of the sheet with a centimeter overlap. Of course the wing taper causes the vinyl to make an angle after rounding the leading edge, but using paper patterns to experiment before cutting the vinyl, allows you to cater for that so the lines on top and bottom are parallel. After that, the inner wing large yellow panel was applied shoulder-to-shoulder, then the one-piece very large yellow outside part. If like me you have no extra hands to keep the panels from the surface during application, you better prepare strips of former protective greasy paper that you apply in adjacent layers, and will only be removed as you advance further along the surface. Sorry that I have no pictures of that, but I already needed 6 hands just to apply the vinyl, only had two, and had to work in one go without interruption. Although unavoidable, lifting of already applied vinyl should be kept to a minimum because stretching will occur and complicate the work further down. I can recall about 20 partial liftings per vinyl length application. It was a work of thinking, preparation, feeling for the material, tension regulation, and very slow advance, but after more than an hour for each individual color panel, I was able to look back at a perfectly smooth surface without a single wrinkle or air bubble.

Before tackling the wing extremities, I had to think about making protections to keep the wing bottom from scraping hard surfaces. In my club we use a tarmac surface for takeoff and landing, so I knew whatever I made in the shape of the real glider’s protective skids, would probably not survive a season, and thus had to be replaceable (yes I intend to fly for many more years with that model). I opted to use highly-modified Hobby King large nylon skids that could be bolted onto solid metal nuts permanently glued invisibly under the vinyl. For lateral solidity, I wanted the two side bolts in the front, and therefore used the Dremel to reshape those nylon skids closer to the real glider’s wooden skids. The nylon wouldn’t last for 10 ground movements, so I epoxied 3mm plywood plates to both sides of it, then sanded the assembly into an aerodynamic bulbous shape with a tie-down hole in the middle, before multiple epoxy layers coated the created assembly for additional erosion protection. This was also constructed that way because after flying, I still had to slide those wings into their foamy individual sleeves for transportation, the standard thin-edge skids either blocked the movement or slowly destroyed the foam. For the nuts I used reversed wood self-tightening M3 nuts so their rounded shape could me mounted flush under the vinyl between the skid assembly. After some dry fittings, the skid assembly was painted, and the end of the wing with epoxied nuts and position guide-holes got covered with dayglo vinyl panels. I made 6 additional skid assemblies, ready to be bolted on when necessary. The picture below shows the basic HK skid on the upper right, a shaped one on the lower right, plywood pieces epoxied on the middle, epoxy glassed sabot shaped skid on the upper left, and painted skid assembly on the lower left. Upper wing shows the inverted woodnuts epoxied flush, and vinyl piece to be applied. The lower wing shows the same assembly after being vinyled and painstakingly stretched around the complex curved wingtip shape. The original skid pins were retained (but shortened)and tight channels drilled in the wings to receive them, all in order to increase lateral stiffness in case of groundloops after landing.

About the same time my wings were completed, I got a message from my painter that my fuselage and canopy(frame) had been painted. The attached pictures of my model drying (for a week) looked very promising. His yellow paint perfectly matched my vinyl covered rudder.

The difficult canopy frame looked good on picture, but later proved unacceptable due to former black paint traces between the clear canopy and the wooden frame. I certainly don’t blame the painter for that, but rather the guy who didn’t fill the voids when gluing both together decades ago. I later corrected it by masking the inside of the canopy with tape, and allowing liberal amounts of a similar yellow paint to fill the voids (applied by a much shortened brush).

When I arrived to collect the model, I just looked in awe at the quality the painter had delivered, his price was right, but the result was so much better as I ever could have imagined. With such high standards, I felt obliged to raise my finishing touches as well. To ensure the paint was rock solid he recommended me that I allowed the model to dry out for a full week. I certainly did not want to take any risks of tearing off paint when trying to apply the vinyl decorations.

Vinyling the nose

I knew getting the nose covered was the biggest challenge of this model, and using paper patterns, I tried various shapes to see how I could get the intrinsic nose decoration applied with a minimum of visible joints. When I got close to the multiple curved shapes, I cut them out inn inferior quality yellow leftovers, and attempted to stretch them around the nose to see where the streaks would point back and where the wrinkles were impossible to flatten out.

It quickly became obvious that even with the better quality orange vinyl, it would be impossible to cover the nose in one go. I then experimented with a piece that hopefully would cover the top, sides and upper nosecone in one go, but even after stretching it painstakingly with heat during hours, the result never pointed towards a satisfactory outcome, and would result in a very visible joint along the fuselage sides.

After much thoughts, I figured the only practical solution to the problem was to stretch a first piece from the nose back, as far as I could get it to lay flat almost all around the nose, almost because the last centimeter between the towhook orifice and the underside all the way under the cockpit, was impossible to flatten. This was as good as I ever could get it, so this became the new starting point.

With the top line appearing to be 2cm wide, I figured that by cutting the bottom part of each flap away one centimeter from the centerline, I could then shape a two centimeter wide strip and install it shoulder-to-shoulder to fill the gap where the creases between the towhook and the bottom of the cockpit and been. I made that strip long enough so it could be applied joint-less from the nose till the wheel well. I then used a fresh cutter to separate the ‘perfect’ nosecone from the wrinkled part that couldn’t be made to fit, but not cutting so deep as to cut into the paint job.

The above picture makes it clear that when scrutinized from nearby, the seam is visible from below, but on the next picture it is nearly invisible from a normal viewpoint. With the most pronounced part of the nosecone having been negotiated, I used a few clean sheets of paper to make a single pattern for the remainder of the complex lines leading to the thin stripes along the fuselage. After a few trial and errors regarding the sweep angles, I was able to draw a pattern that could be applied shoulder-to-shoulder to the already applied dayglo panels, and mirrored the elegant sweeping bows towards the four cardinal fuselage corners. In order to look symmetrical, all those lines first had to be hand drawn, then heart lines were marked before the symmetrical bows were produced using parts of an anniversary large golden carton number 6 (offering various elliptical shapes). When the final paper was laid out flat, it became obvious there was no way I could cut both side stripes out on a single width of vinyl because the lines fanned out too much. I then decided to make a fan with the wide top stripe to continue till the cockpit, and the side bows to stop where they reached the 5mm start of the thin fuselage line. The pattern was then cut out along the exact lines, and corrected for a seamless joint with existing parts, before it was transposed inverted to the back of the vinyl cover.

After cutting out the vinyl and before removing the supportive paper, more trial fittings and millimetric adjustments were made in order for all parts to touch each other without any gaps nor overlaps. Small pencil marks were then applied on the upper center of both dayglo panels, and the protective paper carefully removed only from the middle portion, without unnecessarily stretching the vinyl. This crown piece was then positioned from the top middle, alligning the previously applied pencil marks, and the top stripe pushed down until in the cockpit. Next the side protective paper was carefully removed and the front of the crown pushed against the nosecone. From there on the rest was flattened out towards the back, observing the symmetry of the port and starboard sweeps along the fuselage from along the nosecone. This time not much stretch nor compression was needed, and this critical part could be applied without any heat.

I admit the finished nose shows a seam between the cone and the streaks, but this was the best I could achieve and it does not look so unrealistic, even close by. Here is a picture of the finished looks, and some of the test patterns I used before getting it right.

Final decorations

I initially delayed the remainder of the fuselage striping till I knew were the registration letters would end. Making the latter proved more work as anticipated. Scaling the pictures of the original airplane up and down according to the model’s fuselage length and diameter, then measuring the letters’ height versus width ratio, then character thickness and spacing, I finally was able to cut out patterns of the letter type, and transferred them to vinyl for the final cut. I then drew a grease pencil helpline on the fuselage, because getting those letters in a straight line and perfectly vertical was no sinecure. The letters O have to be started from the top middle, but getting the curved vertical parts to nicely align so the bottom part falls neatly flat is not so easy. The letter Z has to be applied starting with the short horizontal stripe along the cheat line, hoping the long diagonal part doesn’t bend and cause the bottom line not being parallel to the top one. The letters D and R have to be applied starting at their left vertical side, but the problems for the remainder of the letter is similar to the letter O problem. If parts of a letter start sticking to the fuselage, forget about lifting it again because these thin letters stretch out so much in the process, that they become asymmetrical. Satisfied they ended-up in a straight line, I started to apply the thin fuselage line making an elegant but difficult to apply flowing curve. Looking at the result from a distance showed a disaster. Whereas the line should have intersected the middle of the letters and flow into the hyphen, it wasn’t aligned at all. My letters D and R didn’t look like the original letter type, and when those letters were applied on the highly curved fuselage, proved too high and too thick.

Back to the drawing board to figure out new sizes and ratios, thickness, angle versus fuselage tapering, and letter type design. The letters I had made for the other side were useless, and the ones applied destroyed by removal. Two complete new sets were cut, and this time applied starting from the fuselage-line reference towards the tail. Obtaining the symmetry on the other side required much eyeballing from the nose and tail of the glider, but the final result was stunning. Getting everything from flat pictures into a constantly curving and tapering fuselage proved much more complicated as initially imagined. Even larger letters then had to be applied on the intrados of the port wing, and again necessitated many calculations and dry runs with patterns, for the letters to coincide with the aileron cutout, spoiler area dayglo panel, and different aileron actuator position. Please compare following pictures depicting my model in the same angle as the real glider, and notice how faithful my quarter scale model became.

Even more remarkable is the comparison between the interiors of the real glider and the model, taken from a same angle, and both having parts of their spoilers laying on the seat.

After the post restoration weight and balance check, I found out it now weighed (battery included) 5,5kg and thus gained half a kilo. I also had to add some lead in the nose to compensate for the new position of the servos and the weight of the paint and vinyl that mostly is behind the CG (now 92mm from the leading edge). A 10% in overall weight is more than acceptable considering the extra detailing and finishing that took place over the winter. I just had 2 hours to spare before I loaded the finally completed glider in my car to show it to the other club members during the post winter ‘build evening’ where everybody shows their completed projects. 12 hours later I was on the road for a well-deserved ski holiday in Italy.

Flying the beauty

A week after my return, temperatures in March had reached spring levels, and after a couple of towed refamiliarisation flights with my Parkzone Ka8b, I felt ready to hook up my Ka6e to a powerful Robin tug for the maiden of my restored beauty. During assembly on the field, I discovered a few minor problems assembling the wings on the now play-less floating spar, but after half an hour of help by clubmembers and their tools, got everything ready for the maiden.
Yes I was apprehensive, feeling rusty after not having flown serious gliders for half a year, and flying a model that I spent 4 months to restore into a true quarter scale marvel, behind a Robin towship I never flew behind. My fear proved unfound, the 3 flights that day went without a glitch, and even with both the main runway and the grass strip blocked by other models, managed to get my precious Ka6e down (albeit at that time not that smooth) on the remaining stretch of runway. When it’s on the ground, I cannot take my eyes of that beauty, and when it’s in the air, it is so elegant and visible in that paint scheme, people just love it as much as I do. The increase in weight is not very noticeable during tow or gliding because contrary to a Ka8b, a Ka6e needs to be flown at speed to perform well. Landing her is simple and can be done very smoothly up to ¾ spoilers. With full spoilers, it drops like a brick when the speeds gets a little low, and full up elevator is not sufficient to break the rate of descent, even dropping in ground effect from only half a meter. Without spoilers, it floats forever and is even rather touchy on the elevator. Loopings are easy, but barrel rolls nearly impossible. So far I always aborted the attempts, and recovered with a split S from the inverted position.

Awaiting higher quality videos this summer, I can only show a couple of shots made during the first post restoration flights. Here is a takeoff and tow to altitude
Ka6 second tow (1 min 0 sec)

And the second landing, where I could not fly a normal circuit because both the grass strip and the runway were initially blocked. You see me extending my downwind to gain time, and after they removed the 6m glider from the grass, I initially rolled out for that. When the tow got airborne in time, I sidestepped onto the main runway but being so low, didn’t date to pull much spoilers and landed long. With another retractable gear glider in the pattern, I intentionally veered off the main runway to create landing space.
Ka6 landing (0 min 30 sec)

The following week I made about 10 flight and started getting the hang of it again. I never would have expected this 30-year old sober secondhand glider to become such a solid and elegant scale performer in less than a year. Although I never have flown a real Ka6, I became very fond of this model, and hope it will survive another 30 years of use, providing other pilots and the public with the sights of sixties era competition gliders, at a time everybody flies similar looking plastics. Within the month following the completion of this restoration, I was able to acquire two other secondhand gliders, not really a necessity, but chances of them becoming available on the market in the future are so slim that I didn’t dare to let them go to anybody else. The first is a 25-year-old rare Twin Astir II in less than good condition, but with a solid GRP hull and real wooden wings (not only the cover, but also the inner structure. The tailplane is shabby and the canopy cracked at various places. After some searches I believe it could be a 1980 WIK kit but am still not 100% sure. Wingspan is 3m55 with optional extensions towards 4m10.

The second is a 4m Ka8b in traditional wood and fabric from Flair, was built 6 years ago and very grossly painted to portray a Schaffen Ka8b during the 80s. It is in flying condition and I will soon testfy it ‘as is’, the full restoration (including new fabric all around) will have to wait till after summer. Watch my blog entries for updates on those rare classic, and presently nearly unobtainable gliders.
Last edited by BAF23; Apr 06, 2014 at 04:05 PM.
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Jun 14, 2014, 08:53 AM
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Sad end of the Ka6e OO-ZDR model

Just as the real OO-ZDR came to a sad end when it overturned inside its trailer during a storm, my very historic detailed scale version didn’t survive Friday the 13th of 2014. After having suffered a receiver brownout during a previous large scale glider event, I replaced the Spectrum AR7000 dsm2 receiver by a more recent AR9010 dsmx receiver and paid particular attention to the orientation of the antenna and positioning of the satellite. I also did that because I installed a brand new Pitlab sky assistant variometer/altimeter, which I programmed to give an alarm at 500m height. The range check proved much better, even with the vario transmitting, loss of signal only occurred beyond 70m (that is more than twice the minimum figure).

Last Wednesday I took the Ka6e and Ka8b in my camper with the intention of spending the full 5 days at an international model glider happening in Wey (Germany). While socially it was ok, the flying was poor. During the first 3 days there must have been about 5 towplanes on the flight-line, and the same number that didn’t come out of their mega trailers, towing only started by the same motivated good pilot after 10.30 . A lot of the glider pilots stood in the row each morning, but half of them didn’t get towed when they had to stop the activities to mow the lawn, mandatory break between noon and 2pm (rather standard in Germany for noise), or theoretical lectures. It usualy was already 2.30pm before the starts resumed.

There was a variety of gliders with wingspans between 3,5m and 7m, and roughly 4kg and 23kg. Some of the towships were underpowered to tow the heavier gliders, and some could pull anything up with ease. On the second afternoon I already noted that some of those tugs were more appropriate for the very heavy gliders, and had problems reducing their tow speed to accommodate the older traditionally built wooden historic gliders. The tug pilot starting the sessions did a perfect job according to the gliders he saw behind him, but when others took over from him, the performance was not so consistent anymore.

That day I also talked extensively with the tow pilot who wrote the book and since 10 years setup the procedure for towing, and being towed, for the (then) big gliders. Because rumors inexplicably already had spread about my former aviation career, we also talked for more than an hour about our respective real aviation background (he retired as an airline captain and I from the military). He had made a new very powerful towplane and made the first tows with it that afternoon. That think had an awful power, and was climbing out very steep and rather fast. I thus wisely decided to take my Ka8b off the flightline after only 2 flights behind his conservative predecessor, and dismantled that balsa 4m Flair model for stowage in the camper for the rest of the weekend in Germany.

I knew my Ka6e was much more solid and never had problems being towed at the normal faster speeds. I had at least a dozen tows behind that pilot during the last weeks at events in Holland, Belgium and Germany, and liked his steady hand and consistent rate of turns. On the Friday afternoon I stood in line I already had noticed he pulled rather steep with a lot of power. When it was my turn we hooked up and took off. After takeoff we immediately had to turn about 180° for noise constraints, and he did that with what I sensed was 45° climb angle. I had to work very hard to keep an acceptable position behind him. After rolling out he allowed the speed to buildup even faster and initiated a left climbing turn during which I had trouble maintaining the correct bank angle. He jokingly made a comment he climbed like an F104 in afterburner. Being so concentrated I was not able to comment. After rolling out from that, we already were at 350 meters and he told me he aimed at a cloud so I could see my glider better. Once under that cloud I told him I was going to release and he acknowledged.

I activated the release and I had the impression we had a break, so I turned right and he initiated a left descending turn. This was to me the sign we had sufficient separation but the right turn inexplicably reversed into a left one. It was not a steep turn and I cannot remember attaining 45° of bank, nor pulling on the stick, but my Ka6 was still going fast, and less than 5 seconds after the release I saw a major part of a wing separate at the moment my altitude came through my earphone as 420 meters. My glider then plunged down vertically with me having no control over its fate anymore. We saw the impact about 300 meters from us at the edge of a crop field, the tail remaining vertical and well visible. The separated wing part very slowly came down spinning, and drifted off for about half a kilometer in high crops.

A friendly Dutch glider pilot volunteered to join me to get the pieces. We first went to the camping and changed from sandals to shoes, then set course into the fields. During the long walk I tried to recollect what had happened because at the time of the mishap I could not pinpoint what had gone wrong. Some thought I had not disconnected, other said they had seen the disconnect and turns from each other, it was total confusion because it all had happened so fast with no obvious clues or indications of the cause.

I knew from the speed of vertical impact that the model would be a total loss, but wasn’t prepared to for what I discovered. The aft half of the tail did survive relatively intact, the right wing seemed intact and still attached to the fuselage, but structural damage was visible span-wise. The left wing stub was still attached normally to the fuselage, but the separation did happen halfway the spoiler, which had been torn out and probably still is attached to the outer wing. There were no clues at the separation of how it happened. We were surprised the Styrofoam core was only reinforced by a span-wise 2mm thick top to bottom plywood wing spar between the obechi planking (without further reinforcement). Even stranger was that there was no leading edge nor trailing edge spar, just the thin obechi wood planking around the foam core. Those 1980 Multiplex gliders had been designed at a time that hand-launch along the slopes was the primary method of gliding, and the few towplanes were barely capable of getting such ‘large and heavy’ sailplanes in the air.

Forward of the wings, not much was left, I was able to recover my pilot puppet, it had serious scars in the face and had lost both hands, but the expensive variometer came out relatively unscratched from his back. The plastic attachment for the TEC tube was broken, but the print card was straight and looked intact. The rest of the nose was solidly buried about a foot in the soil, and I had to pull hard to get it all out. Similar to a bowling ball, the heavy 780 gram ballasted nosecone survived the impact very well, but everything else from the cockpit was just scattered. My friend had taken the precaution to bring a large waste plastic bag, and we collected everything in it and started walking back. I made the decision to not even go look for that outer wing part in an uncertain area of high crops. During the walk back I started feeling my stomach turn into a knot, and my throat to close, and that became worse with every step, and look at that strong towship still busy getting others in the air (albeit not so steep anymore).

Members of my club came with me to the camper where we became no wiser after a more thorough look at the collected parts. The 2S2100 lipo battery had taken a serious punch but still indicated 85% capacity, and first was allowed to sit idle on the grass at some distance from the camper, before I inserted it in a fireproof pouch for transport. I removed the receiver which together with the satellite looked unharmed, and the 10Amp CC BEC was still connected to the instrument panel switch and receiver. I already had made my mind up that after this terrible loss I wasn’t going to fly my Ka8b anymore during that weekend, and staying at that field any longer would only make it worse in my mind. In less than half an hour, I had packed everything in the camper, and contrary to the people around who told me I should stay, I said goodbye and prepared to leave.

The tow pilot must have felt some remorse, because for the first time during our stay he detoured to talk to me. After he initially thought I hadn’t disconnected, he now revised his opinion and told me he had positively heard my disconnect switch noise on my transmitter. I was glad one of our club members also heard when he commented he might have towed too fast for such an old glider. I got another stab in my chest when he casually said it was about time I bought a larger glider. Even not being able to swallow, I tried, and didn’t react, but inside I was fulminating. 24 hours before, I had told him why a 4m glider was already approaching the limit of my apartment, and that my interest were the restoration of worthwhile classy secondhand gliders in quarter scale, and fly them stately for the image. I have no interest in investing large sums of money in a modern glider I cannot manhandle, and definitely not just to follow the trend of exploding engine sizes of the towplane engines. Every minute I stayed longer or talked to people, I had more and more problems containing my tears. I hardly could swallow or talk anymore, so I quickly drove away.

During the 90 minute drive back, I felt like a zombie on autopilot, continuously thinking about everything concerning my beloved glider and that recently embraced aspect of model flying. I had invested so much time, money and energy into it lately, and I now doubted the future. The traditional wooden Ka8 was delicate and still had to undergo a full restoration to be trustful. The Twin Astir has a lot of work to be done, and the communication with the only German still able to deliver the essential canopy mold are very laborious since more than 2 months. Back home the receiver and satellites powered up, the variometer has a flashing light and transmits on the frequency of handheld, but doesn’t self-test or produce any sound anymore. When I add up the 400 euro purchase of model and parts, the 150 euro for the receiver, 250 euro for the professional paintwork and many meters of vinyl, 250 euros for the variometer, I see that 1000 euro of material and months of work have been wasted because of somebody’s testosterone driven ego to fly steeper and faster than others, in total disregard of the weakest link of the combination. I am furthermore convinced he also wanted to show me an airline pilot could fly as spectacular as a fighter pilot. Yes, he and his model are capable of making zoom climbs like an F104, but a Starfighter doesn’t tow 30 year old gliders doing it.

To say I am disappointed about those latest developments is an understatement. For the moment my plans for a nice summer attending family atmosphere model gliding happenings have been shelved for at least another season. I will take me some time to recover (mentally) from that avoidable mishap, and it again proves that you cannot trust anybody just because of their reputation or experience. It also proved for the umpthieth time that model flying should be considered as serious business, as opposed to fooling around for a hobby. If my glider had fallen on horse-riding people on that agriculture road, or a farmer on his land, those people wouldn’t have survived an impact on their head. My model only weighed 5kg, and during the last glider meetings I saw 3 other even heavier gliders plunge down at terminal velocity, and can only have nightmares thinking of a combination of a 50 pound high-powered towship, entangled to a 25kg 8m glider coming down onto people or property.

Why are testosterone driven beings always forced to push their speed, size, power etc into absurd corners. A few examples of that are visible every day, a neighbor of mine drives every day to work with a BMW M5, it sounds like the (old noisy) formula one cars as from startup, I even don’t need an alarm clock since. Others drive monstrous Audi Q7 or BMW X6 cars into town. In what kind of society do we live? Is everybody only concerned about themselves anymore? Is everybody supposed to just follow (pun intended)? Doesn’t anybody feel responsible for their acts anymore? Poor world, poor people trying to integrate, poor me who after the age of reason doesn’t understand the world anymore.

A day later I got phone calls and e-mails from people who had either seen or heard of my mishap. Apparently a few other very experienced tow and glider pilots had been watching in terror how I got pulled up at a much too fast speed and people spontaneously contacted me for support, even offering me the use of one of their gliders so I could continue attending the summer meetings. I was really touched by so much human feelings by people I only learned to know a few weeks earlier. On the other hand, nothing can push me back into that direction until I feel ready for it, and only time can heal those scars. Their stories about previous mishaps resulting from what only can be called reckless model-flying by that towpilot came too late, and will never resurrect my beloved Ka6e model, nor somebody else s towship and glider that were lost because of his attitude.

Multiplex Ka6e, R.I.P and thanks for the approximately 50+ peaceful flights you gave me.
Last edited by BAF23; Jun 14, 2014 at 09:33 AM.
Jun 14, 2014, 10:59 AM
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Phaedra's Avatar
It's really sad to see that people don't want to take responsibility for the damage they cause to others, that is the first point. It's very nice to see that other club members show some empathy and compassion in this nasty case, but the tow pilot truly is an example of what drove me away from the aviation world, namely egos that become proportional to size of the planes they fly (in auto-pilot mostly).
You can write a thousand books and a gazillion of procedures on how to do things, but if you don't apply them, it's pointless. Those people should set an example, but instead they are just a caricature.

I really feel very sad reading this, and angry at the same time because this tragedy could have easily been avoided just by applying a minimum of the rare commodity called "common sense".
I really hope you soon have another beautiful bird like this in the sky again.

Jun 14, 2014, 02:40 PM
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jetpropdlx's Avatar
Sad, to read about your Ka6e,
Try to get over it, by remembering al the fun you had flying with this and other gliders and al the nice people you did met while attending at those glider -tow events , but try to forget this one person behaviour .
I know who your talking about, and yes he thinks Big(gs), but personly i am suprised about his discribed towing , knowing he did tow very delicate gliders in the past with adapted power and speed.
I was a member off Biggs from the beginning until a few years ago , because my gliders didn't grow (as mutch as some of the ego's, of some new members)and didn't had time to go to the biggs events , I decided quit my membership . (still going to a few events where they also attend)
Jun 21, 2014, 09:10 AM
Registered User
I am very sorry for the loss of your beloved K-A6E. While it seems the tow pilot gave you a wild ride, there is responsibility on the other end as well. Number 1, You have a tow release, and if you don't like the way the tow is going you can release anytime you want (provided you have at least enough altitude to bring the model home safely), and if you feel you wouldn't be able to release with so much tow line pressure, you need a more powerful release servo. I see many persons think they can put a small servo/and or release mechanism in their model, when in fact at times there are enormous loads during the tow. Number 2, you and the tow pilot should have a conversation before the tow about what kind of tow you want and you should also keep conversing during the tow, if the tow pilot refuses to listen to you (it sounds like he has issues) then get off tow ASAP. If I am not familiar with a tow pilot, I ALWAYS watch him tow a few others first to observe his style and skill towing either large or small models.
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Jun 21, 2014, 10:24 AM
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Originally Posted by s2000
I am very sorry for the loss of your beloved K-A6E. While it seems the tow pilot gave you a wild ride, there is responsibility on the other end as well. Number 1, You have a tow release, and if you don't like the way the tow is going you can release anytime you want (provided you have at least enough altitude to bring the model home safely), and if you feel you wouldn't be able to release with so much tow line pressure, you need a more powerful release servo. I see many persons think they can put a small servo/and or release mechanism in their model, when in fact at times there are enormous loads during the tow. Number 2, you and the tow pilot should have a conversation before the tow about what kind of tow you want and you should also keep conversing during the tow, if the tow pilot refuses to listen to you (it sounds like he has issues) then get off tow ASAP. If I am not familiar with a tow pilot, I ALWAYS watch him tow a few others first to observe his style and skill towing either large or small models.
I agree that I should have released, but please consider the fact he is probably the Benelux tow-pilot with the most experience, and I had at least 10 recent tows behind his previous similar aircraft with less power, none of them being difficult because he always towed so well. Who am I, only being towed since a year, to doubt his judgements? I kept in tow until we at least flew straight (but still climbing) under the first cloud we encountered, so I wouldn't lose sight of my glider anymore when walking to the glider pilots box.

My release mechanism worked flawlessly even under tension, also that time, it just was me who was terrified so much during that very fast and steep tow, that I concentrated too long on staying behind instead of cutting my losses (pun intended), and watched in awe without being able to talk. Yes, you therefore can put the final blame on me if you wish.

I also realize a 30 year old second-hand refurbished glider might not have been strong enough to endure the intense consecutive flying I did at glider events. I am therefore considering carefully what I will replace that Multiplex model with.
Oct 10, 2018, 09:42 PM
Registered User
If its any help, another RC modeller in innsbruck has just offered me his KA6e multiplex. it is also finished in yellow. would you like me to put you in touch? Very sorry your loss, Marcus
Oct 11, 2018, 01:28 AM
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Hi Marcus,

If Innsbruck were closer to Belgium I might be interested. Size plus the delicate built of the wings makes it expensive and difficult for shipping. I pass along Innsbruck around March every year underway to and from skiing in Italy, but that is still half a year from now. Thank you for letting me know but I'm afraid purchasing that one is impractical.

Happy landings, Laurence

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