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Jun 03, 2013, 05:17 AM
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Stampe SV4b

Since I had my first real aircraft ride during an open door in 1967, as passenger in a Belgian Air Force primary trainer Stampe and Vertongen SV4bis tail number V41, I had a strong penchant for that charismatic biplane. In 1972 those trainers were obsolete and got replaced by sleekly SF260M Marchetti trainers, and most were acquired by civilians. In 1982 V41 flew occasionally from the civilian airfield I used during weekends. It remained completely original except for sporting an additional civilian registration OO-LUK. I flew it many times over the years, and lately (2013) is in the hands of a former air force colleague pilot, having been restored to its former glory and being kept immaculate.

No wonder I wanted to have a model of it, but unfortunately the few kits on the market were either too large or out of production (Svenson), and all were for heavy petrol engines. In 2011 a fellow club member bought a second hand Stampe on the internet. It had a two stroke engine that had soaked the front, was missing struts and parts of wing covering, and most essential fittings were either unglued or poorly repaired (after a crash?). The landing gear obviously had absorbed serious hits and was pointing anywhere but straight. The cockpit and interior had the looks of a battered toy. But I wanted it so much I was able to persuade the new owner to electrify it, produce the missing bits and selling it to me so I could further finish it to my desires. It wasn’t cheap, but getting a 6ft wide balsa scale biplane I craved for was worth it. This is the condition it was after the internet purchase.

After a few months I collected the much enhanced model. It now had interplane struts, adjustable flying wires, a 1000W 500kv engine, a 90A ESC, new better shape front cowling and refurbished Oracover panels. Not feeling ready to fly this big delicate biplane yet, I slowly made the cosmetic changes to make it look like my beloved V41. Unfortunately each time I got closer to detail things, I discovered (sometimes major) additional (structural) discrepancies.

The wood and metal parts of the cabane struts holding the top wing over the fuselage had separated or just held together with paint over filler. The gear springs had elongated so much they had no more practical use, the top wing had inverse washout and would for sure lead to premature tip stall. Installing washers on top of the front cabane attachment and leaving the model during all winter with cloth hangers pulling down the outside wing front with the weight of heavy pullovers finally corrected that critical error.

New wheels were purchased to eliminate axle play and allow the SV letters on the covers. Those were Piper Cub wheels where the CUB letters sticking out have been Dremeled off. Getting the thick wheel struts to point in the right direction and angles was difficult because they couldn’t be removed (being both screwed on and epoxied to the frame). 4mm axles don’t bend easily and exercising torsion required a delicate balance between high torsional iron force and minimal wooden frame impact. To power the aircraft I measured the front compartment which is accessible by pivoting the left and right metal side panel, just as in the real Stampe. The former fuel tank space was ample but in order to be able to remove the power pack I opted for two 6S2300mah 30-40c batteries mounted side by side in parallel. Those weigh each 460gr and had to be secured so they couldn’t move around during aerobatic maneuvers. Being unable to reach inside that compartment I glued pieces foam to block any movement, but still allowing them to slide in and out when a center piece is taken away, and allow air circulation around them for cooling.

The 90A (120Amax) Esc had been mounted in an unventilated compartment above the batteries and I didn’t like the thin 14AWG parallel cable setup, and also was afraid of sparks connecting the 22V batteries through Deans plugs. Taking out the Velcro attached ESC resulted in the whole floor coming along, that balsa still being soaked with former oil residue. I replaced all cables by thicker 12 AWG and used EC5 plugs all around. The ESC can now be lifted to change the batteries, but for flight is fastened at an angle in the direct slipstream behind the nose cooling intake.

To power the AR500 receiver and heavy servo’s I use a separate 2S950mah battery mounted further back, switchable through a slider protruding on the left cockpit side. Extensive testing of the servo’s revealed the rudder one to be sometimes sticking to the right. The one that had come off from the throttle also was unserviceable and an internet search showed those were expensive strong Multiplex servo’s from the early 80’s. Luckily I found 5 such servo’s on German e-bay and got good spares for little money. The metal gears on those 80Ncm servo’s seem suitable for a BMW car and one servo weighs a hefty 82 gram I wonder how much juice they need and will make the first flight a short one to measure the battery after landing. Both rudder and elevator servo's were mounted on hardwood crossmembers. When unscrewing the first I noted the one of the crossmembers had become unglued against the sidewall and had much play, leading to the other one having to absorb all the forces which would certainly have led to disaster after a while. There is only one servo in the bottom wing, actuating all 4 ailerons through pushrods and bellcranks. All servo’s now work well but seem to have a rather undefined neutral point, depending from which direction it comes. Trimming the airplane out will not be easy but just as the real Stampe, It will have to be actively flown at all times.

When I got the model the interior and canopy were a disaster. The instruments showed pinball machine type panels labeled on-off-danger and the hood was silver inside and out, with much repaired attachment holes.

I used front and back seats pictures taken in the real aircraft, with correct positions of magneto switches and different attitude indicators. Pilots were further painted and the hood fixed on simulated side rails and yellow opening handles on top. Interior was painted the correct color and throttle and mixture levers glued on top. The result is more than pleasing for the eye.

Having no indications of correct CG position I had to use some ingenuity. The Stampe has 4 individual swept and staggered wings. I thus marked the 25% MAC position on each wing and interpolated that onto one common CG for the complete airplane. My Sig balancer could not be used because either the landing gear stood in the way, or the complete weight would rest on the oracover or thin wing ribs. I thus extrapolated the CG position on the top wing and was able to lift it with the fingers just behind the recess over the front pilot. This airplane is big and needs specific methods.

Weighing the airplane posed similar problems so I subsequently noted the figures on my precision scale after weighing each wheel (also tailwheel) pressure with the airplane in a horizontal attitude. Even with the batteries in position this huge airplane still tips only 4,7 kg which relates to a 70cm2 wing area with a loading of about 68gr/dm2. Those encouraging figures, combined with the training I did exercising biplane techniques on my WW1 SE5a and WW2 Stearman PT17 foamies, gave me sufficient confidence to attempt flying my Stampe on a calm day . My biggest fear remains that inside the fuselage some potential unseen structural problems are a potential for disaster. Assembling the model from transport configuration takes more than an hour (struts and flying wires etc). All crumpled surfaces have been ironed out but that also was very difficult because there are so many different materials used (each stretching at different temperatures), and even repairs or reinforcements made with transparent scotch tape in some places. I balanced the 18x6 prop which according to my calculations will make her fly at a realistic 56km/h. I also have a 18x10 prop but that would probably propel it too fast and cause more strain on the ESC.

My Stampe SV4 is anything but perfect, but fulfills my desires of having a (model) of the aircraft that influenced my life so much. I liked flying the real Stampe more as any other airplane in my life (including the best jetfighters). I wonder but am also apprehensive of how the model will behave. During summer 2013 I will testfly her and report about it on these pages, in the meantime she teases my eyes and heart at home.
Last edited by BAF23; Jun 04, 2013 at 02:59 AM.
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Jul 04, 2013, 01:37 AM
even monkeys can do better!

3e stampe en oldtimer flyin

Dear BAF23

What a joy to read that you are a stampe enthousiast.
So am i for that reason im organising an yearly event.
With the goal to get as much as rc stampes together as possible
Here is the link
You can participate bij simply following the instructions in the link
Hope well meet on that day and we can talk about our beloved aeroplane
Regards pascal
Jul 19, 2013, 12:50 PM
The sky is the limit
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First flights

With a few days of calm weather forecasted in July 2013 I took the bull by the horns and after a detailed last minute inspection, transported my Stampe to the airfield. Assembling it on the field was a bit laborious and I requested 3 experienced pilots to check my model and experimental CG position location. After they confirmed everything visible to look fine I performed some powerchecks and taxied out to the runway. I already had decided to takeoff on the tarmac, but land on the parallel grass. After a last control check next to the lined up aircraft (not in the too far away pilot box), I looked at the windsock which indicated light wind but continuously shifting between left and right full cross.

I waited for a lull, then slowly opened up the throttle in anticipation of a swing that never happened. As the model broke ground with little over half throttle and not yet in level attitude, I continued opening up slowly but was surprised the left wing started to drop. As corrected by applying right aileron and a bit of up elevator, I experienced a serious wingdrop to the right at less than 1 meter altitude. Without hesitation I opened the throttle completely and used all my experience to fly out of that precarious situation without stalling again.

To my surprise full down trim was insufficient to correct the pitch at safe altitude, and only 3/4 down elevator on the stick kept the Stampe from raising its nose. I quickly turned downwind and elected to land after a short pattern to correct the anomaly before further flight testing. In downwind I gained sufficient feeling in the limited elevator control to attempt a landing, and after a 180° turn, I lined up long finals with the grass strip to which I had moved, and flew a steady powered descend with sufficient speed to keep the elevator effective. I touched down in front of me in a deliberate 2-point attitude and after a slight bounce, the second touch kept it on the ground. Only then did I close the throttle and allowed the tail to slowly settle.

Taxiing in my heartbeat came back to normal and I was glad to have completed that very short maiden without a scratch. Back in the pits I analyzed the situation. As I did not want to bring the 25% CG forward any more because the nose would certainly tip over on takeoff or landing, and the tailplane incidence could not be adjusted, the only quickly feasible solution remaining was to note what down angle the elevator had with trim fully down and stick 3/4 forward, then after neutralizing the stick and trims again, mechanically adjust both elevators to the noted down angle. I needed help to slowly rotate both rusty and often painted over quick link adjusters without breaking them with to the extreme twist force I had to apply.

With the batteries barely used I started out for a second flight without charging, being prepared to catch anything fast, and controlling the aircraft to first reach 2-point attitude before allowing it to get airborne. My TLAR (That Looks About Right) adjustments had been spot on, because after a normal takeoff and gradual climb, I was able to lift both hands in the air for 5 seconds on downwind, to prove it flew nicely trimmed. Having no idea of battery consumption I just was glad it flew nicely and after one circuit decided to land and this time I could use my elevator the normal way to flare.

Post flight investigation revealed still 67% in the engine batteries, and 87% in the flight battery. I thus easily could fly about 8 minutes on the next flight (after charging). On the other hand, the ESC felt too warm to my likes, as well as the engine. Time to quit, disassemble the Stampe, and take the model home for modifications. Where the rectangular cooling hole below the spinner had been painted over to represent the real more oval cutout, I used the Dremel to cut it out completely even enlarging the orifice slightly over the real proportion. I also removed the prop and further enlarged the engine shaft hole. The 18/6 prop got replaced by a 17/6, I further bowed the engine access panels at their back, to have better heat exhaust, and relocated the ESC vertically just behind the nose cooling hole. All previous changes were made to ensure cooler operating temperatures.

A few weeks later I took her up for a third flight that lasted about 6 minutes. The Stampe flew as on rails and gently stalled without wingdrop tendency. After the 45° dive CG check (showing the desired tendency to slowly recover by itself), I started maneuvering and flew some loops, Cuban eights, barrel rolls and straight rolls. The latter revealed too little roll rate for a 4 aileron equipped Stampe. After flying two stabilized low approaches I made a textbook landing without bounce tendency, and very smooth touch. This time batteriesn ESC and electric motors all were barely warm to the touch. Next flight will have to wait till after the aileron throws will be mechanically augmented, and if all ok, I will explore the spin characteristics and attempt my first landings on the tarmac.

When I was complaining to fellow club members it would take another half hour to dismantle the Stampe and secure and protect the fuselage and wings for transportation, one guy suggested I attempted getting it in one piece in my camper. The door being half an inch more narrow as the height between the wheels and top wing didn't facilitate things, but with some dexterity and caution, I managed to get it in a 3 point attitude on my back bed, where it can stay till I fly it, or need my bed. The engine batteries can be loaded home, but with the flight battery presently only accessible by removing the bottom wing (which in turn requires top wing, struts and flying wires to be removed first) I plan to relocate that battery in the much more accessible nose compartment. I took it out a few days later for a family picture, together with some of my other RC planes I stock fully assembled (except for wing removal of the ASW22 glider) in my camper to fly on a weekly basis.

I'll keep you informed on this page regarding final adjustments, pictures or movies becoming available. In the meantime you can watch an early video of a proving flight during a windy day.
Stampe compil flight 2 (2 min 58 sec)
Last edited by BAF23; Dec 27, 2014 at 06:58 AM.
Jul 27, 2015, 07:36 PM
The sky is the limit
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Thread OP

Making the Stampe better

The model being too fast for scale, I started using 5S batteries, and even was capable of shoving then through the enlarges air intake, greatly facilitating battery changes, but also allowing them to be charged while still in the nose. On two times 5S2700 in parallel i Fly about 7 minutes, using only full power for takeoff and during portions of the vertical maneuvers. Speed and power to weight ratio look very scale and the model docile in handling. At our club, I mostly takeoff on the tarmac, but elect to land in the adjacent grass. Taking so much space when assembled, I rarely take it along, also because it is not very suitable for crosswind operations on our 03-21 restricted takeoff and land direction.

In the meantime I used the few flights I had with it to perfect a standard scale-like routine including mild aerobatics and a spin, but have trouble with the execution of the stall turn. Somewhere in my head I still have the tendency to make it to the right as I had to do on the real Stampe because the the prop rotated the other way around (the British Gipsy Major staying in line with driving the opposite side of the road etc). That model being rare and desirable, I don't use it frequently but when it flies and on the ground it is a model most people can't take their eyes off.

August 2014 I attended a private venue of retired Belgian Air Force pilots on the now abandoned airfield of Goetsenhoven, the sole operating base of the BAF Stampes. Not only that, but they had invited 5 real Stampes flown by ex-BAF pilots to offer rides to others who all had flown solo in SV4's, but more than 45 years ago ! They also invited me with my model, but the real V41 OO-LUK unfortunately was unserviceable that day and I only was able to make pictures along other Stampes.

I had a limited time window during which I could fly, and the wind was blowing fully cross on the available axis, but with the 3-times world champion scale RC flying Philip Avonds next to me, I took her up and performed some basic aerobatics before bringing her back to terra firma in one piece.

It was one of the few flights I performed in 2014 with the Stampe, but it will remain grafted in my memory forever. Such a historic framing will probably never happen again, and I had been actively part of it, confirming I was on a good track with my RC flying.

Although I hardly flew the model during the last two seasons (too worthwhile to risk?), an intermediate inspection in 2014 revealed that the motor was loose on the X-frame, making a second flight at EBTN probably would have ended in a disaster. That problem normally is easy to correct, but the guy who installed that assembly used a lot of putty type material on the long threaded engine mounts to keep things permanent, before building the rest of the nose permanently around it. Needless to say, it took me hours of swearing, dismantling the nose, grinding away wood and metal, and pure frustration before I was able to access the back of the X-frame to tighten all the screws without being able to remove the X-frame from the model, but this time using liberal quantities of blue thread locker in the process.

Early 2015 I switched to Taranis/FrSky equipment but didn't feel confident flying that increasingly valued model on a ridiculous piece of AR400 Spectrum receiver through a Spectrum DM9 interface in DSM2 mode on my new transmitter. Halfway summer I found some time and decided to make the full switch, combining it with an IRAN (Inspection and Repair As Necessary).

Since I was installing Shotsky diodes in my fleet to improve redundancy, I looked at the possibilities on this bird. Being already equipped with an Opto ESC and a Castle Creations 10Amp BEC behind a single external power switch, restricted the possibilities. Full redundancy could only be obtained by yet an additional receiver battery routed to a second BEC and either a second or dual polarity external switch. I finally opted for a simpler redundancy of only duplicating the 2S950 battery, by rewiring so as to connect both to the existing system by a diode ahead of the CC10 BEC. I know it's a gamble, but it's already better than before.

Although it was obvious that initially the model had been setup with separated servos for each elevator, somewhere during its life it had been modified within the now enclosed tail to operate from a single old Multiplex servo so the model only needs 4 channels. When hooking up the new receiver I heard that elevator servo making some very strange noises (although the movements were as commanded). Having been lucky to purchase a few of those old servos through a German second hand site some time ago, I didn't hesitate to replace it but then faced the problem of a servo direction that had to be changed and a servo arm that was mounted on a square pin that doesn't allow anything but 90° angles to be selected. Having already dismantled the canopy and rear cockpit to access the area, I became confronted with adjusting the pushrod length. I remembered having difficulty after my maiden to adjust it at the tail end, I thought it would be easier to do it at the servo end, only to discover that the quicklink had too large a diameter for the 2mm thread and separated much too easily. That could have ended in disaster and I was glad I hadn't flown it much before discovering that major flaw. Lubricating the nylon hinges and the old concentric nylon pushrods greatly reduced friction, and after a few hours of work I had all the tail feathers operating correctly and much smoother than before.

After finding places and ways to fasten the new equipment, I reassembled the parts, and for the first time since I acquired it, felt confident about the way to control it. Although the model looks extremely attractive from a distance, close inspection shows the glossy Solarfilm type covering to be both inappropriate and applied with bits and pieces, indicating many repirs. First concern now is getting the model back airborne with the new electronics, fine-tuning it, and eventually completely re-covering it wit Solar/Ora-Tex type of strong but realistic "fabric".

I do not post any additional pictures or movies, because the many essential updates all were done internally.
Last edited by BAF23; Jul 28, 2015 at 06:22 PM.
May 31, 2016, 07:40 PM
rc builder guy

need advice

was reading your blog about the Stampe.
I am building a Severson Stampe and am getting close to completion. just figured out that the tires that came with this half built kit do not have air valves.
I really need to know what size tires/ wheels really belong on this plane. if you have a clue, please let me know.
Jun 06, 2016, 04:09 AM
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Thread OP

stampe tires

Hi Larry,

The real aircraft has 500x180 size tyres that are kind of slicks and balloon shaped. The not 100% scale wheels I used on my model are for ease of purchase and use, and as you can see on the picture in the text with the 2 batteries next to it, they look acceptable and the disk can easily be modified to display the SV letters as per on the real flat (rubber) disk. On the real airplane the disk sits deeper, bolted straight on the rim but as said, my flying model needs practicable parts that only purists can identify as incorrect. My wheels are the 4"25 from Hangar 9's quarter scale Piper Cub.

Good luck
Sep 28, 2016, 10:09 AM
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The 2016 flight

It was already end September when I finally took the Stampe to the grass field of TMV Tongeren. A local school would be visiting at 14h and although I did not plan to fly it for demo, a discrepancy on the towplane's throttle servo meant that the demo of towed large gliders could not take place within the timeframe of the visit. I thus quickly decided to assemble the Stampe and fly it in order to have one more large scale model in the air. Not having flown that model for more than a year, I was a bit apprehensive with such an audience and cautiously taxied out.

Takeoff was uneventful and scalelike, after a few figure-eights I felt confident, climbed to a safer altitude and started some scale-like aerobatics. Loopings, stall turn, Immelman, split-S, barrel roll and aileron roll were combined and I was rather pleased of the results and concluded with a top-view curved pass for the bystanders and photograher Danny.

I then flew a square pattern to get acquainted with the local (wind) situation and environement but as I told another pilot not to fly till I was on the ground, I turned downwind to land sooner than planned.

Finals looked good albeit a bit high and I had a steady glide angle to touchdown.

With the steeper glide angle I flared a bit too late and the Stampe surprised me, leading to an unacceptable landing. Well after touchdown the model completely nosed over. No damage but to the pilot's ego , but I noted even full up stick did not produce much up elevator, something to remedy before next flight so I'll be able to keep the tail down after touchdown.

This probably was the last flight before a more extensive resoration and re-covering with Oratex somewhere in the future.

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