Biplane Aviatik

[Bernd Lewerenz]

Every now and then I also have to tidy up my hobby room. So I noticed how much pieces of balsa and plywood were lying around uselessly.Too little for a large model, but also too much to simply dispose of.Last winter, a colleague had brought a small high-wing monoplane and flew with it.It should be possible to realize something like this with the leftover material.While looking through my plans, I also found a suitable object, namely the Aviatik biplane by Jaromir Pipek.With a span of just under a meter, it would fit in my car when assembled, In my plan, a nitro engine with 2.5cm3 is still planned, but for me only an electric drive was an option. As the warm season was now over and so it was time to get started.

[Bernd Lewerenz]

The tail unit.

The rudder and elevator are made of 6 mm balsa strips and are shaped like a Focker from the First World War. It is quickly assembled on the foil-covered plan, using only wood glue.

[Bernd Lewerenz]

The fuselage

It is a simple construction consisting of two side parts, reinforced with 0.8 mm plywood in the front third.Lightweight 2mm plywood former are also used there, while 4X4mm balsa strips determine the shape in the rear section.In other words, really classic model making, which I always enjoy with a good cup of coffee.I know, you prefer tea.Once the basic construction was complete, the conversion to electric drive had to be considered.The motor mount for the burner was omitted; instead, the mounting cross for the electric motor was attached to the front former.

[martin collins 1]

Watching your build with interest 😃

[Bernd Lewerenz]

Adjustment of the wing canopy with + 2 degree angle of attack

[Bernd Lewerenz]

THe wings.

Bad weather in Germany and a good reason, to build the wing

  Upper and lower wings are both drawn in the plan and the only difference is the wingspan.The bracket for the undercarriage and the wing bracket are also positioned in the lower surface.First, 50 ribs had to be made from two, four and five millimeter balsa wood.😂 Since all ribs are the same size, a master rib made of 5mm plywood was sufficient.Admittedly a somewhat monotonous job, but better than housework.Once the wing connectors had been made, the construction of the lower wing could begin.

Due to the flat underside of the ribs, the four halves were quite easy to assemble.Both wings have neither spar webbing nor nose planking.The reason is probably the main spar, which is very thick at 12X5mm.Images later

Edited November 27, 2024 by Martin Harris - Moderator
Bernt - you might not realise that the first word in your reply is regarded as bad language so I’ve replaced it with “Bad”.

[Bernd Lewerenz]

Both wings are almost finished and are already taking their place; they are not yet attached and are therefore slightly crooked

[Bernd Lewerenz]

Sorry will avoid bad language in futur😇

[Bernd Lewerenz]

Adjusting the angle of attack of the upper wing of plus 2 degrees

[Jonathan M]

1 hour ago, Bernd Lewerenz said:

Adjusting the angle of attack of the upper wing of plus 2 degrees

 

The correct term is angle of incidence, i.e. angle of wing to fuselage datum line.  Angle of attack would be the attitude of the whole aeroplane, i.e. fuselage datum, to its flight path.

 

If the incidence angle of the upper wing is 2°, what will be the lower wing's angle?

 

Nice winter project by the way! 👍  What will be your electric power-train?

[Bernd Lewerenz]

16 hours ago, Bernd Lewerenz said:

Adjusting the angle of attack of the upper wing of plus 2 degrees

 

21 hours ago, Bernd Lewerenz said:

Sorry will avoid bad language in futur😇

 

[Bernd Lewerenz]

Hello and thanks for the tip. The angle of incidence of the lower surface is zero degrees.The tail unit also has zero degrees, so you can say that the angle of attack is plus 2 degrees altogether.The motor is an Extron 2712/26 KV100
Controller 30Ampere
Servos: 2X Master S766MG/MG= metal gears

[Bernd Lewerenz]

The undercarriage is being bent.It looks a bit weird, but that's the perspective.The undercarriage consists of a front and rear bracket with 2 mm steel wire.Then comes the 3 mm axle for the wheels.
Then everything is soldered

[Bernd Lewerenz]

The undercarriage is ready for installation

[Bernd Lewerenz]

Ready for covering

[Murat Kece 1]

looking very nice 👍

[Bernd Lewerenz]

Thank you, made from scrap wood

[Bernd Lewerenz]

Final work.

Again, classic model building. The fuselage was treated with pore filler and covered with paper, while the wing and tail were covered with Proficolour2 from Practical scale.

This film is ideal for vintage models.Two table tennis balls painted by my wife serve as pilot heads and look funny. They are also very light.The plan shows the emblems of the German Air Force and a machine gun..However, I have opted for a peaceful airplane.That's why I have attached flying doves to the fuselage and wings. I think that's better in view of the world situation. Now I have been waiting for better weather for the first start.

[Bernd Lewerenz]

Hello together,wich you a happy new year and allways happy landings.

My first landing with the Aviator on the first day of the new year was a disaster.The take-off was good, but in the air the model was not controllable.It staggered through the air and could only be forced into a turn with maximum rudder deflection.After about 30 seconds of flight the model crashed.
Frustrated, I drove home.Due to the low mass of the model, the damage was not serious and was quickly repaired.Now my ambition was awakened and I wanted to find the reason for the crash.The electronics were not the reason.Research on the Internet revealed that the upper wing of a biplane must always be set at a negative angle. The lower wing, on the other hand, must be set at a positive angle.With my model it was the other way around.You always learn something new, even at an advanced age.Now I have changed the angle of attack of both wings and increased the side thrus.Upper Wing Minus one degree, lower wing Plus 1Degree.I admit I'm a bit scared of the next flight, but as soon as a nice calm day arrives, I'll start the Aviator and report back.Keep your fingers crossed.

[Jonathan M]

Sorry to hear this was your experience.  But I'm not sure your diagnosis of the problem or the solution is correct.  One has to assume that the designer knew what he was doing and that numerous other examples of this model have flown perfectly well with the top wing at 2° and the lower one at 0° as specified.  (I've made several small free flight biplanes powered by rubber, electric, CO2 and diesel, which have all had the upper wing set at a slightly higher angle than the lower one - and they've all been stable and gently self-correcting if disturbed by a gust or similar.)

 

It's difficult to discern from your description why the model flew briefly as it did, but there could have been other complicating factors:

• did you build in any or enough down-thrust?
• how accurately did you measure and build the upper wing angle - perhaps there was some extra error that crept in?
• was the weight of the model within specification, and - importantly - was the centre of gravity in the right place (not too far forward or back)?
• was the powertrain (motor, lipo, prop) correctly specified?
• were the control throws adequate?
• etc

As indicated above, I come from a free flight background.  Here if one small change is made in trimming a model (say power, prop, side- or down-thrust, nose- or tail-weight, wing warp, rudder deflection, etc) then everything else is effected.  The process of trimming is therefore a careful one of changing only one factor at a time then carefully observing the flight behaviour before increasing or decreasing that change if necessary, then making a small change to any of the other factors that could be effected.

 

Edited January 6 by Jonathan M

[Bernd Lewerenz]

Thank you very much for your support.

The down thrust is 4Degree( my Kapitän had 3degree and this was to litle)

To measure the angle of attack I use the setting angle gauge from Robart and an additional electronic one with digital display, both displays were about the same

The weight is about 800g ready to fly.

The engine is from my Kapitän and both models are similar

Airscrew is 9X6

I understand your arguments very well, because Jaromir Pipek is a well-known model maker in Germany.On the other hand, my new information about the angles
comes from Ralph Müller, who has also developed many models and was very shocked by Plus 2Grad. So the only thing left is learning by doing.

If the weather is good, I'll try a new start and report on it. let's be honest, if everything always works well, it gets boring too.

 

 

[Jonathan M]

Interesting, thanks for the extra detail.  Good luck with the next test flights.

[Bernd Lewerenz]

Last week I flew my Aviatik with the newly adjusted angle of attack.And this time it worked: the aircraft flew without any problems and was stable.After a few rounds, I wanted to land.During the landing approach I was blinded by the very low sun.As a result, I flew too low towards a small wood and the model landed on a tree at an altitude of about 1 meter.At almost 76 years old, I no longer climb trees.So there was nothing left to do but cut down the tree. It was dead anyway.The fuselage was destroyed, but the wings remained intact.That's why I have now mounted the wings on my Kapitän and corrected the angle of attack there too.Now my captain is also flying stably and I at least have something from my aviation.We model pilots are all familiar with this.Sometimes you have bad luck.But never mind, my next model is already in the works. It's a Klemm25 from Krick.

[Bernd Lewerenz]

Sorry, I mean 10m of course