Mój model SZD-10 Czapla

[ultralajt]

Newest video taken from "aft seat" of Czapla!

 

It was a TURNIGY mini camera.

 

Enjoy the ride!

 

 

 

Regards!

 

Mitja

[ultralajt]

And another movie with flight No2 and 3.

 

 

 

Mitja

[ultralajt]

Another aerotow meeting is behind me and my Czapla!

 

Now we are able to soar in thermals! It is a great pleasure to soar with Czapla!

 

I made a "poor man variometer"

I simply use my old electronic Hang gliding variometer, extract electronic from the casings to make it lighter and wrap it in streech foil. (to prevent some short circuits and smoke)

Then I bought a cheap two way radio pair (walkie talkie) in a market (cheapo...29€complete pair with charger, reay to use). I also dismantle one radio to make it lighter and attach a servo that operate radio transmitting button. This servo is connected to a tow hook channel.

 

And how it works?

 

During a flight I simply use tow hook channel swich to switch on or off the radio (walkie talkie) in the model cockpit. If model is in the rising air, variometer beeps and rawalkie talkie transmit this sound to my walkie talkie. I use headphone in the ear, not to distur others with BEEP-BEEP-BEEP.. souns.

 

I think it is clumsy system, but work well and afterall it is more affordable as buying one of commercial variometers, that costs 300€ and more.

 

 

 

Mitja

[ultralajt]

Hi!

 

A brief insight in today`s aerotowing event held at the airfileld very near to famous Postojna Cave.

 

 

 

Mitja

[fischer8]

Beautiful flight.

[ultralajt]

Beautiful flight.

Another story, made from photos that my friend Uros captured:

 

 

 

 

 

 

Enjoy!

 

Mitja

[ultralajt]

Last saturday! Aerotowing event.

 

 

 

 

 

 

 

 

 

 

 

 

 

Videos on youtube:

 

Part 1/2:

 

part 2/2l:

 

Using homemade assembly of paragliding vario and cheap walkie talkie, I manage to stay up long time and soar in thermals almost to the edge of visibility. Czapla maybe looks boxy and draggy, but it soar in thermals amazingly well! Probably it is so because of low wing loading and gentle flight performances. Also the circling can be done very tightly, so one can use the best of the thermal core and climb up fast.

 

 

Enjoy the pictures and videos!

 

Mitja

[ultralajt]

Today, my beloved SZD-10 Czapla left my house and ended in the hands of new owner.

 

I know she is in good hands now, and I am looking forward to meet her next year on some aerotowing events.

 

I am sad and happy for her at the same time..... very strange and odd feelings for me as this was my first model that left my house.

So, I think, this is an official end of this thread from my side.

 

Now, back to the drawing board!

 

 

Mitja

 

 

[ultralajt]

Probably the last video with my Czapla:

 

 

 

Mitja

[Callab]

Very nice footage. Looks like you miss your glider.

[ultralajt]

Very nice footage. Looks like you miss your glider.

Yes I do.

 

It is like a health! You start to appreciate it when is lost

 

Thats why I already start to design a vintage scale sailplane from ex Yugoslavia, CIRUS HS 62 from 1962. It has some similiraties with Czapla: biplace, forward sweept wing, boxy fuselage, large rudder.... and it is also unique and cute.

 

At this moment I am working on the drawings of real sailplane, as there are no useful drawings to find. Only information available was a very bad 3 view drawing, without proper propotions. Luckily I got help from Cirus designer himself, and he help me to reconstruct the glider structure, so I am able do make better drawings than these available on old books and some Internet sources.

When I finish drawings completely (90% done already now), I will start to make drawings (workshop plans) for a model in 1:4 scale , which gives me a wing span of 4,25m.

 

Cirus is also like Czapla very apropriate sailplane for a RC model because it looka liek a giant model, with ample tail and controll surfaces. I believe Cirus will also have very nice and gentle flight performances.

 

Some graphical informations on that project:

 

 

So, it looks that next year will be very busy in my workshop....

 

Regards!

 

Mitja

[vik]

Mitia,

 

I didin´t know the Cirrus - it looks like a wonderful scale object. With great proportions and easy to build.

 

I would just like to ask you about the Czapla. Can you say something more about the performance. Circling and rising in thermals was very good, It think the chord and the low surface/weight ration is is responsible for this. Its also known that forward swept wings circle very well. But how about the penetration/glide angle and speed?

[ultralajt]

Mitia,

 

I didin´t know the Cirrus - it looks like a wonderful scale object. With great proportions and easy to build.

 

I would just like to ask you about the Czapla. Can you say something more about the performance. Circling and rising in thermals was very good, It think the chord and the low surface/weight ration is is responsible for this. Its also known that forward swept wings circle very well. But how about the penetration/glide angle and speed?

The penetration is not comparable with plastic scale gliders. It is somehow "worse", but you can advance against the wind pretty well. With this type of sailplane you must not be in a hurry. It is best to relax and not "push the limits" . When you push Czapla to fast flight, first it loose some height, but then sudden starts to glide better and flat. It looks that airfoil get proper reynolds number then or what.

I made loopings with Czapla, rolls..2 in a row, immelman and ranversman.

Circling in tight and slow turns is possible because of the forward sweep wing and 3°of twist. Czapla resist very much to drop the wing tip.

If you pull Czapla to very stall, some strange thing happens. It dont drop the nose, it dont drop a wingtip, but it starts kind of "parachuting"... high angle of attack steep glide angle, but totaly controllable. A short push of nose down and few moments later Czapla fly normally again.

 

Mitja

[vik]

Mitja,

 

which section did you use?

I bought once a Hü-17 in 1/3 It das the original Gö-535. It was a nightmare to fly (thickness 16% over 5% camber) a wing shape like a Piper. I sold it although it was a beautiful model to look at. Made of birch plywood. But since then I´m very carefully with models with a large wing area. I like the Czapla, and the only thing I´m worry about is to much induced drag from the large wing.

 

Can you say something more about the Cirrus. I googeled a bit and found basically your treads :-)

Do you have the original glider drawings? The proportions seems to be very very good for a large scale model.

[ultralajt]

Mitja,

 

which section did you use?

I bought once a Hü-17 in 1/3 It das the original Gö-535. It was a nightmare to fly (thickness 16% over 5% camber) a wing shape like a Piper. I sold it although it was a beautiful model to look at. Made of birch plywood. But since then I´m very carefully with models with a large wing area. I like the Czapla, and the only thing I´m worry about is to much induced drag from the large wing.

 

Can you say something more about the Cirrus. I googeled a bit and found basically your treads :-)

Do you have the original glider drawings? The proportions seems to be very very good for a large scale model.

Czapla uses Go 549 airfoil. It was thickened to 18% at root. As wing chord at root is 35 cm long I just use original airfoil and thinned it to 14% as program profili 2 predicted quite satistactory performance. Go 549 is a very good airfoil. Using much thinner airfoil will ruin the apearance of the glider. There are a line of MS airfoils (look at retroplane.net) that are also thick and could be used on vintage scale sailplanes. As I did not notice any remarkable difference I use "original".

 

 

Behind a Cirus HS stands a very interesting story. Its streamlined version (fuselage not from steel tubes, but monocock plywood shell), was very popular here, and even win one international competititon amnong biplace gliders.

As its designer was not perfect for comunist party of former Yugoslavia, he escape to France. In France he design gliders at Breguet, then design some CAP aerobatic two seaters, and became chief designer of space rocket ARIANE.

 

There are no useful documentation for Cirus sailplaen left, except some 3 view drawings, but of such bad quality, that one cant use them for making a scale glider.

 

So, I start to research for any information about this sailplane. I manage to contact his designer, and with his help make reconstruction drawings of this interesting sailplane.

 

At this moment I already start to make RC scale model drawings. 1:4 scale, 4,25m wing span.

 

I will use HQ3/13 airfoil.

 

Mitja

[vik]

Mitja,

 

I have heard about many models which fly with the Gö 549. Or Gö-549 transition Gö-676 - which has been used in the Jacobs Weihe and Meise. (1/3 scale Weihe or 1/4 scale Meise)

But when you look at the polars of modern sections like the SD7062 or MS3retro are better, especially on low Re numbers. It is possible, that the good results of the modern sections become worthier on real build wings.

[ultralajt]

Mitja,

 

I have heard about many models which fly with the Gö 549. Or Gö-549 transition Gö-676 - which has been used in the Jacobs Weihe and Meise. (1/3 scale Weihe or 1/4 scale Meise)

But when you look at the polars of modern sections like the SD7062 or MS3retro are better, especially on low Re numbers. It is possible, that the good results of the modern sections become worthier on real build wings.

Glider with wing loading of about 75g/dm2, and max lift coefficient of 1,45 achieve minimum speed at about 30 km/h.

At average wing chord of 28 cm, at this speed, reynolds number is about 150000.

(This is only rough estimation, as right now I dont have time to run and present excact numbers... they should be even a bit better than these presented above.)

 

If you compare some airfoils, you will notice, that Go549 is not bad at this re number and max lift coefficient...if you compare the drag coefficient at that max lift.

 

 

 

But of course, drag of wing is not just a profile drag. It is also an induced drag, which goes up with CL square.....

 

Mitja

[vik]

Some time ago I calculated some polars for the Orlik and the Komar in 1/3 scale. These are wing only polars. It´s w/o any fine tuning in therms on handling ( tip sections, twist etc.)

 

I used the SD7072, the MS3-13, the HQ3/13 the FX60-126 and added the Gö549 yesterday.

 

Orlik polars: (the Orlik has a "normal" wing shape - the Komar has very narrow wing tips) you can see how good the MS3 is. It has a very wide range of speeds where it has very good sinking.

For the Orlik the choice is between the SD7062 and the MS3. It depends if you want a faster or slower model. The yellow curves is an 1/3 SZD 56 Diana2 :-)

 

For the Komar it is a bit more difficult: The choice would be rather between the HQ and the FX. The Komars were very light and it was knwn to be able to climb in almost nothing. The Problem here could be the low Re numbers on the tips.

 

The top right is the sink polar

 

 

[ultralajt]

 

It looks XFLR dont like Go 549.... :mrgreen:

[vik]

Yes :-)

 

when you see the polars they are horrible. Especially on low Re. Maybe I should smooth the foil a bit. I remember with HQ you have to do the same.

 

But it´s s strange: in profili the foil seems to be better.