Designing and building Polikarpov Po-2 biplane. (Full Version)

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mihaj -> Designing and building Polikarpov Po-2 biplane. (3/1/2004 6:15 PM)

Hi group!
Since I'm half way into the design process of this "legendary" aircraft, I thought that it may not be a bad idea to show how I design my models. In addition to that I'd like to get some feedback or advice from you.
Personally, I think Po-2 is a grate alternative (as a modeling subject) to DH Tiger Moth. Plus, this plane has very HEROIC history.
I'm sure that most of you know about it but check this out. I'm sure there is more:

http://www.samolet.co.uk/femalefaces.html
http://pratt.edu/~rsilva/witches.htm
http://www.svogroup.com/itsrussian/catalog/popova.htm



mihaj -> RE: Disigning Polikarpov Po-2 biplane. (3/1/2004 9:24 PM)

As any of you scratch-builders I started with some 3-view drawings from www.airwar.ru
Good thing I didn't have to scan them.[:D]
Next step was to vectorize them. I was using WinTopo software to do that. It outputs .dxf that was easily imported into my CAD software. There was a fear amount of time dedicated for "cleaning" those drawings but the benefit is that I was able to zoom in without getting pixilated image. (Millions of lines though)



mihaj -> RE: Disigning Polikarpov Po-2 biplane. (3/1/2004 10:01 PM)

After cleaning and aligning the views I got them to the same scale and then they ware scaled to the final "real 1:1" size of the model.
Next step was tracing the outlines and recreating cross sections. And again aligning of cross sections on the top of the side view (my working plane for modeling the fuselage) this time in 3D. This structure was used to generate a solid fuselage model.



BobH -> RE: Disigning Polikarpov Po-2 biplane. (3/2/2004 2:30 AM)

mihaj, that's pretty interesting. Please keep posting, I am enjoying the process.. Thanks BobH.



mihaj -> RE: Disigning Polikarpov Po-2 biplane. (3/2/2004 6:06 AM)

Thanks Bob,
I will do my best.

Here you can see the wing core that was generated using the same method that I used to model the fuselage.
There is also see some construction lines where future spars will be placed. On the left is a pattern that I will use to slice and dice the wing core to make the ribs.



Stay tuned for more!
Mike



BobH -> RE: Disigning Polikarpov Po-2 biplane. (3/2/2004 5:20 PM)

Are you planning to use foam for the wing or build one up from balsa? BobH.



mihaj -> RE: Disigning Polikarpov Po-2 biplane. (3/2/2004 5:56 PM)

quote:

ORIGINAL: BobH

Are you planning to use foam for the wing or build one up from balsa? BobH.


Hi Bob
This is going to be all build up construction using 1/8 and 1/16 ply, 1/8, 3/32, and 1/16 balsa. I'm calling it a wing a core just because I'm simulating the process of making ribs by chopping a solid piece. The idea is to end up with fully interlocking construction and 3D design is a grate tool to do it. NOTE that it's NOT a one off scratch build project. It has to be reproducible. The first prototype will be cut on CNC router and then transferred to a laser cut.
Final model will be a .40 size 58"WS that makes it easily convertible to an electric.


Mike



mihaj -> RE: Disigning Polikarpov Po-2 biplane. (3/2/2004 8:31 PM)

Since I don't have the old files with me I will use a horizontal stab as an example of getting structure out of solid model.
Here is a traced outline of the stabilizer with profiles of spars, ribs and leading/trailing edges.



BobH -> RE: Disigning Polikarpov Po-2 biplane. (3/2/2004 8:32 PM)

Mike, thanks for the additional info. If it were larger. IMAA. you could bring it to Warbirds over Delaware in July!.. Considering that its a cadd product, no reason why it can't be resized huh?.. Just a thought...



mihaj -> RE: Disigning Polikarpov Po-2 biplane. (3/2/2004 8:43 PM)

After "cutting" out slots for spars in the stabilizer core I sliced it with the rib pattern lines.
Here is the result

P.S.
I've made three copies of a stabilizer core (on top of each other) to cut out spars and supporting ribs (violet).



mihaj -> RE: Disigning Polikarpov Po-2 biplane. (3/2/2004 9:03 PM)

quote:

ORIGINAL: BobH

Mike, thanks for the additional info. If it were larger. IMAA. you could bring it to Warbirds over Delaware in July!.. Considering that its a cadd product, no reason why it can't be resized huh?.. Just a thought...

Bob,
Resizing is not as simple and linear process if you want to do it right. But good thing is ones I get the design done it will be just a matter of time to recreate it in larger size and different materials and thickness. Also it may require some modifications do to more powerful motor, servos and larger ailerons and elevators. It all depends on how large you want it to be.

Anyhow, here are some more pics for you.
Hey Bob, it seems like you are the only one that is interested. Hmmm...[8|]

But Thanks for your attention
Mike

P.S. I forgot to mention that this model will be SCALE!!!!!!! It is very unusual thing for the .40 seizers.



BobH -> RE: Disigning Polikarpov Po-2 biplane. (3/2/2004 10:36 PM)

Mike, I can't speak for the uninterested persons lol But your process is usefull to watch. I understand about resizing but after you do the major design work, redesigning may be less difficult. If you moved your thread to the "scale" forum you may get more interested parties?



mihaj -> RE: Disigning Polikarpov Po-2 biplane. (3/2/2004 11:07 PM)

It's OK. I'll stay here. May be I'll get more attention later.

BTW check out my thread about Yak-3.

http://www.rcuniverse.com/forum/m_1439579/mpage_1/key_/anchor/tm.htm#1439579

Thanks
Mike



buzzard bait -> RE: Designing Polikarpov Po-2 biplane. (3/3/2004 5:15 AM)

This is really amazing. Even though I will never get the time and equipment to do all this it is very interesting to follow. And I love the PO-2. The latest issue of Flying Scale Models has pretty detailed 3-views for several variants and includes a plan for a pretty CO2 powered Polish air ambulance version by long-time top free-flighter David Deadman. Jim



mihaj -> RE: Designing Polikarpov Po-2 biplane. (3/3/2004 5:51 AM)

quote:

ORIGINAL: buzzard bait

This is really amazing. Even though I will never get the time and equipment to do all this it is very interesting to follow. And I love the PO-2. The latest issue of Flying Scale Models has pretty detailed 3-views for several variants and includes a plan for a pretty CO2 powered Polish air ambulance version by long-time top free-flighter David Deadman. Jim


Thanks,

Actually, the only equipment you need is a computer and design ideas. And 3D design is more effective and time saving than any other method.

BTW talking about design....

Here is the wing that was constructed the same way as a stabilizer. Good thing, all four wing halves are identical which means that all I need is one half to be designed.



mihaj -> RE: Designing Polikarpov Po-2 biplane. (3/3/2004 6:41 PM)

OK I'm back.

Since this plane is half way done, I’m probably going to miss some of the intermediate steps of the process.
All I can say is the whole deal is to make some copies of a solid model and then slice and dice to get formers, ribs, spars, sheeting and so on. After all of the parts have being "cut out" it is time to “model” sticks and put them in place (they will be used to make cutouts in the parts.) At some point along the design I started to create the interlocks (and again "cutting" with different profiles to shape the parts up).
All of this may sound too general but it may take me a whole lot of time and effort to describe the design process in details.
The major thing is THINK 3D and use BUILDING EXPERIENCE TO BUILD A PLANE ON THE COMPUTER THE SAME WAY ONE WOULD BUILD IT ON THE BUILDING BOARD USING WOOD!!!
OK that is enough of lyrics.[:D][:D][:D]
Let's get back to reality.

Can you tell what this is?????????????[8|]



Oryx -> RE: Designing Polikarpov Po-2 biplane. (3/4/2004 7:39 PM)

Mihaj

That looks pretty good - and the Po-2 is a very interesting subject. Last month's feature on "Modeling the Soviet VVS" was on the U-2:
http://vvs.hobbyvista.com/Markings/Po2/po2-part1.html

BTW, which CAD package are you using?



mihaj -> RE: Designing Polikarpov Po-2 biplane. (3/4/2004 7:48 PM)

quote:

ORIGINAL: Oryx

Mihaj

That looks pretty good - and the Po-2 is a very interesting subject. Last month's feature on "Modeling the Soviet VVS" was on the U-2:
http://vvs.hobbyvista.com/Markings/Po2/po2-part1.html

BTW, which CAD package are you using?

Thanks for the link. That is very useful info.
I'm using Cobalt. It's a 3D CAD from Ashlar-Vellum.



mihaj -> RE: Designing Polikarpov Po-2 biplane. (3/4/2004 7:53 PM)

Ithink I found the color sceme for my first prototype.



beardking -> RE: Designing Polikarpov Po-2 biplane. (3/4/2004 7:59 PM)

mihaj, don't worry, you have more interest here than you think. We are all just letting you walk us through it instead of getting in the way (well, I am at least). I think your drawings look very good. Can't wait to see it get CNC'ed and see how well your 3d to wood conversion goes.



mihaj -> RE: Designing Polikarpov Po-2 biplane. (3/4/2004 8:28 PM)

quote:

ORIGINAL: beardking

mihaj, don't worry, you have more interest here than you think. We are all just letting you walk us through it instead of getting in the way (well, I am at least). I think your drawings look very good. Can't wait to see it get CNC'ed and see how well your 3d to wood conversion goes.

Hey guys, I didn't think that this thread will be treated as a tutorial.[:D][:D][:D]
I'm expecting to get some feedback as well as concerns and advices about my design. May be it is too early. I'm definitely going to need your participation when model is "materialized" in wood.

BTW you can see the 3d to wood conversion result on my Yak-3 thread.
I think Po-2 will be more painless. Experience MAN!!![:D][:D][8D]



mihaj -> RE: Designing Polikarpov Po-2 biplane. (3/8/2004 8:57 PM)

Hi

I'm back with a stabilizer parts (one half) that are ready for CNC.
One can notice a "tons" of interlocks.[;)][;)][;)]
Construction:
Ribs - 1/16 balsa
Spars - 1/8 balsa
LE - 1/4 balsa
TE- 1/16 ply
Control horn - 1/16 ply



BobH -> RE: Designing Polikarpov Po-2 biplane. (3/9/2004 1:32 AM)

looks like youll be assembling it soon.. kewl!



mihaj -> RE: Designing Polikarpov Po-2 biplane. (3/9/2004 3:36 AM)

quote:

ORIGINAL: BobH

looks like youll be assembling it soon.. kewl!


Not untill we finish our Yak-3[:D]



mihaj -> RE: Designing Polikarpov Po-2 biplane. (3/11/2004 11:28 PM)

Just want to share some design ideas.
1. planning on using a CF tubes to attach the wig halves to the fuselage and centerplane
2. planning on using a brass tubes and music wire (as an axle) to construct a landing gear
3. cabane struts will be made out of bass wood with aluminum inserts for mounting

Du you guys have any concerns?

Thanks
Mike



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