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Old 06-16-2012, 01:34 PM
Leif Ohlsson's Avatar
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Inka II Slovenian 1937-38 vintage glider

Here's a vintage glider which could be seen in the Slovenian mountain areas around 1937-38. The original designer of this paper model is Mitja Sersen Erman, and his original design in ca 1/25 scale can be downloaded from his site ultralajt.webs.com (scroll down until you get to the Inka model).

Mitja very kindly allowed me to rearrange, rescale & repaint his original uncolored model, and publish it here, in the downloads section (links in following posts). The model design is based on the original drawing below from Narodna Krila (National Wings) magazine, December 1948:



Mitja tells me that the Inka glider was designed by Dr. ing. Anton Kuhelj in 1937-38. Intended for schools and gliding clubs with little or none previous building experience, it was a much simplified version of the Grunau Baby. An early version of the Inka even had square wing tips:



Almost every Inka glider built differed from each other in various details such as the extent of plywood covering of the fuselage. Some builder gropus enlarged the rudder area, after reports of insufficient rudder control if built according to the original plans. I have used this as a license to create a division between plywood-covered sections of the aircraft and fabric-covered structure which was to my own liking. It may not represent a typical Inka, but in any case it was theoretically possible...



The glider was used for slope-soaring in the Bloke mountain area of Slovenia up to the outbreak of WWII. The starting method was the common one of the era, several club members tensioning two strands of thick bungee cords, while others held the glider back until no more tension could be achieved.



The glider was hauled back to its starting point by attaching a couple of barrel wheels to the landing skid. Gliding in those days was great exercise for everybody involved!



Data (original):
Wing span: 12,3 m
Fuselage length: 6,3 m
Height: 2,05 m
Wing chord: 1,4 m
Wing area: 16.35 m2
Root airfoil: Go 549
Tip airfoil: NACA M6
Empty weight: 130 kg
Take off weight: 219 kg
Best glide: 17
Minimum sink: 0,85 m/s @ 50 km/h

Original photos and drawing provided by Mitja Sersen Erman.
Attached Thumbnails
Inka II Slovenian 1937-38 vintage glider-inka-original-dwg.jpg   Inka II Slovenian 1937-38 vintage glider-scan0004.jpg   Inka II Slovenian 1937-38 vintage glider-scan0007.jpg   Inka II Slovenian 1937-38 vintage glider-scan0006.jpg   Inka II Slovenian 1937-38 vintage glider-scan0005.jpg  


Last edited by Leif Ohlsson; 06-16-2012 at 01:59 PM.
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Old 06-16-2012, 01:48 PM
Leif Ohlsson's Avatar
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The Inka II model recoloured, textured and in three scales

Based on the data for the original, Mitja Sersen Erman's original model was enlarged by 155 percent to get to 1/16 scale. It was then recoloured, textured with wood textures, plus a few smaller details like the pilot's seat and wing struts redesigned for an even nicer look.

Here are a few sample pages from the new 1/16 scale kit:



(Above:) This is page 1, which serves as introduction and instructions. If you have downloaded Mitja Sersen Erman's original, and studied it, you will notice that the main design difference is in the cockpit area, with what I believe is a more true-to-scale pilot's seat.



(Above:) This is page 2, with the main fuselage parts. Rather prettily textured, don't you think?



(Above:) Page 3 contains a lot of small parts. Mitja Sersen Erman kindly advised me on the order of the Slovenian colors in the banner on the fin.



(Above:) Here's one wing. There's one similar page with the opposite wing, and then a final page with some struts and internal spars.

The kit is formatted for a paper size of 42 x 21,6 cm, which is A3 length cut down to the maximum width of an ordinary A4-Letter inkjet writer. If you have an A3 printer, no problems, you will just get a bit of surplus paper. If you have an ordinary inkjet printer, cut your own sheets from A3.

Use a paper weight of ca 200g/sqm. That usually means a thickness of ca 0.25 mm.

I have changed the design of the cockpit interior quite a bit from the original design, to allow for textured insides, and a true-to-scale seat.

The Inka glider is very attractive from a modeling point of view, since the interior of the cockpit is more visible than in the Grunau Baby, on which the original glider was based.

For those who do not like the idea of large models, or strange paper sizes, I have rescaled the original 1/16 scale version into one 1/25 scale (like Mitja Sersen Erman's original model), and one 1/33 scale version. Both of these print on "universal" paper size, 210 x 279 mm, which is A4 width and US Letter height. Thus you can use both paper sizes.

These three versions will be found in the downloads section for civilian aircraft as soon as they clear admin scrutiny (probably during Sunday 17 June 2012). Here are the links:

Inka 1/16 scale - the original recolored and textured version.

Inka 1/25scale - 6 pages normal paper size.

Inka 1/33 scale - 3 pages normal paper size.

I would of course love for someone to take on one or several of these versions and post their experience. If any major problem is encountered, I will try to come up with a solution and amend these models.

Leif
Attached Thumbnails
Inka II Slovenian 1937-38 vintage glider-page-1.jpg   Inka II Slovenian 1937-38 vintage glider-page-2.jpg   Inka II Slovenian 1937-38 vintage glider-page-3.jpg   Inka II Slovenian 1937-38 vintage glider-page-4.jpg  

Last edited by Leif Ohlsson; 06-16-2012 at 02:11 PM.
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Old 06-18-2012, 05:30 AM
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The files have now cleared the moderation queue and are available at the beginning of the Aircraft/Civilian downloads section.

I added a 1/24 scale version, as requested by a friend who saw the possibility of combining the Inka model with commercially available models from the same era in that scale.

For a simple look at what the model looks like, I would recommend downloading the 1/16 version since that is the original.

Leif

Last edited by Leif Ohlsson; 06-18-2012 at 05:53 AM.
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Old 06-18-2012, 05:48 AM
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Beautiful old sailplane , thank you very much.
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Old 06-18-2012, 09:55 AM
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Nicely Done...,

Hi Leif,

Up to your old tricks! Beautiful old slope glider. I like the plywood texturing.

Noticed that there's snow on the ground in the last picture. A very dedicated group of enthusiastis...,

Best regards, Gil
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Old 07-20-2012, 02:42 PM
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Inka card stock model

The 1/33 version was scaled down to 55% and this is the results. There is a longer thread on this subject and other sailplanes in the sub forum "Sailplanes available?" John
Attached Thumbnails
Inka II Slovenian 1937-38 vintage glider-001.jpg   Inka II Slovenian 1937-38 vintage glider-002.jpg   Inka II Slovenian 1937-38 vintage glider-003.jpg  
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Old 07-21-2012, 02:03 AM
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Thanks John! Your post in the "Sailplanes" thread is here. Good to know that the Inka goes together without major problems, even in your chosen 1/60 scale! - L.
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Old 08-06-2012, 01:55 PM
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Updated version with improved fabric texturing

Now that I've learned a method for making translucent fabric over wood structures (this post in the Fi-1 sailplane thread), I could not resist applying it to the Inka glider, which is nothing but fabric over wood. Here's what the new wings looks like:



And here's what the same wing looked like in the previous version, just to be able to make a comparison:



I think the new wings look more exciting and more realistic. Here's what the fin and stab look like now:



The challenge here was to do something about the national insignia banner on the fin, so that it, too, would be a bit translucent, while simultaneously shadowed where the fabric did not have any wood to support it.

Those wanting to replicate it, just to learn the technique, will benefit from the tech notes at the end of this post.


The download

You will find the updated version of the 1/16 scale model in the downloads section under Aviation - Civilian. Here's the specific download link for the Inka glider. It will be available as soon as it clears the moderation queue (uploaded 6 Aug ca 20.00 GMT). (Make sure you get the updated version - I cannot see for myself, whether the version in the downloads section is the old or updated one. The new one says "Updated version with improved fabric texturing" in the first sentence of the text.)

I have deleted the various other scales, since these were just downscaled versions of the 1/16 version, no other changes. You can very easily print in other scales:


Printing & rescaling

1/16 scale: The original model was 1/25 scale. The 1/16 scale download is formatted for a paper size of 42 x 21,6 cm, which is A3 length cut down to the maximum width of an ordinary A4-Letter inkjet writer. If you have an A3 printer, no problems, you will just get a bit of surplus paper. If you have an ordinary inkjet printer, cut your own sheets from A3 or similar. Use a paper weight of ca 200g/sqm. That usually means a thickness of ca 0.25 mm.

1/24 scale: Print at 67%. This is a common scale for some commercial printed models which could be used as tug aircraft for a nice diorama.

1/25 scale: Print at 64%. This is the scale of Mitja Sersen Ermans original model.

For both of these scales you can use either US Letter or European A4 size paper sizes. There will be some extra white spaces, of course, top & bottom.

1/33 scale: Print at 48%. You can use portrait orientation of your paper and print 2 pages per sheet.


Texturing tech notes

I still think it is difficult to achieve some absolute standard for the various settings. I had to experiment a bit again, which makes me insecure every time. Here's the settings I arrived at this time (for a more detailed tutorial, see this post in the Fi-1 sailplane thread).

Fabric base layer: Regular fabric CMYK 10-10-50-15. Opacity: 25%.

Fabric pattern layer: Regular fabric CMYK 10-10-50-15. Opacity: 25%.
Inner glow: Normal - CMYK 0-0-0-0 - Opacity 100 - Blur 5mm - Center

Insignia (fin) base layer: Blue-white-red, opacity 75%. This is to leave a hint of the wood below.

Insignia (fin) pattern layer: 50% grey. Opacity 50 percent. The grey is a new feature. Best I could come up with to handle differing various colours over the same area of non-supported fabric.
Inner glow: Normal - CMYK 0-0-0-0 - Opacity 100 - Blur 2mm - Center (same as fabric pattern, but only 2 mm blur)

All figures and terms refer to settings in Adobe Illustrator.
Attached Thumbnails
Inka II Slovenian 1937-38 vintage glider-wing-new-version.jpg   Inka II Slovenian 1937-38 vintage glider-wing-old-version.jpg   Inka II Slovenian 1937-38 vintage glider-fin-stab.jpg  

Last edited by Leif Ohlsson; 08-06-2012 at 02:08 PM.
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Old 08-06-2012, 03:17 PM
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It's beautiful, Leif. You are achieving some realistic and very attractive effects for these lovely sailplanes.

Don
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Old 08-07-2012, 08:26 AM
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Thanks Don! - And I'm happy to be able to report that the updated Inka download now has passed the moderation queue, after kind assistance by Rick. - Leif
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