IVL K.1 Kurki – peanut plan

If you check my last post (see here) you might notice that I sound overly enthusiastic of this ugly duckling. You are pretty right.. This is truly one of ugliest planes I have seen and it is also of finnish origin.

It was designed in 1927 by Asser Järvinen. He was employed by Finnish state aviation factory (IVL = Ilmavoimien Lentokonetehdas, directly translated airforce airplane factory..). Originally this plane was his pet project which he designed without permission. But the need for planes was so great that initial design got accepted as an official project.

Good intentions do great things, but not in this case. When plane was completed it turned out to be overweight and challenging to fly. For many reasons. There is an good wiki page for it. Strangely enough this is categorized as an military, transport & training plane.

After extensive testing, some 55 test flights it was concluded that it is of ‘no practical use’. Project was scrapped and only existing plane was stored for prosperity. That is museum. It ended up in Vesivehmaa museum where it was stored in sad condition. Check my previous visit there.

After while good people of Finnish Aviation museum decided to restore it and the end result is much nicer. But still it is ugly plane.

Well, that does one do when one encounters something so extraordinary? Obviously one must make model aeroplane out of it. I did some initial design drafts couple years ago. Then after new Kurki exhibition opened in decemeber 2018 at museum I decided to complete design. For several reasons I decided to make an peanut scale version of it.

So here it is for your viewing and building pleasure. Enjoy.

Click here to download plan.

I strongly propose that you visit Aviation Museum (Ilmailumuseo) to see this plane in it’s 1:1 glory. It is sight to see, and the  IVL Kurki special exhibition is open to end of january 2019. Nice place to visit in so many ways!

This plan has been released for free download. If you manage to make something out of it pls send me pics of that. I would love to hear whether it flies….

Getting better scanning results from vintage plans

Now with better time I have been tuning my processes for better scans. For mini-review of scanner see here. This is continuation article of that mini-review, but these comments apply also to any scanner.

1. First, if plan is really vintage, try ‘Document type : Grayscale CAD/map’ instead of normal colour. For example, see below:

with colour

with Grayscale CAD/map

This is rather counter-intuitive, but idea is to let scanner do automatic removal of yellowish tint. It performs rather nicely.

2.  Do not use high resolution.

Changing resolution from normal (300) to fine (600) dpi creates rather large files and makes things much more complicated. Using 600dpi resolution creates A1-scans of PDF-size 16mb. And if you open that file and make some changes you end up with 200+ mb workspace and 150mb files. Which are just too much.  Using 300dpi has enough resolution for normal model aeroplane plans.

3. Use backing paper if plan is really fragile.

Use normal A0/A1-roll paper as backing if plan is almost schreds. Just tape leading edge of plan to paper with small pieces of tape (3M Magic Scotch). Note that use as small amount of tape as possible and only on leading edge. By leading edge I mean the edge which goes into scanner.

really brittle plan with all kinds dents.

taped to paper, nicely and safely waiting for scan

4. If plan is vintage drafting paper then do following

  • scanner can do wonders with yellow tint removal, but it cannot help translucent drafting paper hue. You can try to use backing paper to make effect smaller, but it does not work well enough

Plain Grayscale CAD

Graysale CAD with paper backing.

  • Get adobe photoshop, elements is just fine and use Levels-tool. Move white end from right side to the left part of black curve. See below.

Using levels

And then you get much more clear plan.

Good enough.

The plan in question and further info of this nice -30’s biplane can be found here.

Visited F3A competition @ Paattinen model aeroplane field 15.-16.7.2017

Nice weather. Some pics.

Aerotow hook printed by @shapeways

Just received final professionally printed version of Aerotow-hook (see all notes about this) from Shapeways. It looks gorgeous. The openings are not really open, but it does not matter as they must be drilled to spec anyway. It feels slightly heavier than PLA-printed version, but that does not really matter.

This process of first designing product in 3d-cad, then prototyping it with home printer and finalizing it with shapeways is really working. The home printed version has limited strength but this shapeways ‘strong and flexible’-material is extremely strong. Shapeways also have really, and I mean really fast & professional service. You can get your copy of this version from shapeways.com (direct link to product). Also I’ll try to embed shapeways product info directly below. Let’s see how it turns out.

Also, just an reminder – if you want to print this directly in your home printer, or ask shapeways (or some other commercial printer) to print it for you just download this file aerotow S 06. It is ready .STL-file, identical to that in shapeways.

Send me photos if you try this out. Thanks in advance!

3d-printed aerotow hook done

Ok, this is now done. For maiden use I have to wait until weather will get warmer. It might take 6 months or something. I still made some changes to design and then printed final version. Some notes regarding printing & actual installation:

  • Use infill of approx 70%
  • I used temp 205c
  • Use normal speed, ie. do not use faster than normal speed

With these settings and my Miniboy this thing takes approx 2-3hours to print. Then actual installation is breeze.

  • Final weight including MG-14 servo is 32g but this varies with printing settings
  • All holes must be drilled for final spec.  STL-file contains holes set so that servo screws are 2mm, installation holes are 2mm and hook pin is 3mm.
  • I used 3mm brass tubing for pin with piano wire epoxied into it for servo actuation, I drilled pin hole to 3.5mm

Just as christmas is approaching I decided to set this to public download. You can copy it from aerotow S 06 (I had to put it into .zip file as wp does not allow .STL-files as media files). As 3d-printers are somewhat rare I also set up shapeways account so that you can get it printed. You can find it here. Actually, I have not printed this using shapeways, but they make great models out of normal .STL-files so this should work well. But just to be cautious I set this product to beta. If there are problems pls. let me know. Also, I am well aware that the use of MG-14 is a bit risky, but this is inteded for light aerotow of light planes etc.

Some pics of final sprint are below.

This is first design I have done with 3d-cad. Or actually I have done several ‘things’ which are used in several places, but this is first which has any further use. I am quite happy with Autodesk Fusion 360, but the learning curve was quite steep for me, I have long history of 2d-cad work and model aeroplane design. This new tool is an new tool requiring adaptation of workflow and different mindset.

Still, final design looks kinda spiffy 🙂


Final disclaimer : this has no guarantee whatsoever. It might work in it’s inteded use or then again it might not.

Edit : I added video of Z-400-maiden. It was year 2008 and weather was bad. Really bad.

Continuing 3d-printed Aerotow hook

That printed rather well, but still some refinements to design are needed. I added further flanges to servo posts to limit splitting of material due self-threading screws. After a while I realized also that the holes for screws need to be just right size to work well. Then one thing would be just avoiding self-threading and using machine screws, like M2.

Design evolution from prototype to more refined design. I have corrected some minor problems to design and final printing will be done when I have finalized pushrods etc. Current final desing looks like this:

Those screw holes on top of structure are to pin structure from above. This PLA-printed structure is a bit like wood. It will split only laterally, a bit like wood grains. So to limit splitting one could use vertical binding screws. Also, not visible in this picture, the holes through the bottom of part are not all the way through. This is due problem of printing start of first layer. If there are minute details (like holes) in part they are tricky to print because they do not adhere so well to printing table. This might be problem of Miniboy, or something else. One thing still, this is absolutely largest version of this part that can be printed in Miniboy.

3d-printing an aerotow hook

Lately I have been toying around with an cheap and cheerful 3d-printer, an Mini Fabrikator by Tiny Boy from Hobby King. Actually it works rather well with some limitations, like small print area etc. But it works.  Original idea was to utilize 3d-printer for small scale detail parts for kits but is has proven useful for other purposes also. I really think that in future large part of modelling will be done using cad & 3d-printing. It makes things much more exact and also from kit building perspective it is really shortening design and building cycles. I do initial design in cad anyway so the leap from drawing to 3d-design is quite short.

Then to today’s dish. I also have an old electric aerotow plane, an rather rare kit of Zlin Z-400. It flies well, but it’s aerotow hook has suffered .. something. So I decided to make an new hook.

This is somewhat rare experiment. Aerotow hooks are normally made out of aluminium or something as strong. Making something using extruded PLA is propably not sane thing, but I can always try it. Also, If it looks nice I can always get it printed at shapeways.

First I made some measurements from existing plane. This is quite old plane and hook is really bad looking.

Then I proceeded to make an prototype of new and improved design. You might notice extreme overkill in material strengths, but to get this strong enough it must be done this way. I did design in Fusion 360 which is rather easy to use after some head banging. Then proceeded to print prototype and try it out.

Design looked ok, but it was quite clumsy. I made several refinements and currently 3d-printer is churning next version out. You can see design for that below. This is interesting.

Model Aeroplane Enthusiast Colouring book vol 4.

And the volume 4. of Model Aeroplane Enthusiast colouring book…

Model aeroplane colouring book vol 4

Model Aeroplane Enthusiast Colouring book vol 3.

And then to next volume of colouring book.

Model aeroplane colouring book vol 3

Second Model Aeroplane Enthusiast Colouring book

And to continue from vol.1 of model aeroplane enthusiast colouring book, here is second vol. Enjoy!

Model aeroplane colouring book vol 2