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TOPIC: TSK - 11 Iskra Semi Profile For L-2/L-1

TSK - 11 Iskra Semi Profile For L-2/L-1 4 months 3 days ago #908

  • rogersimmonds
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Those of you who have been following the "New Models for 2020" thread will know I have, at the instigation of Piotr Tendera (who is manufacturing our rocket motors), been designing a new model:



Above: the TSK Iskra is a lovely little Polish jet trainer. This is a particularly colourful version that took Piotr's fancy.

A quick search on the Internet resulted in a usable '3-view':


prints of which I cut out to form the basis of a template for the model:



I enlarged the tailplane and fin by about 15% (not sure if this was necessary, but old habits are hard to give up!).

I checked the red colour against several photos (again from the Internet) and got to work with the rather nice livery:



I work in Paint Shop Pro 9, which is not ideal, but it's what I'm used to. Starting with the fin, the decoration is slowly built up a few pixels at a time. Piotr specifically asked for the number '13' on the fin.

After a couple days of hard work (thank goodness for the 'undo' function!) I was quite pleased with the result:



The other side was easy to do (think 'mirror function' of the software). Some of the fine detail I copied from the rather fine cardboard model out there, and I decided against too many panel lines, etc. I then printed out both templates on thin card, cut out all the bits, and checked everything fitted together:



Which they did, apart from a few tweaks here and there.

So next up is a proper balsa prototype.

More later .....:)

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TSK - 11 Iskra Semi Profile For L-2/L-1 4 months 3 days ago #909

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Construction followed my normal practice, first printing out the templates, cutting out the shapes, and temporarily sticking these on to sheet balsa:



I used 1/8" (3 mm light balsa sheet for the wings (Howard Metcalfe maintains an aerfoil section is superior to a 'flat plate' even at these scales' and 1/16 for the fuselage sides and tailplane. The latter are fixed to the fin, which I shall make a bit thicker than normal.
The wings, tail and fin were then sanded to shape (note the soft balsa wing is protected by hard 1/16" square balsa leading edge).

The fuselage is my 'normal' method with quite thick edges (soft on the top, medium on the bottom) so the whole can be rounded and diagonal bracing.



More later .....
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TSK - 11 Iskra Semi Profile For L-2/L-1 4 months 2 days ago #910

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That's rather pretty. I do like those little 'chequer board' national markings.

Will you be putting in a bit of dihedral? I think swept wings and deltas get a modicum of roll stability curtesy of the leading edge of the lower wing generating a little more lift than the other. Do you think it might need a tad of the old fashioned style?

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TSK - 11 Iskra Semi Profile For L-2/L-1 4 months 2 days ago #912

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I shall certainly put in a fair bit of dihedral, and perhaps (as is my usual practice) a tad of 'up' aileron' on each wing to give washout.

I spent yesterday sanding the wings, fin and tailplane, followed by a couple of coats of thinned dope.

The fuselage needed more than a bit of carving, starting out as an quite unprepossessing lump:





but I was quite pleased with the result. Mind you, it took all day! :unsure:





Next task is covering with the appropriate part of the printed templates. I decided to cover with some very nice white Modelspan which takes the ink well.

More later ....
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TSK - 11 Iskra Semi Profile For L-2/L-1 4 months 2 days ago #913

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Looking great

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TSK - 11 Iskra Semi Profile For L-2/L-1 4 months 22 hours ago #914

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Covering the wings, tailplane fin and fuselage with tissue took (on and off) two days. I was pleased the ink didn't react (much) with the dilute dope I was using and everything matched up quite well:



And the wing a and tail feathers fit sort of where they are supposed to:



The two extra bits of balsa are the side cheeks that fit under the wing so that I can attempt facsimiles of the air intakes. These are a characteristic feature of the real one and it would be a pity to miss them out. :dry:

Next step is to glue everything together, using a jig to make sure everything is square:



You will note I touched up the wing leading edges etc with paint of matching colour, which is where my OCD can kick in. It's best not to get carried away with this procedure - one can end up painting the whole model - which using pre-printed tissue is meant to avoid!
Time for dinner ...
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Last Edit: by rogersimmonds.
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