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TOPIC: Profile SAAB J 39 Gripen for Rapier L-1 or L-2

Profile SAAB J 39 Gripen for Rapier L-1 or L-2 11 months 6 days ago #678

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Hi guys,

for the background to this thread please see the latest blog:

www.jetex.org/index.php/blog/96-swedish-profile-jets-for-2018
This posting is about the creation of a template of a model for transferring to balsa or Depron. I can't match Mark Digby's or Rob Smith's CAD skills, but I think the end results of my efforts are not too bad.

As I say in the blog, I do love the Swedish jets and a Gripen has been on my 'wish list' for some time:


Above: photos of the real thing. In contrast to Mark I chose to model one of the prototypes as I rather liked the blue and yellow flashes and I didn't have to add any missiles.

After choosing your subject (or, rather, it tends to choose you) find a usable and not too complex 3-view to work from:


This is then printed out and drawn over if you want to enlarge the flying surfaces or compensate for the thin profile fuselage. I often combine two or three published 3-views and compare 3-views with photos until I'm happy it looks vaguely like the 'real thing'. The bits are cut out and scanned into the computer:


Above: the basic montage. Note only the starboard wing is scanned in as the port wing can be 'copied and pasted' in from the mirror image. That way the wings will be identical!

When satisfied with the basic outlines and proportions one can begin colouring in. This is quite soothing and he colours can be copied from photos or published 3-views. As with the 3-views, different photos and drawings can be scanned and combined - colours are notoriously difficult to get even half right. But decisions have to be made. The Gripen prototype is. as far as I can tell, basically grey blue or blue grey:



Above: comparing shades of grey. the fin was copied from a published drawing and cleaned up in paint shop pro

Detail is then added a step at a time:
Above: I've now chosen the shades of blue and yellow and have started the decoration.

And so one continues. I wasn't happy with the published roundels:


so created my own:



Below is the first 'complete' draft of the template:



The air intake warnings are incorrect, so again some creativity was called for:



The panel lines, control surfaces are then drawn in, and the right hand side created from a mirror image. Obviously, any lettering has to be redone! Here is the first version ready for printing:


Note I have chosen light blue for the canopy (as opposed to black).

I print these out in B/W draft to check dimensions; if all is OK, then it's ready for 'beta testing', that is printing on light paper or tissue and transferring to balsa. Obviously, the templates can be printed out at different sizes to suit L-1 of L-2 motors.

Would anyone out there like a high-res copy of both (right and left) templates?:unsure:

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Profile SAAB J 39 Gripen for Rapier L-1 or L-2 11 months 6 days ago #679

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Delightful, I look forward to seeing this in the air.

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Profile SAAB J 39 Gripen for Rapier L-1 or L-2 11 months 4 days ago #680

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Hi guys,

as you know, I have long admired Mark Digby's J 39C Gripen:



Mark has now finished his plan, and it was certainly worth the wait, for example:

And this is just the frontspiece! John writes:
"I too was impressed with his drawings, you may be surprised to know that the cover sheet is created from a rendering of a 3d model he spent many hours putting together. If you could see a view from the underside you would see it includes a fully rendered rapier motor where you can clearly read the L2 legend around the nose!

As a taster here is a lower-res copy of the wing templates:


and a close up of the fuselage side:


You can see how well Mark has thought things through - note the 3 degrees of positive incidence on the forward canard. The graphics are, I think you will agree, stunning.B)
The plan pack comes with extensive building instructions, for example:


If you would like copies of Mark's templates, just pop him an email at:
This email address is being protected from spambots. You need JavaScript enabled to view it.


John says they " look forward to forward to seeing how your prototype version progresses".:whistle:
but I don't think this will be until next year when I hope there will be quite a few Gripens (and Lansens, Drakens and Viggens making smoke trails in the air!

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Profile SAAB J 39 Gripen for Rapier L-1 or L-2 6 months 3 weeks ago #712

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Hi Guys,
I have finally been able to get started on the Gripen. Being a 'hemi-demi-semi profile model (it's compressed by 0.67 in width) construction is all-balsa, 3/32" sheet for the wings, 1/16" everything else. The fuselage is put together from light sheet sides with triangular edges and very light sheet top and bottom carved to shape. The thickness of the fuselage is sufficient to allow the Rapier to be hidden in a trough.
Here are the bits before covering:

and here are the all the parts after covering with paper:



The wings, tail and fin were easier than the fuselage, but did need some tidying up afterwards. The rudder and elevons are hinged:


Covering the fuselage, which is quite '3D' needed a lot of 'cut and paste' but the overall effect is not too bad. I was quite pleased with the tail pipe:



I agonised long about whether to add cockpit details, but, having moulded a canopy I decided to go ahead. Here is Sven in the office:


Next is gluing everything together. Watch this space!
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Profile SAAB J 39 Gripen for Rapier L-1 or L-2 6 months 2 weeks ago #713

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Hi guys,
well, I've glued everything together, more or less in the right places, with the following result:







Not too bad, and the colours came up quite nicely with a quick spray of acrylic varnish. It weighs 36 grams (a bit less than I feared) so the wing loading is 5 oz/sq ft which is 'not too bad'. Happily, the CG is where Mark said it should be without nose weight.:cheer:

I'll give it a few hand launches the next warm calm day and see if its gonna be a goer. We will see.:S

Anybody else out there busy building? It's quite lonely here!
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Profile SAAB J 39 Gripen for Rapier L-1 or L-2 6 months 2 weeks ago #714

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Wow, that looks splendid, a great tribute to your skills. I presume that is 0.5 oz/sq ft though. How big is it? I'm guessing, 15" span and 20" long overall and about 100 wing area? Sounds light? It will go well, clean too.

Note added by Roger:
Wow, this is praise indeed from a master! But no, that is indeed '5oz/sq ft'.
It's a bit smaller than your estimate, Howard. The span is 8.8"; length 15.4". The wings are 36.4 sq in, 0.254 sq ft.
It weighs 36 g, 1.3 oz. So the wing loading is 1.3/0.254 = 5.1 oz sq/ft . Sorry about the mixed units, but it's what I'm used to!
:whistle:
I have flown Rapier models of 10 z/sqft so the Gripen should be OK, if a bit trcky to trim, and probably fast and twitchy. We shall see. :S

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