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Fly Swedish SAAB J-29B Tunnan in Congo


thierry laurent
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Nice progress :speak_cool:

 

Good to learn about the fixes for this kit. Used square Albion tube too for my (stalled) Mirage III build. For Trumpeters Mig-19 simply went with Evergreen styrene tube drilled through the wingroots after the wings were glued on. But the Mig-19 wings had a sturdy internal structure and were lacking only in mounting tabs to the fuselage. I'll go with the square brass rod too when time has come to pull my Tunnan out of the stash.

 

Keep rolling!

- dutik

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Thanks Dutik!

 

Here's the final work done on each stabilator edge:

 

zt6XYse.jpg

 

And here's the elevator with the sanded front edges:

 

5lf6jmN.jpg

 

Finally, here's how should look like the final combination when added on the kit:

 

6xbYeX3.jpg

 

I will add some small copper wire sections between both to secure the seams. The elevator will be put in neutral position as this was the normal stance in parking mode.

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I forgot publishing a picture with the final strengthening step: replacing the pylon holes in the wings by sections of rods. They go through the wing to be glued against the inner side of the top. Corresponding holes will have to be drilled in the pylon. A side effect will be the easiest possibility to add the tanks and pylons after painting.

 

gFTavh6.jpg

 

The wings are now rock solid! :thumbsup:

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Then, I had a look at the pitot tubes. Well, I should say at the parts that should normally become pitot tubes...<_<

 

Here's what Fly is offering:

 

j0ob3ZH.jpg

 

Ouch! :blink:

Useless to say it is highly recommended to rebuild them. I relied on my proven Albion tubes. I used sections of 0.8 and 1 mm. I also rounded the edges with fine sandpaper and here's the result.

 

YjJ9D99.jpg

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And now, what about the engine exhaust?

 

Well, for whatever reason, it looks Fly mixed the De Havilland Ghost used on the early J-29 marks with the upgraded engine with afterburner used on the J-29F. The later engine was not only sligthly larger. It also had a fully different exhaust. And this looks like what Fly is proposing:

 

TWoHf9u.jpg

 

However, here's a cross section of the Ghost engine used on the J-29B:

 

DlP7XGU.jpg

 

The main difference is the lack of pointy rotor cone that took most of the place inside the exhaust tube. This really annoyed me. I have already bugged Brian from Resin2detail to see him releasing the early engine that is actually 95% ready. He looked more interested when I mentioned this could also be used on Sea Venom models. Unfortunately, this is not on the top of his pile of priorities. So, I considered different ways to improve the parts myself. Initially I had the weird idea to mold the tip of a new pencil! Then I had another idea that deserves further investigation: the rear of the useless tanks!

 

47xC1ZE.jpg

 

I think I may have found an easy solution...:whistle: Obviously you will have to find something else if you want to use such tanks. Hopefully, only the later ones were used in Congo.

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Well, it looks I was somewhat overoptimistic... The Fly parts are a cylinder whereas the full exhaust part had a truncated conical shape. The TM view clearly shows it. This means that if you want adding the very visible rotor cone its base diameter needs to be smaller to be inserted into that cylinder. It should also be far pointier to see its end located close to the exhaust rear end. Not that simple. The best approach asks for replacing that exhaust chamber. One option that may already help somewhat is to use the larger J-29F parts given in the box. I really need to assess that. More calliper work ..<_<

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24 minutes ago, dutik said:

If things go wrong there is always the option to put a nice bright red exhaust cover onto the muzzle and call it a day.

 

Regards

- dutik

Well for whatever reasons pictures of Tunnan airframes with FOD protection are very rare. Moreover, I think I've only seen the mesh type over the intake. Last, I did not find one picture with FOD in Congo! :(

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Hi guys,

 

To keep you informed: Some days ago I have been contacted by Andreas, the Swedish modeller who restored a full scale airframe and produced some 3d- printed parts. He is currently finalizing the early exhaust. He proposed sending me some 3d parts to assess them and I proposed to review them for LSP in due course. The side effect is the need to slow down the pace as some internal parts are included. He already made the seat, nose intake, wheels and the exhaust is coming. Wait and see!

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3 hours ago, thierry laurent said:

Hi guys,

 

To keep you informed: Some days ago I have been contacted by Andreas, the Swedish modeller who restored a full scale airframe and produced some 3d- printed parts. He is currently finalizing the early exhaust. He proposed sending me some 3d parts to assess them and I proposed to review them for LSP in due course. The side effect is the need to slow down the pace as some internal parts are included. He already made the seat, nose intake, wheels and the exhaust is coming. Wait and see!

He is doing some nice stuff.
It would be worth to wait for that.

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  • 4 weeks later...
On 10/13/2022 at 8:34 AM, thierry laurent said:

Well, it looks I was somewhat overoptimistic... The Fly parts are a cylinder whereas the full exhaust part had a truncated conical shape. The TM view clearly shows it. This means that if you want adding the very visible rotor cone its base diameter needs to be smaller to be inserted into that cylinder. It should also be far pointier to see its end located close to the exhaust rear end. Not that simple. The best approach asks for replacing that exhaust chamber. One option that may already help somewhat is to use the larger J-29F parts given in the box. I really need to assess that. More calliper work ..<_<

Great build and learning curve!!!

the cone in the exhaust is called just that-exhaust cone(helps to smooth the gas flow)

about FOD cover-I don't know of any jet without them,lack of photos isn't an indicator(there's always a chance a cat or a bird will enter the intake),the net/mesh cover

is for engine run up tests

about your solution of the wings-isn't an H profile better in bend resistance than square one?

If the wings would've been longer-do you think these profiles will held the load?

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42 minutes ago, iaf-man said:

about your solution of the wings-isn't an H profile better in bend resistance than square one?

If the wings would've been longer-do you think these profiles will held the load?

The problem with an H profile is simple: you cannot slide smaller sections into larger ones. This means you have to use a single part and slide the wings over it. This is more complicated and assessing how to glue it efficiently inside the assembled wings is also a major challenge. So, to me, this was not a good approach. The assembly is quite solid and the advantage of the square profiles is that you can put smaller ones inside to get an even more rigid result. This also means the section can become progressively thinner from the wing root to its tip. Last, you can also use more than one spar. Initially I considered that possibility to use a second one but quickly concluded that was hopefully not required.

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