J-20 5th Generation Fighter VII


taxiya

Colonel
Registered Member
Maybe a nit pick, but why are there so many rivets on the canopy?

I know they will apply RAM coatings, but could they maybe not have designed it so the rivets are on the inside of the canopy to keep the external skin as smooth as possible?

With the canopy, it’s not like they would need to regularly undo the screws for regular maintenance and check ups to start with.

Even if you do need to undo the screws, that will mess up your stealth coating, so I am really struggling to understand why they didn’t just design the canopy frame such that all the rivets are installed from the inside.
I went back to look at pictures of J-20 in various stages of production. I am not sure but I have a proposal of what is done.

I think these holes are for fine finishing by adhering some kind of plastic/rubbery strips. The strips are heated to very high temperature becoming jelly like when being applied. The strip is then applied and pressed to the area with those small holes. Because it is in a jelly state, the strip material will be pressed into the holes and fill the interior which has a bigger cavity. After cooling, the strip will stay tight on the surface. The small holes are essentially for self-riveting of the strips. It is actually what you have suggested "inward rivet". Only the bigger holes are meant for screws for maintenance be left open. This can be seen that in the 2nd and 3rd photos that there is no marking of the smaller holes but only the recessed marking of the bigger ones. The reason of doing this is probably for RCS reduction, covering all gaps smoothly.

Here are the photos with my markings. They are large photos, so you can zoom in and take a closer look.
J-20_cockpitside.jpg
Very rough and big gap around the light strip. The canopy base are joint by four pieces with gaps. This is impossible to be finished with thick paint.
j20-primer 2017-11-10_2.jpg
In the semi-finished state, no sign of small holes. Only big ones. The marked area are otherwise super smooth.
Zhuhai2018 (20).jpg
In the finished state.
 
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taxiya

Colonel
Registered Member
the "teeth" is part of the double layer nozzle,functionally just similar to Rafale m88,bring out cold air from the engine compartmentView attachment 64554View attachment 64553
Just a note. Although both WS-10 and M88 has the little flaps and they all induce air from outside of the engine, WS-10 and M88 are quite different. WS-10 nozzle is convergence and divergence while M88's nozzle is induction. The flaps and the holes in M88 act to induce outside air to facilitate divergence of exhaust (expansion) without mechanics. WS-10 on the other hand has divergence mechanics just like AL-31 or the American equivalents to do the expansion work. The flaps and holes on WS-10 therefor is more for cooling and maybe stabilizing exhaust flames rather than the expansion work as M88.
 

Tirdent

Junior Member
Registered Member
Just a note. Although both WS-10 and M88 has the little flaps and they all induce air from outside of the engine, WS-10 and M88 are quite different. WS-10 nozzle is convergence and divergence while M88's nozzle is induction. The flaps and the holes in M88 act to induce outside air to facilitate divergence of exhaust (expansion) without mechanics. WS-10 on the other hand has divergence mechanics just like AL-31 or the American equivalents to do the expansion work. The flaps and holes on WS-10 therefor is more for cooling and maybe stabilizing exhaust flames rather than the expansion work as M88.
Mostly it is for expansion control though. Like, among others, the D30-F6, the WS-10 does have a short divergent section, but not long enough to properly expand the exhaust to near-ambient. Incidentally, makes the J-20 from behind look rather like the Su-47:

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