Quand un mirage n'est-il plus un mirage ? Quand il transporte un rayon de soleil

[Gondor]

While not much physical work has been done, the little grey cells have been putting in the hours. It is the weekend though, so some progress should be made.
After finding a picture on the Secret Projects forum which shows a two-seat cockpit being assembled while the two 4000's were being built, shows me that the style of cockpit was simmilar to that used for the 2000, so I have glued the 2000D fuselage together to work out where to cut, and the closed canopy has been used to give me an idea of how it will sit on the 4000. Of course, if I have the canopy open, that could hide a lot of misalignment and act as a distraction from other things, too.
I might have a go at the underfuselage conformal fuel tank; it all depends on how well other things go.

[Weaver]

There's a profile on that Secret Projects thread from the guy who did them for the Mirage 4000 book. It shows a 2-seater with a 2000N/D spine, but with fewer canopy frames. There's also some discussion about whether that factory photo shows a "4000B" or a 2000B under construction. It certainly looks like a 2000B, with two opening sections with a fixed portion between them, rather than the one in the profile, which looks like it might be single-piece. If you look at a cutaway of the 4000, the space behind the pilot is partially filled with avionics, rather than being empty, as in an F-15. That might make the spine more credible as an alternative home for those avionics, assuming that they're neccessary for an operational aircraft and not just flight test instrumentation. The spine might possibly be more neccessary on a strike-oriented aircraft than an interceptor.


Mirage 4000B profile. This was apparently done in collaboration with the authors of the Le Fana book:


(Image originally posted to Secret projects by user "alanqua" here: https://www.secretprojects.co.uk/threads/mirage-4000.34/page-3 )


Mirage 2000B:




The factory photo. Note the fixed portion between the two canopies and the single-hole fuselage frame at the rear, implying a single engine(?). It's credible that the Mirage 2000B prototype and the Mirage 4000 were in the factory at the same time:


(Image originally posted to Secret Projects by user "PhR" here: https://www.secretprojects.co.uk/threads/mirage-4000.34/page-6#post-898806 )

[Gondor]

Good point, well made. The forward fuselage in the photograph also looks to be too shallow for it to be a 4000 forward fuselage. So I think I will go with the artwork you just posted.

After a think about it, I may just use the 2000D canopy, but erase the existing central tunnel frame lines and install a single one in the middle. I would also have to add an edge to the canopy where the tunnel was, due to that part of the fuselage side being higher than where the individual crew canopies are.

[Gondor]

I have been looking at possible canopies for this build. The nearest that I can find is from an F-14, although I can't find my TSR2 trainer canopies to check them against the requirement. While talking TSR2, I have a spare belly tank which I recon with a bit of cutting up and a little addition here and there will do the same job on the 4000.

[Gondor]

No pictures today, maybe tomorrow. I received a vac-form F-14 canopy today, which allows me to free up a Hasegawa canopy to test fit and use, or even modify for use, as the canopy for this build. Consequenty I have had no option but to glue the forward fuselage halves together, after checking that the new rear bathtub can be fitted afterwards.
I think that the canopy will need too much work to be useful other than as the basis for a buck to make a vac-formed canopy. That is something that I would ask someone else to do, as I don't have the equipment to produce a good-quality canopy. The buck, yes, that I can do, but the making of a canopy, no. Saying that, I do not know yet if that is necessary or not. The forward fuselage is drying at the moment, so I will find out tomorrow. I did fix inside the fuselage, two sections of L-shaped plastic rod, to support the rear cockpit tub. I have also marked up the forward end of the spine of the 2000D so it can be prepared for transplantation onto the 4000. I should get that cut out tomorrow, so I will have a much better idea of how things are progressing by the end of Sunday.

[NARSES2]

I think my success rate with plunge modelled canopies was about 1 in 5 back in the day. Havn't tried it for decades.

[Gondor]

I think my success rate with plunge modelled canopies was about 1 in 5 back in the day. Havn't tried it for decades.

No problem Chris,  I will put you on the list of who not to ask then.

[Gondor]

Only a little progress. I realised that the rear cockpit I had "borrowed" from a Mirage 2000D was sitting in the nose undercarriage bay roof, where in the 4000, the pilot's cockpit sits in that position. So the GIB, Guy In the Back, doesn't need to be very high as he is mostly looking down in the cockpit and won't need as good a view as the pilot.

So I marked up the rear cockpit for a bit of trimming



I had also made some rough measurements of the inside of the fuselage, so I would have an idea of how much to reduce the height of the rear cockpit.



These were the lines to the right. The rest were from earlier.



I did try the cockpit at the height shown, but it's not enough, so I will have to get out the saw again.

[Gondor]

I have taken an idea from Dizzy and stuck some foam into the area behind where the intake parts go.





I thought white would work well with the intakes being the same colour.

I have also settled on the position of the rear cockpit. It is now firmly glued in place, so no going back without a lot of swearing and the like.



The parts in the picture above the forward fuselage are the spine from the 2000D. I found that using my ultrasonic cutter on Low rather than High or Auto gives me more control without the hot wire effect on the plastic that I am cutting through. I now ned to finish painting the exhausts so I can button up the fuselage and then try to find out how much weight to fit under the rear cockpit that I have just fitted.