Yak-75 "Flapper"

[Gondor]

I won't mention anything about the 2:30 at Aintree   

Gondor

[Gondor]

Decided to add some length to the wings, this is not an attempt to enter one model into two themed builds at the same time. I have simply decided to follow an accepted aeronautical practice of reduced sweep outer sections to the wings to assist in low speed flight.

Gondor

[PR19_Kit]

Decided to add some length to the wings.......

GOOD thinking Alastair! 

[Gondor]

Decided to add some length to the wings.......

GOOD thinking Alastair! 

Think more Draken than U2!

Gondor

[Gondor]

The fuselage is getting nearer towards the fins being added. No blue and white roundels. so now I have to turn my attention to the wings as I need to wait for filler to dry before more PSR ensues.

Its progress they say!

Gondor

[Gondor]

Photographs!!

Wings and such!

First start with this.....


Do this to them.....


Then it ends up looking a bit like this......


The tape in the last picture is there to show where the end of the wing was so that I can mark a parallel line to get the new wing tip pointing in the right direction rather than being toed in or out. I applied the tape after making sure that the trailing edges were aligned as I do not want the trailing edge of the outer wing panels with a different angle to the inner wing.

Gondor

[Gondor]

The nearest to a MiG 29 that the Yak-75 is in some of its appearance. This should not be surprising as the TsAGI had come up with the basic requirements of an aircraft to meet the demands of the Soviet Air Force.
Twin fins, single cockpit with good all round vision, rough field performance and in the case of the Yak-75, canards and a chin intake.

I have changed the requirement. The wing is now modified to have more and less sweep in places as well as being extended a bit, this in turn has removed the need for canards.

The lack of canards might help confuse the JMN's when it goes public. 

More pics when I finish getting the old air-brake faired in properly. Its the worse fitting part of this build so far 

Gondor

[Gondor]

I have managed to get some more work done on the "Flapper" so here are a few photographs to show the progress that has slowly been made.

First up the new outer wing panel is just about ready to have the tip trimmed prior to being re-profiled back into something resembling an aerofoil.


The final part of the spine has been sorted, just the tail fins to be put in place then tidying up the cockpit. As they will be canted outwards at an angle I think I will have to make a former or jig for the tail fins as I want them to cant outwards at the same angle. There will be pictures so there will be no need to take notes, especially it its an F flat!


Here is a shot of the fuselage as it is right now. I just realised today that it will actually resemble a Project Cancelled aircraft, if you squint at it from about five feet away in a darkened room you will see what I mean!


Paint scheme and decoration will not be of long skirts, bobby hats and strings of pearls. Decoration will be a boring Grey overall other than dielectric panels the radome and of course the Red Stars and Bort Numbers. I might hang a few weapons beneath the wings but as the aircraft was not real don't expect the weapons to be accurate either.

Gondor

[Dizzyfugu]

Looks slick, like an alternative to the Su-15?

Keept it up! 

[Gondor]

The wings will certainly have a look along those lines but more Draken like.

Gondor

[Gondor]

So a bit more done, I am getting one wing made as a "Master" as it were then working from that to produce the other wing.

I was going to place the wings back to back then mark where to make my saw cut but realised that the surfaces made this almost impossible to do, plan 'B' called for!

Measurement!

You can see in this picture my rules for this occasion and in glorious 1/72 scale to boot! placed along the trailing edge to get the distance from the fuselage to the reduced tip. As you can see there is a small amount of trimming still to do at the tip.


I will also measure the leading edge of the wing as below, so that I end up with the same place to remove the existing wing tip on the other wing as it was removed on this wing tip.


The extensions have a fairly flat underside which allowed me to simply score a line and cut to suit. However, with the main wing and the extensions having different aerofoil sections a wing fence will have to be placed between the two which will hide a multitude of sins.

Gondor

[Gondor]

When I checked the marks I scribed in the under-surface of the second wing I found that in relation to the holes for the pylons the leading and trailing edge marks didn't match up. Plan 'B' swung into action or rather some fast thinking. First I figured out that as there were holes for the pylon mounting lugs on the underside of the wing, they would be in line with the airflow so I simply had to use some masking take and place it parallel with the locating holes and with an edge of the masking take against the trailing edge mark from measuring which I trusted more than the leading edge mark.



You can see the locating holes better in this picture.


The edge of the tape was used as a guide for a metal ruler and a line was scribed against the edge. The wing tip was cut off on the outer side then filed back to the scribed line.

I now have two matching main wings and work is apace on the cut down wings to make them "more aerodynamic" as the trailing edge was more akin to a wall than they should have been after being cut to shape..

The next problem is fixing the new outer panels to the wings, I am thinking of pinning them to the main wings, however I have never added pins into plastic that is this thin so advice will be welcome.

Gondor

[zenrat]

So it's not an ornithopter then?

As you have very thin panels try using thin wire instead of an actual pin.  On small parts on model cars (rear view mirrors etc) I pin them using the 0.5mm wrapping wire I use as spark plug leads.
While it doesn't add major strength it does add enough to prevent an accidental knock meaning something breaks off.
Just be aware that on a thin part a visible external bulge will result when drilling into it's end with even a 0.5 mm drill.

Just remembered I used this method to locate the resin prop blades on the Kookaburra and I managed to not break them off.

[Gondor]

So it's not an ornithopter then?

As you have very thin panels try using thin wire instead of an actual pin.  On small parts on model cars (rear view mirrors etc) I pin them using the 0.5mm wrapping wire I use as spark plug leads.
While it doesn't add major strength it does add enough to prevent an accidental knock meaning something breaks off.
Just be aware that on a thin part a visible external bulge will result when drilling into it's end with even a 0.5 mm drill.

Just remembered I used this method to locate the resin prop blades on the Kookaburra and I managed to not break them off.

Thanks zenrat 

Gondor

[Gondor]

A little more progress and it has also caused a slight step backwards too. More of that later, now the pictures......

Following zenrat's suggestion, which I had thought of as well, I started to drill holes in both the new wing tips and the existing wing. This is an end on view of the existing wing. In the background you can see the new wing tip with its two pins already located.


Here is a close up of the pins in the new outer wing.


So we have pins in holes and more holes for the other pins. The big question is do they fit together? 
The answer is surprisingly yes! Well ok, only one wing tip fitted first go, the other needed one of the holes cleaned out and a slight "alignment" of one pin but certainly not as much as I feared may have been required.


Here is where we see the expected step backwards in building the revised wing. Because the wing I am using for the extended wing tip is of a different aerofoil section that that of the existing wing, where they meet there is a significant difference in the contours of both the upper and lower wing surfaces. I am going to use a simple, effective and time honoured and very Russian method of curing this problem, I shall use a wing fence which will also double as a weapons pylon on the underside.


I did find it easier to pit the pins into only the outer wing parts rather than one into each piece. This could have caused no end of problems especially is I had glued them in place only to find I had put pins in the front or rear holes on both pieces 

Gondor