Su-27KUB Naval Trainer 1/72

[Dotcom]

Hello fellow modellers,

I am usually a silent watcher on this forum, but for once I also like to contribute with my current time-eater.

After finishing my last long-term project, a Hasegawa old mold F-15E with plenty of mods, I decided to step a bit ahead in the extent of scratchbuilding. The new subject requires quite some alterations in order to turn a stock kit into a different version aircraft. I don't intend to go into the highest level of detailwork but rather use the project to explore and hone advanced scratchbuilding skills.

The Sukhoi Su-27KUB is the two seat trainer version of the Su-27K/Su-33 carrier based fighter of the Russian Navy. It first flew in the late 1990s but only few items were ever built and seen in service. The main modification of the KUB variant over the standard Flanker is the cockpit section with the pilot and instructor seating side-by-side, similar to the Su-34 Fullback bomber version.

To my knowledge there is no kit of this Flanker version available, but forum member Flankerman masterfully described his modification of an Airfix Flanker into the prototype Su-27KUB. While in my build I start with the Italeri 'Sea Flanker' I was very inspired by Flankerman's work.

An image of the operational Su-27KUB is seen at:

http://www.airsceneuk.org.uk/airshow01/zhukovsky/su-27kub.htm

The Italeri kit to start with.

The major components. The Italeri kit is not a very accurate rendition of the Sea Flanker as the Canard wings are quite off, missing the characteristic 'shoulder' blending into the body. The tailcone lacks the modification (higher and shorter) as seen in a Sea Flanker. But it has the twin wheel nose landing gear and the overall shape, despite raised panel lines, looks fair enough.

More info on the intended modifications to follow shortly,

Regards,

Andy

Edited July 26, 2011 by Dotcom

[Berkut]

Look very much forward to this one! But i have to wonder, why do you start with Italeri kit? If i remember correctly, the intakes are way to small/slim.

[Nazar]

Look, photos will probably be useful

Su-27KUB

[supergru]

It first flew in the late 1990s but only few items were ever built and seen in service.

Hi Andy, looking forward to see this conversion, especially in 1/72 scale.

As far as I can tell, there's only one Su-27KUB ever built.

[Dotcom]

The major modification hotspots

I identified a number of work packages/items that need to be adressed for the intended project:

(1)

2 seat cockpit: The big one. Cut out kit cockpit section, replace with scratchbuilt floor and bulkheads, blend in with rest of the fuselage, add instrument panels and seats, get a canopy from whoknowswhere, ...

While I could use the Italeri Su-34 kit cockpit this would leave me with a useless rest of the Su-34 which I plan to build later on. So I decided to make the cockpit section from scratch, in the end I intend to learn something here ;-)

(2)

Canards and shoulders: Add correct shape canards and provide attachment points which blend in with the rest of the fuse. Will take quite some putty I assume.

(3)

Tailboom position: Remove kit tailboom which is for landbased Su-27, replace with a shorter and higher boom. Add arrestor hook.

(4)

Wing chord: Increase wing root chord as on all sea based flankers by splitting the wing at the flap location. Provide ailerons and two section flaps. Imitate wing fold mechanism, but wings remain extended (let's not go over the top here ;-)

Edit: Increase wingspan to scale 16m by inserting additional section at wing root.

(5)

Elevon inner corners are squared off on Su-27KUB as opposed to the canted version on the kit elevons.

Points 3-5 are nicely shown here:

http://www.airliners.net/photo/Russia---Air/Sukhoi-Su-27KUB/1671007/L/

Well, thats about the roadmap. I'm sure lots of additional smaller things will come up and need to be added along the way.

Cheers,

Andy

Edited July 26, 2011 by Dotcom

[Dotcom]

@Berkut:

Why the Italeri kit - a good question to a long story ;-)

I had the kit in my stash for quite a while, and it had been picked up at the LHS at a very reasonable price. The original plan was to turn it into an accurate Su-33 Sea Flanker with all the mods necessary, including wingfold and such. After lengthy reference study I compiled a long to-do list with all the steps necessary to come up with a reasonably accurate Sea Flanker.

That was about a week before I learned about Hasegawa's new tool Su-33 release.

So I thought, let's go bowling, and bin the conversion plans. But then what to do with the Italeri kit? Then I thought of this new challenge and here goes ;-)

I will definitely look into the intake size then, wasn't aware of this deficiency. thanks for the hint!

Cheers, a

Edited July 24, 2011 by Dotcom

[Dotcom]

@Nazar:

Thank you for the link to the reference pictures, they will come in very useful!

@supergru

From a google images search I came up with pictures of two different aircraft: The yellow-silver prototype and a blue camouflage aircraft (21 Blue). It never occured to me that this might actually be the same aircraft, but then of course I didn't check further. So it might well be a unique conversion.

I haven't decided yet as which of the two paint schemes i will do, but then, that's still long off...the prototype does sure have it's charm though.

Regs,

Andy

[Flankerman]

Andy,

I will follow this one with interest....... I http://www.lindenhillimports.com/su-27kub.htm eleven years ago !!

Note though, the wings of the Su-27KUB are much bigger than even the Su-33 (which itself is bigger than a Su-27).

As well as the increased chord to make the Su-33 - you need to also increase the span for the KUB....

The relevant figures for span and wing area are :-

Su-27 - 14.698m, 62.04m2

Su-33 - 14.698m, 67.84m2 (increased area)

Su-27KUB - 16.0m, 71.38m2 (increased span and area)

If you can start with the Hasegawa Su-33 it should save lots of work.

Note also that the shape of the canards changed on the KUB - early flights in primer had canards with a straight leading edge, later flights - when it was fully painted and had TVC nozzles also had a new canard with a kinked leading edge.

Happy Flankering

Ken

PS - The wing fold line on the KUB is further outboard and it doesn't have folding horizontal tails.

Edited July 24, 2011 by Flankerman

[Dotcom]

Well then, let's get started!

First I start with the wing flaps. The Sea Flankers have a wing with ailerons (outboard) and two section flaps (inboard) with a longer root chord as opposed to the standard flanker wing where there is only a single flaperon.

See the original flap configuration:

http://www.airliners.net/photo/Russia---Air/Sukhoi-Su-27KUB/1671007/L/

The left wing flap was separated and will be in approximately the position as shown above. The missing triangle to be filled with sheet plastic.

Sheet plastic added. The outer part is glued on to the aileron. The inner part is separate for the additional flap section. I always use CA glue to bound sheet plastic as normal plastic solving glue won't hold it one bit.

The notches for the hinge connections are cut out. This was done using a file, and alignment proved difficult. Some putty will need to cover this up later.

The hinges added, made from square plastic profile.

All in place provisionally. Still some putty will be needed to remove seams and such. I think it looks quite it's business if the light shines through the flap section gaps on a rather small plane as in 1/72.

That's it for the moment, will see how much time I can make during the week.

Regs,

Andy

[Dotcom]

Hello Flankerman, nice to have you on board!

About the wingspan...bummer! :-| i should have followed your description more thoroughly. I had one reference stating the span as 14.7m for the KUB and didn't check further...but of course you are right, the below picture shows the flaps extend to a wider span than the elevons which is not represented on my flaps. The info is much appreciated!

http://www.flanker.free.fr/mono/Texte/su27kub/22.jpg

I guess I will fix this by moving the wings outbord and lengthening the flap towards the fuse. At least one hinge I will need to redo. I also see that my aileron is quite off (too slim) but this will have to do... Glad I didnt do the right wing yet.

[rom]

hi!

nice project! ;)

have fun

rom

[tonal]

Hi Dotcom, great start!!

Tonal

Edited July 27, 2011 by tonal

[Dotcom]

Hi rom and Tonal, thank you! Hope it goes on like this!

As a short update, I started working on the canard wings and shoulders. The demarcation line between shoulder and canard seems to have some toe-in, that is to say that the shoulders get narrower towards the front.

Drawing the shoulder shape onto sheet plastic.

Note the ledge which will slide in between the upper and lower fuse half.

Small curved scissors is very handy in cutting thin plastic. Found it at the beauty department of a supermarket :-P

Don't forget to make a second item for the opposite side at this point, else it needs to be redrawn.

A notch was sanded into the top fuse half to allow for the shoulder to slide in between...

...like this.

Overall view. Smaller plastic bits and lots of filler will be needed to get the blend once the cockpit section is modified. Also, the Canards will be positioned in a parking nose-down position so a shaft needs to be integrated.

Inside view. The ledge provides ample room for the glue.

Well that's it for the moment...other building projects keep me busy as well, but I hope to get back soon. It sure seems to be a challenging project.

Cheerio,

Andy

[PetarB]

This is shaping up nicely. Please excuse the terrible pun!

[Dotcom]

This is shaping up nicely. Please excuse the terrible pun!

Hi PetarB, thanks! But I didn't see no pun here, maybe my english is not well enough ?!?

[Dotcom]

Hi everyone!

This update starts the real chopping work.

Drawing the cutting line on the fuselage side using reference pictures. Several attempts were needed as you see. The front gear bay will define the position of the future cockpit floor.

Sawing the single seater fuse walls off. Trying to get both sides at once but some fine tuning is needed afterwards anyway.

The bottom line can not be accessed with the saw so the scraper was used with repeated strokes until the wall was worked through.

Done choppin'. The gear bay roof was also sanded and thinned lightly and the dashboard removed.

Next steps will be to trim a cockpit floor and walls, followed the aft spine and front cover beneath the windscreen.

Regards,

Andy

[Dotcom]

Part two: Getting some plastic card to shape.

The cockpit floor width is defining the whole shape of the fuselage section. Test sitting is the Italeri kit's K36 bang seat.

From photo reference I made out the cross-section quite circular so from the floor width the cockpit back wall was drawn using a passer.

Again, testing with the seat for headrest clearance. The back wall still requires some fine trimming.

The front wall is also added. The flat area ahead of the front wall will be the base for the dashboard cover.

The rear spine. Using a first guess and several iterations of test-fitting and trimming, this piece of plastic card is ultimately bent and super-glued into place...

...like this. Tapering the edge provides more area for the glue, important since there is some stress to be held by the glue joint.

View from the side...

...and from the front.

Now the side walls could also be added. They required more test-fitting than the aft spine cover! The whole thing still looks quite edgy, so numerous filling and sanding sessions will be required to get the scale blend of the parts right.

As the cockpit layout will soon need to be designed, does anyone have pictures they are willing to share? Also, how does the crew get into the cockpit? Some sources say the crew enters through the front gear well and a door in the back wall of the cockpit as in the Su-34. But there is no sign of a ladder on the front wheel strut as opposed to the Su-34 variant. ??

Regards,

Andy

[Flankerman]

As the cockpit layout will soon need to be designed, does anyone have pictures they are willing to share? Also, how does the crew get into the cockpit? Some sources say the crew enters through the front gear well and a door in the back wall of the cockpit as in the Su-34. But there is no sign of a ladder on the front wheel strut as opposed to the Su-34 variant. ??

Regards,

Andy

It's looking GREAT Andy

Interesting approach on the cockpit - I just grafted on the Su-34 cockpit section and used the Su-34 canopy - but your method is probably more accurate.

The Su-27KUB cockpit is narrower than the Su-34 though - I don't know if the canopy is different ???

Re the crew access.... the Su-27KUB front gear retracts forward - unlike the Su-34 which retracts aft.

Access to the cockpit is the same though - via the front gear well.

But it doesn't have a ladder mounted on the front strut - note that early versions of the Su-34 didn't either - that only came later.

The Su-27KUB access ladder is a piece of ground equipment - same as on all the other Flankers.

Keep it coming....... :worship:

Ken

Edited August 7, 2011 by Flankerman

[HOLMES]

Andy,

This is simply SUPERB....and in 1:72 too...Your conversion is looking impressive and sleek..

Keep up the good work.

Will be back to see more

HOLMES

[Dotcom]

Progress has been very slow on this one the last weeks...other projects as well as job keeping me busy.

I'm getting closer to the canopy though...I have tried if I could fit in some clear plastic pieces cut from water bottles and other packaging but I didn't really succeed, none of the attempts got even close. Looks like I will get my first shots at vacuforming of at least thermo-forming.

I am mulling this one over a bit...fist step will be to find suitable material for the plug which will need to be easy enough to shape, and still stand high temperatures and provide a smooth surface. I was thinking of wood, but maybe there are special plastics for that purpose?

Cheers,

Andy

[Flankerman]

I was thinking of wood, but maybe there are special plastics for that purpose?

Andy,

I used the cockpit/canopy from the Italeri Su-43 on my KUB, but if you want to plug-mould a canopy, check out Ureol wood.

This is a high-density plastic wood used by professional model makers.

It carves easily and provides a smooth surface finish and is ideal for making masters.

I used it to make the MAWS Turret on my Su-30MKM conversion.....

Ken

[Bulldog 09]

Outstanding build Ken. I sure looks like you have your work cut out for you. Quick question for you on the Oreol wood, where did you purchase it?

Dave Fassett

[Flankerman]

Quick question for you on the Oreol wood, where did you purchase it?

Dave Fassett

I obtained a few offcuts from a friend who works in the commercial models industry.

They use it all the time.

I dunno where else you would get it - but there must be an online source???

Ken

[Dotcom]

Oreol doesn't shake out a supplier in a google search, but it might as well be named differently under a different brand. My usual plastics and composites supplier doesn't carry a similar material either.

My approach would have been to produce a wooden plug, make a negative from it with epoxy resin and use this negative to make the definite plug, also from epoxy resin. But thats a long walk compared to the advantages presented by Ken's solution. Hmm.

[Flankerman]

It's also spelt ureol - try that.

Ken