Tigger L-39 Conversion

[daveculp]

 

A couple years ago I spotted this airplane at the Nellis AFB airshow.  Obviously someone has to build one!  It's an L-159 operated by Draken International.  Draken calls it the Honey Badger.  Tigger has a vacuform model of an L-39 in 1/32 scale, and that's close enough to a Honey Badger to be the basis for a conversion.  This is my first vacuform build, so it's going to be a wild ride.  The Tigger L-39 parts:

 

 

Not shown here are the two copies of the canopy.  The barrel looking bit at bottom right is both left and right engine inlets.

 

The fuselage almost ready to glue together:

 

 

 

I applied some bondo to the rudder to thicken that part up.  When I sand the rudder down to give it a sharp trailing edge I want to have some material there to keep from making a hole.  I'm not going to build inlet ducting, but I did add a thin inner wall that will simulate the ducting.  I also (later) painted the inside of the fuselage black from there back to keep inquisitive eyes from seeing what's not there.  I added a cradle to hold up the front end of the tailpipe which will be made from 3/4 inch thin plastic tube.  Also added are tabs on both halves of the fuselage for gluing.  I've already cut the nose off in preparation for measuring the section shape so I can 3D print a new nose.

 

 

Fuselage halves joined today.  I've printed up two fuel tanks, two pylons for the right wing, and an ejection seat.  I plan on loading the airplane with two fuel tanks, an AIM-9M and a TCTS pod, so the outermost pylons won't be needed.  I don't plan on making a centerline pylon either.  There is still a lot of designing and printing to do:  landing gear, nose, tip tanks, and cockpit bits.  Fortunately the printed parts sit ahead of the CG, so the heavy resin parts will help keep the nose down.

 

I already made one mistake today.  I painted the seat beige as was shown in the one photo I've found of the whole seat.  I think the Draken airplanes have grey seats.  And speaking of the seat, does anyone know who makes the seat and whether there are any aftermarket seat belts that would fit it?

 

Shown are the colors I'm planning to use, Vallejo 71.074 Beige, 71.125 USAF Brown, 71.056 Panzer Dk. Grey.

 

The decals are going to be a challenge

 

[tomprobert]

This sounds like a great build - it's great to see another vac getting some attention. Not sure if it's just me, but I can't see your photos.

 

Tom

[Oldbaldguy]

15 hours ago, daveculp said:

 

A couple years ago I spotted this airplane at the Nellis AFB airshow.  Obviously someone has to build one!  It's an L-159 operated by Draken International.  Draken calls it the Honey Badger.  Tigger has a vacuform model of an L-39 in 1/32 scale, and that's close enough to a Honey Badger to be the basis for a conversion.  This is my first vacuform build, so it's going to be a wild ride.  The Tigger L-39 parts:

 

 

Not shown here are the two copies of the canopy.  The barrel looking bit at bottom right is both left and right engine inlets.

 

The fuselage almost ready to glue together:

 

 

 

I applied some bondo to the rudder to thicken that part up.  When I sand the rudder down to give it a sharp trailing edge I want to have some material there to keep from making a hole.  I'm not going to build inlet ducting, but I did add a thin inner wall that will simulate the ducting.  I also (later) painted the inside of the fuselage black from there back to keep inquisitive eyes from seeing what's not there.  I added a cradle to hold up the front end of the tailpipe which will be made from 3/4 inch thin plastic tube.  Also added are tabs on both halves of the fuselage for gluing.  I've already cut the nose off in preparation for measuring the section shape so I can 3D print a new nose.

 

 

Fuselage halves joined today.  I've printed up two fuel tanks, two pylons for the right wing, and an ejection seat.  I plan on loading the airplane with two fuel tanks, an AIM-9M and a TCTS pod, so the outermost pylons won't be needed.  I don't plan on making a centerline pylon either.  There is still a lot of designing and printing to do:  landing gear, nose, tip tanks, and cockpit bits.  Fortunately the printed parts sit ahead of the CG, so the heavy resin parts will help keep the nose down.

 

I already made one mistake today.  I painted the seat beige as was shown in the one photo I've found of the whole seat.  I think the Draken airplanes have grey seats.  And speaking of the seat, does anyone know who makes the seat and whether there are any aftermarket seat belts that would fit it?

 

Shown are the colors I'm planning to use, Vallejo 71.074 Beige, 71.125 USAF Brown, 71.056 Panzer Dk. Grey.

 

The decals are going to be a challenge

 

Dooooood!!!  If you can build this, you can make yer own dang seatbelts!

[daveculp]

9 minutes ago, Oldbaldguy said:

16 hours ago, daveculp said:

 

I already made one mistake today.  I painted the seat beige as was shown in the one photo I've found of the whole seat.  I think the Draken airplanes have grey seats.  And speaking of the seat, does anyone know who makes the seat and whether there are any aftermarket seat belts that would fit it?

 

Shown are the colors I'm planning to use, Vallejo 71.074 Beige, 71.125 USAF Brown, 71.056 Panzer Dk. Grey.

 

The decals are going to be a challenge

 

Dooooood!!!  If you can build this, you can make yer own dang seatbelts!

 

Hahha!  Yes, you're right, but I'd rather outsource that part.  I really don't like making seat belts.  I already ordered an aftermarket AIM-9M, and I'd like to use an aftermarket TCTS pod and the rails for both because there are some nice ones out there and it'll save me a lot of time.  Unfortunately the guy who makes the TCTS pods and rails only sells on Facebook, so i'm having trouble getting in touch with him.

[daveculp]

1 hour ago, tomprobert said:

This sounds like a great build - it's great to see another vac getting some attention. Not sure if it's just me, but I can't see your photos.

 

Tom

 

Tom, your browser is blocking them.  Some browsers have recently shipped with a setting that blocks "mixed content", which just means it won't load http content with https content.  Supposedly this is being done for security, but I believe its really being done for tracking content sources.   [insert Big Tech rant here].

 

One solution is to find that setting and turn it off.  Another solution is to use a browser which is not set up for tracking, like this one:  https://dissenter.com/download

 

 

[dutik]

Nice project!

 

Another ALCA:

 

 

Regards

- dutik

[tomprobert]

1 hour ago, daveculp said:

 

Tom, your browser is blocking them.  Some browsers have recently shipped with a setting that blocks "mixed content", which just means it won't load http content with https content.  Supposedly this is being done for security, but I believe its really being done for tracking content sources.   [insert Big Tech rant here].

 

One solution is to find that setting and turn it off.  Another solution is to use a browser which is not set up for tracking, like this one:  https://dissenter.com/download

 

 

Thanks for that - I can now see your pictures without issue. 
 

I’m really looking forward to seeing your progress with this. 
 

Tom

[daveculp]

Work on the fuselage is progressing.  I've printed a new nose.  Getting it to fair in nicely with the fuselage will take some putty and sanding.  Part of the problem is that the kit fuselage has a flat belly, whereas the real airplane has a rounded belly.  I'm not going to reshape the belly, so I'll just make it work with the putty and sanding.  In this photo the nose is installed and the cockpit opening is roughed out.

 

 

 

In the mean time I've been working on the other small bits.  Shown here are the seat, drop tanks, pylons (right wing only for now), missile launcher rails, sidewinder, and tip tanks.  The launcher rails (LAU-7, I believe) are taken from my KH OV-10 kit.  The sidewinder is from Brassin. 

 

 

 

 

 

Funny thing about the Honey Badger is I've seen photos of it sitting on the ramp with all gear doors closed.  I've also seen it with some or all doors open, so I'm still trying to decide how to pose the airplane.  I've decided the nose gear door will be closed, but I haven't yet decided about the main gear doors.

 

The drop tanks are each made of two halves, top and bottom, just as you'd expect from an injection kit.  That keeps the weight down but adds the difficulty of getting the seam just right.  For the tip tanks I decided to print them solid, accepting the added weight.

 

 

 

 

I am a bit concerned about the weight because the landing gear will be 3D printed as well, and I'm not sure how much weight they'll be able to hold.  All three gear have a trailing arm design which makes it even more concerning.  On the plus side all three gear can be inserted into holes in the airplane without glue, so if they break it'll be easy to remove them and replace them with gear printed with a different resin.

 

 

 

 

 

[LSP_Kevin]

Awesome project, Dave!

 

Kev

[Pete Fleischmann]

With a couple hundred hours in the L-39, I can tell you that The L-39 at rest typically has the gear doors closed, flaps up, and speedbrakes up. We can open all of the gear doors on the ground for inspection/maintenance with the emergency gear extension handle with the gear down and hydraulic power available. Speedbrake extension on the ground is also possible with the engine not running but hydraulic pressure on the system.

Cool build of a cool jet! Haven’t flown the Honey Badger yet, but would love to!

 

cheers

Pete

 

[Dandiego]

OMG a vac!

 

Dan

 

[daveculp]

1 hour ago, Pete Fleischmann said:

With a couple hundred hours in the L-39, I can tell you that The L-39 at rest typically has the gear doors closed, flaps up, and speedbrakes up.

 

 

Well Pete, that makes the L-39/L-159 the perfect subject for a vacuform build

 

One other thing I've noticed while looking at online photos of the L-159 is that the part of the main gear well that contains the strut has its own set of doors (in addition to the door that's attached to the strut).  I've never seen this on any other airplane.  It means the belly is a smooth as can be when the gear are down.  I've been racking my brain trying to figure out why it has the extra pair of doors.  Maybe it's to keep the tires from throwing mud/debris up into the wells?

 

-- Dave

[Pete Fleischmann]

14 minutes ago, daveculp said:

 

Well Pete, that makes the L-39/L-159 the perfect subject for a vacuform build

 

One other thing I've noticed while looking at online photos of the L-159 is that the part of the main gear well that contains the strut has its own set of doors (in addition to the door that's attached to the strut).  I've never seen this on any other airplane.  It means the belly is a smooth as can be when the gear are down.  I've been racking my brain trying to figure out why it has the extra pair of doors.  Maybe it's to keep the tires from throwing mud/debris up into the wells?

 

-- Dave

Hi Dave-

yes. Those are mechanically linked and spring loaded, so you can pull them open by hand.

Although I don’t know for sure; I suspect you are correct. There is a section in the dash-1 specifically addressing operations from unimproved airfields, and you thoughts certainly make sense-

 

cheers

P

[daveculp]

The Honey Badger has a single seat cockpit, the rear cockpit being full of electrical equipment with a sun shade built in.  Here's a photo from wiki commons (credit Thomas Del Coro):

 

 

 

One thing to note in this image is that the rear canopy is raised up a few inches.  Also, note that the crease where the fuselage side meets the canopies extends aft and disappears behind the splitter plate.  So, the kit's one-piece canopy part needs to be cut up so the aft canopy can be raised.

 

 

 

Locating the wings so I know where to cut open the fuselage.  

 

 

 

 

I cut out the belly of the airplane so that the wings can be attached at the correct angles.  It also make it easier to install a spar.

 

 

 

 

I gave the bottom of the wing 4 degrees dihedral.  That should give the top surface of the wing about 1.5 degrees diredral.  The wings look pretty strong, so I only need to run the spar out to the main landing gear mount points.

 

[daveculp]

I have the cockpit roughed in and am printing up the small bits.  I've made the front panel, pedestal and pedals all one piece.

 

 

 

I've decided to make decals for the instruments, so they'll be 2-dimensional.  The left console will have the throttle designed in, but the rest will be decals.  I'll wait for installation until after the exterior is painted.

 

 

I know one of the big chores when making a vacuform model is getting the wings and tail surfaces the right thickness, and giving the trailing edge a sharp edge.  Judging by the amount of work this process has already required just for the rudder I don't think I'll have the patience to shape the wings.  So, alternate plan is to cut off the trailing edge and either scratch build or print new ailerons and flaps.  Either way will work.  Printing them will be less work but will weigh more (and they're behind the CG).  I'm inclined to print just because I like repeatable processes, but I've discovered that in the vacuform world the printed parts are all designed to fit the current model - and I don't think I could make the vac parts the same way twice.

 

By the way, the more work I put into the rudder the more likely I'll just cut it off and make one as well.

 

 

 

The drawing seems not quite accurate.  From photos I've seen the aileron leading edges aren't swept - they go straight out just like Tigger molded them.

 

EDIT:  I later found out I had installed the upper halves of the wings on the wrong sides!  Oops.

Edited September 29, 2021 by daveculp
Don't want people to think this is correct.