Tigger L-39 Conversion

[daveculp]

I saved the scariest part for last - trying to get the vacuform clear parts done.  My first plan for the windscreen was to cut out the right shape from the original part and fit it to the frame that I'd 3D printed.  That wasn't working well, so I went to plan B which is to remove the forward canopy bow and vacuform a new part that will serve as the windscreen and canopy bow (much as with any kit).  This gave me a chance to use the vac machine I bought a couple years ago and hadn't yet found a use for.

 

I 3D printed a form (buck?) in resin.  The form has a cavity on one side, only because it seemed wasteful to print it solid.  I thought the cavity would not need to be covered since it's on the side, but I was wrong.  The vacuum finds a way to get to the cavity somehow.  This mistake was easily recoverable though.

 

One problem I had was guessing what the thickness of the final part would be.  I started with 1mm stock and ended up with a 0.2mm part, which is thinner than I wanted, but I'll use it anyway. 

 

 

 

 

 

 

 

 

 

I'm hoping to get this project done for the local IPMS show on August 27.

[LSP_Kevin]

Super work, Dave!

 

Kev

[John1]

I'm unable to see the pictures in that last post.  Is it me?

[themongoose]

21 minutes ago, John1 said:

I'm unable to see the pictures in that last post.  Is it me?

Yep 

i can see them

[John1]

2 hours ago, themongoose said:

Yep 

i can see them

Weird.    I just came back to this post on my phone and I can now see them fine.    That is an outstanding model.   Immaculate paint work.  

[Dandiego]

Sweet! Vacforming, the last dark art. One that has eluded me as of yet.

 

Dan

[daveculp]

3 hours ago, Dandiego said:

Sweet! Vacforming, the last dark art. One that has eluded me as of yet.

 

Dan

 

I've done it once now, so I'm an expert    It turned out to be easier than I thought.  Some things I learned:

 

1)  Will the resin buck survive the heat when the hot sheet is lowered onto it?  Yes.

2)  Every imperfection on the buck's surface will be copied, even if only a few microns tall.

3)  There might be a way to estimate the thickness of the material after being stretched over the buck.  Maybe someday I'll work on that.  In general the taller the   buck, the more the material will be stretched.

4)  The working material, ZUVAS ZS02 PETG clear 0.04in sheet, worked well.  It's sandable, which is important for getting the edges trimmed.

5)  I'll look for some thicker material for next time.

6)  This material holds it's shape well.

7)  I should have packed the cavity in the buck with some material such as Milliput.

 

Dave

[daveculp]

After polishing the new windscreen and painting the bow it looks nice, but doesn't quite fit.  I'd use it if I had too, but I have enough time to try again.  The new reshaped buck is printed, and now I'm waiting for delivery of some thicker PETG material.

 

 

[Dandiego]

1 hour ago, daveculp said:

After polishing the new windscreen and painting the bow it looks nice, but doesn't quite fit.  I'd use it if I had too, but I have enough time to try again.  The new reshaped buck is printed, and now I'm waiting for delivery of some thicker PETG material.

 

 

That looks quite good.

 

Dan

[Renegade]

On 8/2/2022 at 1:01 AM, daveculp said:

After polishing the new windscreen and painting the bow it looks nice, but doesn't quite fit.  I'd use it if I had too, but I have enough time to try again.  The new reshaped buck is printed, and now I'm waiting for delivery of some thicker PETG material.

 

 

 

I do quite a bit of vac-forming and also use PETG as well. Mostly with 0.7mm thickness, and 1mm for ones that needs to accommodate for more stretching. PETG is quite tough, and you can almost push the windshield flat and still return to it's shape without cracking. You can easily flair the windshield wider without worries that it will be damaged. It might be a tad lower at the top afterwards. 

 

Cheers, 

John 

[daveculp]

Thanks, John.  I may try that with the thin windscreen.  In the meantime I'm trying a much thicker material, maybe too thick.  I just received an order of 3mm sheets of PETG, and have tried vac-forming it.  It actually worked even though the machine wasn't built for material that thick.  A modification to the hinge might work to allow the thick material to be locked in properly, but I just let the sheet heat up without being locked in to the carrier.  It worked out fine.  The final thickness is 1.5mm, a bit thicker than I need, but I'll still continue to sand it down to fit.  Maybe 2mm is the sweet spot for this use case.

 

Here's a photo of the new thicker windscreen getting sanded down to fit. 

 

 

[daveculp]

It's 99% done now.  Just some touch-ups, a couple canopy hold-open rods, and a good dusting to go.

 

I learned a lot during this project, but man, that was a lot of work.

 

 

 

 

 

 

 

 

 

[thierry laurent]

I love it!!! Excellent result. You did a really great job.

[daveculp]

8 hours ago, thierry laurent said:

I love it!!! Excellent result. You did a really great job.

 

Thanks, Thierry.   It only took one year, and that includes making the wings twice.  There is no way I could have done this without 3D printing.  Here's an after action report:

 

Kit:  Tigger 1/32 L-39

 

Scratch:  dorsal hump, exhaust area, extended tail cap, cockpit rough-out, lights on front of tip tanks, inlet splitters, rear cockpit sun shield

 

3D print:  landing gear, cockpit, tip tanks, antennas, pylons, drop tanks, trailing edges and control surfaces, extend L-159 nose, tail pipe and turbine, canopy mirrors

 

Vacuform:  windscreen

 

Aftermarket:

     Missile - Brassin, AIM-9M/L

     ACMI pod - Bandit Resin Factory, ACMI Pod Type D

     Pitot tubes - Master Model, L-39

     Seat belts - Eduard, MiG-29UB

 

Paint:  Mission Models MMP-010 Gelbbraun,  Vallejo 71.038 Cam. Medium Brown (? not sure - I don't remember ) , Vallejo 71.056 Panzer Dk. Grey

 

-- Dave

[tigger]

Bravo sir, your work is superb!