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Tigger L-39 Conversion


daveculp

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The 3D printed wing trailing edge came out just right.  I've decided not to worry about weight any more.  If I have to pose the airplane on a stick then so be it.  Maybe I'll learn how to make brass gear.

 

 

trailing-edge.jpg

 

The resin parts can be scribed just like styrene.  The right side is printing now.  I spent much of the day carving out NACA scoops and drawing up the instrument panel decals.

 

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47 minutes ago, LSP_Kevin said:

I don't see anything unrecoverable, Dave. What's up?

 

Kev

 

I installed the wings backwards.   The fuselage is wider at the rear, so it can only go on one way.  This is what i get for not marking the parts with an arrow pointing forward.  I considered cutting the wings off, but there's enough CA glue there to hold a real L-159 together.

Edited by daveculp
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2 hours ago, daveculp said:

 

I installed the wings backwards.   The fuselage is wider at the rear, so it can only go on one way.  This is what i get for not marking the parts with an arrow pointing forward.  I considered cutting the wings off, but there's enough CA glue there to hold a real L-159 together.

 

Ouch! Does that mean you installed the flaps and ailerons on the wrong edge of the wings?

 

Kev

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17 minutes ago, LSP_Kevin said:

 

Ouch! Does that mean you installed the flaps and ailerons on the wrong edge of the wings?

 

Kev

 

The lower surfaces are installed correctly, but the upper surfaces are on backwards.  I then cut the upper surface ailerons and flaps off based on the location of the molded-in recess marking the aileron hinge line.  Then I flipped it over and cut the bottom surface.  End result is the upper surfaces are cut correctly but installed backwards.  The lower surfaces are installed correctly but cut on the wrong edge.

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While I await a new kit to re-do the wings, here's the progress on the fuselage:

 

rear-fuselage-progress.jpg

 

For conversion to the L-159 type:

 

1.   Make the exhaust area straight (parallel to red line shown)

2.  Add a filet below the rudder that extends all the way back

3.  Add a small fairing for a rear-facing light

4.  Finish up the dorsal hump

 

For general additional detail:

 

5.  Cut out the NACA scoops

6.  Cut out the elevators

 

I won't print a new set of elevators until the horizontal stabs are installed.  That way I'll have a final set of measurements to use.  And I won't install the horizontal stabs until the aft fuselage is close to complete.

 

 

While looking at photos of the L-159 on the internet I noticed something unexpected.  The wing pylons seem to be perpendicular to the underside of the wing rather than parallel to the local vertical (gravity vector).  It's only about 4 degrees of difference, but I wonder how common this is?  Maybe it's like this on all airplanes and I just never noticed before?  I've always assumed the pylons are vertical.

 

pylons2.jpg

 

(original photo credit:  Jan Kouba Czech republic 2013.  All rights reserved.)

 

 

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I think most pylons fit this way because they are milspec standard and interchangeable between wings and other aircraft, so they are not “handed” like they would have to be if they were perpendicular to the ground.  Does that make sense?

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3 hours ago, Oldbaldguy said:

I think most pylons fit this way because they are milspec standard and interchangeable between wings and other aircraft, so they are not “handed” like they would have to be if they were perpendicular to the ground.  Does that make sense?

 

That makes perfect sense.  I assume then that the sway braces in this case will also be angled 4 degrees from horizontal, and the store will hang 4 degrees off from the pylon centerline.  In the photo it looks like the gun pod hangs this way.

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