1/18 Scale P-51B 3D Print Build

[Gazzas]

Gun panels look sweet!  Wingtips, too.

[Philbucknall]

On 10/19/2024 at 7:20 AM, airscale said:

Hey Jay - i use OHP film - it's paper thin and will take a 180 degree bend without cracking or discolouring

 

Thats what goes in all our decal packs for instrument glass

 

Sorry - a little off topic but they still make OHP film????? I recall doing my final dissertation back in 99 on OHP film. Didn't know there was even a market for it anymore.

[Thunnus]

Great work on the various details, Jay!  Such a variety of materials on your builds.  Gun barrels look suitably lethal.

[JayW]

On 10/21/2024 at 6:58 AM, Philbucknall said:

Sorry - a little off topic but they still make OHP film????? I recall doing my final dissertation back in 99 on OHP film. Didn't know there was even a market for it anymore.

 

Apparently so!  I now have more than I will ever need.  

 

To that point, I want to report on two little sub-projects - the landing light panel, and the wing tips. 

 

Last post I showed my first attempt at the landing light wing LE panel, with its severely contoured glass.  Severely contoured - here is the engineering drawing

 

  

 

At 1/18 scale the formed radius at the LE highlight is about .035 inch.  It's tight, and I have found that my first material selection - Evergreen clear sheet .005 inch thick - just cannot handle it without crazing and discoloring.  Even with heat forming.  Recall this picture:

 

 

 

 

The highlight is basically white, not clear.  A good try, and I suspected this might take several tries.  It did.

 

So upon the recommendation of Airscale and Dodgem37 I ordered some "OHP" film.  "Overhead Projector".  This stuff is .004 or so inch thick if I recall correctly - close enough to the .005 inch my parts are designed to accept.  Supposedly this stuff can take a severe forming, even a fold, and will not craze.  That turned out to be so.  Thanks guys for that - it is so good to be with LSP.

 

Before I show my latest result, I want to say this effort was very very frustrating and worrying.  It was great to not have to worry about crazing, but that was just one of the challenges resolved.  The process was kind of long and labor intensive, with lots of opportunity to screw up.  And screw up I did, often.  One particularly frustrating episode was when I was handling a freshly hot-formed and cut out piece of OHP - lots of time and effort put into that part - and ping!!!  It disappears into the ether.  The formed part made for an excellent spring.  I thought I heard it careen into the trash can, so I searched it without success.  When small opaque parts ping away, they are hard enough to find.  A clear part - forget it!  Start over.  Anyway, this transparency is two parts - a wider base layer and an outside layer, bonded together with 2-part epoxy.  It is the outside layer that has the oval shape.  I did this so that the outer layer can be right on contour.  Just like the actual part (see the drawing above).  But that introduced a challenge - to bond the two parts together without any bubbles or disbonds which would spoil the clarity.  I would fail miserably on this, until I finally got one right.

 

Finally, all the stars aligned, and I got this:

 

 

 

It is not perfect, but it's pretty good, and I am happy enough with it.  I am also relieved.  That little PITA was as challenging as anything I have done on this long project to date.  One might ask - why did you skin it in alum Jay?  When the rest of the LE will not be skinned?  Because, as Antonio pointed out, this panel appears to have not been filled and painted silver like the rest of the wing, for some reason.  So that is how Cripes A Mighty will be.

 

Also I moved the wing tips forward.  Last post I showed some really nice 3D printed tip fairings.  The tip assemblies themselves were then digitally designed and 3D printed:

 

  

 

Printed up pretty nice.  Note one of the panels has the three holes for ID lights.  That all comes later.  Here are the tip assemblies ready for installation onto the wings:

 

 

  

 

The tip fairings fit OK but not perfect.  P-38 bondo has been applied to fill in gaps - this tip is going to be painted silver, even the aluminum paneling.   I limited any fastener punching to aft of the 40% chord line, except the tip-to-wing fastener line along the edge of the aluminum skin. 

 

 

The above picture shows the interesting wing airfoil of the P-51 where the thickest part of the airfoil is significantly further aft than standard airfoils of the day.  The "laminar flow" airfoil.  And one reason this bird was so speedy.  I am very proud that this wing has the proper airfoil shape.  Oh, and you also see the metallic rings for the ID lights.  They go on later.

 

Here, I show what P-51 experts know about - external re-inforcement stiffeners for the trailing edge, in the vicinity of the ailerons: 

 

 

These are separate parts bonded on, and were a pretty challenging Rhino modeling exercise.  I would love to know the story behind these parts - what problem did they fix....

 

Wing and tips to date:

 

 

 

Next I will be doing some acreage alum skinning on the wing surfaces.  And I mean acreage.  This will require the wing tips to be installed, which will turn my wing into a long boomerang-like object that will bump into everything.  So I must be vigilant.  The big thing this is all leading up to is wing-to-fuselage join, and construction of the inboard leading edge and gear bay.  A big deal.

 

See y'all later!

 

 

 

 

  

Edited October 26, 2024 by JayW

[JayW]

On 10/18/2024 at 1:19 PM, geedubelyer said:

How resistant to temperature is your resin?

 

I never answered this Guy.  My male/female bucks appear to have made it through quite a few boiling cycles without an apparent deformation.  

[geedubelyer]

Awesome.

 

Congratulations on solving the clear part conundrum. 

We all knew you would even if you didn't. 

[JayW]

Greetings people.  Last post I declared I was going to acreage skin the wing box, all the way out to the tip.  Which would require tip installation.   Tip installation would add about 5 1/2 inches to the already long (19 inch) wing span.  That is something I do not relish at all.  Working on very long parts is so problematical on a busy work bench with limited space.  So I am hesitant to do that right now.  On the one hand I want to see the full span wing, with ailerons.  That would be really exciting.  On the other hand, I want to minimize the chances for more damage, almost a certainty on the full span wing.   So what I think I am going to do is move my focus onto inboard LE design and build-up, and in parallel digital development of the aft fuselage and empennage surfaces in Rhino.  It is becoming time to do so, and that would complete my P-51B surfaces. 

 

I did however do some "acreage" skinning inboard of the tip assembly.  Here is for example a lower skin panel wing sta 75 to 135.5 (RH side) - it was a toughie:

 

   

 

It has holes for the pitot mast, shell and link ejection, and bomb pylon attach.  This is one of ten aluminum panels I fabbed and installed, this one being the largest along with its opposite.  Here they are for your inspection - 

 

LH gun access panels upr surf:

 

 

RH gun access panels:

 

 

Note one of the panels has a piano hinge.  Note also the three access doors (the fourth is a riveted panel) lack fastener marks, except a few.  That is because they are largely assembled with spot welds, which I think are not very visible, especially with paint.  And these will have silver paint.  The rivet marks that do exist, are almost all for 1/8 inch flush head rivets, which are small (.216 inch head diameter full size), and require a quite small punch. 

 

Lower skin panel WSta 75 - 135.5 LH:

 

   

 

And RH side:

 

 

Note the flaps are taped in place.  And again - the rivet marks depict 1/8 inch rivets almost without exception.

 

Back up to take a shot of all the aluminum (flaps too):

 

 

 

In addition to the aluminum skinning, I have filled in some gaps and smoothed some areas needing smoothing, with P-38.  Getting it ready for that silver paint not too long from now.

 

So now, I will let the wing tips gather dust for a little while, and get to work on the IB LE.  It will be the most challenging part of the whole wing.  And a project I have been waiting for almost since I started this adventure.  Take care, and stay tuned for major adventure.

Edited November 2, 2024 by JayW

[SwissFighters]

Looking really, really good Jay!

Thanks for sharing,
Tony

[JayW]

So the IBLE - Inboard Leading Edge.  When I began this project about a year and a half ago, this was one of the sub-projects I was looking forward to with great anticipation.  The IBLE and landing gear bays are the grand central station of the P-51.  All systems are represented in it, as is a whole lot of exposed internal structure - ribs, skin/stringer, and the backbone of the wing - the front spar.   And, it is the intersection of several main components - the wing box, the wing leading edge, the fuselage, the engine cowl section, and the wing-to-fuselage fillet fairings.  These components have been (or will be) built up independent of each other, with the hopes and prayers that they will integrate properly.  

 

So we already know the wing box will attach properly to the fuselage.  What I don't know (or didn't know) is if the leading edge will match up to the engine cowl section and firewall.  Rhino says it should, and I have a plan (or a concept of a plan 😁)  but I wanted to know right now if it will be successful, before I go off and add tons of detail to parts like the centerline rib, the leading edge ribs, and the nose beam.  So I made some test parts - incomplete versions of parts that are currently undergoing detail design in Rhino.  Here they are:

 

     

 

What you see there are four parts - the LH side IBLE nose skin already bonded to the IBLE nose beam, the LH side upper IBLE skin/stringer panel, and the all-important centerline rib.  All parts complete enough to do this fit-up test.  

 

To check fit-up, I first had to temp install the engine cowl and firewall to the fuselage with tape.  Then remove the protective faux-panels from the wing leading edge (the ones that protect the gear struts).  Then tape in place the nose beam, centerline rib, and upper skin panel, like this:

 

 

So far so good.  Now to try mating up this wing assembly to the fuselage and engine cowl:

 

    

 

And wow!  There is a whole lotta success represented in that picture above.  The centerline rib fits perfectly, nestled between the front spar and the firewall.  The nose beam and nose skin fit beautifully with the nose gun panel and the engine cowl's fillet fairing - better than I had even dared to hope for, and a source of great angst for months upon months.  No longer.  And the upper skin/stringer panel needed some trimming on its outboard end, but fits well enough against the wing box upper panels and the centerline rib and the nose beam. 

 

The view from above: 

 

 

A bit of P-38 to perfectly match up the fillet with the nose skin (I always knew that would be needed), but not much.  That task is a ways off.

 

Pan back - this is an opportunity to remind us all of the end game:

 

 

I cannot adequately describe how relieved I am with this development.  The plan is working.  This test allows me to proceed with confidence with wing IBLE build-up without having to do a wing-to-fuselage join until after it is nearly complete.  Much easier.  Oh, and perhaps you can see from the picture above that I have a relatively compact wing/fuselage/engine cowl assembly to work with.  I am glad I waited to install the wing tips.  And I will wait as long as I can to do the aft fuselage and tail. 

 

The test parts you see here will go the way of the other test parts - the trash bin.  They will be replaced with much more detailed parts along with scores of other IBLE parts.  Stay tuned for that and more! 

 

 

 

 

Edited November 4, 2024 by JayW

[LSP_Kevin]

Fantastic work, Jay! Way above my pay grade.

 

Kev

[GMK]

So good, Jay. An absolute masterpiece of conception, design, & finish.

[Rocat]

I'm happy the plan is working! Great work

[Henricus]

Well... You are setting new rules for this hobby!

Looking at this, who will assemble a standard plastic kit with the same enthusiasm?

Very inspiring, congratulazioni

Enrico 

[Gazzas]

Wonderful stuff, Jay.

 

[JayW]

I have been working hard detailing the centerline LE rib - I sure hope everything prints up OK - asking alot.  Here are the Rhino models if interested, report out on the printed parts to follow maybe tomorrow:

 

 

 

There will be ALOT of parts.  I will combine everything I think I can.  Ought to be one interesting assembly!  Stay tuned.

 

 

 

Edited November 11, 2024 by JayW