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

[JeepsGunsTanks]

This is going to be so amazing when done! So far its magical.

[airscale]

amazing Jay, truly..

 

looks so good and we all know every micron is right where it should be

 

Question - when you print the body parts what printer setting do you use? I use 0.030 for detail parts and 0.050 for body parts that will be skinned / covered

 

It literally prints twice as quickly and even big jobs are only a few hours

 

 

Peter

[Oldbaldguy]

Ref the holes left along the spine after the Malcolm hood mod:  since this was essentially a field mod, logic would say that the three holes were covered with simple patches cut to fit if they were covered at all - sheet metal airplanes tend to have lots of holes in them.  Neatness may not have counted.  I’d be very careful about using a restored airplane as a reference in this case because the metal work on them is always so very good.

[JayW]

On 3/24/2024 at 4:56 AM, airscale said:

Question - when you print the body parts what printer setting do you use? I use 0.030 for detail parts and 0.050 for body parts that will be skinned / covered

 

Hi Peter!  No doubt a response to my "took all day to print" comment. 

 

My settings for standard gray resin:

 

 

 

 

I actually have not been using the .03 mm thickness for anything.  Always .05 mm.  Perhaps I should for the tiny parts.  However I would have to guess at the exposure times.  What is yours?

 

The crown skin, when turned vertical, was about 3.5 inches tall, or about 90 mm.  Doing some arithmetic, I get these times (in seconds) for the steps in a single print cycle:

 

Exposure time - 3.5 s

Rest time after retract - 1 s

Lift time - 4.9 s

Retract time - 3.2 s

 

That gives total time per layer = 3.5 + 1 + 4.9 + 3.2 = 12.6 seconds

Total layers = 90/.05 = 1800

 

Total time = 1800 x 12.6 sec = 22,680 sec, or 378 minutes, or 6.3 hours.  But the several bottom layers are 35 sec exposure time plus the same lift and retract times - so total time is more by about a half hour.   So it was just short of 7 hours. 

 

 

 

 

 

 

 

Edited March 27 by JayW

[JayW]

39 minutes ago, Oldbaldguy said:

since this was essentially a field mod, logic would say that the three holes were covered with simple patches cut to fit if they were covered at all - sheet metal airplanes tend to have lots of holes in them.  Neatness may not have counted.  I’d be very careful about using a restored airplane as a reference in this case because the metal work on them is always so very good.

 

Hi OBG.  Agree 100%.  Wouldn't it be fun to get our hands on the kit instructions and/or drawings?  I had a ball incorporating the dead cowl flap mod on the Corsair - I actually had the drawing if you will recall. 

 

It would not be difficult for the field mod to cover the holes for the light and the insulator using an interior rough contoured doubler with a rivetted patch same thickness as the skin buildup, shaped like the holes.  And using the existing fastener holes with flush rivets or bolts to attach the doubler to the airplane.  Same for the antenna mast hole, except it has no skin fasteners, so drill new ones.  I will probably assume that to be so, and just duplicate that when I skin this beast.  Will be easy.  And thinking about it, that would be the Cadillac fix.  The Chevy fix would be simple exterior patches, as long a there was enough clearance to the lip of the hood as it slides aft. 

 

Also correct with resto's.  Pristine metal work as if the hood is an in-production feature.  Here is one:

 

  

 

No patches.

 

BTW - the wooden antenna mast is getting replaced with a whip style antenna further aft.  I will have to do that one day.  Something like this:

 

And I don't see any patched holes on that aircraft either.  But its also a resto.  

Edited March 24 by JayW

[airscale]

Hi Jay

 

I have no real idea actually - i watched a set up video when I got the machine for the best results for detail and after plugging that in all I ever change is the 0.030 and the 0.050

 

here is the rest..

 

 

should definately use 0.030 for detail, it results in near perfection with zero striation

 

good luck!

 

Peter

[scvrobeson]

More fantastic progress Jay! I'm sure you'll crack the mystery of the quarter windows

 

 

Matt 

[LSP_Kevin]

8 hours ago, airscale said:

I have no real idea actually - i watched a set up video when I got the machine for the best results for detail and after plugging that in all I ever change is the 0.030 and the 0.050

 

Interesting that you say that, Peter, as for the smaller layer size, the layer exposure time should ideally come down, as thinner layers don't need to be exposed for as long. But if you're not seeing any evidence of overexposure, and aren't bothered by the longer print times, then I'd say carry on!

 

Kev

[JayW]

2 hours ago, LSP_Kevin said:

Interesting that you say that, Peter, as for the smaller layer size, the layer exposure time should ideally come down, as thinner layers don't need to be exposed for as long. But if you're not seeing any evidence of overexposure, and aren't bothered by the longer print times, then I'd say carry on!

 

So Peter's exposure time for .03 mm layers is 2.5 sec.  Mine is 3.5 sec for .05 layers.  I guess my question would be are the prints with .05 layers and 2.5 sec exposure underexposed.....   I think Peter and I are using the same gray resin......  I might just experiment with .03 layers on the next batch of small parts, coming soon - with 2.5 sec exposure.  

[LSP_Kevin]

11 minutes ago, JayW said:

 

So Peter's exposure time for .03 mm layers is 2.5 sec.  Mine is 3.5 sec for .05 layers.  I guess my question would be are the prints with .05 layers and 2.5 sec exposure underexposed.....   I think Peter and I are using the same gray resin......  I might just experiment with .03 layers on the next batch of small parts, coming soon - with 2.5 sec exposure.  

 

Unfortunately every printer and resin combination is different - even with different machines of the exact same model! This is why performing exposure tests is so important, and why they really should be done whenever any variable in the mix changes. Even ambient temperature can make a big difference, with colder temperatures requiring longer exposure times. I'm taking it from Peter's comment that he only changes the layer height to mean that the exposure time remains at 2.5s. For comparison, on my OG Saturn with 50 micron layer height, my exposure time is 2.9s.

 

Kev

[JayW]

Status update - 

 

I just ordered a set of aft cockpit windows from Shapeways.  The transparencies I made myself just do not cut the mustard.  Good lord this model is getting expensive.  The price of those two windows is as much as a pretty nice 1/48 kit!  So was the Malcolm hood.

 

Radio equipment - what goes in there and what does not?  I got the story from the P-51B/C Erection and Maintenance manual, and the Operating manual.  So WW2 fighters essentially have two kinds of radio equipment - communications and identification.  For the P-51B/C, its communications radios were the familiar SCR-522 VHF equipment, and the long wave Detrola equipment.  But the ETO never used the Detrola, and that equipment was removed including the long cable extending from the forward fuselage crown to the tail.  Too many modelers go through the unnecessary trouble of making that wire and modeling the associated equipment in the cockpit if they are modeling an ETO aircraft.  Not me.  As for identification equipment, there were several versions of IFF (Identification Friend or Foe) equipment provided.  Most of it resided behind the pilot armor on the lower radio shelf, and some of it on the RH side of the cockpit.  BTW - it is this equipment that required the detonation switches you see in WW2 aircraft cockpits.  The IFF stuff was top secret, and in the event of a survivable crash in enemy territory, it had to be destroyed.  But once the fuselage tank was introduced, its volume wiped out that space for the IFF radio equipment.  So, the equipment was simply removed, and everything else that was in that compartment (like the battery) was moved to the upper radio rack behind the pilot's head.  Period.  No IFF capability for those fighters.  So just the SCR-522 stuff and nothing more.  You will see some of that equipment (what resides on the RH side of the cockpit) next update.   

Edited March 26 by JayW

[Jim Barry]

Yeah, Shapeways does like our wallets! 

[JayW]

Remember this?

 

 

That was posted on Nov 21 of last year - four months ago.  The finished engine cowl section - painted and all. 

 

There is still some more blue that has to be applied to this model - around the windshield, and the uppermost panels between the windshield and the firewall, which is the aft end of this sub-assembly.  You will recall that I, in my impatience, just had to apply a final topcoat to the forward end of this P-51.  I couldn't wait to show off the blue-noser blue.  Well now it occurs to me that the paint cocktail I ended up with is not going to wait forever for me to complete the forward fuselage of this uber-complex model.  It has already been four months since I shot that paint, and it will probably be something like another four months to complete the forward fuselage such that I can skin it in aluminum to match the finished engine cowl section, and paint the rest.   I am screwed if the paint decides to dry up; I have no confidence I can match up a new batch to the old batch.

 

To review, this is the combination:

 

Tamiya medium blue XF-18 (49% plus)

Vallejo medium blue 70.965 (49% plus)

Vallejo white 71.001 (quite a few drops, but quantity unknown)

 

No way would a new batch be perfect.  Were it all Tamiya, I would not be stressing as much about the shelf life.  But it isn't.  I just don't know how long its shelf life is.  So far it seems fine after four months.  Am accepting comments from the master painters here who are tuning in.  

 

So I think I am going to hit the pause on the assembly plan, and try to get the rest of the blue on sooner rather than later.  To do that, I have to mate up (dry fit) the engine cowl section to the forward fuselage section in its current state, and skin the forward portion of the forward fuselage section to match the already skinned engine cowl section.  I do not trust using the jig to trim the fuselage section aluminum skins.  In theory it would work, but in practice, I don't think I will get a great match to the engine cowl.  And it needs to be good.  In order to do that, I must be able to assemble the two nearly complete sides of the forward fuselage section, and the fully complete windshield surround section, without the benefit of the fuselage jig.

 

I think I know how to do that:

 

1.  3D print the firewall, with its four posts that match the holes in the forward ends of the four longerons.  Just like the forward end of the jig does now.  My firewall is already mostly designed in Rhino.  It won't take much to finish it and print it.  Fit the firewall to the engine cowl and then the forward fuselage can be fit to the firewall, and taped in place.   

2.  Rhino design and print a mock station 200 frame, just a plate with four posts to match the holes in the aft ends of the four longerons.  Again, just like the aft end of the jig does now.  This part can be taped to the side panels and will stabilize the aft end of the side panels and keep them in place. 

3.  Rhino design and print a simple square plate with four posts that match the four wing mounting points at stations 104 L&R, and 146 L&R, on the lower longerons.  Again, just like the jig does now.  Tape this to the side panels also.

4.  Tape the windshield onto the side panels.

 

This should give me an accurate forward fuselage assembly that holds shape acceptably and can be fit onto the engine cowl, complete enough to skin the forward end of it, to perfectly match.  Maybe skin just the windshield surround, since the blue doesn't extend down to the side panels.  Once the trim is final, mask up for the remainder of the blue, paint it, and problem solved.  

 

That is if there is a problem at all.  If the shelf life of my paint is alot longer than a half year, then I don't need to do this out-of-sequence work.   What do you think?        

Edited March 28 by JayW

[Landrotten Highlander]

perhaps this is a stupid idea, but what about putting the paint in the refrigirator (i.e. where you keep your milk and foodstuffs you plan to eat quickly, not the place where you freeze the things)?

Perhaps that will slow down the chemical reaction that leads to the passage of shelf-life-time-thingemything?

[JayW]

Let's get up to date!  There have been some issues, at least in my head, that needed to be resolved.  One, the side windows.  I don't like the ones I did myself.  So I await the 3D printed transparencies from Shapeways - due in a week or so.  It is my hope they turn out as nice as the Malcolm hood has.  Two, blue paint that has been sitting for months - I feel I need to finish up the blue painting while the paint is still healthy.  Because if it dries up, I will have great difficulty matching up a new batch.

 

In the mean time, I have been working on the RH side of the cockpit wall where we find the radio gadgetry and some electrical equipment.  Recall in previous posts that radio equipment for US ETO fighters was pretty simple especially for Mustangs with fuselage tanks, where the tank has used up alot of space where radio equipment went.  Hence all they really had was the VHF SCR-522 equipment.  Missing was IFF (identification friend or foe) equipment and low frequency radio equipment (the Detrola).  The VHF SCR-522 consists of the following components:

 

Transmitter-receiver - the big box behind the pilot's armor plate on the upper radio rack (to be done later)

Dynamotor - a slightly smaller box also behind the pilot's armor plate on the upper radio rack (to be done later)

Jack box - a version of this is included in the cockpit RH side stuff

Radio control box - this item is included in the cockpit RH side

Antenna mast  - the familiar nasty looking spike antenna we see on all ETO fighters.  Although this will be replaced by a whip antenna as part of the Malcolm hood modification.  

 

Here is the finished radio and electrical equipment on the cockpit RH sidewall:

 

 

 

 

 

You see there in the forward-most bay the dominant black main switch box, below it the interior green radio junction box, and just aft of the radio junction box the fabric covered connector panel.  The next bay aft has the SCR-522 radio control box with the red buttons, below it the jack box bracket, and below the jack box bracket the detonator box, and aft of the detonator box the silver mic adaptor box.  I attempted to wire this equipment but the drawings are not very good - hope I got it close....  I may or may not include microphone cords.  All this stuff except the fabric covered connector panel, and the red buttons, are 3D printed from my Rhino models, as usual for this build.  You also see radio support brackets (3D printed), at least the one with a blank area where other radio equipment would go (IFF stuff), but is missing on this aircraft.  Lastly another shout-out to Peter for the decals.  They are marvelous. 

 

At this point, the sides of the cockpit area are pretty much complete.  Here they are:

 

   

 

Late additions are the flare gun stowage bag on the LH side (with the two brass buttons), and the map case on the RH side.  The map case is just simple plastic sheet parts.

 

I must mention - for those of you who followed the Corsair build, you may agree when I say the P-51 cockpit is much more simple than the Corsair cockpit.  Mind you, I still have the floor to do, and some other stuff hanging off the IP panel, as well as the pilot's seat and armor plate.  But there just is not nearly the amount of complexity.  The Corsair cockpit was a nightmare!

 

All right - I have been nervous about the blue paint.  So what I have decided to do is to go ahead and paint the remainder of it on the windshield surround part - this:

 

  

 

In order to do that, the rest of the skinning has to be done.  And in order to do that, I have to fit this part to the already completed engine cowl, and tidy up the panel line between them.  In order to do that, I feel I have to tool these parts up to one another.   So I designed and built another jig:

 

 

This new jig is part of a simpler plan than the one I laid out a couple posts ago.  This way, I can still utilize the main jig (minus the firewall bulkhead).   Construction and concept are similar to the main fuselage jig.  That new bulkhead has a post on it that fits into the prop shaft hole in the nose of the engine cowl.  Which will assure a proper orientation of the engine cowl to the forward fuselage both up/down, and sideways.  The bulkhead can slide fore and aft in the center slot (the mounting holes are slotted), similar to the two end bulkheads on the main jig.  This jig, or better an auxiliary jig, will bolt onto the existing fuselage jig that is working so well for me.  Like so:

 

 

 

 

Note that the firewall bulkhead has been removed.  In its place is to be the actual firewall (actually a simplified version of it just for this exercise):

 

 

Two parts - a top and a bottom - 3D printed.  They fit onto or into the aft face of the engine cowl, which has just awakened from a months long winter hibernation.  Note the firewall has the same four longeron posts that the jig bulkhead has.  The beauty of digital design - the locations are identical to the zillionth of an inch.  Much fiddling was required to get the firewall parts to fit perfectly into the big engine cowl part.  Dimensional accuracy on 3D print parts is not quite perfect - parts grow just a bit, such that male and female parts when designed without any gaps often clash a bit with one another.  That was the case here.  

 

Before using this new aux jig, I reloaded the fuselage side panels and windshield surround into the main jig, minus the firewall bulkhead, like so:

 

 

The holes in the longerons are loud and proud in that picture - waiting to mate up with that new firewall.  And here is the new aux jig in action with the engine cowl plus firewall loaded:

 

  

 

 

f

 

The jig is now about 13.5 inches long, and it is unwieldy to jockey around.  Big model.  The concept works great, but I got a bit of a surprise - tapering gaps at the firewall interface:

 

 

 

 

Both sides.  Not bad, but it makes me wonder if something is in error.  

 

I do notice that once the aux jig is clamped up and bolted to the main jig, despite my efforts to get it just right, its forward end has risen up a few hundredths of an inch above the flat desktop.  That would cause that tapered gap, and maybe that's all there is to it.  So I am going to shim between the jig surfaces to eliminate the condition, and hope that tapered gap disappears.  Actually it matters little - when I skin the fuselage side panels, that gap will be hidden, and turn into a normal panel line.  Still, I want that Mustang nose to be spot on relative to the rest of the model.

 

Next steps - I believe I am going to adorn the windshield surround assembly with the electrical equipment that hangs off it - several boxes and a lamp.  I don't want to do that work after I paint on the blue, because there will be alot of handling and that paint is a bit fragile.  After that - then I will put the parts back into the jigs and skin the windshield surround, and then paint!  You will see the results next up.

 

Hope you like that aux jig - I sure do.  Later folks.        

   

 

 

  

   

Edited April 4 by JayW