1/18 Scale Blue Box F4U-1A Corsair Modification

[JayW]

21 hours ago, Hans said:

Jay, looking at your work I can't help thinking at times I am looking at a 1:1 Corsair. 

 

Hans - thank you.  That is the ultimate complement a modeler can receive.  Now for me to continue to live up to it.  Perilous times ahead.   

[Citadelgrad]

2 hours ago, JayW said:

 

Hans - thank you.  That is the ultimate complement a modeler can receive.  Now for me to continue to live up to it.  Perilous times ahead.   

No worries from the peanut gallery. Your slow, thoughtful approach is yielding excellent results.  Slow and steady.  

[JayW]

In parallel with actual physical modeling work, I am trying to keep the pipeline active for 3D print parts.  They have a fairly long lead time, and I don't want to be caught having to wait for parts.  But also, my orders have to be large enough to warrant the overseas postage.  So sometimes i order parts I don't need immediately.  Now is such a time.

 

One of the first posts I made on this build a few years ago described how I turned the nose cowl on my lathe to decrease its diameter a bit.   

 

 

Now though, I can do much better with a 3D printed part.  Thought I'd show you the Rhino model as a preview to the real part:

 

  

 

 

Some construction geometry:

 

 

That is going to look alot better than my plan A.  The internal ribs will also be 3D printed separate from the cowling itself.  They attach to lugs on top of the engine cylinders, so I need adjustment to locate all those ribs right.

 

I have also worked on the propeller and hub.  Here is what came with the toy:

 

  

 

Nice prop, actually.  But this is a "combat prop", not effective on earlier F4U's.  Take a look at what Dana Bell has to say:

 

 

So I need the thinner prop on the left.

 

Doing a prop in Rhino is really a challenge.  The way to do it is to draw prop blade cross sections in many places along the length of the blade, rotate them to account for twist, and then create a surface through all the cross sections.   Where do I get the cross sections and twist angles, and other prop blade data?  From Aircorps Library, which have lots of manuals on propellers, including Hamilton Standard.  Including the "6443A-21" prop blade. 

 

Here is the construction geometry I created in Rhino using that data:

 

  

 

And with alot of persuading, I get a prop blade.  Do a polar array with three parts, add a hub and I get this:

 

 

That will be much more representative.  

 

The hub was fun.  There is also maintenance and overhaul data for Hamilton Standard hubs of all kinds.  And I used it to create Rhino models with alot more accurate detail than what the toy provided:

 

 

 

 

I'll be ordering these parts (cowling, ribs, prop hub, three blades) along with some engine accessory compartment parts in the next day or so. 

 

Now, back to the real work.  I will post progress soon.  As always, thanks so much for looking in. 

[JayW]

A bit of real work progress instead of solid modeling in Rhino, as I wait for 3D print parts in the mail - 

 

Remember the belly door?  Here, from a few weeks ago:

 

 

Now that most of the belly skinning is done, it can be installed.  It's position is controlled by a hydraulic actuator mounted on the center section spar.  The tough part was bonding the door to the fuselage (it didn't fit that well).  The actuator was easier, although the hydraulic hoses were pesky as usual:

 

 

 

 

And....just like that I have cleared the way to the very challenging engine accessories compartment project.  No more dawdling, delaying, looking for other things to do.

 

First is to start building the engine mount truss, you know, this:

 

 

 

The ring in front has been around for a couple years now - it is part of my diaphragm.  The first of many tubes has been done (lower LH main tube), with the attach fitting on the aft end:

 

 

I think I may have to build this up a little at a time, and mount stuff on it as I go.  We'll see.  Take a look at this nightmare:

 

 

That array of ugly contraptions is the support structure and the bell cranks, idlers, and control rods for the engine controls.  Yikes!!!  All mounted on - you guessed it - the engine mount truss.  How on earth am I going to do that?    

 

I am going to give it a go, either now, or after I get the carb air intake duct in there on the bottom of the compartment.  In the next couple of posts you should see something on both.   

 

Take care!

 

[Oldbaldguy]

Dang.  It’s always somethin’.

[brahman104]

Can't wait to see the magic continue Jay! After everything you've done so far, can you really class this as a challenge?   Just kidding, that's a very complex looking part and I can only assume there's going to be some very create jigs made up to align everything!

 

Craig

[Oldbaldguy]

On 3/17/2022 at 5:46 PM, JayW said:

A bit of real work progress instead of solid modeling in Rhino, as I wait for 3D print parts in the mail - 

 

Remember the belly door?  Here, from a few weeks ago:

 

 

Now that most of the belly skinning is done, it can be installed.  It's position is controlled by a hydraulic actuator mounted on the center section spar.  The tough part was bonding the door to the fuselage (it didn't fit that well).  The actuator was easier, although the hydraulic hoses were pesky as usual:

 

 

 

 

And....just like that I have cleared the way to the very challenging engine accessories compartment project.  No more dawdling, delaying, looking for other things to do.

 

First is to start building the engine mount truss, you know, this:

 

 

 

The ring in front has been around for a couple years now - it is part of my diaphragm.  The first of many tubes has been done (lower LH main tube), with the attach fitting on the aft end:

 

 

I think I may have to build this up a little at a time, and mount stuff on it as I go.  We'll see.  Take a look at this nightmare:

 

 

That array of ugly contraptions is the support structure and the bell cranks, idlers, and control rods for the engine controls.  Yikes!!!  All mounted on - you guessed it - the engine mount truss.  How on earth am I going to do that?    

 

I am going to give it a go, either now, or after I get the carb air intake duct in there on the bottom of the compartment.  In the next couple of posts you should see something on both.   

 

Take care!

 

What are we looking at here?  I don’t think this is a motor mounted on a firewall -  you can see boxes and other stuff through the lightening holes at the bottom.  This could be a jig where they built up the motor and mount at the factory before hanging the whole thing on the airframe or it could be an engine test stand.   I’d do some cross reference on all those bellcranks and such before committing to glue and plastic just to be sure that’s how all that stuff works/looks on the real deal.  Besides you still need to know how and where all those pushrods penetrate the firewall and you get none of that in this photo.

 

[JayW]

21 hours ago, Oldbaldguy said:

What are we looking at here?  I don’t think this is a motor mounted on a firewall -  you can see boxes and other stuff through the lightening holes at the bottom.  This could be a jig where they built up the motor and mount at the factory before hanging the whole thing on the airframe or it could be an engine test stand.   I’d do some cross reference on all those bellcranks and such before committing to glue and plastic just to be sure that’s how all that stuff works/looks on the real deal.  Besides you still need to know how and where all those pushrods penetrate the firewall and you get none of that in this photo.

 

Good eye.  What you are looking at is a quick-change unit.  I don't think Bu Air followed through, but the intent was to have a unit that easily mounts to the fuselage, where as much as possible is already attached to the engine or mount truss.  That includes the engine control clap trap.

 

As for the engine control clap trap you see in the picture - that really goes on the airplane.  I have a drawing that defines all that stuff (drawing 10301 - Engine Controls).  The firewall has a complicated little block with many little holes in it for bicycle brake style cables and housings to penetrate.  The cables run from the engine control quadrant in the cockpit to the that rube-goldberg looking contraption.  When I get to it, I will learn more of the details.  Tell the truth, it isn't going to be much fun....    

[Oldbaldguy]

28 minutes ago, JayW said:

 

Good eye.  What you are looking at is a quick-change unit.  I don't think Bu Air followed through, but the intent was to have a unit that easily mounts to the fuselage, where as much as possible is already attached to the engine or mount truss.  That includes the engine control clap trap.

 

As for the engine control clap trap you see in the picture - that really goes on the airplane.  I have a drawing that defines all that stuff (drawing 10301 - Engine Controls).  The firewall has a complicated little block with many little holes in it for bicycle brake style cables and housings to penetrate.  The cables run from the engine control quadrant in the cockpit to the that rube-goldberg looking contraption.  When I get to it, I will learn more of the details.  Tell the truth, it isn't going to be much fun....    

Wow.  Vought engineering strikes again.  It’s like the designers were being paid by the parts count.  Thanks for clearing that up.

[JayW]

OK - alot to go over.  First, let me present to you the last two pictures you will see of the completed R-2800, because from now on, the engine is separated into a forward section and an aft section:

 

 

 

Some of you thought way back when I finally completed it, that I ought to not install it and just display it on its own.  Well it was on display in my office on its own for a couple of years or so.  But no longer.  Nope - it's going into the Corsair.

 

Work has now begun in earnest on the engine accessories compartment, and it is one adventure after another.  My plan is to do this compartment in layers starting on the bottom.  I may vary from this plan from time to time if it seems to make sense. 

 

On the bottom is the carb air intake duct and the carb air box.  These parts were 3D printed.  Here is the air duct, where I have added some stiffeners and a piano-hinged door and some itty-bitty linkage parts:

 

   

 

Here is one of the real ones, leaning on the big fixture:

 

 

You can see my part is pretty simplified.....but it will not be very visible.

 

Here I have installed it, along with a typical Vought rube-goldberg contraption for operating that hinged door:

 

 

That door and linkage is part of a system called "alternate air - engine".  It was on early Corsairs, and deleted later on.  Your guess is as good as mine what it is for, and why it was deleted, and when for that matter.  The drawings and manuals are not clear on any of that.  If you know- please enlighten us all!    The door, when pulled open, allows air in the duct, traveling from the wing leading edge air intakes to the carburetor, to escape into the compartment, and presumably out the belly door.  I don't know why - but I could guess that it can change the percentage of air flow to the superchargers relative to the carb, or perhaps between one stage of the supercharger to the other.  

 

Next was to install the aft section of the engine to the diaphragm, and get started on the engine mount truss - the bottom of it anyway:

 

First the diaphragm:

 

 

This might be the singularly ugliest part I have made for this model so far.  But fear not!  In the end with the engine installed along with the exhaust stacks, the cowl flaps and shoulders, and the supercharger ducting, it will be all but invisible.  It was made a long time ago, out of lathe-turned acrylic and simple plastic sheet, and incorporates the engine mount ring.  It may look ugly, but it is engineered to the max, and allows accurate installation of not only the engine aft section, but the front section.  An extremely important part to get right.

 

And bonding the engine aft section to the diaphragm, and beginning the engine mount truss:  

 

 

A BIG DEAL that last picture!  Before I did that though, I accidentally fumbled the engine aft section and it fell to the floor.  A couple of years of NOT dropping the engine, and now I drop it?  At which point it separated on one of the bond planes, and sent several pieces (including the generator) scattering in all directions.  After recovering from temporary heart stoppage, and after the quivering and shaking of the hands that must do the repair work subsided, I hunted down the scattered parts and went to work repairing.  The assembly now is no worse for wear, really.  And I am so fortunate it wasn't anything worse.

 

Above you can see the carb airbox there in between the "rabbit ears" on the diaphragm.  Enjoy it - that is the last you will ever see of it.  For when the engine aft section and diaphragm are installed into the fuselage, that part disappears from view entirely!  It was a waste digitally creating it, getting it printed, and then painting it and installing it....  That can also be said, I'm afraid, of the carburetor unfortunately.  The carburetor that I spent many many hours on (days really), and am so proud of.  It breaks my heart.

 

Another pic:

 

 

Lots and lots of tight clearances, some too tight.  The tachometer generator is too close to one of those tubes; not sure how to address, but I will at some point.

 

Here is the major subassembly temp installed:

 

  

 

So as you can see here, I am off and running on this very complex and crowded compartment.  

 

Now that the engine aft section is installed on the diaphragm, I was able to do some checks WRT the supercharger ducting.  Here are the 3D printed parts I received some weeks ago (save one elbow that was missing, and being mailed separately):

 

   

  

 

They are fresh off their sprues, and are of course not fully prepared. 

 

The Rhino 3D mock-up I have been using is approximated.  Because it must depict the actual toy model I have to work with (which I measure as best I can and duplicate features digitally), as well as new parts I create.  So I knew the ducting was not going to fit perfectly; I was hoping it would be close....

 

First check was these ducts:

 

  

 

Using some double backed tape to dry install, I get this:

 

 

Whaaaa?????   Wow.  The mismatch is about .15 inch or so.  How did that happen?  See what I mean about the approximations made to create the Rhino model?  Big digital modeling error or more likely a big error in measuring the existing toy - it concerns me...what other surprises are in store.  So what to do.   I think at this point I am going to create another 3D print duct and its opposite - the one that sits on top of the intercooler box - modified to account for that vertical mismatch.  And/or modify the elbow to put a downward dip in it.  It's only time, and money.  But I need to do it soon, as the 3D print parts have a several week lead time.  That ducting will not be installed for a good while though.  

 

Next check was these ducts:

 

 

That run has three parts - an elbow coming out of the wing leading edge, a middle section that elbows up at its forward end, and the prominent flattened top section that leads to the supercharger housing. 

 

Here is the check: 

 

 

It doesn't look too good either.  However, I think I can salvage the parts with spacers and some trial and error. 

 

Last post I was lamenting the engine control clap trap.  This stuff:

 

 

I decided (wisely it turns out) to add it to the digital mock-up in Rhino, using the engineering drawings that define the parts.  I am mostly through it, and have found one clash after another.  Good grief - am I glad I am finding this on the computer instead of later on the bench!  Why is this happening you ask?  Well the engine aft section itself involved some guesswork, the compartment has out of scale thick walls that causes design adjustments to be made to the engine mount and other components, and some of the engine control parts are so small that to scale them perfectly is impossible.

 

The modeling is almost done:

 

   

 

 

Many parts are receiving modified designs to address all the surprises.  The changes will be unnoticeable though.  The push/pull rods are not in there yet BTW.  I think Oldbaldguy asked about the firewall penetration - there you see it.  

 

Next post I believe you will see more of the engine mount truss, and the engine control clap trap.  Microscopic work to be sure.  At that point I will be in a position to decide what goes in there next.  I  must be ever careful not to mis-sequence something.  I want to include everything I can.  I will also show you the design changes to those mis-matched supercharger ducts.

 

Adventures await!  Til next post - thanks for looking in!  

 

 

Edited March 26, 2022 by JayW

[dodgem37]

Jaybo, you is killin’ it!

 

Sincerely,

Mark

[brahman104]

Oh man Jay I think your build has got to be the most complex one around by miles! There is so much going on here it's hard to even fathom how you managed to work it all out in advance! I definitely see the digital mockup value, and I'm sure you'll come up with an ingenious fix on the ducting soon enough. I can't imagine how much the kit's wall thickness and "real world" problems have impacted here despite your best efforts, but you certainly find ways to overcome them!

 

Loving your work as always Sir!

 

Craig

[LSP_Kevin]

It's just ridiculous how good this build is.

 

Kev

[Jim Barry]

I keep thinking your project photos here are reference photos! Lines are getting blurred! Outstanding!

[Pete Fleischmann]

Crazy good.

 

love it!

 

cheers

P