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

[JayW]

On 3/25/2022 at 2:22 PM, brahman104 said:

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,....

Craig - I thought I had it all worked out in advance.  But that big fat mismatch with the s/c ducts is serious.  It translates to two or three inches in full scale.  in a compartment that is chalk full of things with tight clearances.  It is a harbinger of things to come.  I think the reason why is that the intercooler boxes that the ducts lie on top of were defined relative to the wing (they mount on wing leading edge ribs), and the rest of the engine accessories compartment is defined relative to the fuselage.  I apparently have made some scaling errors while duplicating the toy into the Rhino model.   Another disturbing thing I found is that the firewall doesn't match the Rhino model very well either.  

 

I tried doing another duct, but have found that it is going to interfere with the engine controls clap trap, or at least it appears to.  I am going to have to try to better understand the error, and see what needs to be redesigned and what doesn't.    

[JayW]

On 3/25/2022 at 4:31 PM, LSP_Kevin said:

It's just ridiculous how good this build is.

 

Coming from you Kevin, it means alot.  My challenge now is to keep it "ridiculously good" - troubles ahead in the engine compartment.

[jeroen_R90S]

I'm quietly following along enjoying each and every update. Such good stuff, I'd never thought the Corsair had all these odd quirks into it.

 

Kind of the difference between my old 1971 Hanomag camper (which was based on a 4,5ton truck chassis) which must have been designed, or aided by, people maintaining and repairing these things trucks. Hatches, room to move your hands, and some clever stuff was in there for ease of maintenance.

The Mercedesses had such odd features compared to that -remove the drive shafts from the rear axle to get the brake drums off or put te drain plug for the radiator riht above the chassis crossmembers -really?  

 

The Corsair seems to  fall into the old Mercedes trucks category!

I really enjoy looking at your work and am amazed by your abilities to replicate something from a 2D drawing into something that looks almost real in 3D.

 

Jeroen

[JayW]

6 hours ago, jeroen_R90S said:

or put te drain plug for the radiator riht above the chassis crossmembers -really?  

 

Oh I had a Fiat like that!

[airscale]

just mesmerising watching you do this Jay - every step is a lesson in mastering complexity and challenge

 

It seems the Corsair is a very complicated aeroplane and with opening it's kimono like that you have 3 models worth of model on your hands

 

Pretty much why I keep mine closed up now as I just can't take the work it involves or each one would take me years more than the years it already takes

 

Inspirational stuff

 

Peter

[KiwiZac]

That engine...just wow. Incredible.

[Rocat]

Wow mate! Stunning progress.

[chuck540z3]

So I'm looking at this incredible engine that came out of nowhere, not realizing that you made it from scratch starting on Page 2.  Triple Wow!  No wonder you knew so much about my Hellcat engine!

 

Ultra Impressed, 

Chuck

[JayW]

14 hours ago, chuck540z3 said:

So I'm looking at this incredible engine that came out of nowhere, not realizing that you made it from scratch starting on Page 2.  Triple Wow!  No wonder you knew so much about my Hellcat engine!

 

Hahaha Chuck!  I perhaps didn't fully think that out, posting a couple pics of the completed engine, done so long ago, and some followers had not seen it.  My first post on the engine was September 2, 2019.  Two and a half years ago.  And yes, in order to do that engine, I scoured the world for technical data so I could make it as accurate as possible.  I learned so much in the process.  As you are probably aware, the Hellcat and the Corsair share the same engine, or nearly the same - the Hellcat has its carb mounted on top; the Corsair's on the bottom - which means different aft section castings.  As far as accuracy goes - read on.  I am having crisis upon crisis in the engine accessory compartment, some due to inaccuracies with the engine aft section! 

 

On 3/30/2022 at 12:33 PM, airscale said:

It seems the Corsair is a very complicated aeroplane and with opening it's kimono like that you have 3 models worth of model on your hands

 

Hahahah Peter!  Kimono?  Kilt lifted maybe?   Yes you have the gist of it.  And I knew it when I made the decision.  I mean what do you do when you put your heart and soul into a sub-project (the R-2800)?  Do you cover it behind the cowl?  I think not. 

 

Let me give everyone an update.  When last I posted, I was a bit shocked by the mismatches found when dry fitting the supercharger ducting, and was anticipating problems to come.  I lost faith in my Rhino digital mock-up, yet knew I still had to use it.  I was right - it has been one surprise after another, almost all unpleasant.  

 

Beginning with a seemingly innocuous addition of the cowl flap actuator, which sits atop the engine aft section on the centerline.  Cowl flap actuator?

 

    

 

Many Corsair modelers have taken great pride in showing open cowl flaps, even with the circumferential cable that controls their position.  Well in real life the flaps are spring loaded open, each flap having its own coil spring on its hinge, and that cable must be pulled on to close them, almost like pulling down an umbrella.  That pull is provided by a small hydraulic actuator shown above.    

 

Here is mine:

 

 

The main component is some 0.078 inch diameter brass tube.  The rest is just bits of plastic stock as usual.  I mention engine accuracy above.  Initially that cowl flap actuator had its tail end tilted up more than you see in the pic.  It was supposed to be that way.  But I sensed trouble, so I Rhino modeled it and found a big clash with the hydraulic reservoir support bracket - this thing:

 

   

 

Looks like a playground set of monkey bars....  I have yet to make this thing (you will see it later on), and I am glad I found the clash now rather than later.  Another reason to make full use of my digital mockup.  Why the clash?  The only reason I can come up with is inaccuracy of the supercharger section of the engine, and/or inaccuracy of the engine mount.  I think the Rhino model is accurate in this case, if not in others.  Well, it had to be fixed, and breaking loose the actuator and reducing its "tilt" fixed it.  Whew.

 

Last post, I had completed the lower portion of the engine mount truss, anticipating access issues with other components, so not completing it.  Sequencing.  But I began to realize that, with the inaccuracies with both the Rhino model and the already completed engine, I needed to rethink this engine accessory compartment integration plan.

 

My new plan is sniff out potential problem areas (I am getting better at that, knowing now some of the inaccuracies), make up all the big stuff, no matter if it's on top or on bottom, and make sure it all integrates.  Then find a way with the smaller stuff where I might have more options should problems arise.  That meant, finish the engine mount truss, get the engine control clap trap installed, get the oil tank dry fitted, and figure out what to do with the mismatched supercharger ducting.

 

The engine mount truss - here is a nice shot from the Erection & Maintenance Manual:

 

     

 

Here is mine:

 

 

 

 

 

How did I make it - I used four tube diameters - .125, .100, .093, and .062.  I temp installed the engine/diaphragm onto the fuselage, taped it down tight.  Then I sized and trimmed each individual tube to fit.  Took a long time, but was classic scratch building and alot of fun.  I tried hard to accurately duplicate the aft end hard points.  As you can see, I made the mount very dirty - probably accurate.  The unpainted area is where the feared engine control clap trap goes.   This:

 

 

With the engine mounted completed, I set to work on the engine control supports, and the bellcranks, torque tubes, and push rods.  Parts were very very small.  Here is the lower idler support:

 

 

 

.8 mm brass tube, "welded" with tiny drops of CA.  Micro-surgery.  The long white plastic tube is greatly modified from the real thing - a redesign for a clash with the engine aft section.  Installed:

 

 

 

I had yet another unpleasant surprise installing this item - a minor clash between the long support tube, and the engine mount.  Consequently, the support is tilted a bit inward - hope it doesn't cascade into more problems...  There are two dark silver push rods that go from the yellow bellcranks to the carburetor - see them?  One is mixture control, one is throttle control.  Once this is all said and done, this installation will be almost invisible.  Almost, not entirely. 

 

This is really getting long.  Let me continue on a separate posting.  Coming right up.

 

 

 

 

 

 

Edited April 2, 2022 by JayW

[JayW]

Continuing, it is becoming more and more apparent that the very large oil tank poses integration challenges.  In the real aircraft, it is just STUFFED in there.  It is as large as the engineers could make it, and clearances are very tight to everything around it - the back of the engine, the cowl panels, the firewall, and notably - the engine control supports and linkage.  Another E & M manual pic of the engine control clap trap - the upper portion is going to be at risk for interference with the oil tank (and the supercharger ducting):

 

 

So I determined I had to make the mounting brackets for the oil tank, so that I can dry fit the tank itself as I proceed with making other stuff around it.

 

The oil tank supports are almost never seen on their own; here is another pic from the E & M manual:

 

   

 

There is a pair of top supports rivetted to the firewall, a pair of bottom supports with support rods going to little fittings on the spar, and a pair of straps.  Here are my support brackets:

 

 

Straps will come later.  I don't like that they are there at this stage of the build; they are fragile and are apt to be broken off.  But they just have to be there if I am to fit the oil tank.  Which will look like this:

 

 

The tank, if you recall, was Rhino modeled and 3D printed a while back.  It is a good thing I am going about it this way.  The process has uncovered still more surprises.  Do you see the protrusion on the tank down low on the centerline? Oil lines will emanate from it.  It clashes hard on the starter motor on the back of the engine!  I have remedied that by grinding the protrusion down to about 2/3 its original size, and I will crowd the oil lines later when i make them - hope it works....fortunately the details are going to be invisible.  That is not all.  The generator on the back of the engine clashes with the RH side lower oil tank support bracket.  I have removed the offending generator:

 

  

 

 

It is the protrusion that is the source of the clash.  I have not quite figured out the fix for this one.  Just rotating it might do it.  I have some reason to believe that generator is obsolete (used on the F4U-1, and not the -1A).  I will look into that and maybe kill two birds with one stone.  Either way, that generator (in which I worked very hard to produce) has to get replaced or modified or relocated in some manner.

 

Take a look at how this compartment is shaping up:

 

 

Getting crowded, and access to more stuff is clearly going to be an issue.  So much more to come.  My goodness.  Daunting and worrisome.  Everything is an uphill battle due to inaccuracies in a bay where clearances are so very tight. 

 

Next post should be the results of the upper engine control parts, and their integration with the oil tank and supercharger ducting (already requiring redesign due to the big mismatch described a couple of posts ago).   One way or another, this is going to get there!   Stick with me!

 

   

Edited April 2, 2022 by JayW

[Rocat]

Wow, amazing work

[JayW]

A short update for you.  Last post I mentioned that the generator had a clash with one of the oil tank brackets, and that the generator I built a couple years ago might not be effective on the -1A's.   I was right, so I made a new updated generator, which thankfully is shorter:

 

 

It is now attached to the engine; no more clash!  Next time you will see it is when the wire bundle is attached, and also the "blast tube".

 

Also I had expressed concern that the LH supercharger duct (the one on top of the intercooler box) might want to clash with the engine controls, once modified to address the big mismatch described a couple posts ago.  Additionally I was concerned about clearance between those engine controls and the oil tank.  To check, I built a crude mock-up of a modified version of the duct (a little taller, and angled) that I thought might work, and I finished up the engine control "clap-trap".  Tight, but looks like this is going to work.  Phew!  

 

 

This paved the way for me to order modified 3D print versions of the affected supercharger ducts, which address the big mismatch and which clear the engine control stuff.

 

In order to better study the other supercharger duct mismatch issues, I prepared and installed the 3D printed flattened ducts that attach to the main supercharger section of the engine:

 

      

 

Every part in the engine accessories compartment is going to be dirty, this included.  

 

A few pics of the aft section with the ducts and engine controls installed:

 

 

    

 

 

 

 

I now know that I can add spacers between ducts to address that other mismatch, so I do not need to redesign the ducts.  A PITA, but it's gonna be OK.

 

Next up will be the complex truss-style multi-purpose bracket on top of the engine mount, which supports the prop accumulator, the hydraulic reservoir tank, and a curious heater cutoff valve:

 

 

Modeled in the Rhino digital mock-up:

 

 

It is fairly large and takes up alot of space, so I will build it up and dry fit it as required as I continue populating the accessories compartment.  It may not be evident from the pictures, but the bracket is going to have to be tooled up with a mini-fixture of sorts.  You'll see that next post.  

 

Take care, thanks for looking in.

Edited April 10, 2022 by JayW

[brahman104]

You are a machine Jay!!!!!

 

Craig

[Rocat]

Wow. Amazing!

[JayW]

Thought I would report on a genuine success rather than problems.  Next on the list was the support bracket for the prop accumulator and hydraulic reservoir.  It is a truss works made up of welded tubes, in real life, and is a typical bracket in an engine compartment where attachments must be made to the engine mount tubes, for any aircraft, not just the Corsair.  

 

 

 

The assembly is front and center in the engine accessories compartment, in full view.  So I needed it to be the best i could make it.  No shortcuts.

 

To make this thing half-way accurate, I had to make a jig:

 

 

Really, it is a pair of .125 inch diameter tubes that locally simulate the top tubes of the engine mount truss, which are removable with long pins inserted into the aft end of each.  And most importantly a table of sorts in the middle, glued down on the base plate, which locates the prop accumulator, and the pan for the hydraulic reservoir.  I believe the jig is more complex than the airplane parts it is meant to help make!  The key here was for the simulated engine mount tube locations and orientation to be dead-on accurate.

 

Here it is in use as I build up the bracket assembly:

 

The partially completed bracket was extremely unstable and fragile at this point.  Until I got all the tubes in place and glued down.  Tube lengths were a long series of cut/fit/cut/fit/cut/fit.....

 

And, ta-daa!!  The finished bracket:

 

 

I don't want to repeat this - it was a stressful day building it up.  It is made of a long piece of 1/16 plastic rod, and lots and lots of pieces of .025 inch rod (some just tiny).  Also, .156 inch aluminum tube, split in half for the end clamps.  Once out of the jig, it is stronger than I thought.  Trusses really work, even when scaled down.

 

Painted, but not yet weathered:

 

 

If any of you know what color the prop accumulator should be, please advise me.  Without any further input, I am going to leave it gray.  

 

Dry installed: 

 

 

 

The Rhino digital mockup has been quite accurate for the upper region of the compartment, as opposed to the lower region where the wing parts (the intercooler rib) comes into play.  It's been a big help.  I am so so pleased that this came out all right.  

 

I think I am going to prepare and install the hydraulic accumulator, and put in as many hydraulic lines as I can associated with the reservoir, and also the air lines for the  accumulator.  Then I am probably going to start in on the electrical system and wiring.  I am going to do as much as I can to the engine mount / engine aft section combo on it's own before I finally must install it into the compartment.  Once that is done, access to anything deep in there will be nearly if not entirely impossible.

 

Stay tuned - more adventure to come.

 

 

 

 

Edited April 12, 2022 by JayW