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


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Jay, first off, have to say your work is fantastic!

Searching Tommy Thomasons site shows the Kepford photo with the following info: “Another alternative that eliminated the forward antenna mast was to originate the antenna on the tip of the right horizontal stabilizer. It is shown here on Ira Kepford's F4U-1A but it was typical on the F4U-2 night fighter. (Also note that this VF-17 F4U does not have the mast aft of the cockpit; it does, however, have a whip antenna in that location that is presumably for a VHF radio.)” as you’ve probably found. 

I’m thinking (and it is purely a SWAG on my part) that the “whip antenna” could be the internal rod that the wooden mast mounts onto. Not sure if there is a drawing detailing the mast mount. I’ve seen a lot of the masts but don’t recall ever seeing the actual mount assembly for it. I’m not sure what type of wood the masts were made from, but given the speeds and locations (vibration and flutter), it would seem they would require a secure mount. Again, purely conjecture on my part.


Addition: I can’t post pics but one photo from the linked sale listing shows the mast base and would appear to show a mounting hole in the base connector that would slide over the rod for mounting.



Edited by Tec182
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2 hours ago, Oldbaldguy said:

Cool.  Glad we got that sorted out.  It’s amazing how much and how quickly our technology advanced during WW2.


Ah, well remaining to get sorted out is just what that whip antenna looked like, and also just how the aerial cables or wires were rigged on this aircraft.  That rigging might be the last thing I do in this build - should I live so long!


3 hours ago, Tec182 said:

Not sure if there is a drawing detailing the mast mount. I’ve seen a lot of the masts but don’t recall ever seeing the actual mount assembly for it.


Oh yes - drawings galore.  The mast/antenna itself is an "AN" government standard with its own spec drawing, outlining basic requirements and interfaces.  And then whoever contracts to supply this to the government has its own in-house drawing(s) used to manufacture the item, and defines all the nitty gritty details.  The mount itself is the responsibility of the airframe manufacturer, in this case Vought-Sikorsky.  Here is the Vought drawing for the aft mast mount:




Close examination of the drawing shows that mounting brackets are attached to an adjacent fuselage bulkhead (Station 218 bulkhead), which is actually the aft face of the radio compartment.  What is not shown on this drawing is a penetration hole in the bulkhead for the cable to pass through - that cable attaching to the bottom of the mast, and then some equipment in the radio compartment on the other side of the bulkhead.  This support installation is typical of any aircraft that has this mast.  In all cases I have seen, the mast is located directly adjacent to a fuselage frame, which provides a good stiff and strong hard point for a couple of mounting brackets.  Note also that the fuselage skin is not relied upon to provide structural support.  The skin cutout is larger than the mast cross section, and then a closer fitting "cap" is fitted over the hole, and rivetted to the skin itself.  Lastly, note that the mast is offset from the aircraft centerline, in this case to stay clear of a centerline longitudinal longeron.  That is also commonplace - the P-47 (bubbletop) mast is also offset an inch or so; not sure about the razorback.


3 hours ago, Tec182 said:

Another alternative that eliminated the forward antenna mast was to originate the antenna on the tip of the right horizontal stabilizer.....


 From what I have read, there are many versions of aerial wire antenna rigging for the Corsair.  In time, I will be studying it closely.  But not today!   

Edited by JayW
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20 hours ago, Oldbaldguy said:

While I certainly don’t know for certain if this applies here, it would be about this time that the FM radio came into its own in the US military.

OBG - I think you are correct.  FM (frequency modulated) radio signals are indeed in the VHF band of radio waves.  The timing seems to correspond to the appearance of these AN-104 antenna masts.

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22 hours ago, Tec182 said:

Addition: I can’t post pics but one photo from the linked sale listing shows the mast base and would appear to show a mounting hole in the base connector that would slide over the rod for mounting.



I took a couple of screen shots of pics in that link.  Not to beat a dead horse, but Tec182 - this is a great find!  I mean this antenna mast isn't even restored.  It appears to be new out of the box!  If you are referring to this pic....




....that is not a mounting point at all, but merely the jack for attaching the cable, or in this case a 90 deg elbow and then the cable.  The next shot in that collection shows the elbow:




As described in my earlier post, there are brackets that grip the lower (unpainted) portion of the mast that serve as the mounting points. 


Thanks for the ultra-cool link. 

Edited by JayW
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Just to let you know I have not completely ceased work, I will show you a bit of progress.  A bit only, because in order to complete the tail wheel bay, a bunch of 3D printed parts are required, and I don't have them yet.  They are however in the mail (from UK), and I expect to have them within a couple of weeks.  


Meanwhile, I have been doing all I think I can with the aft fuselage in the 3D print parts' absence.  One area is the radio compartment behind the pilot seat and armor.  I am not at all sure that any of it will actually be visible, but the armor plate does not completely cover the compartment, so a bit of it may (wonder if the Tamiya kit has a radio compartment....).  Here:




This is not a max effort by any means since at least 90% of it will be unseen.  And, it is a fiction.  These radio units are nothing but a SWAG.  As was discussed over the last few posts, VF-17 aircraft got VHF radios and antenna's even though they didn't show up on the production line until later.  So changes were incorporated in the field.  I found a radio compartment drawing that shows VHF stuff, so I sort of made boxes that look like what I see on that drawing.  That shelf you see, is there for more radio equipment, but that drawing didn't show anything on it.  So there you go.  Electrical cables are just white painted solder - I think some of that might be seen if you know where to look.  In back is the Sta 218 bulkhead which the floor attaches to.  It will not be seen at all, but the floor has to attach to something. 


Here is the aft fuselage at its current stage of completion (held for parts):




Next post I hope to show those new 3D print parts.  Should be fun!

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  • 2 weeks later...

Just a small update while I still await 3D print parts from UK, which has been suffering a postal strike.  :BANGHEAD2:


In the mean time, I am turning to control surfaces (rudder, elevators).  I hope to show something soon - hopefully convincing looking for fabric covered assemblies.  


Some may recall that I had 3D printed two kinds of tail wheel tires - one with fine tread slots and one with a coarse tread slots.  Both are shown below.  The coarse tread tire came out better (a better bulge at the flat), but I think the sentiment both with my viewers and myself was to prefer the fine tread version if the bulge could be improved.  So I got out the putty and did a bit of improving on the part and it came out pretty good.  Take a look at the tire/wheel/yoke combination so far:







I think I made the right choice....Man, 3D print is just magical.  BTW, do you think it is dirty enough?  Just a heavy dose of Tamiya Weatherine "oil stain" and some "mud and "light sand" on the tire.  Am accepting suggestions from anyone who thinks the weathering ought to be different.


As soon as those 3D print parts come in, I can get to work on the linkage that supports that assembly, and button up the aft fuselage.  Sooo frustrating having to wait, but I am busy enough with other things.


Merry Christmas to all my fellow LSP'ers!  


Edited by JayW
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On 5/3/2022 at 11:59 AM, Oldbaldguy said:

Not that I’m trying to get in your business, but one wonders if you are going to build up the control surfaces from card stock and then cover them with tape or something like you did with the fabric panels in the gear bays.  After all this work, I can’t imagine slapping heavy plastic ones on it and have it look right.


OBG comment from nearly eight months ago.  So this post is for you.


As I continue to wait on important 3D print parts for the tail gear bay, the package now hopelessly stuck in the Royal Mail quagmire for god knows how long (I cannot tell you how frustrated I am over that), I am looking for things to do instead of the tail gear bay which is finished as much as it can w/o those parts.  For those of you unaware, the Royal Mail is in the middle of a protracted strike which apparently has sent an awful lot of mail into a black hole for an undetermined amount of time.  Grrrr! 


Turns out there is plenty to do in the mean time.  I have turned to the tail feathers, first the rudder.  An early picture of the fin/rudder, taken at the beginning of this build years ago:




And a later one with rudder removed:




This part is typical for a 21st Century Toy effort to provide a fabric covered surface.  Pretty sad but hey - it's a toy.  It is going to get entirely replaced, except the leading edge portion that I have sawed away (taped in place).  Funny, I didn't even notice until I began work on the rudder that the real one does not encompass the vertical tail upper leading edge.  In fact it stops short of it:




instead the fixed fin extends its leading edge into that zone.  So that sawed off portion will have to be added to the fin, like this:




I will retain the fin and its new top extension, and skin it in aluminum.  After the fuselage halves are joined of course.  Trying not to lose sleep over it.....


For the rudder, I am going to attempt to do an "Airscale" style scratch build where you start off with a "spine" and add elements to it like spar and ribs, etc.  Then I either fill with bondo (in this case P-38), or use a tape of some kind to simulate the fabric.  I have made a Rhino model to minimize surprises:





Alot to that digital model; has taken some time to develop.  Here are the important components of the rudder:


1.  Main rudder box including spar, rib elements, and fabric skin

2.  Balance weight tower including short false spar, ribs and P-38 filler (this is the upper portion of the rudder, forward of the hinge)

3.  Rudder leading edge @ hinge including circular section formed plastic skin, ribs, and hinge provisions

4.  Tab including tab spar, ribs, skins, and "horn" attachment for tab control pushrod


My progress so far:




That shows the main spar, the beginnings of the balance weight tower, and the main rudder spine.  Also the first of quite a few main rudder ribs.  Nothing on the tab yet, nor the hinge area leading edge (circular section).


Here are the ribs and spine that will give the balance weight tower its shape (already glued down and attached to the main spar):




Edges painted black for when sanding the P-38 comes.  Materials are just plastic sheet stock (.02 thickness) mostly.  


Here is the aft spine after prep:




Peter uses brass sheet generally for his empennage components; I am going to try to make do with .02 plastic sheet.  Note the bare areas for rib attach, and a notch cut out on top - for the aerial antenna mast.  And of course the cut away portion for the tab.


Once my "skeleton" is done, I will use these products to finish it up:




P-38 multi-purpose filler, on the recommendation of Peter (Airscale) Castle, and aluminum adhesive backed tape on the recommendation of myself.  The P-38 filler is for the balance weight tower.  I already tried it out on a simple test part - it should be fine.  I am worried about the tape though, which will cover the remainder of the rudder except tab.  It has very little if any flex to it so it will want to wrinkle a bit wrapping around a compound curvature rudder body.  Also, it will not have a whole lot of surface to adhere to - just edges of ribs, and a built up periphery.  Man - I am counting on this stuff to work.  I also have clear packaging tape which has great stick....  I would love some comments and ideas on this.  My hope, of course, is the tape will give a draping effect that makes the rudder look fabric covered (which it is in real life).  Bare Metal Foil offers several foils which purportedly have some flex, which might be a better option.  Anybody have any experience with that? 


This rudder work, including the Rhino model, is time consuming and labor intensive.  The elevators will be a very similar large effort (except times two!), coming soon, as will the ailerons later on in the build.  Perhaps the interminable RM delay can be withstood.


OBG - I mean to make you happy on this.  Stay tuned.



Edited by JayW
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This looks exciting Jay! My limited experience with Aluminium tape is when I used it recently on the nose cone. I've also done some experiments with using it to cover the cowls as they are one big nightmare of compound curves as well. 


Suffice to say the tape definitely has potential. By virtue of "peeling" it off the reel it tends to develop little wrinkles all by itself, but it does hold up to liberal applications of steel wool and a little bit of sanding. Depending on the width of any strips you make of it, you may want to wick some super glue along the sides once it's in position. The adhesive is okay, but does tend to go a bit tacky after some heavy shaping and smoothing. I think it has definite potential for what you're trying to do here Jay and I know you have the skills to see it through :) 


Good luck with it, can't wait to see the result! 



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