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


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Posted (edited)
4 hours ago, Ayovan said:

I like the dope and tissue, but did you ever consider using silk instead of tissue.


Well, this ship has already sailed for the rudder.  However the elevators and ailerons and some of the outboard wing remain.  I will take that under consideration.


1 hour ago, Oldbaldguy said:

I see you’ve tried traditional tissue covering material.  That stuff is not the best for what you’re trying to do.  Plastic covering material such as Monokote or something similar is thin, easy to use and does not need much attention to look good under a coat of paint.  It comes in many colors and a roll of it is not that expensive.  I think the tissue you’re using is too heavy to work well in 1/18th.  Second point:  The “draped” look on control surfaces is a myth.  Simple truth is, the fabric skin on a control surface is flat just like aluminum.  Nobody much wants to hear that because a “draped” fabric covering “looks so realistic” and all.  But it doesn’t.  You may see that effect between the ribs on some fabric covered wings, but not on a properly covered control surface.  


The tissue I used is 0.001 inch thick.  Certainly not heavy.   Not familiar with monokote, but I will look into it.  As I stated above, the elevators, ailerons and outboard wings remain to be skinned with some sort of "fabric".   So I can try something else.  As far as a "draped" appearance, I have made a skeleton that closely follows the real thing.  I have the correct number of ribs, spaced correctly, and the contour of the rudder, although too thick (I had to keep the thickness unchanged so it matches the fuselage and fin) is close.  Both the full scale rudder and my rudder have compound curvature.  I believe that no matter how taut a fabric skin is, it is going to seek a flat contour if it can.  Only formers of some kind underneath it will force it to a curved contour.  And in between curved ribs where there is nothing to support the fabric, there will be some finite amount of "draping" although small.  Every picture in the Dana Bell #7 and #8 books where a rudder is shown, you can see some small amount of "draping".  I think my rudder will have a very representative amount of this, as long as the tissue remains taut. 


Since I posted earlier, I have applied several coats of Tamiya semi-gloss spray.  This appears to have smoothed out some of that roughness.  It's a little scary - each coat tended to slightly sag the tissue, but each time it sprang back taut as the paint dried.  Hopefully there is enough paint on there now so that the blue top coat will not do same.  I'll find out soon.


Next, I will be applying strips of decal paper to simulate the doubled up areas of fabric.  Wish I could pink the edges, but at this scale the pinked edges are just too small.   Look - each rib and the spars area covered with an extra layer of fabric.  I hope the decal strips will represent that convincingly:  




Also I have begun construction of the tab.  Thank you for the comments.  Will post soon. 

Edited by JayW
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All right - I have invested just over two weeks into the rudder project.  Every day there has been at least some activity, with some days consumed by it.  This doesn't include a week or so of Rhino modelling.  It seems longer.  It has been difficult and challenging right from the start.  Here are the finished parts prior to surface finishing:




You see a tab, made of plastic through and through (no fabric).  In real life it is aluminum.  You also see the tab control rod, a round tab mechanism access door, and the antenna mast.  Nothing magic - just carved and sanded plastic chunks.  Note also that plain white decal material has been used for doubled up fabric on the rudder itself.  The pattern fairly closely follows the drawing.


And here is the finished product - assembled, sealed painted, and weathered:






I am struggling with this.  I do not like to throw stuff away especially something that required alot of effort.  It's pretty rough around the edges.  Yet in some ways I am pleased with it.  Probably mostly because it obviously looks like a fabric covered control surface.  Yet, OBG reminds us that really well-done fabric covered control surfaces look almost as if covered in metal skin.  I just wonder if a wartime Corsair had control surfaces that pristine....  My replica is going to be just a mess from stem to stern - heavily weathered and tired just like it should be.  Already the forward fuselage shows this.  So I wonder if the rudder might just blend in.  This as opposed to a pristine model that looks factory fresh.  Were my model the latter, I would definitely not accept this effort....  


What would I do differently if I started over?  I could try to strip it and cover it with something other than tissue (silk, or monokote).  I think stripping it would not end well - that stuff is doped on there pretty good.  And the round door and opening for the tab control rod would be ruined.  I could make a new skeleton, and cover it with silk or monokote.  Or, I could do it over, redesigning it to accept thin plastic skin like Airscale did with the example he provided (no fabric).  I know this - I will not be doing the elevators the same way as the rudder - something different.


Two pressure packed weeks - alot.  Should I send it down the drain?  Yet this project is in its fourth year.  Accepting comments.  

Edited by JayW
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2 hours ago, Jim Barry said:

Is it possible to thin the trailing edge though? (If I have a good comparison here? ) 


Not now Jim.  Even if I had, it would have created mismatch with the rest of the model.  21st Century toys has pretty fat gages usually, with abrupt trailing edges.  Same with my flaps BTW.  Trailing edges too thick there too.  The elevators however, for some reason, have thinner leading edges.  Stay tuned.

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As I continue to wait for 3D print parts, my next task is the elevators.  Here is the toy part, along with the horizontal stabilizer (h/stab):




Both parts are dimensionally fairly accurate, and I will keep the h/stab and skin it in the near future.  The elevator is not bad as 21CT goes, but it has its problems similar to the rudder.  So I will scratch build the elevators similar to rudder, but with plastic skin instead of fabric.


A couple of interesting things about Corsair elevators - first, the left elevator and right elevator are identical parts (not opposite).  That is also true of the h/stab.  So items that are on top on the left side are on the bottom on the right side.  Pictures below show this.  Second, not only does the elevator have a trim tab, it also has a "balance tab".  Here:




Does anyone know of any other aircraft with balance tabs?




Notice the balance tab on the right has a horn fitting and a control rod which connects to an exterior fitting on the h/stab.  It is a kinematic parallelogram, so when the elevator rotates, the balance tab stays level.  The picture shows it clearly - the elevator is a few degrees down yet the balance tab is parallel with the h/stab plane.  That is why it mismatches with the adjacent trim tab, whose angle is controlled in the cockpit with the trim wheel.    Note also how one side is upside down from the other.


I don't know the reason for the balance tab, but I do know that it will counteract stick forces from the elevator itself.  Perhaps that is its function?  


Anyway, I have been at work creating the Rhino model:








I have not finished the trim tab yet, but the balance tab is in there.  


I intend to display this Corsair with the elevators about 10 or 15 deg down, so the balance tabs will at that angle to the elevators (e.g. level with the h/stab).   


Time to start making parts!!  Stay tuned.



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Awesome work as always, Jay!  The rudder looks legit... definitely looks like a fabric covered control surface.  If anything, all I might do, if possible, is to putty and smooth the edges of the rudder and leave the rest alone.

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35 minutes ago, Thunnus said:

Awesome work as always, Jay!  The rudder looks legit... definitely looks like a fabric covered control surface.  If anything, all I might do, if possible, is to putty and smooth the edges of the rudder and leave the rest alone.


Which is pretty much what I did couple days ago. Not putty, but CA and some 2-part epoxy to smooth out the edges.  So it might survive some sanding.  It looks alot better.  If however the elevators turn out stellar, I might do the rudder over again.  Thanks!    

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On Nov 1, 2022 I placed my latest 3D print order - tail gear bay parts.  Finally, yesterday, it arrived after running the Royal Mail gauntlet, and to a lesser extent the customs and USPS gauntlet.  Here's what I got:




I don't think I will describe every part.  But they are all important.  The big ones in back are the tail gear doors (two left, two right).  The littlest ones (and boy are they little) are rod end fittings for small pushrods and the like, for either the elevator push rod, elevator hinge shaft, rudder hinge shaft, tail gear mechanism linkage, and arrestor hook linkage. 


Some of these parts are exceedingly fragile.  I successfully Rhino modeled parts that are right at the limit of what 3D print can do WRT smallness or thinness.  Here is the most fragile of the bunch - the "scissors link":




What you ask?  It's this part:




That part is so thin and fragile that it nearly did not survive being cut from its sprues.  I ordered two of them just in case I ruined one, and yes I ruined one - broke a lug off.  Were I to do it over, I would beef it up - I became too enamored modeling to the drawing of the actual part and didn't have my 1/18 scale thinking at work.... 


The door has now re-opened for work in the tail gear bay at last.  I will have to try to re-remember just how I wanted to sequence things in there, as it is not obvious if I am to get it all in there properly.


Before that though, I really need to do those scratch built elevators before I forget the important little details.  The Rhino model is now complete (last you saw it, it was missing the trim tab, the round access hole and door, and the trim tab push rod penetration):




Some will notice the trailing edges look thick.  I mean to correct this as much as possible when the whittling begins.  Next post you are going to see parts and assemblies!  Stay tuned.

Edited by JayW
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It feels as if I am stuck in concrete, progress seems so slow.  But, I have put in alot of work the past week plus; just not alot to show for it.


In anticipation of fillet fairing work, I took a detour and added another aluminum skin panel and its opposite to the aft fuselage:




The upper one is the new one; the lower one I did a couple months ago.  It is missing an access door; it will be added after the fillet fairing work is done.  


The really hard work though is the elevators.  I have completed the "skeleton's"  for both LH and RH:




These assemblies were built up similar to the rudder skeleton, but are designed to accept thin plastic skins instead of the fabric I used on the rudder.  These two items are supposed to be identical, but tolerances come into play, and one tends to fit up to the LH side h/stab better, and the other fits the RH side a bit better.  So I have identified them as such.  I suppose they are not really "complete".  The leading edge ribs must be added, which is next.  


Next post will no doubt be completed elevators.  Hopefully with the tabs.  On the horizon is a return to the wheel well, and h/stab installation and skinning.  I am not sure which will happen first.  Both will prove adventurous!  Stay tuned.     

Edited by JayW
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