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Heavy Mod - 1/18 21st Century Toys P-47D Razorback


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'I must now somehow protect them'

Build a box around them.


'The layouts were hard'

An under statement.


'Must be very careful to duplicate everything exactly,'

I have found the making of duplicate, reverse, or obverse parts to be my most patient-lacking part of modeling.  Besides the precision, you're duplicating effort.  Who wants to do the same thing twice?  Wheel wells.  You gotta hate 'em.


Great show, Jay.  Lots of really good problem-solving.



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While doing the outboard ends of the gear bays, where the gear strut attaches, and where the strut side gear door hinges attach, it became clear to me that area of the airplane is a bit of an integration nightmare, with tight clearances between moving parts.  And if clearances are tight on the real thing, you know they will be tighter still on a scale model.  The main culprit is the "shrink link", a component that "shrinks" (actually compresses) the landing gear oleo as it retracts into the wing.  On Thunderbolts, a fully extended oleo doesn't fit into the hole!  Here is a sneak preview of this part:




Hmmmm - picture a bit fuzzy.  That's OK.  You see the link is temp installed with little plastic pins.  The silly little .06 by .06 by .08 box you see in the joint represents (poorly) a universal joint.  The scale is just too small to do it justice here (but not for a similar larger joint on the LG actuator (you will see that later).  And you can see the tube is being torqued a bit (it really needs to be a UV).  So I will remove the box and re-install it a bit tilted.   Both ends need it.  Anyway - that shrink link occupies the same space the gear door wants to be.  And I anticipate issues.  So, I will be re-shuffling the line up a bit and making the strut doors, to satisfy my burning curiosity.  Then if all goes OK, it will be on with continuation of the gear bay fixed components.  You will see that the station 64 rib is a monster - the beefiest rib in the bay (not including the strut box ribs you saw in a previous post) with the LG uplock and other stuff adorning it.


I have begun the layout work on the gear door, and I noticed my door wants to be considerably shorter than what is found on the engineering drawing.  Here is part of the drawing:




Why?  Well turns out that the model's wing is quite a bit thicker than it should be if scaled exactly.  This is common with models, especially big toys like this.  My landing gear strut length is actually pretty accurate compared to the real thing.  And it is mounted in the wing about right relative to the wings reference plane (a horizontal plane that runs down the middle of the wing).   But the lower wing skin is actually lower than the real thing by about .06 inch, compared to the wing's reference plane.  The upper skin is higher too.  Hence the thicker wing section.  Soooo, should my strut length reflect its relationship to the wing lower surface, or the wing reference plane?  If the wing lower surface, then I have to lengthen it by around .06 inch which I can do with some difficulty.    And that allows a properly sized strut door.  If I leave the strut length as is, then the door has to be short by at least .06 inch, so as not to jam its upper edge into the wing skin with gear extended.  It's almost noticeable.  I am inclined to just leave it alone - the overall airplane orientation resting on the gear will be more accurate that way.  I am open to suggestions.


Lively times.  Stay tuned. 

Edited by JayW
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43 minutes ago, Gazzas said:


   Again, you've done some great improvement to the model.  


In my mind there comes a point where you have to accept the thickness of the plastic, or learn to make the whole thing out of sheet aluminum.


Good luck, buddy!



I have thought this many times watching this build! Then you have to decide- where does it end?

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Ok - I decided to increase the length of the landing gear upper struts by 0.06 inch.  Doesn't sound like much, but it translates to over 1 inch full scale.  And it makes the landing gear doors look more right.  Since the last post, I fabricated the strut doors, largely from the drawing, but modified as required to account for the model's inaccuracies:






If the four support locations you see look kinked, or tilted, you would be correct. This door effort was 90% layout, 10% fabrication.  Making it was easy.  Here are the two swiveling links that attach the door to the landing gear strut - they were NOT easy at all due to their small size:  




Now, I have been on pins and needles wondering how this door is going to fit once installed.  I cannot understate the integration challenges with it and the "shrink link", and the structural box that supports the gear strut itself, and also supports the top of the door.  So I had to temp install the door in order to bond on the lug that provides the link attachment to the strut:




And with the lower strut and shrink link:




Everything fit!!!  Wow.  Cannot tell you how pleased I am.  Some things we do cannot be seen well; some can.  These doors stick out like sore thumbs and they have to be right.  Another shot of the exterior surface:




Alright - lots of detailing to be done, but this exercise has validated the approach I have taken with the landing gear.  What remains is to finish the brake lines on the gear strut, bond the lower strut to the upper strut (large milestone), and then I will do some more detailing (like paint), and set these components aside until final gear installation which is a long ways off.  Now, it is on to the LG actuator and the other wheel well components.  Thanks for tuning in.

Edited by JayW
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  • 2 weeks later...

Let me fill you in on what I have been doing lately - with the landing gear bay.  I get comments on how dis-satisfying gear bay work is.  Why is that?  To me it's a highlight.  Except what's coming up here.  What a drag (I mean the uplock fitting).


First, I finished up the detailing of the gear doors:




Fancy decals huh?  Great drawings from Republic - I just recreated them in PowerPoint format, copy/pasted into the decal program, and scaled. 


IT was then time to combine the landing gear lower forks to the upper struts.  Had to - in order to finish the brake lines.  To do this and assure the wheels would look straight (they could swivel), I sacrificed a long aluminum tube like this:




Much had to be temp assembled to do this.  You know the wings are a long way from being final installed to the fuselage!  And it is not time to final install the gear struts into the gear bay.  Anyway this worked well.   A finished landing gear strut now looks like this:




Then it was on to the gear actuators.  These were simply made of an assortment of plastic and aluminum tubes.  The hard part was creating the UV joints at either end of the actuator, which can kinda be seen in this picture:




Well, maybe not so much....  Anyway, it was a tight fit for a key item in the gear bay.  Here - this just proves I did both sides:




Right over the actuator is a pesky but essential component called the uplock box.  It's a piece of clockwork driven by a chain/cable drive, and timed by a hydraulic timing valve.  What an exercise in micro-surgery.  The real thing looks like this (from the Dottie Mae restoration):




The hook you see engages this part of the landing gear strut (circled in red):




I used to think that was a tie-down fitting.  Not so.  


And see that chain?  Remember the chain I made for the bubble canopy drive?   Well, I did it again.  Glad I had extra left over.  Here is the model:




A shot from the top (a luxury only available with the top half of the wing not there):




You can be forgiven if you do not see the chain.  The box and its associated details were a first class PITA.  I made it from plastic sheet laminations and some other very small adornments.  Once again, the layout work was tougher than the actual building.  And so also begins the tubing and wiring routing in the gear bay as you can see.  


Now what you also see in that last picture is the long station 64 rib.  It sort of divides the outboard bay from the inboard bay.  I have now finished the outboard bay on both wings, except for stringers which come soon (attached to upper wing half).    Next is the shear web that makes up the aft wall of the inboard bay.  Then more ribs (all partial), the all important inboard canted rib, and stringers.  Stay tuned!    



Edited by JayW
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  • 2 weeks later...

Last y'all saw was the outboard half of the LG bay pretty much done.  Now to update you on the inboard half, as much of it as I have finished anyway.


A P-47 wheel bay clearly shows, among other items,  alot of naked stringers on the wing upper skin, and a hydroformed web that is the aft close-out for the inboard half of the bay.  A good pic from Miss Dottie Mae:




You also see in there a canted and dished rib just above the gear door on the right edge of the picture.  So, since none of those parts exist on the toy, I was off to the races creating them.


The hydro-formed shear web was a little tough to do - I wanted to include the hydro-formed stiffening beads that surround the access door cutouts.  The drawing looks like this:




I considered several approaches, and settled on simply cutting rings out of .030 plastic sheet:




I added all the beads, and then filled in the corners with epoxy, and dirtied the parts up alot to hide imperfections (of which there are many):




This was a dirty airplane, operating off steel mesh airstrips in muddy French airfields in winter 1944-45, after all!  Note also the canted inboard rib, which I will not describe much except to say I could not figure out how to put the dished surface on it, so I didn't.  The real part is dished to provide clearance to the tire with gear up.


Now, the gear bay was closed out except upper surface, and stringers.  Stringers are beaded "T" section extrusions in real life, and there are 15 of them per bay.  Each is attached on its inboard end to the canted rib upper chord with a small fitting.  Drawings follow:




A closeup of the above drawing, showing inb'd attachment fittings:




And a typical attachment fitting:





For this effort, for the stringers I used 3/64 (0.047 ) inch angle shape, plus .01 x .04 strip for the missing skin flange.  And for the end fittings, just little (very little) pieces of plastic strip:






Ugly, I know.  But after paint and weathering it starts to look like it is supposed to:




Compare to the old wheel bay:




But I am not done!  There are still two sets of partial ribs (Stations 40 and 52) which are important for systems routing, and then the plumbing and wiring itself.  You will see that next post.  And that will be all I can do with the LG bays until the upper and lower halves of the wings are bonded together - sometime in the (distant?) future.  Thanks for tuning in!





Edited by JayW
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