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

[JayW]

Hi folks - hope your Thanksgiving was terrific.  Mine was. 

 

Last August, I got started on the flap support ribs, and then thought better of it and delayed any progress.  I left it like this:

 

 

Now after four months of all the other wing stuff,  alot of which was heavy lifting where you don't want fragile stuff exposed to damage, it is time to return to the flap supports and linkage.  I have really been looking forward to it.  

 

What you see above are two flap support locations - the outboard and the mid.  So I set out to make an inboard support, which is so far inboard it practically falls off the wing:

 

 

 

I know, it looks awful.  But it's going to be fine later.  It actually sits underneath the wing-to-fuselage fillet fairing, and in real life occupies the inboard end of "spar 3".  I had to create a spar 3 segment for it, and it was messy.

 

In parallel with the trailing edge rib work, I started on the flap linkage.  I have determined that the linkage needs to be installed prior to gluing together the wing halves. 

 

Recall the flap linkage looks like this:

 

 

 

 

That view on the left is a little confusing because it shows the 3-piece support linkage and the 2-piece drive linkage as if they are in the same plane, when really they are several inches apart.  That can be seen in the plan view on the right.

 

The forward link (89C22305) looks like this:

 

 

My forward link looks like this:

 

 

The resemblance is fleeting at best, but the link is nearly buried inside the wing with flaps out (and of course completely buried with flaps stowed).  Anyway that's all six.

 

The aft link (89C22306) looks like this:

 

 

My aft link looks like this:

 

 

The resemblance is much better, and this link is fully visible with flaps out.  Here is the assembly line for the aft links:

 

 

Basically two side plates, a center web, and a lug, all made from simple plastic stock.

 

And lastly the third translating link - I will call it the boomerang link - (89C22307) looks like this:

 

 

Mine looks like this:

 

 

This one, of the three, is the biggest pain because of the stiffening flanges, which are small slivers of plastic strip, trimmed to shape.  I have a good bit of micro-surgery to get all six, as you can see.

 

Assembled together they look like this:

 

 

 

And attached between rib pairs on the wing:

 

 

The geometry of these links differs some from true scaled parts - I had to do this to deal with the inaccuracies of the toy wing.   Anyway, pretty rough looking right now, but I promise it's going to look awesome once I am finished with it.

 

BTW, here are some flap support linkages on Dottie Mae:

 

  

 

Next post I hope to be done with all six flap supports, including support rib pairs, support linkage, and the drive linkage in two places per flap.  Til then!

 

Edited November 28, 2018 by JayW

[Trak-Tor]

 

 

Juraj

[dodgem37]

Complicated shape.

 

Great!  I love articulating details.

 

Sincerely,

Mark

[JayW]

"Complicated shape."  says Mark (dodgem37).

 

yeah - I thought about reproducing it, but it would have been a big PITA for a link that is largely unseen.  Note also the severely slanted clevis slot - the shot of the stowed linkage shows clearly why that clearance is needed. 

 

So linkage mechanisms are right in my wheel house - that is what I did before I retired.  Thinking on it a little (why it is the way it is in real life), this link is mostly a two-force member meaning that it is intended to only take tension or compression inline loads.  There is no significant in-line bending (like the boomerang link sees).  MOF, the primary load is tension - as the flap provides lift, the forward link reacts it with a tension load.  The only compression load it sees is from the dead weight of the flap, times some inertia factor - a much smaller load than the load resulting from flap airloads.  That said - its cross-section (a cross or "+", as opposed to an "I" or an "H") is ill suited for compression loads.  It would buckle under a significant compression load.  The aft link (which does see a significant compression load) has a nice stable "H" section for that purpose.   But the forward link has a nice efficient section for tension load.

 

But that's not all.  To be a true 2-force member, the end joints must be spherical bearings.  But they are not.  They are "journal" joints meaning they can take side load (sphericals cannot).  Why?  Well something has to hold the flap in position spanwise.  If all the joints were sphericals, it would wiggle to and fro in a spanwise direction!  To do that at least one attach joint must be a journal, on both the forward and the aft link.  Side loads however will be small.  Airloads go fore and aft with almost no side component.  The only side load of any significance at all would be getting bumped or pushed by something on the ground (these are typically called "abuse" loads, and are a factor of the weight of the flap - 6x or something like that).   Even with the factor the load is small in comparison with the air load.

 

 

Edited November 28, 2018 by JayW

[Shawn M]

excellent engineering summary 

[richdlc]

[JayW]

The RH wing flap linkage is done, and it wasn't easy.  Here:

 

 

Some things to note - You see three supports, each with a pair of fixed ribs, and a linkage in between the ribs, just like the real thing.  Most exposed are the "boomerang" links, sticking out inviting damage.  That is also just like the real thing.  So far no damage, but I live in fear of breaking one, and/or what it attaches to.  Repair would probably be very involved.  Each linkage is movable to a certain degree.  That way I can better attach the flap when it comes time, and get it to the flaps-down position I want.  You also see an unpainted torque tube between the inboard and mid supports, just like the real thing.  Look closely and you will see the actuation arms on either end of the torque tube, directly adjacent to the main supports.  The ends of these two actuation arms attach to fittings growing out the nose of the flap.  At this point the arms can rotate, independent of each other (NOT like the real thing), again to better attach the flap in the correct position.  The torque tube is actually two halves, with a crude torque tube support at the tube's mid span.  This allows me to get that independent rotation.  Once the flap is positioned later on, I will drop in some liquid glue on all the linkage joints to firmly fix the flap in its flaps-down position.  

 

With both wing halves, the supports look like this:

 

  

 

Hopefully, this scale aircraft will have robustly mounted flaps in the down position, when it is all said and done - during my lifetime hopefully!

 

That is all I have for now.  The LH wing flap supports are almost done.  Then some wing panel painting (some but not all of it).  At that point, I will have ticked off all the items required prior to final landing gear installation, and wing half join.   That is a milestone I have been waiting for, for a very long time.  Then - after joining the tail to the fuselage, and temp installing the wings to the fuselage, I get to put "weight on wheels" for the first time!!!  Oh yes.  It's only a week or two away (hard to predict, with all the holiday activities).  You will see it soon. 

Edited December 6, 2018 by JayW

[JayW]

Last on the long list of things to do before joining wing upper and lower halves (and not least) was to permanently install the main landing gear and associated stuff (like shrink link, strut door, strut door links, gear actuator rod, etc).  This was not hard at all, as I had dry fit these parts numerous times.  Pictures of the RH wing (LH is a little behind):

 

 

This shot shows the previously missing bolt which joins the gear retract actuator to the gear itself (just had to show that):

 

 

The black flex hose which is part of the brake line run is now properly connected too.  Cannot tell you how good it feels for all these separate projects to come together like this.  And check this out - it's new:

 

 

That little flap you see there where the strut door meets with the wing lower skin panel is the shrink link flap.  The shrink link, with gear down, would clash with the strut door unless modified.  So it has a slot in it, as does the wing skin itself.  And that little spring-loaded piano-hinged door is there.  But all you P-47 experts know this already! 

 

The long term milestone I have been working toward for months now is "weight on wheels".  What does this beast look like with her shoes on?  To do that, the main gear had to be permanently installed (check!), and the aft fuselage (with tail gear) had to be joined to the main fuselage (check!):

 

  

 

I have some work to do on that join - later.

 

Over a year ago, this picture inspired me to add to my scratch-built engine so that I could display it with canopy off.  Love that picture: 

 

 

 

Well here is my version of it:

 

 

Good Lord this is a big model.  Here are some shots of the landing gear:

 

 

 

The wheel/tire is just slid on the axle, without the axle cap.  I will wait until the wings are finished before I permanently attach them.

 

Here are a couple more shots of the beast on its gear:

 

 

 

This shot is an attempt to show the 3-degree splay of the gear struts, which gives P-47 main gear a bit of a "bow-legged", or over-extended, appearance.  

 

 

By and large I can declare victory on the landing gear.  The two main gear are absolutely symmetrical - got lucky, but worked very hard to try to attain that.  The gear doors and links are fitting up well, the shrink link is well integrated.  And the gear orientation looks realistic to my eye.  I am going to relook at the tail gear and decide if it should extend down a bit more - to me it looks like it has too much weight on it.  Maybe - maybe not.

 

Well I am going to have to make a bigger shelf!  But for now, the next tasks are to actually glue the wings together, paint (including the US insignia stencil by Maketar), finish up and install the ailerons, and then the flaps.  So far I still have all six flap linkages, but they are in constant peril, until I get those flaps installed.

 

Take care all of you, and Happy Holidays!  

 

Edited December 10, 2018 by JayW

[Out2gtcha]

Love it!!!

[MikeMaben]

1 hour ago, JayW said:

                 Take care all of you, and Happy Holidays! 

 

You too Jay.

Shaping up quite nicely.

 

 

[brahman104]

Oh man Jay!

 

You certainly don't like taking the easy option do you? I've got to say you certainly have a knack for replicating complex mechanisms..... a theme which seems to come up in each of your builds!!!

 

Exceptional work my friend..... Keep at it!

 

Craig

[dodgem37]

'So far I still have all six flap linkages, but they are in constant peril, until I get those flaps installed.'

Fold and tape an index card over them.

 

Great update.

 

Sincerely,

Mark

[JayW]

"Fold and tape an index card over them."

 

Thanks Mark - I am going to take you up on that, soon as I get the wing halves joined.  That's easier than a plastic "roll cage".

[JayW]

".....complex mechanisms..... a theme which seems to come up in each of your builds!!!"

 

Craig - I'd wager you were thinking of the "Studebaker hinges" on the P-38 gear doors?  Good God man.  That might bring back my PTSD!

[JayW]

Dang it - I keep finding reasons NOT to glue the wing halves together!  Could be I am psychosomatically paranoid of it.  At any rate it's real good that I positioned and plumbed the gear door actuation cylinder prior to wing half join - it was pretty easy with access both above and below the area; it would have been much harder with access only in one direction.  So I had to fabricate the gear door actuation cylinder with the help of another really nice engineering drawing 89C38180 (thanks Aircorps Library!):

 

  

 

 

Installed - it is supposed to look like this (from wing hydraulics drawing 93C38604)

 

 

 

Note the 45 deg hydraulic fittings on either end of the cylinder, and flex hoses that end on ribs in the wheel bay.  My goal of course is to replicate that even though it is seldom seen (would have to turn this model upside down to see it).

 

My actuator is made from aluminum tube (.093 inch diameter body with .125 inch diameter heads), which is a pretty accurate scaling:

 

  

 

The white (.035 inch dia) plastic rod is of course the drive rod, which will be finished later when I fab and install the gear doors.  The 45 deg elbow fittings were the toughest simply because of their itty-bitty size.  Again I made use of Meng nuts and bolt heads.  I highly recommend this product.

 

Here is the installation of the cylinder in the wheel well:

 

 

 

 

You can see the previously installed thin hydraulic lines from a couple months ago, and the bulkhead fittings that allow them to be joined to the newly installed black flex hoses (which are made from .032 inch dia solder).   It should make sense why the 45 deg elbow fittings were used - makes for a nice clean routing of the flex hoses.  Also you can see that the attaching end of the cylinder mates with a bar of sorts that spans the front spar and a dedicated intercostal that in turn attaches to a stringer on the upper surface.  Note also the large oblong penetration hole in the station 40 rib.  All that boring wheel well work a couple months ago has paid off as I hoped it would.

 

Don't know why I was so jazzed about this little feature - but it probably has to do with the notion that this detail is seldom seen in walk-arounds, and I always wondered how that cylinder was attached in the wheel well.  Hope you like it.