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

[airscale]

wow, lots of stuff going on here Jay - I am stressing out thinking about you stressing out

 

I know it's easy to say after the fact, but any panels with just one line of curvature (ie not compound) can be pre-shaped by rolling. I use a 1 inch brass tube and a block of chair foam (or a thick mouse mat) to help the panel come to terms with it's new shape so that it doesn't try and pull away and straighten. If anything over curvature is good as that way the force is inwards, rather than pulling away from the surface. It may or may not have helped and you certaaily had a lot to deal with in adding multuiple access hatches in the same panel

 

personally, I think it looks great, these things came on and off all the time and on some airframes are REALLY bad fits (like the Fw190D) so nothing wrong with a bit of deviation..

 

I share your anguish with skinning the wings, you know by now it involves a lot of handling and putting the model through stress. Given the proximity of the fragile parts it won't be easy thats for sure, so some pre-acceptance of damage / repaair is a good thing

 

You can avoid quite a bit of trouble with those air intakes by just building up a thin filler layer to a panel line and skinning up to that, rather than trying to actually skin the intake itself (see my P40 carb intake) this is what I do for really horrible intake areas where it is virtually impossible to get the material to conform to acute compound curves. It works even better for you as you are painting the model

 

Whatever happens, we are all rooting for you and as always if I can help in any way, let me know

 

Peter

[LSP_Kevin]

This is so good it makes my head hurt! Fantastic stuff, Jay.

 

Kev

[JayW]

1 hour ago, airscale said:

I know it's easy to say after the fact, but any panels with just one line of curvature (ie not compound) can be pre-shaped by rolling. I use a 1 inch brass tube and a block of chair foam (or a thick mouse mat) to help the panel come to terms with it's new shape so that it doesn't try and pull away and straighten. If anything over curvature is good as that way the force is inwards, rather than pulling away from the surface. It may or may not have helped and you certaaily had a lot to deal with in adding multuiple access hatches in the same panel

 

Hi Peter!  Thanks for looking in.  Yes - I remember your previous suggestions on how to contour single curvature panels.  And that is exactly what I did.  What I think is happening here is that the contour is transitioning from round at the forward end of the panel (at the diaphragm) to more oval at the aft end, where the upper fuselage mold line tilts slightly upward, presumably to allow the cockpit to be higher (aids looking over the nose I guess), while the width is actually decreasing.   Hellcats have this feature except more pronounced I think.  At any rate, it seems to introduce a touch of compound curvature, just enough for the skins to misbehave.  I had trouble with some fixed panels further aft, you might recall, only worse.  Ended up with some ripply edges here and there.  The mismatches you see have two components - one is lifting of the panel due to stresses in the aluminum skin - this is very slight if at all.  And two, more of a problem, the build-up of my removable panels where they attach to the fuselage is a bit thicker than I planned.  And/or the attach flanges on the fuselage that have the magnets are not as deep into contour as I hoped for, for whatever reason (possible a varying fuselage gage).  This leads to the removable panel, in some places but not all, being a bit too proud.  Filing and sanding helps but I can only do so much.     

[Thunnus]

Wow... always astounded by the fabrication you do! Contour mismatches do not look very significant to me... I can hardly notice them.  But it's what your eyes see that count!

[JayW]

Wing skinning - I felt (still do) that if I can get good aluminum skin panels on the forward gull wing portion of the wing, then the rest will be easier.  And if it failed miserably, then I'd pull them off and do a plan "B" (currently undefined).  These panels:

 

 

 

Here is a shot from the Vulture's Row birdcage resto:

 

 

Can you believe the amount of fastening????   

 

So I started out on the LH wing.  The challenges:

 

1.  Match the contour with the adjacent LE intake panel (no step)

2.  The severe compound curvature, especially the upper panel

3.  Good butt join at the leading edge

4.  Do not break off the gear strut or gear door

 

One of the biggest excuses I had for not skinning the wings is the LE intake panel.  It's impossible to skin, so I knew that adjacent aluminum skins would create a step around its periphery.  Peter had suggested repeatedly to build up the edges of the intake panel using P-38 or the like.  A good idea except not in my skill set.  Instead I sought to sand and grind down the edges of the adjacent surfaces about .005 inch, to negate that step.  That was very hard work, but that is what I did.  So far so good - these two panels, and some others, will butt up against that LE intake panel.

 

The compound curvature made it tough to get the panel periphery trims right.  You cannot just lay down masking tape and trace the edges.  The tape wrinkles, of course, when you lay it down on the wing, and makes the edges inaccurate when you flatten it out on a piece of aluminum sheet stock.  Took two tries on the bottom panel, and one on the top panel, but just shear time and determination finally gave me good edges, including the very tricky curved butt join on the leading edge splice line.

 

The other big excuse for not skinning the wing was possible damage to the landing gear and gear doors.  Well I have decided to take that risk.  The gear strut got nudged repeatedly, but held firm.   The struts are pretty strong.  The outboard gear door, on the other hand, has a nicely fractured forward gooseneck hinge, fractured right at the gooseneck.  It is somewhat repairable, but will be a bit unsightly if you look for it.  Oh well - that is a casualty that I knew would happen.  It will be OK.  I'm not going to fix it until I finish the wing skinning effort.

 

OK, drum roll please......

 

 

 

 

 

I had to use annealed aluminum, which shows every possible imperfection of the underlying surface, including the adhesive.  Also, for the upper panel, I was unable to create the fastener patterns on the flat panel on the bench (I use a glass pane for hardness), and had to do it on the wing.  Once that wild contouring was done, no way was I going to flatten it back out to do the fasteners.  That makes accuracy harder, and the depressions are a bit deeper because the underlying surface is not as hard.  You be the judge, but I attempted to duplicate all those hundreds of fastener heads you see on the real thing.  It's a little "lumpier" than I want; the only way to have improved that would have been to further thin down the adhesive before bonding down the panel.  The shininess accentuates any imperfection; I am expecting a flat final top coat will make it look OK. 

 

I should have taken a picture of the upper panel at the point where I pushed it into that double-curved concave reverse gull wing shape.  The middle just collapsed into an ugly bunch of wrinkles, worse than the "test panel" I tried last week.  This modeler's hair caught on fire for a moment.  But amazingly after lots and lots of burnishing with balsa sticks, it smoothed out.  Same for the lower panel LE trim - it wrinkled badly at first, but it also burnished out.  The leading edge butt splice took hours of trim/fit/trim/fit/trim fit.  I am very happy with it though. 

 

This was pressure packed work, and took a few days to get through it - now I have to do it again on the RH wing. 

 

Next post I'll show the RH wing, plus a bunch of other panels.  Not sure how far I will go - will I skin the flaps, will I tear off the flap doors underneath and redo using aluminum....all TBD at the moment.  See ya' next time!      

 

 

Edited June 7, 2022 by JayW

[Jim Barry]

The balsa stick is a foiler's best friend! My Fury cowling would never have made it without it. Great work! Thanks for the updates

 

https://forum.largescaleplanes.com/index.php?/topic/69495-124-hawker-fury-biplane-scratchbuild/&do=findComment&comment=940788

 

 

Edited June 7, 2022 by Jim Barry

[geedubelyer]

 

If you dressed your parts with a little blue ink they'd look identical to the reference picture above. 

Tremendous work, well done 

 

Good luck with the remainder. I shall keep my fingers and toes crossed for you. 

[LSP_Kevin]

Fantastic work, Jay! Your perseverance and determination - along with your considerable skills - are winning the day.

 

Kev

[Troy Molitor]

So so nice Jay.  Loving this.  

[brahman104]

Brilliant work Jay! I don't know what you were worried about, the skins look AMAZING! 

 

Craig

[airscale]

18 hours ago, brahman104 said:

Brilliant work Jay! I don't know what you were worried about, the skins look AMAZING! 

 

Craig

 

+1

 

..very fine job there Jay, I can almost feel your confidence growing and panel by panel this will be your magnum opus

Peter

[JayW]

On 6/7/2022 at 11:32 AM, Jim Barry said:

My Fury cowling would never have made it without it.

 

Jim - that is sooooo good!  Dam.

[Maybach_man]

On 6/7/2022 at 10:36 PM, MARU5137 said:

Hello Jay,

Well you certainly have worked hard over a few days to get your results to be perfect... your tenacity knows no bounds and having read through *at least thrice * your detailed explanation  about skinning etc; I think with your engineering  skills you are doing an AMAZING  Job.

Splendiferous  workmanship Sir. 

Very detailed,  informative  & comprehensive  posts..

  The 3 Dimensional  Shoulder  parts are super.

Looking ahead to see how you tackle the gaps !?!

 

I dont know what "annealed aluminum"  means. you mentioned it ... thank you  Jay.

 

Annealing is when you heat the metal (aluminium) and it 'softens it to make it more malleable' You can use a hand torch. A tip would be to rub some domestic soap on the surface of the piece and when it turns black its done...

[Pete Fleischmann]

On 2/20/2022 at 11:18 AM, JayW said:

 

 

 

 

Hi Jay!

I am loving this build! very cool.

can you tell me your technique for cutting holes for access panels in the aluminum? That came out perfectly-

 

cheers

Pete

 

 

 

[JayW]

On 6/11/2022 at 6:31 AM, Maybach_man said:

Annealing is when you heat the metal (aluminium) and it 'softens it to make it more malleable'

That is correct, although in my case I actually purchased a roll of annealed aluminum sheet.  Know what I wish?  That annealed aluminum could be easily heat treated.