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U-2S "Senior Span/Spur"
Part
Two - Wing & Airframe Construction

by David W. Aungst

 

Assembled Model Before Painting
U-2S_2-Wings-C18.jpg

U-2S "Senior Span/Spur"
Under Construction

 


Cutting Edge's 1/48 scale U-2n accessories and conversions are available online from Meteor Productions
 

Introduction

 
 

This is part two of a three part posting on my U-2S "Senior Span/Spur" project. It has only taken two years to get to this point. Sorry for the delay...

In part one I discussed a brief history of the U-2, a description of the Testors / Italeri kits, and the building of the fuselage on my U-2S model. In this part I will discuss the completion of the fuselage, construction of the wings, and attachment of the wings to the fuselage.

Follow these links to get to the other parts of this posting.

  Part One: Aircraft History, Model Kit Description, and Fuselage Interior Construction
 

 

Construction Continues

 

I left off in the last part with the fuselage having just been assembled. That completed the work on the inside of the fuselage. Now, there are lots of tings to do on the outside of the fuselage.

Before installing the wheel bay unit into the fuselage, I had cut the fuselage sides to open up the engine intake areas. Into these openings, I could now install the rear engine intake duct pieces. First, I painted them following the instruction sheet directions. The inner walls are colored with a color closely resembling Israeli Pale Gray-Green (F.S.34242). I used this color from the old Floquil Military Colors line. Then, I gently pushed them into place inside the engin eintake openings on either side of the fuselage. The pieces are keyed to fit only one way. Scribing on the pieces tells which piece goes on which side.

The fuselage update set completely replaces the forward intake pieces in the kit with seamless one-piece resin engine intakes. I painted the inside of the intakes in the same Israeli Pale Gray-Green that I used on the inner duct pieces, then I attached them to the sides of the fuselage. They do not fit as well as I would have hoped. Shrinkage in the resin causes htem to be a bit small. I fixed this by applying a backing piece of 0.015" sheet styrene on the sides that go against the fuselage. This pushed the intake pieces out enough to remove the step in the surface where the intakes meet the fuselage.

When I constructed the the original intake master pieces, I used the actual kit pieces as a starting point. The result is that the new resin intake pieces still have some of the original fit issues of the kit pieces. I needed to fill voids on the top and bottom of the pieces to achieve a flush surface with the fuselage. I also needed to file down the mounting areas on the fuselage sides because the intake pieces were too far away from the fuselage (based on reference images).

The oil cooler louver details on the outside of the intakes was another sticky point for me. My original masters did not include these details. Considering the nature of the louvers (being mostly flush), I considered using a decal to represent them. As such, I only scribed in the outline of the outer panel. The master pattern maker at Meteor decided to help me and cut in the louvers with some high-tech router milling machine. Unfortunately, this person did not consult enough references to get the louvers right (IMHO). They are too big, too deep, and look more like grills than louvers (IMHO). They are vast improvements on the louvers molded on the kit intake pieces to be sure, but I wanted to tone them down for my model.

Corrected Intake Louver
U-2S_2-Wings-C01d.jpg
Corrected Intake Louver
 
I decided the only real way to do this was to start over. I took a bunch of super glue and filled in the louvers. Sanding this smooth, I re-scribed the panel lines around the louvers. Next I measured and lightly scribed the placement of the louvers and their individual blades. Using a new X-Acto blade, I scraped the lines so as to create the louver blades. It took most of one night and a couple re-paintings with primer to get to the point where I happier with the louvers. The final version is seen in the picture to the right contrasted with the louver as provided in the Cutting Edge resin set.

My version of these louvers is still not perfect. As they are hand carved, there are some irregularities. They also are missing the tabs on the louver blades that give the impression of braces. But, I like my version better as they are much less "in your face" on the finished model. When looking at real U-2 aircraft, these louvers are mosty invisible unless the lighting is just perfect to light up the louver blades.

After working out the fit and permanently attaching the intake pieces, I was very pleased with the view looking in from the front of the engine intake. It is not completely accurate (being a bit too shallow in depth), but you would be hard pressed to see this on the final model sitting on a display table.

 

Inner Engine Intake Pieces
U-2S_2-Wings-C01a.jpg
Inner Engine Intake Pieces
Outer Engine Intake Pieces
U-2S_2-Wings-C01b.jpg
Outer Engine Intake Pieces
View from the Front
U-2S_2-Wings-C01c.jpg
View from the Front
 

With the intakes attached, I started test fitting the ASARS II nose. There is a slight shrinkage when resin cures. To my dismay, I found the nose was smaller in diameter than the kit fuselage -- so much for expecting a "drop in fit" with the nose. Rather than increasing the diameter of the resin ASARS nose piece (which would have necessitated some elaborate putty work to blend the expansion into the rest of the nose), I chose to try to reduce the diameter of the kit fuselage.

Helping me in this pursuit, I had someone in the UK send me an e-mail telling me his ideas that the Cutting Edge ASARS nose seemed to be too short based on his investigations. I decided to take a much more detailed look at the part using some side-view images to measure the details of the nose. Bottom line, yes, the nose is too short by somewhere between four and ten scale inches. Also, the ADF fairing on the top is out of place by a small amount and molded too large.

The ADF issues are hard to see without a tape measure, so I ignored these, but the length of the nose was noticeable to me, so I decided to fix it. I added a 1/8" adapter to the rear of the nose to lengthen it by a scale six inches. This extention acted as an adapter and gave me the chance to start to enlarge the nose diameter to better meet the size of the kit fuselage. I then filed down the forward 1/8" of the fuselage to reduce its diameter to meet the size of the nose piece. Fortuneately, the thickness of the fuselage pieces is sufficient so as to allow this thinning without breaking through.

Effectively, this process slightly decreased the cross-section of the fuselage, nominally increased the forward fuselage taper, and lengthened the nose, but it made everything meet up without having to blend a lot of putty on the nose itself. I glued the nose into place and addressed the seams where it met the reduced diameter fuselage. There are a couple small blisters on each side of the fuselage just behind the nose joint that seem to only be on ASARS equipped aircraft. I whipped up the blister shapes using some strip styrene and attached them in place.

 

ASARS Nose Fit Before Fix
U-2S_2-Wings-C02a.jpg
The Fit of the ASARS Nose Before Fixing It
ASARS Nose Fit After Fix
U-2S_2-Wings-C02b.jpg
The Fit of the ASARS Nose After Fixing It
 

The Italeri horizontal tails have some fine ribs molded onto the upper leading edges. After some investigation, I found these only pertain to early-built aircraft (serial numbers 68-10329 thru 68-10340). The ribs are stiffeners to solve a flutter issue when the super pods were added to the wings. Later-built aircraft (serial numbers 80-1063 thru 80-1099), do not have these ribs. To solve the flutter issue, the later airframes had the interior structure beefed up when they were constructed.

If building a model of an early-built aircraft, leave the kit-provided ribs on the tails. If building a model of a later-built aircraft, remove the ribs. Here is the problem, though -- the ribs should be on both the top and bottom of the tails. The kit only has them on the top.

Horizontal Tail Ribs
U-2S_2-Wings-C03.jpg
Horizontal Tail Ribs
 
The original aircraft I saw at the Andrews AFB air show was a later-built aircraft without the ribs on the horizontal tails. However, I really liked the look of the ribs on the kit tail and decided to change the tail number on my model to be an early-built aircraft with the ribs. This meant I had to scratch-build the ribs on the lower sides of the tails. I did this with 0.010" by 0.030" strip styrene. I rough-cut the taper into the strip, tacked it to the tail, chopped it to the right length, and permanently glued the rib. My results are show here to the right.  

For any modelers considereing whether they need these ribbed tails, for what it is worth, I learned from looking over a U-2 aircraft attrition table that most all the early U-2R airframes have been lost for one reason or another. Most any U-2 seen today is a later-built aircraft that will not have the reinforcing ribs on the horizontal tails. All the ER-2 aircraft flown by NASA and the two-seat U-2R/S aircraft are also later-built aircraft without the ribs.

To help other modelers wanting ribbed horizontal tails, I provided my modified tail pieces to Meteor Productions. The recently released U-2 horizontal tails correction set is made from my masters. I actually used Cutting Edge pieces on my model, here, not modified kit pieces.

The vertical tail on the U-2 is sort-of unique, especially in the way it handles trimming the aircraft. Instead of (or in addition to?) standard trim tabs on the horizontal tails, the entire unit formed by the vertical and horizontal tails is one solid item that is pivoted inside the fuselage to accomplish trimming the aircraft. The thin white or silver line on the leading lower vertical tail is one scuff zone for this unit when it pivots.

Another scuff zone exists all along the lower edge of the vertical tail where the tail slides in and out of the rear fuselage. This scuff zone is black though, instead of the white or silver found at the leading edge, so it is easy to miss on a casual look, but it is there. A glove fairing at the base of the rudder that produces a small step in the surface is part of this scuff area. I wanted to include this fairing on my model and added it using some 0.010" sheet styrene.

 

Vertical Tail Scuff-Zone
U-2S_2-Wings-C04.jpg
Vertical Tail Scuff-Zone
Senior Span/Spur Dorsal Antenna Unit
U-2S_2-Wings-C05.jpg
Senior Span/Spur Dorsal Antenna Unit
 

The next thing I worked on was the bulbous Senior Span/Spur dorsal antenna. Comparing the Cutting Edge pieces to the recent Italeri U-2S pieces, I found I liked the Italeri antenna pod better, but I preferred the Cutting Edge antenna pylon. I cleaned up the Cutting Edge antenna pylon pieces and attached the piece for the large cooling intake found on the left side of the antenna pylon. Then, I assembled the Italeri antenna pod and hacked it off of its pylon. After cleaning up the seams, I attached it to the Cutting Edge antenna pylon. I attached the unit to the fuselage with brass wire pins to make sure it was secure.

Choosing to use the Cutting Edge dorsal antenna pylon opened a can of worms for me. The pylon has recessed scribing while the Italeri kit has raised. I hate when all the components of a model do not match on this detail. I toyed briefly with the thought of adding raised scribing to the Cutting Edge piece, but decided against it. Instead, I broke out my scribing tools and rescribed the rest of the model to match the recessed lines of the Cutting Edge piece. Since the majority of the lines are just long straight runs, this was not as difficult as it can be on some other aircraft.

At this point, I was down to minor things on the fusleage. I added mounting plates and drilled holes for the anti-collision beacon lights that are provided in the Cutting Edge fuselage update set. I would add the lights after I was done painting.

Spine Exhaust Port
U-2S_2-Wings-C06.jpg
Spine Exhaust Port
 
The kit has several molded-in louvers on the upper fuselage. These are way over-done, represented as deep depressions with some molded ribbing. I took a moment to fill most of them in with super glue and sand them smooth. The louvers molded over the wing roots are only applicable to U-2R aircraft with the J75 engine. The aircraft lost these louvers when they were upgraded to the U-2S standard and received a TF118 engine. Since it was a U-2S that I was building, I just filled these and left them go.

The louver on the aircraft spine, just ahead of the Senior Span/Spur antenna pylon, is not a louver at all on the real aircraft. It is an open exhaust vent for the hot air exiting the air conditioning unit behind the cockpit. I drilled this vent open and added some sheet styrene to create the angled forward slope of the vent. In front of this exhaust are a couple louvers that bracket the location of the upper communications blade antenna. I used an X-acto knife to scrape thes in like I did for the louvers on the sides of the engine intakes.

Under the forward and rear fusleage, there are two data link antennae bulges on the U-2. Over time, these antennae have varied in shape and size. Sometimes they are not even installed. Looking at reference pictures, I determined that the aircraft I was building used the more common types of these data link antennae. The needed bulges are provided in the Cutting Edge fuselage update set. I cleaned them up and attached them to the fuselage.

 

Forward Data Link Antenna Bulge
U-2S_2-Wings-C07a.jpg
Forward Data Link Antenna Bulge
Rear Data Link Antenna Bulge
U-2S_2-Wings-C07b.jpg
Rear Data Link Antenna Bulge
 

The last thing I addressed on the fuselage was to drill a bunch of locator holes in the lower center fuselage. These holes would be the locators for the antennae farm found on the bottom of Senior Spear aircraft. The Cutting Edge Senior Span/Spur/Spear update set and the Italeri "Senior Span" kit both provide all these antennae as well as instructions on where they all go.

With the fuselage mostly assembled, it was time to turn my attentions to the wings. Many pictures of parked U-2 aircraft show the wing flaps being down, although the one I saw at the Andrews AFB air show had its wing flaps up. This left me with a quandary -- do I drop the flaps or not? I decided to have the flaps dropped. Besides the look of the model with its flaps down, this would also give me a chance to correct some fit issues on the wings. There is a substantial seam on the wing top that cuts straight through the flaps. Replacing the wing flaps removes this wing seam when the kit's wing flaps are cut off.

I used the Cutting Edge U-2R/S / TR-1 Wing Correction set. Having created the masters for this set, there were no surprises in its usage. Not only does the set provide dropped wing flaps, it also provides replacement super pod tail cones, corrected antenna fairings, and properly sized ailerons along with some other minor details.

I started by cutting the wing flaps and ailerons off of the kit wings. I then measured the distances carefully to where various items should be located and further cut the wings to make these details line up correctly. The exact measurements are outlined in the Cutting Edge instructions.

 

Cut and Uncut Wings
U-2S_2-Wings-C08.jpg
Cut and Uncut Wings
 

Before I assembled the wings and started attaching the correction set pieces to the wing, I took time to re-scribe the wings to engraved scribing. As it was all just long straight runs, this was done easily with a metal ruller and an X-acto #11 blade drawn backwards over the wing surface. A few of the kit scribed lines are located in the wrong place, so I also took time to measure out the corrected locations and scribe the lines. Most notable amoung the incorrct lines are the wing fold lines. They should be 70 inches from the wing tip. Italeri molded them about a scale foot (a quarter inch) too far inboard.

Assuming the wings are cut correctly, the resin pieces attached to the wing easily. I missed by a little on one of the spoiler wells and had to add a strip of styrene to fill a gap that I created by accident. The instructions say "measure twice, cut once", but I always get too excited to take time to be that thorough. I permanently attached the super pod tail cones, spoiler wells, System 20 and GPS fairings, and the ailerons. I left the wing flaps loose until after doing some painting. With the mounting tabs on the flaps, they hold themselves into place quite well, so I could get the look of the wings without committing glue to the flaps.

There is one quick fix to make on the resin wing pieces. When I made the masters, I accidentally scribed some bad lines on the outboard flaps. I thought I had sufficiently filled in the bad lines, but in the resin pieces you can still see the hint of them. Note the pointer in the one image below and remove all traces of the line being pointed to in the pictures. The same line is present on both sides of both outboard flaps. Sorry...

 

Wing Flaps Installed
U-2S_2-Wings-C09.jpg
Wing Flaps Installed
Wing Correction Detail
U-2S_2-Wings-C10.jpg
Wing Correction Detail
 

 

Flap Angle Detail
U-2S_2-Wings-C10a.jpg
Flap Angle Detail
 
Next, I turned my attention to work on the super pods. In the "Sky Patrol" kit, the super pods are simple tubes with rounded cones that fit on the front and rear of each wing-mounted center section. There are no bulges or antennae provided. In the "Senior Span" kit, the nose cones of the super pods are modified to incorporate the flattened sides of the Senior Ruby installation and the canoe fairing for the left super pod is included for the Senior Spear installation.  

Wanting to have my model outfitted with both Senior Spear and Senior Ruby (collectively referred to as Senior Glass), I built up the Senior Ruby nose cones for the super pods and attached them to the wings, orientating the flat spots at a slight angle down from facing straight out to the sides. I studied all the pictures I could find and decided to use the Italeri kit canoe fairing under the left super pod. I am not convinced that its shape is any better or worse than the Cutting Edge equivalent piece, it is just different. The selling feature for me was that the kit canoe fairing fit better onto the super pod.

 

Senior Ruby Super Pod Nose
U-2S_2-Wings-C11a.jpg
Senior Ruby Super Pod Nose
Senior Spear Super Pod Canoe
U-2S_2-Wings-C11b.jpg
Senior Spear Super Pod Canoe
 

Then, I addressed the seams where the super pod nose cones are attached. With a little pre-work to flatten out the mating surfaces, the cones mounted with only a small seam. I filled this and sanded it smooth. Then, I turned right around and scribed a panel line right where the seam line had been. I continued on to scribe lines around the super pods based on the diagram in the Cutting Edge Senior Spear/Span instructions. With the scribing done, I located and drilled holes along the pod centerlines to mount the Senior Spear blade antennae.

The last details I added to the super pods where a series of small intake vents along the outside of each pod. These are provided in the Cutting Edge wing correction set. There are three intakes on the left pod and two on the right. Shrouded in shadows under the wings, I did not even know these intakes existed before I started researching to create the wing correct set masters. Some pictures I got from a source on the Internet highlighted them to me. Knowing about them, I was then able to find them in my own pictures, too. It is amazing how long you can look at some pictures and not see some details.

The wingtip skids from the kit are fine. I cut these from their sprue and attached them on the wingtips. The ECM pods that attach to the skids are also pretty much fine right out of the kit. I did add some laminated sheet styrene to their end plates with punched out holes to represent the round center antenna points, then attached the pods to the skids. I also filed off the solid kit navigation lights and drilled holes to mount Cutting Edge clear red/green lenses from the generic Cutting Edge navigation light sets.

With the wingtips done, I moved to the undersides of the wings. First thing here is to change the location of the pogo leg mounting holes. Italeri molds the holes too far inboard. They stay within the same scribing panel, but move outboard to the outer edge of the panel. Picturtes show what looks like a reinforcing plate where the pogo legs attach, so I built this up using 0.005" sheet styrene. Then I drilled the mounting holes for the pogos.

The final additions to the wings were the fuel cell pressurization intakes. These small scoops are found in the lower middle of the wings, just inboard of the attachment points for the pogo legs. These are also provded in the Cutting Edge wing correction set.

 

Super Pod Vents
U-2S_2-Wings-C12.jpg
Super Pod Vents
Wingtip
U-2S_2-Wings-C13.jpg
Wingtip
Fuel Cell Pressurization Scoop
U-2S_2-Wings-C14.jpg
Fuel Cell Pressurization Scoop
 

With all these wing modifications complete, it was time to rent a gymnasium to hold the fully constructed model. Thus, I started the process to attach the wings to the fuselage.

As I was dry fitting the wings to the fuselage, I came to the realization that the wing joint was going to be a weak point in the model. And, the lowered wing flaps had decreased the size of the mounting area for the wings. There is more than twelve inches of wing hanging off each side of the fuselage. Those long wings have relatively small mounting areas with their locating tabs being rather short (in comparison to the overall length of the wings). Even if I did manage to firmly attach the wings to the fuselage, the weight of the wings hanging on the model could potentially split open the upper fuselage seam. I decided I wanted to add a length of brass tube as a wing spar to add strength to this joint. This would also help to align the wings for attaching them and keep them aligned after they were attached.

 

Wing Spar Modification
U-2S_2-Wings-C15.jpg
Wing Spar Modification
Fuselage with Wing Spar
U-2S_2-Wings-C16.jpg
Fuselage with Wing Spar
 

To start the process, I measured and cut away a center portion of the wing locator tab on each wing. I then drilled an appropriate sized hole (1/8th inch) in the wing inner edge at the place where I had removed the locator tab section. It was important that these holes in the wings would line up with each other so the spar would fit straight across from one wing to the other.

With the wings modified, I then measured the fuselage to locate the correct positions of the holes to pass the wing spar though. Drilling more holes in these locations on the fuselage set up the whole assembly to be completed. I measured the brass tube to determine how far into each wing I needed the spar to go, then cut it to the determined length (5 inches). This provided about an inch and one half of spar sticking into each wing. That seemed enough to me. After making sure the spar was level in the fuselage and that the wings fit as I wanted, I super glued it in place on the fuselage. I then slipped the wings on for a final check. With everything lining up the way I wanted, I glued the wings to the fuselage.

I reworked and modified many more places on the model than I thought I would at the beginning of the project. The picture below shows the model just before I painted it. With the black plastic of the original kit, all the modifications in white plastic and gray/beige resin stand out quite well.

 

Assembled Model Before Painting
U-2S_2-Wings-C18.jpg
Assembled Model Before Painting
 

This completed the airframe construction. Time for painting. As the descriptions have gone on here long enough, I decided to break here and have the painting and finishing of the kit be a third part in my U-2S "Senior Span/Spur" project postings.

References

(Newest to Oldest)

  • U-2R/S Walk Around by David W Aungst
    On-Line HyperScale Reference, 2003

  • U-2: The Second Generation by Chris Pocock
    World Airpower Journal, Volume 28, AirTime Publishing, 1997

  • Dragon Lady by Ted Carlson / Toyokazu Matsuzaki
    Koku-Fan Magazine, Volume 1996-04, Bunrin-Do Company, Limited, 1996

  • Recce Tech by Paul F Crickmore
    Osprey Color Series, Osprey Aerospace Publishing, 1989

  • U-2 Spyplane in Action by Larry Davis
    , Squadron In Action #86, Squadron Publishing, 1988/2002

  • Lockheed U-2R/TR-1 by Jay Miller
    AeroFax MiniGraph #28, AeroFax, Inc., 1988

  • Lockheed U-2 by Jay Miller
    AeroFax AeroGraph #3, AeroFax, Inc., 1983


Model, Description and Images Copyright 2005 by David Aungst
Page Created 25 October, 2005
Last Updated 25 October, 2005

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