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Attaching the outer wing panel to a B-17

Attaching the outer wing panel to a B-17


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Attaching the outer wing panel to a B-17

Here we see ground crew at the 2nd Strategic Air Depot, Abbots Rippon, attaching a new outer wing panel to a B-17 Flying Fortress.

Pictures provided by Sgt. Robert S. Tucker Sr. (Member of: The American Air Museum in Britain {Duxford} ).
Robert S. WWII Photo Book, Mighty 8th. AF, Ground Crew


William Leroy Barton

He graduated from Moody Field, GA. Flight Officer T62413. He was with the 8th A.F., 457 Bomb Gp (H), 748th Bomb Sqdn. On July 31, 1944, his B-17-G (S/N: 42-97087) with a 10-man crew was hit by flak over the target, Munich, Germany. The plane began to disintegrate quickly with part of one wing falling off.

Barton’s description of the crash from MACR #7829 follows:

We were hit on the bomb run in the nose. At that time I think F/O Firing (bombardier) was wounded. (Navigator F/O Irving Cohen said later that Firing waved him on when Cohen took ahold of his arm, so Cohen bailed out.) After "bombs away" we started to "peel off" to the left and lose a 1000′. We had the plane at a 45° angle and a burst of flak tore a large hole in the right wing behind No. 3 engine and the flaps and entire outer wing panel ripped off. The pilot, Lt. Byron Schiffman, bailed out. I got my flying boots caught in the rudder pedals but got loose and followed him to the nose escape hatch. (As soon as the ship was hit it fell off in a steep spin to the right. However it went into a flat spin soon afterwards). I started to bail out but saw Firing bent over the chair and bombsight in the nose. I grabbed him by the chute shoulder straps but lost my grip. I tried three or four times to get him out. He made no effort to help himself and fell forward each time. I never saw his face but I assume that he was wounded. The last time I had his shoulders about to the bulkhead but due to the centrifugal force, the plane’s nose at a fairly steep angle and him making no effort to help me I couldn’t lift him out of the nose and I lost my grip again and he fell forward so I bailed out. I am sure that I was the last one to bail out of the ship because I think I got out at approx. 5,o000 feet or less and delayed my fall because I couldn’t get out from under the ship which flattened out in its spin and had both outer wing panels gone and the tail behind the radio room gone, to around 1000 to 800′ approx. The ship barely missed my chute and crashed in an open field and burst into flames. My chute swung about twice and I almost went into the flames which leads me to believe that I was last out of the plane. I saw no other chutes around me but I was dazed and trying to escape so might have missed them. The plane kept exploding at times so I’m sure no one could have survived the crash. We were talking to the crew of the ship ahead of us in prison camp later and they said that the tail of our ship was blown off so I imagine that some of the crew were blown out. This is all I can remember. I can’t be absolutely positive on any details because events happened so fast.

Pilot (Lt. Schiffman) said that while he was floating in the air he saw another chute at quite a distance so he yelled, "hello". The man in the other chute answered back. It might have been the engineer who may have been killed by civilians after reaching the ground.


Build Your Own Most Famous Stork

World War I French troops hunkered down in trenches called the Nieuport 17s circling above them “silver hawks.” One of the best-known silver hawks was flown by Georges Guynemer, recognized by many as the “most famous stork,” a reference to the red and blue bird emblazoned on the side of Escadrille N.3’s aircraft.

Eduard’s 1/48th scale Nieuport 17 (kit #8023) is complete with all the modifications, painting masks and markings needed to build Guynemer’s aircraft as it appeared in July 1916. Construction starts with painting the sidewalls and floor of the cockpit “wood.” The seat is “leather,” with belts made from paper strips. Stain the strips with black coffee, and while they are still wet drape them over the seat to give the straps a realistic arrangement.

The rest of the cockpit has a throttle side panel and rudder bar that should be painted aluminum. Strangely, there is no instrument panel included in the kit, but you can easily make one from a piece of styrene stock and a few dots of paint. Don’t spend too much time on the cockpit, however, since not much is visible once the fuselage is assembled.

Attach the bottom wing and the horizontal stabilizer to the assembled fuselage and set aside to dry. A complete 110-hp LeRhône 9J rotary engine, unique to Guynemer’s aircraft, is contained in a separate bag in the kit. The engine should be painted steel with a wash of gloss black to bring out the details. An additional cutout portion of the cowling, included in the kit, is attached to the top center.

Nieuports belonging to N. 3, with a few exceptions, were painted overall with an aluminum dope to protect the linen fuselage covering from ultraviolet light. Painting the entire model one shade of aluminum is correct, but to give it some depth of color try to break up the finish by using various shades of the silver paint. The cowling and the forward portion of the fuselage were aluminum and can be painted with Model Master’s “buffing aluminum.” The remainder of the fuselage and wings should be sprayed with Floquil’s “platinum mist” (a lusterless shade that gives the appearance of paint on fabric).

The vertical stabilizers of French WWI aircraft were painted red, white and blue. Decals are provided in the kit, but they don’t fit well. Paint this control surface overall insignia white (FS-17925), and when it’s dry, use the kit masks to paint the rear portion insignia red (FS-31136). The forward section is U.S. Navy blue-gray lightened with a little white, so that it matches the center color of the French insignia roundel.

One of the distinctive portions of Lieutenant Guynemer’s aircraft was the nonrotating “cône de penetration” that was attached to the front of the propeller to alleviate some of the drag caused by the LeRhône engine. Spray the cone white and then, using the masks provided in the kit, employ the same colors as on the vertical stabilizer. (This is not an easy task and requires a steady hand.) The cone was only on the aircraft for a short time and can be excluded if you choose. Another important feature of Guynemer’s aircraft, included in the kit, is the top wing with the two special cutouts that gave improved upward vision during aerial combat. Micro Scale “crystal clear” can be used to fill in these cutouts in final construction.

The outer wing struts should be painted “wood” and then, when dry, masked and the metal strengthening bands painted aluminum. There are decals in the kit that can be used for this job. To add additional interest to an overall silver model, paint the inner wing struts and the landing gear assembly light gray (FS-36375), mixed with a little aluminum. Do not assume that WWI aircraft tires were always black. Most were light gray or light brown, and some were actually pink. Model Master gray (FS-36231) is a good match.

WWI Nieuports carried the French roundel on the top and the bottom of the upper wing. Apply the national markings and then attach the outer wing struts using white glue. The inner struts can be cemented in place now, and then the top wing can be glued to lower wing and the fuselage.

Nieuport 17s had relatively few bracing wires. Minimeca (ref. 106) stainless steel 0.20-by-250 wire is excellent for this job. Use a pair of dividers to determine each wire’s length and attach them with white glue. The final task is to paint and attach the windscreen to the area in front of the cockpit.

Originally published in the September 2006 issue of Aviation History. To subscribe, click here.


What’s in the Box

The standard Midget Mustang and Mustang II airframe kits include a fully assembled and powder-coated center section, pre-bent parts that would be beyond simple hand-tool capability and pre-rolled wing leading edges. The fuselage bulkheads and control surfaces are pilot drilled, as are most of the wingskins. Not included are the engine mount, fuel tanks, wheel and brake kit, canopy, cowling and tips.

The quickbuild options include fully completed wings or partially built wings, assembled tail group spars, and deburred and powder-coated steel parts. Full quickbuild kits cost $22,625 for the M-1 and $27,700 for the M-II, which adds the “not included” items above. Construction drawings must be ordered separately from the kits, $125 or $225.


Going All-Out With A Classic Balsa B-17-F – Part 7

I finished our last building session by closing up (adding the last of the 1/16”balsa sheet skin) the lower surface of both wing panels and doing some final reinforcement and preliminary sanding around the flap well access. With that done, the next step is to locate, mark and cut out the portions of the wing skin that are now covering (and hiding) those flap and aileron servos along with all the access to cables, connections and so on that I want to build into this airplane. That’s where we’ll start this time.

B-17-7-1 When I framed in the four flap and aileron well/access hatch locations and sanded them flush with the rest of the wing surface/ribs and spars it was with the intention of closing up the entire bottom surface with a single sheet of 1/16” balsa. On this model that makes more sense than trying to “piece together” a wing skin of multiple sheets arranged around the various openings…that would be a good way to introduce lots of “discontinuities” (bumps). The downside of closing the structure with a single sheet is that I have to locate those openings through it and cut them out without marring the balsa sheet around them. Pre-marking the exact openings on the sheet before assembly would have required exact registration (alignment) during assembly. I prefer to devote all my attention to getting the balsa sheet skin attached smoothly and consistently to the underlying structure and then deal with all these openings like this…by measuring from the plans I can locate and mark the approximate center of each opening and be “off” by quite a bit without causing trouble. Watch…

B-17-7-2 I have rough-cut a hole about an inch across as close to the middle of the hidden flap servo hatch opening as I can get. Now I’m slicing carefully through balsa that’s eventually going to be cut away while the blade locates the exact edge of the pre-framed opening.

B-17-7-3 With that done it’s no big deal to locate the rest of the edges by “feeling” with the No. 11 blade.

B-17-7-4 Off camera I drew in pencil lines to mark the edges of the cutout I wanted to make, keeping my cuts at least 1/16” inside where the finished edge will be. Then I could easily see what I was doing using this 100-grit sanding block to finish each skin-to-hatch transition neatly.

B-17-7-5 With that done, along with a few passes with 320-grit paper on the wider block to double-check that the whole deal is smooth and even, the new flap servo access opening looks like this. I’ll work on the actual cover plate (all four of them) later in the construction process.

B-17-7-6 All that work on designing, cutting out and fitting the landing gear mount assemblies leads up to this. This is the right main gear assembly seen from in front and below. Did you notice that there is balsa structure (an N-1 former) that is going to be in the way when I try to retract the strut? I have a good reason to leave that as-is for now…watch this space for an explanation later.

B-17-7-7 How do you cut out CLEAN stringer notches into formers like these N-1’s AND keep them all in line from one former to the next? As it turns out, although most of the stringer notches in this kit are pre-cut, there are a few places (like the corner longerons on each of the nacelles) where I need to re-define them. One of those old time tricks that I learned from Cleveland kits during the 1950’s is to glue a strip of medium-fine sandpaper cut toa precise width (here that’s 1/8”) to a straight piece of hard balsa of the same thickness. That custom cutting/sanding tool looks like this…

B-17-7-8 …and using it looks like this. The kit plans does not show clearly that we need a 3/32” sq. balsa stringer here, but with all the adjustments I’ve been making to the structural design, including them has become necessary to ensure a smooth, consistent outer contour when I skin the nacelles with 1/16” balsa sheet.

B-17-7-9 Here you get a good look at the “new” stringer notch I have cut into the assembled nacelle along the outer edge of the longeron. I’ll put the extra stringer in place in just a moment. Right now, though, I’m using Deluxe Materials Roket Hot to assemble the free rear end of this side stringer to the 1/16” balsa sheet wing skin. Look closely…the rear end of the stringer is tapered/beveled to match the odd angle of the joint exactly. You can also see that the front end of the stringer lines up with the curve that the stringer (and later the nacelle skin) will follow when I bend it to fit into the corresponding notch in the front N-1.

B-17-7-10 All that happens when I use “calibrated thumb pressure” to form the bend. I’ll use a generous drop of Deluxe Materials Roket Hot to lock up that joint.

B-17-7-11 More of the same. All the remaining 3/32” sq. balsa nacelle stringers get installed in the same way.

B-17-7-12 With all the stringers on the nacelle in place I can use my 100-grit sanding block to cut off all the overhanging excess balsa and true up the face formed by the front N-1’s.

B-17-7-13 While you weren’t watching I finished assembling the stringers to the remaining nacelles and cleaned up the front faces of each of them the same way. Now I need to make sure that the outer nacelle circumference/surface that is defined by each group of assembled stringers is accurate. The curves defined by the outer faces of the stringers dictate the shape of the 1/16” balsa sheet skin (the outer surfaces of the finished nacelles) that comes next. If you don’t get that right now, the error will always show. Important note: The assembly of N-1’s, stringers and glue joints that I have to cut/sand “perfectly round” is just about guaranteed to be harder (tougher to sand) than the 1/16” balsa sheet skin it is going to blend into. If I don’t protect that skin adjacent to the structure that I’m going to shape with the sanding block I’ll almost certainly scuff and gouge it seriously. That’s why those protective layers of masking tape are in place wherever the abrasive could slip and cut whatever happens to be in its way. Can you see that right here working “around” the nacelle in a spiral pattern?

B-17-7-14 This is the same nacelle seen from the other side. You can see some of the sanding dust that shows I’ve cut away a considerable amount of wood. This is one of those aeromodeling tasks that must NEVER be rushed…you have to sand and check and sand some more until the surface curvature you are defining is correct or the errors you leave in your work will always show.

B-17-7-15 When I have all four nacelles shaped and sanded the way I want them…top and bottom, front and rear…I can go on to the next step of making paper patterns for the various sections of 1/16” balsa sheet skin that will close up and define the outer nacelle surfaces everyone is going to see. This is one of the important changes I’ve chosen to make from the kit design…originally these nacelles were intended to consist of tissue covering over exposed stringers. As I have suggested earlier, I am so turned on by the look of a classic, round radial engine cowl and nacelle that I’m not willing to compromise. The small increase in weight is going to be part of paying my dues for improved scale appearance. Making the various paper patterns for the panels that form the nacelle skins is a cut-and-try process. I made the preliminary paper pattern you see for the panels that fit both the inboard and outboard halves of the rear portions of the right outboard nacelle by tracing roughly against the structure and then drawing a “clean” copy on fresh paper using a drafting curve.

B-17-7-16 Test-fitting the pattern to the actual structure revealed the need for a bit of extra width/depth at the rear outside edge. If you look closely you’ll see where I have marked the error with a pencil line.

B-17-7-17 In this image I’m again using a drafting curve to mark a smooth curve (that should match the contour of the wing skin accurately) onto a corrected pattern on yet another fresh piece of paper.

B-17-7-18 When I cut out THAT pattern and checked it against the nacelle structure it fit correctly, so I went on to use it to mark cutting lines onto a piece of the 1/16” balsa sheet that I had already selected for the nacelle skins. Here I’m using a No. 11 blade to cut the critical curvature/edge that MUST match the shape of the wing skin.

B-17-7-19 Remember what I said about “cut-and-fit”? Holding the newly-cut balsa panel in place I can see that it comes close to matching the wing leading edge curve…BUT…I can still make it fit better.

B-17-7-20 Some 100-grit paper on a round block is just what I need to “open up” that inside curve just a bit…

B-17-7-21 …with the result that it now fits with noticeably improved accuracy. Off-camera, I dampened the outer surface of the panel with water and glued it into place.

B-17-7-22 I finished closing up the rear portion of all four nacelles in pretty much the same way. Here I’m using a new pattern to begin marking more 1/16” balsa sheet for one of the inboard nacelles.

B-17-7-23 Just as before, I test-fitted each panel to its final location on the airplane and corrected wherever it was necessary.

B-17-7-24 Now I’m applying a bead of Deluxe Materials Roket Rapid to the critical edge of the panel…

B-17-7-25 …and pressing it (very carefully) into place, aligned /fitted to match the wing skin. I have left all the other edges of this panel slightly oversize so I can fit and trim them to an exact match where the panel contacts the nacelle structure…then with this first/most critical edge glued securely I can roll/wrap/press the remaining free edges into place and glue them in turn. Did you notice my other “freebie tool”? Paper towel rolls make excellent pads to rest potentially vulnerable structure on while you’re working on it.

B-17-7-26 Now I’m going to sheet/close the forward section of the nacelle. Because this portion of the structure…from the sub-firewall to the second former station…is cylindrical (not tapered) the sheet covering panels likewise don’t have to be tapered, so making them is a lot easier. Here I have aligned what will become the rear joining edge of the new panel with the structure it has to match and I’ve drawn a straight pencil line to mark a simple cut that will give me a panel section (grain along the axis of the nacelle for easy bending) with enough overhang in the front to give me room for adjustment if one part or another of the front former isn’t exactly square.

B-17-7-27 I have cut the new panel section along the line a marked and held it in place where it’s going to go on the nacelle. Notice that I have carefully aligned the “bottom” edge of the panel/sheet along the nacelle side stringer where it is going to be attached. With that alignment as a reference I then made those pencil marks along the top stringer…they become the alignment reference for the top of the panel.

B-17-7-28 As it turned out that top/front panel “blank” fit so well that I left it long enough to wrap around to the inboard nacelle side stringer, giving me one-piece coverage of the top 180 degrees of the nacelle circumference. Again off-camera, I water sprayed the outer face of that panel, then applied Deluxe Materials Roket Rapid to all the joining surfaces on the nacelle, wrapped the panel into place and used calibrated hand pressure to hold it firmly-but-gently exactly where I wanted it to be. With an “open joint” cyanoacrylate adhesive like Roket Rapid and consistent “clamping pressure” on a joint like this, a minute or so is all it takes for the CA to grab. This is an example of one of those places where “hand-holding” makes more sense than the time and effort of taping, clamping, etc., to get the same result.


Fairchild PT-19

The PT-19 series was developed from the Fairchild M-62 when the USAAC first ordered the aircraft in 1940 as part of its expansion program. The cantilever low-wing monoplane with fixed landing gear and tail wheel design was based on a two-place, tandem-seat, open cockpit arrangement. The simple but rugged construction included a fabric-covered welded steel tube fuselage The remainder of the aircraft used plywood construction, with a plywood-sheathed center section, outer wing panels and tail. The use of an inline engine allowed for a narrow frontal area which was ideal for visibility while the widely set-apart fixed landing gear allowed for solid and stable ground handling.

The M-62 first flew in May 1939, and won a fly-off competition later that year against 17 other designs for the new Army training airplane. Fairchild was awarded its first Army PT contract for an initial order on 22 September 1939.

Production began in 1941 and 3,181 of the PT-19A model, powered by the 200 hp L-440-3, were made by Fairchild. An additional 477 were built by Aeronca and 44 by the St. Louis Aircraft Corporation. The PT-19B, of which 917 were built, was equipped for instrument flight training by attaching a collapsible hood to the front cockpit.

When a shortage of engines threatened production, the PT-23 model was introduced which was identical except for the 220 hp Continental R-670 radial powerplant. A total of 869 PT-23s were built as well as 256 of the PT-23A, which was the instrument flight-equipped version.

The final variant was the PT-26 which used the L-440-7 engine. The Canadian-built versions of these were designated the Cornell

Operational history Compared to the earlier biplane trainers, the Fairchild PT-19 provided a more advanced type of aircraft. Speeds were higher and wing loading more closely approximated that of combat aircraft, with flight characteristics demanding more precision and care. Its virtues were that it was inexpensive, simple to maintain and, most of all, virtually viceless. The PT-19 truly lived up to its nickname, the Cradle of Heroes. It was one of a handful of primary trainer designs that were the first stop on a cadet’s way to becoming a combat pilot.

Variants PT-19 Initial production variant powered by 175hp L-440-1, 270 built. PT-19 Powered by a 200hp L-440-3 3226 built. PT-19B Instrument training version of the PT-19A, 143 built XPT-23A A PT-19 re-engined with a 220hp R-670-5 radial engine. PT-23 Production radial-engined version, 774 built. PT-23A Instrument training version of the PT-23, 256 built. PT-26 PT-19A variant with enclosed cockpit for the Commonwealth Air Training Scheme, powered by a 200hp L-440-3, 670 built for the Royal Canadian Air Force as the Cornell I. PT-26A As PT-26 but with a 200hp L-440-7 engine, 807 built by Fleet as the Cornell II. PT-26B AS PT-26A with minor changes, 250 built as the Cornell III. Cornell I RCAF designation for the PT-26. Cornell II RCAF designation for the PT-26A. Cornell III RCAF designation for the PT-26B.

Operators: Argentina, Brazil, Canada, Chile, China, Columbia, Ecuador, Haiti, India, Mexico, Nicaragua, Norway, Paraguay, Peru, Philipines, South Africa, Southern Rhodesia, United Kingdom, United States, Uruguay, Venezuela


Laptop Backpack Project

Sew seams together with a 1cm seam allowance, back tacking at each end & trimming off loose threads, unless otherwise indicated.

Pins perpendicular to the seam line can be sewn over.

The ideal sewing machine needle size is heavy duty 100 (16).

Use a hot iron on interfacing and ensure shiny side is against the material WS. You can iron directly onto the matt side of the interfacing.

Sewing lingo

Back tacking = sewing a few stitches backwards at the start and end of a seam to secure the stitch.

Topstitch = a row of stitches sewn on the material RS.

RS = right side of material.

RST = right sides of material together.

WS = wrong side of material.

WST = wrong sides of material together.

Cutting guides

The seam allowances are included in the pattern pieces.

Cotton Canvas:

Iron your material before you cut out the pattern.

The spot pattern on the material is diagonal so align your pattern piece vertically on the material.

Interfacing:

To save time, you can draw around the interfacing outline and then cut it out, instead of pinning on the pieces.

Once you have cut out the interfacing pieces, iron on to the applicable material piece WS (e.g. 1 x B interfacing ironed to 1 x B material WS).

Leave the F (straps) interfacing separate for the time being.

For C (inner pocket), iron the C interfacing piece to the WS bottom half of the pocket material (the short edges are the top & bottom).

To sew your laptop backpack

Outer Pocket (A)

Pin the 2 x outer pocket pieces (A) RST (non interfacing piece on top). Leave a 10cm opening along one edge so you can turn it inside out. Stitch the outer edges, leaving the 10cm gap unsewn. Trim triangles off the seam excess in corners and turn inside out to RS. Iron flat (interfacing side first), including turning in the gap 1cm seam allowance.

Pin the gap closed and then topstitch around entire edge. The side with the interfacing attached will be the front of the pocket and should be on top when topstitching.

TIP: When topstitching, use the right edge of your machine foot as a stitch width guide, unless otherwise instructed.

Along the edge opposite to the opening end, also sew a 1cm seam across. This edge will be the top of your pocket.

Adding wadding to 2 x panels (B)

On the 2 x material panels (B) without interfacing, pin separately WS on top of 2 x wadding (material on top).

Stitch around the panels with the material on top, to secure the wadding to it.

Front inner & outer panels (B)

Take 1 x wadded panel (B) & position the outer pocket (A) on RS 7cm from the top edge in the centre. The shorter 45cm edges on the panel are the top and bottom. The pocket interfacing side should be facing you and the edge with the double seam should also be at the top. Pin the lower and side edges.

Topstitch around the pinned area (go over topstitching already in place), leaving top edge open. Then stitch another row 1cm in on the same sides.

Pin the top edge of this panel RST to an interfaced panel (interfacing on top so the wadding doesn’t catch in your machine). Stitch the pinned, top edge only. Iron seam on RS and put to one side.

Inner Pocket (C & B)

Iron the inner pocket material in half WST over the interfacing. Topstitch along material folded edge on interfacing side, using your machine foot as a stitch width guide again.

Pin the pocket (C) WS (interfacing side is RS) lower and side edges on RS bottom half of 1 x interfaced panel (B).

Stitch around the pinned lower and side edges of the pocket to anchor securely to the panel.

Then mark & stitch 2 x seams on the pocket RS, 6cm in from each side.

Strap adjusters (D), handle (E) & strap connectors (G)

On 2 x straps adjusters (D), iron a 1cm seam WST on one of the short edges. You don’t need to iron a seam on the handle (E) or strap connectors (G). Iron 2 x D, E & G in half lengthways WST.

Open and iron raw edges WST towards centre fold line. Then iron in half lengthways again so that all the pieces are now a quarter size in width (2.5cm).

On all, topstitch around all edges, close to the edge, starting on the long, open edge.

Padded shoulder straps (F, G & buckles)

On the strap (F) material x 2, iron 1cm seams WST on both long edges & 1 short edge. Iron the strap interfacing pieces onto both strap material WS, tucked under the corner seams.

Trim the strap wadding & material to the same size. Place the wadding on the material WS. Fold the strap in half lengthways WST, catching in all the wadding and pin the long edge. Repeat for the other strap.

With the flat, curved edge of the buckle facing up and at the bottom, thread a strap connector (G) through the top 1 st hole from behind and then down through the 2 nd hole from the front. Repeat for the other strap connector and buckle. Fold the strap connector in half and place both raw ends in the centre of the seamed short edges of the strap (F) 1cm in and pin (strap interfacing side and the flat, curved buckle edge on top).

Topstitch around all sides on both straps, close to the edge. Start and end on the raw, short edge, as this will be hidden. Then, starting in the left corner of the non seamed short edge of the strap, diagonally stitch a zigzag down the strap, from side to side and working your way to the bottom. Follow the material’s spotty diagonal pattern.

When you get to the bottom, sew along the stitching already in place on the short edge to the opposite corner and then zigzag stitch back up to the top, on the opposite sides of the previous diagonal stitch and finishing in the right-hand corner. This reinforces the strap.


Attaching the outer wing panel to a B-17 - History

Posted on 02/02/2003 4:43:56 PM PST by NormsRevenge

Space Shuttle Tiles - A little history and some general information with links

Press Release from Lockheed , May 1, 1992

SUNNYVALE, California, May 1, 1992 -- When the Space Shuttle Endeavour rockets into space on its maiden voyage, it will be protected by ceramic tiles manufactured by Lockheed Missiles & Space Company, Inc. of Sunnyvale, California. NASA's entire orbiter fleet -- Columbia, Challenger, Discovery, Atlantis, and now Endeavour -- is protected from the searing heat of reentry by Lockheed's Reusable Surface Insulation. Endeavour will be protected with over 26,000 tiles. Earlier orbiters used as many as 34,000 tiles, but as the knowledge base increased, tiles on surfaces that experienced moderate reentry temperatures, such as the upper fuselage, were eventually replaced with flexible insulating blankets.

As early as 1957, Lockheed began investigating a broad range of insulating materials, including zirconium compoutes. By 1961, work focused on finding a suitable all-silica material. By 1968, the basic shuttle tile material LI-900 (which stands for Lockheed Insulation/9 lbs per cubic foot) was developed and successfully tested during the reentry of NASA's Pacemaker spacecraft where surface temperatures reached 2300ûF.

Space shuttle tiles are made of high-purity amorphous silica fibers (2 to 4 microns in diameter, as long a 1/16th inch) derived from common sand. A water slurry containing silica fibers is frame cast to form soft, porous blocks to which a colloidal silica binder solution is added. The blocks are then dried, sintered at 2300ûF. to develop maximum strength, then quartered and machined to precise dimensions. Machined tiles then go to ovens for baked-on coatings. Tiles for areas of the orbiter that experience reentry heating up to 2300ûF. receive a black borosilicate glass coating. Those for lower temperature areas, from 600û to 1200ûF., are coated with a white silica compound which includes alumina to better reflect the heat of the Sun on-orbit. All tiles are treated with a waterproofing polymer.

An installed square foot of shuttle tile material, reusable for up to 100 missions, cost NASA about $10,000. The ablative heat shields used on Apollo command modules returning astronauts from the Moon were priced at $30,000 per square foot, and were used only once.

Once the shuttle tile production line was running smoothly, Lockheed used independent development funds to develop third generation tile material. Called, HTP, for High Thermal Performance, it surpasses shuttle tile material in strength by a factor of two and one-half, and coupled with the success of Lockheed's Reusable Surface Insulation for the space shuttle fleet, transformed Aerospace Ceramic Systems from a single- contract, single-customer group into a multiple-contract, multiple customer group in the space of a few years. The first non-shuttle contract came from the Lockheed Aeronautical Systems Company, builder of the F117 Stealth Fighter. The material is used for high temperature insulation. Similarly, Northrop turned to Lockheed's Aerospace Ceramic Systems for heat shield parts to be used on the B-2 Stealth Bomber. Between 1989 and 1991, Aerospace Ceramic Systems fulfilled 112 separate contracts. Typically, one new proposal a week now comes out of the office. "In the area of low-density, high- strength rigid fiber ceramics, Lockheed is really the only game in town" exclaims John Donaldson, Lockheed senior staff engineer, "And if you want manned spaceflight qualified rigid fibrous ceramics, you should come to us. As far as we know, nobody else in the industry makes it." In that regard, Lockheed has been approached by General Dynamics in Fort Worth, Texas to submit a bid to build heat shield test parts for the National Aerospace Plane. Structural ceramic composites represent another productive area for Aerospace Ceramic Systems. As silica-based tile material is quite fragile, Lockheed engineers devised a rigid skin to surround the material, thus reducing its fragility. These composites have been used to create missile nosecones and laser- hardened spacecraft antennas.

Lockheed's HTP material is also an outstanding acoustic attenuator, and that characteristic, coupled with excellent heat rejection capability make it ideal for use in the suppression of noise associated with engine exhausts. While modern means of transportation have brought increased mobility to millions, the introduction of noise into the environment remains a persistent concern. Lockheed's Aerospace Ceramic Systems is poised to address that problem.

One challenge for the future will be to produce ceramic insulation that can withstand reentry temperatures for spacecraft returning to Earth from the Moon and Mars. Current material can withstand temperatures of 2300ûF., but 3500ûF. reentry temperatures will not be unusual for astronauts venturing beyond Earth orbit. John Donaldson, and the Aerospace Ceramic Systems team are looking for solutions: "We're looking for exotic ceramic materials that can be made into fibres, and then we'll turn them into low density products. We'll figure it out. We always have."

THERMAL PROTECTION SYSTEM

The thermal protection system consists of various materials applied externally to the outer structural skin of the orbiter to maintain the skin within acceptable temperatures, primarily during the entry phase of the mission. The orbiter's outer structural skin is constructed primarily of aluminum and graphite epoxy.

During entry, the TPS materials protect the orbiter outer skin from temperatures above 350 F. In addition, they are reusable for 100 missions with refurbishment and maintenance. These materials perform in temperature ranges from minus 250 F in the cold soak of space to entry temperatures that reach nearly 3,000 F. The TPS also sustains the forces induced by deflections of the orbiter airframe as it responds to the various external environments. Because the thermal protection system is installed on the outside of the orbiter skin, it establishes the aerodynamics over the vehicle in addition to acting as the heat sink.

Orbiter interior temperatures also are controlled by internal insulation, heaters and purging techniques in the various phases of the mission.

The TPS is a passive system consisting of materials selected for stability at high temperatures and weight efficiency. These materials are as follows:

1. Reinforced carbon-carbon is used on the wing leading edges the nose cap, including an area immediately aft of the nose cap on the lower surface (chine panel) and the immediate area around the forward orbiter/external tank structural attachment. RCC protects areas where temperatures exceed 2,300 F during entry.

2. Black high-temperature reusable surface insulation tiles are used in areas on the upper forward fuselage, including around the forward fuselage windows the entire underside of the vehicle where RCC is not used portions of the orbital maneuvering system and reaction control system pods the leading and trailing edges of the vertical stabilizer wing glove areas elevon trailing edges adjacent to the RCC on the upper wing surface the base heat shield the interface with wing leading edge RCC and the upper body flap surface. The HRSI tiles protect areas where temperatures are below 2,300 F. These tiles have a black surface coating necessary for entry emittance.

3. Black tiles called fibrous refractory composite insulation were developed later in the thermal protection system program. FRCI tiles replace some of the HRSI tiles in selected areas of the orbiter.

4. Low-temperature reusable surface insulation white tiles are used in selected areas of the forward, mid-, and aft fuselages vertical tail upper wing and OMS/RCS pods. These tiles protect areas where temperatures are below 1,200 F. These tiles have a white surface coating to provide better thermal characteristics on orbit.

5. After the initial delivery of Columbia from Rockwell International's Palmdale assembly facility, an advanced flexible reusable surface insulation was developed. This material consists of sewn composite quilted fabric insulation batting between two layers of white fabric that are sewn together to form a quilted blanket. AFRSI was used on Discovery and Atlantis to replace the vast majority of the LRSI tiles. Following its seventh flight, Columbia also was modified to replace most of the LRSI tiles with AFRSI. The AFRSI blankets provide improved producibility and durability, reduced fabrication and installation time and costs, and a weight reduction over that of the LRSI tiles. The AFRSI blankets protect areas where temperatures are below 1,200 F.

6. White blankets made of coated Nomex felt reusable surface insulation are used on the upper payload bay doors, portions of the midfuselage and aft fuselage sides, portions of the upper wing surface and a portion of the OMS/RCS pods. The FRSI blankets protect areas where temperatures are below 700 F.

7. Additional materials are used in other special areas. These materials are thermal panes for the windows metal for the forward reaction control system fairings and elevon seal panels on the upper wing to elevon interface a combination of white- and black-pigmented silica cloth for thermal barriers and gap fillers around operable penetrations, such as main and nose landing gear doors, egress and ingress flight crew side hatch, umbilical doors, elevon cove, forward RCS, RCS thrusters, midfuselage vent doors, payload bay doors, rudder/speed brake, OMS/RCS pods and gaps between TPS tiles in high differential pressure areas and room-temperature vulcanizing material for the thick aluminum T-0 umbilicals on the sides of the orbiter aft fuselage.

REINFORCED CARBON-CARBON

RCC fabrication begins with a rayon cloth graphitized and impregnated with a phenolic resin. This impregnated cloth is layed up as a laminate and cured in an autoclave. After being cured, the laminate is pyrolized to convert the resin to carbon. This is then impregnated with furfural alcohol in a vacuum chamber, then cured and pyrolized again to convert the furfural alcohol to carbon. This process is repeated three times until the desired carbon-carbon properties are achieved.

To provide oxidation resistance for reuse capability, the outer layers of the RCC are converted to silicon carbide. The RCC is packed in a retort with a dry pack material made up of a mixture of alumina, silicon and silicon carbide. The retort is placed in a furnace, and the coating conversion process takes place in argon with a stepped-time-temperature cycle up to 3,200 F. A diffusion reaction occurs between the dry pack and carbon-carbon in which the outer layers of the carbon-carbon are converted to silicon carbide (whitish-gray color) with no thickness increase. It is this silicon-carbide coating that protects the carbon-carbon from oxidation. The silicon-carbide coating develops surface cracks caused by differential thermal expansion mismatch, requiring further oxidation resistance. That is provided by impregnation of a coated RCC part with tetraethyl orthosilicate. The part is then sealed with a glossy overcoat. The RCC laminate is superior to a sandwich design because it is light in weight and rugged and it promotes internal cross-radiation from the hot stagnation region to cooler areas, thus reducing stagnation temperatures and thermal gradients around the leading edge. The operating range of RCC is from minus 250 F to about 3,000 F. The RCC is highly resistant to fatigue loading that is experienced during ascent and entry.

The RCC panels are mechanically attached to the wing with a series of floating joints to reduce loading on the panels caused by wing deflections. The seal between each wing leading edge panel is referred to as a T-seal. The T-seals allow for lateral motion and thermal expansion differences between the RCC and the orbiter wing. In addition, they prevent the direct flow of hot boundary layer gases into the wing leading edge cavity during entry. The T-seals are constructed of RCC.

Since carbon is a good thermal conductor, the adjacent aluminum and the metallic attachments must be protected from exceeding temperature limits by internal insulation. Inconel 718 and A-286 fittings are bolted to flanges on the RCC components and are attached to the aluminum wing spars and nose bulkhead. Inconel-covered cerachrome insulation protects the metallic attach fittings and spar from the heat radiated from the inside surface of the RCC wing panels.

The nose cap thermal insulation ues a blanket made from ceramic fibers and filled with silica fibers. HRSI or FRCI tiles are used to protect the forward fuselage from the heat radiated from the hot inside surface of the RCC.

During flight operations, damage has occurred in the area between the RCC nose cap and the nose landing gear doors from impact during ascent and excess heat during entry. The HRSI tiles in this area are to be replaced with RCC.

In the immediate area surrounding the forward orbiter/ET attach point, an AB312 ceramic cloth blanket is placed on the forward fuselage. RCC is placed over the blanket and is attached by metal standoffs for additional protection from the forward orbiter/ET attach point pyrotechnics.

HIGH-TEMPERATURE REUSABLE SURFACE INSULATION TILES

The HRSI tiles are made of a low-density, high-purity silica 99.8-percent amorphous fiber (fibers derived from common sand, 1 to 2 mils thick) insulation that is made rigid by ceramic bonding. Because 90 percent of the tile is void and the remaining 10 percent is material, the tile weighs approximately 9 pounds per cubic foot. A slurry containing fibers mixed with water is frame-cast to form soft, porous blocks to which a collodial silica binder solution is added. When it is sintered, a rigid block is produced that is cut into quarters and then machined to the precise dimensions required for individual tiles.

HRSI tiles vary in thickness from 1 inch to 5 inches. The variable thickness is determined by the heat load encountered during entry. Generally, the HRSI tiles are thicker at the forward areas of the orbiter and thinner toward the aft end. Except for closeout areas, the HRSI tiles are nominally 6- by 6-inch squares. The HRSI tiles vary in sizes and shapes in the closeout areas on the orbiter. The HRSI tiles withstand on-orbit cold soak conditions, repeated heating and cooling thermal shock and extreme acoustic environments (165 decibels) at launch.

For example, an HRSI tile taken from a 2,300 F oven can be immersed in cold water without damage. Surface heat dissipates so quickly that an uncoated tile can be held by its edges with an ungloved hand seconds after removal from the oven while its interior still glows red.

The HRSI tiles are coated on the top and sides with a mixture of powdered tetrasilicide and borosilicate glass with a liquid carrier. This material is sprayed on the tile to coating thicknesses of 16 to 18 mils. The coated tiles then are placed in an oven and heated to a temperature of 2,300 F. This results in a black, waterproof glossy coating that has a surface emittance of 0.85 and a solar absorptance of about 0.85. After the ceramic coating heating process, the remaining silica fibers are treated with a silicon resin to provide bulk waterproofing.

Note that the tiles cannot withstand airframe load deformation therefore, stress isolation is necessary between the tiles and the orbiter structure. This isolation is provided by a strain isolation pad. SIPs isolate the tiles from the orbiter's structural deflections, expansions and acoustic excitation, thereby preventing stress failure in the tiles. The SIPs are thermal isolators made of Nomex felt material supplied in thicknesses of 0.090, 0.115 or 0.160 inch. SIPs are bonded to the tiles, and the SIP and tile assembly is bonded to the orbiter structure by an RTV process.

Nomex felt is a basic aramid fiber. The fibers are 2 deniers in fineness, 3 inches long and crimped. They are loaded into a carding machine that untangles the clumps of fibers and combs them to make a tenuous mass of lengthwise-oriented, relatively parallel fibers called a web. The cross-lapped web is fed into a loom, where it is lightly needled into a batt. Generally, two such batts are placed face-to-face and needled together to form felt. The felt then is subjected to a multineedle pass process until the desired strength is reached. The needled felt is calendered to stabilize at a thickness of 0.16 inch to 0.40 inch by passing through heated rollers at selected pressures. The calendered material is heat-set at approximately 500 F to thermally stabilize the felt.

The RTV silicon adhesive is applied to the orbiter surface in a layer approximately 0.008 inch thick. The very thin bond line reduces weight and minimizes the thermal expansion at temperatures of 500 F during entry and temperatures below minus 170 F on orbit. The tile/SIP bond is cured at room temperature under pressure applied by vacuum bags.

  • Concept of reusable space transportation system originated in the 1960's
  • Development of shuttle system begun in 1970's
  • Major components contracted to various companies

  • IBM -- computers
  • Morton Thiokol -- solid rocket boosters (SRB's)
  • Rockwell -- orbiter vehicle (OV)
  • Martin-Marietta -- external tank (ET)
  • General Electric -- kitchen and toilet
  • Not flight-qualified
  • Test vehicle for landing checkout only
  • Now at Dulles Airport near Washington, DC

    The Launch Assembly (Stack)

  • Orbiter (crew, payloads, main engines)
  • ET (liquid hydrogen and liquid oxygen for main engines in orbiter)
  • SRBs (reusable solid chemical engines)
  • Previous s/c (Mercury, Gemini, Apollo) employed ablative heat shields. During atmospheric re-entry,, a layer of glass-phenolic material chars as it reaches high temperatures, and the hot particles are sheared away by the high-velocity air flow -- this is the ablation process. The hot particles carry the heat away from the s/c. Major disadvantages are weight of the shield and non-reusability (since a new shield cannot be easily bonded to the s/c).
  • Shuttle orbiters use a system of 30,000 tiles made of a silica compound that does not ablate, but does rapidly radiate heat away from the orbiter. These tiles can be repaired in space. Major disadvantages are fragility (tiles easily damaged before launch and by orbital debris -- lots of tile damage due to debris since anti-satellite tests in mid-80's) and complexity (many people needed to manually attach tiles to orbiter in a tedious and time-consuming process, and to inspect them all before launch).

A meteor moving through the vacuum of space typically travels at speeds reaching tens of thousands of miles per hour. When the meteor hits the atmosphere, the air in front of it compresses incredibly quickly. When a gas is compressed, its temperature rises. This causes the meteor to heat up so much that it glows. The air burns the meteor until there is nothing left. Re-entry temperatures can reach as high as 3,000 degrees F (1,650 degrees C)!

    Aerobraking tiles are produced from amorphous silica fibers which are pressed and sintered, with the resulting tile having as much as 93% porosity (i.e., very lightweight) and low thermal expansion, low thermal conductivity (e.g., the well known pictures of someone holding a Space Shuttle tile by the corners when the center is red hot), and good thermal shock properties. This process can be readily performed in space when we can produce silica of the required purity.

These tiles keep the heat of re-entry from ever reaching the body of the shuttle.

These links will help you learn more:

I can only post on Geocities and have little bandwidth to post, so perhaps someone can post it for me.

I inverted the photo on my computer and the writing reads:
V070-1911
-076 (or G) MN00

With these numbers, the tile should be traced to its exact location. It came from Kerens, Texas, 65 miles SE of Dallas and another tile is in Rice, Texas, 45 miles S of Dallas on I-45. If these tile came from under the left wing, that would place its failure at the top of the debris field.


Irwin Thompson / DMN

The tiles themselves would scare you. intuitively, they look insubstantial and too much like styrofoam. Kind of crumbly and brittle and unlike much of anything you'd trust. Amazing stuff.

Reentry sounds a lot like a kiln. Regular porcelain liquifies before hardening.

Would it be possible to coordinate launch schedules with the Russians so that they would have a Soyuz 24 hours or less from launchability when we do a shuttle mission, with the ability to retarget to the Shuttle's orbit should the need arise (with us possibly providing some reciprocal services)?

To be sure, the Soyuz would probably only be able to remove two of the astronauts, but it could also supply life-support supplies as well as such repair supplies as were determined to be necessary.

The most critical tiles are on the underbody of the shuttle. Those are not very likely to be either damaged or suspect, tho' they are replaced after missions frequently in small numbers and in a routine manner. But to look at them , "This is gonna get me home?".

Space Flight is the ultimate act of faith. but you better believe in your vehicle.

Anyway, just a throwaway, an idle curiosity. Did you know that there are ceramic knives far harder and sharper than the best steel?

He created a substance that which was in a liquid form, but could be poured into a mold and allowed to set as a solid. In either form it would not retain heat.

Since then I have never heard anymore about this and I often wonder what happened to the guy.

Yes, I heard of the ceramic knife not too long ago. Strange, but heck, the cavemen and native americans used certain rocks to make some pretty sharp cutting devices as well. Maybe, we are finally catching up technology-wise our ancient ancestors.

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.


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Going All-Out With A Classic Balsa B-17-F – Part 8

I finished our last session of B-17 building by closing-up/sheeting-in the forward section of one of the one of the engine nacelles. I’ve been doing nacelles for quite a while now and I’m sure it has occurred to you (as it did to me when I was planning the project) that four nacelles …all of them slightly different…are going to demand not just some seriously skilled balsa work, but also a lot of patience.That last part is the key to getting it right. As I’m about to show you, as very often happens with building model airplanes, not everything connected with doing nacelles came out exactly right on the first try. One of the lessons I want to share this time around is how to go back and get it right when whatever it is that’s getting built at the moment falls short of your expectations. Being able to apply that lesson, along with a generous shot of that patience (as in, “No, I don’t have to finish closing all four nacelles today!”) is one of the secrets to doing the sort of model building people talk about. Once all the sheet balsa nacelle skins are in place, I’ll go on to fill in some more of the shape that will go a long way to defining the character of the B-17. When I close the shop door this time around there’s still going to be a healthy dose of nacelle building left…but…it’s going to get easier to squint a little into the shadows in the corners and imagine four R-1820 radials chuffing and rumbling into life one after the other. Let’s cut some balsa…

B-17-8-1 Last time I started with the front of the left/outboard (No. 1) nacelle…now I’m working on the right/inboard (No. 3). This is where the get-it-right part begins. In a perfect world, the ring-shaped joining surface created by the open edge of the 1/16” balsa sheet skin where it attached to the N-1 formers at the wing leading edge would be exactly circular and lie neatly in the single vertical plane defined by the N-1’s. If that were the case I’d be able to cut a single piece of 1/16” balsa sheet (with the grain running front-to-back for easy bending) that would wrap a full 360 degrees around the structure and close it. In this real-world project there are going to be imperfections…bumps and wiggles…that will require corrective adjustments (trimming) to the front skin material to allow me to make a neatly fitted, closed joint all the way around the nacelle circumference. By making this front skin in four quarter-circle (90 degree) segments I can make those adjustments easier to manage. Here I’m starting by marking a piece of 1/16” balsa sheet wide enough to cover ¼ of the nacelle circumference and long enough to provide some extra margin for trimming at the front and/or rear.

B-17-8-2 Cutting the first of the four front skin panels I’ll need for this nacelle from a stock 1/16” x 3” x 36” balsa sheet is just the usual straightedge-and-razor blade job.

B-17-8-3 Because I have planned for extra length/overhang it’s not necessary to measure each panel individually to get an exact measurement…I’m using the first one as a pattern to mark off the rest.

B-17-8-4 Here’s the front cowl skin ready for some careful cutting and fitting into an accurate assembly.

B-17-8-5 Here’s the first of those inaccuracies (errors) that are going to need fixing. Clearly one edge of the new skin panel must be centered on that 3/32” sq. stringer, so I’ll have a joining surface/gluing base for the one that will fit next to it. BUT…can you see where, for whatever reason, I have allowed the joining edges of the rear skin panels to end up out of line with the stringer? What’s more, the rear panel edges don’t line up. What’s the best way to correct all the misalignment to get an accurate finished nacelle surface?

B-17-8-6 Look very closely at the joining edges as I hold the new panel in place. I used the sharp corner of a sanding block to trim a shallow notch into the corner of the front sheet to achieve the fit you see here. This is easier than trying to cut and chisel away extra material on the old glue line over the N-1 former.

B-17-8-7 This is the same panel as seen from the other side…the trimmed joining edge we just looked at is at the top where I’m holding it firmly in place with my thumb. Before positioning this panel I made the pencil mark that’s on the left of the seam to reference the centerline of the side 3/32” sq. stringer I’ll use as a joining base. With the skin panel temporarily bent into place I then made the pencil mark on the right side to provide a reference for cutting off the excess panel width so the finished edge will line up with the stringer.

B-17-8-8 I marked the front edge at the stringer centerline, too. The result looks like this.

B-17-8-9 The narrow cut-off piece of balsa is the portion that would have extended beyond/over the stringer centerline.

B-17-8-10 When I test-fit the trimmed skin panel it looks like this.

B-17-8-11 As with all the other assemblies on this airplane that require panels of sheet balsa to bend to fit a curved structure, I’m spraying what will be the outer face of this one with water. If you look carefully you can see that the 1/16” balsa sheet has already started to assume a curve away from the moistened surface.

B-17-8-12 This is a classic example of “open joint assembly”. I have to put adhesive on ALL the structural surfaces (stringers, formers, etc.) that will contact the panel I’m attaching before I fit it into place. Traditional aliphatic resin (or even old-time model airplane cement) would do the job here by remaining wet long enough for me to fit the assembly together and hold (clamp) all of it in place long enough for the adhesive to harden…for an assembly like this I would normally use masking tape to avoid poking holes or otherwise marring the sheet panel with pins. This is where Deluxe Materials Roket Rapid is just what I need. Once the joining surfaces are closed (pressed together) under gentle pressure the adhesive will take hold (“grab”) within a minute or so. That’s a reasonable length of time for me to hold everything in place with my hand. When “handholding” is tthe better choice and when you should rely on tape, clamps, or whatever to do that job for you will always be a judgment call on your part as an aeromodeling craftsman. Watch how it works here…I’ll begin by laying a smooth, full bead of Roket Rapid along each of the surfaces to be joined, even the little narrow ones.

B-17-8-13 The Roket Rapid easily stays “wet” for the minute or two it takes me apply it to every part of this complex joint and then allows me time to accurately align the panel along the top stringer. Remember that since I’ve already double-checked the fit, lining up this part of the joint ensures that all the other edges will fit as well.

B-17-8-14 With that done I can wrap/roll the rest of the panel around and into contact with the pre-glued nacelle structure…

B-17-8-15 …and HOLD it there by hand for the minute or so it takes the Roket Rapid in the now-closed joint to grab and take over the job of holding. I could have used a masking tape wrap to do the job, but this is a good example of a case where using cyanoacrylate allows me to make a strong, accurate joint in less time.

B-17-8-16 This is the same panel/assembly seen from a different angle.

B-17-8-17 Remember what I said about opportunities for less-than-perfect joints that may jump out to surprise you? Look carefully…the upper edge of the new 1/16” balsa sheet panel is aligned exactly along the top stringer, ready to form a perfect joint with the panel that’s already in place. The square-cornered panel doesn’t fit. What’s going on? For whatever reason I’ve permitted an alignment error to creep into the N-1 formers as they align with the wing leading edge. What should I do? Having this particular skin panel joint cut at a corrective angle will not compromise structural strength, nor will it show after I’ve finished skinning the nacelle and done some careful sanding, so…

B-17-8-18 …I’m going to adjust (trim) the panel edge to cancel out the error. I’m measuring the width of the gap that’s defined by the misalignment…

B-17-8-19 …and transferring that measurement to the panel.

B-17-8-20 That allows me to mark a reference line that I’ll use to cut off the extra 1/16” balsa sheet that’s getting in then way of a proper fit.

B-17-8-21 This happens a lot. I trimmed off almost, but not quite, enough balsa. Off camera, I repeated the measure, mark and cut operation.

B-17-8-22 On the second try it fit the way it’s supposed to. If you check back over the last several steps you’ll see where I left plenty of extra length on these panels in case this kind of trimming became necessary.

B-17-8-23 All things considered, it’s a good idea to check again that everything fits. Remember that I’m allowing the overhang on the front to remain there for now.

B-17-8-24 You couldn’t see it, but I found a little “wide spot” along the top/joining edge of this panel, so I used my 100-grit sanding block to “feather off” a tiny adjustment that would have been too delicate to get right with a razor blade and straightedge.

B-17-8-25 Now I can get out the Deluxe Materials Roket Rapid again and start gluing-up this panel assembly just as I did the last one.

B-17-8-26 As before, I’m relying on calibrated finger pressure to clamp the multiple gluing surfaces of this complex joint long enough for the Roket Rapid to grab.

B-17-8-27 Now I’m moving on to the adjoining nacelle…the right inboard…and going through the same process of fitting the new panel piece to the existing structure.

B-17-8-28 As before, I measure-and-trim-and-check until I have a fitted joint I won’t need to hide.

B-17-8-29 Here I have moved on to yet the next nacelle…more of the same until I have them all the way I want them.

B-17-8-30 THAT looks like this. Here it’s easy to see all that extra 1/16” balsa sheet I left overhanging the sub-firewall (front) N-1’s in case I needed it for trimming and fitting.

B-17-8-31 Now I can trim away all that extra sheet balsa. I’m rough-cutting the assembly to shape using a SHARP razor blade and a slicing motion.

B-17-8-32 The 80-grit sanding block makes an easy job of blending all those protruding edges into the surface defined by the N-1’s so smoothly that I can’t feel a discontinuity.

B-17-8-33 Here’s a dry fit of one of the laser cut plywood firewalls directly out of the kit box. Before I can glue these in place I have to finalize any decisions regarding the motor mounts and mark/cut/drill any openings I might want to make in the firewalls while I still have them “loose” and fully accessible to work on.

B-17-8-34 Another sign of things to come…this is one of the aft-nacelle fairing blocks that I’ll be cutting from ¾” balsa sheet and attaching to the top and bottom of each nacelle rear-end in turn. There will be a LOT of trimming and fitting and sanding involved here, so I’m going to put off working on those details until next time to assure having plenty of space to explain it all.


Then do it all again for the other wing

Including making all the ribs, it took me eight months to finish the left wing panel. The right wing took about four months. The wing center section required another three months, mainly because I made some changes off the plans, including moving the fuel tank from the center section to the fuselage, and cutting out a semi-circular area in the trailing edge of the center section to make it easier to get into and out of the rear cockpit.

People who stop by to check on my progress have remarked that the Pietenpol wing really goes together like a big balsa wood model, and they are right. Much of the design, from the built-up ribs to the double spruce spars, looks like a scaled-up model. I built a few flying, or sort-of flying, models in my youth. Based on the performance of some of those models, I’m not sure whether that thought makes me feel comfortable or nervous. Knowing that my rear end will be flying in this big model makes me a lot more thorough than I might have been with the balsa and tissue models from 30 years ago.


Watch the video: Farm Girl Installing Running Boards. Side Steps on 2019 Ram 1500 (September 2022).


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