Nose rib assembly Jig

Unless you have 3 hands or an assistant, you'll need a nose rib assembly jig.  See photo 1.  The jig is simply two pieces of 1 inch spruce band sawed to the shape shown and screwed together at right angles.

The jig is clamped to the wing spar at the nose rib position and the nose rib is then clamped to the upright portion of the jig.  See Photo 2.  Once the nose rib is clamped in position it's an easy matter to nail the rib in place.  I use a spring clamp on the wing spar and a small "C" clamp on the rib.  Check the rib angle to the spar with a small square before nailing.

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Wing Assembly Jig

You can , of course, assemble the wing on saw horses. However there are two major problems with the saw horse method: (1) a horizontal wing takes up a lot of floor space, 5X16=80 square feet.  Plus room to walk around all sides, doesn't leave much room in a small shop for other important things like the fuselage and tools. And (2) you can't reach both sides of the wing unless you're willing to turn it over very often.

I use saw horses to begin the assembly:  attach wing spars to the compression struts, thread in the drag wires and trammel the assembly. I modify the saw horses by adding 6 inch "lifts" to them to bring their tops up to a more comfortable, work bench like, height.  Photo 1.

But for the remainder of the assembly, nose ribs, trailing ribs, leading edge, etc., it's much easier to use a vertical jig.  I can get at all sides of the wing easily, and the whole thing takes up less than 20 square feet.  I use a couple C clamps to secure the wing to the vertical jig.  Photo 2.

I made my jig out of 2X4's bolted to the rafters and standing on the cement floor.  Another 4 foot long 2X4 is bolted to the upright member and to the wall of the shop.  This gives me a 4 foot space to work behind the wing and makes the jig nicely rigid.  Photo 3 is a drawing of the jig.

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Wing 10: Trammel

Trammel the wing to ensure compression struts are perfectly perpendicular to the spars.  Trammelling means that you measure the diagonals that the drag wires form in each wing bay.   In other words, you'll measure the "X" s made by the drag wires and adjust the wires until both arms of the "X" are the same.

The wires in each bay are adjusted to the same length.  But then the trammel bar is reset for the next bay and the wires in that bay are adjusted independently.  One bay at a time.

Before you start, while the wires are loose, wrap each wire with about 1 inch of vinyl electrical tape where the wires cross.  This will reduce the chafeing of the wires and cut any noise they would produce rubbing together.  Don"t tape the wires together as you want them independently able to move when you rig in the wing wash out later.  Photo 1.

I suppose you could trammel the wings with a tape measure, but the actual length of the drag wires is unimportant...what you want is just for the lengths to be the same.  A trammel bar a quick, handy way to do it.  If you can, barrow one for a few hours.  Otherwise, it's easy to make your own out of scrap steel and a bolt.  Mine is a 6 foot length of 3/8 steel rod, with a one inch length of  3/8 ID tube slipped over and a AN3 bolt and nut make the adjuster.  I used some scrap 1/8 inch rod to make the pointers and welded it together. Photo 3.

Start at the root end of the wing and work toward the wingtip.  Adjust the wires in one bay until the trammel bar says they are identical length, then move on to the next bay and do the same.  After you've trammelled the entire wing, go back and double check...you'll probably have to do some minor adjustment.  Photo 2

When you get done the wires should all have approximately the same tension and give a nice TWANG when you pluck them.  Use a very short wrench to keep from getting the wires too tight.  I made my own out of a 1/2 by 1/8 by 3 inch long piece of steel.  I simply hack sawed a slot in the end.  Photo 4

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Wing 9: Drag wires

Drag wires (and anti-drag wires) hold the compression struts in the interior of the wing.  They form an "X" between compression struts and resist fore and aft motion of the wing.  In other words, drag wires resist the force that drag produces on the wing, the force that would make the wing fold up against the side of the fuselage.

Drag wires look like giant bicycle wheel spokes, they are more like thin steel rods with threads on their ends.  The threads screw into drag wire fittings in the end of the compression struts.  See photo 1.  The fitting opposite the camera has a drag wire screwed into it, the one closest to the camera is ready to receive it's anti-drag wire.  Be sure to secure the drag wire fittings with little pieces of black tape, as shown here.  Don't remove the tape until you're ready to screw in a wire, otherwise the fitting can fall back into the compression strut end and it'll make your curse when you have to take it apart to get the fitting back out.

Screw one end of the drag wire into a fitting until it meets the lock nut.  Photo 2.

Put a drop of Marvel Mystery Oil (MMO) onto each wire end thread before attaching it to the fitting.  Photo 3. hold a paper towel under so you don't drip oil on the floor or your beautiful, restored wing.

To get the other end of the drag wire into its fitting you'll have to bend a modest arc in the wire.  Don't worry, it'll pop right back straight.  Photo 4.

Very important.  Install the drag wires on top of the anti-drag wires.  The drag wires resist the motion of the wing toward the tail of the airplane, anti-drag wires resist wing motion toward the nose.  Drag wires have to be on top so that later when you rig your aircraft you can rig wash out into the wing.

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Wood

I wanted to recycle the old wing spars...lots of great old spruce in them.  I decided to use them to make new cabin door frameing.  The problem is that the old spars are 3/4 and 5/8 thickness...and the cabin frameing is 1/2. 

I set up my band saw to re-saw the old spars down to 1/2 thick.  I used a 1/2 inch, 6 tooth per inch blade and a home-made fence.  And a slow, slow feed.  Checking the resulting boards with a dial caliper I found the blade wandered about .030 (the boards were about .530 to .560 thick).  Photo 1.

I used a hand plane to remove the high spots and then I went to work with a belt sander.  I used an old Sears belt sander mounted upside down on a plywood base.  Photo 2.  After planeing and sanding my boards were nice and smooth and  running .510 to .530 thick...close enough.

Tom Baker was kind enough to lend me his old door frame boards (original!) to use as patterns.  So I just traced around Tom's frames and then back to the band saw to cut them out.  Photo 3.

The cabin wood frameing turned out beautiful.  It all looks like new, but with that mellow 60 year old patina.  Photo 4.  I set the wood pieces aside for varnish and fitting with the stringers later.  AND I still have plenty of old spruce left in those old spars!

Link to Stringers

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Wing 8. Reinforcement Plates

Photo shows router setup to mill butt end of spar for plywood reinforcement

The 1/16th inch plywood reinforcement plates must be flush with the surface of the spar, so the spar is milled down 1/16 inch on both sides.  I used an ordinary router.  First I set up a stop made of two 1x2's clamped to the spar.  The base of the router contacts the 1x2 stop and makes a nice even square end to the milled down portion of the spar.  I used a 3/4 inch diameter flat bottom router bit set to 1/16 depth.   It took several adjust and try cycles before I got the depth just right.

Cutting the recess is a matter of moving the router left and right across the surface of the spar.  Keep the router level by keeping the router base flat on the uncut portion of the spar.  Go slow, no hurry.  Chew gum, listen to music, stay loose.  You want the cut portion of the spar to be as smooth as possible.

After milling with the router, dress the cut with sandpaper until the router marks disappear.

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The Wing 7 Rib installation

Photo: Ribs being installed, note yellow string lines

Ribs are nailed to the wood spars with tiny cement coated aircraft nails. 

Install the rib closest to the butt end of the wing first.  Then install the full rib closest to the tip next.  Installing these two ribs first allows you to tie a couple masons strings between the butt and tip to use for aligning the remaining ribs.  The ribs are a snug fit fore and aft but are able to move vertically, so the string lines are needed to ensure accurate vertical alignment.

Aircraft nails are so small that it's difficult to hold them.  If you attempt to hold them with your fingers you end up smashing the fingers with the hammer everytime.  There are two ways around this problem: (1) you can hold the tiny nail with a needle nose pliers while you tap it with a tack hammer, or (2) my favotite method is to place the little nail head on the magnetic end of the tack hammer, place the nail point where you want it and then tap the tack hammer with a big ball peen hammer...the nail sets into the wood about half way with that one blow.  Finish setting the little nails the last 1/4 inch with an ordinary nail set. 

Be sure the ribs just touch the string line and use a square to ensure the ribs are vertical and perpendicular to the spars.

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