Imperial Fuel Valves

There are better, more modern valves than the old Imperials, but the new valves are expensive and they're not ORIGINAL so let's take a few minutes to fix up our old fuel valves.  There are three major problems with the Imperial valves: (1) they can "sieze" or lock up so you cannot turn the fuel on OR off  (2) they can leak in the Off position so that fuel runs through when you don't want it, resulting in a dripping carb or overflowing main tank and (3) most annoying of all is a leak around the stem which results in fuel dripping INSIDE the cockpit!

It doesn't take long to spruce up this old girls...take them apart by removing the handle and unscrewing the top, pull out the stem and spring.  There's a half round washer that will tip up when you pull on the stem.  It has a tab on the back side so you have to pull the tab out of its notch to get the washer free.  Clean everything using a toothbrush and MEK

Next you'll "lap" the stem into the tapered body of the valve.  There are special lapping compounds available, but most folks use toothpaste (a nice smelling mild abrasive).  Coat the stem with toothpaste (Photo 2) and then put it back into the valve body.  Use the handle to turn the stem back and forth in the body as if you're turning the valve on and off.  Do that a hundred times or more and the toothpaste will start to wear the stem and body so that they match perfectly.  Remove the stem and you can tell the lapping is working because the toothpaste has turned black.  Wash off the toothpaste to check lapping progress.  You're done lapping when the stem and body look nice and shiney.  Photo 3 shows a comparison of before and after lapping the stem.

Finally, re-assemble the valve using a new seal and fuel lube grease.  Newer (!?) Imperial valves use O-ring seals, just put a new one on.  But the older valves used leather seals which are no longer available.  I haven't tried this but people tell me you can use waxed dental floss or teflon string wrapped around the stem to replace the leather seals.

Engine primer

Not much to overhauling the engine primer, but you'll need to have on hand two O-rings of the correct size (Kohler takes a -12 O-ring) and a very small amount of fuel lube grease (EZ Turn).

First, unscrew the locknut and pull the plunger out of the barrell (Photo 1).  Remove the old O-rings from the plunger...they may just fall off if they're more than 15 years old.  Examine the inside of the barrell for any dirt, crud, or scratches.

Apply a light coat of special grease to the new O-rings and to the end of the plunger (Photo 2)  Roll one O-ring into the first groove, the roll the second O-ring over the first and into the second groove.

Finally, grease the plunger and barrell good and reassemble.  (Photo 4) Test the unit.  If there's any problems, remove the check valve springs and balls (under the two screw covers on the end of the primer) and clean and lube them.

Fuel system test rig

Easy to make (and cheap) test rig for fuel systems.  Use it to test valves, fuel line connections, gascolator, carburetor float level, etc.  Consists of:

(Photo 1)  1 1/4 to 3/4 reducer coupling...makes the reservoir for the test fuel.  Wrap a piece of safety wire around it so you can hang it up.  Needs at least 19 inch "head" above the item being leak tested.

3/4 to 3/8 bushing to step down to the hose barb

3/8 pipe to 3/8 hose barb

4 feet or so of 3/8 inside diameter vinyl hose

(Photo 2), two more 3/8 pipe to 3/8 hose barbs

3/8 ball type valve, and

another 2 feet or so of that 3/8 ID hose

and a few hose clamps, total cost about $10

To use your tester hang it at least 19" above your work bench and attach the loose end to the valve or whatever you're testing.  Fill the reservoir with fuel or even with water (I use E85 because of its low density and distinctive fruity smell).  Open the hosevalve and wait...if no leaks appear, wait overnight then give it the smell test (if using water place a piece of paper under your test item and see if its damp in the morning).  Of course if you use fuel to test your fuel system components, you should test outdoors and away from any ignition source!

Rivet tools

There's not all that much sheet metal work involved in restoring a classic airplane, but there is always some minor repair work that needs to be done, so you need basic rivet tools.

A modest rivet gun (a TP83) is shown in Photo 1.  In addition to the rivet gun you need rivet sets.  I have three: a 1/8" set, a 3/32" set and a flush set.  The flush set needs a different type of retainer, so you need two retainers: a beehive retainer and a quick change type. 

Of course you need a bucking bar.  There are dozens of different styles and you can even make your own.  But I have only ever needed one, a #647.  The 647 seems about the right size for general use and the small end will even buck the hard-to-get-at rivets on Taylorcraft wing ribs.

Photo 2 shows some nice to have (some would say required) items for riveting.  The air drill is one of my favorite tools, I got it for $10 on eBay.  It's old and its castings are worn smooth from years of use, but it still works great and I love the high pitched whine it makes. 

Next to the drill is a rivet cutter.  With one of these you can buy a batch of long rivets and cut them to length as needed.

Also handy is an assortment of cleco fasteners.  I have 8 each of 1/8" and 3/32" clecos.  Some folks who build aluminum planes buy hundreds of clecos and wish they had more, but I've never needed more than 8.  You'll need a cheap cleco pliers to install and remove the clecos.

Finally in the photo is a little bottle of Marvel Mystery Air Tool Oil.  I put 3 or 4 drops of oil in the air inlet of my air drill and rivet gun every time before I use them.

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Fiberglass Layup

All the materials and tools needed for a fiberglass layup are readily available at your friendly local WalMart.  Get:

      1. Fiberglass resin and fiberglass cloth and a can of car wax in the automotive department

      2. A couple of 2 inch chip brushes and a quart of acetone in the paint department

First, give the mold a couple coats of wax.  Car wax is not the very best mold release available, but it works fine and it's cheap.  Photo 1

Next, rough cut two pieces of glass cloth at least 1/2 inch larger all around than necessary to fill the mold cavity.  Use cheap sissors to cut the cloth.  Mix about 1/8 of a quart of resin with about 1/8 of the small tube of catalyst that comes with the resin.  While it's not necessay to be terribly accurate in your mixing ratio, it's a good idea to use a ruler and felt tip marker to number depth marks on the side of the resin can and the catalyst tube.  I found that roughly 1 inch out of the resin can needed about 1/4 inch out of the catalyst for a nice mix.  Photo 2.

Once the resin is mixed you have only 10 or 15 minutes (depending on temperature) to finish the layup, so from this point move quickly and smoothly.  Coat the inside of the mold cavity and about 1/2 inch around the outside with a thick layer of resin.  Some people just pour in some resin and then smear it around with the brush.  Photo 3.

Then stuff the first piece of pre-cut glass cloth into the wet mold.  Use the brush to push the cloth down into the resin, brush on more resin to completely wet out the cloth.  Areas that are not wet out will appear white.  Photo 4.

Put the second piece of glass cloth into the mold and wet it out like you did the first piece.  Then, using the brush in a stabbing, stippling motion to poke the resin into the cloth weave.  The idea is to get all the air bubbles out of cloth and get the cloth down snug against the mold surface.  Air bubbles will appear lighter than the rest of the layup.  Pay special attention to cornors and curved areas.  Photo 5. Keep working the layup until the resin starts to set up.  When the resin starts to set it will first get a jelly like texture, stop stippling at that point and throw away the brush. If you got any resin on your hands, a little acetone will clean it off. 

Let the layup cure for several hours or overnight, then use a putty knife to pry around the outside of the molding until the part pops loose from the mold.  Photo 6.

A bandsaw works great to trim the excess glass from the outside of the part.  Some folks use old tin snips or even sissors.  Photo 7.  Finally, finish with sandpaper, clean the surface with acetone and paint.

Link to Yoke Centerpiece,  Fiberglass Mold

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Fiberglass mold

Carl Ellis was kind enough to let me use his cowl bump to make copies in fiberglass.  Cowl bumps are needed to allow the use of shielded spark plugs, the shielded plugs are taller than the old style plugs and won't fit under the stock cowl.

The first step in making a fiberglass mold is to attach the original part to a plywood base.  I screwed the original to the plywood from underneath.  Then I coated the original and the plywood base with wax. Photo 1.  There's lots of great, expensive fiberglass mold releases and waxes available, but I used plain old car wax, the kind that comes in a can (Turtle wax).

Then I covered the original and base with a layer of fiberglass cloth.  I got my cloth and resin from WalMart.  It took about 1/4 of a quart can of resin to make the mold.  I used a cheap chip brush to apply the resin.  After the first layer of fiberglass I applied a second layer (right after the first layer, before the resin sets).  Then I set a plywood board into the wet fiberglass layers.  I'd cut out the plywood earlier so it would fit snugly down around the original part.  Finally I applied a third layer of fiberglass over the top of the plywood and original.  So I'd made a sandwich of: plywood base, original part, wax, 2 layers of fiberglass, another plywood, and a final layer of fiberglass.  Photo 2.

After letting the sandwich resin cure for a couple hours I used a putty knife to pry the sandwich apart at the wax-fiberglass boundary.  After mounting support rails on the second plywood piece I had the negative mold shown in Photo 3.

Link to Fiberglass Layup

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Brake rivets

The Taylorcraft uses "Shinn" brakes; mechanical, drum style brakes.  Parts are available from Skybound in Georgia.  I got a little kit of parts from them ("send me everything" is what I said) and after cleaning and painting my wheels I was ready to install the new brake linings.

There's two ways to attach linings.  The British method is to bed the linings in epoxy.  The Brits say this method is easier, stronger, keeps the linings from cracking, and you don't have to worry about the linings wearing down to the rivets. 

The other method is to use rivets through the lining and the drum.  The rivet folks argue that rivets are the original method and have worked for over 60 years and anyway epoxy could fail if it gets too hot.  The Brits reply is that, well, they didn't have epoxy 60 years ago or they would have used it and the epoxy bedding method has never failed in thousands of hours of hard use. 

Both methods appear to work just fine, both have their strong points.  So, of course, I used BOTH.  I bedded the linings in epoxy and then put rivets in too.

The epoxy method is by far the easiest way to go.  It took less than 30 minutes to epoxy linings into both wheels.  I used aeropoxy because of its thick, sticky character and reputed high temperature qualities.  I used C clamps and the brake shoes to clamp the linings in place while the epoxy set.

The rivets took a little more time.  First I chucked the wheel under the drill press and drilled holes slightly larger than the rivet shank through the drum and epoxy bedded lining.  Photo 1.  Then from inside the drum I counterbored the hole for the rivet head.  I used a 5/16 drill bit to remove most of the lining material for the counterbore, and then finished the flat bottom of the counterbore with a 5/16 brad point drill bit. No drill motor needed!  I was able to easily make a beautiful counterbore in the soft lining material just by turning the drill bit by hand.  Photo 2.  The brad point drill bit is shown on the left on Photo 3, an ordinary bit is on the right.  Brad point drills are available in most hardware stores.

The top of the rivet head needs to be about 1/16 below the surface of the lining.  Check your counterbore by slipping a rivet into the hole and checking the depth with the depth end of a dial indicator.  Photo 4.  The actual upsetting of the rivet is easily done with a special brake rivet tool (about $20 from Spruce), or the time honored punch and hammer method. Photo 5.

Link to Brake Spring Tool,  Tire Mounting,  Wheel Pants

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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.

Go to Wing 10:Trammel

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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.

Go to Wing 9: Drag Wires

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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.

Go to Wing 8: Reinforcement Plates

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Wing 6 compression struts

Compression struts tie the front and rear spars together.  They are steel tubes with a flat plate (flange) welded to each end.  Bolts through the wood spars and the flanges attach the compression struts to both spars.  Large diameter wood washers are used under the bolt heads.

The wing begins to aquire rigidity with the addition of compression struts, like building a lightweight box.

Go to Wing 7: Rib Installation

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Varnish

Photo: using a Q-tip to varnish the inside of a hole.

Ahh, varnish.  Being a sailor and boatbuilder I love the look and the smell of varnish.  I love what it does to the wood  A good varnish job gives your wood a beautiful honey glow, and it's functional too, varnish preserves the wood and protects it from damage.

Half of the art of varnishing is sanding.  Start with a 120 or 150 grit sandpaper on the raw wood.  Don't use an electric sander or a sanding block.  Use your hand.  Tear the sheet of sandpaper into 4ths and then fold each 1/4 sheet in half and then half again until you have a approximate 2in by 2in pad of sandpaper.  Sand with one side of your sandpaper pad until it loses effectiveness, then turn it over and sand with the other side until that side is worn out...then unfold and repeat until all four sides are used. 

Sanding is a two handed job: the right hand moving the sandpaper over the surface while the left hand comes along behind feeling the surface for smoothness and missed spots.  Use a very, very light touch.  Do not attempt to remove wood.  The idea is to only smooth the surface and you should be kicking up just very little fine dust.

After sanding the raw wood, remove the dust with a tack cloth and then apply the first coat of varnish.  Thin the first coat with about 25% mineral spirits so it will be readily absorbed into the wood.  I use a traditional spar varnish for the first two coats.  Traditional varnish takes a long time to dry, all the while soaking into the wood.  And spar varnish gives your wood a beautiful color, a nice warm glow. The second coat can be full strength spar varnish, and the third coat should be an epoxy varnish.  Using the spar-spar-epoxy combination gives excellent protection to the wood and a beautiful finish.

Use a good varnish brush..(they are expensive, don't cheap out on your brush).  A good brush is very soft and has a really decadent feel to it.  If the hardware store guy won't let you take it out of the package and feel it before buying, just walk away. 

After the first coat is dry (overnight).  Sand, very lightly again, with a 220 sandpaper.  Remove dust with a tack cloth.  Brush on the second coat of varnish.  Let dry.  Sand with 320 sandpaper.  Tack cloth.  Then brush on the third and final coat.  Resist the temptation to add more coats of varnish.  Three coats is just right:  protects the spar, looks very nice, but not too heavy.

Don't forget to varnish inside all those holes you drilled and be sure the ends of the spar get a good coating too.

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Wing 5, Ribs

Transfer the positions of the ribs from the old spar to the new spar.

The ribs are nailed to the spar with tiny aircraft nails and weather you removed the ribs rough or easy they will leave distinctive marks on the old spar where they were nailed on.  Start by laying the new spar and the old spar side by side on sawhorses.  Check that they are perfectly aligned by using a square on the butt end.  Then slide the square down the spar to the first rib position, align it with the nail holes and draw a line.  One line is not enough, because when you go to install a rib the line will be covered, so draw two more lines one on each side of the nail hole line.  The two extra lines should be about the same distance apart as the width of the rib.

Once all the rib positions have been marked, flip both spars over and mark the rib positions on the other side.

Go to Wing 6: Compression Struts

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Wing 4, Trim wingtip to length

Photo shows two spars, the one on the left has been trimmed to length and tapered.

Before the newspar/oldspar sandwich is unclamped (after drilling holes), trace around the wingtip end of the old spar with a pencil. Unclamp the two spars and set the old spar aside. Then using a carpenters circular saw carefully and slowly cut the taper in the end of the new spar,.  You can make a precison cut with a circular saw by holding the guard open with your little finger and then watching the blade as it moves through the wood.  The blade should remain on the waste side of the line and the cut should just barely touch the pencil line.

After cutting with the saw, dress the cuts smooth with a small block plane.  Remember to plane in the direction of the grain, if you try to plane against the grain the plane will catch and rip out little chunks of wood.  It's also possible to do the same thing with sanding block and some course sandpaper.  It takes longer but you're unlikely to damage the wood. 

Go to Wing 5: Ribs

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Wing 3, Drilling holes in new spars

Photo of drill press set up to drill holes in spars.

I mounted my benchtop dirll press on the rolling cart that normally supports my sandblaster.  The old spar was clamped on top of the new spar blank with the butt ends perfectly aligned.  Then it was a simple matter to drill through the old spar holes into and through the new spar.  The drill press assures that the holes are perfectly straight and true and perpendicular to the face of the spar.

One little trick: the oldspar/newspar sandwich should NOT be clamped to the drill press table.  If the sandwich is loosely set on the drill  press, it is allowed to "float" as the drill bit enters the old spar hole and any misalignment will be eliminated as the spar sandwich is able to move to align itself with the drill.  Another tip is to use a scrap piece of wood under the spar sandwich so the drill bit does not burst through the wood as it exits.  That way you get a nice clean hole on both sides of the spar.

Go to Wing 4: Trim Wingtip

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Wings 2, New Spars

Photo of old spar with cracks and bent ribs.

Spar choices: (1) new spars from the "factory" (but the Taylorcraft factory was in start up mode and not able to supply spars, yet able to take deposits on spars...oh,oh!) or (2) new spars from AirRepair (but they were being aquired by WagAero and unable to supply spars...otherwise would have cost about $500 each, 4 required!) or (3) buy spar blanks from Aircraft Spruce and fabricate own using original spars as a pattern.   No choice, I ordered spar blanks from Aircraft Spruce.

And then the pleasant surprize, fabricating spars was easy and enjoyable.  AND it cost about 1/4 of what new spars would have cost if I'd been able to get them!  About $600 total for all 4 spars. 

The spar blanks arrived about 2 weeks after I ordered them. They came in one real long box.  They were absolutely beautiful.  Perfectly straight, fine pitch grain from one end to the 16 foot other end.  There can't be many spruce trees left on Earth that can supply boards like these.  I counted "rings" on my boards and calculated that the tree would have to be at least 100 years old and probably much, much older.

Bonus: the spar blanks/spruce boards came packed between two additional 3/8" X 6"X16' spruce boards.  This "packing material" was almost as good as the spars themselves, and would have been the best boards by far in our local lumber yard.  And 3/8" is the perfect size for making fuselage stringers.  I would use them to make some super lightweight, high strength stringers.  Nothing goes to waste. 

The spars had been milled to the exact dimensions that I'd specified and all I had to do was trim one end to length and drill holes for the hardware.  I'm sure glad I was not able to buy factory spars!

Go to Wing 3: Drilling Holes in Spars

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Wings 1

Photo of right wing with fuel tank and huge birds nest from years of storage.

Both wings were rough.  The right wing had both spars broken.  The plane had been tied down outside when a wind storm broke one of the tie down ropes and then flipped the plane up on one wing.  Extensive cracks in the wood spars left the wing limp and flopping.  Also, years of barn storage had allowed birds to build nests in the wings and their excrement had corroded the aluminum ribs.

The left wing was not as bad.  There was only one 6 inch crack in the front spar and a couple of ribs had minor dents.

I decided to replace the spars in both wings.  But since I wanted to rebuild only one wing at a time (I wanted to have a factory assembled wing to refer to), I started with the left wing.

Disassembly went rather fast.  The hardest part was dealing with the hundred or so #4 sheet metal screws that held the leading and trailing edge pieces to the ribs.  Most of these little screws were badly rusted...so badly that when I tried to turn them, the heads just shredded.  I found that I could remove the really impossible screws by grinding the heads off with my hand grinder, then turning the shank out of the hole by grabbing it with pliers. 

I labeled all the parts with masking tape and a felt tip marker. 

Go to Wing 2: Spars

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aircraft restoration economics

Photo of a Taylorcraft Delux at Oshkosh 2004.

The subject came up recently about what it costs to restore a classic airplane like the Taylorcraft.  Here's my experience with the economic side of aircraft restoration.

SHOP AND TOOLS

I had to build a shop for the project and buy tools.  I did most of the work myself and bought the tools on eBay.  Total about.....$6000.

Then I bought a used car hauler trailer to bring the project plane back home.  It is 18 feet long and 8 feet wide.  Cost.....$1000.

Total getting ready to do restoration______________________$7000

THE AIRPLANE

I bought a project plane that had been damaged (bad wings), but had a zero time engine.  The plane, a 1946 Taylorcraft, had been in storage for 10 years.  A few parts were missing, but mostly it was all there.   Cost.....$8000.

Cost to rebuild the wings, fabricate new wing spars, repair minor dings and dents, replace all AN hardware.   About....$1000.

Cost to restore zero time engine.  New magnetos, plugs, harness.  Overhaul carb.  Repair two cylinders (valves).  Repair baffels, new cowl seal.  New hardware, paint, data plate, new gaskets, hoses, etc.  About.....$2000.

Overhaul old instruments, purchase used instruments, new control cables, hardware, repair magneto switch, new P leads, etc.  About .....$1000

Sandblast fuselage and fittings, new tailwheel, brake ovehaul kit, AN hardware, paint stripper, epoxy primer.  Roughly.....$1000.

Recover materials, Poly Fiber.  Approx.....$3000

Total invested in the airplane _________________________$16,000

TIME

Of course, I'm not done yet, but judging from what I've done so far and the experience of others...looks like about.......2000 hours.

 

So, when I get done I'll have about $16,000 invested in the plane and about 2000 hours of my own time.  They tell me the completed plane will be worth $20,000 to $24,000. 

As a business, this project is a loser.  I would be better off working at McDonalds.  I make only $4 an hour at best working on the airplane.

But as a hobby, this airplane project is just grand!  I get the pleasure of a very interesting project, then I can turn around and sell it, get all my investment back plus a little profit.  And have enough left to buy the next project plane!

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Engine paint and baffels

Paint was Lycoming gray crankcase and black cylinders. I got the paint from Spruce, it's high temperature engine paint in spray cans.

I think the baffels were the hardest part of the whole project.  Baffels are aluminum plates around the outsides of the cylinders.  The baffels seal the engine around the cowl and direct the cooling air around the cylinders.  The baffels that came with the engine looked like they'd been the victum of a cattle stampede.  They were bent and cracked from the engine vibration..  The outside of the baffels was lined with one inch strips of felt.  The felt was soaked through with oil and old dirt. 

The "new" baffels are the old ones hand bent back into shape, with real bad sections cut out and new aluminum sheet riveted back in place.  They are painted with more of that black engine enamel.  I threw away the felt edging seal and used the modern equivalent, silicone rubber strip bolted to the baffel edges with #4 screws and locknuts.  Better than new.

Link to Magnetos,  Cylinders Overhaul,   Compression Test

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Magneto: Eisemann to Slick

Yellow T-Craft at Oshkosh 2004

According to the logbook, my supposed 0 time SMOH engine had new Slick magnetos installed when it was overhauled.  But by the time I got it out of its storage situation, the Slick mags had disappeared...replaced by two disgusting looking Eisemann magnetos. I guess someone needed some nice magnetos and figured noone would notice if the new Slicks were replaced by crusty old Eisemanns.  And, in fact, I didn't notice until I got the engine home and took an inventory of what I had.

My first thought was that the ex-owner of the engine probably had two new Slick magnetos sitting on his kitchen table and would welcome a chance to send them to me.  So I wrote a nice letter suggesting that there had been a minor mistake and I was had HIS old Eisemanns while he had MY Slicks.  I offered to switch them back, I would even pay the freight both ways!

Well, that didn't work.  So next I checked into getting the Eisemanns overhauled.  I was able to find two places that still worked on Eisemann magnetos.  They quoted around $300 for each to return the old dogs to airworthy condition.  About $600 total.  Add in a new ignition harness, and new plugs and the total came to almost $900.  Seemed like a lota money to be running 60 year old electrical gear.

I got on the phone one day and started calling around.  Mattituk quoted $950 for two new Slicks, new harness, and 8 shielded plugs.  The only catch was that I'd have to trade in the old Eisemanns.  OK  Two weeks later, my old A-65 was sporting an entirely new ignition system.   

Link to Engine Paint and Baffels,   Cylinders Overhaul,   Compression Test

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Stromberg carburetor

The Continental A-65 has a Stromberg carburetor, a NAS3A1 model.  Very simple unit, no accelerator pump and no mixture control.  Just a venturi with a supply of gas in the float chamber.  Problem 1: with no accelerator pump, it doesn't give an extra little shot of gas to the engine when the throttle is opened, so increases in power need to be done very slowly.  If you quickly jam the throttle ahead, like you might do in a panic/emergency situation, the engine sputters, hesitates, seems to stop for some seconds.  Problem 2: no mixture control, so it's impossible to adjust the mixture for higher altitudes.

Both these problems are cured by going to the Marvel carburetor that was used on some old Continentals.  But Marvels are not made anymore, and used ones are impossible to find. 

So, Plan B, I decided to overhaul my old Stromberg and just live with it's drawbacks.  I figured I could do it myself.  There's plenty of how-to information on the web and parts are available in Aircraft Spruce.  But when I tried to unscrew the main nozzle, it just broken right off.  I was stuck with a useless, 60 year old pile of junk.  Nothing to do but throw the old broken parts in a box and send them off to D&G Supply in Michigan in hopes that they could fix it.

It turned out that the folks at D&G are very helpful, they even donated some of their stock of used Stromberg parts to get my carburetor back together, at no extra charge.  Two weeks later I had my old carb back looking like new with a nice yellow tag!

I'd found two good suppliers.  What did they have in common?  When I talked to them on the phone, they both seemed to be interested in my project.  And they both went the extra mile to make my project successful.  A good rule to follow in the future.

Continental cylinders overhauled

The engine was bolted to its engine mount and the engine mount was bolted to the wall of the shop.  Baffels and ingnition and intake stripped off.  Then cylinders 1 and 3 were unbolted from the crankcase.  Those special very expensive wrenches are NOT required, ordinary box end wrenches work ok, if rather slow.  The rocker arms were removed and set aside, the push rods pulled out and labeled.  And finally, the cylinders were pulled straight our, being careful to catch the piston as it came clear of the cylinder.

With both cylinders on one side of the engine removed it was now possible to view the inside of the crankcase.  I had thought that I might find a rusted mass inside after years of storage...but this time my luck was good, and the inside of the engine was clean and shiney.  It looked like new!

I plugged the space where the cylinders had been with paper towels to keep dust and crud from getting into the crankcase.

Next, some research was required to find the best (cheap) source of engine parts and service.  It turned out that Aircraft Spruce had a great selection of parts for old Continental engines, and good prices, too.  I ordered all new gaskets, intake hoses, push rod seals (all the "soft" parts), plus new hardware...nuts, screws, hose clamps.

I went to the web for advise on a good cylinder overhaul shop.  Someone on the Taylorcraft forum suggested Marrs Aircraft in Florida.  I called the next day and talked to Mr. Marrs himself.  He's an ex-cropduster who at one time had flown out of my wife's home town of Miller, SD.  He advertised "Cylinder Overhaul $99 (plus parts)" which seemed almost TOO good.  There had to be a catch...maybe his parts were real expensive, or he'd keep my cylinders and want $500 to send them back, or maybe...?  But then my father was a cropduster and the Miller connection was a remarkable coincidence.  

I decided to send my defective cylinders to Florida.  It turned out to be a smart decision.

Link to  Compression Test,   Engine Paint and Baffels,   Magnetos

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Continental A-65 compression test

My project plane came with a supposed 0 time SMOH Continental A-65 engine.  But it was 10 years in storage since the overhaul and, of course, that fact alone raised questions about the engines airworthiness.  So a compression test was the first order of business.

To test compression on a car engine, you screw a pressure gauge into the spark plug hole and then turn over the engine with the starter.  The compression of that cylinder is then read directly from the gauge.  We might call the car compression test a dynamic test since the engine is turning during the test.

In contrast, the compression test on an aircraft engine is a static test,  the engine is set at top center and left there during the test.  The test rig for an aircraft engine test has two gauges, the first one measures the input pressure...set at a standard 80psi.  The second gauge measures the pressure inside the cylinder.  Between the two gauges is an "orifice", a small hole.  If the cylinder being tested is perfect, there will be no air flow through the orifice and both gauges will read 80psi.  But if there is any leakage in the cylinder, the first guage will continue to read 80psi but the second guage with read some lower figure,  depending on how bad the leak.

The great thing about this kind of compression test is that you can actually hear the air leaking out of the cylinder.  An exhaust valve leak will be heard through the exhaust.  An intake valve leak through the intake system.  And leaking rings will make themselves known by a hissing in the crankcase.

Compression figures, then, are given in numbers like 78/80 (very good) or 52/80 (bad).  The FAA suggests maximum 25% leakage, so 60/80 would be the lowest compression figure you'd want to see. 

But the compression test is supposed to be done on a warm engine, just after running (hard to do on a project plane), and after the engine is well broken in (not possible on a zero time engine).  But, still, you can learn alot about an engine's condition in short order.

So, in November, we ordered a test rig from Aircraft Spruce and set up the test.  Sharon would hold the prop (they'll kick if you don't), and I would read the gauges.  It's easy to find top center, just hold a thumb over the spark plug while rotating the prop.  You can feel the pressure on compression stroke.  Then turn on the pressure on the test rig, read the gauges, listen for leaks...then go to the next cylinder.  The whole test didn't take 5 minutes.  The results:

Cylinder 1     0/80   leaking out the exhaust

Cylinder 2     65/80 leaking past the rings

Cylinder 3     30/80  leaking out the exhaust

Cylinder 4     75/80  leaking past the rings

Link to  Cylinders Overhaul,   Magnetos,   Engine Paint and Baffels

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Taylorcraft progress

I got off to a slow start on my restoration project because I had to first build a shop in my backyard so I'd have room to do the airplane.  The shop building is just barely big enough, 16' X 24'.  I can work on one wing at a time, or I can work on the fuselage if I move everything else out of the building.  It took about 3 months to complete the shop.  I put insulation in the walls but left the ceiling open so I could store materials in the rafters.  I have 2500watts of electric heat and 4 windows on the south side.  The east side has a 8' X 7' garage door facing a brick face "patio".