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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