1940 Stearman restoration (moved from Triumph forum so all can enjoy)

[Graham H]

Bob, I was wondering the same thing.

Graham

 

[NutmegCT]

I'm thinking ... an antique fire extinguisher.
You can see the pump handle at the top, in an earlier picture.

 

[CJD]

Hey Bob. That is a turn of the (last) century ship fog horn. My Father used to frequent old nautical junk yards and restore old brass hardware. This is one of his restoration pieces. Every time you pull or push the handle it gives that lonely, low pitched, haunting, "Aaaaauuuuuhhhggg". It used to be very shiny brass, but every child in our family (including me as a kid), has used it so much it needs a polish. The green entrance piece was my great Grandmother's, that my Dad restored when I was 3. It never occurred to me, but both those items are older than the 85 year old Stearman?!? I may have to schedule their next restorations after I finish the plane.

 

[Nivens]

It seems to me antique cars and airplanes go together and always have. My first car was a Healey 3000 which I had to give back to the finance company when I was drafted into the Army. After serving in Viet Nam as an assault helicopter pilot and instrument instructor, I took up fixed wing restorations and flying. I completely restored two Piper Dakotas, built an RV8A, and worked on building a Lancair 4 for 2 years. I also built a Hot Rod while in high school. I built a custom Cobra replica with all custom parts. Currently I have another Healey 3000 frame off restored which I am currently putting a new interior in.

I truly admire your bravery, commitment, tenacity and the workmanship demonstrated in your current Stearman project. It is obviously a labor of love and enjoyment for you.

 

[CJD]

That's an impressive history of builds, Nivens! I have enjoyed all my restorations, but I am thinking this will be my last grand effort. There are some things I would like to do and places I want to see...so I will keep my projects to under a year from now on?! Plus, I am sure you guys have noticed, insurance has risen out of sight the last 5 years. Most of my cars are 20+ years old, paid off, and only insured for liability...yet they are still charging over $100 per month! We haven't even had a claim in 20 years.

 

[Graham H]

Yes, John, and every year, insurance companies increase the value to keep pace with inflation just so they can increase your premiums.

Graham

 

[DocDup1]

If it were not for Hagerty Insurance I would have to sell off a couple of cars. I don't know how they do it, but they sell really great coverage for less than half of what I would have to pay from a regular insurance company.

 

[Gliderman8]

That's an impressive history of builds, Nivens! I have enjoyed all my restorations, but I am thinking this will be my last grand effort. There are some things I would like to do and places I want to see...so I will keep my projects to under a year from now on?! Plus, I am sure you guys have noticed, insurance has risen out of sight the last 5 years. Most of my cars are 20+ years old, paid off, and only insured for liability...yet they are still charging over $100 per month! We haven't even had a claim in 20 years.

Not Political, just facts….
I read that all auto insurance rates may rise since “over and above taxes” will add to the cost of auto repairs so insurers will need to raise rates.

 

[CJD]

Just a quick update. It turns out the ailerons are NOT a quick job. But then, I kinda' figured they would slow me down. I counted about 800 rivets per aileron that I had to drill out. I then had to locate many replacement ribs to replace the mangled parts. Here is the aileron spar going on the jig I welded. About half of the spar had to be replaced, as there were bends and cracks from the crash.

I am getting a little better driving rivets...but I still cringe when I send pics to my A&P supervisor!!

Here the ribs start going back on. The jig keeps the spar...and therefore the aileron...straight as I work.

 

[CJD]

Next, the curved tips go on. I had to remove the aileron to install on it's wing, so that the tip will match the curvature of the wood wingtip built earlier.

Now she's ready for the covering that goes around the leading edge...with...868 rivets!?! The sheet covering forms the closed "D" section which gives the aileron stiffness from twisting. That is very much like the Triumph's fully boxed frame! Or...very unlike the Model "A" Ford frame which was an open "C" frame that twisted easily.

I am sure the scorching on some of the ribs bothers some viewers. Those are ribs that were mangled and had to be straightened. With aluminum, you must anneal it before doing any major bending or straightening. If you try to straighten a bad bend, the thin sheet will crack...and that's the end of the road for that rib. They are much too thin to repair by welding. A trick is to mark the aluminum with a sharpy. Then when you heat it, you know to stop heating when the sharpy mark just disappears. If you heat any more, you end up with a small puddle of aluminum that used to be your part, LOL. Once it air cools you can do some more straightening without cracking.

That's it for now...

Hope everyone is taking advantage of the nice Spring weather to get the cars out for a ride!

 

[Basil]

Next, the curved tips go on. I had to remove the aileron to install on it's wing, so that the tip will match the curvature of the wood wingtip built earlier.

Now she's ready for the covering that goes around the leading edge...with...868 rivets!?! The sheet covering forms the closed "D" section which gives the aileron stiffness from twisting. That is very much like the Triumph's fully boxed frame! Or...very unlike the Model "A" Ford frame which was an open "C" frame that twisted easily.

I am sure the scorching on some of the ribs bothers some viewers. Those are ribs that were mangled and had to be straightened. With aluminum, you must anneal it before doing any major bending or straightening. If you try to straighten a bad bend, the thin sheet will crack...and that's the end of the road for that rib. They are much too thin to repair by welding. A trick is to mark the aluminum with a sharpy. Then when you heat it, you know to stop heating when the sharpy mark just disappears. If you heat any more, you end up with a small puddle of aluminum that used to be your part, LOL. Once it air cools you can do some more straightening without cracking.

That's it for now...

Hope everyone is taking advantage of the nice Spring weather to get the cars out for a ride!

Wow, impressive!

 

[CJD]

I can’t wait to finish this…like when I did the TR2, parts are being stored in every open area around the whole house. It’ll be like doubling the house size when the parts all leave!

 

[70herald]

Wow this is almost like building an entire plane from scratch! very impressed.

 

[CJD]

Running late on the updates...again!

So, the ailerons are finished, after almost 2000 rivets.

It was now time to cover! This part is exciting, as the plane starts to take it's aerodynamic shape. I'll start with the vertical tail fin to show how covering goes. There are currently 3 systems to cover planes that the FAA recognizes. There is the original dope system. This is easy to do, but is highly flammable and only lasts 5-10 years. Then there is a water based system by stewart. I went with the third, which is a vinyl based system called "Polybrush". The latter 2 systems will last indefinitely. The covering on my plane was polybrush and over 40 years old...and it was the crash that killed it!?!

So here is covering with polybrush:

Here is the tail fin, which I had to build from scratch. It is primed to last another 80 years...hopefully! The first step is to use a cloth tape to give some insulation anywhere that a sharp metal part comes into contact with the fabric.

There are 2 ways to cover. One is called the "blanket" method...where you just lay a cloth over the part and glue it around the edges. I went with the "envelope" method...because that is how Boeing did it, of course. The envelope is a sock sewn to the shape of the part. It is placed over the part and then the open end is both glued and locked with a plate.

Of course...it is obvious that you cannot get the fabric perfect, so it is loose and wrinkled at this stage. Next comes the magic...

 

[Gliderman8]

Did you have to sew the envelope that covers the tail?

 

[CJD]

Here is the fabric all tight and perfect! This is done with a regular household iron. First set to 250 deg, and finally fully shrunk and tightened at 350 deg. They warn you that if you allow the iron to go over 350 then the fabric goes loose again and is ruined for good.

This is how relatively modern processes have come to play. The original covering was cotton...first shrunk slightly with water, and then fully tightened with 4-6 coats of nitrate and butrate dope. Polybrush uses a polyester fabric that shrinks with heat. Once shrunk, it is as tight as it will ever be. Whereas the dope shrunk the cotton...the vinyl solvents in polybrush do not shrink anything. They merely seal the fabric water tight and block the UV light, which is the one thing that will destroy the polyester fabric.

Let's keep going...

In this step one coat of polybrush vinyl has been brushed onto the fabric. This locks the fabric and seals it. Then, you can see the cotton reinforcement strips which are laid over the top of the ribs. You will note the pencil marks. The marks locate where stitches will be laced to draw the fabric tight against the rib. Without the stitching, the fabric would pull away from the rib and ruin the airfoil shape. The blueprints and the FAA have specific rules on the spacing of the stitches, depending on the top speed the plane will go and whether the area is within the propeller arc or not. Spacing will be between 6 and 1 inch. For the fin and rudder, 2" spacing is the spec.

Also of note...each stitch is locked with a running knot...called a sein knot. It allows you to use a single length of chord for each rib. The knots and chord between each stitch is pulled into the control surface. This took me a week to learn. I had to practice...and then make...so many stitches that I think I could do sein knots in my sleep?!?

Once the stitching is complete, then you must use the polybrush to glue tape over the stitching. This closes the holes from the stitches and re-seals the fabric.

So far all the polybrush has been hand brushed onto the fabric. Now we will switch to a spray set up for following coats. The fin and rudder above have been sprayed with 2 more coats of polybrush. This leaves a rubbery sealant, which can be flattened easily with the iron where needed.

 

[CJD]

Now comes the "patching". These patches are spelled out precisely in the Boeing blueprints. They add strength to any openings in the fabric, or places where chafing might occur. These are glued on just like the fabric tapes, using more polybrush.

This picture shows the patches on the stabilizer:

 

[CJD]

Oh, Elliot, I see you are already following! Yes, I have been sewing the envelopes. Amazingly, every envelope size and shape is precisely spec'd out in the Boeing Blueprints, including the placement of the machine stitches! Here is a photo sequence of the ailerons being covered:

 

[CJD]

Now, I have never owned a paint booth. For car painting I have gotten away with using garages, or spraying on the driveway in the winter months, when the bugs are fewer. The shear volume of area needing many coats of paint in on the Stearman had me thinking of alternatives. For $500, I found a blow-up paint booth...COOL!!

For about half that cost you can get a smaller booth that a Triumph would fit in. I needed one that will take the wings and fuselage. It's about an extra hour to set-up and take down...but well worth it to keep the bugs from sticking to my fresh paint and doing a death trail through the wet paint.

So, after the 2 sprayed coats of polybrush, you then switch to polyspray...which is the same viny base, but with aluminum glitter. This is what blocks the sun's UV for the next 40+ years and gives the longevity to this covering job. You spray 4 coats of polyspray, sand lightly, and finish with 2 more coats to replace the UV protection that was sanded off.

Here is the wing center with all 6 coats of silver UV protecting polyspray

 

[CJD]

Now it gets fun. Once all the polyspray is on, the parts are ready for the final color coat with "polytone". They make a urethane that gives the plane a modern wet look (aerothane), but that is not what I am going for. I am going for the semi-gloss look that the original doped fabric had in 1940. That is best duplicated with the polytone.

I do not like the original Navy color of school bus yellow. After 5 years of research, I learned that...although most modern Stearman are painted in the Navy yellow peril or Army blue and yellow...it turns out that during WW2 most Stearman were silver! Silver is the UV protective color used prior to painting. Since 10,000 planes were built, but 50,000 planes worth of spare parts...Boeing provided most planes in silver and allowed the Army/Navy to paint the colors they wanted. During the war, they did not have the time or resources to repaint. Thus...the most common color was silver. I can live with that! The tail and a fuselage band was added for the squadron, but that was it. I was glad to learn that all the crop dusters that my Father flew in the 1950's were still in their military silver dope.

Our plane will be silver, with squadron colors of blue. Here is the finished rudder:

I am sure most of you are wondering what the deal is with the ugly stenciled lettering? These are the part number and dope codes, provided so the army/navy can keep track of the type, amount, and date of the covering. If it gets too old, it must be replaced or "rejuvinated" (a story for another day). My goal is originality, so as ugly as they were (are), the codes are there. Remember, these planes were work horses, training tens of thousands of pilots with minimum maintenance. They were utilitarian during the war, and even more utilitarian as crop dusters for 50 years after the war.

You guys may find it interesting how I got the stenciling. It was originally done using large cutting machines...which are expensive if you can find one at all. I had to manually build each letter in autocad, and then build each stencil individually to laser cut. I then spent weeks deciding the best way to apply the paint. I could have done it absolutely perfectly, but chose to use a standard stencil and an airbrush...leaving period similar imperfections. Again, chosen in the quest for originality.