Sunday, August 13, 2017

Better Paint Mix and Second Coat on the RH Upper Wing

When I mixed a new batch of light green, I realized I had made some mistake with my spreadsheet for calculating the pigments.  It was causing the quantities of pigments to be so low the paint was watery.  I had seen this with the red, blue and black, but it was much worse with the green.  I spent the morning re-measuring all my pigments by weight and volume to determine their density.  I needed this to correctly convert my weight (gm) measurements into volume (ml) measurements so I could use measuring scoops.

When I first mixed the colors I had access to a very accurate scale.  All I have now is a small kitchen scale which is not accurate enough to measure such small quantities.  Most of the pigments come in 175 ml jars so I have large enough quantities to work out the density with the kitchen scale.
The densities are:
Lamp Black                     0.17 gm/ml
Aluminum Powder           0.27
Prussian Blue                  0.55
Alizarine Crimson            0.66
Litopone                         0.83
Burnt Sienna                   0.87
Chrome Yellow                0.87
Chrome Orange               1.18

 When I mixed the colors I used about 4 times as much pigment as my attempt with the Light Green, which was what I found with the black.  The colors still match and the paint covers much better.
The color mixes here are for Light Green, Beige, Red and blue.  Each has about 25 ml of pigment for a quart of Poly-Tone.  The Alizarine did not want to mix well with the Poly-Tone but the color seems to match my old samples.
 We had another warm dry afternoon so I started the numbers on the lower left wing, and did the red and blue on the roundels.

The upper right wing got a second coat on all the colors.  The red and yellow need another coat and then I can outline the numbers.

After 26 years it's nice to see this paint job getting close to being done.  I really like the look.

Thursday, August 10, 2017

 The afternoons yesterday and today were both nice and dry for painting.  Yesterday I got the second coat of all the colors on the top of the lower wings.

I also got started on the red in the roundels.  The green stripes are squadron stripes for the 103rd Areo Squadron.  They still need red stripes between the green.

 In the evening when it was too damp to paint to paint I drew all the color boundaries on the top of the upper wings.

Today I was able to get the first coat on the top of both wings.  When the colors are done I'll add a black border around the numbers.

 The upper right wing gets the same green and red stripes as the lower left.

I got the numbers drawn on the lower right in the evening today, but it was too damp to paint them.  Odds are I won't get to do any more painting until mid September.

I did get the gasket set for the engine so I can pull the cylinders to check for rust.  I've only got about 125 hours since the overhaul so I don't want to risk damaging the engine.

Sunday, August 6, 2017

Painting the Camouflage Colors on the Wings

 The weather has dried out for a couple days so I finally got some color on the top of the wings.  I bought 4 gallons of the clear Poly-Tone base so I can mix my own colors.  I also bought a quart of Blush Retarder to slow the drying and help with mixing the pigments.  Austin at Preferred Air Parts was very helpful.
I found a plastic lid, at the hardware store, for the gallon can which has a small poor spout.  It allows me to easily poor small amounts of the base without making a mess.
 Based on my color formulas I measure the pigments into my mortar.  This mix is for making 1 quart of the dark brown, Chestnut, color.  It uses Lamp Black, Chrome Orange, Chrome Yellow, Burnt Sienna, and Alizarine Red.
 When I did this with dope I used one of the plasticizers for mixing the pigment.  With Poly-Tone I used some blush retarder, 4 teaspoons for a quart of Poly-Tone.  It gave me a liquid which wouldn't dry quickly while grinding the pigments and it helps the Poly-Tone flow out the brush marks before it drys.

You grind the pigments with the pestle until you get a good even color mix.  You can see the color change as you grind it together.

 The hardware store sells empty paint cans.  My little paint spatula bends nicely to scrape most of the mix from the mortar.  When I did this with dope I used a little thinner to wash the last of the pigments from the mortar.  The Poly-Tone is already very runny so I didn't want to add thinner.  Instead I cleaned it a couple times with a couple tablespoons of the clear Poly-Tone.  It worked pretty good but I didn't get it as clean as with thinner so I used 1/4 more pigments to allow for some not getting to the can.

 Once the pigment mix was in the can I added the aluminum powder.  For this color it takes 14.75 ml, 3 teaspoons of aluminum.

Then I fill the can 1/2 with Poly-Tone and shake it vigorously for 3 minutes.  I don't know if less will work as well but 3 minutes is all my arms can take.  I then finish filling the can and shake it another minute.  The Poly-Tone is so runny you need to stir it often while painting.

 I start with the lightest color and work to the darkest so each color can overlap about 1/4".  The beige seems a little lighter than the dope on the fuselage but the other colors match very well.  2 coats seem to get a good even color.

 The process is pretty simple.  I draw the pattern on the surface with a soft lead pencil, which won't bleed through the Poly-Tone.  The patterns used by each of the SPAD subcontractors were so consistent that they must have had a pattern they traced for each surface.  Mine were free handed from my sketch.

I mixed a quart of each color, except Black for which I only made a pint.  It looks like I'll need another quart or 2 of beige and light green.  Originally I planned to mix a gallon of each of these colors but I'll never use that much.

I finished the center section and ailerons.  I've got one coat on the top of the lower wings, none on the upper wings.

 I also got the first coat on the blue for the lower wing roundels.  The blue and the black both seem much weaker with Poly-Tone than they did with dope.  I probably could have doubled the amount of pigments in the blue, and I used 4 times a much lamp black to get it to cover in 2 coats.  Mind you, I used 4 teaspoons of lamp black in a pint of Poly-Tone, and I have 5 quarts of lamp black dust.  I won't use it up in a thousand years.

I did find the Poly-Tone a pain to brush compared to dope.  It runs easily and you get bubbles easily while brushing.  I'm getting the hang of it and it looks great.  I really like the look.  Because of the aluminum powder you see every brush stroke so it has much more life to it.  It also looks Like WWI French Camouflage would have looked.

Sunday, July 16, 2017

Painting Roundels and Center Section Installed

 The grand kids, Rowan and Duncan, visited for a couple weeks around Independence day.  We had a nice dry day near the end of June so we started painting the roundels on the lower wings.  We made a cardboard pattern and drew the circle with pencil on the wings.  As with the rest of the SPAD paint scheme the roundels were brushed on.  One thing we learned was, unlike dope, Poly-Tone really softens the the paint you're applying it to.  It will take at least 2 coats of white to get the cream not to show.  They had fun and we made progress.

The weather has been mostly hot and humid.  Today wasn't to bad so I installed the center section.  We fit the center section to each wing before installing it just to make sure I put all the fittings back on correctly.  Everything fits nicely.  Once the cowl is permanently installed I can safety wire the turnbuckles.  Nice to be putting things back together.

Sunday, June 4, 2017

Dad's Pitts Special Model 1951 - 2017

While visiting my parents for my Mom's 90th birthday party I noticed my Dad's old Pitt's Special model.  Going with Dad to the flying circle was one of my favorite treats.  Watching him fly that Red and White Pitt's is just one of those great memories.  The plane has always hung in his workshop a never fails to remind me of going to the flying circle and watching him and all his friends flying, dog fights, jets and stunt jobs.  It was great fun!  I think is was a major reason all I ever wanted to do was build and work on airplanes.  We built a Fly Baby and fixed op an L-2 Taylorcraft while I was in High School.  Fifty plus years later as an A and P, Private Pilot, and Aerospace Engineer, I still have the Fly Baby, and 2 other projects.

We were looking for something in his shop in the barn and I asked him when he built the Pitt's, since it just always seemed to be a part of our lives.  He couldn't remember exactly but he always took pictures of models he built and has the pictures all in albums, many albums.
We got to searching and sure enough there was a picture of my older brother David (right) holding the plane in 1951.  Dad's in the middle and uncle Peter, 2 years older than David on the left.
We did some more searching through all Dad's well organized magazines and found an add for the Pitt's on the last page of the January 1951 issue of Model Airplane News.  The add for the McCoy 29 was on the back cover.  The kit was $4.95 but the engine was $11.95.  Dad, a retired cop, always worked part time at a hobby shop so I suspect he at least got a small discount.
The model appears to be one of the few which never crashed.  I think the real hobby is fixing busted planes.  All the paint job on the wings and tail is done with the original decals.  I never realized it was all decals until we got looking at it.  He was thinking he should recover it.  I suspect there aren't many models that old and still so original.  The only change has been to rotate the engine to the outside.  I wondered if it ran better that way or if it's a different McCoy than originally installed.  Engines moved from model to model and had a way of occasionally getting damaged in the dirt, usually at high speed.  Ah the excitement of watching airplane parts flying in all directions, when it's someone else's plane.  The truth is much simpler, the control lines didn't stay tight with the engine facing into the circle.  Turning the engine to the outside solved the problem.

We decided to recreate a couple of the pictures of the Pitt's.  The spiffy shirt is long gone but their current house has  the same shingles as the old one.  The tissue paper is starting to fail but other than the pilot, added some years later, it's all original, and in very good condition.

The day we took these pictures dad was getting ready to start working an a large scale P-40 kit he got in a deal for his P-51 model which the other fellow should enjoy flying as much as dad did.  The P-40 has retracts and all so it should keep him busy for a few days.

I'm glad he still has the Pitt's.  The memories it brings back are treasures.

Brace Cable Length Fixture

Having figured out how to make the wire wrapped cable ends the way I wanted, I needed a way to make sure the cable length was correct.  Wrapping and soldering the ends was too much work to remake one because I messed up the cable length.  When we assembled the plane the first time we did it in the barn, and just made each cable to fit the plane with the wings held in position.  When I started this it was fall and I didn't want to leave the plane assembled in the driveway for weeks.  I also wanted to recover the wings while I made new cables.

To control the length I made a simple fixture from 2x4s and some pieces of angle iron.  The block and angle bracket on one end is screwed to the 2x4.  The other end can be positioned to the desired length of the cable and just clamped to the 2x4 frame.

I assembled the plane and rigged all the cables tight.
I measured each cable length from the edge of the fitting, at one end,to the center of the pin, on the far end of the turnbuckle, at the the other end.

The fixture is set up to duplicate cables using the distance between these same references, the edge of the fitting and the pin at the far end of the turnbuckle.

I made a bracket at the fixed end to hold the fitting.  It's screwed to a piece of 2x4 which is screwed to the 2x4 base.
I found I needed to protect the fitting paint from scratching so I made a protector from a plastic blister pack.  It had a nice fitting square corner.

The 3 holes are for socket head cap screws which keep the fitting from sliding off the end of the bracket, which it did without them.
My length measurement starts from the fitting side of the bracket.  If I had been thinking, I would have positioned the angle bracket on the block so the fitting side of the angle was in line with the edge of the block
I took all my measurements in centimeters because it was easier.

The movable block was made so the measurement between the edge of it and the edge of the fixed block is exactly the length of the cable.  As a result all I have to do was measure from the fixed block, draw a line for the front of the movable block and clamp the movable block on that line.

The bracket on the movable block has eye bolts for the turnbuckle pins.  Since all my wing brace cables are double I used 2 eye bolts.  In the end I did each cable as a separate piece so I could have done this with 1 eye bolt.

One advantage I found to 2 turnbuckles was the ability to easily lock the turnbuckle barrel so it wouldn't unscrew while working.

I crimped the Nicopress sleeve on the free end of the cable but did not wire wrap it until cutting the cable to length.  You can't spin the cable while it's still attached to the reel of cable.

With the length set and the turnbuckle at zero threads showing, I pulled the cable snug, then cut it off about 8" past the fitting end bracket.

The turnbuckle end was then wire wrapped and soldered.

I found a couple nails and a safety pin made simple stops to keep the cable end from turning in the barrel.

Slip the Nicopress sleeve on the cable, pull the free end of the cable around the thimble on the wing fitting, then back through sleeve.
To grip the free end of the cable, so I could pull it tight, I modified a cheap pair of Vise Grip type pliers.  I used a chain saw file to make a groove to fit the 1/8" cable.  I felt it gripped better than flattening the cable end in the jaws.  The groove needs to be such that there is a slight gap when the jaws are tight.

This works really well.

I removed the adjustment screw on the pliers and installed a 5/16" eye bolt so I could use a ratchet strap to pull the cable tight.  The cheap pliers had a metric bolt with threads very close to 5/16 UNC.  I just ran a tap down the threads to clean them enough for the eye bolt to turn freely.

The ratchet strap works well to pull the cable tight.  To keep the 2x4 from bending I screwed another 2x4 to the bottom, forming a "T" section.

I also added some 2x4 feet so I can clamp it to saw horses at a convenient working height.

With the cable tight the Nicopress Sleeve is positioned with a 1/16" gap to the thimble, as on the other end, and squeezed.  I had to take the cable out of the fixture to make the squeeze closest to the fitting.  If you don't you just can't see what you are doing to position jaws.

My original idea was to leave the first cable in position while crimping the second cable.  With very little thinking I would have realized the 2 cables were too close together to squeeze the second cable with the first one tight.

Tip it back out of the way and do the second cable.  You still need 2 slots in this bracket for everything to fit.

The cable is then ready to finish wire wrapping the ends as discussed in the previous posting.