# S-38 Restoration



## Builder 2010 (Jul 25, 2019)

My modeling reputation has gotten out in Louisville, KY. There is a monument in the historic Bowman Field admin building commemorating a flier who was lost in 1937. A metal model of a Sikorsky S-38 seaplane sits atop of a bronze hemisphere and several years ago, when moving the very large object, the model fell off and was severely damaged. The members of the historical society patched it up with hot glue and it looks just as bad as that sounds. 

One of the members of the Bowman Field Historical team had just joined the Military Modelers Club of Louisville of which I am a member, and the first meeting he attended was the one where I was running a soldering clinic. He came to the conclusion that I was the person who could restore this model. 







The model is cast and is probably pot metal which makes it effectively non-solderable. I have restored some interesting models and took on the assignment. We're meeting next week to discuss particulars since this a paid endeavor. I will probably have to drill and use pins and epoxy to put it correctly together. It's missing one prop which I'll have to scratch-build. But since I now own a high definition 3D Resin printer, if I can draw it (or get the existing one scanned) I can make one. Here's the rest of the pictures I took today. Any input would be appreciated. I really don't know how much to charge for my services. We've agreed in principal that it would be a cost plus materials contract, but what the "cost" is I have no idea. I don't know how long it's going to take until I pull it apart and get rid of all the old hot glue. Hot glue is good for craft projects, but has no business on model restoration.

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## MiTasol (Jul 25, 2019)

Builder 2010 said:


> My modeling reputation has gotten out in Louisville, KY. There is a monument in the historic Bowman Field admin building commemorating a flier who was lost in 1937. A metal model of a Sikorsky S-38 seaplane sits atop of a bronze hemisphere and several years ago, when moving the very large object, the model fell off and was severely damaged. The members of the historical society patched it up with hot glue and it looks just as bad as that sounds.
> 
> One of the members of the Bowman Field Historical team had just joined the Military Modelers Club of Louisville of which I am a member, and the first meeting he attended was the one where I was running a soldering clinic. He came to the conclusion that I was the person who could restore this model.
> 
> ...



Quite beyond me that is for certain.
Would love to see photos of the finished job

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## Capt. Vick (Jul 26, 2019)

Good luck!


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## Gnomey (Jul 26, 2019)

That repair job is interesting to say the least. 

Looking forward to your efforts!


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## TheRealMrEd (Aug 1, 2019)

It sort of appears that some of the metal plating has been damaged. If so, I doubt that you can plate over epoxy, etc. to repair the finish. Might have to go with some of the metal paste type repairs...

Ed


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## Chris H (Aug 1, 2019)

That looks like a lot of stripping off the glue; cleaning and straightening the struts; followed by drilling and pinning with brass or steel rod. Then maybe use Bondo or Milliput to fill and strengthen the joints, followed by rubbing down and a re-spray with a metallic bronze shade.
It's not beyond the realms of a competent modeller, but it's going to take a lot of time and patience. If you have any other Club members who could help, it would be good!
Please keep us updated on this one and "Good Luck"!


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## Builder 2010 (Aug 1, 2019)

Thanks guys! I'll run this as an active thread. We agreed to a price (decent!) and I brought i home in pieces. The whole thing fell apart when we got it off the monument. 

There may be a hitch in my agreed to price and I won't be starting until any misunderstandings are clarified. Meanwhile I came up with an elegant way to support the plane in proper configuration for reassembly. It turns out that the whole thing is either cast brass or bronze, not pot metal. That means once I get it cleaned up and down to base metal, I can use normal soldering procedures. It will be much stronger than going with any sort of glue. The thing weighs a ton with the main wing well over 20 pounds and the cabin and lower wing slightly less.









What I'm planning is this. I will install long threaded rods into the build board with nuts and washers above and below. I will then have nuts and washers at the level that the part to be suspended. This level will include a formed block of wood to support the wing and then another more flexible piece above and then another set of nuts and washers. I will have the lower wing upside down on the build platform with any level or padding to stabilize it, and the cabin and lower wing suspended upside down above it. This way I can fine tune the positioning by raising or lowering the nuts on the threaded rod. 

Here's what the real plane looked like.









The model's wing span is 41" so the scale is an odd 1:21. That's just plain weird. I thought there was a prop missing, but it was laying on top of the model on it's pedestal. The mounting will have to be re-designed also since it was cobbled together with some 3/8" bolts. I'm going to copy and enlarge the drawing so it will be full size and use it for positioning and building any unrepairable spars.









If

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## Wurger (Aug 2, 2019)




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## Airframes (Aug 2, 2019)

A bit of a challenge, but I'm sure you'll manage it.
Looking forward to seeing the result.


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## hainus (Aug 18, 2019)

Have you tried to use a fine blow torch and join them with silver solder ?
i use to make clutch and throttle cables for motorbikes and found silver solder was alot stronger than normal solder.


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## Builder 2010 (Sep 12, 2019)

Hey gang. After working on another model railroad extravaganza I'm now starting to do the S-38 restoration in earnest. The model is worse than I thought partially because I knocked the wing onto the floor and broke of the tail section and two more long struts. Regardless, everything had to re-soldered. Before doing that I have to strip all the paint and the residual hot glue that was used to patch it together four years ago. Stripping the paint is a messy, smelly job that got complaints from my wife upstairs when the air conditioning system was sucking the fumes and distributing them all over the house. I just striped the engines, the tail and all the loose parts. The Bowman Field Heritage Group thought it may be great to have the model in bare metal to match the bronze globe on which it's fastened. It may be possible, but there are some concerns. The model is actually three metals. The body and wings are bronze or something that looks like bronze, the long struts are brass and the short ones are steel. I was wondering why the short struts just weren't cleaning up and showing brass color.

This is the main wing surface. Not only was the paint to hide the hot glue, but it also hid some terrible soldering work. All of this needs resurfacing before I reassemble.






Today I was able to solder the nacelles back on their center strut. You can see the bronze color of them and also how mottled the surface is. I've suggested we get it media blasted to provide a nice, uniform surface after I put it all together. When I solder something it doesn't look like a mess.






I also soldered one vertical fin back on. I think it broke loose when I knocked the wing onto the cellar floor. Regardless, the tail metal is better than some of the other parts.





Here are all the struts after stripping, ultrasonic cleaning and some steel wool. You can see the steel vs. brass struts. I confused me at first as to why they looked so different. A test with a magnet solved my confusion quickly.






I'm going to strip the pain off the big parts in the garage so the smell won't get all over the house. The mass of some of these parts is so great that my propane torch had to heat them for minutes in order to reach soldering temperature at the joint. Patience was needed.

I'll start building the assembly fixture soon that will support the 50 pound wait of this beast. I've also selected some brass lamp parts to support the model on the bronze globe. Right now it was held with some bolts with pieces of copper pipe as decorative sleeves. I'm assuming the brass turned bushings and the threaded pipe will be able to support the weight.

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## Builder 2010 (Sep 26, 2019)

A lot has happened since my last post. I had the large parts commercially stripped using glass bead blasting to remove all the old paint, hot glue and most of the oxide. This prepared the model for soldering. I built the jigging that would hold the heavy pieces in alignment so soldering could proceed without too much handling. I started soldering the first set of main struts in place and ran into a brick wall. The bronze parts are so massive in relation to the pieces being soldered to them to make them almost unsolderable. I use "almost" because my problem was simply not generating enough heat to get the joint to solder temp before the bronze sinks all the heat away. I actually resorted to using two torches simultaneously; one a MAP torch and the other propane. This didn't do it. Then, one of the Heritage team members brought his acetylene/air torch and it's 2,700 degree flame was sufficient to bring the joint up to solder flow. I was still not satisfied. I talked to a tech service person at Harris Metals, a major solder and flux maker here in the USA and he suggested using 60/40 solid core solder and their high temp flux so it would stay put during the long heating session. I'm waiting for this new stuff to arrive.

Here's how the plane parts looked after glass beading; a far cry from how it looked before. At least now I had a chance to get it desoldered.






I constructed the jigging using 3/8" threaded rod, nuts and b body washers. The jig let me align all these heavy parts and not have to worry about them moving while I'm fitting up all these heavy pieces.






My first joints were decent, but didn't meet my standards.






The landing gear were missing. In the original installation, the landing gear were load bearing and held up the front part of the model. The rear was affixed with a 3/8" threaded lug. At some point after 1988, the gear disappeared and the model was supported with three lugs. I've re-created the landing gear using a hybrid of 3D printed parts and machined brass. I first was going to do the entire deal with 3D printing, but the long strut was too weak. So I designed the print with a 1/8" hole down its length which I would fill with a piece of brass rod. My first print had too much uncured resin in the bore and after hardening, formed a hardened plug that I attempted to drill out. The drilling out process destroyed that gear. For the next one, I drilled some tiny drain holes at the base of the strut so I could flush the recently printed resin out before hardening. This worked and I was able to insert a 1/8" brass tube down the entire length to reinforce it. I also reinforced the mounting lugs that would hold the gear to the fuselage wall by inserting a 3/64" brass rod into previously drilled holes. In the process of pushing this rod into a tight fitting hole I pushed too hard and blew the entire thing apart losing the reinforced strut. I still had the entire lower portion. I then made the struts out of brass and created the hybrid assembly. If this didn't work, the last resort was to print the parts in casting wax resin and have them investment cast in brass. We had a source to do this if necessary.






I didn't have much clearance to drill the 1/8" holes in the fuselage to accept the reinforced lugs on the gear legs. I was looking to buy and angle drill, but then remembered that I had a Dremel right angle drill attachment. I hadn't used it in years. Today it was worth the wait. 






I measured twice before drilling the holes in the fuselage to accept the gear. I knew that the spacing was accurate since, even though the drawings were very rudimentary, I was able to at least got those details correct.






The last thing I did was drill out the wooden shafts from old props from the engine fronts and then bored out the props to accept machined hubs which I'm now in the process of turning on the lathe. Originally, it looked like the plane didn't have variable pitch props, but later iterations showed Hamilton Standard HydroDynamic props and their distinctive hubs. I'm going to make something in between. I was concerned that my drilling of the props could destroy them. I hand drilled a centered pilot hole and then used the drill press to open it up to a #2 drill. I was careful and was rewired with clean centered holes ready for the new hubs.






Once I get the new solder and flux, work should proceed fairly quickly. Until next time...


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## Builder 2010 (Oct 2, 2019)

I machined prop spinners and then covered them up with bronze paint. I also ordered lower melting temp solder and a high temp longer lasting flux. The flux arrived, but the solder has yet to arrive. I 3D printed a fixture to hold the main struts in place and at the correct angle so I can solder them more easily to the main wing.






After painting these are set aside until the end of the build.






I designed the fixture directly over the scaled plans I found. I did the design in SketchUp. My first version was too wide and I found that the brass struts are narrower than the steel ones. The steel struts are 1/4". I think they are made of common steel key stock used to make keyway keys in machining. The question I have is were the originally struts developed in 1937 steel or were they substituted in a rebuild sometime later. I know someone did some sloppy desoldering in the past. I had to refine the design to accommodate this variation. The UV resin is thermoset and will not soften as the metal heats up. It will most likely burn and I don't intend on getting the heat anywhere near it. I only have to use it two times.


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## Airframes (Oct 4, 2019)

Lots of dedicated work going on - great job !


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## Wurger (Oct 4, 2019)

Agreed. Well done so far.


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## Gnomey (Oct 4, 2019)

Great work so far!


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## Builder 2010 (Oct 7, 2019)

Thank you. With the new solder (60/40 solid core) and the new higher temperature flux (Bridgit) and the acetylene/air torch I'm able to get solder to correct temperature and solder parts together. I used the fixture and got the main struts soldered to the big wing at a reasonable position so they'll successfully mate up with the smaller lower wing. I fixed the joint in the right engine nacelle so it's more correctly seated. The new torch is has some many more BTUs than the propane that instead of five minutes (or more) it now takes 30 seconds to get to heat. I then started fitting the missing engine support struts. I'm making these out of 1/8" square brass rod. I also substituted brass bar stock for the steel struts. I didn't like how the steel struts were soldering (or not soldering).











The engine struts were pinned to the engine. I'm doing this also. It helps stabilize the joint which is coming at an acute angle. I needed to cut and fit the outer two struts to measure for the third one that goes diagonally between these two. I couldn't measure it without simply building it and just fitting it up in real time. None of my drawings show details about these struts but they're there in photos of the plane and there's soldering residue in the previous strut's positions.






Once I get these struts fitted I will invert the plane and realign the filtering so it will be right side up and solder the struts to the lower wing and the long diagonal that runs from the main wing to the fuselage. One of those was also missing and I have brass for that too. I have one more work day and then we're off to Philly for a wedding. We'll return next week. I'm confident that the rebuild will be done by the end of the month.


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## Builder 2010 (Oct 8, 2019)

It was ridiculous trying to hold those struts still while I could solder them to the nacelles. I tried welding clamps, iron wire, and was unsuccessful. I then took the engine assembly off the plane and again attempted to use wire. Didn't work. Finally, I made a metal fixture to hold the three struts at the correct angles and position so I could solder them. The pins kept the top joint stable enough. It took all the heat I could generate to get those 1 pound bronze casting hot enough to melt the solder correctly.









I cleaned up the joints using cutters in the Dremel and then into the ultrasonic cleaner. I put the engines back on the wing and the angles are good. Next week I will solder the other end to the wing. This should be easier, but I'm not holding my breath.









Here's another view showing the solder joints themselves. Not pretty, but it will be painted. Thank goodness!


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## nuuumannn (Oct 9, 2019)

Mate, you've got your work cut out for you there, and your perseverance is admirable. Enjoying your commentary on welding. Looking foirward to the fnished product, which I'm certain you'll get right.


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## Wurger (Oct 9, 2019)




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## T Bolt (Oct 9, 2019)

Some very nice work


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## Builder 2010 (Oct 18, 2019)

Thank you! It's a totally different modeling experience than what I'm used to. It's serious metalworking. The fact that 47 years ago I was a metal shop teacher is a good thing. I'm surprised how many things I remember even though I haven't used them for almost 50 years. Example: knocking off the sharp cutting edge on a drill when cutting brass, copper or bronze so the drill doesn't hog in and jam. 

All the engine struts are in place and the engines are securely soldered to the main wing. I built and installed the V-sharped mid-braces using 2-56 allen cap screws and only broke one 2-56 tap. It caused me to make an emergency trip to the hobby shop to get two more of them. I re-soldered one of the floats that was hanging loosely. Finally, I was able to drill out the old threads that held the mounting bolts with a "Q" drill and tapped them for an NPS 1/8-27 lamp tube thread. There Q drill was just big enough to totally remove the old threads and provide a clean surface for the new threads.

Using screws relieved me of the worry of de-soldering the struts that were right next to the mid-braces. The tap broke on the second of the four holes. I had completely tapped the hole, tried the screw in it and it didn't go deep enough. Instead of shortening the screw, I attempted to tap the hole deeper. When trying to back out the tap it jammed. Instead of freeing it, I broke it. I drilled another tap drill hole near the old one and re-tapped successfully.







I think my finger got into this picture.






I'm going to take the fuselage with these standoffs to the airport and fit it to the globe to make sure it goes on easily. The fuze weighs 20 pounds and is fairly easy to manipulate. The total plane weighs about 50 pounds and will be much harder to handle. I wanted to check the mounting before attempting to hold the monster over the globe 8 feet in the air. Note: one of the standoffs is upside down. I just dropped them on to see if the threads were okay.


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## Builder 2010 (Oct 21, 2019)

Couldn't take the fuselage to the airport today for the trial fitting, but I did make some more progress. Got the fuze situated on the build table and trial fit the main wing on top. I also clamped and soldered the tail back on. The tail was one part that hadn't been separated in the great fall. That responsibility fell to me. I had the wing on a couple of stools in the shop. It was behind me when I was working on my little lathe. I rolled back my desk chair and knocked the wing onto the concrete floor. The noise was horrendous and the tail was separated. Luckily, it didn't deform badly and I was able to refit it and solder it back together today. No harm, no foul. One of the struts was slightly out of position and I corrected that too.

I soldered this strut about a 1/4" to close to center and a little bit too far forward. The other struts lined up beautifully.






I modified my fixture to support the tail during the soldering operation. The tail has some 3/64" bras wire details that I need to replace. These will be easy compared to all the massive parts that needed to be reattached. Notice the model is actually supported by the fancy brass standoffs and lamp pipes. I drilled the base board so they would sink to the proper depth. I then leveled the model and level the main wing. Lines up well.






With the acetylene air torch soldering has become much more predictable. It's no longer a worry. The joints are coming out relatively clean and well bonded. The repositioned strut now joints the other at the bottom end as it should.






I used some small C-clamps to lock the tail down tight, applied flux and was able to refuse the previous solder. I just had to add a little bit more to fill some more voids. There are a couple of spots that will need some filler before painting. Two are seen in this image. They're from the two pins that hold up the nacelle tapered end. I cleaned off the wing with baking soda and water to neutralize the acid flux and then went over it with some 240 grit abrasive on an oscillating multi-tool.






With a successful trial fit I'm quite confident that the entire plane will come together as it should and be quite strong. Once I got the soldering process lined out the project became must less onerous.


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## Airframes (Oct 22, 2019)

Nice work, and I hadn't fully realised how big it is. Must be very heavy !!


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## Builder 2010 (Oct 22, 2019)

It has a 41" wing span and will weigh almost 50 pounds (22.7 kg) when it's all assembled. It will be reasonably strong, but dropping it on concrete would re-kit it all over again. The team for whom I'm doing the work is very pleased and it's exceeding their expectations (mine too) since considering where we started it did seem almost too much to think it could be close to as-built condition. I would love to know who built it in 1937. The dome is about 1/2" thick bronze and a member of the Bowman Field Heritage Foundation Team and I got it into position. I had to drill out the three existing holes and we got it to slip into position. It was much easier doing this with only a 20 pound fuselage without the 30 additional pounds of complicated soldered assembly hanging on. This is over 7 feet in the air so it took both of us on ladders to work up there. I thought ahead and ground negative rake on the drill's cutting edges so it would better cut the non-ferrous metal. It kept the drill from grabbing on exit and kept it from breaking my arm. Now it's back the shop to combine the main parts into a single hole.

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## Builder 2010 (Oct 24, 2019)

Today was a big deal day. I finished putting the last of the support struts on the fuselage. The wing end is soldered. The fuze end was fastened with a 2-56 cap screw into a hole that I drilled and tapped. These six center struts were strong enough to support the fuselage weight. I was able to lift the 50 pound beast up from the build table and set it on the arms of our old knock-off Eames chair, but I am not able to lift it, hold it and position it onto the build table right side up.






To do the great reversion I enlisted the help of my daily-growing, 15 year-old grandson. He came over tonight and we were able to turn it and set it properly onto the build table. I've started doing the final cleaning and finishing in preparation for painting. I also added the hanging brace that suspends the tail of the fuselage from the tail booms. This piece is steel wire and replaces another piece of steel wire. We had to cut that wire to release the fuselage from the wing when we removed it from the memorial. All of the rest of the struts (the hot glued ones) had let go and only this wire was holding the mess together. I was gratified that the piece I made ended up being the same length as the wire it replaced indicating that the geometry was still pretty good. There are only four or five more solder joints to finish the job. There are some non-load-bearing cross wires that go between the tail booms. I'm going to epoxy these instead of soldering because of their proximity to the hanging brace.






Now that it's sitting correctly I find that one strut on one side is a bit long (about 3/32") and on the other side it's a bit short. It wouldn't be hard to de-solder and move the mounting position, but I can't do that with the model in this orientation. It's hard enough to solder this model. It would be near impossible to solder upside down. So I'm going to trim the long one in situ, and either shim the other with a piece of brass or just tie it to the small wing slightly separated from the other strut. I epoxied the landing gear so they're ready for paint too. I'm painting them separately and will epoxy them to the plane when it's actually on the dome. They're delicate and will most certainly be destroyed when we're attempting to maneuver the model into position. The props also will go on at the end.


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## Builder 2010 (Oct 25, 2019)

The S-38 is mechanically done. I tied the main struts to the small wings. I fixed the slight length deviations by trimming the long one and adding a little chunk of brass under the slightly short one. This was a much easier solution than turning model over again, de-soldering and re-soldering the errant struts in a different position. I also added the cross wires on the tail booms and with that the model was complete. I did some more heavy cleaning. There's still some more to do before painting, but I need to get the right weather since it has to be either outside or in the garage.






Props are not glued in. That'll wait until the model is in final position on the memorial.






Finally was able to make respectable solder joints. I guess I need to do another to use my newly refined skills.









The model is very heavy, but quite strong. It will last a long time as long as no one drops it from seven feet in the air onto concrete. With the new mounting system I'm employing, it will not fall down.






It would be nice to keep it natural bronze, but the landing gear are going to have to be painted. So I'm painting the whole thing.









The Bowman Field Heritage Team is very happy with the outcome and they really didn't think it would happen. I wasn't sure it would either. They're planning a big deal for the memorial re-dedication, including newspapers and a presentation by me at the Louisville Filson Historical Society.


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## Builder 2010 (Oct 29, 2019)

Here are some more (better) images of the completed project. The model is going to be left in natural metal with just the LG painted a bronze color to match the metal. My sister, the antique dealer, suggested to NOT clear coat the model, but let it age naturally.

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## michael rauls (Oct 30, 2019)

Beautiful.


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## Wurger (Oct 30, 2019)




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## Builder 2010 (Oct 31, 2019)

Thanks all. Yesterday, I had a professional photographer shoot a lot of pictures with proper lighting. In some of the pictures I temporarily put on the composite landing gear and the stress fractured one of the hubs where the brass cylinder is epoxied to the resin. This required me to build "landing gear version 3.0". I machined a steel hub out of key stock, drilled the wheel 1/8" to accept the hub and soldered the existing brass strut into it. It was the first time I was able to use my newly acquired four-jaw independent chuck to hold the rectangular 1/8 X 1/4 stock. This was a sweet little project and will work great. I was concerned about the integrity of that resin hub and now my worries are over. I trimmed the extended pin on the cylinder legs.






The hub goes deep inside the wheel and has a lot of meat around it. 






I bought the 4-jaw because I was planning on using it to shape the struts, but didn't. But I did get to use it today to turn the key stock into the wheel hub. It's been 45 years since I had to center a 4-jaw. It's fun.






I also ground a slant on the upper end of the cylinder so I could more easily rock it sideways to get the gear legs into those holes. Fits very nicely. With the stronger hubs I think the gear can be put on in my shop. The hinge pin is simulated.


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## Builder 2010 (Nov 4, 2019)

A couple of fancier pictures and the painted landing gear.








The "Artist" with his work.






In the above, the resin part of the landing gear weren't painted. I did that today. I prime coated it with Tamiya white primer, then air brushed a mixture of Tamiya Gold, White and Clear Red. Didn't like the result. It was too tan and had no life. I then overcoated it with Venetian Gold, a nice rose gold shade (almost copper) that was better. I brush painted it and didn't worry about making it too smooth since the rest of the model is sand cast and has a rough finish. I then aged it a bit with AK dark wash. After removal of the excess, I think it works.









From a distance, it looks better. The model will be over 2 meters in the air and you can't get very close to it, so it will not be viewed this close…ever. From this distance and light level you can't see much difference.

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## Airframes (Nov 5, 2019)

Excellent !
You've done a superb restoration job on this - very well done !

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