Fiat G.55
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G.55 Centauro


Role Fighter
National origin Italy
Manufacturer Fiat
Designer Giuseppe Gabrielli
First flight 30 April 1942
Introduction 1943
Status Retired
Primary users Regia Aeronautica
Repubblica Sociale Italiana
Argentine Air Force
Royal Egyptian Air Force
Produced 274 (wartime), 75 (postwar)[1]
Unit cost
L. 535.000 (L. 1.284.000 for planned 2.400 aircraft)[2]
The Fiat G.55 Centauro (Italian: "Centaur") was a single-engine single-seat World War II fighter aircraft used by the Regia Aeronautica and the A.N.R. (Aeronautica Nazionale Repubblicana) in 1943-1945. It was designed and built in Turin by Fiat. The Fiat G.55 was probably the best type produced in Italy during World War II,[3] (a subjective claim also frequently made for the Macchi C.205 Veltro as well as for the Reggiane Re.2005 "Sagittario") but it did not enter production until 1943.[4] when, after comparative tests against the Messerschmitt Bf 109G and the Focke-Wulf 190, the Luftwaffe itself regarded the Fiat G.55 as "the best Axis fighter".[5]

During its short operational service, mostly under the Repubblica Sociale Italiana insignia, after the 8 September 1943 armistice, this powerful, robust and fast aircraft proved itself to be an excellent interceptor at high altitude. In 1944, over Northern Italy, the Centauro clashed with British Supermarine Spitfire, P-51 Mustang, P-47 Thunderbolt and P-38 Lightning, proving to be no easy adversary.[6] Italian fighter pilots liked their Centauro but by the time the war ended, fewer than 300 had been built.[3] For comparison, the Germans produced 34,000 Bf 109s.

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I became interested with this Italian Fighter plane after reading the Squadron publication on the Regia Aeronautica. I was really impressed by its lines and by its actual performance, and the fact that so few actually were built and put into operation.

I've seen some really nice PSS ships done of its close cousin, the Machhi 202 and they seemed to fly really well, so I thought this is an opportunity for me to see if I could pull off a scratch build. The Fiat G55, the Macchi 202, and the Reggianne 2005 were all close cousins of the Serie 5 group. The Italians had a design competition with aircraft to become a primary fighter, all of which had similar design parameters. The Fiat was the winner, but took so long to construct, especially compared to the German ME109, that it really never made an impact, as Southern Italy was taken over by the allys in 43-44.

I started things off by finding a 3 view on the internet. I took this on a flash drive to Kinkos and had it blown up till the wingspan was 50".

This took a couple runs to get it right, but the extra printouts are nice to have, because you can sacrifice them when you make full size templates to create the plug.

The side view is laid out on a 3/32 piece of plywood, and bandsaw, sanded to the outline. I then made 2 each of the vertical stations, which get glued on to the central stringer at the A, B, C, D, etc stations on either side. I then added blue foam between the station positions.

I had some good pictures, but as luck would have it, my computer got toasted, so I lost the ones that weren't backed up to my external drive. If I find them somewhere in the damn internet cloud, I'll put them in here.

IMPORTANT DISCLAIMER:

What I am documenting is just what I did. Its not necessarily the right way, the best way or the only way....so take it all with a grain of salt because what worked or didn't work for me may be totally different than your experience. The process of getting a flying model out of just a 3 view drawing is what interested me the most. I like to build and this seemed like a challenge, that anyone who has been in this hobby as long as I have, needed to accomplish...just for the hell of it.

After I added the foam between the verticals, it was time to rough carve the foam down to the plywood outlines. I used a surform file and it ripped away super fast...way too fast...as I would find that I had hogged away the foam too low between the vertical stations....

My only choice at this stage was to glass the rough outline and build out on the low spots with bondo, and then sand back down again to the shape I wanted....eeechhhh.

Its at this time that I needed to figure out the wing saddle too. So I used my Compufoil program to generate some templates to cut my wing. I'm using the standard RG14 @ 7.5 thickness airfoil. This is a fairly fast and easy to build section and has been proven here in So Cal to be pretty effective in a variety of lift conditions. I built a section of the wing up so I could make the wing saddle match the airfoil.

So here is the inner wing panel for the scale wing. This was needed early on to match the airfoil to the fuselage saddle. I used 1/64 ply to smooth the saddle area and extend the bottom of the wing/fuselage fillets.

The fillets took a lot of fiddling with. I wanted them big enough to smotth the wing transition, but not so large that they would be a bear to get the fuselage out of the mold.

I'll be honest. I screwed up the initial shape of the plug so much, that I had to fight the urge to just throw it away and start over. I ended up putting it to the side in my work area for about a year. My biggest issue with it, was that I had "ovalized" the fuselage, especially around the nose/spinner area. I made the nose by cutting a circle in 1/4" plywood and then mounting a 1/4-20 bolt to the center of that, and adding a 3" balsa block to the front of that unit. I then put the 1/4-20 bolt in the chuck of my cordless drill and spun it while I ran it against my belt sander to create the rounded spinner. That worked great, but I over sanded, shaped the fuselage prior to glassing it, so instead of round cross sections, I had ovals. I glassed the plug with about 3 layers of glass -1-2oz and 2-6oz using epoxy. Polyester doesn't like eps foam and will melt it pronto.

The only way to deal with this was after glassing the ovalized plug was to then start adding bondo to bring it back round.....this had to be done to the nose area and all the shallow valleys that I had oversanded between the plywood vertical formers. God what a lot of work. To check roundness in the nose, I cut out plastic circles from different size lids in various diameters and would add, sand and check progress about 1000 times until it looked OK. I also made a mistake in adding the reliefs for the top side machine guns too early. I had to totally fill and re-bondo these two small valleys about 4 times to get them fairly scale size, symmetrical and looking ok to the eye.


The other thing I checked at this stage was that the wing saddle and the horizontal stab could be set at 0-0 incidence and that the model would fly in a nice slightly nose down position when the incidence was set correctly. Things lined up nicely. After setting the incidence meter to level on the wing section with the fuselage sitting on it, you could use the point on the end of the fuselage to draw another line with a level at 0-0 forward to the nose.

At this point I realized that to make a plug, you have to compromise scale outline with artistic lines and practical limits of molding....so its as good as I could do it, and still get it done. So many projects just die because the builder isn't happy with one thing or another...I've been there done that about a million times because I enjoy the challenge of building stuff.

I used Krylon Industrial high build gray primer. This stuff is really good as it dries quickly, and sands nicely without and gummy build up on the paper. Along with the primer I use red spot putty, that fills cracks and pinholes really nicely and feathers out smoothly.

During the early stages of the plug shaping, I went back and forth on adding details like intake cowling, exhaust headers, some panel lines, etc. I also was going to mold in the vertical stab, fin and made a fin that I was going to add to the plug.

After all the work to get the plug halfway nice, I said to heck with it. I will make a couple small molds for the ventral radiator, intake cowl on the fuse left side and exhaust headers and these can be added later. I'm figuring that there will be a sport set up...more similar to the SlopeScale ships which are really fast to build and practical by most guys if they are interested in this thing. It will be a hell of a lot easier to mold also. I went with a platform for the vert. fin and the fin will be made up of 3/16 balsa and basswood in the usual fashion for these kind of ships.


But I did want some window frame outlines so I got some sheet wax from McMaster-Carr and used it to create these. The wax has an adhesive backing and is thick enough so you can put it where you want the windows, then build up the frame areas on the fuselage by spraying several coats of high build primer. This went OK, but its a little rough because it was really hot when I pulled the wax off, and things got "gummy" so the lines aren't quite as sharp as I would've liked. This took some detailed cleaning to make decent, but its "gud enuf"

After this stage it was time to get some shinny paint on the plug! I used Black Krylon rattle can Industrial acrylic enamel. This stuff dries quickly and has a super high solids content, but you really have to watch your time intervals between coats. You can spray a second coat within 1 hour, or you have to wait for 48 hours. If you sand it between coats, you have to wait 48 again....Yeah I learned the hard way.

Krylon actually had pretty good support, and I was in contact with them because their product labels didn't address multiple coats on this stuff. They recommended their acyrlic lacquer, but I thought I could power it out with this stuff, and I did with good results.

After 3 coats, with sanding to deal with a couple runs here and there, I had sufficient coating thickness to wet sand and then compound polish/wax to a nice gloss.

I had some 3/4" melamine board scrap left over from a cabinet project that I used to make the parting board to make a mold.

I outlined the plug on the board and then cut out the opening to position the plug at midpoint in cross section. You'll need to add some feet to the bottom of the board to hold it up off the work surface and let the plug go to half on the board top surface.

Of course, I cut a bit too much and ended up having to add some scrap would to plug the opening to about 1/8". After supporting the plug in the opening, I used never hardening model clay to fill in the gap around the plug and the board. Take your time doing this and make it as clean and sharp a transition as possible..you will pay for it later if not. I use old credit cards cut to different angles as putty knives, scrapers to get the clay smooth and tight. You don't want a radius to the plug, you want a 90 <, or your parting line will not be sharp where your seam is on the fuselage halves.

After you feel really really really good about where the plug is located and everything is sparkly clean and shiney, its time to shoot the PVA mold release. Don't even think about trying to use a brush with PVA on a large surface. Brush on may work for little parts....but not for something this big.

I use a really cheap siphon gun that I got a Harbor Crappy Freight. I get decent results from it, but I only use it on PVA. If you get one of these Chinese made units, do yourself a favor and strip it down, polish the needle and check the orifices to make sure they are concentric. After I did this, I got OK results from this sub $10 masterpiece.

PVA gets 1 mist coat....needs to dry at least 15 minutes before next flow coat, which needs to dry minimum of 30 minutes, which needs to dry at least another 30 minutes before doing any epoxy work. The PVA release works really well in conjunction with a parting wax, but its not fast, that's for sure. PVA is a little tricky to get to flow without leaving runs and puddles. If this happens, its easy to start over by rinsing everything off with water, but you loose a lot of time.

After making sure that the PVA is totally dry and covers the entire board its time to glove up and make the first half of the mold. I've used this room temperature epoxy tooling coat by PTM&W on a couple molds and have really been happy with it: http://www.ptm-w.com/ptm-w-products/...ts.html#PT1414
It has a high silica content, really clings to vertical surfaces and is fairly cost effective at about $60 a quart kit shipped to my door. It takes the entire kit for a mold this size. If you are not careful, you might need to use more than 1 qt. You really have to mix the hell out of this stuff and it is thick, so cup up on the coffee and plan on a good 5 -6 minutes of whirling and scrapping to mix the hardener and epoxy thoroughly. When done, it is evenly blue in color without any streaking. If you need to stretch it, you can make temporary dams of blue foam hot glued to the parting board to contain the coat on your board and plug. I just let mine run. When applying it, let it run down a stick onto the mold, concentrating the even pour on the edge of the mold where it meets the parting board. You will see a million air bubbles and these are your enemies. I go after these with a pin and pop them as I see them....this is good for about 30 minutes of tedium.

When the tool coat is set up, but still tacky, it's time to start laying on the fiberglass that will reinforce the tool coat and give the mold strength. I used 1 layer of 6 oz and about 8 -10 layers of 10 oz, maybe about 5 yards of material overall. I used West Systems epoxy because it is readily available and easy to mix with the pump systems. It took about 1.5 qts or close to $100.00 in epoxy for the entire mold.

When I was laying up the thickness I was aiming for about 1/4 minimum at the surround where I would be bolting the mold halves together. I used a lot of strips around the flat edge to get this thickness. One of the best tools I have is an inexpensive Black and Decker electric scissors. This thing flies through fiberglass and allowed me to cut strips and sheets really easily and quickly.

I used 1.5" cheap" chip brushes that I cut the bristle to about 1/2 length to stiffen them up and push the epoxy into the glass with a stippling type motion.

Nice build. Subbed.

Al

Thanks _Al! I'll keep updating the build as I go along...I didn't want to besiege the guys on the Slope Forum with this, but I thought it would be interesting to a few folks, so here it is.

After letting the fiberglass harden overnight, I popped the 1st half off of the parting board without any issues.

It was time to go for the 2nd half of the mold.
I PVA'd up the plug and the face half of the 1st side. The parting board held everything in good enough position. After doing the 3 coats of PVA, I laid down a coat of the tooling epoxy. After letting this set up until it was just sticky on the surface, I began building up the fiberglass reinforcements as I did with the first half......
Whistle while you work........

I trimmed up the mold using a segmented carbide blade (a couple actually!) on my Jigsaw. That Silica loaded tooling coat is really hard and tough to cut.

After trimming it was time to split the mold. I started using a really thin screw driver, then used credit cards to hold a gap. Once I had a couple credit cards holding a gap, I used a plastic shim that is used to set doors and windows. These are tough and have great wedging ability. After a little working of the tool, the mold popped open. WOOT!

The last thing to add before actually laying up a fuselage was legs on both sides, so the mold would be stable lying on any of its 4 sides , and then drilling the perimeter for 1/4-20 machine screws.

I hot glued the nuts and washers in place so I can use a drill with a screw driver head to zip the screws on or off in less than 30 seconds.