1/18 scale Tervamaki Engineering JT-9T autogyro

Nick_Karatzides · Skill Level 3

1/18 scale Tervamaki Engineering JT-9T autogyro

Nick_Karatzides · Skill Level 3

CHAPTER I - Basic airframe skeleton construction

Following the 1/18 scale printed diagrams and using just a sharp blade and ZAP superglue, it took about 60 minutes to build the basic airframe skeleton. The tiny gaps between the skeleton connections, were filled with Humbrol modeling putty, applied with an old brush. In order to make the putty liquid and let it spread naturally and fill the tiny gaps, I mixed it with laquer thinner. Because the laquer thinner is volatile, the liquid putty mixture took about 45 minutes to get fully dry and be safe to sand - carefully ofcourse. If you follow this method, be sure that you mix the laquer thinner and the modeling putty into a metal or glass plate / canister, because the most plastic materials cannot stand it and melt. For this reason, keep in mind to use just the essential laquer thinner quantity, in order to remain the mixture in liquid form, as it is presented at the following pictures.

http://img265.imageshack.us/img265/5679/image0016.jpg

About 45 minutes after nitro resolvent and Humbrol putty liquid mixture applied with brush on the skeleton to fill the tiny gaps between the connections, it looked to be fully dry and safe to sand it. As soon as that was done, the skeleton was hanged by a string and airbrushed with enamel mat white color as a base coat. Cockpit floor, wheels etc made while waiting the putty to dry, were also spayed with base coat.

http://img233.imageshack.us/img233/2520/image0017p.jpg

http://img265.imageshack.us/img265/4757/image0018.jpg

-- Edited by Nick_Karatzides on Wednesday 4th of November 2009 11:41:24 AM

-- Edited by Nick_Karatzides on Wednesday 4th of November 2009 02:05:51 PM

Nick_Karatzides · Skill Level 3

CHAPTER II - Diesel engine building & painting

Setting as a task to build the model in a way that airframe look like cutaway side opened with cockpit and engine bay details visible, I should also leave the engine's cover opened. that ofcourse means that a diesel engine building from scratch is something I couldn't easily avoid. Using plastic card, sprue, metal wire and unidentified parts found in the sparebox, here is my effort to build a realistic 1/18 scale engine.

After connecting with superglue the main elements, the electric cables and oil or diesel lines etc on engine's shape, I airbrushed it with enamel mat white color as a base coat, using high air pressure and spraying from distance to develop a pore surface and help silver & aluminum paint establish easier on plastic or metal engine's parts. As soon as the enamel mat white color seemed dry enough, a mixture of silver and aluminum paint sprayed on the engine and let about 24hrs to dry before trying to wash it with darker colors.

As I personally believe that following simple techniques and sometimes unconventional methods, result in superior effects, I usually do not use enamel or acrylic paint to wash, because I feel risky when applying the paint mixture and let it run. I prefer an easier technique that can be undone if the results are poor - that makes it the perfect technique. I use hard chalk pastels to wash (NOT oil pastels). The hard chalk pastels, look like a teacher would use on the blackboard in school. Do not use the soft oil pastels that artist use to draw on paper. The hard chalk pastels are easy to find in a variety of colors into your local art store or maybe Wal-Mart if in US or ASDA if in UK.

To do the wash, I use an X-acto knife, a small metal or plastic container, an old brush, dish washing soap and a bit of water. Begin by scraping some chalk powder from the side of the chalk pastel stick, carefully put this chalk powder into the small container and add a tiny amount of water and stir. It is important to add a tiny amount of water in order to make the mixture look like mud - not like soup! For this reason, I use a syringe to add just few drops on the hard chalk pastel powder and I stir using the old brush. Because the chalk powder doesn't mix well with the water, a drop of dish washing soap is needed to break the surface tension of the water and also acts as a "glue" to help the chalk powder stick to the model.

Once the chalk is fully dissolved into the water/soap mixture it is time to "paint" this mixture onto the model's engine. "Painting" the mixture is simple - just apply it anywhere it is needed to darken recessed detail. The mixture can be applied carelessly, because any mistakes can be completely removed and redone. Once the chalk wash dried, I rubbed off the high spots with a slightly damp dry (not wet) Q-Tip cotton swab (Kleenex papers can be also used) and I wiped the dark color from the areas should be light & shinny. The high spots were cleaned to the SNJ bare metal finish and the low spots were left black. I did the chalk wash on the engine in under 30 minutes which makes it a very quick and effective technique. You can also read about this into Steve Bamford's article, by clicking HERE.

Some of the wash mixture is re-applied and the wash being wiped completely out of the narrow points. If you follow this method, it is adviced to not rinse out the wash container till you are finished this job. You will probably be touching up certain spots a few times, so it helps if you're not mixing up a new chalk mixture each time because you kept cleaning out your container of the chalk wash mixture. As soon as I paint the electric cables, the oil or diesel lines etc, I repeated the the wash process with lighter colors where needed. Using micro cotton batons found into cosmetic shop for less than 1£, I applied some red, orange, purple & brown chalk pastel powder on the engine's chrome excaust, to make it look overheated. I repeated the weathering process until it satisfied me and finally I sprayed a clear coat to seal the chalk powder on the engine.

The scale model building, cost me almost nothing and took about 2 evenings work so far. Some pictures of my secret hideout / hobby room while scratchbuilding the 1/18 scale JT-9T autogyro model. Click on the first image to enlarge hi-res 180 degrees picture.

-- Edited by Nick_Karatzides on Friday 2nd of October 2009 01:53:57 AM

-- Edited by Nick_Karatzides on Wednesday 4th of November 2009 02:07:25 PM

-- Edited by Nick_Karatzides on Wednesday 4th of November 2009 02:08:07 PM

Nick_Karatzides · Skill Level 3

CHAPTER III - Instrument panel & cockpit construction

The original Tervamaki Engineering JT-9T autogyro instrument panel is not what you would call as "glass cockpit". Actually it does only have just the basic instruments in cockpit to provide the pilot with information about the flight situation, such as height, speed and attitude. Since the JT-8T autogyro is not designed to fly in conditions of poor visibility or night, the main information is available from visual reference outside the aircraft. Of course, many pilots who are lucky enough to own an autogyro, they might add more sophisticated equipment such as CFT screens, HSI - Horizontal Situation Indicator to follow VOR signals, GPS screens, VHF/UHF radio, replace the heading indicator by a GPS-driven computer with wind and glide data etc. The basic instrument panel is consist by:

I started by cutting the main panel shape in plastic and drilled the gauges positions. Using the Corel Photo Paint, I created a colored sketch of the instruments, copy & paste the image into a MS Word new file and print it on a simple A4 page. Meanwhile, I add some detail on the instrument panel, such as rivets made by streached sprue inserted in drilled out holes, knobs etc.

Using styrene plastic card, I cut the basic lines to form into the two simple seats. The dimensions are based on the basic 1/18 scale JT-9T two-seat trainer blueprint line diagram as seen HERE. On the real JT-9T autogyro, these simple seats are made of hard plastic, fiberglass or even wood sheet and buckram covered home made pillows are placed to provide comfort. These seats are fixed on metal rails, running across the cockpit floor connected with main skeleton, to ensure seat's secure installation.

For many years, I was used to form aircraft seat pillows with Milliput epoxy putty, which is popular among modelers and also useful in countless household & restoration applications. But, while I was in a supermarket last week, I found the following item and I thought that it could be nice to try it and start experiment with this material. It's an air-drying modeling clay ideal for scale modeling and shaping. According to the instructions, it can be easily formed into shape, become solid rock withing few hours, re-filled or sanded if neccessary and painted or lacquered. That sound quite good to me and similar to the well known Milliput epoxy putty, with the only difference that the 500g air-drying modeling clay pack cost only 1£, instead of 100g Milliput epoxy putty which cost 5£. That makes the new found air-drying modeling clay, about 25 times cheaper than Milliput epoxy putty and that's a good reason for me to give it a chance.

Grabbing a small quantity with a metal spatula and applying the air-drying modeling clay on the seats, it felt too soft and very easy to spread the material nicely to simulate pillows realistic way. I didn't want to care too much and try forming and shaping the clay, because I was planing to cover the sculpted pillows with wet soft paper to simulate the buckram covered pillows. After all, I had no idea how much available time I had, before the material start becoming hard and difficult to handle.

-- Edited by Nick_Karatzides on Friday 2nd of October 2009 01:57:33 AM

Nick_Karatzides · Skill Level 3

Toilet paper is not only for the obvious purpose but can also be useful for scale modeling. I used ordinary toilet paper, cut it to shape and dress the seat pillows made by air-drying modeling clay, to look more realistic and simulate the buckram covers. Water based white glue for wood, which becomes transparent when it dries, is just the right for the job. So, I opened a 500 grams canister bought for 2 only, pick a small quantity, add just few drops of water with a syringe into a small metal container to make the right mixture and finally I formed the paper on the pillows with a wet brush, into the desired shape. Because the mixture is enriched with water based glue, the soft toilet paper becomes hard when the water dries.

-- Edited by Nick_Karatzides on Wednesday 4th of November 2009 03:30:03 PM

Nick_Karatzides · Skill Level 3

CHAPTER IV - Right side fuselage construction

As I said at the beginning of this thread, I decide to make the JT-9T building look more interesting and show the model in a way that airframe should look like cutaway side opened and let cockpit detail be easily observed. THIS artistic diagram gave me the idea and that would be a nice opportunity to present my way to do it. To do so, I decide that a solid rock one-piece "negative image" cast of the right side fuselage should be made of plaster first and then build a right side solid replica made of polyester, epoxy or resin. This replica - virtual fuselage, would be the basic line to create a thin right-to-scale fuselage surface.

My local newsagent, usually wraps my newspaper and magazines into a plastic bag, which sometimes I use to collect the trash. This time, I decide to use the plastic bag in a completely different way. I cut free-hand few pieces of plastic, keeping in mind to make them longer & wider than the autogyro scale model dimensions. Using duct tape, I stretched the plastic bag across the airframe, in a way to simulate the full right side and half bottom fuselage surface, trying not to leave any visual wrinkles or marks.

Nick_Karatzides · Skill Level 3

I add some grams of plaster powder and few drops of water with a syringe into a soft rubber cup to make the right mixture. Materials like plaster, start as a dry powder that is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after drying and this characteristic make plaster suitable for the job. Keep in mind that adding salt into wet plaster mixture, reduce the plaster's hardening time and adding vinegar into wet plaster mixture, extend the plaster's hardening time. When the first layer of thinned plaster applied on the plastic bag was dry and hard enough, a second thin layer of plaster was applied to form a basic strong cast. The basic idea, is to let the plaster follow the airframe details, accurate on scale and as thin as possible trying not to apply extra stuff where is no needed.

Nick_Karatzides · Skill Level 3

Found at my local supermarket and got for only 0.5, the following modeling clay for kids. Some scale modelers, use this material to border camouflage patterns while airbrushing. I pick a piece, mold it into snake alike formation and placed it across the airframe to border the wet plaster flow - yellow color for up and purple color for bottom airframe side.

When I finally enclosed the right half JT-9T scale model into plaster, I left it few hours to get harden in order to be sure that the cast wouldn't break when I would try to remove the scale model from inside. Meanwhile, I took the soft rubber cup which I used to make the plaster mixture, squized it to break the last hardened plaster left inside, so it would be easier for me to clean it afterwards and prepare it for any future mix. That's the reason this soft rubber cup were used for.

As soon as the plaster cast was dry and hardened, I removed the the modeling clay I used for bordering the plaster flow and pull the enclosed JT-9T scale model airframe away, gently. Brushing the area with an old tooth brush, I removed unwanted dust or small broken plaster pieces.

Johnson's baby oil or similar is well know to anybody who have children in house. If you don't have children yet, ask your girlfriend - all girlfriends have a tiny bottle in their cosmetics drawer. If you don't have a girlfriend, close this web page, shut down your PC/laptop and get your feet out of house to meet one! Scale modeling is nice, but feeling a nice female next to you is much better. Continuing with the project, thin layers of vaseline based mixtures can be also used instead of baby oil to apply with a soft brush as a segregative material between the plaster cast and generous quantities of polyester filler applied on the plaster cast.

The specific polyester filler I used, comes with the proper catalyst which provides a solid rock build and approximately 3 to 5 minutes time window to form it into shape. I prefer to use epoxy putty or polyester filler with fiberglass grains for special purposes, because:

It becomes solid rock within only few minutes or seconds,
it does not shrink and does not crack after months or years,
you can pour to any shape that you want but you need to work fast because as soon as you mix it with catalyst cream approx 5%, you have limited time before becoming solid rock,
you can also put additional layers of epoxy or polyester filler to build up,
you can sand it, you can drill it, you can use any type of scale modeling glue, any type of primer or enamel / acrylic paint on it with no problem,
can be purchased at any good crafts store into 250ml, 500ml, 1lt (comes with a tube of catalyst hardener) or bigger canisters and if you can't find it, fear not and try your local decent hardware store and finally...
it is cheaper than dirt - estimated prices are £3 to £10 depending the canister size, the quality, if contains fiberglass grains for maximum strenght etc.

Keep in mind that the chemical reaction after mixing the polyester filler with the catalyst hardener, produces some heat that possibly effect on thin plastic parts, so test it first before try it on your scale model. I dont think that the produced heat is more than Fahrenheit 110, but better watchout. Remember that epoxy materials are dangerous when breath or shallow and could result skin, eyes or lungs problems or even cancer when used for long period with no precaution measures. Always keep in mind, that a powerful vacuum system to suck away the epoxy dust should be used all time to keep the workbench area clean while sanding or milling epoxy or resin materials. Using an issued breathing mask and a pair of surgery latex gloves to prevent dust contact with lungs and fingers while sanding or milling epoxy, is also an important matter that you should seriously take care of! My recommendation is to also wear an overall working suit (as I do) to keep your clothes dust free while sanding epoxy. Some people might find it too much, but I wouldn't like to bring epoxy dust & grains from my work bench into living room and my beloved.

When the plaster cast used as a "negative image" of the right side fuselage, was filled with a thick layer of polyester filler and had enough time to polymerize and get solid rock, it was sunk into water and stayed wet for few minutes, in order to get moistened, become soft and let the right side fuselage replica made of polyester be removed easily.

if you still read this, you are a father already or have a girlfriend

To produce a thin-skinned right side fuselage, the polyester part, must be vacuum formed. That means, that I should build from the beginning a new vacuum chamber box. Vacuum forming is a very simple technique that can produce thin-skinned parts of various forms. I mainly used vacuum forming for producing a variety of components for scale modeling. Basically, its all about a box with a connection for your household vacuum cleaner and a series of holes in its top plate and try keeping the box airtight at the seems. The basic idea is to build from scratch or buy one if you find something similar, a wooden box like the one I present. I found the following item (which supposed to be a display box or something, for placing plants, colored sand & stuff inside and make them look nice as a decoration on the wall) at my local IKEA. Looking exactly like what I've been searching for and considering the low price (not more that 5), I preferred to buy it instead of building a new wooden box like this from scratch. As you can see at the following pictures, I removed the glass, applied a generous layer of water based white glue for wood (which becomes transparent when it dries) across the inner joints, to keep them as air tight as practical and be sure that no air could escape from there.

Visiting my local Dexion store (shelving & racking solutions), I got a 135x85cm hardboard sheet (more than 1 square meter area) for 8. This is actually a louvred panel, designed to stand against the wall and accept hooks & spigots for easy storage of everything from belts and hose clips to spools and reels and all kinds of other parts. I cut a piece on the right dimensions and slide it into rail to test the fitting. The 35x25cm top plate has many 4mm wide holes to allow air to be pulled through them. The locations of the holes are not important, and can be also drilled by hand using a hand held drill. Just make sure that they are fairly close together. This top plate should be pretty sturdy to hold the subject being duplicated. I made mine from hardboard high-density fibreboard plate, but I have seen them made out of aluminum too. The top plate finally was slided into inner rails - otherwise it would be screwed down with flat head wood screws. Be sure to countersink the holes to make the heads flush with the top surface. I also epoxied it down, just to also make it a little more air tight. As long as 1 square meter area hardboard plate, is more than enough for me and can be used to build more than 5 or 6 vacuum forming device plates, I gave the rest to other fellow modelers who are also interested to build one.

Nick_Karatzides · Skill Level 3

Using the proper Black & Decker saw tool, a 34mm wide hole was drilled through the side of the box to facilitate a vacuum cleaner fitting. Luckily, last week I found a real bargain at the local Media Markt store and I bought a 1600W brand new Hyundai HVC-6003 vacuum cleaner for 15 only. I decide to use in this vacuum cleaner into my hobby room and for vacuum forming purposes only. I cut a plastic tube - you may have an old piece of an old tool laying around the house or you can purchase one at a vacuum cleaner shop - and fix it with Bison glue for PVC on the box. Then, I screw a wooden stick into the box's center to prevent any possible hardboard plate bending because of vacuum and finally slide the high-density fibreboard plate through the rails to close the box. I sealed everything with white water based glue for wood. The following pictures show the vacuum chamber box building progress and where you will plug in your household vacuum cleaner.

I also got few wooden picture frames found at the local IKEA store for only 1 to 3 each (depending size) and few metal made spring clamps for 0.5 each, to use them for steady & tight styrene sheet holding while being heated. Avoid plastic clamps, because they might melt while in the oven. It's also possible to build clamping plates made by aluminum sheet and the two plates are clamped together using screws and wing nuts. Aluminum clamping plates is better but might cost more. For these, you are only limited by the size of the oven you have.

Heat your electric oven to some predetermined level, whatever works and start heating the plastic sheet. I have never tried this with a gas one, so use caution if you do! Once the plastic gets warm, youll notice it will droop down. When you think the plastic is soft enough, fire up the vacuum cleaner, take the plastic from the oven and thrown the sheet on the vacuum former. The plastic will nicely form around the moulds. This will take some practice and sometimes a mould tips over or the plastic wont form properly over the mould (folding around edges). This is also the part where I should warm you that you can burn your fingers - I highly recommend Nomex Aramid flame resistant MilSpec gloves, which I personally use for the job. I buy large plastic styrene 50x30cm sheets for 0.5 to 1.5 each (depending width), not the more expensive styrene by Evergreen. When an attempt fails, I usually throw the sheet back in the oven and start again. Ive included some pictures above, but remember, this description of how to make a vacuum form is only a guide. You can make yours with many variations to suit your own needs and from various materials. Once you have the machine, you can make all kinds of things. You can make a lot of aircraft wings, airframe, panels etc out of a sheet like that. You can make the master molds from basswood, epoxy, polyester etc and the parts you make depend on how accurate the master molds are. The molds must be as accurate and detailed as necessary to achieve the results you are after.

Nick_Karatzides · Skill Level 3

I thought as good idea to try something different this time and I did not use the metal made spring clamps to hold steady & tight the styrene sheet on the wooden frame and experiment with thumbtacks. I placed the frame into the preheated electric oven and I wait few critical seconds watching the plastic start heating. As soon as I noticed that it started drooping down, I removed the frame while wearing Nomex Aramid flame resistant MilSpec gloves, to prevent finger burns. While the vacuum cleaner was already switched on, I placed the wooden frame with the pined plastic sheet on the vacuum former plate. The plastic nicely formed around the virtual airframe mould... and voila!

Note: If I leave the styrene plastic sheet in the electric oven a few more seconds and the plastic was softened further, I would avoid the shrinkage of the plastic that appears in the lower right corner of the original cast. The fact that the plastic could heat up even more, evidenced by the fact that one or two thumbtacks were pulled. But as long as my point of interest (the whole right side of the fuselage and a bit from the bottom side) formed nicely around the mould, the result fully satisfied me and I didnt try a new vacuum forming.

-- Edited by Nick_Karatzides on Saturday 26th of September 2009 02:04:36 AM

Nick_Karatzides · Skill Level 3

Using an X-acto, I removed the formed fuselage from the styrene sheet and test fitting on the autogyro scale model airframe. Few drops of cyanoacrylate glue applied on the right spots across the fuselage joints to make the contact secure, did some light sanding on the fresh produced thin-skinned right side fuselage to eliminate some tiny marks and as you can see at the following pictures, the nearly transparent result is more than realistic to scale and completely satisfies to me.

Nick_Karatzides · Skill Level 3

Do you remember the wooden picture frames I found at the local IKEA store for only 1 each, securing the styrene plastic sheet to be vacuum formed? I kept these thin plexiglas plates, to use them as required. Continuing the cockpit construction, I had to build the rear cockpit cover, so I placed the autogyro model upside down facing a glass surface, I boxed it by placing the thin plexiglas plates around it, securing in place with modeling clay for kids. Then, I removed the scale model carefully, leaving space between these thin plexiglas plates. Wet white plaster mixture, applied into the gap, between the thin plexiglas plates to fill the area. When the first layer of thinned plaster was dry and hard enough, two or three extra layers of white plaster followed to finally build the basic cast. Keep in mind that adding salt into wet plaster mixture, reduce the plaster's hardening time and adding vinegar into wet plaster mixture, extend the plaster's hardening time.

When the plaster cast was dry and hardened after few hours, I removed the modeling clay for kids and the thin plexiglas plates. The white plaster cast got shaped into proper dimensions but cutting it with saw, filling with tiny quantities of modeling putty added to close minor scratches and pores on white plaster cast surface, dry sanded and finally sprayed overall with gloss shiny coat.

-- Edited by Nick_Karatzides on Wednesday 4th of November 2009 03:33:03 PM

Nick_Karatzides · Skill Level 3

Because I was planning to use smaller wooden frame to secure the styrene plastic sheet (the piece to be vacuum formed is too small, there is no need to spend big plastic card), I had to close the outer holes on the hardboard high-density fibreboard plate. To do so, I cut a plastic bag in shape and covered as required the desired area. I pined a styrene plastic sheet on the wooden frame, insert it into the preheated electric oven as described before and as soon as I noticed that the plastic started drooping down, I removed it on the vacuum former plate, while the vacuum cleaner was already pluged & switched on. The plastic nicely formed around the plaster cast and here is how it looks like.

As long as the piece looked satisfying to me, I removed the formed plastic from the styrene sheet with a new Nr 11 surgical blade on my cutter, test fitting on the scale model and later start adding internal detail.

Nick_Karatzides · Skill Level 3

I placed the rear cockpits cover in place and secure it with just one or two drops of cyanoacrylate super glue. Then, using a small pencil, I defined the exact line that the rear cockpit cover should be cut in order to let the inside structure visible. Using the mini Dremel tool, I cut and removed the left half part, in a way to look kind artistic.

My good friend Dimitris Pravinos, who is a WWII German tanks specialist scale modeler, sent me about five hundred (!!!) cups he found and looked ideal to use them for mixing colors, modeling putty etc. Few drops of nitrocellulose lacquer thinner and just a little amount of Humbrol modeling putty, were more than enough to prepare a nice liquid mixture to apply on the rear cockpit cover surface, to ensure that little tiny scratches would disappear.

Few hours later, soft sanding and a quick airbrushing with white color to make mistakes, scratches etc become easy to spot, the rear cockpit cover was finally ready.

Nick_Karatzides · Skill Level 3

CHAPTER V - "H" shaped tail construction

The Tervamaki Engineering JT-9T autogyro designed by Finnish engineer Mr. Jukka Tervamaki, is equipped with a twin "H" shaped tail. To build this, I started by rolling flexible styrene sheet around a plastic tube and forming as required to look like the real JT-9T autogyro right side elevator main wing - only 18 times smaller. Following, using the sandwich method (placing one plastic sheet over another), cutting carefully and working extensively with sandpaper to form into desired size and aerodynamic shape, I manage to build the right side stabilizer wing. As you understand, the left side elevator wing, the stabilizer and rudder, will be stripped in a way to show the airframe aluminum skeleton.