1/18 scale Tervamaki Engineering JT-9T autogyro

[Nick_Karatzides]

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, it's 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, coloured 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.

[UrbanKnight]

I hate you!   

[Nick_Karatzides]

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.

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, you'll 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 won't 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. I've 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]

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 mold... 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 didn't try a new vacuum forming.

[Nick_Karatzides]

Using my X-acto blade, I removed the formed fuselage from the styrene sheet and test fitting on the autogyro scale model airframe. Few drops of CA super 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.

[Kerber]

Excellent work !

If I can see well, the new "side" is extremely thin, man can see the light trough that...very nice trick for modelers. Cheers !

[Nick_Karatzides]

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 plexiglass 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 plexiglass plates around it, securing in place with modeling clay for kids. Then, I removed the scale model carefully, leaving space between these thin plexiglass plates. Wet white plaster mixture, applied into the gap, between the thin plexiglass 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 plexiglass 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.

[Nick_Karatzides]

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 plugged & 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]

I placed the rear cockpit's cover in place and secure it with just one or two drops of CA 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.

[Nick_Karatzides]

My good friend Demitris "Jagdpanther" 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 colours, 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.

[Nick_Karatzides]

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]

CHAPTER V - "H" shaped tail construction

The Jukka Tervamäki Engineering JT-9T autogyro designed by Finnish engineer Mr. Jukka Tervamäki, 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.

[menestenasli]

this looks excellent!!!!

[Boki]

WOW  ! Amazing work. I Love it! 

[Aranza]