1/18 scale Tervamaki Engineering JT-9T autogyro

[Nick_Karatzides]

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.

 

[jspitza]

This build is EPIC! awesome stuff. The vac form box is genius.

Nick makes this stuff look SO easy to do right?

 

[jspitza]

Nick, I award you with Scale Models UK Honorary Doctorate. And the Nobel peace prize for the vac form box.

 

[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.

 

[tigertc]

Fantastic stuff!

 

[Nick_Karatzides]

 

[Bluewavestudios]

Hi Nick,

Very impressive work there so far and I do like your technique for the Vac Form box and your methods of using it too. I have covered Vac Formers on a separate post on here already and yours is almost identical to mine. You have nicely demonstated how it can be used and the results are superb !!

Interestingly enough, I actually saw my first real autogyro in flight over here last week on Thursday. It was a nice clear sunny day and I was down at the beach walking my dog when this one flew over and did a few low circuits over the Great Orme. I was quite impressed with it's agility and manoueverability. Even hearing the rotor noise at one point sounding just like a Helicopter !!

The only one that I had seen before that was the original Cierva machine in the RAF Museum at Hendon

Keep the good work coming !!

Yamas !! ..........Mark

 

[Nick_Karatzides]

CHAPTER VI - Landing gear system construction

The single seat JT-9 and the tandem seating JT-9T, are available with tricycle landing gear system with a steerable nose wheel or a taildragger version too. For both types, the type of landing gear is based on the placement of the exact CG position, determined after complete weight calculations according the owner/pilot's personal needs. My 1/18 scale model is designed to be equiped with a tricycle landing gear system with a steerable nose wheel. An utility free-spinning tail wheel is also placed, to prevent any accidental damage on tail structure if the autogyro raise nose too high while in ground. Feel free to check the diagrams and images found into my first post of this project, back in page 1.

Using plastic card, sprue, metal wire, resin tires and brakes fit accurately to 1/18 scale diagrams and few unidentified parts found in the sparebox, I build a realistic looking 1/18 scale main landing gear system with absorbers and a steerable nose gear. I stole a nickel plated button from GF's favorite dress (hope she'll never find out where's the missing button or I'm in real trouble), placed it into a plastic tube piece, covered with with transparent plastic card & add some details to simulate the landing light in scale.

Yeah, yeah, yeah... I know! I am a button stealer, but let's admit it! We all prefer less buttons on female dresses.

 

[Nick_Karatzides]

CHAPTER VII - Canopy construction

The Jukka Tervamäki Engineering JT-9T autogyro canopy is made by bented and cold-formed 3mm polycarbonate sheet. The backwards sliding canopy of the single seat JT-9 version, offers the possibility to taxi and fly slowly with the canopy open, a benefit in a hot climate. The trainer / tandem seating JT-9T, has a side opening one piece canopy. Of course, canopy modifications can be done, according the autogyro owner's personal needs or desires.

 

[Nick_Karatzides]

I used styrene plastic card to form it as shown into following pictures to give the basic shape of the canopy. Then, a layer of polyester filler applied on the styrene. 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 strength 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 don’t think that the produced heat is more than Fahrenheit 110, but better watch out. 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 basic canopy shape made by styrene sheet, was fully covered by a a thin layer of polyester filler and had enough time to polymerize and get solid rock, I sand it with wet sandpaper to make the cast curved and shiny. To produce a thin-skinned canopy, the polyester part should be vacuum formed. As described into previous chapters, a transparent plastic sheet were pined on a wooden frame, preheated into electric oven and as soon as I noticed that it started drooping down, I vacuum formed it. The clear plastic nicely formed around the canopy cast following the curves & details as planed. Using an X-acto, I removed the formed canopy bubble from the transparent sheet and start adding details, such as canopy's frame. Few drops of cyanoacrylate glue applied on the right spots with great caution. Remember that CA glue does fog the transparent parts and this canopy would not be an exception - that's why I placed some very tiny drops of it, just on few spots.

 

[Sky Raider]

Fantastic workmanship mate, cant wait to see the finished product. Well done.

Andy

 

[Nick_Karatzides]

It’s sad! Obviously, voodoo curses came from the unspeakable dirty Viper snake, got real and the final varnish finishes on the model suffered what the Americans call as FUBAR - F@cked Up Beyond All Recognition.

In brief words, the color layers popped and “cracked” everywhere on the model’s surface, just before the final touch. For some mysterious reason, the color looked peeled off and an unexpected chipping (I would never succeed this by purpose) appeared! The scale modeling accidents committee is expected to investigate the possible reasons within following days, but unconfirmed sources report "pilot’s error" - OK, I made a rookie’s mistake, while using old colors or coat varnish. Meanwhile, the following actions took place:

• Garlic cloves were hanged across the workbench to keep away evil curses, vampires and “snakes” (or those who claim themselves as “snakes”),
  
• The scale model were covered with a thick layer of ModelStrip product, locked tightly in a plastic bag and left overnight to let the chemical work.
  

 

[Nick_Karatzides]

It’s sad! Obviously, voodoo curses came from the unspeakable dirty Viper snake, get real and the final varnish finishes on the model suffered what the Americans call as FUBAR - F@cked Up Beyond All Recognition.

CHAPTER VIII - Live After Death

When I started building the model, I did not expect to present the CHAPTER VIII under this title. Bus as all the sad & bad situations in life, it was unexpected and accompanied by great frustration because suddenly I saw months effort to dissolve in only few minutes. The old colours (or bad white spirit solvent) that I used, have led to drying crack. Unfortunately, I ignored all the warning signs such as thick grains left by the white colour in which I primed the scale model before the final painting. Having as target to make this model alive again, just like Iron Maiden Eddie’s Live After Death, I decided to try a full reset – after all, I had nothing to lose! The scale model was already FUBAR.

The following photos show the unsuccessful paint process. The problems appeared marked inside the red circles. Unfortunately, I have no photos of the model while looked completely written-off, because at that time I was not in a mood to take pictures!

​

ModelStrip, was the first thing came up as the most conventional solution to try paint removing. Following the instructions on the box, a generous stuff applied on the model, wrap it with airtight plastic bag to prevent drying and wait about 15 hours to let the chemical work. Opening the bag next day and checking the results, the colour (or rather the colour layers) were soft and could be removed by rubbing vigorously with an old toothbrush. Unfortunately, using the brush on some very delicate spots (even with careful use), had as result to break / or ruin a couple of plastic pieces. Moreover, the paint could not be removed through narrow points and difficult locations.

At this point and while I’ve already used all the ModelStrip material without being satisfied with the outcome, I decide to change tactics to something more unconventional, such as oven cleaner.

Following the product’s directions as always, I sprayed the model with the material, wrap it with airtight plastic bag to prevent drying and wait about 15 hours to let the chemical work. Testing results next day, the oven cleaner failed no more than ModelStrip. I noticed that the colour could be removed but only when pressure and persistent rubbing with brush and that was prohibitive for some parts of the model. Not having another solution, I approached the most unconventional method and visit a science specialist - my local grocery store!

• - Hey man! I need something really strong to clean up kitchen’s oven?- Really strong? Use this!
  

…and he gives me a dust covered 1lt plastic bottle found in an almost unreachable shelf. Reading the bottle’s label, I found out that it contains sodium hydroxide also known as lye (corrosive alkaline substance) or caustic soda and is a caustic metallic base. It is used in many industries, mostly as a strong chemical base with chemical type NaOH.

• - Are you sure that this will work? Are you sure that this is safe to use?- Trust me. It’s gonna clean up the kitchen’s oven like a nuclear bomb!
  
  - How much?
  
  - 3.50 € . Take it or leave it.
  

Thinking about a possible failure, I filled a plastic bowl with the milky liquid contained in the bottle and threw all the model pieces inside. As long as the autogyro model was already FUBAR, I had nothing to loose to try. I sealed the bowl with a cover and leave the sodium hydroxide to act for 20-30 minutes while the instructions sets out to wipe the sodium hydroxide chemical liquid after 10 minutes. Opening the plastic bowl’s cover, a nice surprise followed...

​

 

[yak face]

hi nick, so glad you managed to save the project, it would have been tragic if it had been trashed after all your superb work. Looking forward to the end result ,better luck with the paint this time , cheers tony

 

[Sky Raider]

Hi Nick, I know exactly how you fell mate. I thoight my current project was destined for the bin when the fuselage warped like a bannana over night. Trial and error payed off and i managed to save the day. Good luck in finnishing this fine work.

Andy

 

[Nick_Karatzides]

The truth is I was delighted! Styrene pieces simply and magically totally striped off the enamel colour layers! Absolutely success, without even apply brush cleaning! Amazing product - incredible grocer! Just because I couldn’t believe it and I wanted to make sure that the colour striped off because of the sodium hydroxide chemical (and not the previous used ModelStrip product or the kitchen oven cleaner), I decide to experiment. I threw in a bowl, already filled with the chemical, a 1/18 scale female figure that I was about to convert for a future project. The specific 1/18 scale female figure, is made by Fast Women brand and can be found by clicking HERE). The results after just 15 minutes in the sodium hydroxide chemical - Perfect! The following pictures, show the "before" and the "after".

Keep in mind that the sodium hydroxide is (and thus should be considered) a strong caustic base. This means that:

• Throughout the impregnation of the model parts into sodium hydroxide, you should take all the necessary protective measures (like mentioned in the warnings on the bottle’s label) and is certainly to use disposable surgical gloves made by latex and breathing mask with appropriate filters to protect against possible fumes.
  
• The colour stripped plastic parts must be rinsed with soft acid to neutralize the caustic base and produce salt and water. Dunking the colour striped parts in plastic container filled with cooking vinegar and then rinsing with plenty of lukewarm water, plastic is now safe to handle with bare hands.
  

Under the above "adventure" circumstances and considering that all these years dealing with the scale modeling I've tried many color striping methods (including ModelStrip, kitchen oven cleaners, blue alcohol, brake fluid, nitro laquer disolvent, etc), I think that sodium hydroxide NaOH is the best method so far, for the following reasons:

• Kitchen oven cleaners in spray canisters, can do the job, but they cost 3 - 4 € for a 300ml product in which also includes the propellant gas. On the other hand, the NaOH in liquid form is a pure substance, much less price, taking for 1lt bottle, which equals 3.3+ times more product! Using the liquid form NaOH (which you can fill a plastic bowl), you can sink several plastic pieces, same time!
  
• The brake fluid may be effective and remove paint, but it is not plastic friendly plastic and is likely to convert the scale model into a blob of molten plastic. It is clearly more expensive and as far it is highly toxic, flammable and hardly to manege, I will not recommended it for scale modeling use.
  
• Nitric acid laquer disolvent, could be a nice solution for metal figures paint striping, but it is not the best for the plastic. Just like the brake fluid, it does melt and damage plastic parts.