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JK Aerotech Big-T

Old 02-04-2012, 09:06 AM
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Join Date: Dec 2011
Location: Milwaukee, WI
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Default JK Aerotech Big-T

I originally saw the Jk AerotechBig “T “ airplane advertised in Model airplane magazines probally 12 years ago, and thought it was kind of neat in part due to its large size and being made of hot wire cut foam with coroplast cladding. While this plane was originally designed for a .25 to .40 glow motor, I knew it would make a good glow to electric conversion.

I had already built a 1/12 scale Zero from the same company, so I was familiar with howJK’s stuff went together, andso when I sawsomeone advertising a prebuilt one on RC Groups at a fair price, I went ahead and bought it.

Among Big T’s unusual features was its folding wing. This is accomplished by using coroplast as a hinge, connecting the two wing halves on the bottom, and using two interlocking coroplast pieces on each half on the top. You just unfold the wing, interlock the top pieces and use tape to hold them together. This has proven reliable in practice.

Big T arrived already built,colored orange and without ailerons. It flew ok but not precisely, using a fair bit of dihedral and rudder forcontrol. I decided to recover it changing it to yellow and add ailerons. I flew it at first with a kyosho endoplasma car motor using a great planes gd600 gearbox with a 3.8:1 ratio with an 8 cell gp3300 nihm pack from Robotic Power Solutionsand a apc-e 12×8 prop. This had plenty of power for this 5lb plane and 12 minute flights, but I eventually was able to source a 10t pinion. This changed the ratio to 4.6:1, and I used that with an extracell soldered in converting from 8 to 9 cell packs. This gave about the same rpm but at a lower amps, allowing the plane to fly much longer than the one extra cell would indicate. I belive this was because the cells weren’t working as hard I could empty them further before the low voltage cutoff hit. With this new setup, I got flights as long as 18 minutes.

The restof the plane was pretty straightforward. The motor cowl was actually the top of a two litre bottle cut out and painted black on the inside. I used wheel pants from a crashed magic extra and colored them black.

I flew the heck out of this great plane for a couple of years, but is been sitting now for a while. I may repower it with lithiums. When I built it back when, lithiums for a plane this size were just way too much money. Now I can put infour HobbyKing3s2200 packs in parallel, making a 8800 sizedpack for under $40. Sounds like Big “T” might be flying this summer again.


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