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Jun 13, 2012, 10:46 AM
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P. Tritle's Avatar
Build Log

J-3 Kitten -- Going Small


Since the popularity of small outdoor models that are also suitable for indoor flying I figure it's about time to try my hand at it as well. As always, learning something relatively new always works out best when starting out with something simple I decided to go with the J-3 Kitten high wing home-built. The model spans 28" and is set up for 3 ch. R/C using the equipment stripped out of a Beast. So with that, let's get started....

Building the Kitten begins with the wing. Since suitability for indoor flight is the goal, the model has to be light, so a Single Spar Split Rib system was used. The ribs are layed out with a stick bottom that incorperates the lift and jury struts, then the spar aliggned and the upper rib sections were added.
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Jun 13, 2012, 10:48 AM
was geht , müssen unten kommen
Keenan smith's Avatar
First!.....

Awsome!
Last edited by Keenan smith; Jun 13, 2012 at 10:50 AM. Reason: Joking...!
Jun 13, 2012, 10:48 AM
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WAGliderGuy's Avatar
Glad to see your back! This J-3 sounds perfect for my indoor site

Ethan
Jun 13, 2012, 10:48 AM
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Finishing the Wing


With the Basic Wing Assembly together the tip platess were added, then the panels blocked up and the Center Section completed.
Jun 13, 2012, 10:50 AM
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Building the Tail Section


Nothing Fancy Here. The basic assemblies were built over the plans and then sanded to shape in preperation for cover.
Jun 13, 2012, 10:51 AM
was geht , müssen unten kommen
Keenan smith's Avatar
nice work When will this be available...?
Jun 13, 2012, 10:53 AM
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Building the Fuselage


Construction begins with the side frames. Both were built, then the joinery begins at the cabin. The remaining formers and stringers were then added to complete the basic assembly.
Jun 13, 2012, 10:56 AM
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Wow, that was quick!


Thanks guys, it's great to be back. Been sneaking in the build among many other customer projects, and if all goes well will be done real soon. Meanwhile, as soon as the model is flown and trimmed I'll offer up the Short Kits.

But for now, keep an eye on the thread. Will finish up what I have below, then button it up and get the kit in place as soon as the model flies.....
Jun 13, 2012, 11:00 AM
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Building Up the Landing Gear


With all the framing done it was time to build up the Landing Gear assembly. The gear is quite complex, like the J-3 Cub, so all of the parts were bent to shape, jigged up and soldered together.....
Jun 13, 2012, 11:04 AM
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Dry Fitting the Big Pieces


With all the framing done the model was dry-assembled to test the fit of the major assemblies. A couple of minor fit problems were identified and corrected. One big thing showed up in that the wing was just too flimsy at the root, so the balsa diagonal bracing was added to stiffen things up nicely.
Jun 13, 2012, 11:07 AM
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Mounting the Radio and Motor


The motor was mounted on a balsa plate, then aligned and glued into the fuselage. A balsa frame was made up and glued in place, the the Rx/Servo Board was secured with silicone. The pushrods were made up from .025 carbon rod with .-15 wire z-bends added at both ends. The tail section was then taped in place and the pushrod guides added about mid span to prevent buckling under load.
Jun 13, 2012, 11:10 AM
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Prepping for Cover


With all the framing done and the equipment in place and working the frames were detail sanded and the struts built up. The lift struts are balsa with the cabanes made up from round toothpicks. The front cabin bracing was also made up from toothpicks but weren't glued in until after the fuselage was covered.
Jun 13, 2012, 11:22 AM
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Cover and Trim


The model was covered with blue and yellow Microlite. I figured that since these tired old eyeballs don't work as good as they once did a colorful scheme would go a long way in keeping track of this little jewel, so the blue and yellow military trainer scheme sounded like a good idea. As always, Callie did a terrific job with the trim.

Meanwhile, my target weight was 2 - 2.1 oz. and less wheels, prop and battery tray the Kitten tips the scales at 1.9 oz. so it looks like the goal is easily reach-able.

At this point we're down to wheels, prop and the battery mount. If all goes well I'll finish it up today, and if the wind gods will mind their manners will get a test flight either tomorrow or Friday morning. Will post up the results as soon as it happens.

The plans and cut files are pretty well wrapped up too, so barring and major complications the kits should be available in a couple of weeks tops, so stay tuned for all the details......

PAT
Jun 13, 2012, 12:23 PM
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Pat,

When you say you stripped the hardware out of your Beast, I assume you mean the Park 180 motor and the AR6400LBL brick. Is that correct?

If so, it looks like the RTF weight with battery will be about 3+ ounces. With the power available, it could be a rocket, instead of a kitten!

Jim R...
...never a rocket scientist, but he knew a couple.
Jun 13, 2012, 01:33 PM
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She's Ready to Maiden


Just got the wheels and the prop mounted, and to get a good CG the battery ended up on the Instrument Panel, so no addition mounting pieces were needed. In the end, the kitten tips the scales at exactly 2 oz. so the chance of the model being under-powered is at best non-existent! I can see where some diligent throttle management will be in order with this one.

Forthe wheels I used the ones from the Carbon Cub. They're a tiny bit small in diameter, but the balloon tires look way better then the narrow 1 1/4" foamies. I also went with the 5-2.75 prop to help keep the pitch speed at least a little bit under control.

So now, we keep our fingures crossed for good air in the morning so we can give her a try.....

PAT


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