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Old Jan 24, 2010, 03:47 PM
WMD
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Jackal Twin - compact 1m span twin-engined COIN style parkflyer. Plans & Video.

Here's a design I want to share with the forum. Gentlemen, I present the Jackal Twin. She's designed to be cheap, cheerful, fast and fun. She's built almost entirely of 6mm depron and she's powered by a couple of cheap BL motors and 2x10Amp Escs. She's basically a Twinstar with a bad attitude. Crossed with a Partenavia. And then maybe a Pucara. Her lineage is, frankly, a little murky - but she's lovely. Plans, build info and pics plus video footage to follow.

Spec is:

Span: 1m
Weight: 498g
Motor: CF 2812 (x2)
Battery: Thunder Power 1320 mAh 3S
Prop: APC 6x4 (matched pair, 1x standard 1x pusher)
Current: 17 amps
Watts: 168 watts
Speed control: Wasp 10A (x2)
Flight controls: Elevator, ailerons, rudder (plus flaperon mixing)

With matching 6x4 props counter-rotating she flies dead straight, there's no torque With the motors up high on that shoulder-mounted wing, there's lots of ground clearance for ROG takeoffs and touch and gos. Landing is just a matter of dropping the power then belly-sliding in. No u/c gear to get bent. No prop strikes. Not ever. Even if you drop a wingtip into the grass, the props are still clear. I'm actually thinking that with the rates on low this would be a perfect aileron trainer. But then again, switch to high rates - and she's a fun handful. Open up the throttle and she'll happily go vertical. And that's with a cheap and basic twin powertrain thats not even breaking a sweat.

On the maiden flight she happily took off with no gear, sliding along on her belly - on wet, sticky, uneven grass - in about 30 feet or so.

[Edit] Here's a quick link to the maiden video from page 2 of this thread - http://s896.photobucket.com/albums/a...win_Maiden.flv

At the moment (I've just maidened her) this is still very much a prototype. She flies (I think) very nicely, but I still have things to sort out. Need to add cowls around the motors, add underwing stores, add nice paint job. I might reshape the fuse belly to slide on grass better, make her more stable, stop her rolling and dipping a wingtip. Anyway...

Anyone want plans or info, just ask - I want to share this with you guys, to try and repay a little for all I've learned on here in years of lurking.
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Old Jan 24, 2010, 04:05 PM
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I started by designing in Sketchup, drawing from a Partenavia 3-view, then narrowing the fuse, making the wing chord much deeper, adding larger control surfaces. I wanted 4 channels and flaperon mixing (but to be honest the flaperons turned out not needed) I thought she'd be heavy and might need to slow down, but no, she's a pussy cat. I added what I hope is a more military COIN look to the airframe (but a bit cartoonified), then set about building a prototype in 6mm depron.
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Old Jan 24, 2010, 04:22 PM
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Edit (22/01/12) : I have shuffled these post around so I can post some pics here of finished models. I find it fascinating how people have taken this design and made it their own, each time:

1. Kepa - ("Water Jackal" seaplane variant) - p7 and then on thead at http://www.rcgroups.com/forums/showthread.php?t=1236492
2. Enthlapy - page 8 (inc video)
3. tolic21 - p9 (120% size)
4. mardimardigras - p10 (70% size, KFM wing)
5. Aero Andy - p11 (60% size, EPP airframe) (inc video on p12)
6. grandwazoo - p12
7. brett.c - p13 (80% size, KFM wing)
8. twinkle - p14 (shorter fuse, longer wing)
9. di.gi -p16 (mini size) (inc video)
10. CaseySP - p16 (T-tail design)
11. twinkle - ("Jeckel" twin boom variant) - p18

Good work, RCGroupers. I salute you.

If I missed anything, or you have something more I should add here, just let me know. Steve
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Last edited by WMD; Jan 23, 2012 at 01:52 PM. Reason: reshuffled to show pics sent in by users
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Old Jan 24, 2010, 04:32 PM
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I can't wait for plans !
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Old Jan 24, 2010, 04:34 PM
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It all starts with the wing. I decided on a a flat-bottomed wing section, with 6mm depron for the base, a 6mm CF tube spar for strength, then a 3mm skin on the top. I complicated things by adding 3mm CF strip at the LE too. The whole thing is just one big rectangle, theres no chord change, no dihedrial. The strip ailerons/flaperons added later give it a little shape, but this is all pretty square so far. I'm using UHU POR to glue everything here.

Wing construction pics
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Old Jan 24, 2010, 04:45 PM
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Wing continued. I like to use 3mm CF strip stuck on the edge of 6mm depron. That way I can easily run a blade along the edge of the CF strip to get a clean chamfered sloping edge. If you line everything up and have a long steel rule, you can get clean perfect cuts every time.
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Old Jan 24, 2010, 04:51 PM
WMD
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Here you go wamsys55, this will hopefully get you started... wing section drawing from sketchup with measurements. To be honest the 6mm CF spar is overkill, but it's just what I had handy.
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Old Jan 24, 2010, 05:03 PM
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Almost done. The wing design is me trying to make everything repeatable. This may not make sense to anyone without OCD - but I want to be able to make the exact same thing again if I need to, with the same results. So I'm sorry if it seems long winded, but it does produce a good parkflyer wing that you can exactly replace when you crash. Which I do. A lot. See video later for detailed examples.

The whole 1m wing (sans strip ailerons) at this stage weighs 94g. That's including a monster 6mm tube CF spar.

Give a quick sandpaper to the LE to make a nice clean curve, then stick 3M satin tape along it. Also run a blade down the TE to get a nice square edge. TE should now be 6mm thick to match the coming aileron strip at the back.
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Old Jan 24, 2010, 05:15 PM
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Quote:
Originally Posted by WMD View Post
Here's a design I want to share with the forum. Gentlemen, I present the Jackal Twin. She's designed to be cheap, cheerful, fast and fun. She's built almost entirely of 6mm depron and she's powered by a couple of cheap BL motors and 2x10Amp Escs. She's basically a Twinstar with a bad attitude. Crossed with a Partenavia. And then maybe a Pucara. Her lineage is, frankly, a little murky - but she's lovely. Plans, build info and pics plus video footage to follow.

Spec is:

Span: 1m
Weight RTF: 498g
Motor: CF 2812 (x2)
Battery: Thunder Power 1320 mAh 3S
Prop: APC 6x4 (matched pair, 1 standard, 1 pusher)
Current: 17 amps
Watts: 168 watts
Speed control: Wasp 10A (x2)
Receiver: Spektrum
Flight controls: Elevator, ailerons, rudder (Flaperon mixing)

With matching 6x4 props counter-rotating she flies dead straight, there's no torque With the motors up high on that shoulder-mounted wing, there's lots of ground clearance for ROG takeoffs and touch and goes. Landing is just a matter of dropping the power then belly-sliding in. No u/c gear to get bent. No prop strikes. Not ever. Even if you drop a wingtip into the grass, the props are still clear. I'm actually thinking that with the rates on low this would be a perfect aileron trainer. But then again, switch to high rates - and she's a fun handful. Open up the throttle and she'll happily go vertical. And that's with a cheap and basic twin powertrain thats not even breaking a sweat.

On the maiden flight she happily took off with no gear, sliding along on her belly - on wet, sticky, uneven grass - in about 30 feet or so.

At the moment (I've just maidened her) this is still very much a prototype. She flies (I think) very nicely, but I still have things to sort out. Need to add cowls around the motors, add underwing stores, add nice paint job. I might reshape the fuse belly to slide on grass better, make her more stable stop her rolling and diping a wingtip. Anyway...

Anyone want plans or info, just ask - I want to share this with you guys, to try and repay a little for all I've learned on here in years of lurking.

nice looking plane would like to see some plans.
i have four off those out runners.
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Old Jan 24, 2010, 05:26 PM
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Ok, so now we have a nice big straight wing, we need nacelles. Mark out where your nacelles will go, then cut access holes for wiring. We need to get esc and servo cables to each nacelle. I used liteply to form bulkheads to mount the motors. Was trying to leave the two air vents clear so that when I mounted cowls over the motors there would be some airflow.
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Old Jan 24, 2010, 06:08 PM
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Nacelles drawing with measurements. The shape of the nacelle changed and ended up more simplified, but this is the placement.
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Old Jan 24, 2010, 06:15 PM
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er, sorry popedan but these *are* the plans. This is as good as it gets. I just print out a schematic from sketchup, then use a ruler and a pencil and start cutting. But hey, if you want the sketchup file, you're welcome to that, if it helps...
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Old Jan 24, 2010, 06:21 PM
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Ok, more nacelle work now. Need to extend wires for the 2 escs (both power and control) and do a T- junction to both. Need to disable one red wire from one esc. Also now is a good time to check what direction the props spin in. Switch cables if needed to get contra-rotating props. Nacelle fronts are 6mm, but the top and bottom covers are both 3mm depron , with some sanding / chamfering. Its not critical, is just cosmetic to get things to fit nicely as possible. Also we need to check alignment of motors. On the prototype I set 0 degress donwnthrust, I put in the the bulkheads at 90 deg to the flat bottom of the wing section. That worked, but I think a tiny bit of down would be even better.

Edit: re props and direction of rotation, I think the best way is this: from pilots point of view, looking forwards, the right-hand motor and prop should be going anti-clockwise, and the left-hand motor and prop should be going clockwise. This is so that any loose dirt, grass, leaves, litter, tin cans or wildlife you may encounter as you belly-slide along the ground is swept away from the fuselage. Probably.
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Last edited by WMD; Jan 25, 2010 at 06:48 PM.
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Old Jan 24, 2010, 06:40 PM
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Nice looking plane, I'm going to have to build this one. I will be also be waiting for the plans when you post them.
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Old Jan 24, 2010, 06:45 PM
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More nacelle stuff. I was planning just to use double sided tape to mount the aileron servos, but changed this later. After one fell off.
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