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Author Topic: My Forward-swept wing PREDATOR  (Read 800 times)
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Pit
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« on: June 06, 2014, 07:29:39 AM »

In response to a few PM's I've received (one just yesterday) requesting photos of my forward-swept canard (rc) model that I mentioned in an earlier message in the General Forum.  It is called the Predator, designed by Andy McNally and was published in (IIRC) RCM & E magazine sometime in the early 90's as a slope glider.  It is VERY stable, even with the fixed canard (builder's choice of fixed or moveable), using what appeared to be the CJ-3309 ( slightly reflexed) airfoil and is set up as a flying wing (two channels, mixed).

The span is 44 inches and the OAL is about 30 inches and mine weighs 800 grams RTF.  The canard is fixed (optional) at about +2° from datum.  Not fast, even when ballasted but a lot of fun.  Stays up when even some gasbags fall out of the sky with very light slope lift.  Stall is practically non-existent and the model can be hauled around in an 80° bank at a ridiculously low airspeed - 2 feet off the ground (documented by my club a few times).

I've had only two opportunities to fly off a slope - the first was a nice trip but with NO wind (forecast was for wind >10 kts on the Wasserkuppe), and the second was also a near bust with winds light and variable, but I did manage one short 5 minute flight (2 knots wind that petered out).  Flights off a high-start are only moderately successful as the model requires a good thermal to do much other than show how stable it is and how maneuverable it is at low speeds/altitude (to avoid the chain-link fence at our old field).

The photos are of the model on the wall behind a big pile of other models.  It's about time to dig it back out for modernization (2.4GHz) Wink.
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My Forward-swept wing PREDATOR
My Forward-swept wing PREDATOR
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TekGnosis
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« Reply #1 on: June 06, 2014, 02:33:25 PM »

Thanks very much for this.  As noted in the PM, it's encouraging to see a report of a forward swept, possibly light anhedral wing with a thick chord that has good stall characteristics.  There are lots of easier ways to fly and be inherently stable, but the kids really like forward/down swept wings since every evil alien ship in every movie... ever...  has had this design. Wink

I also found a version of this plane that had been modified significantly.  
This version looks quite similar except being larger and with heavier construction techniques.  Reported AUW was 5.5lb with a glow motor, full servos, and retracts on 54" span.

http://www.grahamlegg.talktalk.net/wig.html
^^ Some interesting talk about the airframe in that form and possible ground effect impact and inability to take off, though I have to wonder if weight had something to do with it.  At the top is a .dxf download link for anyone interested, I can't attach here only pics allowed.
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Re: My Forward-swept wing PREDATOR
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Pit
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« Reply #2 on: June 06, 2014, 05:10:18 PM »

The forward sweep of the wing combined with the close-coupled, rear swept canard (~2° positive incidence and no 'hedral, creates an optical illusion of having anhedral Grin.  It actually has about 5° total dihedral.  A number of people who have built this model, including those who bought 9 of the ones I built (ARC) slapped a speed 600 or a Pletti/Lehner on the back and flew them with some success (heavy - they gained over a kilo with 8 sub "C" cells and those brushed paperweights.  A lot of experiments were done with I.C. motors on the original sized airframe up to 0.40 cid (6,5 cc) in both pusher and tractor config.  Flew quite well... once it got into the air.  I don't think ANYONE was successful getting it to ROG - unless it hit a bump and literally bounced into the air.  This was true even with those models that had functional canards and coupled canard/elevon.  Looks mean and FAST(NOT!), but it's a real puddytat to fly.

Might have had something to do with the airfoil, as there are better ones out there.  Profili even has a few in the standard library that should be MUCH better.

I might have an opportunity to go to the Wasserkuppe tomorrow for a couple of days, so I might take the PREDATOR along if there is enough room in the van Wink.
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« Reply #3 on: June 06, 2014, 08:40:55 PM »

Fantastic info, and good to know about the dihedral.

I'll be applying the form factor to a much smaller 6mm foam structure with carbon support and likely 2:1 power/weight, anticipate no issues getting airborne.

From the look of it I don't know if those canards are really contributing much, there are even notes on some posts about the original that it flew fine with or without them.

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« Reply #4 on: June 06, 2014, 09:29:28 PM »

Nice one Pete, it may just be the thing for our slope site where the wind usually doesn't blow all that hard, and we get a lot of help from thermals.  I'll look up the plans and maybe build one as my build queue allows.

--Ates

EDIT: Nope, couldn't locate the plan at any of RCME, Aeromodeller, RCM, MA or Carstens Sad. Any other guesses?
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« Reply #5 on: June 07, 2014, 12:58:33 PM »

I'm looking for my original plan.  I have not been successful finding the plan anywhere either, but I do remember that it came out of an RCM & E mag.  I also dug up some of my notes from the builds that are dated from 1996-7 and I had gotten the mag as a hand-me-down (still fairly new).  I checked thru the "X" plans (and all the others) at RCM & E but it is not listed.  the DXF drawing on Graham's site is an enlargement (to 55") and modified for a nose mounted IC engine.

Maybe an email to Graham will help?
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