|Sep 02, 2011, 10:06 PM|
SNice-mitar -Scimitar Wing Clone...just couldn't help myself...sorry!- video & PLANS!
Always wanted to get into wing-type models, but never liked the looks of the stryker... Built a few funjet clones (Prime-Jet 8)- great flyers! Once I saw the Scimitar, I knew I had to have one, but it is well out of my budget...so... here goes!!! May add the thrust vectoring at a later point depending on how she flies...
Got the model done... prototype-done...maiden video -done (posted below)
She flies!!! So, as promised, plans are below. I have also scaled them up to a 34" version for those that would like to use a traditional parkjet power system with a 6" prop. Plans are pretty freeform so you can put stuff wherever you like. I suggest building the airframe first and then cut areas for servos, motors, cooling vents, hatches, etc... be sure to post pics! Enjoy!
Stats for the 28" prototype:
AUW: 11.4oz - 1000mah 3S lipo; 12.7oz - 1300mah 3S lipo
Airframe minus batt: 8.4oz
Bare airframe (unpainted, no electronics): 3.1oz
Lipo: 1000 - 1300 3S lipo (25-30C) -- (I prefer the 1000mah 3S 30C)
ESC: 30A (all I had available - min 20A; 25A to be safe)
Servos: 2x9g (elevons); 2x5g (rudders)
Prop: 5043; will also try 5x5 speed
Prop UPDATE: 6x4 - it's close, but it will fit between the rudders - this is my favorite prop - the acceleration is quick - she will shoot wherever the nose is pointed - much easier to get out of "sticky" situations...
CONTROL THROWS (28" Version):
These are my settings -- adjust to your liking!!! Note - I do not use dual rates on this model - only expo. Elevator throws are very aggressive at endpoints. Too much elevator sits her on her tail and reduces airspeed to near zero (see video). Be sure you have the thrust (or altitude) to get out of this! If not, I would strongly suggest reducing elevator throws.
ELEVATOR: 3/4" up; 3/4" down -- 50% expo
AILERON: 7/8" up; 1" down -- 35% expo
RUDDER: 1-1/4" left/right -- 25% expo
Explanation of 3-Stage wing profile:Below you will find a diagram detailing how I sanded the leading edge. The wing has a 3-stage leading edge profile. Not sure how much of a difference this makes - but it works for me! The theory behind the 3-stage sanding was to create reflex and improve stall characteristics for maneuverability. It seems to work wonderfully, but is untested b/c I never flew it without the 3-stage leading edge...
Compilation Video w/ 6x4 prop!:
Maiden video - 1000 & 1300 lipos:
Since the maiden video, I have greatly reduced the elevator throws, and added additional support to the wing. I also now mount my batteries flat. In the maiden, I had the battery mounted sideways which was making the roll very sloppy. Roll is much more axial with the battery in the flat position. With the above adjustments, I can now knife-edge with rudder and a little bit of aileron input. Once I get some more stick time, I will post a short highlights video.
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|Sep 04, 2011, 01:49 PM|
For the initial prototype, it will not have TV. I just want to see how the airframe does. However, I have thought about the TV... It could be accomplished by movin the motor mount forward and getting the rudders in the propwash OR with a mechanical system. If I go the mechanical route, I would definitely want 360deg TV instead if just yaw.
The build is going great. The prototype has a ws of 28in. I was worried about the size - after I cut everything out, I was thinking I should have gone smaller for the intended power system (emax2805 2800kv, 5x4.3 prop, 1000mah 3s lipo). But after I weighed everything - I was under 10oz! The power system will be fine - right now I have it on a heavier, smaller plane.
...maiden should not be too far off!
|Sep 07, 2011, 02:56 PM|
Airframe wt. (so far): 2.8oz
So far so good... all the parts have fit together really well. I even figured out a way to preserve the rudder for belly landing (+1 Snice-mitar; 0 Eflite Scimitar).
I planned on installing a 9g rudder servo in the fuse and linking it with flexi-rods. However, to get the desired cg, the batt, ESC, RX will be pretty far back in the fuse (where I intended on putting the rudder servo) I now think that I will just install 1 5g servo for each rudder. That may give me a cool airbrake mixing option!
Still pondering the TV. I've looked at a bunch of homemade setups using heli swashplates, etc. I've looked at videos of funjets and the real scimitar spinning and flipping in the air. I really have no interest in spinning or flipping in the air at lightning speed. However, a stationary hover would be cool (to me) - but I think it would be very tough given the position of the CG. I think she will knife edge and high alpha great on her own w/o TV. ...so the TV will be on the backburner for now... maybe a V2 upgrade...
|Sep 08, 2011, 01:28 PM|
Thanks guys! Hopefully I will be able to install some of the electronics tonight. This build is going much slower than I expected -- work has been pretty hectic lately!
|Sep 09, 2011, 05:17 AM|
Nice one....You beat me to it...Well done, its looking good..
I saw the videos of the actual model for the first time the other day and had to add a KFm4 build to my list..
Now I will wait for your plans..
Please dont forget to add your build link in the KF builds thread here http://www.rcgroups.com/forums/showt...122108&page=13
|Sep 12, 2011, 09:35 AM|
...Almost there.... got her painted -- look familiar? All servos are installed, and control surfaces linked up. Did a glide test of the bare airframe to determine cg. Got a great glide.
Left to do:
- Cut hatch, install ESC, RX, Batt.
- Touch up any rough spots on paint job
- Add clear packing tape to wing leading edges and bottom of fuse
I tried something new with the leading edge of the wings on this model. The inner part (strakes) - I sanded the leading edge closer to the top of the wing. From the break to the fence, I sanded the leading edge to the center of the wing; and from the fence to the tip, I sanded the leading edge towards the bottom of the wing. I am hoping this will improve slow speed handling and ward off stalls.
I think my aileron servo placement for this prototype will be fine, but for larger, faster versions, I think I would install the aileron servos further out on the wing and perpendicular to the hinge line.
davereap - I will definitely post link and video to your KF thread!
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