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Old Dec 03, 2008, 08:51 PM
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Build Log
Mini Supra (1m / 40") - Depron hotliner (with HD maiden video)

Hi Guys,

I'm sure most of you have heard of the Supra. For those of you living under a rock, here's the low-down:

http://www.charlesriverrc.org/articles/supra/supra.htm
http://www.kennedycomposites.com/supra.htm

To my mind, it is the single most sexy-looking and well-performing aircraft that I have ever had the pleasure of flying - until I got all sorts of R/C issues which are soon to be sorted out (servos poorly manufactured). I've been so upset with having the Supra "grounded", that I decided to build one in the meantime out of scraps that I had buried in a big box labeled "R/C stuff".

Now, if I were a blucore-pro or vacuum-bag-ninja, the end result would have probably been a nice floater plane that even I could thermal all day (just like its bigger sister). Since I'm not, I decided to take the risk-free alternative: "Anything propelled fast enough flies". I suck so much at building (really impatient) you'll be laughing all the way through the thread. Don't believe me? Check the 30-second-paint-job

I will provide plans for the wings, but I don't have the fin and tail plans that I used anymore (didn't save them ... ouch). You can download these from the first link (charlesriverrc). What I did was import the plans into Photoshop and then I looked at the Depron Dynamite and roughly resized the plans to fit its dimensions (just visually, mind you. I don't measure or calculate - it's against my religion). Mark Drela would probably smack his forehead if he saw the end result, but believe it or not, she flies. And she flies really well. If you're less restricted by your religion, you may of course draft your own wing and share the plans with us. And airfoils, for that matter, since I just sanded a "shape of a wing" into them.

Below are a few pics. She moves around at around 80 km/h (again, guesstimate, since I don't measure ... I take my religion very seriously ) and floats just nicely. Nothing to thermal, mind you, but it's a hotliner that looks like a thermal duration glider. I've always wanted something fast and "edgy" (read "hard to control but still nice to fly").

And here's the video of the "re-maiden" (did some minor modifications and added paint)
Mini Supra (1m / 40") - Depron Hotliner - Re-Maiden (1 min 0 sec)
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Old Dec 03, 2008, 08:52 PM
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Here are some numbers:
Motor: ~250W @ 1200 kV
ESC: 30A
Battery: 1200mAh 3S
Prop: CAM folding prop, 10x6
Servos: 8g servos
Controls: Motor, Aileron, Rudder, Elevator, Flaps (to be added, trying to find a capable servo among the scraps)
Total weight: ~350 - 375g

All supplies courtesy of r2hobbies.com - they didn't give them to me for free, but considering the prices they charge they just as well could have (the motor was $11 as far as I can remember) Quality is top notch in my books.

The motor doesn't nearly pull 250W. The prop is far too small. I'm sure 10x10 or 10x12 could be possible. But a 4500kV motor is already on the way. 280W. Again courtesy of r2hobbies.com. Just to spice (and speed) things up a little
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Old Dec 03, 2008, 08:54 PM
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Construction Details/Instructions

For those of you that want to build one yourself, I wrote down how I built it. I recommend reading through the instructions first, then build, as they jump back and forth in the timeline. All can be done in roughly 5 hours and with about $50 worth of material and R/C gear.

I used 3mm depron for this. Everything is glued with super glue (I'm impatient) but I highly recommend using Epoxy for some of the stuff - Depron doesn't like superglue. Everything was built in 2 evenings with lots of interruptions from phone calls and people dropping in to see why I was swearing so loud

Wings:
3 sheets of 3mm depron cut from the wing template. Glued 2 sheets together, then cut them roughly at the COG line. Glued one carbon spar (5mm x 0.5mm x 1m) in there. Now added one sheet of glass fiber (the lightest I could find) around 40cm wide and epoxied it into place at the center. Gave the wing some weight so it could dry.

TOP 3mm + 3mm + Glass + 3mm BOTTOM

I also cut flaps, though they are not required. Since I didn't find the correct servo for it yet, I just taped the flaps back on. Ailerons are cut out a little smaller than on the plans, simply because I knew it was going to fly fast.

Boom:
For boom I used a 8mm diameter carbon tube. Length will be included in the pictures. I cut it at the very end just so I didn't need to adjust the COG (adjusted the boom length and rudder/tail position instead ). Be sure to wrap kevlar roving or your wife's/mom's sewing thread around at the end and superglue into place because cutting carbon tubes messes with their stability.

To glue the boom onto the wing, remove 1 sheet of 3mm depron 8mm wide at the bottom, along where you want the boom to sit. Now the glass fiber comes very handy, since it will give you a good surface to glue the boom to. Make sure it's roughly a 90 degree angle, then epoxy into place.

Hint: Score the depron lightly where you want to remove it, then use a "minus" screwdriver and simply run along the 2 cut lines. It comes off quickly and beautifully.

Battery:
I used a 3S and split it into 2 parts. 2S and 1S. See the picture to get an idea. This was done to reduce drag and shift the weight a bit. I scored & removed the 2x 3mm depron at the top of the wing until I reached the glass fiber sheet, then put the battery into the "hole" created (2S side facing back). The ESC was about the same hight as the 1S in front so I taped it to the battery. Then both were taped to the wing and boom.

Motor:
Took a small block of hardwood (balsa will do fine, didn't have any at hand). Drilled 8mm hole into it (or whatever size your carbon rod is) at a roughly 90deg angle. If you want to compensate for motor intertia (some measure ~3-5 degrees, I do it by accident) do that here - not really needed but will improve handling. Roughened the carbon rod at front, stuck it through the hole, super-glued into place. Motor then super-glued to the woodpiece (use screws if you want ... my way is faster ). Now was a good time to solder ESC to the motor.

Rudder:
Rudder was cut out (2x 3mm glued together) and then sanded into a good shape. Also cut out the rudder "flaps" and hinge-taped them on. I used glass to glue it to the wing, after measuring COG with the vertical stab and rudder taped on. Rudder was placed on the boom and held at 90deg angle, then I wrapped glass from the left side to the right, running through the bottom. Used 3 sheets of glass here, simply because I forgot to compensate in the COG "measurement" that the rest of the boom that I hadn't cut off yet also has weight.

Vertical Stab:
Original supra features some really slick and sexy design which moves the whole stab instead of "flaps". Wasn't patient enough for that, so instead I epoxied the servo to the boom (again at 90deg, using same technique as with the rudder). Then I removed a bit of the vertical stab that I had cut out already (you probably know the deal by now ... 2x 3mm, sanded into airfoil shape, "flaps" added with hinge-tape, additionally stabilized with 2mm x 0.2mm carbon spar). After that I super-glued the vertical stab to the servo and added some of the thin glass fiber to stabilize it a bit more. Works like a charm. See pictures above for more details.
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Old Dec 03, 2008, 09:02 PM
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Here is the wing-plan ... despite having a 3-piece layout it should be one piece. The wingspan is also 106cm (I warned you - I don't calculate or measure !!!) so you'll either need to print at a reduced size or remove a little from the wing center to make it fit onto the typical depron sheets
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Old Dec 03, 2008, 09:19 PM
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Forgive me father, for I have sinned ...

One last note for the people building this: The original supra has 3.4m wingspan. This one has 1m. So you can resize the tail and stab by 3.4 and then make them a bit "fatter" (50-75%). Also, the horizontal stab can be a lot wider if you want (+50-100%). Use common sense - if it looks awkward it's not going to fly

Feedback and comments appreciated. Video coming soon.
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Old Dec 03, 2008, 09:49 PM
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Oh, almost forgot ... the obligatory "nose-shot" (to see the low profile/drag) and a side-shot so you can verify she looks like or at least resembles a Supra.
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Last edited by trappy; Dec 03, 2008 at 09:59 PM.
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Old Dec 05, 2008, 11:38 AM
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video added to the first post. hope you enjoy. Please let me know any improvements or suggestions.
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Old Dec 05, 2008, 06:55 PM
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Quote:
Originally Posted by trappy
video added to the first post. hope you enjoy. Please let me know any improvements or suggestions.
Very cool project, I like where you are going with it. It really seemed like it would be hard to see against the snow and the over cast sky since it is white/light colored.

Cheers
Ron
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Old Dec 05, 2008, 08:11 PM
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Thanks, Ron!

Visibility was worse in the video than "live", but yeah, I wouldn't have flown if this was more than a prototype. The main wing is really nice (although the flaps are useless ... the plane can be slowed down really well using elevator), the vertical stab needs to be improved and also the rudder servo is just adding weight and not really being of any help. Overall it's a fun project but now that the servos for the real Supra have arrived I might put it to rest for a while

If there is continued interest I will improve the plans and make another model / maiden video
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Old Dec 05, 2008, 08:17 PM
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Quote:
Originally Posted by trappy
Thanks, Ron!

If there is continued interest I will improve the plans and make another model / maiden video
I have the interest, and of course a few other interests in front of it but it is winter times so I am sure I will get to it before spring.

Ron
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Old Dec 05, 2008, 08:38 PM
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Ok. I expect to take on this project again mid January early February. Since the plane itself takes only about 5h to make, I guess there will be results around that time too
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