|Jul 19, 2011, 12:25 AM|
My latest plane is a Multiplex TwinStar II that will be a platform for FPV. Specs:
Receiver: Futaba R319DPS receiver (72 MHz)
Servos: HS-82MG (tail servos moved to tail boom from nose)
Motors: eRC 900kv outrunners from Hobby Lobby (http://www.hobby-lobby.com/480_size_...33023_prd1.htm)
Props: APC 8x6 Counter-rotating; APC 9x6 CR; GWS 9x7.5 normal-rotating (different props for different scenarios)
ESCs: 18A Castle Thunderbirds
Battery: 3S one or more
Gyro: GWS PG-02 dual-gain, switchable via Tx
AUW (empty): 33oz.
AUW (2 2200 mAh): 44oz.
FPV weight (1 2200 mAh): around 50 oz.
I made a conscious decision to put quality components in this aircraft. I have purchased from a particular low-cost vendor before and was thoroughly disappointed in its service. This plane is an FPV platform and I won't take chances that one of my ESCs will just quit (see note at bottom), or that the batteries will pop while I'm in the air, or the servos will strip if I bump the control surfaces transporting it.
I did a number of mods including moving the tail servos, shaving the motor mounts to clear the motors, cutting a lot of foam out of the nose for more space, and cutting the hatch you can see in the third picture.
The paint job was designed in Inkscape and done with Krylon Fusion spray paint. I used a similar method as when I painted my Radian
1. Prep the foam for painting by cleaning with denatured alcohol and lightly sanding to get rid of the mold bumps.
2. Mask off paint sections. I used automotive vinyl tape 6mm wide for the main boundaries and masking tape for the broader areas. You HAVE to make sure you don't mask over paint because the masking tape will pull up the paint easily.
3. Apply the paint. One or two coats should be fine.
4. Touch-up with a Sharpie paint pen - the automotive tape didn't do a great job, but it was the only thing I knew that was thin and flexible.
5. Apply a couple of coats of Minwax Polycrylic over the top for durability.
This plane flies beautifully! I maidened it on a relatively still day and it flew very nicely. My other planes have a lot less mass and this plane doesn't fly like them. It just feels solid in the air. One interesting thing is it glides really well! It took me one-and-a-half soccer fields end-to-end to get down the first time. I realized after I landed that my spoileron switch was disabled. Next landing, I used spoilerons and could hold the nose up while coming in steeper and slower. On a second flight, I tried some aerobatics. Smooth! It performs very crisp rolls and loops.
I have flown the plane loaded to nearly to 60oz. The empty weight is 33oz. This means it carried almost its own weight in cargo and still was able to climb out at very high rate (50 or 60 degrees). Naturally, the stall speed increases, which requires a more powerful launch toss and a higher approach speed, but even with all that weight the TwinStar felt very light and maneuverable! Awesome aircraft!
I learned through experience that the counter-rotating props might not be the best idea. When the props spin the "normal" way the nuts holding the prop on tighten as they spin. When you reverse the spin direction without reversing the threads, they loosen! So unless you tighten your prop adapters extremely well, you may lose a prop, exactly what happened to me. I wasn't in the mood for experimenting with the plane's single-engine characteristics and dead-sticked it without incident. From now on, it's normal-spinning props for me!
I've been meaning to put up some more detailed photos so here they are. Can you tell I'm proud of this plane?
Note: Ironically enough, even though I went with what I thought to be high quality components, namely Thunderbird ESCs, I got burned. The exact scenario that I mentioned up above (ESC quitting) happened to me at nearly full throttle a a few hundred feet. The resulting asymmetric thrust put me into a graveyard spiral into an empty parking lot. So much for that!
Check out the video below for one of my first FPV flights!
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