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Old Feb 26, 2008, 10:12 PM
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Diablo speed plane build

I've decided to build another Demon series pylon racer plane. This one is the Diablo. It will be the biggest (and hopefully fastest) Demon plane yet. Wingspan is 36" (the Demon V1 was 26", V2 was 30", and the Fire Demon is 34"). I'm venturing into uncharted territory (at least for me) and making a fiberglass wing for it.

The motor has already been built. It's a GoBrushless Triple stator 8 magnet motor. It is wound as a 6 turn AaABbBCcC sequence. It should be around 2800 kv.
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Old Feb 26, 2008, 10:31 PM
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Wing cut

I made two wings for this plane; one out of solid balsa and the other foam. The foam wing is 1/2" thick at the middle and 1/4" thick at the tips! I hope it won't flex too much. The balsa wing is 3/8 thick in the middle and 1/4" at the tips. The thin wings should cut drag significantly.... I hope
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Old Feb 26, 2008, 10:38 PM
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Foam wing glassed

I think I'm calling it quits for the night. I just got done fiberglassing the wing. I used 5 oz fiberglass cloth and West System epoxy for rigidity since the wing is so thin. My scale shows it weighs 6 oz

The glassing process:

First I filled all the foam pores with spackling to keep it as light as possible. I then sprayed the wing with super 77 adhesive and wrapped the fiblerglass cloth over the wing. Then I mixed my epoxy and ran it over the wing. I then wrapped the wing in wax paper and spread out the epoxy.

It isn't perfect, but it should work fine.
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Old Feb 27, 2008, 09:39 PM
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Fuselage build

Tonight I built up the fuselage. I used my favorite balsa sheeted foam method. The balsa was 3/16" rather than the usual 1/8". I figured another 1/2 oz was worth it for the durability.

I started by sanding down a 2X4X30" foam block to the curve I wanted the plane to take. Then I cut out my fuselage halves and sprayed the sides with Super 77 as well as the foam block. After sticking them together I put a 1/8" balsa sheet on the bottom using Gorilla glue.

The fuselage weighs in at 2.5 oz. The wing needed a second coat of epoxy to smooth it out. So now it weighs 7 oz. So I'm now up to 9.5 oz (7.8 with the solid balsa wing) and I don't even have a tail or electronics

I know some people (or perhaps a certain someone who shall remain nameless) think heavy planes fly like crap, but I think this one's speed will more than make up for it's heavy weight.
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Old Feb 28, 2008, 11:50 AM
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I prefer my planes on the heavy side. Takes wind better, less prone to the whims of the wind currents, etc. Gives me more "feel" and authority over what the plane is doing. I try to gain weight via the strength mods I want on a particular design, and save it in other areas if I can.
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Old Feb 28, 2008, 09:10 PM
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Taking shape

Tonight I started melting out chamers and installed the elevator servo. I melted the chamber using a special hot wire tool I made inspired by Tom Hill (critterhunter). The servos will be buried deep inside this model as will be the linkages and even the wires

The wing will be mounted to the fuselage via two blind nuts. At this point with the battery, esc motor, elevator servo, and receiver, the plane weighs 18 oz with the fiberglass wing and 16.5 oz with the balsa wing. I anticipate the finished weight to be 22 oz. Quite heavy, but it will be stiff, strong and most importantly FAST.
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Old Feb 29, 2008, 02:03 PM
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Looking good Alex!

Call me if you want to hitch up to fly Saturday or Sunday. I'm putting the finishing touches on the Dual Boomer tonight, including paint.
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Old Mar 01, 2008, 09:04 PM
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Diablo complete!

I finished the plane after only 5 days construction! No record for me, but this encomassed a few experiments. AUW on this one is 23 oz which gives it a wing loading around 16 oz/ft, which is still acceptable, but I'd rather be around 14 or so.

I added a functional rudder to the plane because it was nose heavy and I'd rather add function than dead weight.

The wing came out stronger than I ever imagined. I could prbably break bricks with it! Ok, maybe not that strong, but I can hold the plane by it's wingtip and shake it without the slightest hint of flex.

In leiu of the stiff wing, I decided to cut a V-notch int to wing to make the aileron. I went through several blades to accomplish this, but in the end the ailerons came out nice. They are a bit stiff to move, but that will hopefully keep the from vibrating in flight.
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Old Mar 01, 2008, 09:11 PM
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Flight report

Ok I had to maiden this today. The suspense was nearly killing me. I started out with an APC 6X4 prop favoring torque over speed in case I needed it. I'm glad I went with the bigger prop. Out of my hand it immediately went into a steep climb. 6 clicks of down elevator and it was flying straight and level. I had it going about 80mph or so on the straight aways. Not bad, but I wanted more.

I went back to the car and replaced the 6X4 with a 5.25X6.25 prop. Again I launched it, but this time it took some time for it to get up to speed. After 1 minute I got up the nerve to go WOT, and all I have to say is WOW! I'd guess it was going 105-110 mph. On top of that, the plane would snap into turns, rolls and loops with incredible speed and grace. I made the mistake of yanking back on the elevator at full speed and executed a loop of no more than 12' diameter, again no wing flex

This is perhaps the fastest plane I have ever built. I'll wait for the speed trials for the official speed ruling. I wonder if it's faster than my Banshee hotliner?
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Old Mar 02, 2008, 06:36 PM
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Yea, loved how that plane flew today and can't believe how stiff that thin wing is.
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