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Old Jan 30, 2010, 10:39 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,449 Posts
Build Log
IBCrazy's Vampire FPV project

Now that I have several hours behind the sticks with FPV gear, I think I'm ready for a little bit more performance. I want to build a fast airplane that is not a flying wing. I have built several renditions of my Demon pylon racer, which seemed to be the best suited platform for this.

Despite every plane I own having the props outside the camera angle, this one will have the prop viewable. I will be incorporating pan capability, but not tilt since I don't plan on flying this one incredibly high up.

Here are my goals:

AUW of 36 oz or less
Top Speed > 75 mph
Capable of transport without disassembly
Durable enough to withstand my less than stellar landings

-Alex
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Old Jan 30, 2010, 10:48 PM
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Long Island, New York
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Have you thought about a Funjet?
I just finished my Stryker, it comes in at about 36oz.
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Old Jan 30, 2010, 11:01 PM
Engineer for Christ
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Amherst, VA
Joined Jun 2006
10,449 Posts
Wing cut

The first thing I usually do is design the wing, then build the rest of the airplane around that. I need enough wing to lift the added weight of the FPV gear, but not so much wing that it's cumbersome to fit into my compact car. I also need it to be fast, which means a thin fiberglassed wing.

Now the questions are: how big do I make the wing? and What airfoil do I use? I decided on a 42.5" wingspan. This will comfortably fit inside my car, but give me fair stability to rolls. I now need the chord dimensions. Central chord is 8-1/8" and the tip chord is 6-1/4". This gives me about 2 square feet of wing. For the airfoil I chose the USA 49. It is only 5/8" thick, so it's going to be very fast.

I cut the wing out of pink EPS foam with a hot wire bow. I place the foam between two airfoil templates which are screwed to a board. Then I connect a car battery charger to my bow's .025" welding wire and drag the bow through the foam right along the templates.
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Old Jan 30, 2010, 11:05 PM
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Amherst, VA
Joined Jun 2006
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I have my Snyper flying wing. It is comparable to a Stryker. I wanted something that wasn't a flying wing. Besides, my Demon series planes always have been a blast to fly.
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Old Jan 30, 2010, 11:07 PM
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That wing came out awesome, I can't wait to see the end product.
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Old Jan 30, 2010, 11:14 PM
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Amherst, VA
Joined Jun 2006
10,449 Posts
The fuselage

As much as I like the balsa sheeted foam method to make a fuselage, I'm going to need more room with all of my FPV gear. Thus I'm just going to make a balsa box. For a little bit of durability, I'm going to use 3/16" balsa rather than 1/8".

I'm sizing it as small as possible to reduce drag, but still make it roomy enough for all of my gear. Since my battery is a little over an inch high, I went with 1-1/2" sides joined by a 2" base board. Length is 34".

I then needed a tail. I'm making this out of 1/8" balsa. I decided on dual rudders for two reasons: 1. it will help keep the plane straight in a sharp turn, and 2. It looks awesome

I simply glued the parts together with Welder adhesive.
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Old Jan 30, 2010, 11:24 PM
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Amherst, VA
Joined Jun 2006
10,449 Posts
Wing build

With the glue drying on the fuselage, I can make a little more progress on the wing. I need to join the halves, add a carbon rod, then fiberglass it.

To join the wings I used a mix of Gorilla glue and wood glue in a 5:1 ratio. This foams up to 10 times it's size and really adheres to EPS. Light and strong, that's what I want.

I also needed to cut a channel for a carbon rod. I just dragged a hot soldering iron down the bottom of the wing. I put a little bit of the Gorilla glue mix in the channel and inserted the carbon rod. The foam filled most of the gaps.
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Old Jan 30, 2010, 11:43 PM
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Amherst, VA
Joined Jun 2006
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Fiberglassing

Tonight I'm going to finish up with fiberglassing the wing. I use West System epoxy and 2 oz fiberglass cloth. It takes about 1 oz of epoxy for every square foot of wing to get a good adhesive base, so I mixed up 80ccs.

The trick with this epoxy is that heat both thins it out and speeds up the cure time. Normally it takes this stuff 24 hours to cure, but I wanted to do both sides tonight.

I completely covered the bottom of the wing in epoxy, leaving about 1/8" from the leading edge uncovered. I then heated it up with my heat gun and got it around 130 degrees or so. Not too hot, but hot enough to speed things along. After about 3 minutes of maintaining that heat, I let it cool down. Now the epoxy is tacky and ready for the cloth.

I placed the cloth with about 1" overhang and worked it into the epoxy with my fingers. Once I had all the wrinkles out of it, I heated it up again with the heat gun. I made three runs, three minutes a piece, with 5 minutes between for cool down. The heat thins out the epoxy and allows it to soak into the cloth better, then when it cools it is significantly harder.

Once I did the backside, I repeated the process for the top side. Now I have both sides covered, however, the surface is dry. I now need a skim coat to smooth it out (and add a bit more strength). Again I mixed up 80ccs, however this is enough to do both sides with some to spare. I just wiped the whole thing down with the resin. It is now setting upright and I'll let it cure overnight.

I could have saved a bit of weight and made a slightly better wing with a vacuum bag system, but I don't have the money for one of those at the moment. Besides, I've made dozens of wings this way and they all worked out well.
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Old Jan 30, 2010, 11:46 PM
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USA, NY, New York
Joined Nov 2008
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Beautiful wings , looking forward the progress.
I order my last wings from http://flyingfoam.com/ , first class service !!! they do EPS and EPP also, wising computer CNC or Computer Numerical Control, precision foam cores without the need for templates.
I feel also tired of flying Flying wings only, so I am building from scratch 96" by 8" chord EPP thermal ship for FPV, foldable to fit in golf travel case. My wings are SD7037 9.20% airfoil. V tail may be, I dont know yet.
Cheers,
Georgi
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Old Jan 31, 2010, 01:11 PM
Engineer for Christ
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Amherst, VA
Joined Jun 2006
10,449 Posts
Covering

Before I went off to church today I took a little time to cover the airplane. I used my favorite two tone coloring scheme. A bright neon red tail in the back on a dark fuselage. The bright red tail makes it easy to identify the plane should I choose to land point of view or in the event I need to go looking for it after a crash.

The double rudder gives the plane a unique look. It also should help keep the plane level in a turn since I will not have rudder control.

I sanded the edges off the fiberglassed wing as well. The wing alone weighs 9.1 oz. Heavy, but very strong. It should easily support high G-force maneuvers. I still need to sand the wing smooth and then paint it. I figure I'll probably go with a two tone paint scheme on the wing as well.
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Old Jan 31, 2010, 01:28 PM
It just keeps getting better!
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Eureka, CA
Joined Oct 2002
1,533 Posts
Nice build!
I have a few pylon racers kicking around I've been planning on putting
cameras on. Looks like you'll beat me to it!
I also have a few hotliners that would be good choices.
Haven't got the nerve yet to cut them up.
One of these days!
Sure looks like fun.
-Dave
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Old Feb 02, 2010, 10:08 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,449 Posts
Motor trouble

Well, I thought I had a motor, but something went wrong. I rebuilt a Scorpion 2215. I wound it as a 5 turn parallel WYE in dLRK style. This is a 2.5 turn equivalent. It was expected to turn about 2100 kV. Unfortunately, I messed up the termination somewhere and it had significant braking effect. When I tried to dismantle it, I couldn't get the stator off the bearing tube. So for now, that motor is taking a back seat.

I decided to put my favorite motor in this instead - The GoBrushless GBX triple stator. This one is currently wound as a 4 turn WYE with 4 parallel strands of 26 AWG wire. However, I have a second stator which I might try my hand at 3 strands of 22 AWG. If I can get 3 strands of 22 in there, this thing will absolutely rip. It will be capable of over 42 Amps!!! The kV of the motor is 2150, which will spin a 6X5.5 prop with plenty of authority. If I can't, I'll go for the 3 strands of 23 AWG... still good for 35 Amps

The motor mount is my classic primitive fold over aluminum flat stock. It will be glued on with Shoe Goo. Nothing fancy, but it works.
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Old Feb 02, 2010, 10:13 PM
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Amherst, VA
Joined Jun 2006
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Ailerons cut

I cut ailerons in the wing tonight. They measure 8"X1-3/8". This should give me a more than adequate roll rate. These are "live" hinges cut out of the fiberglass wing. This reduces drag and offers a very stiff hinge. It keeps the part from vibrating at high speed.

I also setup the locating blocks for the wing. I used 8-32 nylon bolts. Why so small? In the event of a wreck, I want the wing to sever from the airplane. This will reduce the crash damage since the plane will no longer tumble once the bolts break free. It also takes the impact stress away from the other parts. Bolts are easy to replace
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Old Feb 02, 2010, 10:17 PM
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I have one dead Scorpion S-3014-16. You want it? Free
G
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Old Feb 03, 2010, 06:45 AM
Engineer for Christ
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Amherst, VA
Joined Jun 2006
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Absolutely! I love the 3014. I'll put it in my Scout V2 soaring airplane. I usually wind those 11 turn YY (5.5 turn Y equivalent or 13 turn Delta equivalent) with 2 strands of 23 AWG wire. You can spin a nice 11 or 12 inch prop with incredible authority. I might even go for the split angle offset LRK winding pattern AaACBbBACcCB - which spins a bit faster Unfortunately the waveform is distorted so I don't know if the speed controller will handle it too well.

If you can't tell, motors are my real bread and butter in this hobby. Most every motor I fly is a rebuild or scratchbuild.

-Alex
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