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Old Feb 08, 2012, 09:32 PM
Terry Dunn
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United States, TX, Lubbock
Joined Jan 2001
852 Posts
Build Log
Popfly 2 Night Flyer

Keith Sparks, the man behind Park Flyer Plastics, is reintroducing the Popfly flying wing as a built-up depron model. For anyone not familiar with the original Popfly, it was a solid-foam indoor/outdoor model that was popular back when brushed motors and nicads were king.

Popfly2 Product Page

When I saw the new version, I thought it would make a great plane for night flying at the park down the street. So this thread will document my build of the Popfly2 as a night flyer…which isn’t much different from the stock Popfly2.

The Popfly2 will be a free plan in the May2012 issue of Fly RC magazine. Keith is doing his own build thread of the Popfly2 in the Flying Wings forum. Since I’ll be adding lights and using different gear, I figured that a build thread in this forum wouldn’t be too awfully repetitive.

I began assembly last night and got quite a bit done. Most of the onboard gear that I will be using is still en route, so I had to stop before adding the top wing sheeting. My plan is to use a Rimfire 200 outrunner motor and 3S-500 lipo for power. I’ll decide on a prop once I have the motor in hand and can test a few set-ups.

I'm installing LED strips and will power them with the flight battery. As Keith suggests, I am using Gorilla Glue for most assembly steps. But my foam-safe CA and low-temp glue gun are kept within arm’s reach as well.

Enjoy, and feel free to email me questions,
Terry
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Old Feb 11, 2012, 06:54 PM
Terry Dunn
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United States, TX, Lubbock
Joined Jan 2001
852 Posts
My on-board gear showed up Thursday...most of it anyway. The Rimfire 200s were on backorder. Hopefully it'll show up in a few days. In the mean time I thought I'd set it up for a Rimfire 250. The 250 is a little bigger and heavier than the 200. More importantly, it is a lower kV (1750 vs 2400 rpm/v). That means I'll need to run a larger prop.

With the stock layout even a 4" prop (what I plan to run on the 200) requires a little trimming of the elevons. Going larger than that requires a little more work. I moved the servos out one rib which will let me cut away more elevon area for prop clearance.

I was toying with the idea of adding a spar as well. Looking though my stash of carbon fiber, I found a small tube that was the perfect length to run between R5 in each panel. That seemed enough like fate that I was convinced to add it.

As I was planning the next few assembly steps in my head, I decided that I would be better off joining the wing panels before adding the top sheeting. This would let me make sure that the spar was properly glued at every rib.

As I write this, the top sheeting is drying, as is the initial strengthening of the motor mount. Next, I'll trim the top sheeting to install the leading edges and battery tray.

Terry
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Old Feb 12, 2012, 12:37 PM
Terry Dunn
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United States, TX, Lubbock
Joined Jan 2001
852 Posts
I had a few free minutes this morning so I sanded the sheeting and wired the LEDs. I added a strip of white LEDs along both leading edges. Keith provided clear plastic leading edge covers for this purpose. I'm not sure if they'll be a part of the kit or an option. It's hard to tell in the photos but I think the lights will be plenty bright enough for good visibility and orientation.
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Old Feb 12, 2012, 09:54 PM
Night Flyer
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United States, TX, Round Rock
Joined May 2005
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You're a fast builder. Will it be flying later this week?

Phil
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Old Feb 12, 2012, 10:02 PM
Terry Dunn
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United States, TX, Lubbock
Joined Jan 2001
852 Posts
Quote:
Originally Posted by phil007 View Post
You're a fast builder. Will it be flying later this week?

Phil
If only you knew how false that statement is! I move along okay once I'm in the shop. But, with 3 little ones, the shop doesn't see me often. That being said, I agree that the Popfly is coming along quickly. There just isnt much to it.

With any luck, I'll have a few free hours Tuesday. That should be enough to get her finished. Then I'll put her up if the weather clears. After a very mild winter, it's finally cold in Texas...as you know.

Terry
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Old Feb 13, 2012, 09:37 AM
Addicted to RC
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USA, TX, Houston
Joined Nov 2003
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Looks great Terry! Keep a list of tips for me when I start my build....

...next year.
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Old Feb 13, 2012, 11:54 AM
RC 4 Life
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Fort Worth, TX USA
Joined Feb 2001
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Wait till Gretchen sees it fly! as if that pretty smile could be any bigger.
I hope she has a few friends that can watch daddy fly it.
Kids love night flyers: the neighborhood dogs . . . .not so much.
Fly along the edge of the field tree line at about 50 ft and the barking will follow the model.

Carbon fiber rod for a spar? you must be planning on some speed.
Watch the weight of the motor tho, the ballast adds up fast .
Modifying it to a mid engine or a prop on the front may be needed if the motor is heavy.
Looking good!
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Old Feb 13, 2012, 01:29 PM
Terry Dunn
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United States, TX, Lubbock
Joined Jan 2001
852 Posts
Quote:
Originally Posted by sparks View Post
Carbon fiber rod for a spar? you must be planning on some speed.
Watch the weight of the motor tho, the ballast adds up fast .
It's well known that my airplanes lead hard-knock lives. So the spar seems like a good idea for a .1oz weight penalty.

Piecing things together, it looks like I'll be really close on the CG without the ballast nuts, but I am using a 3S-500 lipo. I'm thinking the finished weight will be right at 8oz. Not bad considering the weight of the lights and bigger power system. I guess we'll see if my weight prediction holds true.

Terry
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Old Feb 13, 2012, 01:32 PM
Terry Dunn
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United States, TX, Lubbock
Joined Jan 2001
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Quote:
Originally Posted by yarsmythejr View Post
Looks great Terry! Keep a list of tips for me when I start my build....
No tips...this one is falling together quite easily.

Hey, I'll build yours for you (before next year). It's the least I can do.
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Old Feb 14, 2012, 10:26 PM
Terry Dunn
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United States, TX, Lubbock
Joined Jan 2001
852 Posts
Well, I finished the Popfly2 tonight. Yes, it's heavier than I wanted, but all the numbers look really good. It's late, so I'll fill in the details later. For now, I'll let the photos tell the story.
Terry
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Old Feb 15, 2012, 12:06 PM
Terry Dunn
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United States, TX, Lubbock
Joined Jan 2001
852 Posts
I calculate the wing area to be exactly 288 sqin = 2.0 sqft
FWIW - I dont count the elevons as wing area on flying wings since they are not technically a lifting surface....they push down!

So the following numbers emerge:
AUW: 8.8 oz
Wing Loading: 4.4 oz/sqft
Power Loading: 124 watts/lb
Cube Loading: 3.1

All good numbers for a slow flyer with some spunk. We'll see how the reality pans out.
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Old Feb 15, 2012, 12:43 PM
Night Flyer
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United States, TX, Round Rock
Joined May 2005
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That's going to be a beautify night flyer. I still haven't decided on how I'm going to light mine up but it will be close to what you've done. The LEDs on the leading edge look great.

Phil
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Old Feb 15, 2012, 08:23 PM
Addicted to RC
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That looks great my friend. Can't wait to hear about the maiden flight.
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Old Feb 15, 2012, 09:22 PM
Terry Dunn
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United States, TX, Lubbock
Joined Jan 2001
852 Posts
Thanks Phil and Lee.

Now to back-fill a little build info: I always seem to make at least one bone-headed move during every build I do. The Popfly was no exception. After tinkering with the motor mount and getting it squared away, I decided to test a couple props to see which I should use. So I placed (not secured...just placed) the tray into its slot on the airframe and hooked the ESC to my servo driver and wattmeter. All was fine for a few seconds and then I saw the tray start to creep out of its slot. Before I could shut down the throttle, the whole thing jumped forward and the prop chewed up the starboard trailing edge. After a few choice words, I grafted in a scrap piece a foam and it was good as new...or close enough. In the end, the worst damage was the destroyed GWS prop. I can live with that.

Other notes are embedded in the photo captions. I hope to maiden it in the next few days.

Terry
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Old Feb 16, 2012, 09:14 PM
Terry Dunn
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United States, TX, Lubbock
Joined Jan 2001
852 Posts
Maiden complete!

Sorry, but I dont have photos. It was a last-minute sprint out the door with 2 kids in-tow (neither quite ready to man the camera).

I call it a success on two counts:
1. The airplane flew and sustained absolutely no damage.
2. I verified that Keith is not joking with his CG location.

I thought I could fudge the CG just a smidge, but it made the airplane VERY pitchy. I didn't bring anything to ballast the front. So after a few laps, I brought her in very carefully and called it good. I'll get the CG where it should be and try again. Hopefully I wont swell my AUW too much. But as I always tell people: Better to be heavy than tail-heavy.

Terry
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