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Old Mar 15, 2011, 03:42 AM
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Livermore, CA
Joined Sep 2004
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Quote:
Originally Posted by Murman View Post
It wouldn't loop well because you forgot the elevator!
There called elevons! And it loops ok, just not as tight as I'd like.


I used to build with EPP sheet but it was too pitch sensitive, so I started cutting airfoils out of EPP block for a smoother flight.
But it looks like this simple Km2 airfoil flys just fine. I was able to cut the whole plane out of one 12x36" sheet of 9mm EPP. I could have used 6mm on the tails and strakes to cut the weight, but I wanted to keep it simple.
It flys perty easy, so it would make a good aileron trainer, and cheap too.
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Old Mar 15, 2011, 08:17 PM
If it flies, I will crash it
mxspode's Avatar
USA, CO, Westminster
Joined Jan 2008
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Wouldn't mind seeing some plans or this one Butch. I have recently started working with EPP and this looks like a pretty good candidate. Always wanted to give one of these a try. I have a 24" KFm wing with a 5 gram on it that would probably do the job.

Nice work,
Rob...
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Old Mar 17, 2011, 01:34 AM
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Livermore, CA
Joined Sep 2004
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Quote:
Originally Posted by mxspode View Post
Wouldn't mind seeing some plans or this one Butch. I have recently started working with EPP and this looks like a pretty good candidate. Always wanted to give one of these a try. I have a 24" KFm wing with a 5 gram on it that would probably do the job.

Nice work,
Rob...
Thanks!
I think it could be built several different ways and still fly stable.
The strakes seem to do there job and they, as well as the tails and fuselage could be about any shape. I used about 15 degree sweep, measured on one side. I went with a 4-1 aspect ratio and a mild taper. Because of the large prop taking up alot of the trailing edge, I went with larger ailerons.

For a 5g motor, you may consider 6mm EPP. The size of your prop would determine the distance between the tails.
I may put together a simular Km Boomer with elevator, using one servo on the ailerons and a 10g motor as well. Butch
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Old Mar 18, 2011, 12:30 AM
If it flies, I will crash it
mxspode's Avatar
USA, CO, Westminster
Joined Jan 2008
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Draw it up chief and I will build it, or even drop a few dimensions so I can get it close. These little motors make some amazing power for there size and in general I have trouble flying them due to the speed. My boss however seems to love the darn things.

Rob...
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Old Mar 20, 2011, 01:57 PM
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swanton, vermont
Joined Apr 2005
244 Posts
good info!

Thanks for the info! I followed your post in flying wings to here. I guesstamated the 15 sweep, (started building prior to reading) and used the wing C/G locater. I have 6" root & 5" tip for a C/G of 2.92. looks like what I have been searching for. Simple build with built in bounce factor + prop protection! How could ask for more.
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Old Mar 20, 2011, 07:25 PM
If it flies, I will crash it
mxspode's Avatar
USA, CO, Westminster
Joined Jan 2008
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Pretty close to what I have. I hope to test it as soon as my radio gets back from Horizon. Not sure which will be ready first the radio or the plane but it should be fun either way.


Rob...
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Old Mar 20, 2011, 08:04 PM
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Livermore, CA
Joined Sep 2004
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I'll go ahead and post some more pics and details. If you need anything else, just let me know and I post it.

I used a 15 degree wing sweep, thats about 4"s back on the tip, with a 28" wing. I ran a C/F tube spar, about 75% of the wing.
I went with about 30% back on the Km doubler, instead of 40-50% back, because the larger pusher prop takes up aileron length.
Therefore the aileron needs to be wider, more like a 3D plane, especially for slow flight responce. The problem is, that the Km step will have some ruff air just past it which may affect the ailerons preformance.
I may be wrong, but it does fly ok, so who knows!
For the elevons(ailerons), I used 6mm depron and sanded a slight taper on the back edge. I used CA hinges like on all the Boomers.
If you run a smaller/faster prop, you could change things around a bit, but I wanted good slowflight/parkflyer maneuverability.

The Tail pattern can be found on page 2, here on the Boomer Thread. I cut a 1/4" off the top and front to down size it. The dorsel fin can be any size. I added a carbonfiber rod under it, as you can see in the pic on the previous page. I glued it in it at the same time I glued the tail assembly on. The aft strake, under the tail is about 1 3/8" wide.

The fuselage is two 9mm sheets glued together with EPP glue(4693H 3M). If you use epoxy, it will be hard to cut out the wing/rx and battery slot. Wing slots are a pain to cut out level through thicker EPP. I used a block of wood and took a snap-off blade out of its handle to make a good cut. I cut the slot just a bit undersized and sanded it to fit.

To make it easier to fit the fuselage, I add a strip of EPP along the top of the wing, under the fuselage, as you can see in the pics. There's no need to add a CF spar to the fuselage, because the forward strakes stiffen it up just right.

The motor mount is 1/8", 5 layer plywood, glued on with epoxy, with the motor shaft centered to the wing, so no thrust angles. I used the servo screws to mount motor mount. Believe me they will hold well in 5 layer ply. I drilled out the holes and was working the screw in and out, but I still snaped one screw in half, so I just used 2 screws to mount the motor.

My C/G ended up about 18% back so far, thats about 3"s. I set in about 2 degrees of reflex, about maybe 4-5mm up at the back of the elevon.
With it trimmed for level flight at medium speed, it pulls out of a 45 degree dive decently, which may have something to do with the lifting Km airfoil.

I still want to mess with the C/G and reflex a bit.
Also maybe decreasing the size of the aft strake to help it loop a bit faster, but as it is, it seems to fly very stable, even in 10mph winds, at 4.5ozs RTF. Also, it has a near vertical climb.
Butch
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Last edited by Butch777; Mar 20, 2011 at 08:44 PM.
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Old Mar 20, 2011, 08:32 PM
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swanton, vermont
Joined Apr 2005
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thanks!

Thanks for the info & photos Butch! It looks like it will be a nice small lot flyer.
I have to wonder how it would perform as a small sloper? My wing is built, spar installed. Going to be on the road for next 2 weeks so be a while
until its done. Such is life.
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Old Mar 20, 2011, 08:43 PM
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Livermore, CA
Joined Sep 2004
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I have to be carefull when I launch these Boomer parkflyer types, because of the larger prop. So when I tossed this one, on a stormy/windy day, it seemed like it glided well, but it was hard to tell with all the wind. So it shouldn't have any problem sloping. Butch
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Old Mar 21, 2011, 07:26 AM
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swanton, vermont
Joined Apr 2005
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Nice sanding job!

Very nice sanding job Butch. I use drywall screen, 120 grit. and a razor. Works well, but takes time. It shows thsat you took the time necessary to complete proprely. I can not wait to get back adn finish it up.
Please keep the info coming, I will try to keep up while on the road.
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Old Mar 21, 2011, 02:36 PM
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Auburn, WA
Joined Nov 2005
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Butch, why the wood motor mount instead of a carbon tube? Any particular reason, or just cheaper solution?
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Old Mar 21, 2011, 05:22 PM
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Livermore, CA
Joined Sep 2004
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On the WildWing Boomers, the motor mount area was thin, so the tube went in aways to get some solid mounting, but this design lets me use a simple and yes, cheap firewall.
I say cheap, but the 12x24 sheet of the 1/8" 5 plywood was $20.00 at the hobby shop, but luckly it goes a long way. Butch
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Old Mar 30, 2011, 12:27 AM
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Joined May 2006
8 Posts
Any tiled plan file or build instructions...your boomer looks great and i intend to build one too!!

So how many mm EPP foam do i need?? 6mm for the fuselage and ?

Thanks a million!
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Old Mar 30, 2011, 02:33 AM
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Livermore, CA
Joined Sep 2004
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This latest Boomer is all cut from 9mm EPP and the elevons are 6mm depron.
I cut the whole Boomer from one 12"x36" sheet. The fuselage is 2 sheets of 9mm glued together.
Its a simple cutout and glue project, so above build notes and pics should be enough.
If you have any questions, just ask.
It could be built several different ways and using different Km airfoils, but that's up to you. I used the Km2 because it was a lifting airfoil and it does float quite well.

I used the 9mm because its a 28" wing. It could be built a bit smaller, but with the small 10g motor on a 2 cell it still has near vertical climb. Butch
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Old Apr 26, 2011, 10:09 AM
Kansas is windy.
pburress's Avatar
Wichita, KS
Joined Jun 2003
1,554 Posts
R/N Models Baby Boomer

Here's my R/N models Baby Boomer I built a few years ago. Quick to build and it's a great flyer- very quick and agile with a brushed IPS S2 motor. I'm sure it would be even better with a brushless motor.
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