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Old Mar 30, 2012, 01:46 AM
Assault the sky
secretspy711's Avatar
United States, CO, Denver
Joined Aug 2004
153 Posts
More progress...ailerons, winglets, hatch

I ordered a Turnigy Park 480 1320kv motor and a 8x4.5 folding prop.

I may have to make a motor-less version just for slope-soaring. I really like how it's turning out.
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Old Mar 30, 2012, 01:50 PM
Ed @ Experimental Airlines
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United States, AZ, Phoenix
Joined Sep 2011
459 Posts
That's looking very nice, lots of space in there. "We don't need no steenking molded-in bays". Good to note the spar paths, thanks for that. I'll personally probably go with tubular fuselage, for hand-launching purposes and a few other ancillary reasons. I'm already down to 9 fingers so I'm pretty careful these days. I think your center section is still more efficient for flight though.

Ed
(PS: not an RC accident)
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Old Mar 30, 2012, 03:03 PM
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United States, NY, New York
Joined Nov 2011
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Quote:
Originally Posted by ExperimentalAir View Post
That's looking very nice, lots of space in there. "We don't need no steenking molded-in bays". Good to note the spar paths, thanks for that. I'll personally probably go with tubular fuselage, for hand-launching purposes and a few other ancillary reasons. I'm already down to 9 fingers so I'm pretty careful these days. I think your center section is still more efficient for flight though.

Ed
(PS: not an RC accident)
That is a nice looking fuselage indeed.

Ed,
I imagine if you mount the prop like this guy did
FB Drone part 1 (4 min 40 sec)


and attach fuselage tube underneath the wing, you'll be albe to put in-line wheels on it and take off from ground.
To me that would be awesome, but I've seen very few wings that can do that
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Old Mar 30, 2012, 07:00 PM
Just Me
United States, OR, Salem
Joined Apr 2006
877 Posts
Al, that is one great link you posted, wonderful resource. I dl'd a couple, ran the dat files through my foil program and they plotted out great. Thanks very much for that link.

Also like the looks of your launcher, may have to put one of those together for testing my canard design.

Don

Quote:
Originally Posted by atone1 View Post
I've been flying a similar design of this type of wing for over 2yrs.
Here's some things that might help you guys out.
I use this site for airfoil pattern templets; the NACA ones that have symmetrical cambers are good for level and inverted flight. http://www.worldofkrauss.com/foils/l...mebeg&letter=N
The NACA 0010-34 is what's on most of my wings. Here's how to use this site.
Click an airfoil name to see it displayed. Once there click on the picture of the airfoil to go to it's plotting page. Under the display area you can change the size and other perimeters of that particular airfoil. To size it just change the inch # from 3 to 14 and hit enter.
Here's how I build the inside of my wings. The space between the ribs is for the battery and I cut holes in the side of the ribs to run wires for flight gear.

On the break down wing project: why couldn't you make it like the balsa planes?
A 3 piece unit where the wing panels have a plywood rib with a hole for the spars that's sleeved with a fiberglass and epoxy tube glued to the inside of the panels. Thumb screws hold the wings to the wing panels. Blind nuts on the back of the plywood ribs and the main stress is on the tubes and spar assembly. The ends of the tubes would need stops on them so the spars can't slide and allow the panels to flap at high speeds. The fuselage section could be used as a modular unit so other size wing panels could be added on later. This would be a great test bed for trying out other wing airfoil types without having to build the center section. Lots of R&D will need to be done on this as you figure out if it will work with one spar or two. One spar might work on the 40" version with pegs and alinement holes in the plywood ribs. I think this breakdown modular wing system is more suited for wing sizes over 48" as that's when they get hard to transport and the added weight will come into play. A heavy wing is not fun to fly, IMO. Fiberglass practice arrows from any sporting goods store could be used as spars.
Have you notice how they act as gliders if you keep the weight down and C/g balance right? I gain more flying time by shutting off the throttle and playing around with the thermals.
Well, that's some of my thoughts on these wings.

I built this PVC launcher to sling these wings into action just by pulling a string.
Al.
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Old Mar 31, 2012, 02:43 AM
Assault the sky
secretspy711's Avatar
United States, CO, Denver
Joined Aug 2004
153 Posts
Quote:
Originally Posted by ExperimentalAir View Post
That's looking very nice, lots of space in there. "We don't need no steenking molded-in bays". Good to note the spar paths, thanks for that. I'll personally probably go with tubular fuselage, for hand-launching purposes and a few other ancillary reasons. I'm already down to 9 fingers so I'm pretty careful these days. I think your center section is still more efficient for flight though.

Ed
(PS: not an RC accident)
Thanks! The Zephyr is a cool airplane, but I'm already spending a bunch on the electronics, why would I want to spend another $130 just on an airframe when I can do this for less than 1/10th the price? If this one works out well, I'll try a bigger one. Flying wings are just so much fun.

P.S., since I'm using your Armin method, and it has elements taken from the Zephyr and Deep Reaper in terms of shape and power characteristics... I'm calling this the "Cheap Armyr"

Saw your intro video where you tell about your hand. I had no idea they could move a finger to become an opposable thumb. That's pretty cool
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Old Apr 03, 2012, 11:18 AM
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Joined Jan 2012
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bajiwing meet Ex Air

I've been working on a hybrid design using Ed's building techniques in a bajiwing style. I wanted a fuse to be able to mount my motor and stash batteries and electronics. Its a full 30" right now but i'll cut it down to 20 or less more than likely.

The wingspan is about 44". I started the wing with the template by Rob Mackenzie but tweaked a couple things.

I was wondering what the consensus was on expanding foam? I have a spar (black line drawn in the photo) but I was thinking of putting some foam in the space between the leading edge and the wing former. And maybe putting a couple strips of it from front to back between the former and the trailing edge. It seems like there should be room for the foam to expand without ruining the shape.

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Description: Inside the wing.  I laid down 3 pieces of foam vertically and it seems very rigid.  I'll probably put some bbq skewers along the length.

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Description: Folded over.  The root height of the former is about 1".  Tip height about 0.5"

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Description: Mockupormer.
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Old Apr 03, 2012, 01:38 PM
IFO's are planes too
atone1's Avatar
Petersburg, Va.
Joined Dec 2008
432 Posts
I found this site on model building and saw your airfoil shape and here's what this guy says on flat bottom airfoils. He's been building planes since the early 80's.
http://www.airfieldmodels.com/inform...t_airfoils.htm

"Flat-Bottom Airfoils
Don't use true flat-bottom airfoils for anything.
So called "modified" flat bottom airfoils are excellent for slow, gentle flight.

"Flat Bottom" Airfoil
True flat-bottom airfoils are a poor choice for any design. They are next to impossible to trim properly because they are extremely speed sensitive. It may be possible to trim this trait out, but it means spending hours tweaking the wing incidence, decalage and engine thrust.

I've never flown a model with a flat-bottom airfoil that could even come close to being trimmed as it was built. I don't particularly enjoy cutting the tail off my planes numerous times attempting to get it right.

The rest of this discussion refers to modified flat bottom airfoils.

Flat bottom airfoils are used for powered aircraft that are willing to make the compromise of having more drag in exchange for slow flight or high lift capabilities. They do not penetrate the air well but can stay aloft at very low speeds. I have built a handful of models having flat bottom airfoils that can hover right in front of me because the aircraft's minimum flight speed was below the wind speed.

For example, if the model can fly at 10 MPH and the wind is blowing 15 MPH then the model can fly backward (relative to the ground) at 5 MPH. As far as the air is concerned (which is the only thing the airplane cares about) the aircraft is flying forward at 10 MPH.

An aircraft that is identical except for having a symmetrical airfoil will have a higher minimum flight speed."
Even though he talks of conventional aircraft,I built a flying wing with a flat bottom and it would flip upside down and I never could fix it. Maybe you'll have better luck with your flat bottom design. That one was my first wing build and for the rest of my wings I went with a symmetrical airfoil.

"I was wondering what the consensus was on expanding foam?"
I have used the great foam in a can stuff and find it messy and there's no way to stop the expansion if you use too much. Maybe you could weight it down and let it expand out the ends.
AL.
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Old Apr 03, 2012, 02:13 PM
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United States, NY, New York
Joined Nov 2011
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I see where this guy is coming from , but how about all of those 3D foamies that are completely flat, top and bottom? How about numerous delta wings on this forum that have either flat bottom or are flat on both sides? Kfm airfoils are mostly flat on the bottom, and some consider them to be amazing.

I'm far from a great pilot, I'm a beginner, but as you can see in my video I'm not really struggling with my wing, which has completely flat bottom.
Maybe in larger scale, high-precision aircraft intended for competition it makes a great difference, but I've had a few planes with flat bottom airfoil and didn't really notice any problems. They all flew

Regarding foam. I tried that Great Stuff foam from home depot and it does expand nicely and weight very little, and makes wing very rigid, however it really is messy. You need to have your wing halves separated and opened, do not seal off root or tip cord, spray a few lines of foam from root to tip, and only then fold the wing. As long as there are openings for extra foam to escape , it shouldn't mess up the airfoil, and you'll end up with a wing that will take quite a beating.
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Old Apr 03, 2012, 03:53 PM
IFO's are planes too
atone1's Avatar
Petersburg, Va.
Joined Dec 2008
432 Posts
T-89, all I can say is this is the info I found and my experience with FB airfoils.
Do a couple of test wing builds and make one with a FB and one with a symmetrical airfoil and see which one you like. Let us know your results.Now they need to be the same dimensions and power setup in order to judge the outcome. I did this test and I don't like the FB airfoils in my wings. I do have 3 flat plate scratch built foamy profiles that fly great. I had this thought too; make the winglets removable and don't glue the spars so you can change the foam spar and create any airfoil you would like to test. Been thinking of this for a glider wing to see which one glides the best on these wings.

Here is something I think is strange: I build and fly RC kites which the fabric covering lifts up in regular flight to create a curved bottom airfoil like you see on a lot of trainer planes. They glide a little with the throttle off in the wind, but I noticed they really glide a lot better inverted and I can even find thermals to soar in.
I can double my flight times by just punching it and go strait up to 500' and shut the throttle off; go inverted and fall in with the birds and have a blast soaring.
Right side up I'm do to 50' in a minute, and I do have places where the fabric is glued to the frame. There's only a slight curving of the airfoil top and bottom.
Right side up it does slow flying with a good amount of speed and inverted it has sustained lift and soaring capabilities.
You can take whatever from this, but in the end do what's right for you.
Al.
Al.
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Old Apr 03, 2012, 09:38 PM
When pigs fly rc
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USA, NY, Chester
Joined Apr 2008
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dollar store wing with leds at night (4 min 5 sec)
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Old Apr 04, 2012, 08:58 AM
Ed @ Experimental Airlines
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United States, AZ, Phoenix
Joined Sep 2011
459 Posts
rcrich - Call SETI, they're here! That is bad-ass!
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Old Apr 04, 2012, 09:18 AM
Ed @ Experimental Airlines
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United States, AZ, Phoenix
Joined Sep 2011
459 Posts
Quote:
Originally Posted by atone1 View Post
I found this site on model building and saw your airfoil shape and here's what this guy says on flat bottom airfoils. He's been building planes since the early 80's.
http://www.airfieldmodels.com/inform...t_airfoils.htm

"Flat Bottom" Airfoil
True flat-bottom airfoils are a poor choice for any design. They are next to impossible to trim properly because they are extremely speed sensitive. It may be possible to trim this trait out, but it means spending hours tweaking the wing incidence, decalage and engine thrust.
This debate will go on forever. Naturally there is a very refined science behind airfoil design but also a lot of subjectivity and prejudice, and other considerations beyond absolute performance.

The core philosophy with the folded foamboard wing is that we can build at least a cambered airfoil in 1/10th the time at 1/10th the cost of a rib-and-spar airfoil. Incurring, say, a 20% degradation in performance due to the flat bottom doesn't seem quite as detrimental if economy and speed of build are important. My opinion is that in powered electric aircraft with thrust:weight ratios of .7 and up, you're not going to notice as much difference anyway.

I'm looking at the 11 foamboard airplanes on my wall that I've designed and built all with flat bottom, cambered airfoil wings, 0-degree angle of incidence on the wing and tail, and they all fly nicely to phenomenally well.

As a private pilot and light-sport aircraft owner I do respect the science of airfoils. If I had a deep budget and retiree amounts of free time, I too would be building at least some of my RC planes with "correct" airfoils.

The BajiWing is proving itself to be a very accessible and effective design and I think it and its variations will be a great success. I mean, 3 hours and $10? Who can argue with that?!

Ed
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Old Apr 04, 2012, 10:46 AM
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United States, NY, New York
Joined Nov 2011
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rcrich, that is awesome! Where did you get those LEDs? Please tell there is a place besides HK that offers decent price and shipping time I have a few 1s 300-500mah batteries lying around that I wouldn't mind putting to use with my 30" kfm wing
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Old Apr 04, 2012, 11:23 AM
When pigs fly rc
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USA, NY, Chester
Joined Apr 2008
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hobbypartz!
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Old Apr 04, 2012, 03:06 PM
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United States, NY, New York
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LEDs purchased, 30in version of bajiwing is coming up
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