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BUFY v2.0 - Scratch builder contest #2

Old 05-30-2009, 07:18 AM
  #26  
Larry3215
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I finished dolling up BUFY a whiloe ago but just got around to shooting a few pics.

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Old 07-05-2009, 04:11 AM
  #27  
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I didnt have my camera with me today which is tooooo bad. I could have shown you some good pics

By the way lightning DOES strike twice!

Some of you may remember last year I posted a video of the first version of BUFY ejecting its flight pack durring a knife edge 1/2 loop and then landing itself with no damage.

Well, today I did something very similar with BUFY v2.0

I was up fairly hi practicing knife edge spins. This plane will wind up pretty tight if you enter it just right. Go into a hover then kick the nose over to horizontal with one wing straight down and then give it full power and full down with just a touch of top rudder. It spins like a top right around the CG.

Looks very cool!

Unfortunately, it must be causing huge G forces on the battery pack because it came loose from its straps and unplugged itself righ in the middle of one of these spins

I was out over some dense forest and tall trees at the time but lucky for me it came out of the spin, righted itself and was gliding straight towards me - whew! But - just as it got to the edge of the tree line it stalled and went into a spin and ended up stuck in a tree about 20 feet off the ground.

One of my more athletic flying buddies climbed part way up the tree and handed it down to me.

I couldnt believe it but there was almost NO damage again!! One servo popped loose from the wing and some minor scratches and dings.

I am one lucky dude
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Old 07-05-2009, 12:21 PM
  #28  
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Larry, i will say you are Lucky allright. I fly over a Jackpine forest and i have had to cut quite a few trees down to recover my planes. I own the property that i fly over though and when i cut a tree down i know i don't have to worry about that one anymore.
Nice lookin plane, how big is it?
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Old 07-05-2009, 03:55 PM
  #29  
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The tree section we fly over is so dense with under growth and Black Berries, that its a real chore just to move through it. Ive searched for downed planes for days only to discover that I had walked within 3 feet of the plane several times without seeing it!

This new version is 64" long by 72" span. All up weight as it is now is 6 lbs 10 ounces.

Thats about 7 or 8 ounces more than the profile fuse version.

The wing has 1008 sq inches of area and the fuse has about 750 sq inches of side area.

Power is a cheep Ammo inrunner in an MEC Monster box geared about 5/1 spinning a 22x12 prop. Around 850 watts or so peak on a 6S1P A123 pack.

Its a hoot to fly

Last edited by Larry3215; 07-06-2009 at 07:01 AM.
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Old 07-06-2009, 12:18 PM
  #30  
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Thats a big plane Larry, i would not be able to land one that big here as my clearing is too small. I could launch it ok and fly over the trees but getting it down for a good landing would be rough. I would have to do a parachute landing.Ha
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Old 07-06-2009, 05:20 PM
  #31  
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You could do what I call a short field approach instead. Its basically a flat spin that isn't very tight. More like very tight flat circles with the nose held slightly up but not quite in a harrier. Its still flying on the wing.

The Yak can be held inside the space of a 1/2 basket ball court and land easily. You do need to straighten it out at the last second and you will have maybe a 20 foot run out.

My Mega Capricorn can do the same thing and come down and land almost in its own length! That's what ridiculously low wing loading will do for you
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Old 07-06-2009, 07:09 PM
  #32  
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Yes i made a couple of the Capricorns and flew them here, they are a blast and fun in the winter too.
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Old 08-23-2009, 04:20 AM
  #33  
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Ive been flying BUFY quite a lot lately and Im getting it dialed in pretty well. Its now my second favorite plane after the Mega Capricorn.

I have decided to do some mods to get it tweaked a bit more. Its flys very well but it could be a bit better.

Im going to change motors so I can prop for a bit more power. Im right at 600 watts peak now which is just under 100 watts/pound. With the 22x10 prop that gives me just enough power to pull slooooowly out of a hover and a reasonable if slow top speed.

Im spending a lot more time at higher power levels and very slow speeds and the motor I have in there now - Mega 22/30/4 - is coming down on the hot side. I also want a little more pullout speed so Im going to change over to a larger motor and change the gear ratio for closer to 800-900 watts on the same prop.

I'll probably also go to 9S up from the 6S A123 Im running now to get some more run time. Im barely getting 5 minutes now the way I've been flying lately.

Thats going to up my weight some and all the extra weight will be ahead of the cg, so Im going to have to re-do the hatch so I can get the packs further back.

After i fly it with those mods I may also add some foam to the leading edge of the wing and make the ailerons wider to gain some more wing area. If I do that I'll also enlarge the rudder and elevator some more.

Then I'll see if it needs anything else

Oh - I need to repair my wheels. Ive been playing with one wheel landings and take offs and Ive broken both wheels loose from the hubs
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Old 08-23-2009, 08:30 AM
  #34  
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Larry, great thread and a really impressive plane.

I'm very interested in your wings - they appear like you haven't shaped them at all to create lift. ie they look just like the foam you've cut out. Is this the case - in your videos it flies beautifully and I thought you'd need at least a bit of shape??
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Old 08-23-2009, 11:01 PM
  #35  
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You don't need airfoils to fly. Shockflyers are dong great 3D and they don't have airfoils.

I think they are mostly used to create more lift. Correct me if I'm wrong
A shockflyer wing will probably create more drag then lift.
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Old 08-24-2009, 01:38 AM
  #36  
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At light wing loadings and slow speeds - basically all 3D and most all sport type flying - there is very little penalty in having a flat wing with square leading edges. In fact, its possible the square leading edges delays the stall somewhat and are batter than a shaped leading edge - if you have a flat plate wing.

For gliders, where low drag is critical, or hi speed planes or very heavy planes its better to have an airfoil.

BUFY flys great. My XXL Polaris is larger and heavier with a higher wing loading and also flys a LOT faster and still does fine on a flat 'airfoil'. My Mega Capricorn is another example.

So, for 3D machines for sure and most sport models there is no significant penalty in having a flat wing.

That said, airfoiled wings do create more lift and do have less drag. They also have more inherent strength and twist resistance due to the shape and depth of the structure. For the same strength a built up wing can be lighter and will be stiffer and less susceptible to twisting.

But, if you're into KISS, a flat wing will probably do just fine
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Old 08-24-2009, 01:51 AM
  #37  
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!!!! BUT !!!!
A profile-wing does look SO much better




Here's a plane I'm making without airfoil
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Old 08-24-2009, 02:10 AM
  #38  
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No argument from me on that point. Hense the 'U' in BUFY. It stands for Ugly
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Old 08-24-2009, 04:05 AM
  #39  
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Thanks guys, appreciate the quick replies.

It has raised my curiosity though - everything I was aware of until now about flight stresses the importance of wing shape to create lift.

So I assume we're just putting so much power into these things that we're able to somewhat overcome the lift issue... or have I missed something?
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Old 08-24-2009, 06:03 AM
  #40  
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Our models operate in a different realm from full scale planes. We can get away with things they cant due to the relatively low wing loading and relatively hi power loading.

Its kind of like why a bumble bee can fly when they "cant" aerodynamically.

So, unless your going after hi lift or very low drag - carring heavy loads for example or thermal duration soaring or pylon racing or a heavy war bird or jet - all you need is a bit more angle of attack to get all the lift you need.

The same thing applys to any symmetrical airfoil actually. They dont generate any lift unless there is a positive angle of attack.

If you need lots of lift at low speeds you can always camber a flat plate and it works great too - a GWS slow stick wing is a great example.

Our flat plate airfoils are just relatively thin, symmetrical airfoils. Some aerodynamics guy from Boeing - I think it was Steve Schumate IIRC - said recently that they have a coefficient of lift of about .8. Not all that bad really.
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Old 08-24-2009, 02:46 PM
  #41  
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Hi Larry,
Thanks for clearing that up. Completely forgot about the angle of attack - it's a pretty important element!
Cheers,
Alex
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Old 09-01-2009, 04:44 AM
  #42  
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Ive been messing with the power system.

Changed the gear ratio and motor for more power but that reduced flight times too much.

So tonight I changed the motor again to a Medusa 36-60- 1300 - down from the 36-60-1600 - and went up to a 6.4/1 ratio. Im going to run some 9S A123 packs tomorrow and see how that goes. If I did the calcs correctly, I'll be pulling about the same amps at about 50% higher peak power.

If Im carefull with throttle management I should get roughly 50% more flight time too - maybe
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Old 09-03-2009, 03:15 AM
  #43  
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I had gotten several flights in on the new power system over the last few days. I like it a lot!

Today I was extending my flight times to see how much longer I could run on the 9S packs. I got a little carried away and hit LVC at a bad time....

Pancaked in pretty hard. Ripped out the landing gear and motor and smushed up the nose a good bit.

Its all easily fixed but its still a bummer. I had just got it dialed in perfectly!

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Old 09-06-2009, 09:19 AM
  #44  
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you're flying on 9s

Too bad you crashed I hope you can fix it !!

Good luck

(my bignasty is dead too :p) Making new 3D plane ...

[media]http://www.youtube.com/watch?v=HdVco7on8QA[/media]
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Old 09-06-2009, 06:38 PM
  #45  
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Ouch!

Glad you didnt have much damage

Im still debating whether to fix this one or finish the other one Ive started last year.....
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Old 10-05-2009, 01:21 AM
  #46  
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Do u have plans for this ugly piece of art?

PA
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Old 10-05-2009, 02:00 AM
  #47  
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Sorry PA. This was a TLAR build all the way.

However, you could take pretty much any Yak plans and just scale them up. The only places I departed from the basic Yak outline was making the rudder larger than scale and making the fuse taller in cross section.

As far as details on how I did the wings etc, I posted lots of pics but didnt take any detailed notes myself and didnt get exact measurements.
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Old 10-05-2009, 08:11 PM
  #48  
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Ok, thanks. It shouldnt be to hard if i just follow your pics. I will do this a bit later as i am working on a projest right now.

PA
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Old 10-05-2009, 08:35 PM
  #49  
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Good luck and keep us posted on progress
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Old 03-12-2010, 07:49 AM
  #50  
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Well, I finally got around to fixing BUFY up and getting back in the air

While I was at it I shortened the nose about 1.5" which allowed me to move the motor back. Now I can get the CG I want without having the packs so far back in the fuse.

It flys great!
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