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Old Oct 08, 2009, 05:27 PM
Onward through the fog.
Cybernaught's Avatar
Bohol Philippines
Joined Aug 2008
1,566 Posts
Quote:
Originally Posted by davereap
Steve... have a read on the Goolie thread http://www.rcgroups.com/forums/showthread.php?t=990577
Mixing is done at the radio using rudder / throtle mixing.
Some wild manouvers are possible and it will also knife edge on the differential..
Finless..I dont know, I am still woried about using two motors

Will it be worth it, I think so, it should certainly be interesting. With two motors and 26+oz thrust I expect it will go up fairly well.

DZ1. ...Ken
please view this thread http://www.rcgroups.com/forums/showthread.php?t=629435
It shows the whole of the testing that was carried out.
For yourself try replacing any conventional wing...use a KFm4 to replace a symetrical profile or a KFm2 for a more lifting section like clark Y..
You will be pleased..Also check out the building time, I used to make conventional built up balsa wings, that takes a while, doesnt it, A simple KFm wing can be finished whilst you are still pinning the balsa one together..A straight chord wing can be cut, glued and covered in a hour.. easy
For general flying the KFm sections are hard to better, however I dont believe they can replace everything, I havnt yet seen a high performance glider wing being replaced... or an ultra fast racer...note a KFm2 has exceeded 100mph and thats fast enough for me
Saying that however the KF wings will beat most everything for anti stall and range of speed in flight..
The best example is the Zagnutz vs the Zagi.. I have both, both will fly fast, but the zagi will stall at a not too slow speed whist the Zagnutz keeps flying, untill it stops, then it still doesnt stall but it parachutes down, perfectly controlable.. all down to the KF steps..
Agreed, Dave,
KFm2 and KFm4 are all I use and the conventional foils are just too much bother when the Notched foils have performed so well. I can do a wing in about 15 minutes. Actually cutting the 3 pieces per side, laminating, truing the centers with a sanding block and final gluing take about 1/2 hour to 45 min. With a coffee and smoke once the glue gun has heated up.

I am still struggling with the fuselage for the canard. Also wing spread, fore and aft, to get the best balance without making it too touchy on the controls. I'ts coming out way tail heavy. This new build is actually a good reminder for me about why I don't like fuselages and tails anymore.

I'll check out the link but I'm not sure I want to go to the trouble.

Steve.
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Old Oct 08, 2009, 07:53 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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I was out in the yard the other day and a nearby aircraft caught my ear, it turned out to be a BD-5 or something very much like it. A canard with swept wings with tiplets turned up on the ends. Power was an IC motor of some kind. It was just visible for a few seconds and was gone.

We get some unusual aircraft over at the Bar Harbor/Trenton airport from time to time. Some of the the people that have summer homes out on Mt. Desert Island also like other expensive toys. There was a privatized Douglas A-4 Skyhawk out there at times when I first moved here in 2001. Haven't seen it recently.

The B-17G Sentimental Journey cam clattering over the house one day at about 1,500 feet or so. That was a thrill. I went down and put $300 in the maintenance kitty and took a ride on her. Got to do the takeoff from the bombardiers position. That the highlight of my airplane rides, it even outranks my having landed on an aircraft carrier one time in a C-2 Grayhound.

Jack
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Old Oct 08, 2009, 08:57 PM
just Some Useless Geek
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Chicagoland
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Brag, brag, brag. [fume, fume, pout, whimper]

Well, at least I have my cheap toy airplanes to play with. [ahem]
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Old Oct 09, 2009, 06:16 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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It ain't quite as good as you make it sound, Marty. I'm in the same boat except for the occasional thrill.

I sent you a PM with a link the draft plan I made for the Smarty Pants, when you get a chance look at that and maybe we can get those going. I really liked the way that flew in your front yard.

My Divinity 32 is just a little too fast for yard flying in the amount of room I have. A standard approach and landing is to pick a soft tree and run in to it at eye level or so...

Jack
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Old Oct 09, 2009, 06:21 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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davereap wrote:

"..Heres my latest project... a cross between my KFm4 Superfly clone and the Goolie..."

I built a SuperFly out of FFF but it wouldn't fly as built. I had it way too heavy for the wing area. Maybe I need to put a bigger motor on it.

I found the sound of the prop in a slot designs to be quite annoying compared to a trailing edge pusher. Is that just me or do others find it the same way? I can't help but wonder if using two motors will make twice as much noise? And make it twice as annoying?

They SuperFly guys have played with dog bone shapes and angles cut on the back edge of the slot to quiet them down. I guess when you get a bunch of those flying indoors it can get pretty noisy.

Jack
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Old Oct 09, 2009, 09:39 AM
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j2m2t2's Avatar
AZ
Joined Feb 2007
513 Posts
Quote:
Originally Posted by jackerbes
davereap wrote:

"..Heres my latest project... a cross between my KFm4 Superfly clone and the Goolie..."

I built a SuperFly out of FFF but it wouldn't fly as built. I had it way too heavy for the wing area. Maybe I need to put a bigger motor on it.

I found the sound of the prop in a slot designs to be quite annoying compared to a trailing edge pusher. Is that just me or do others find it the same way? I can't help but wonder if using two motors will make twice as much noise? And make it twice as annoying?

They SuperFly guys have played with dog bone shapes and angles cut on the back edge of the slot to quiet them down. I guess when you get a bunch of those flying indoors it can get pretty noisy.

Jack
Yes my Firefly is very loud with the rectangle prop in slot but it is so much fun to fly. I went with KF2 on that also.

My KF2 Firefly exhibits the same thing my KF2 glider did when made from 9MM EPP, power off glide results in a 45 degree descent while the airframe stays level. Ive now read in a few places that people are calling this parachuting.

Is this a result of the laminar flow being interrupted at the step?
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Old Oct 09, 2009, 11:08 AM
Jack
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The parachute maneuver is also called the elevator by some. But it is really an endearing and useful quality once you've found it and played with it a little. I've never seen the parachute maneuver work as well on the other KFm builds as it does on the Zagnutz in KFm1 so I think that might relate to the step being on the bottom. The KFm1 is really one of the least used of the various KFm builds.

"..Is this a result of the laminar flow being interrupted at the step?..."

Tony65x55 pondered on that and discussed it (over three years ago) in this post in the thread that was the forerunner to this thread. The post is here:

http://www.rcgroups.com/forums/showp...8&postcount=84

In fact, his explanation of "why the KFm flies the way it lies" it is about the only one that is at a lower technical level and that gets through to me. And it might be the best explanation of the KFm airfoil that we have here. So I'm going to quote it here:

In Aug 30, 2006 Tony65x55 wrote:

//Quoted material follows//
"I've been thinking long and hard about the KFm and why it flies the way it does and I may have some answers. More likely, new questions.

I think the step is important as it creates the lift but not in terms of the size of the step but more as the angle between the step and the LE. That is to say, the height of the step determines the angle of the airfoil's underside.

I think the underside angled portion of the airfoil does the lifting. On the KFm Wing the lower wing root angle is +4 degrees. Air striking the LE parts and goes up and down. The air flowing over the upper surface is deflected 0 degrees but the airstream hitting the lower surface is deflected downward under higher pressure at +4 degrees, creating the upper/lower pressure differential and pushing the wing up (viola..lift!).

As AoA increases, the airfoil maintains its upper/lower angle of attack differential, always deflecting the air downward 4 degrees more than the angle of attack of the upper surface.

On a conventional airfoil the air must follow the sloping rear section of the airfoil, which at 0 degrees AoA is already at a 8-10 degree slope away from the airstream. This slope away from the airstream make it much easier for the airflow to detach itself from the upper surface and when it does...stall.

The KFm airfoil would have to reach an AoA 8-10 degrees greater to place its upper rear section at the same AoA as a conventional airfoil. At these extreme angles of attack drag becomes a much greater force and the airfoil can no longer maintain it's altitude without a great deal of power and so begins to sink. However, it has not yet stalled and so it maintains it's extreme AoA and mushes down, without the nose breaking through the stall. Simply reducing the extreme AoA restores a lower drag and the airfoil simply resumes normal flying.

This would account for the KFm's extreme stall resistance. Unfortunately, the by-product of the step required to create the angle on the underside of the wing is drag. The air rolling around in a vortex behind the step is drag city. Fortunately, the step is relatively small in the big scheme of things and the aircraft can still perform normally. As drag increases as a square of velocity it will, however, have a limited top end to the speed envelope. But within it's regular performance envelope of slow speed flight, it does perform very well.

That's it, I finished my silly theory. I'm probably full of it but after two weeks of pondering this, that's what I came up with. Any (polite) comments are welcome.

Tony"
//end quoted material//

I think that answers the question and it might also explain why the KFm1 does the parachute best. I think the step and resulting vortex of air off of the step being beneath the wing in the KFm1 is what makes it parachute so well.

The other KFm's, 2, 3, and 4 will slow down, pitch up into a high AOA, and start a descent also if you have enough deflection in the elevons. But they don't have quite the same slow descent and wonderful steering control that you see in the KFm2 Zagnutz.

Jack
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Old Oct 09, 2009, 12:35 PM
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United States, IN, Indianapolis
Joined Oct 2008
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KFm on a 3D foamy?

I recently built a Regal (http://www.rcgroups.com/forums/showt...ighlight=regal) with a KFm2 (as designed) and now I'm hooked KFm airfoils. My question is, has anyone tried building a profile 3D foamy with a KFm wing? I would think the the KFm4 or KFm6 would be most appropriate. I'm leaning towards trying a KFm6 on my next 3D foamy. I assume that since the 6 is designed to fly slower than the 4 that it might be better suited to slow 3D type flight? Would this add too much weight to this type of plane? Would a KFm wing be helpful on a 3D foamy since many of them are already design to perform well in post-stall and near-stall manuevers well? Any thoughts?
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Old Oct 09, 2009, 01:36 PM
Slipping the Surly Bonds
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Attica, MI
Joined Dec 2006
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Quote:
Originally Posted by Sailor Jerry
... My question is, has anyone tried building a profile 3D foamy with a KFm wing? I would think the the KFm4 or KFm6 would be most appropriate. I'm leaning towards trying a KFm6 on my next 3D foamy. I assume that since the 6 is designed to fly slower than the 4 that it might be better suited to slow 3D type flight? Would this add too much weight to this type of plane? Would a KFm wing be helpful on a 3D foamy since many of them are already design to perform well in post-stall and near-stall manuevers well? Any thoughts?
Here is the answer to your question Jerry. A 42" KFm4 EPP Yak55.

http://www.rcgroups.com/forums/showthread.php?t=1102742

Ken
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Old Oct 09, 2009, 05:03 PM
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Ashford. Kent. England
Joined Feb 2005
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jackerbes take a look at my superfly clones all KFm4
http://www.rcgroups.com/forums/showthread.php?t=977954
38" using 6mm is an excellent flyer ..19oz+ battery ...5.1 oz sqft+2oz when the wheels are fitted
and a 24" using 3mm still unflown...6oz + battery...4.7 oz sqft

Now the twin BW motor Superfly/Goolie 30" using 3mm is going to fly at 13.5oz....4.3 oz sqft....with 26+oz of thrust available it should prove interesting...edit...Ive named the new twin delta the CYCLONE

Goolie specs added
Wingspan: 28" (710mm)
Flying Weight: 9.5oz (270g)
Wing Loading: 4.4oz/sqft
Controls: 4 (Elevons(2), Throttle, Rudder mixed into Throttle)
Flight Time: ~10 mins


jackerbes
what span and weight was your version
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Old Oct 09, 2009, 05:06 PM
just Some Useless Geek
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Chicagoland
Joined Oct 2008
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Quote:
Originally Posted by jackerbes
I sent you a PM with a link the draft plan I made for the Smarty Pants, when you get a chance look at that and maybe we can get those going.
I just now sent you an email with a drawing attached. Had to make a new one because I was having no joy editing the PDF. Anyway, it should be sufficient to get going.

I am in the process of building a very slightly upscaled Smarty Pants with my pastor (a building/training kinda thing) and another one for myself out of EPP. Plus, I need to finish the one for the guy in my club before Monday's meeting. Heh. Smarty Pants all over the place! We owe it all to you, goldguy! Smart Dart XS rules!
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Old Oct 09, 2009, 06:41 PM
Jack
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A Useless Geek wrote:

"..I just now sent you an email with a drawing attached..."

Right, just got it! Thanks.

Jack
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Old Oct 09, 2009, 06:45 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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davereap wrote:

"..jackerbes take a look at my superfly clones all KFm4..."

Right, I used your plan, at least in part, for the one I built. I used FFF and when I tried to maiden it I found it was grossly underpowered. It is stuck up in a corner of the basement, still in near perfect/unflown condition and I just need to get back to it and repower it.

I'm a better/smarter flyer than I was when I tried to fly that last, it was about a year ago, maybe I just need to get back up on that horse.

Jack
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Old Oct 09, 2009, 07:04 PM
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Neenah, WI
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Here's an arrangement that I used to stiffen a wing with a KFm4, step airfoil. I cut lightening holes in the original 1/4 inch thick, foam wing material. Then, added 1/4 inch thick blue foam top and bottom step-pieces to the wing. A 1/8 x 1/4 balsa strip glued to the back edge of each step-piece greatly increased the beam strength. The top and bottom step-pieces covered the front 40% of the wing chord.
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Old Oct 09, 2009, 08:41 PM
Onward through the fog.
Cybernaught's Avatar
Bohol Philippines
Joined Aug 2008
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Quote:
Originally Posted by davereap
jackerbes take a look at my superfly clones all KFm4
http://www.rcgroups.com/forums/showthread.php?t=977954
38" using 6mm is an excellent flyer ..19oz+ battery ...5.1 oz sqft+2oz when the wheels are fitted
and a 24" using 3mm still unflown...6oz + battery...4.7 oz sqft

Now the twin BW motor Superfly/Goolie 30" using 3mm is going to fly at 13.5oz....4.3 oz sqft....with 26+oz of thrust available it should prove interesting

what span and weight was your version
Dave,
Has it flown yet?
Are you set up with differential throttle on the motors?
Steve.
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