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Old May 19, 2014, 10:04 PM
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Aerogance's Avatar
United States, CA, Ventura County
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Kinetic Sweeper

As promised, here is the video of the Kinetic Swept Wing "Sweeper" glider from Spencer Lisenby:

Transonic (2 min 54 sec)
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Old May 20, 2014, 01:38 AM
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I wish you the best with your new design.
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Old May 20, 2014, 11:22 AM
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Rexburg, ID
Joined Jul 2008
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Wow. Would be nice, though, to see launch and landing.

Spencer, you say this thing is ugly, but I think it's the coolest thing I've seen in a good long time. Best of luck with this, and may the wind (and structures) gods smile upon you.

-David
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Old May 20, 2014, 03:36 PM
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Huenfeld, Germany
Joined Oct 2006
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Looks promising!

Next step is eliminating fuselage and tail for minimized drag!

Ted
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Old May 20, 2014, 03:59 PM
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I have more videos, including the high speed flight and landing. The video came out inverted (thank you iPhone!) and I just haven't had the time to edit them yet.
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Old May 20, 2014, 04:08 PM
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Some interesting "features" of the KSW kinetic swept wing. The CG is behind the root trailing edge. The wing has 2 flaps per side but the inboard flaps are not used during landing in order to eliminate pitch up. The wing uses a complex snap flap program where the ailerons travel up to fight tip flex. The KSW has a long carbon shaft spliced into the tail boom to achieve adequate tail moment. Spencer had to remove a lot of nose lead to get the CG back far enough to be flyable. Although the KSW is technically a "Frankenplane", Spencer used all top-shelf radio components including bearings. The KSW Sweeper is friggin' awesome! We predict all DS planes will have swept wings within 5 years
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Old May 20, 2014, 05:50 PM
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Pacific Palisades, CA
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Very curious to see how the center panel was done. Seems like there would be some real complications in reinforcing that spar at the root with the 25 degree angle.
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Old May 20, 2014, 08:50 PM
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New Zealand, Auckland
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Is the swept design to allow the airframe to approach or go over the speed
Of sound ?
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Old May 20, 2014, 09:35 PM
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Quote:
Originally Posted by screamin' eagle View Post
Very curious to see how the center panel was done. Seems like there would be some real complications in reinforcing that spar at the root with the 25 degree angle.
I asked this very question to Spencer, and basically since the center panel does not have to house landing gear or fuel tanks (and can be heavy), it is pretty much all carbon. think of a spar cap from LE to TE.

To reduce stress, increasing the mass of the wing panels can counteract the upward bending moment during high g turns. Creative control surface mixing further counteracts the bending moment. There is a lot to this wing, the traditional slap-n-go approach doesn't work with wing sweep.
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Old May 20, 2014, 09:41 PM
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Originally Posted by Jets:) View Post
Is the swept design to allow the airframe to approach or go over the speed
Of sound ?
It has been estimated by Joe Wurts (and can be verified audibly) that the flow over parts of the airframe is supersonic at speeds around 500mph. Wing sweep, as is used on jetliners, would theoretically delay transonic drag rise and prevent control inversion at high subsonic speeds.

Many of us have dreamed of building a swept wing DS contender, but Spencer is the first to make this a reality. He is pioneering without a doubt. It is exciting to watch from the sidelines as he works out all the intricacies to make a sweeper work in the DS flight environment.
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Old May 21, 2014, 01:15 AM
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Quote:
Originally Posted by screamin' eagle View Post
Very curious to see how the center panel was done. Seems like there would be some real complications in reinforcing that spar at the root with the 25 degree angle.
Like Aaron said, the center panel has alot of carbon in it. The swept sparcaps meet at the root and overlap each other by 3-4" In addition to the swept sparcaps, I also have additional layers at the root which are triangular shaped with the fibers running perpendicular to the centerline. Kind of like the letter A but with the inside of the triangle filled solid with full thickness sparcap. I tried to flex the center panel on the bench and couldn't get much out of it. The main source of flex on this plane will be from the joiners which I made out of carbon prepreg rather than steel to keep the weight reasonable. I think the plane is flying well enough now to take the extra weight of steel joiners. Only problem is I permanently glued the carbon joienrs into the tip panels because I had to do some tapering to make them fit...

Quote:
Originally Posted by DS-Ted View Post
Next step is eliminating fuselage and tail for minimized drag!
Ted
I've been advised by a really smart guy that the inertia of the fuselage might be worth the extra drag when it comes to fighting freedom body flutter. Seems this is the usual speed limiter on swept flying wings. I do plan on making one from the molds with full length control surfaces to be flown without the fusealge and tail. It won't be a perfectly tuned wing but with full TE control surfaces, I can create the necessary twist. Have to rig some winglets to it and put all the battery and radio gear into the center panel before joining.


Quote:
Originally Posted by Jets:) View Post
Is the swept design to allow the airframe to approach or go over the speed
Of sound ?
Just to get a little closer. The sweep delays the extra drag due to compressibility by the cosine of the sweep angle. So with my 25deg sweep, instead of having the drag increase begin at m=0.72, it will be delayed until m=0.79.


I don't have any expectations of this model to set any records. I just wanted to begin experimenting with spar placements and layups to combat the inevitable wing twist from high loadings. I probably hit 40G in the 344mph flight and didn't have any twist bad enough to cause any unwanted behavior. That's better than I thought we'd see... Once things do become overstressed, then we can do a little spanloading to help out. I had to get creative to get the CG back far enough anyway. A little tip weight will help.


Quote:
Originally Posted by rothlisburger View Post
Wow. Would be nice, though, to see launch and landing.
-David
I can help on half of that request. My contour battery died about 3 minutes into the flight

Sweeper launch (0 min 38 sec)
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Old May 21, 2014, 01:45 AM
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I mentioned a quick and dirty method of making the molds for the swept center panel. First, I went down to Jason's and he CNC hotwired a top and a bottom plug from surfboard foam with a trough along the LE. This avoided a lipped out LE from the kerf of the wire. Next, I stuck the left and right halves together and down to a flat granite table with 3m77. Then I sucked down some thin (2mil I think) painters drop cloth to the table over the plugs. This kept me from having to surface, paint, and wax the plugs. I then laid up the molds directly onto the plastic film. I just used some lam resin for for the surface coat so I could see how things were going and prevent any bubbles. The molds came off the plugs really easily and the plastic peeled right off the molds no problem. I did a very brief sanding and polishing then waxed up for the first part. All told, after the plugs were cut, it took no more than 6 hours to produce a functional set of molds. I could have spent more time to get the finish perfect but figured it wasn't necessary for a quick prototype.
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Old May 21, 2014, 03:42 AM
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timbuck's Avatar
gold coast australia
Joined Aug 2008
5,590 Posts
Awesome spencer
I got a heap of pics on my iPad of guys doing proto types exactly like that and similar. Using a female foam piece and pulling carbon wing straight from the plug. Great way of doing rapid proto types of wings for race cars etc
Great to see this thing fly well done
I've always thought a swept wing with 2 boom's could be built very strong and also help with stopping the wing from flutter , might be worth the drag.
Interesting to see how your wing goes with out a fuse .

Tim
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Old May 21, 2014, 04:11 AM
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Australia, QLD, Elimbah
Joined Jan 2005
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Slightly off-topic

As soon as I saw the Sweeper, I recall around 1982-'83, a pair of brothers in my club developed the "Talon".
The Talon was a swept wing, T-tailed sailplane developed for F3B when the speed task was still only 2 laps, not the 4 laps it is today. You'll see in the images that there are quite a few swept wing sailplanes but the Talon was designed and built for speed.

Sorry to interrupt, I just thought I'd share and acknowledge your developmental quest.

David
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Old May 21, 2014, 07:23 AM
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New Zealand, Canterbury, Christchurch
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Quote:
Originally Posted by Larrikin View Post
As soon as I saw the Sweeper, I recall around 1982-'83, a pair of brothers in my club developed the "Talon".
The Talon was a swept wing, T-tailed sailplane developed for F3B when the speed task was still only 2 laps, not the 4 laps it is today. You'll see in the images that there are quite a few swept wing sailplanes but the Talon was designed and built for speed.

Sorry to interrupt, I just thought I'd share and acknowledge your developmental quest.

David
Are a couple of those 'gems' in the photo the swept wing Graupner Cumulus 2800 of the early 70's? Rudder / elevator only, not even spoilers, was also used for F3B in it's day. My first RC glider, I still have it. Also not too dissimilar to the Sweeper, except in strength...
Richard
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