Talus: High Aspect, Constant Chord Swept Wing Revolution - Page 2 - RC Groups
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Apr 02, 2006, 03:05 PM
Needs brain lubrication
biber's Avatar
If you want performance over a broad range of flight regimes without involving a tail, a swept wing with winglets is the way to go.
Not as easy to design and set up as a plank, though.
But, as mentioned by alex, there is the opportunity of using self trimming flaps.
No need of using stable airfoils, a fairly low negative cm is acceptable.
Another thing to consider, a little twist, let's say around 1.5 upto 3, has proven to be not noticably detrimental to speed performance on many swept wings.

Although I appreciate the efforts to bring a fully molded swept wing to market, I don't think the particular choice of airfoils is too reasonable:
SD7037mod/evolving to SD8020mod
I'd rather go for one airfoil with more a moderate cm than the 7037 and do it without blending into a symmetrical section.
SD7003, MG06 and similar are quite promissing candidates, while the MH-types are still a good recommendation.

Well, just my 2 euro cents...

biber
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Apr 02, 2006, 06:28 PM
Registered User
Aio_1's Avatar
It's nice to see a flying wing that doesn't look like a zagi!
I've always liked flying wings and was happy to see them appear in the form of EPP wings etc but now 10 years later the only thing most people think of if you mention "flying wing" is a zagi type foamie.

Quote:
Originally Posted by EdSoars
...Swept wings only need washout if the root airfoils have a high pitching moment (the X-wing does). The Talus has a low pitching moment airfoil, and has ZERO washout. This allows the builder to construct it on a flat bench which makes it much easier to control warps during covering....
If you don't use any washout in a swept wing you lose some of their advantage over an unswept wing. With a swept design you can avoid inefficient heavily reflexed aerofoils and instead use an aerofoil with a more modest positive Cm (pitching moment coefficient) or even a slightly negative Cm. If you don't use washout your aerofoil MUST have a reasonably significant positive Cm or you cannot balance an appropriate CG position. Significant positive Cm can either be achieved by the original aerofoil selection or by altering the aerofoil through added reflex at the control surfaces later. I think either way it will tend to give worse L/D than a more modest positive Cm or slight negative Cm with tip washout. This is because negative Cm aerofoils tend to have better general characteristics and also the washout allows a more elliptical lift distribution which improves the efficiency of the wing as a whole.

Aidan
Apr 02, 2006, 06:52 PM
Needs brain lubrication
biber's Avatar
Compared to a Zagi style wing, it will be a blast to fly anyway.

But besides that, I would second Aio's statement.

In the concept of swept wings there is generally still quite some potencial left more or less untouched.

biber
Apr 02, 2006, 06:54 PM
Throw Caution to the Wind
Lavawing's Avatar
Some photos from my proto-build. Most of this will probably change, but this is how mine is shaping up so far.

(Must get to work, so I can get some in-air shots!)


(Edit: forgot to add photos.)
Apr 02, 2006, 07:43 PM
Cho Oi! Hay Qua!
tomi's Avatar
Nice... I like how it breaks down for traveling..
Apr 02, 2006, 09:25 PM
Striving to Rip the Bring
raptor22's Avatar
I third Aio's statement.

It should still be fun, but it may not be as high in performance as it could be.

Additionally, swept wings tend to tipstall unless you have some aerodynamic or geometric washout.

--Alex
Apr 02, 2006, 09:26 PM
Striving to Rip the Bring
raptor22's Avatar
Quote:
Originally Posted by IwantaJet
John,

The ritewing site is down. Do you have a current link?

Roy

He is updating his site (it wasn't updated in about a year). To get the video, just PM klique directly.

--Alex
Apr 02, 2006, 09:51 PM
auto-tune remix
slopemeno's Avatar
Heres some info in the "Just in Time". I dont know much about it, other than I have some cores coming for it. Its a 2 meter constant chord, symmetrical airfoiled, 4-surface wing. Its primarily for light lift aerobatics, so I'm told. Kinda like the "Jart" in that its freeware, so no ripping it off into a bunch of kits.
Apr 03, 2006, 12:10 AM
The lift is out there....
barefootbass's Avatar
Hey Ed! Good to see you in the forums again. Did you take down the Upslope site? Just tried linking to it from my old bookmarks with no dice. I like the design. Lava will you have it ready in time for the WCSC?
Apr 03, 2006, 11:35 AM
Needs brain lubrication
biber's Avatar
JIT 3 'Johannes':
http://www.rc-network.de/forum/showthread.php?t=41006

biber
Apr 03, 2006, 11:40 AM
It could happen...
InTheLift's Avatar
Slick project LW...love the way it breaks down too.
Apr 03, 2006, 07:30 PM
find me @samotage
samotage's Avatar
Looks like this could be a sweet project. I remember reading about the 3.3m Taborca a 6 flap delta in RCSD in December 2003... a very cool looking toy.

http://www.rcsoaringdigest.com/pdfs/...SD-2003-12.pdf

Sam.
Apr 07, 2006, 12:15 AM
Registered User
EdSoars's Avatar
Good comments. The airfoil is the MH-44, which has a small negative Cm (-.003), and a very good drag profile (I use Profili). Someday I'll get around to plotting the profiles with the modified TE, which is flat-surfaced for the aft 25% of the chord. This makes it possible to machine a good, thin balsa TE. In fact, the bottom surface is flat right up to the 25% chord line, right under the spars. The spars are at that position on Neil's suggestion, which places them at the center of pressure, and thus eliminates torque moments around the spar. Clever.

The #3 prototype is under construction. Simplified, strenthened joiner system, solid keel fuselage, so no room for ballast or battery. The battery is split into 2 cells in each wing root ahead of the spar. If there's a lot of public outcry against having to solder up your own cell sets, we could make them available for a reasonably exhorbitant fee.

Concerning washout and tip stalls: as I mentioned, the Talus prototypes have no washout...flat bottomed all the way. Easy to build true. Yes, there must be SOME twist, but it required only about 1/8" up elevon for the first flights. This will be reduced as the CG gets tuned.

Swept wings are inherently stable in turns, so tip stalls should not be a problem. I had a battery failure on the fourth or fifth flight, and the Talus stayed locked in its turn, smooth as glass, right on around behind the hillside. All it did was bend the joiner rods and crack a tip fin. This stability makes the plane feel like you're flying in a grooved track: put it in a bank and it just stays there, no falloff, no pullout. Almost weird except that it's so nice. VERY different from anything I've yet flown.

Gotta get this next one up and running, so back to the instruction manual.

Ed
Apr 07, 2006, 12:26 AM
Suspended Account
It's definately an interesting project. I look forward to seeing either yours fly at WCSC or Gregs some time when we get together.
Apr 07, 2006, 12:29 AM
Registered User
EdSoars's Avatar
BTW, to respond to other issues: yes, I took down the Upslopesailplanes website. It gives me more time to build and fly!

The JIT with the power fuselage gave me the idea to make a power pod that would fit on top of the wing. With the CG at the TE in the center, the motor, battery and ESC fit perfectly into a slick little pod that doesn't change the balance at all. The receiver lead is the only electrical connection between pod and wing. A 9-5 folder on an AXI 221220 and a 3 cell LiPo battery should push the Talus uphill very nicely. The same combination on my 26 oz HighRise gives a near-vertical climb. Quiet, too!

As soon as I figure out how to post pics, I'll put some up. Or I'll email them to Greg Luck and let him do it, and retain my rep for ignorance and sloth.

The beautiful composite 3+ meter Taborca wing is in a different category of aerodyne entirely! There is actually no aerodynamic reason for a tapered swept wing, Neil tells me, since the lift distribution is completely different than for an unswept wing. The mysteries of fluid dynamics elude me: a digital watch in the next room is enough math exposure. I suspect the 3M wing's taper is a matter of controlling flutter.

ed


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