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Apr 01, 2006, 12:35 PM
Throw Caution to the Wind
Lavawing's Avatar
Thread OP

Talus: High Aspect, Constant Chord Swept Wing Revolution

Ed Berg of Upslope Sailplanes is at it again. Bringing something new and different to us.

Concept: A high aspect, constant chord swept wing glider. Fun and fast to fly. Aerobatic. Easy to build and fix. And tough enough for our proverbial Colorado landing zones. Plus it only takes two servos, and comes apart for easy portability.

Short History: There are other slope gliders with this basic configuration. There was a rage of them in parts of Europe in the 90's. Performance is supposed to be excellent. Those models were built up and/or fairly high concept Carbon/composite. Neil Pollack from Australia wrote an article in Quiet Flyer that got Ed thinking about the design. What Ed's trying to do is to get us a durable, quick-building EPP version.

Ed's calling his new design the Talus, named after the v-shaped tumble of rock that spills down a mountain slope. Ed's a geologist. (This name could prove somewhat linguistically challenging. Everyone I know in Colorado pronounces it so it rhymes with "palace", but all the dictionaries I've consulted say the proper pronunciation is actually like "Tailless", which, considering the design, is rather appropriate.)

Current Talus Design: 60" span. MH44 airfoil. Two 32.5" EPP panels with balsa trailing edge into which 60% elevons are cut. Spar system and joiner system are undergoing some changes. My proto-version has single non-tapered carbon tubes. Joiners are 1/8" steel rods in brass tubes and some ingenious bolt-through interlocking joiner blades. My version also has an attractive laser-cut plywood fuse with an EPP nose and a ballast tube.

Covering is important to the needed stiffness. Proto versions have been covered with carbon mat and 10 mil Mylar. I'm going to experiment with carbon mat on the underside and uni-directional carbon strips in an X on the top of the wing.

Tiplets are added for visibility, though they are supposed to be aerodynamically unnecessary.

Final design will probably have a redesigned spar system, thicker joiner rods, and modifications that allow the wing to safely separate on impact, er, landing. The fuse may be replaced with a "keel" and the gear embedded in the wing.

So... Do they fly?

Yes. Ed's first quickly-built version had carbon mat on the underside of the panels only. It proved to be too flexible and had flutter issues. He added some stiffness and has flown it successfully. Neil P. is also building prototypes and he reports that his version -- fully covered in carbon mat under the Mylar -- flies very well. Good speed. No flutter in dives. Good roll rate. Likes to be flown fast.

My own proto-version is being built now. Very interesting looking plane. Two panels and no tail to carry around or break appeals. But I have to admit I'm cautiously skeptical about the flight characteristics and what advantages it might have over conventional models. Doesn't look like anything I've ever seen in the air, so I really don't know what to expect.

I'll keep you posted. And I hope Ed and Neil chime in, especially as they've actually flown them, and they've been going on and on about airfoils and pitch moments and such -- things that just fly over my head. But I'll build it and I'll fly it. And get some photos of it in the air and some video. Maybe it WILL be a revolution...
Last edited by Lavawing; Apr 01, 2006 at 12:43 PM.
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Apr 01, 2006, 12:37 PM
auto-tune remix
slopemeno's Avatar
Is this similar to the "Just in Time"?
Apr 01, 2006, 12:57 PM
just add beer......
malachite's Avatar
I recently saw an X-Wing 60" fly and the ammount of speed maintained in light lift was pretty impressive. Though once the wind picked up to 20+ you tell it wasn't too happy about being out there. But that light lift performance translated into a landing that would rival a butterlfy. Pretty neat for a mouldie. I think distributes them?

Apr 01, 2006, 01:14 PM
Laughs at his own jokes.
IwantaJet's Avatar
Does it have a trailing edge spar? A piece of flat carbon there would help stiffen it up and keep the elevons straight. IMHO.

How about leaving the leading edge EPP and starting your carbon mat covering an inch or two back, going to the trailing edge? That could make for a stiff wing that still has some bounce where you need it. At least where I need it.

I saw Neil Pollack's article and wondered when folks would start playing with this design. Hope it works out well.

Apr 01, 2006, 01:15 PM
Registered User
wakumann's Avatar
Don't know high aspect ration and in EPP...

However here the real stuff:

Apr 01, 2006, 01:36 PM
Throw Caution to the Wind
Lavawing's Avatar
Thread OP

I'm not familiar with the Just in Time.


I've seen video of the X-wing 60 doing DS. Looks fun.


Trailing edge spar is done in an interesting fashion. I don't know if it's fully Ed's idea or not: The balsa TE is 2 inches wide. The elevons are cut out and are only 1.5 inches wide. Leaving half-an-inch of balsa as the subspar toward the tips, and full balsa toward the center. With the skin structure, this seems to be sufficient. (No guesses for DS yet. Interestingly, Neil speculates that DS may be one of the designs strengths, as the lift and weight are fairly evenly distributed over the span and bending forces are reduced.)

The carbon mat over EPP is supposed to retain some "bounce", though there may be a slow breakdown of the fibers over time. It's not full carbon cloth, but looks more like carbon cheese cloth.

wakumann: Thanks for the link. Interesting stuff. I've perused there. Very little video available, and what's there is less than inspiring. I wish there were more. I realize you aren't much for EPP. We're hoping that this model can be "real" as well as inexpensive and durable.
Apr 01, 2006, 01:56 PM
Registered User
wakumann's Avatar
Hi Lavawing
The carbon mat over EPP is supposed to retain some "bounce", though there may be a slow breakdown of the fibers over time
Don't know if this will work : stiff carbon over flexible EPP what's the point, why not using hd foam in the first place.

Anyway try this 2 links ( in german, but lots of construction pics).

Apr 01, 2006, 02:31 PM
ajroahkni's Avatar
Have you considered Chris Klique's fiberglass and 3m90 spray method as an alternative to the carbon mat? It could be what you're looking for. He sells a $25 video of his secrets, the glassing method included.

Apr 01, 2006, 02:51 PM
Registered User
miniphase's Avatar
looks great

more photos pls
Apr 01, 2006, 06:45 PM
DS Junkie
Screamin' Eagle's Avatar
Don't these types of designs require a lot of washout in the tips to prevent the spiral of death? The X-Wing reportedly has quite a bit of washout as well, which may contribute to the perceived difficulty penetrating in more windy conditions.

One of the locals at a nearby hill built something like this (with a mystery airfoil) that at 80", flew reasonably well and DSed even better, but let's just say that frontside top-end speed was not its forte'.
Apr 01, 2006, 06:53 PM
evan is gonna be pissed..LOL..

Again,, More photos!
Apr 01, 2006, 07:10 PM
Striving to Rip the Bring
raptor22's Avatar

These wings are great for all around flying, but as others have said, they usually need a decent amount of washout.

What I think is coolest is that with these very hig aspect ratio wings is that you can actually end up with flaps ahead of (or on) the CG, and combined with ailerons and combi-flaps, you can actually tune the lift distribution for various speeds. But the problem with that is that is requires more mixing power than most people are comfortable with.

Last edited by raptor22; Apr 01, 2006 at 07:16 PM.
Apr 02, 2006, 09:49 AM
Laughs at his own jokes.
IwantaJet's Avatar
Originally Posted by ajroahkni
Have you considered Chris Klique's fiberglass and 3m90 spray method as an alternative to the carbon mat? It could be what you're looking for. He sells a $25 video of his secrets, the glassing method included.


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

Apr 02, 2006, 10:57 AM
Needs brain lubrication
biber's Avatar
That's one really nice looking wing.
I'm glad to see, there is more than planks and zagis.

Don't get the idea of combining soft epp with stiff carbon fibres either, but anway...

Doooooooooooo eeeeeeeeeeeeeeeeeeeeeeet!

biber wondering why the wings' forum is located in the electric forums corner...

P.S.: Gotta stick that pic to this post, couldn't resist, thogh it ought to be top secret
Last edited by biber; Apr 02, 2006 at 12:37 PM.
Apr 02, 2006, 12:46 PM
Registered User
EdSoars's Avatar
That's a lot more response than I'd expected! To answer a few of the questions and observations about swept-wing designs in general, and the Talus in particular...

The aerodynamic advantage of the swept wing configuration over deltas or planks is that they have better L/D than either, have inherent spiral stability, and are easily built to be damage-resistant. My first prototype tracks very solidly ("like it's on rails"), will sit in a thermal turn hands-off for a LONG time, and is well, "groovy" in handling; not as quick and light-feeling as a combat delta, but still agile, with the best glide of any wing design I've tried so far. Not a floater, but long, fast and flat. Recovery from stall is very predictable and easy (this with a quite rearward CG). The first prototype was only covered with 10 mil mylar, which was heavy at the tips and not torsionally rigid enough, and fluttered before any dives could be done. The second proto, built by Neil, hasn't developed flutter in hundred-foot vertical dives, but hasn't flown in high wind or done any DS.

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.

The carbon fiber covering is not cloth; it isn't woven, it's like a very lightweight felt. Yes, it would be more rigid over high density EPS, but after
two rough mountainside landings the styrofoam would be a bag of crumbs. EPP is the only material I now have available that can recover from impact deformation. The mylar covering is much tougher than model films, and very inexpensive. It's clear, so trim colors are applied before ironing on the mylar, which has much stronger adhesive than model films, so doesn't need extra spray cement.

I'm still experimenting with different structures, coverings and adhesives. So far, the CF mat, painted onto the EPP foam with polycrylic varnish or thinned Goop, then covered with 5 or 10 mil mylar, seems to be the best solution to the need for ease of building, low cost, and torsional rigidity. Swept wings are inherently susceptible to flutter, and we just haven't had time to try different methods in different conditions. A laser-cut plywood fuselage works well to contain receiver, battery, and balance weight, but it isn't necessary. A plywood keel is all that is needed (to hold on to if a bungee launch is used) if the builder is willing to stuff a micro receiver into a wing panel and wire up a battery pack in two units of two cells, each in one wing panel. Less fuselage = less drag, and less to build and repair.

Because the CG of the Talus falls at the root TE, it's a good candidate for an electric power pod containing motor, folding pusher prop, battery and ESC so that the only connection to the pure sailplane setup is the wire to the receiver. I've wanted to build a Rocky Mountain Landing-capable electric sailplane with a pusher to keep the prop, spinner and motor out of impacts, but they always involved tricky dual-tailboom and tailplane configurations. The swept wing may be the way to go.

Thanks for your comments...keep them coming until we either have to abandon the Talus on the rubble of almost-good ideas, or have a viable kit to offer. If it looks like a go, it will be produced and sold by Laser Arts in Colorado Springs, who now put out my Spinner EPP DLG and HighRise electric designs.


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