New thread so we don't hijack...

Why you feel that the SALex wing performance is superior to the Zone V2? Is this based on modeling or empirical observation?

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The Helios to me is fantastic and it is Zone or V2 is it not? The foils on the Concepts are great too don't know what they are, as you can see in windy turbulent they rock as well as in light conditions. Hope to get CX3 soon to see how she flies.

George,

Relatively so. It uses the Zone-V2 airfoils but not in the reference design. Planform/washout changes will affect handling. This will likely be most noticable in turning behavior or at the limits of the speed range, fast or slow. Of course differences in mass distribution in wings affect launch height and how snappy a plane feels in quick maneuvers when just horsing around. I think the only wing out there (that I know of anyway) that is using the reference design, or very close to it, is Tom's newest solid core wing.

The Helios was designed before I provided the Zone-V2 moldie reference design, if I'm recalling correctly. I had only put out the airfoils. I wanted to give others the chance to see what they could do.

In hindsight though, and no dig on the Helios or any other specific plane so don't take it that way, I should have put the reference design out along with the foils. I've seen many wing designs and I think the vast majority leave something on the table for performance or handling or both. I should have put the reference out as essentially a mark in the sand... Do better than this, or just use it instead. With nothing to compare against, some don't have the experience to know whether they have fully optimized a design for what they want, or whether more work should be done.

That's why when I put out Synergy I provided a reference design up front. Designers are free to ignore it of course! But it provides a comparison point that is already quite good.

Gerald

Like Tom, it would be nice to see polars for the entire wing. It sounds like the ship in question flies quite nicely, but saying it is better without at least some analytical data is a bit bold.

Beating Gerald's reference design is tough. I designed my wing before the reference was published. In the end, it is remarkably close to the reference w.r.t performance; I give up some on the high speed performance and like 0.25 points of overall L/D in tradeoff for some slightly better low speed handling. At the time I designed my wing I knew the target weight for what I could build was closer to 300g, driving me to higher wing areas (350 in^2, reference is 330 in^2 IIRC). Boosting the root chord size required some creativity at the tips to keep the foils properly aligned and avoid degradation of the turbulent air handling characteristics the ZV2 is well know for. Today I would probably tweak a few things, #1 would be to reduce the area at the tips slightly for a tad better launch and ranging performance. I can also build a lighter ship than when I started, such that the reference design makes a lot more sense; anything it gives up on low speed performance is quickly gained back by having a sub 260g ship.

Comparing wings not built to the same exacting standards and same target weights is a moot point IMO. It would not surprise me in the least if the SALex designers feel their latest ships outperform a stock ZV2 based ship, if that reference ship was an early, heavier build than their now beautiful 253g machines. The secret to a Zone v2 is to build it LIGHT.

One thing for sure planes are still making great progress of course do to all the builders out there. Gt is also a great help.

Sometimes manufacturers of sailplane models will specify that their design uses an "improved" or "modified" version of some well known airfoil. Sometimes the reason that they do that is not because their airfoil is better. In fact they might actually be using the original airfoil, but by specifying that it is "modified" or "improved" in some unspecified way they don't have to worry that their design will be copied or that someone will take careful measurements of the wing that they got from you and complain that the airfoil accuracy sucks. After all, the customer, or person wanting to copy your design doesn't know exactly what your design is. Oh, let's not forget the

At the worlds there were lots of Chinese copies of lots planes. As Roland said it still is not my plane.

Phil, polars were shown in the other thread. The SALex root foil is not the same as the Zone V2 root, although perhaps it was used as a starting point. I think everyone is just curious as to how and why this wing is better. Everyone always wants better, do they not?

That is very interesting George. I did not realize there were copies of things other than the Topsky available en-mass. It would be very hard to mimic Roland, even if the ship looked identical getting the craftsmanship to that level would be a feat, and very scary if a factory is doing it.

I don't know of any Chinese copies either even though I'm very active on the Chinese DLG scene...

Sam, that polar showed some questionable logic at the very least. Comparing at RE=200k and 100k are out of the range of DLG flying. The comparison at RE=60k is applicable to a root foil, but if you look at Cl=.3 to .5, which is applicable for DLGs in cruise, then you'll see that the comparison actually shows the ZV2 to be lower drag in this region.

Also notice that as the RE number decreases, the region of Cl that favors the ZV2 is rapidly increasing... indicating that if you did the comparison at typical DLG RE numbers, you'd probably see a completely different picture.

Again, also remember that we're looking only at a root section, not the wing in whole. Root performance is important but in a whole wing analysis, this is probably the section that affects performance the least. Lift distribution and the transition area of the wing typically make the "signature" of the flying characteristic.

I think it's likely from looking at these graphs that the ZV2 was used as a starting point and modified to achieve some sort of different compromise. Again, I'm just curious what that design goal was, and if they actually ever flew a ZV2 reference or just looked at it on XFLR.

Originally Posted by samc99us

The secret to a Zone v2 is to build it LIGHT.

Hi Sam (and Gerald),

This matches what we have felt here from flying Zone planes (e.g. FW5, XXlites) against other designs (e.g Salpeter) – but I'd like to hear you say why? Is it because the Zone airfoil design philosophy is tilted towards good L/D (low CL performance) and compromises on power factor (CL^3/CD^2 i.e. sink/climb rate, typically associated with high CL performance)?

I appreciate I might be able to find this discussed in the Zone design threads and (in lieu of trawling) would be happy for pointers into them, but some comment here would be nice.

thanks
Hugh

FW5 is zone v1 airfoils, XXlite is zone v2 but not the zone v2 flanform and I don't think it uses all the zone v2 foils but only some. I have an FW5 at 265 grams and it is VERY floaty with its higher than usual wing area (22.5 dm^2 or 350 in^2) flying against a friend’s Salpeter (and having flown it a little bit myself), the Salpeter performs well at higher wing loadings and requires higher weights in winds which makes launching hard in windy conditions but it signals lift EXTREMELY well, better than any other model I've flown or flown against. As per climb rate in thermals go, I believe that the differences between models are small and most of the differences reported of superior climb rates of certain models are due to them being easier to core lift accurately rather than "climb rate" which is actually the sink rate taken out of the vertical velocity of the air raising.
Turbulence is usually a question of high performance over a wider range of angle of attack rather than peak performance. Perhaps the zone V2 is “peakier” then what is comfortable for the typical European weather.

Hi Roydor

Sorry, I meant FW Flow (think that's V2?). My understanding is that XXlite uses Zone V2 but I think it starts at the root with the 40k foil (on account of its root chord being so small).

Your points are good ones - planes that can signal and turn well (yay Salpeter - a great design) are going to beat many other planes when the lift is small/the air is bumpy. I still would like to hear from Sam/Gerald/others on their thoughts, too...

Hugh

Planes designed like the Zone-V2 are designed to be able to start out high on launch and to be able to move around the sky well. The idea is that once one has lift, the game is mostly over anyway. Suppose someone else finds lift and one is in the wrong place? A plane which can move fast and flat has a greater chance of getting there. A plane that is light doesn't need a whole lot of lift and doesn't need the best power factor at float speeds. But, a wing which can take a lot of camber can recover the power factor*. A plane which can fly fast for its weight can go downwind to the lift, climb in it, and then come home. A plane which cannot, needs to be able to climb even better just to get back. If there is absolutely no lift to be had, or even worse, nothing but sink, then launching high is an advantage.

If one makes the right choices then the plane choice should only make a small difference in the possible results. This may occasionally be an important difference, but often it is not. Usually it is the pilot which matters and not the plane (within reason of course). But if one makes the wrong choice and is in the wrong air or in the wrong part of the field to hitch the winning ride that someone else found, then a plane which can bridge the gap in time and with enough altitude left just might save the day.

That's a bit of the idea behind designs such as the Zone-V2.

Now the reference design for the Zone-V2 moldie wing was made with particular attention to handling qualities. It is not a simple linear or near linear progression of airfoils; there is a little bit of complexity there.

The original Zone series, as is used in the FW5Flo, is not related to the Zone-V2 series except in name and some similarity in design goals. The XXLite uses the majority of the Zone-V2 series but not the whole series in a rather high aspect ratio wing. Going high aspect ratio like that certainly boosts launch height! But it also gives up performance across the board in other respects. Being light enough can make up for a lot of that though. But in general, it is different enough from the reference design and "normal" aspect ratios that one shouldn't use it as a benchmark for what a "normal" Zone-V2 wing should achieve. Changing aspect ratio a lot alters too many things.

Wings such as the Zone-V2 have some differences in characteristics compared to the majority of the wings out there. The range of useful camber is large. It is funny but some wing designs benefit from a large camber range but others do not. It is a bit hard to predict in advance how much camber one can really get away with in real life. In modeling, pretty much any design shows potential to use a fair bit of camber to improve min sink (boost power factor) but it is often not the case with a real wing.

Zone-V2 designs have a reputation for being able to profitably use a lot of camber at times. The flip side of this is that the pilot should be prepared to adjust the camber more frequently and over a greater range than is the case for most wings. So, there is a learning curve. Flying such as wing the way one would fly a plane such as the Sirius (just to pick an example) leaves a lot of potential performance on the table.

* The envilope of performance of a wing is worth considering. This is what it can do, provided it is always set at the optimal camber for the conditions. Comparing wings at, say, 4 degrees camber and calling that the float setting for each isn't really true even if that is what one might often do. Perhaps for matching conditions, one wing should really be at 5 degrees instead of 4. Now the analysis changes.

So, instead of fixed camber analysis, generate a curve of L/D or of power factor as a function of lift coefficient (or equivalently of airspeed) for the appropriate turbulence level (vaguely approximate by ncrit perhaps). But, use the optimal camber for each lift coefficient. One finds that the optimal camber is not a constant, but changes over this range. The resultant curve is an indication of the maximum performance achievable by the design provided the pilot could make the perfect choices all the time.

But let's back up to the fixed camber method of examining things, and go back in history to the original Zone design. When it came out, the usual planes of that era operated in float mode with something around 3.5 to 4 degrees of camber, depending on the design (referenced to speed mode). Now occasionally in perfect dead air conditions a little more camber was usable, but pretty much only then.

If one looked at the Zone design at that same camber, then one concludes it isn't as good as one might want at floating. But what one should notice is that the optimal speed for a Zone wing at that camber setting is a bit faster than for other wing designs of the time. So let's slow the wing down. How do we do that? Add more camber. Now the speeds match, but suddenly the Zone wing has a very good power factor so it floats nicely.

The peculiarities of the Zone wing design allowed it to use the extra camber easily, whereas other designs struggled more with the extra camber as they were optimal for even slower speeds where the piloting margin was lower, and in many cases the wings wouldn't do it in real life anyway. But the Zone would. So it could cover the other planes in cruise with a 4 degree "float" setting, cover the other planes in float with a 6 degree slower "float" setting, and run figurative rings around them in cruise or speed mode. So it had a wider usable speed range of good performance for the same wing loading.

Anyway that was with the version of wing design that I flew for a while but it is a bit different than the design used in the FW5. I've flown both and they do not fly the same at all. It is amazing the differences planform and washout pattern make in the behavior of a wing. I'm not dissing the FW5, just indicating that it shouldn't be taken as exactly representative of the reference Zone wing flight characteristics, any more than the Helios or the XXLite or some other Zone-V2 wings should be taken as exactly representative of the Zone-V2 moldie reference design flight characteristics. Do the Helios and the XXLite fly the same? The devil is in the details.

Gerald