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aeroexperiments
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PostPosted: Fri Jul 08, 2011 5:26 am    Post subject: Wills Wing Sport 2 --high-speed performance? Reply with quote #1   
I was going to call this thread "Wills Wing Sport 2-- truth in marketing" as a bit of a "tongue in cheek" reference to Ryan's thread. But that's a little mean and I don't really have a beef with Wills Wing. But does anyone believe the Sport 2 is really quite so "hot" at higher airspeeds as is suggested by this polar curve: http://www.willswing.com/articles/Article.asp?reqArticleName=PolarData

The curve suggests that while penetrating strong headwinds or strong sink at high airspeeds, you'll get a glide that is just barely inferior to the U2, and quite a bit better than the old Ultrasport...

Yeah I know they gave a bunch of disclaimers in the article with the polar curves-- and the Sport 2 is a very sweet-thermalling glider-- but I'm a little skeptical about the right side of the curve as published-- but maybe I just have too much crap hanging out the wind....

Steve
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PostPosted: Fri Jul 08, 2011 6:01 am    Post subject: Reply with quote #2   
My personal feeling is the Sport 2 and U2 have a larger performance gap than shown. I don't have any numbers to compare, just experience in reaching point A from point B.

I also don't have any experience on a Ultra sport, or Super Sport to compare.

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PostPosted: Fri Jul 08, 2011 6:39 am    Post subject: Comparisons Reply with quote #3   
Ive owned an early U2 160 and found not much difference between it and a new 155 Sport 2. The U2 flew quite similar to my Talon, but was more difficult to land because of extended glide. I compare the Sport 2 175 as glorified Falcon 195.
Ultrasport a very good wing especially easy to thermal, but not in same class as any of the above.

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PostPosted: Fri Jul 08, 2011 6:55 am    Post subject: Reply with quote #4   
My progression went Falcon>Super Sport>Ultra Sport>U2>T2 (over the course of 13 yrs)

I would definitely say the Sport 2 feels like it goes noticeably better than a Super/Ultra Sport... but that's entirely subjective. Objectively, I can say the Sport 2 has the litestream control frame, which is a major improvement over round or older AT airfoils w/round base. The Sport 2 also has 1 sprog, so it only requires 1 luff line. I don't remember how many the SS or US have, but definitely more than one...

I can say objectively the Sport 2's VG provides longer throw of the cross-bars than the US (SS didn't have VG). Subjectively, the VG on the US didn't feel like it did much... I spent a lot of my time flying that glider at full VG...

As a side note- you or anyone else is always welcome to give me a good tongue-and-cheek ribbing.... I like to ruffle feathers from time to time, and fully expect that to be a 2-way street Wink

But I will say this: Those polars weren't made up, like those other guys

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PostPosted: Fri Jul 08, 2011 7:11 am    Post subject: Reply with quote #5   
AIRTHUG wrote:
The Sport 2 also has 1 sprog, so it only requires 1 luff line. I don't remember how many the SS or US have, but definitely more than one...

Ultrasport has two luff lines, but they both split halfway down from the kingpost, so there are four by the time you reach the sail. There's a lot of wire hanging out there.

Quote:
I spent a lot of my time flying that glider at full VG...

Since I'm flying that very glider now, I'll bear that in mind.

I've got a friend who weighs the same as me and has the same harness, who flies a Sport2 135, so maybe if we're on glide together at some point I'll be able to provide a comparison with my US147, but it's likely going to be no more helpful than, "yeah, his works better". (I have another friend the same size who flies a Sport2 155, but he has a racing harness and I suspect he'll be moving to a topless pretty soon, anyway.)

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PostPosted: Fri Jul 08, 2011 10:58 am    Post subject: Reply with quote #6   
I can only speak about the Sport 2 175 as that is what I owned and flew. Its high speed glide was very poor, which I liked, because it could suck that basetube in and dive it into our small LZ in Albuquerque much like a Falcon. It ain't close to a U2 when flown fast regardless of what that polar says (I owned an early U2 also).
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PostPosted: Fri Jul 08, 2011 11:28 am    Post subject: Reply with quote #7   
Of those mentioned I flew the Ultrasport 166, Sport2 135, Sport2 155, Sport2 175, Super Sport 163, and U2 160.

The S2 155 beats the US and does come close to the U2 performance at anything but a high speed dive.
I was really heavy on the 135 and my performance seemed like s***.
The S2 175 is a pig for regular sized people, so any benefits aren't worth considering unless you're big cuz otherwise it just sucks to fly.
The US and SS are outdated gliders and aren't better in any way.

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PostPosted: Fri Jul 08, 2011 11:55 am    Post subject: Reply with quote #8   
It's hard for me to compare when I have not flown the Fusion/U2 or Talon, but I think its close. I flew the Eagle back around '01 and thought it was a dog. I flew the Sport2 last month and think it is a great glider. The VG was noticable but not the speed I would want. And I have never flown with a speed indicator.

I'm probably the only one, but I think the Sport2 is a great first glider to own new if someone has progressed well with a rental Falcon. I think I would have purchased the Sport2 if it was around the time I purchased my first glider.

P.S.: I'm a Moyes fan.

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PostPosted: Fri Jul 08, 2011 5:52 pm    Post subject: Reply with quote #9   
I fly both a Falcon 1 225 and a Sport 2 175. My hook-in is around 230-235. At slower speeds the Sport has a nice glide. At faster speeds - not so. If I were a pilot who got really good on a Falcon and wanted a better glide but didn't want to go topless I'd get a U2 before I'd get a Sport 2. I expected a bit more performance over the Falcon than what I'm getting in the Sport. But, I'm not wired into the Sport 2 yet. When I do get really familiar with it I may have a more positive opinion of it. My only real disappointment with the Sport 2 175 is roll rate - not its glide (it is nice being able to get it into a smaller LZ). Right now I feel I have better control when flying the Falcon 1 225 - which flies pretty darn well for a big ship (it is in good shape with no sail flutter).
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PostPosted: Tue Jul 12, 2011 8:01 am    Post subject: Sport 2 Reply with quote #10   
Some interesting comments on this thread. Thanks for all the feedback , regardless of the source. Of course when folks come back and say "the Sport 2 135 flies like X and the Sport 2 155 flies like Y", etc, those comments are likely to be highly relative to their hook-in weights, whether they are speaking of handling or glide performance. One particular pilot is unlikely to be able to say that one size is better than another in any absolute sense, just in relation to his own hook-in weight. Although I have heard comments that the 135 is particularly nice. That's what I've been flying for the last few months.

In general, being heavy on a glider will "stretch out" the far right side of the polar and give better glide performance at high airspeed, unless the glider is being so overloaded that the wing is being seriously distorted.

Note that the Wills Wing polars referenced in the first post on this thread are supposed to be for 130% of the minimum hook-in weight for each glider listed. I still suspect that the polar given for the Sport 2 is a little optimistic in terms of the high-airspeed, far right side of the polar. But this is the area where "parasite" drag makes the most difference, and I know there are some things I could do to clean up my vario mount, etc....

My own perspective-- Sport 2 135, hook-in 155 pounds, very sweet handling while thermalling etc, good sink rate at low airspeeds, not such a good sink rate/ glide angle at higher airspeeds. A step down in this regard from the kingposted Laminar I was flying before. I suspect in some "penetration" situations I've been flying a bit faster than optimum, hence my interest in playing around with the polar curve....

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PostPosted: Tue Jul 12, 2011 8:10 am    Post subject: Re: Wills Wing Sport 2 --high-speed performance? Reply with quote #11   
aeroexperiments wrote:
But does anyone believe the Sport 2 is really quite so "hot" at higher airspeeds as is suggested by this polar curve: http://www.willswing.com/articles/Article.asp?reqArticleName=PolarData


On a related topic, that page has always pointed to an excellent tutorial which now seems to have gone away. You can see the text here at the archive, but does anyone have access to the full page with the pictures and can place it in a new home?
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PostPosted: Tue Jul 12, 2011 8:14 am    Post subject: Re: Wills Wing Sport 2 --high-speed performance? Reply with quote #12   
I was just looking at that last week. I'll try to find the link I was using.... Steve

Alan wrote:
aeroexperiments wrote:
But does anyone believe the Sport 2 is really quite so "hot" at higher airspeeds as is suggested by this polar curve: http://www.willswing.com/articles/Article.asp?reqArticleName=PolarData


On a related topic, that page has always pointed to an excellent tutorial which now seems to have gone away. You can see the text here at the archive, but does anyone have access to the full page with the pictures and can place it in a new home?
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PostPosted: Tue Jul 12, 2011 8:18 am    Post subject: Good tutorial Reply with quote #13   
Here ya go-- i just googled the whole first paragraph from your archival post-- it is a very good tutorial, for people who aren't familiar with how to find the best speed-to-fly for any combination of sink and headwind/ tailwind, off the glider polar.

http://www.5c1.net/Glider%20Performance%20Airspeeds.htm

PS here is another good link, similar content. Note that he is just dealing with the case where the "McCready ring setting" is zero-- i.e. we aren't dialing up the ring to a higher setting to represent the expected thermal lift out that we'll find out on course, to maximize our overall speed in cross-country racing. We are simply maximizing our glide angle for the present conditions.

http://people.consolidated.net/lhuffman/stf/STF.htm

Note also that this link specifically mentions the effect of density altitude on the polar and on the best speed-to-fly.

Of course, the latest competition varios do all this stuff, provided that an accurate polar has been entered. (My Brauniger IQ Comp doesn't compensate for the effect of density altitude on the polar curve.) But it's nice to be able to do it graphically ourselves (on the ground) to understand what is going on.

For example last week I took the curve given by Wills Wing for the Sport 2, pasted it on a larger sheet of graph paper so the origin of the graph was included on the sheet of paper, took a ruler and figured out the best speeds to fly for various combinations of headwind and sink. Then I made a little table of these numbers and pasted it on my base bar. Just to give a general check on whether the speed-to-fly indications provided by my vario seemed to be in the general ballpark, or not.

Steve
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PostPosted: Wed Jul 13, 2011 1:22 am    Post subject: Reply with quote #14   
Gary Hume did a review of the Sport 2 for British Skywings magazine. He said that "The Sport 2 looks far racier than it is". He also commented on the very cool looking A-frame corner brackets, the streamlined basebar etc.: "With a glider of this performance level a round basebar is more appropriate. It is hardly a high speed racer."

A friend of mine spoke to a European hang glider manufacturer a few years back and they talked about glide ratio and compared similar intermediate gliders from different manufactures.

He said there's no way you are gonna get a 12:1 glide ratio from a glider with a design like the Sport 2. 12:1 is what you get in real life glide tests on a topless glider.

I am not trying to put down Wills Wing. I am a huge fan of both the company and their gliders. But maybe there is some truth in that it has been overrated when it comes to performance when it just might be a true intermediate glider like all the others on the market.
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PostPosted: Wed Mar 20, 2013 2:15 am    Post subject: Reply with quote #15   
I personally watched a Super Sport 153 out glide and walk away from a Sport 2 155. The fellow on the SS weighed considerably more than the fellow on the S2. The SS has a higher aspect ratio wing and is full VG 100% of the time. I have flown both.
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PostPosted: Wed Mar 20, 2013 5:43 am    Post subject: Reply with quote #16   
I don't have a good reference for personal comparison, but I can tell a story that happened to me yesterday. I'm flying my Sport2 155. I hook in at 220. I fly a Lookout GT Pod harness (just like the Z5). My buddy is flying his U2 145 and he hooks in at around 180 I'd guess. He's got a racing harness. Anyway, the ridge is bangin and there's little thermals everywhere. It was unusually smooth air given the conditions and it was just a generally awesome day to be in the air. drool I was enjoying myself just flying around faster than I normally would. On the sport2 that means between 28 and 35 MPH airspeed (IAS). I had VG on full for the entire flight barring launch and landing. At this speed me and my buddy on the U2 were essentially even. There were times when I was able to fly right by him without altering our relative altitude because I had a slightly better lift line. mosh There were times when he was able to fly right by me. cuss

Then we spot a Bald Eagle flying by beneath us Cool. We both turn and give chase. The Eagle looks like it's just coasting along but when we try and catch it we learn that it's actually smoking us doing closer to 50. Shocked We both pull in to try and stay with the bird but by the time I hit 40+ MPH I start to plummet like a stone. ahh Within seconds I'm 300' below the U2 and I have to give up ever catching those two. He's pulling away both horizontally and vertically and there's nothing I can do about it. I hate that guy ROFL

So yeah, I'd say that my subjective experience confirms that the glide performance gap between the S2 and the U2 is fairly wide at higher speeds. The published polar shows the U2 with a sink rate of 400 fpm at 40 mph and the Sport2 at about 450 fpm at the same. I'd say I was losing 50' to him every few seconds, not in a minute. Of course you'd have to factor in our harnesses as well.

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PostPosted: Wed Mar 20, 2013 5:45 am    Post subject: Reply with quote #17   
In general, being heavy on a glider will "stretch out" the far right side of the polar and give better glide performance at high airspeed, unless the glider is being so overloaded that the wing is being seriously distorted.



I think the word "stretch out" is not correct. The polar shape is the same, it is just "shifted" down and to the right, when the pilot is heavy ( within the range). This mean you get more speed, but also more sink ( the L/D is the same) , and also the min sink gets bigger, and your stall speed also gets bigger. This also means that when you fly with a heavier weight, you have to watch your stall speed . I have seen pilots changing from a bigger glider to a smaller and because they are accustomed to certain position of the speed bar, get stalled and surprised.
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PostPosted: Wed Mar 20, 2013 8:24 am    Post subject: ploar changes with weight Reply with quote #18   
krassihg wrote:
In general, being heavy on a glider will "stretch out" the far right side of the polar and give better glide performance at high airspeed, unless the glider is being so overloaded that the wing is being seriously distorted.

I think the word "stretch out" is not correct. The polar shape is the same, it is just "shifted" down and to the right, when the pilot is heavy ( within the range). This mean you get more speed, but also more sink ( the L/D is the same) , and also the min sink gets bigger, and your stall speed also gets bigger. This also means that when you fly with a heavier weight, you have to watch your stall speed . I have seen pilots changing from a bigger glider to a smaller and because they are accustomed to certain position of the speed bar, get stalled and surprised.


A blast from the past! I'll be happy to respond.

If you had a graph of the polar (sink rate versus airspeed) in front of you, and you wanted to represent a change in weight of the pilot, it would NOT be correct to simply take a photocopy of the polar curve and paste it into position further to the right and lower.

Rather, you would take each individual point on the polar (say use 5 mile-per-hour increments for simplicity) and draw a line from the zero-zero point on the graph to that point on the polar, and then shift the point further down and right ALONG THAT LINE until you get to a point where the ratio of the new airspeed to the original airspeed equals the square root of the ratio of the new weight to the old weight, where "weight" includes wing, pilot, harness, and all the rest.

I once wrote a computer program to do this, that I'd like to get up and running again.

Each of the points on the original polar represents a specific angle-of-attack. Each of those points is shifted down and right without changing its L / D ratio, i.e. without changing its glide ratio, i.e. without changing the ratio of airspeed to sink rate. The higher-speed points get shifted further to the right than do the lower-speed points.

This is what I meant by "stretching out the right side of the polar". Of course the higher-speed points also get shifted further down than do the lower-speed points. I didn't mean that you grab hold of the polar as if it is printed on a sheet of rubber and stretch it only horizontally, not vertically. Still, it's not the same as simply re-drawing the original polar further down and right.

Simply shifting the whole polar down and right by an amount that correctly represents the change in airspeed at say min sink or best L/D, will greatly underestimate the extra performance (reduction in sink rate compared to the lighter pilot at the same airspeed) that the heavier pilot will see while flying at higher airspeeds.

Steve


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PostPosted: Wed Mar 20, 2013 8:40 am    Post subject: Reply with quote #19   
krassihg wrote:
In general, being heavy on a glider will "stretch out" the far right side of the polar and give better glide performance at high airspeed, unless the glider is being so overloaded that the wing is being seriously distorted.



I think the word "stretch out" is not correct. The polar shape is the same, it is just "shifted" down and to the right, when the pilot is heavy ( within the range). This mean you get more speed, but also more sink ( the L/D is the same) , and also the min sink gets bigger, and your stall speed also gets bigger. This also means that when you fly with a heavier weight, you have to watch your stall speed . I have seen pilots changing from a bigger glider to a smaller and because they are accustomed to certain position of the speed bar, get stalled and surprised.


See my post immediately above about each point on the polar corresponding to a given angle-of-attack. That also means a given bar position. Let's say for simplicity that we prefer to trim for min sink. Min sink occurs at the top of the polar and when we shift that data point down and right to represent a heavier pilot, that shifted point still represents the min sink angle-of-attack and the trim bar position. To a first approximation there is NO reason for a heavier pilot to not find the bar still to be at trim at min sink, if the bar was at trim at min sink for a lighter pilot. Just as a sailplane loaded with hundred pounds of water ballast still trims to min sink at the same trim lever setting that it had when it was empty. If the water is centered at the glider CG.

Changes in the relationship between trim bar position and trim angle-of-attack (and remember that stall is a function of angle-of-attack) have nothing to do with the shifting of the polar. Rather, they are a result of the following.

1) The wing washes out (distorts) at heavy loadings which unloads the tips and pitches the nose up. A heavier pilot therefore finds the wing tends to trim to a higher angle-of-attack than a lighter pilot, for the same hang point.

2) The hang point is rarely precisely at (or vertically in line with) the CG of the glider, at the trim angle-of-attack. If the hang point is slightly aft of the glider CG, this will make tend to make the wing trim to a higher angle-of-attack for a heavy pilot than a light pilot. This will exacerbate (make worse) the effect described in 1. If the hang point is slightly ahead of the glider CG, this will tend to make the wing trim to a lower angle-of-attack for a heavy pilot than a light pilot. This will lessen, and in extreme cases could even reverse, the effect described in 1.

Note that for a given glider, the hang point may be ahead of or behind the glider CG at trim, depending on where the pilot has put the hang point in the adjustable range, and even depending upon the glider pitch attitude and angle-of-attack that he is trimming for. (If the glider CG is higher or lower than the hang point, a change in the pitch attitude will move the hang point slightly forward or aft relative to the glider CG-- this effect is probably trivial, but does exist.)

Near the middle of the range of adjustable hang points I would expect effect #1 to dominate over effect #2, because I would expect the hang point to be quite near the hang glider C.G..

Also, the fact that heavy pilots typically need to hook in further forward than light pilots to trim for the same angle-of-attack, suggests EITHER that effect #1 usually dominates over effect #2, OR that the whole range of normal hook-in points is typically a little behind the hang glider C.G.. The latter possibility seems a little unlikely to me.

(Food for thought- why don't see more dramatic changes in trim with more dramatic changes in loading? If the glider trims at min sink for a 150-pound pilot, and trims to a significantly higher angle-of-attack for a 200-pound pilot at the same hang point, why doesn't it trim to a MUCH lower angle-of-attack when kiting during ground-handling with only 10 pounds of load on the hang strap? Or... maybe it does? Maybe the glider is kiting at the min sink angle-of-attack with the pilot exerting ZERO force on the bar or down tubes, whereas in flight the glider needs the weight of the pilot's hands and forearms resting on the bar-- not entirely trivial-- to keep the angle-of-attack down to min sink? Or is the change-in-washout effect negligible until we start to get really heavily loaded? Or does being in ground effect induce a trim change, so that we need to be cautious about comparing in-flight trim to ground-skimming trim or kiting-with-feet-on-the-ground trim? Perhaps more to the point, if ground speed is zero and the wind is strong and smooth enough to comfortably "kite" the wing with the hang strap somewhat loaded but the pilot's feet still bearing some weight, there is probably a large wind gradient, tending to unload the (close-to-the-ground) tips and pitch the nose up to a high angle-of-attack despite the light load on the hang strap... )

Note also that to the extent that effect #1 is taking place, our model of shifting the polar right and down as described in the post above is flawed. We really need to introduce more degradation of the sink rates at high airspeeds for the heavy pilot to show the unfortunate effect of the increased washout. But hopefully his performance at high airspeeds will still remain better than if we simply shift the whole polar down and right with no "stretching".

Steve
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PostPosted: Wed Mar 20, 2013 10:01 pm    Post subject: Reply with quote #20   
I should correct myself. You are quite right about "stretching" effect with wing loading
increase. But when we look at the polar curves of our gliders, the more obvious effect is the shifting, while the "stretching" is visible only when we look really close. I just took a look at some polar curves and the first thing I see is the shift. Then, if I really look closely, I can tell there is a "stretch". So,yes, you are right.

Now, how the higher wing loading is deforming the frame and therefore affecting the performance, that depends on the specific glider I guess. Some gliders are much stiffer than others.
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