Sailplane performance trends

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whiteglider

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Ah, and surprisingly that "unlucky female pilot" was you wasn't it? Welcome Hana.


For others, just know that virtually all reports about the DII have been (very) positive and people like Dick Johnson and Sebastian Kawa do have some authority to speak from.

This Hana had lots of problems and surprisingly, many of her observations were mutually exclusive and contradictionary. All this was strongly backed up... by exactly nobody, except some other users that in the end were the same Hana. Just one big gossip campaign, by what I guess is a bitter woman. If you search the internet you'll find her gossip campaign everywhere, but if you dig a little deeper, there's nobody backing anything up, just wonder why...
Well, I am not sure what makes you think that I am Hanna. First of all I don't personaly know Hanna at all. 2nd. Hanna's English seems to be very poor on her blog. She tries to explain what happened but I understand that she can not put it in to words. I am a glider pilot. I have seen Hanna's blog and pictures. Come on, you don't need to be an expert to understand that her glider and ancilleries were absolutely rubbish. I believe she was ripped off. Just my personal opinion you might not agree. There is one thing that I know; if you brought me the glider in the pictures free of charge I wouldn't fly it. I don't know what Kawa is saying about D-II. I heard that D-II airbrakes jammed on his approach in Chile but he landed safely. I haven't seen any report (D-II) by Kawa. Have you? But I have read his report about Jonker sailplane which was very good.
 

autoreply

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Well, I am not sure what makes you think that I am Hanna.
Apologies for that then. I've seen many (at least half a dozen) of fora where a new user came up with these accusations. At first sight they were well documented, but after digging a bit better they came back every time to a single person; Hana which usually became apparent after a couple posts. So hopefully you'll forgive me for that erroneous conclusion when a new users starts with posts about this, and only this subject :)
First of all I don't personaly know Hanna at all. 2nd. Hanna's English seems to be very poor on her blog. She tries to explain what happened but I understand that she can not put it in to words. I am a glider pilot. I have seen Hanna's blog and pictures. Come on, you don't need to be an expert to understand that her glider and ancilleries were absolutely rubbish. I believe she was ripped off. Just my personal opinion you might not agree. There is one thing that I know; if you brought me the glider in the pictures free of charge I wouldn't fly it. I don't know what Kawa is saying about D-II. I heard that D-II airbrakes jammed on his approach in Chile but he landed safely. I haven't seen any report (D-II) by Kawa. Have you? But I have read his report about Jonker sailplane which was very good.
I've seen, spoken to and heard quite a lot of positive reports about the Diana II by a lot of people who have most certainly earned their credits in the sailplane world. I've seen the ship myself and it's quality was magnificent.
Also, in some of the discussions with Hana it turned out that some things were very suspicious and were likely to be caused by erroneous handling or maintenance. I couldn't trace a single other pilot except for her that had similar comments in any possible way. The general consensus in the gliding crowd seems to be that this is a "hatred campaign" by someone who's obviously disappointed.
 

henryk

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Greg Cole's "dynamic soaring capable" Duckhawk will be groundbreaking for the soaring community.

-anybody know moore about that DUCKHAWK capability?
 

ultralajt

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Considering problems that Diana manufacturer had, it is possible that some of manufacturing and quality control was not as it should be on Diana #3 that came in hands of that frustrated woman, hence some restrictions were stated fot that sample regarding 100 hours of flying only and 200 hours between inspection in manufacturer workshop.

I believe that Diana is in general pretty well designed sailplane, but every perfect design can be made bad if workshop dont follow some standards in manufacturing and quality. That depend also on "health of the company".

My friend RC modeller wotking on an 1:3 RC scale Diana 2 sailplane for latest GPS competitions.
(GPS competition is copmpettiton of scale sailplanes, that must fly triangular course from a given height of 500m as much many times inside a given time window.
These sailplanes fly up to 120km/h average, but they must also exploit thermalls on the course)

I am wondering, how his Diana will perform on the competitions.

It has obviously some features, that will help her to fly well against competitors... specially her small cross section and wetted afuselage area in relation to other gliders. Only biplace gliders offer better relation between wing area and fuselage cross section and fuselage wetted area.

Mitja
 
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sachaknoop

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He here's a thought: In an other threat about designing a very small high performance glider autoreply states that scaling down is worsening the performance potential, now Mitja states here in a way, that scaling up does the opposite. So scaling up gives the best option for performance improvement. Nice, but then they tend to design their planes to take lots of useless ballast with them. I know, this is for competition, but wouldn't it be a party to have a LARGE glider for maybe 4 people with high performance figures? Or even bigger? like a passenger sailplane up to 12 people? That must be some silent glide! I admit I am not held back by any knowledge about gliders and what consequences thermaling such a big glider would have :) Just a thougt. Seems that they had things called Zeppelins that were sized up to more than 200 meters! Someone thought of that once!

Sacha
 

ultralajt

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Sacha, I am talking about radio control guided sailplane models for GPS competitions!
There, all models are of max 1:3 scale (5m wingspan or on open class 6-7m..., depending of an original glider span) and they compete against each other... not against real manned gliders.
So I was trying to tell that my friend opted to build scale Diana just for reason that Diana has very small fuselage comparing to other standard class gliders. And each lowering of parasite drag has benefit!
As fuselage is pretty large parasite drag producer, lowering its wetted area and lowering the max cross section, helps a lot in reducing awerall drag, thus rising lift/drag ratio.
As these RC models fly with very high average speeds, Diana front part fuselage, not bended down as at others gliders, goes trough air at fast flight with much less drag than let say ASW series of gliders...

Regarding other thread about flying wing, why one just dont make proper aerodynamic calculation of the performance and clear away that fog that cover all matter, making some members believe in some very optimistic goals about performances?


Sasha, size of real sailplane is somehow restricted with awerage thermals diameter, maneuverability and possibilities of outlandings on some fields away from airstrips.
Extreme large wing span is here a real problem.

Mitja
 

autoreply

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I believe that Diana is in general pretty well designed sailplane, but every perfect design can be made bad if workshop dont follow some standards in manufacturing and quality. That depend also on "health of the company".
You raise an interesting point and that might very well be the major problem. Most sailplanes are pretty similar constructed and except for canopies, they only differ on details. The Diana though is really different and an experienced workshop might have problems with it because of that. It's easy to see why many of her mentioned problems can be traced back to the unique concept. (Sparless wing, to name just one thing)
He here's a thought: In an other threat about designing a very small high performance glider autoreply states that scaling down is worsening the performance potential, now Mitja states here in a way, that scaling up does the opposite. So scaling up gives the best option for performance improvement.
Unfortunately, there's a weight limit that constrains performance. I've discussed the idea with several people, but with a span of around 40-50 meters and a single seat fuselage with an empty weight of 700 kg or so (and 700-1200 kg of possible ballast), you don't have to thermal anymore. Your performance then is so good that you can dolphin the whole flight even in the weaker weather conditions. There are "some" practical issues though. You need multiple wheels on your wing, you need a runway that's absolutely massive, not to mention that you need absurdly long wing sections. While normal sailplanes are "broken up" in wing portions that still fit in a road-legal trailer (8 meters approximately), for such a design the excessive weight of the many joints would be intolerable. Thus you have to have 12-15 meter long sections, so you can only transport it by ship or special transport.
Nice, but then they tend to design their planes to take lots of useless ballast with them. I know, this is for competition, but wouldn't it be a party to have a LARGE glider for maybe 4 people with high performance figures? Or even bigger? like a passenger sailplane up to 12 people? That must be some silent glide!
You take passengers along for a scenic flight or for transportation. Neither works very well in a glider. Yes, there is a market for "scenic flights", but worldwide that's maybe 10 or 15 sailplanes total. Virtually all operations of 2-seaters is instruction, or flying with a double-pilot crew, much like in an airliner, so there's simply no market for "bigger" sailplanes.

There's also the practical weight issue. MTOW according to CS22 is 750 kg. If you factor in the payload of 3 or 4 people and the required extra structure you're far over that limit. And you can't simply replace the weight of ballast by passengers. The ballast is in the wings and doesn't require any extra wing strength, because it's mass and the lift act at the same place. But if you put that extra weight in the fuselage, you do need to have a much stronger and heavier structure.

Even if you ignore the regulations, no winch can launch you safely and finding a plane, powerful enough to tow you might also be a challenge.
 
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@Mitja, do you know what sort of glide ratio a 1/3rd scale model gets compared to the original? I was always under the impression things got easier the smaller you make them and that model aircraft have amazing glide ratios compared to their full sized counterparts, you seem to be suggesting the opposite? Unfortunately I’m not an aerodynamicist and still learning as I go.

@Sacha the aim with competition gliders is to have as wide a range of wing loadings as possible, so big and heavy isn’t really good, you need big and light but able to carry loads of ballast. Ballast isn’t useless, it’s useful for obtaining the same glide angle at a higher airspeed resulting in higher average XC speeds on strong days. Landing open class gliders in anything other than a big airfield in rough conditions is not straightforward so there is a limit to how far you can go. It would be fun to see what’s possible though!
 

sachaknoop

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Hi Mitja Autoreply and detonation, It was just a free thougt out of the box, kind of. I understand the restrictions, commercial, structural, and others better now. I didn't realise the ballast is in the wings though, and I know it is not useles, but replacing ballast for people seemed like fun, even if I was just picturing it in my mind :)
Sacha
 

harrisonaero

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With DS we now talk about “gradient” rather than “lift”.

I can't help but think that if you could use satellites to predict the lift/sink/gradient bands in the jetstream then you could almost indefinitely dynamically soar a high performance UAV capable of withstanding the G-loads required to utilize the technique. In fact, you could have a whole fleet of these aircraft “talking” to each other about where the gradients are and a powerful computer program optimizing the flight profiles of each member. If a member “dropped out” of a gradient area it would be sent to land and along the way down be gathering data for its squadron mates.

The ultimate “solar powered” airplane using the earth itself as the solar panel.

The Duckhawk may be used as a UAV yet.

And if a DS soaring capable airplane called the Gradient™ appears on the market- you heard it here first :)
 

autoreply

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I can't help but think that if you could use satellites to predict the lift/sink/gradient bands in the jetstream then you could almost indefinitely dynamically soar a high performance UAV capable of withstanding the G-loads required to utilize the technique. In fact, you could have a whole fleet of these aircraft “talking” to each other about where the gradients are and a powerful computer program optimizing the flight profiles of each member. If a member “dropped out” of a gradient area it would be sent to land and along the way down be gathering data for its squadron mates.
Mapping wind (gradients) by radar has been tried for decades, mostly for gliding and for microbursts. Satellites are unlikely to be of much help there, the diffraction limit, even with a 1 km radar dish, you couldn't get more than about a kilometer of resoltion, even for jetstream measuring that's still too rough.
 
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