Diana-2 and overall performance discussion

I find it amazing that there are not more pilots flying the Diana-2 at
the worlds, since it seems to be head and shoulders above anything
else in the 15M. I guess too many pilots do not like the side stick or
lack of manufacturer reputation. Maybe the Australia fiasco stopped
many. Or are there other negative factors?

Other than that, I can not think of any other reason to pass it up for
a competition. If it were a new unproven design I could understand,
but it's not new and has already won a boatload of competitions,
despite flying in so few numbers. They always seem to clean up no
matter the competition.

Or is it that people buy what everyone else buys kind of thing?

I also think that the ever increasing wingspan in the open class has
reached a point where more does not mean necessarily better. Granted
the EB29 is leading, but look at the daily score sheets and the
performances seem so close, it's just very marginal from one to the
other. I think new materials and new structural designs to save weight
will give better results in the future, judging by the Diana-2
approach in the 15M class. Less weight = less required wing area,
higher aspect ration of wing, etc...

Feel free to discuss, as I don' see many discussions on sailplane
performance these days. It used to be a hot topic.

On Aug 5, 5:12*pm, tommytoyz wrote:
I find it amazing that there are not more pilots flying the Diana-2 at
the worlds, since it seems to be head and shoulders above anything
else in the 15M. I guess too many pilots do not like the side stick or
lack of manufacturer reputation. Maybe the Australia fiasco stopped
many. Or are there other negative factors?

Other than that, I can not think of any other reason to pass it up for
a competition. If it were a new unproven design I could understand,
but it's not new and has already won a boatload of competitions,
despite flying in so few numbers. They always seem to clean up no
matter the competition.

Or is it that people buy what everyone else buys kind of thing?

I also think that the ever increasing wingspan in the open class has
reached a point where more does not mean necessarily better. Granted
the EB29 is leading, but look at the daily score sheets and the
performances seem so close, it's just very marginal from one to the
other. I think new materials and new structural designs to save weight
will give better results in the future, judging by the Diana-2
approach in the 15M class. Less weight = less required wing area,
higher aspect ration of wing, etc...

Feel free to discuss, as I don' see many discussions on sailplane
performance these days. It used to be a hot topic.

Some people do not fit.

It is a beautiful sailplane.

On Aug 5, 4:12*pm, tommytoyz wrote:
I find it amazing that there are not more pilots flying the Diana-2 at
the worlds, since it seems to be head and shoulders above anything
else in the 15M. I guess too many pilots do not like the side stick or
lack of manufacturer reputation. Maybe the Australia fiasco stopped
many. Or are there other negative factors?

Other than that, I can not think of any other reason to pass it up for
a competition. If it were a new unproven design I could understand,
but it's not new and has already won a boatload of competitions,
despite flying in so few numbers. They always seem to clean up no
matter the competition.

Or is it that people buy what everyone else buys kind of thing?

I also think that the ever increasing wingspan in the open class has
reached a point where more does not mean necessarily better. Granted
the EB29 is leading, but look at the daily score sheets and the
performances seem so close, it's just very marginal from one to the
other. I think new materials and new structural designs to save weight
will give better results in the future, judging by the Diana-2
approach in the 15M class. Less weight = less required wing area,
higher aspect ration of wing, etc...

Feel free to discuss, as I don' see many discussions on sailplane
performance these days. It used to be a hot topic.

Diana-1 appeared to me to be a 3/4 scale 20-metre ship. That included
the cockpit. If you're 3/4 the size of a typical adult, you will fit
it perfectly! (I have sat, or should I say, squeezed sideways, into
one). If the cockpit is similarly sized in the Diane-2, the number of
potential buyers will be significantly lower than for a ship with room
for the typical American/European.

Mike

On Aug 5, 4:12*pm, tommytoyz wrote:
I find it amazing that there are not more pilots flying the Diana-2 at
the worlds, since it seems to be head and shoulders above anything
else in the 15M. I guess too many pilots do not like the side stick or
lack of manufacturer reputation. Maybe the Australia fiasco stopped
many. Or are there other negative factors?

It is seldom that a contest pilot flying a modern ship says this of
another:

"The Italians came about 1,000’ over me, pair flying beautifully in
their Dianas. I have learned not to even try to follow them. The
Dianas have a huge performance advantage and just walk away from me.
" (John Cochrane, USA team blog).

However you have to get into it before you can fly it. I tried the
Diana (-1) for size and it was hoplessly too small for me. The -2
doesn't look to me to be any bigger.

Have to wonder how much performance it would lose it it had a decent
size cockpit.

Andy

On Aug 5, 4:12*pm, tommytoyz wrote:

I find it amazing that there are not more pilots flying the Diana-2 at
the worlds, since it seems to be head and shoulders above anything
else in the 15M...

Better than average? Sure, I'll buy that. Way better than average? I'd
want to see that quantified.

I guess too many pilots do not like the side stick...

That might be. So far I've sent out several kits for converting side-
stick sailplanes to center stick, and nobody has expressed any
interest whatsoever in going the other way.

or lack of manufacturer reputation.

There might be a little bit of that, too. The majority of competition
pilots count on resale value to step themselves up to the next hot
ship. They might be leery of buying the Next Hot Ship (tm) of the
decade only to find they're out of contention because they can't
unload it for enough to buy the Next Hot Ship of the next decade.

Maybe the Australia fiasco stopped many.

It might be, but I doubt it. I think that most serious competition
pilots are level-headed enough to let one round of he-said-she-said
slide.

Or are there other negative factors?

Well, it is a rather pricy ship...

I think new materials and new structural designs to save weight
will give better results in the future, judging by the Diana-2
approach in the 15M class. Less weight = less required wing area,
higher aspect ration of wing, etc...

That is certainly true. But also, less weight = less structural margin
for crashworthiness + less margin for ground handling loads = less
robust and more easily damaged glider (yes, even with high-tech
materials and processes). All of that stuff is great for cutting-edge
pure racing machines. But one of the things that makes soaring
competition work is that used racing machines get sold off to
recreational fliers, usually at prices very near their original cost,
and the proceeds go towards the Next Hot Ship.

When the cutting-edge ships get so finely optimized that they are more
damage-prone and offer little in the way of crash protection, they
will find less interest in the used market than more conventional
gliders. Less interest means lower resale value, and less money in the
hands of the original buyer for the Next Hot Ship. So, yeah, some
independently wealthy folks with high risk tolerance and good health
coverage stand to totally sweep the competition just by throwing money
at it, and some probably already are. But I don't look towards that as
any huge force in the future of soaring competition.

Thanks, Bob K.

I also sat in the Diana-1 and it fit me fine, I'm 5"10. I actually
like the side stick, though I haven't flown one. As to the structural
integrity of lighter frames - if it's lighter, it'll take less energy
to push/pull it and otherwise less force will be applied to it. Look
how robust model a/c are. They seem more crash worthy than the real
ones. So I don't readily accept that argument off hand. Lighter might
actually be stronger as it would also have less kinetic energy to move/
absorb and thus need less energy (and incur less structural stress) to
stop/move it. Of course I could be wrong on that, but I think there is
something to it.

I think there is an exponential factor here - the heavier the plane's
structure is, the stronger the wing has to be, making it heavier
still, etc...and true in reverse.

Imagine if a structure like Diana-2 were also made of prepegs? Would
it be lighter still by a significant amount? It already weighs less
than 200Kgs. I think there is a lot of improvement coming, mostly by
making the sailplanes lighter and increasing their aspect ratio for
the same wing span.

I would love to see an 18M Diana-3. Any news on something like that?

On Aug 5, 6:07*pm, tommytoyz wrote:

Interesting points, here's a few observations:

...if it's lighter, it'll take less energy to push/pull it and
otherwise less force will be applied to it.

This here is one of the big issues encountered when designing
crashworthiness into airplanes and small, lightweight cars. Since it
takes less energy to deccelerate the lightweight vehicle, it
decelerates more quickly in an impact. The trouble with that is that
the vehicle occupants also get decelerated more quickly, and so
experience greater forces in the impact.

Of course, what has worked well for small cars are active crash
protection systems such as airbags that help distribute the
deceleration forces more evenly over the more vulnerable parts of the
body. There has been some work done to develop similar systems for
small aircraft, but I think we're a long ways away from seeing them in
gliders.

Look how robust model a/c are. They seem more crash worthy than
the real ones.

That is certainly my observation as well, but unfortunately I don't
think that it tells us much about the problem of crashworthiness of
person-carrying vehicles. At issue is that many parts of the model are
perfectly happy to resist a hundred G of deceleration or more without
breaking, and those that aren't absorb a huge amount of energy while
they break. The result is a relatively simple repair job and resumed
flight.

With person-carrying vehicles, I think you are limited to about 40g if
you don't want to hurt the occupants badly, and about 60g if you don't
want to kill them outright. What's important to keep in mind (and is
too easy to forget) is that you do not care whether the aircraft gets
broken. Really. Crunch all you want, we'll make more. In fact, you do
want the airplane to break, and break in such a way as to absorb
energy in the crushing and tearing of structure. Absorbing energy
reduces the peak and overall deceleration applied to the occupants,
and it is the occupants you really want to save, not the aircraft.

That is one of the huge issues with crashworthiness and carbon
structures. Carbon has great strength and stiffness by almost any
metric. What it doesn't do very well is absorb energy. As you load it
up towards its breaking point, it stores some energy in elastic
deformation. But then when it reaches its ultimate stress, it breaks
quickly and is is subsequently not available to absorb any more
energy.

Steel structures, on the other hand, load up and then start to
crumple, all the while absorbing huge amounts of energy in the
propagation of plastic deformation. That's why I likes me my Volvos so
much.

Obviously, the lessons of Formula and Indy car chassis design show us
that it is possible and practical to design and build crashworthiness
into carbon structures. However, the lessons seem to be to use lots
and lots of carbon, and include as much crumple volume as practical
and also to add many frangible bits such as suspension mountings to
absorb energy as they tear away. Both of those are somewhat
impractical in sailplanes.

Also of note, many auto racing classes impose a minimum weight that
allows generous margins for crashworthiness structure. We don't have
that sort of thing in soaring contests, and there hasn't been much
call for it, but there may come a day when that changes.

The trend in European sailplane crashworthiness seems to have been to
supplement the primary cockpit structure with structural elements of
very limber fibers of aramid (such as Kevlar) or advanced
polyethylenes such as Spectra or Dyneema. After the carbon gives up
the ghost, these very stretchy fibers absorb a lot of energy as they
load up into their plastic range, stretch out, and tear free of the
resin matrix. The penalty for such a system seems to be unavoidable
extra weight.

I think there is an exponential factor here - the heavier the plane's
structure is, the stronger the wing has to be, making it heavier
still, etc...and true in reverse.

Yes, that is certainly the case, no argument there.

Imagine if a structure like Diana-2 were also made of prepegs? Would
it be lighter still by a significant amount?

It could be so, but I rather doubt it is worth the effort. It could
certainly make for a stronger structure. However, much of a
sailplane's structure is bounded by stiffness considerations, not
strength. And I think that prepregs offer only a relatively modest
improvement in stiffness and I think no particular improvement in
energy absorption.

Thanks, Bob K.
http://www.hpaircraft.com/hp-24

The trend in European sailplane crashworthiness seems to have been to
supplement the primary cockpit structure with structural elements of
very limber fibers of aramid (such as Kevlar) or advanced
polyethylenes such as Spectra or Dyneema. After the carbon gives up
the ghost, these very stretchy fibers absorb a lot of energy as they
load up into their plastic range, stretch out, and tear free of the
resin matrix. The penalty for such a system seems to be unavoidable
extra weight.


Thanks Bob. Good points.

I think new materials and new structural designs to save weight
will give better results in the future, judging by the Diana-2
approach in the 15M class. Less weight = less required wing area,
higher aspect ration of wing, etc...

I think the Australia fiasco coupled with the 'what everyone else
flies' factor have both worked against this fine ship, although the
sidestick and need for special trailer (male root-spar stubs are perm
attached to fuse; wings have the female recip joint) haven't one it
extra points with most though either. It certainly holds it's own on
the comp circuit though, especially considering numbers, so I'm sure
there are many others out there now looking closer at it though.

If someone loaned Jim Payne their Dianna 2 for a while I bet he could
make it more popular

The Duckhawk will be an even more extreme example of the lighter
materials=less wetted formula by utilizing prepreg carbon, making it
look basically like a 2/3 scale model of an open class ship but with
an extreme envelope(300lb empty/900lb gross, 200ktVNE & 165ktVA, 50+/
1 L/D, +11/-9g's, 2sec roll rate, 30/1 aspect etc...). Sure looking
forward to seeing more progress on that project, which seems to be
backburner'd by projects like Perlan, Goshawk, TwinHawk, etc, but in
the meantime the Dianna does appear to be the highest performing 15m
ship, although not the most popular -at first.

-Paul

the meantime the Dianna does appear to be the highest performing 15m
ship, although not the most popular -at first.

- Diana 2 is the highest performing 15m period. No other 15meter
glider won so much in such a short period of time. It also contributes
to the world greatest pilots flying it...You could contemplate why
commercially the project was such a disaster, but the facts speak for
themselves. It is worth reading how SH tired benefit outdated Ventus 2
platform in GP series by forcing wing loading limits benefiting
Ventuses... It sadly is dirty world we live in. To refresh the memory:

(Copy/paste from Diana website)

1st place -Sebastian Kawa 3rd FAI World Grand Prix, 2010
Santiago,Chile

3rd place - Sebastian Kawa Chilean National 2009 Santiago, Chile

2nd place-Lukasz Wojcik 15th European Gliding Championship, 2009
Nitra, Slovakia

1st place - Sebastian Kawa Pribina Cup, 2009 Nitra, Slovakia

2nd place - Lukasz Wojcik Pribina Cup, 2009 Nitra, Slovakia

1st place - Thomas Gostner 2009 15m Italian Nationals

2nd place - Stefano Ghiorzo 2009 15m Italian Nationals

1st place - Sebastian Kawa World Air Games 2009 Turin, Italy

1st place -Thomas Gostner Chilean National 2009 Santiago, Chile

2nd place- Janusz Centka 30th World Gliding Championship 2008
Lusse, Germany

1st place - Sebastian Kawa 2nd FAI World Grand Prix 2007 Omarama,
New Zealand

2nd place- Tomasz Krok 1st Polish 15m Class Championship 2007
Leszno, Poland

1stplace - Sebastian Kawa 1st Polish 15m Class Championship

1stplace - Janusz Centka 14th European Gliding Championship 2007
Issoudun, France

2ndplace- Karol Staryszak 14th European Gliding Championship 2007
Issoudun, France

1st place - Janusz Centka 29th World Gliding Championship 2006
Eskilstuna, Sweden

1st place - Janusz Centka 31st Open Class Polish Nationals 2006
Leszno, Poland

1st place - Sebastian Kawa 1st FAI World Grand Prix 2005
Saint-Aubain, France

2nd place - Janusz Centka 13th European Gliding Championship 2005
Rayskala, Finland

1st place - Janusz Centka 30th Open Class Polish Nationals.
2005 Leszno, Poland