Diana-2 and overall performance discussion

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

If you just look at the overall results, yes. But if you look at the
dayly results, then the Dianas have outflown the other models only on
the one fast day. On the weak days they performed well, but not
unbeatable. Bottom line: Consistency wins, or in other words, don't
underestimate the pilot factor! If Stefano Ghiorzo wins a two week
contest in the Diana, then he probably had won in an ASG-29, too.

Cockpit size may be a factor in the USA, but in the rest of the world,
most people are still reasonably sized. So this isn't the killer factor.
The small cockpit will prevent clubs to buy it, but then, the Diana
isn't a club ship anyway.

However, for most pilots I know, money is a major factor. So they
consider the estimated resale value. For a ship from one of the major
German manufactorer, this is more or less a known factor. For the Diana,
it's not. Many pilots just don't want to take that risk.

If Stefano Ghiorzo wins a two week
contest in the Diana, then he probably had won in an ASG-29, too.

I do not agree. Stefano is leading by just 2.3% over # 2 Leigh Wells
in an ASG29. I'm sure that the Diana-2 advantage over the contest has
been much more than just 2.3%. If he had been flying an ASG29, I am
convinced he would not be leading as the ASG29 suffers much more than
2.3% against the Diana-2.

Cockpit size may be a factor in the USA, but in the rest of the world,
most people are still reasonably sized.

I agree on that. Americans are over sized and need to consider that
more than anyone else. However, the American market is small compared
to the rest of the world anyway. It would be interesting to study
physical fitness Vs. placing at a World soaring contest. I can not
remember grossly overweight pilots ever placing in the top 3. I think
there is a correlation and cause and effect there. Sorry but I think
true.

Reichman wrote is his book that fitness is a very important element of
success in competition soaring.

Hey! Are you implying that most American pilots are grossly
overweight? Oversized? Supersized? I have seen few such specimens. The
population as a whole, O.K. but glider pilots? You simply can't be fat
and fit into most gliders. I agree that fitness is an important
element but not just for competition flying. I exercise on a regular
basis and am wiped out after a hot day of rigging, flying, helping
others. etc. I couldn't imagine being out of shape and doing it.
Granted, I am 53 years of age. Now, back to my bacon double
cheeseburger and excellent American beer. "Honey, can you hand me the
remote? This damn LazyBoy is stuck again"

On Aug 6, 5:19*am, tommytoyz wrote:
*If Stefano Ghiorzo wins a two week

contest in the Diana, then he probably had won in an ASG-29, too.

I do not agree. Stefano is leading by just 2.3% over # 2 Leigh Wells
in an ASG29. I'm sure that the Diana-2 advantage over the contest has
been much more than just 2.3%. If he had been flying an ASG29, I am
convinced he would not be leading as the ASG29 suffers much more than
2.3% against the Diana-2.

Cockpit size may be a factor in the USA, but in the rest of the world,
most people are still reasonably sized.

I agree on that. Americans are over sized and need to consider that
more than anyone else. However, the American market is small compared
to the rest of the world anyway. It would be interesting to study
physical fitness Vs. placing at a World soaring contest. I can not
remember grossly overweight pilots ever placing in the top 3. I think
there is a correlation and cause and effect there. Sorry but I think
true.

Reichman wrote is his book that fitness is a very important element of
success in competition soaring.

I suggest you buy one and come out and kick our butts with the
overwhelming performance advantage.
But- don't crash it.
Perspective- I had a long exchange with Gerhard Waibel when he was
doing the ASW-28. I wanted a smaller wing with higher aspect ratio. He
went slightly the other way. His practical explanation was that he
wasn't designing the product only for me as a racer, but that it had
to work for many users and be usable in a club environment in order to
be a viable product.
It could also not compromise the level of safety established.
I have 2 gliders in my shop now where the pilots likely would have
been seriuosly injured if the gliders they flew did not have this
important attribute. This is not possible without some additional
structural weight.
It also must be repairable using techniques available in existing
repair shops. The JS1 guys paid a lot of attention to this important
point.
Owner needs to be confident he will be able to get parts and support.
Buying my next racing glider depends on being able to sell the one I
have now. I doubt there are more than a handful of folks that compete
that aren't in the same situation.
The Dianna 2 is a remarkable machine, but my personal evaluation was,
and is, that it does not measure up to other options in the areas
other than performance.
FWIW
UH

On Aug 6, 8:26*am, wrote:
On Aug 6, 5:19*am, tommytoyz wrote:



*If Stefano Ghiorzo wins a two week

contest in the Diana, then he probably had won in an ASG-29, too.

I do not agree. Stefano is leading by just 2.3% over # 2 Leigh Wells
in an ASG29. I'm sure that the Diana-2 advantage over the contest has
been much more than just 2.3%. If he had been flying an ASG29, I am
convinced he would not be leading as the ASG29 suffers much more than
2.3% against the Diana-2.

Cockpit size may be a factor in the USA, but in the rest of the world,
most people are still reasonably sized.

I agree on that. Americans are over sized and need to consider that
more than anyone else. However, the American market is small compared
to the rest of the world anyway. It would be interesting to study
physical fitness Vs. placing at a World soaring contest. I can not
remember grossly overweight pilots ever placing in the top 3. I think
there is a correlation and cause and effect there. Sorry but I think
true.

Reichman wrote is his book that fitness is a very important element of
success in competition soaring.

I suggest you buy one and come out and kick our butts with the
overwhelming performance advantage.
But- don't crash it.
Perspective- I had a long exchange with Gerhard Waibel when he was
doing the ASW-28. I wanted a smaller wing with higher aspect ratio. He
went slightly the other way. His practical explanation was that he
wasn't designing the product only for me as a racer, but that it had
to work for many users and be usable in a club environment in order to
be a viable product.
It could also not compromise the level of safety established.
I have 2 gliders in my shop now where the pilots likely would have
been seriuosly injured if the gliders they flew did not have this
important attribute. This is not possible without some additional
structural weight.
It also must be repairable using techniques available in existing
repair shops. The JS1 guys paid a lot of attention to this important
point.
Owner needs to be confident he will be able to get parts and support.
Buying my next racing glider depends on being able to sell the one I
have now. I doubt there are more than a handful of folks that compete
that aren't in the same situation.
The Dianna 2 is a remarkable machine, but my personal evaluation was,
and is, that it does not measure up to other options in the areas
other than performance.
FWIW
UH


Everything people have said, but I kind of suspect a large factor is
just very few people are interested in buying a new 15m glider. I
suspect other things are secondary behind that.

The action for new gliders is is in 18m. The incremental cost of say
an ASG-29 over an ASW-27 is likely to be payed back in resale value
even if the purchaser is not a die-hard contest pilot. And the ASG-29
and similar gliders lets people compete in 15m class if they want to.
So the only market for the Diana 2 are people wanting to spend $$$ for
a 15m only glider, willing to put up with the small cockpit with side
stick (I'm 5'9" and average build and spoiled by my ASH-26E, I just
have no interest of squeezing into a tight cockpit for long flights),
take ownership risks with a riskier resale value, much less experience
in the field with maintenance and support etc. I'm surprised they sell
as many as they have.


Darryl

Darryl Ramm wrote:
The action for new gliders is is in 18m.

I'm not so sure. Our club has a couple of 15/18m ships. You'd be
surprized how many leisure pilots fly them with the 15m wingtips as soon
as the weather is halfways reasonable.

On Aug 6, 10:59*am, John Smith wrote:
Darryl Ramm wrote:
The action for new gliders is is in 18m.

I'm not so sure. Our club has a couple of 15/18m ships. You'd be
surprized how many leisure pilots fly them with the 15m wingtips as soon
as the weather is halfways reasonable.

By "new action" I meant sales of new gliders. What configuration
people will fly in a 18m/15m configurable ship and whether they would
buy a 15m only ship, a 18m/15m configurable ship or even an 18m only
ship is a different question.

A 18m/15m ship has a configuration advantage over a 15m ship and
therefore likely another reason to purchase (e.g. an ASG-29 or
similar).

Darryl

On Aug 6, 12:28*am, John Smith wrote:
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

If you just look at the overall results, yes. But if you look at the
dayly results, then the Dianas have outflown the other models only on
the one fast day. On the weak days they performed well, but not
unbeatable. Bottom line: Consistency wins, or in other words, don't
underestimate the pilot factor! If Stefano Ghiorzo wins a two week
contest in the Diana, then he probably had won in an ASG-29, too.

Cockpit size may be a factor in the USA, but in the rest of the world,
most people are still reasonably sized. So this isn't the killer factor.
The small cockpit will prevent clubs to buy it, but then, the Diana
isn't a club ship anyway.

However, for most pilots I know, money is a major factor. So they
consider the estimated resale value. For a ship from one of the major
German manufactorer, this is more or less a known factor. For the Diana,
it's not. Many pilots just don't want to take that risk

So, John, how many "oversized" US glider pilots do you know, compared
to, let's say, "well-fed" British or German glider pilots? Since the
US is by far not the biggest market for gliders, and most current
production gliders have ample size cockpits, it would seem logical
that it isn't the size of US pilots that is driving cockpit size, but
that of rich and well fed Euros.

To get back to the subject, Moffat in his original "Winning"
suggested that if one was serious about winning glider races (in span
limited classes), one would build gliders scaled around the obvious
smaller pilot population - women. Seems he was right, as usual.

Kirk
Well fed but comfortable in his LS6

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

I agree US soaring pilots are above average in fitness. However,
having soared in Germany and US though, there is a difference in
average size according to my untrained eye. Nobody who has flown the
bird has said it is uncomfortable, even over long flights. However, I
think the points raised here about the Diana-2 are good ones. Thing is
though, as far as I know, none have crashed or been repaired to
evaluate for their crashworthiness or repairability VS. other models.

Though I do hear the wings can only be repaired in Poland as nobody is
trained to repair their special structure. For European buyers perhaps
not such a big deal. For US buyers a big pause. Then again, who
wouldn't properly insure their glider?

I hear a lot about the Diana-2 offering little protection to the pilot
in a crash. Maybe it's true, but maybe not. From what I read, the
cockpits of some existing German types can jackknife and then
straighten out in a flash in a crash, injuring or killing the pilot in
the process. But the cockpit still looks in good shape later. The mass
of the glider behind the cockpit is a major factor in this. The
lighter the better. Until we can examine a Diana-2 crash, or have
empirical data on the crashworthiness, it all seems speculation to me
and I don't think many take the inherent lightness into account, which
adds to safety due to lower mass behind your head.

The control surface play is certainly an issue. Someone should ask the
factory about that. Is it correctable or not? Was it down to BB or is
it fleet wide? Good discussion. I hope the Duckhawk is a similar
breakthrough in performance. That would be something!