50+:1 15m sailplanes

Earlier, "Bill Daniels" wrote:

With carbon rods, you could probably build a 60 meter glider...

Now, let's hang on for a second while I use that as an excuse to
hijack this thread.

As strong as those pultruded rods and strips are, they offer only a
20% or so increase in stiffness (per weight or per volume) over wet
layups of dry carbon tape. For gliders, and especially for long-winged
gliders, the structural design is bounded by stiffness, not strength.
As such, pultruded carbon rods buy you only a relatively modest
premium over more conventional arrangements of carbon materials.

It's the stiffness, in both bending and in torsion, that keeps gliders
from fluttering themselves to pieces. It's also the stiffness that
keeps exterior finishes like gelcoat happy.

The reason I so dearly love those pultruded rods and strips is that
they represent an extremely effectively packaged solution for the
low-tech glider builder like me. I don't need any expensive autoclaves
or fiber alignment equipment or resin calibration/saturation stuff. I
just grab a bunch of pultruded strip off the spool and go with it.

As for 60-meter gliders (that's just under 197 feet for us
metrically-challenged folks), I happen to believe that they're
possible, but not very probable. But I see the limitations as being
more operational than meterological. There are few places to launch or
land one of them, let alone a contest full of them.

Personally, I think that 15 meter ships are close enough to the sweet
spot for all practical purposes. They fit easily in trailers, hangars,
fields, and launch grids. The pieces are relatively light. And 18
meters is only a wingtip-change away.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com

Jim wrote..
Maybe I'm missing something... but maybe not - didn't a Ventus win
open in SA recently (I could be mistaken).

I believe the Ventus won open the year we tried handicapping open class to
improve participation (US). We immediately dropped that idea because open was
in danger of losing again to another kiddy glider. I too believe that 18 meter
is about the best span for a single place ship. When 18 meter class came out, I
first thought that Standard class would slowly disappear, but they seem to be
as strong as any class. Will 15 meter slowly evolve into 18 meter? Just
thinking out loud, no need to tense up, all you 15 meter drivers. If it takes
as long to happen as 18 meter has, your 15 meter ships will all be 25 years old
and being flown by little old ladies from Placerville, anyway.
Cheers,
JJ Sinclair

I think the 18 meter class has been driven by motorglider considerations
much more than any natural "sweet spot" in performance/$. And frankly,
to even claim that 18 meters is the "sweet spot" is a subjective
judgment. Lot's of people prefer smaller gliders, and many prefer bigger

Since this is early January we can knock this one around a bit. The "sweet
spot" argument for 18 meters ignores all but weather and wingspan.


I don't think span is important. Instead it is aspect ratio. Any builder
can make span cheaply. A longer wingspan with larger mean
chord is useless and trivial. If all we wanted was span, this
would be VERY cheap.

Hmmm...it also strikes me that weight is very important to this discussion.
A 100# solo pilot is probably not getting the best performance for the
dollar from a DG-1000.

What I'd want is a minimum wing loading that, with me as the pilot,
supported a polar I like. What polar I like depends on the
conditions I fly in (floater or penetrator). I wouldn't want
to have to add ballast for every flight to get the polar I normally
like, since this would mean I paid for too much wing.

Having picked the wing loading, I'd now buy the highest aspect ratio
I could afford. As technology advances, this means I get more
and more span.

But technology for reducing weight seems to have outpaced
technology for increasing aspect ratio. So at the end of this
discussion, I'd like a Sparrowhawk for the dollar, instead of
something else. I'd prefer a much lighter glider with a
shorter wingspan and no ballast to a heavier one with more
span and the same aspect ratio.

I actually like LESS wing area with the same loading as my ideal
polar. Because the min sink part of the polar is 20 to 100 ft/min
less, the high speed part also gains this advantage. At the
super light weight, we can use a MUCH slicker airfoil and get the
same stall speed as a glider twice the weight. And we don't have
to beef up the fuse for heavy wings, then make the
wings larger for the weight, etc... (diminishing returns).

The tough decisions a is retract worth the extra weight? And is
the glider sturdy enough to be flown in/out of typical strips
at my skill level (bumps and ruts included)? The Sparrowhawk
is an excellent concept theoretically, but is it sturdy?
As a very lightweight pilot, I'd be very interested in a
similarly light glider, but I sure wouldn't want to BREAK it.
Tiny main and tailwheels, and a fragile tailboom, can be a
real practical drawback...

It sure is fun to browse all the exciting equipment at each extreme...

In article , Fantsu
writes

"Ian Strachan" wrote in message
...
No, but some of the German manufacturers proposed 16 m, which was so
close to the 15m flapped ships already being built (like the Pik 15)
that IGC decided to stick with 15m.

Just a bit of nit-picking, but it was Pik-20. Pik-15 "Hinu" is a towing
plane...

You are quite right, thanks for the correction. I meant the Pik 15
metre (or Pik 20).

On the motor glider front, I flew a Pik20E for some years in the UK.. I
always thought the span a bit short for our weak conditions when
carrying the extra weight of a self-launching engine. I wrote to Pik in
Finland suggesting an 18m version. They did in fact produce a 17m
version, the Pik 30E, but once DG produced the DG400 it was the DG that
sold rather than the Pik 30. I liked the Pik engineering, though, it
was nice and simple (as much as it can be with a self-launcher).

--
Ian Strachan
Lasham, UK

Does someby know a set of specs for the Diana 2 similar to those =
supplied for the American Duck Eagle ?

Snip

I don't think span is important. Instead it is aspect
ratio. Any builder
can make span cheaply.
Snip

Piloting skill makes up for a lot of span, aspect ratio
and weight.

Every salesman or designer will criticeze market competitors, so it's =
not strange for me that they beat the Diana as much as they can.

Regards,


--=20
Janusz Kesik

visit www.leszno.pl - home of the www.css-leszno.it.pl

The design shows some clever features, but I heard German designers =
having
some
doubts if the glider really would pass all JAR requirements.

(JJ Sinclair) wrote in message ...
JJ wrote..
I too believe that 18 meter is about the best span for a single place ship.

Yeah, certainly more convenient!

Jim

(Mark James Boyd) wrote in message news:3ffef018$1@darkstar...

Hmmm...it also strikes me that weight is very important to this discussion.
A 100# solo pilot is probably not getting the best performance for the
dollar from a DG-1000.

It's not the weight of the pilot, it's the weight of the plane that
counts. That's what ballast is for. Sure, you could build a 99/100th
scale DG-1000 just for the 100 lb pilot - but why? And it wouldn't be
cheap!

What I'd want is a minimum wing loading that, with me as the pilot,
supported a polar I like. What polar I like depends on the
conditions I fly in (floater or penetrator). I wouldn't want
to have to add ballast for every flight to get the polar I normally
like, since this would mean I paid for too much wing.

The problem with this approach is that you are tailoring your glider
to one specific condition - and give away the wonderful game of
tailoring a glider's wingloading to the actual condition you are
flying in. A floater in the spring is nice, but is no fun in the
middle of summer when 10 knotters roam the desert and you need an IFR
clearance to climb to cloudbase! BTW, that is probably a big part of
the PW-5 problem - too much of a one-trick pony...IMHO.


Having picked the wing loading, I'd now buy the highest aspect ratio
I could afford. As technology advances, this means I get more
and more span.

But technology for reducing weight seems to have outpaced
technology for increasing aspect ratio. So at the end of this
discussion, I'd like a Sparrowhawk for the dollar, instead of
something else. I'd prefer a much lighter glider with a
shorter wingspan and no ballast to a heavier one with more
span and the same aspect ratio.

I actually like LESS wing area with the same loading as my ideal
polar. Because the min sink part of the polar is 20 to 100 ft/min
less, the high speed part also gains this advantage. At the
super light weight, we can use a MUCH slicker airfoil and get the
same stall speed as a glider twice the weight. And we don't have
to beef up the fuse for heavy wings, then make the
wings larger for the weight, etc... (diminishing returns).

The tough decisions a is retract worth the extra weight? And is
the glider sturdy enough to be flown in/out of typical strips
at my skill level (bumps and ruts included)? The Sparrowhawk
is an excellent concept theoretically, but is it sturdy?
As a very lightweight pilot, I'd be very interested in a
similarly light glider, but I sure wouldn't want to BREAK it.
Tiny main and tailwheels, and a fragile tailboom, can be a
real practical drawback...

The whole Sparrowhawk thing scares me to death! When I'm bashing
around at 130 knots, I want my glider to have a certain structural
authority! Same thing when landing on some strange desert airstrip
for the first time. And don't get me started on the whole unregulated
ultralight glider thing!!! IMPORTANT SAFETY TIP FOR ANY NON-LICENCED
"PILOT" DROOLING OVER A SPARROWHAWK BROCHU Get the training, take
the damn test, get a licence, and fly a real glider, for goodness
sake! Or at least make me the beneficiary on you life insurance
policy...

As a very lightweight pilot, you have the advantage of an even greater
wingloading spread available to use, which can be a nice advantage
early in the season or late in the day - why give it away?

It sure is fun to browse all the exciting equipment at each extreme...

You're damn right about that! And congratulations on your CFIG, BTW!

Kirk
A not very lightweight pilot

Kirk Stant wrote:

The whole Sparrowhawk thing scares me to death! When I'm bashing
around at 130 knots, I want my glider to have a certain structural
authority!

Why do you think the SparrowHawk doesn't have "structural authority"?

Same thing when landing on some strange desert airstrip
for the first time.

Are you suggesting that the 15 meter LS-6 you fly would be easier to
land safely than the 11 meter SparrowHawk? Why would that be? Besides
being a lot smaller span (an asset when landing out, I think), the
SparrowHawk I flew landed slower than the 15 meter gliders I've flown.

And don't get me started on the whole unregulated
ultralight glider thing!!!
IMPORTANT SAFETY TIP FOR ANY NON-LICENCED
"PILOT" DROOLING OVER A SPARROWHAWK BROCHU Get the training, take
the damn test, get a licence,

Excellent advice, and echos what SparrowHawk people recommend.

and fly a real glider

I beg your pardon, but what isn't "real" about the SparrowHawk? From the
FAA registration database:

N-number : N40437
Aircraft Serial Number : 004
Aircraft Manufacturer : COLE GREGORY M
Model : SPARROW HAWK
Aircraft Year :
Owner Name : COLE GREGORY M
Owner Address : 2988 NE ROCKCHUCK DR
BEND, OR, 97701-6515
Type of Owner : Individual
Registration Date : 12-Jun-2003
Airworthiness Certificate Type : Not Specified


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Eric Greenwell
Washington State
USA