Primary Glider Drawings

"Vaughn Simon" wrote in message
...

"Bill Daniels" bildan@comcast-dot-net wrote in message
. ..
Low L/D, taken in isolation, offers no benefit whatsoever in a trainer.
In fact, higher L/D is a safety feature that gets an inexperienced pilot
back to the runway after a bad judgement call.

I MOSTLY agree (see below) ...

In spite of this, there is an instinctive reaction among most glider
pilots to inversely relate L/D and safe handling qualities.

A high L/D implies a very slippery airframe. Unless any high L/D glider
trainer is very carefully engineered, a moment's inattention to any
nose-down attitude could quickly result in airspeeds beyond Vne.

Only a fool would try to learn flying in a "Primary".

I don't know that I go quite that far, but as I have said before, I
would not recommend a primary as a flight training aircraft. That said,
building one might be a great learning experience at the EAA chapter level
and flying it would be a great activity for the annual chapter picnic.

Vaughn

I actually have quite a bit of experience transitioning limited experience
pilots to high performance gliders. The most recent is a new partner in my
Nimbus whose only previous experience was in a 28:1 Blanik L-13. More often
it's a 2-33 pilot in a Duo Discus. My club trains ab-initio students in a
45:1 DG505.

Airspeed control difficulties in slippery gliders is often greatly
exaggerated.

Yes, they will have problems with airspeed control for a few minutes but not
extremely so. Mostly it's letting the airspeed oscillate in the 45 - 60
knot range while circling. They also tend to get a little fast on
approaches. Once they get a good handle on pitch attitude the problem goes
away. These "uber performance" gliders tend to have very effective
airbrakes with which to control excessive speed. Nothing dangerous here.

Letting airspeed increase unintentionally in a high L/D glider is no worse
than the inability to recover airspeed quickly in a low L'D glider.

"Ron Wanttaja" wrote in message
...
On Sun, 5 Oct 2008 09:18:21 -0600, "Bill Daniels" bildan@comcast-dot-net
wrote:

I would claim they are directly related. A glider carefully engineered
for
great handling and occupant protection will also have a good L/D.

Bill, I don't have a dog in this hunt, but: Unless you're using a
different
definition of "occupant protection" than I am, I disagree. Adding a steel
crash
cage to a glider cockpit will increase occupant protection, but has a
negative
effect on the aircraft weight without improving the aerodynamic
performance.

If your intent was more along the lines "occupant encapsulation" (e.g.,
enclosing the pilot to minimize aerodynamic drag), then we're in
agreement. but
it would be possible to put the pilot in an eggshell that would achieve
the
aerodynamics without significantly improving the crash protection....

Ron Wanttaja

I think steel tube structures are way overrated for "occupant protection" as
compared to carbon/Kevlar cockpits on modern composite gliders. Race car
builders abandoned steel tube "birdcages" for carbon/kevlar tubs a long time
ago for safety reasons. You'll never look at steel tube structure the same
way after you've seen a folded tube sever a leg artery.

For the most part, steel tube cages are limited to wing attachment/landing
gear structures in modern gliders.

Bill D

On Sun, 05 Oct 2008 16:32:12 GMT, "Vaughn Simon"
wrote:

A high L/D implies a very slippery airframe. Unless any high L/D glider
trainer is very carefully engineered, a moment's inattention to any nose-down
attitude could quickly result in airspeeds beyond Vne.

I wish that sentence was true........
Even an 58:1 ship at its maximum wing load requires significant
nose-down attitude to reach its Vne... unfortunately.

Only a fool would try to learn flying in a "Primary".

I don't know that I go quite that far, but as I have said before, I would not
recommend a primary as a flight training aircraft. That said, building one
might be a great learning experience at the EAA chapter level and flying it
would be a great activity for the annual chapter picnic.

Rather design and buil something that doesn't become boring after falf
a year....

Bye
Andreas

On Sun, 5 Oct 2008 13:33:05 -0600, "Bill Daniels" bildan@comcast-dot-net
wrote:


"Ron Wanttaja" wrote in message
...
On Sun, 5 Oct 2008 09:18:21 -0600, "Bill Daniels" bildan@comcast-dot-net
wrote:

I would claim they are directly related. A glider carefully engineered
for great handling and occupant protection will also have a good L/D.

Bill, I don't have a dog in this hunt, but: Unless you're using a
different definition of "occupant protection" than I am, I disagree.
Adding a steel crash cage to a glider cockpit will increase occupant
protection, but has a negative effect on the aircraft weight
without improving the aerodynamic performance.

I think steel tube structures are way overrated for "occupant protection" as
compared to carbon/Kevlar cockpits on modern composite gliders. Race car
builders abandoned steel tube "birdcages" for carbon/kevlar tubs a long time
ago for safety reasons. You'll never look at steel tube structure the same
way after you've seen a folded tube sever a leg artery.

You're missing my point, Bill. Whether steel tube or kevlar, occupant
protection does not contribute to L/D, as you seemed to claim. Wrapping an
eggshell around the pilot will give good aerodynamics, but better occupant
protection will weigh more and hence reduce performance.

Ron Wanttaja

Sure nice to have so many comments that are mostly relevant to thread
and beginners glider.

I was thinking about a wing that would support a decently high L/D and
a simple enclosure around pilot to reduce his flat plate drag, built
on a primary glider fuselage frame.

Build time 500 hours or less and transportable home. I'm in my high
80's and don't have 'time' left to build a 10 year project.

Would even consider adding a couple of chain saw engines for self
launch vs aero tow. To keep simple just use for launch and a retract
system with no restart in air. Simple and light weight.

Idea would be to keep very simple, cheap and light. Glider counter
part to LSA in GA.

Big John
************************************************** **


On Sat, 04 Oct 2008 13:35:29 -0500, Tech Support wrote:

On Sat, 4 Oct 2008 09:30:25 -0700 (PDT), "
wrote:

To All:

As promised, I've began posting drawings of primary glider(s). You
will find them in PRIMARY_GLIDERS Group, in the FILES archive, in the
Folder 'The Northrup Primary Glider.' So far I've only posted a few.
The others will be posted as time -- and my medical condition --
permits.

The drawings are in DeltaCAD's native format; the file suffix is .dc.
DeltaCAD will give you a free but time-crippled copy of their
software. It is about 6megabytes and will run on any WINDOWS system
from 95 on up. Most of the drawings are of fittings. The main
advantage in using a CAD format is that the drawings may be printed
full-scale, allowing them to be used as patterns.

I believe I have drawings for five different primaries but so far I've
only found the Northrup and the SG-38. These use a wooden fuselage.
Other primaries use welded steel tubing.

'Northrup' is a seed company. A member of the Northrup family
imported a primary glider after seeing them being flown in Europe
(circa 1929) and 'Northrup' became synonymous with 'primary glider.'
The drawings depict one of the earliest configurations of the primary
glider, in which the wings are wire-braced. Later versions have a
strut-braced wing.

NORTHROP refers to John Northrop, the American engineer best known for
his flying wings.

-R.S.Hoover
************************************************* *************************

Veeduber

What would it take to convert a primary into a basic soaring machine
(35+ to 1)?. I know sitting in open would be a high drag problem
but.......maybe a very light none structual wood frame cloth covered
to stream line fuselage?

Could a machine be made very cheap and quick this way to permit
soaring local around the air patch?

Also designed to pull (or fold) the wings in a few minutes (Solo) and
load to haul home for storage (and work/repair) in the garage?

To continue with a War Story.

I had a young Japanese man working for me in Japan. In discussion with
him he said he was in pilot training when war ended.

He said that the initial training was in primary gliders and that the
instructor stood on the welded steel tubing just behind the pilot in
training. The instructor wore the classical Japanese socks, like they
wore with 'zories', and gripped the tubing between the big toe and
first toe and held on to a vertical piece of the tubing.

Since the instructor couldn't reach the controls in front of pilot, he
gave voice instructions over the shoulder until he got off and let the
pilot go solo.

Launch was typical V of shock cord which two groups would hold and run
down the hill to extend. When they had stretched the shock cord
enough, the glider would be released and launched down the hill just a
few feet off the ground as sink rate and slope of hill was about the
same.

As was typical of Primary Glider flying, all the pilots had to help
launch and pull the gliders back up the hill.


Big John

"Ron Wanttaja" wrote in message
...
On Sun, 5 Oct 2008 13:33:05 -0600, "Bill Daniels" bildan@comcast-dot-net
wrote:


"Ron Wanttaja" wrote in message
...
On Sun, 5 Oct 2008 09:18:21 -0600, "Bill Daniels"
bildan@comcast-dot-net
wrote:

I would claim they are directly related. A glider carefully
engineered
for great handling and occupant protection will also have a good L/D.

Bill, I don't have a dog in this hunt, but: Unless you're using a
different definition of "occupant protection" than I am, I disagree.
Adding a steel crash cage to a glider cockpit will increase occupant
protection, but has a negative effect on the aircraft weight
without improving the aerodynamic performance.

I think steel tube structures are way overrated for "occupant protection"
as
compared to carbon/Kevlar cockpits on modern composite gliders. Race car
builders abandoned steel tube "birdcages" for carbon/kevlar tubs a long
time
ago for safety reasons. You'll never look at steel tube structure the
same
way after you've seen a folded tube sever a leg artery.

You're missing my point, Bill. Whether steel tube or kevlar, occupant
protection does not contribute to L/D, as you seemed to claim. Wrapping
an
eggshell around the pilot will give good aerodynamics, but better occupant
protection will weigh more and hence reduce performance.

Ron Wanttaja

Weight in a glider is a double edged sword and never simple. In fact, it
can add to L/D. For example, my Nimbus 2C has an L/D max of 47:1 at 1000
pounds and 49:1 at 1433 pounds. The difference in L/D max is due to a
higher Reynolds number at the higher best L/D airspeed with the higher
weight.

That extra weight is ballast water in wing tanks. In any but the weakest
weather, that ballast dramatically increases performance. This is shown
most clearly at 100 Kts where the 1000lb GW L/D is 22.3:1 and the 1433lb GW
L/D is 31:1. But, of course, structural weight is not jetisonable as is
water ballast.

But that wasn't really my point. It was that good engineering directed at
crashworthiness is an investment in design excellence which is also likely,
but not assuredly, to increase performance. At least the two aren't
mutually exclusive. That's particularly true when the cockpit structure is
molded carbon/Kevlar which can be of any shape and might as well be the best
aerodynamic one. As near as I can determine, the latest crashworthy
cockpits don't weight any more than the old ones and they are actually
lighter than steel tubes.

Bill D

"Bill Daniels" bildan@comcast-dot-net wrote in message
...

"Ron Wanttaja" wrote in message
...
On Sun, 5 Oct 2008 13:33:05 -0600, "Bill Daniels"
bildan@comcast-dot-net
wrote:


"Ron Wanttaja" wrote in message
...
On Sun, 5 Oct 2008 09:18:21 -0600, "Bill Daniels"
bildan@comcast-dot-net
wrote:

I would claim they are directly related. A glider carefully
engineered
for great handling and occupant protection will also have a good L/D.

Bill, I don't have a dog in this hunt, but: Unless you're using a
different definition of "occupant protection" than I am, I disagree.
Adding a steel crash cage to a glider cockpit will increase occupant
protection, but has a negative effect on the aircraft weight
without improving the aerodynamic performance.

I think steel tube structures are way overrated for "occupant
protection" as
compared to carbon/Kevlar cockpits on modern composite gliders. Race
car
builders abandoned steel tube "birdcages" for carbon/kevlar tubs a long
time
ago for safety reasons. You'll never look at steel tube structure the
same
way after you've seen a folded tube sever a leg artery.

You're missing my point, Bill. Whether steel tube or kevlar, occupant
protection does not contribute to L/D, as you seemed to claim. Wrapping
an
eggshell around the pilot will give good aerodynamics, but better
occupant
protection will weigh more and hence reduce performance.

Ron Wanttaja

Weight in a glider is a double edged sword and never simple. In fact, it
can add to L/D. For example, my Nimbus 2C has an L/D max of 47:1 at 1000
pounds and 49:1 at 1433 pounds. The difference in L/D max is due to a
higher Reynolds number at the higher best L/D airspeed with the higher
weight.

That extra weight is ballast water in wing tanks. In any but the weakest
weather, that ballast dramatically increases performance. This is shown
most clearly at 100 Kts where the 1000lb GW L/D is 22.3:1 and the 1433lb
GW L/D is 31:1. But, of course, structural weight is not jetisonable as
is water ballast.

But that wasn't really my point. It was that good engineering directed at
crashworthiness is an investment in design excellence which is also
likely, but not assuredly, to increase performance. At least the two
aren't mutually exclusive. That's particularly true when the cockpit
structure is molded carbon/Kevlar which can be of any shape and might as
well be the best aerodynamic one. As near as I can determine, the latest
crashworthy cockpits don't weight any more than the old ones and they are
actually lighter than steel tubes.

Bill D

I believe that you are correct in this, and that a kevlar capsule is a good
investment.

I have not researched the matter and could be wrong; but I strongly suspect
that a many, if not most, of the dissabling leg injuries in the old primary
gliders involved easily deflected collisions rather than "hitting a wall".

Peter

"Peter Dohm" wrote in message
news
"Bill Daniels" bildan@comcast-dot-net wrote in message
...

"Ron Wanttaja" wrote in message
...
On Sun, 5 Oct 2008 13:33:05 -0600, "Bill Daniels"
bildan@comcast-dot-net
wrote:


"Ron Wanttaja" wrote in message
...
On Sun, 5 Oct 2008 09:18:21 -0600, "Bill Daniels"
bildan@comcast-dot-net
wrote:

I would claim they are directly related. A glider carefully
engineered
for great handling and occupant protection will also have a good
L/D.

Bill, I don't have a dog in this hunt, but: Unless you're using a
different definition of "occupant protection" than I am, I disagree.
Adding a steel crash cage to a glider cockpit will increase occupant
protection, but has a negative effect on the aircraft weight
without improving the aerodynamic performance.

I think steel tube structures are way overrated for "occupant
protection" as
compared to carbon/Kevlar cockpits on modern composite gliders. Race
car
builders abandoned steel tube "birdcages" for carbon/kevlar tubs a long
time
ago for safety reasons. You'll never look at steel tube structure the
same
way after you've seen a folded tube sever a leg artery.

You're missing my point, Bill. Whether steel tube or kevlar, occupant
protection does not contribute to L/D, as you seemed to claim. Wrapping
an
eggshell around the pilot will give good aerodynamics, but better
occupant
protection will weigh more and hence reduce performance.

Ron Wanttaja

Weight in a glider is a double edged sword and never simple. In fact, it
can add to L/D. For example, my Nimbus 2C has an L/D max of 47:1 at 1000
pounds and 49:1 at 1433 pounds. The difference in L/D max is due to a
higher Reynolds number at the higher best L/D airspeed with the higher
weight.

That extra weight is ballast water in wing tanks. In any but the weakest
weather, that ballast dramatically increases performance. This is shown
most clearly at 100 Kts where the 1000lb GW L/D is 22.3:1 and the 1433lb
GW L/D is 31:1. But, of course, structural weight is not jetisonable as
is water ballast.

But that wasn't really my point. It was that good engineering directed
at crashworthiness is an investment in design excellence which is also
likely, but not assuredly, to increase performance. At least the two
aren't mutually exclusive. That's particularly true when the cockpit
structure is molded carbon/Kevlar which can be of any shape and might as
well be the best aerodynamic one. As near as I can determine, the latest
crashworthy cockpits don't weight any more than the old ones and they are
actually lighter than steel tubes.

Bill D

I believe that you are correct in this, and that a kevlar capsule is a
good investment.

I have not researched the matter and could be wrong; but I strongly
suspect that a many, if not most, of the dissabling leg injuries in the
old primary gliders involved easily deflected collisions rather than
"hitting a wall".

Peter
Most likely.

I know of one accident in a Schweizer 1-26A (tube and fabric) where an off
field landing resulted in a stick coming through the nose fabric severing a
leg artery. The pilot bled to death before he could get out of the cockpit.
I guess you can tell that I have no love of tube and fabric gliders.

Bill D

What great timing for this subject to come up!

On Saturday I attended a course "How to design an aircraft" given by
Bill Whitney who designed, or contributed to the design, of:
* The Whitney Boomerang (http://www.dwaviation.com/),
* The Australian Light Wing (http://www.lightwing.com.au/),
* The Seabird Seeker (http://www.seabirdaviation.com/),

....and about a dozen other aircraft. This was an exceptionally
interesting course and Bill had lots of stories to tell about aircraft
design. He has a very strong interest in crashworthiness and he
dedicates an entire chapter of his notes to this topic, along with
pictures and diagrams from the crash testing of the Boomerang. Given all
this it might be of interest to you to read his views on the subject.

In his notes he says: "Having been to many accident scenes, it is my
view that by far the best structure is the tubular steel fuselage
framework."

He continues: "Aircraft constructed of sheet metal also work reasonably
well provided there are some heavy extrusions going forward from the
pilot's seat to the firewall. In addition, fasteners with significant
tensile strength are required because heavily buckled panels place
significant prying loads on rivets tending to pop them out of their
holes. Thus use of 3/32"dia. or even 1/8" dia. rivets should be avoided
in the nose structure of the fuselage and 5/32" or even 3/16" rivets
should be used.

"In my experience, the poorest performers of all are composite
structures. Crashworthiness can be built into these structures but
almost never is. Building in crashworthiness can be achieved by building
in heavy floor-fuselage side angles or heavy hat sections into the
fuselage inner surface. These added sections will be exposed to
compression so they should be made of uni-directional fibreglass running
fore and aft with some diagonally laid laminates to transfer shear
loads. These sections will need to be reasonably thick noting that local
buckling or crippling is heavily dependent on thickness.

"Timber structures are also very poor performers."

(Whew! I hope this falls under "fair use"!)

Bill stressed the importance of designing a structure which would
"preserve the living space" in a crash. He mentioned the example of a
Jabiru crash where the aircraft failed to do this and fragmented into
small pieces.

Interesting stuff!


Bill Daniels wrote:
I think steel tube structures are way overrated for "occupant protection" as
compared to carbon/Kevlar cockpits on modern composite gliders. Race car
builders abandoned steel tube "birdcages" for carbon/kevlar tubs a long time
ago for safety reasons. You'll never look at steel tube structure the same
way after you've seen a folded tube sever a leg artery.

For the most part, steel tube cages are limited to wing attachment/landing
gear structures in modern gliders.

Bill D

Tech Support wrote:
Sure nice to have so many comments that are mostly relevant to thread
and beginners glider.

Hear hear!!!

I was thinking about a wing that would support a decently high L/D and
a simple enclosure around pilot to reduce his flat plate drag, built
on a primary glider fuselage frame.

Build time 500 hours or less and transportable home. I'm in my high
80's and don't have 'time' left to build a 10 year project.

What you're describing is the Compact 110 (defunct):

http://home.ptd.net/~jlbaker/compact110.htm

....or the ULF-1:

http://www.eel.de/english/ulf-1_description.htm