LSA specs

wrote in
ups.com:

Actually, the CAFE numbers come out a little better than what Van
states as the performance figures for the RV-6. And the stall speeds
that Van posts are pretty much what J. Roncz predicts in his
spreadsheets, even though Van's are a bit better. But then again
Van's planes may be operating at a slightly higher CL than what Roncz
uses. Which leads me to believe that the spreadsheets are quite
accurate.

This is why I'm having a hard time believing that the Sonex aircraft
meet the LSA rules as written. Even at the lightest version of their
aircraft ( Jabiru 2200 power and flown solo and no fuel ) the plane
would have a hard time meeting the stall requirements of LSA which
require max gross wt. figures with a 51 mph stall speed.

And my intention is to fully understand the LSA rules, not "down" the
Sonex aircraft or the people behind it. I believe the Sonex and its
people to be top notch, as do many others, evidenced by how many are
flying and continue to be built. They are reasonally priced,
economical to operate and good "all around" performers for their
power. And from what I have seen, several of the other "popular"
LSA's would have a hard time meeting the LSA specs. as I see them
written.

Neal



Which part of my post that indicated the fuselage of the Sonex is a
lifting body confused you??? Steve Wittman is said to have won a bet or
two with the same issue on the Tailwind. I have not done it, but plug
the same numbers in for the Tailwind and see what pops out.

--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

"ET" wrote in message
...
wrote in
ups.com:

snip

Which part of my post that indicated the fuselage of the Sonex is a
lifting body confused you??? Steve Wittman is said to have won a bet or
two with the same issue on the Tailwind. I have not done it, but plug
the same numbers in for the Tailwind and see what pops out.

--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

Can you find a credible test of the Tailwind's stall speed on the web? I've
looked for one, but without success. The CAFE report in the "members"
section of the EAA site doesn't show the stall speed, although the text
discusses stall speed testing. I seem to remember that Tailwinds with the
stock pitot/static system have an inaccurate ASI at low speeds, showing much
lower airspeed than actual.

A buddy who owned a Tailwind described it as a fast airplane, but with
"mean" low speed characteristics.

I don't buy into the theory that Tailwinds or Soni (?) gain much lift from
the fuselage. The aspect ratio of a fuselage is too small to generate a lot
of lift.

KB

"Kyle Boatright" wrote in message
. ..

"ET" wrote in message
...
wrote in
ups.com:

snip

Which part of my post that indicated the fuselage of the Sonex is a
lifting body confused you??? Steve Wittman is said to have won a bet or
two with the same issue on the Tailwind. I have not done it, but plug
the same numbers in for the Tailwind and see what pops out.

--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

Can you find a credible test of the Tailwind's stall speed on the web?
I've
looked for one, but without success. The CAFE report in the "members"
section of the EAA site doesn't show the stall speed, although the text
discusses stall speed testing. I seem to remember that Tailwinds with the
stock pitot/static system have an inaccurate ASI at low speeds, showing
much
lower airspeed than actual.

A buddy who owned a Tailwind described it as a fast airplane, but with
"mean" low speed characteristics.

I don't buy into the theory that Tailwinds or Soni (?) gain much lift from
the fuselage. The aspect ratio of a fuselage is too small to generate a
lot
of lift.

KB





It is also possible that your friend's plane was poorly rigged.

Some years ago, I saw a BD-4 that a guy had purchased and was trying to
repair sufficiently to complete. The biggest problem was that the fusalage
had a substantial twist. There can also be problems with a very heavy pilot
in a very small airplane--Steve Wittman was only a little bigger than Ken
Rand.

Peter

"ET" wrote in message
...
wrote in
ups.com:

Actually, the CAFE numbers come out a little better than what Van
states as the performance figures for the RV-6. And the stall speeds
that Van posts are pretty much what J. Roncz predicts in his
spreadsheets, even though Van's are a bit better. But then again
Van's planes may be operating at a slightly higher CL than what Roncz
uses. Which leads me to believe that the spreadsheets are quite
accurate.

This is why I'm having a hard time believing that the Sonex aircraft
meet the LSA rules as written. Even at the lightest version of their
aircraft ( Jabiru 2200 power and flown solo and no fuel ) the plane
would have a hard time meeting the stall requirements of LSA which
require max gross wt. figures with a 51 mph stall speed.

And my intention is to fully understand the LSA rules, not "down" the
Sonex aircraft or the people behind it. I believe the Sonex and its
people to be top notch, as do many others, evidenced by how many are
flying and continue to be built. They are reasonally priced,
economical to operate and good "all around" performers for their
power. And from what I have seen, several of the other "popular"
LSA's would have a hard time meeting the LSA specs. as I see them
written.

Neal



Which part of my post that indicated the fuselage of the Sonex is a
lifting body confused you??? Steve Wittman is said to have won a bet or
two with the same issue on the Tailwind. I have not done it, but plug
the same numbers in for the Tailwind and see what pops out.

--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

Quite true. Lifting bodies can generate a lot of lift, and airfoils vary
wildly in their maximum coeficient. Also, there is nothing in the LSA
rules, or any others that I can think of, to require that an aircraft be
able to maintain level flight at stall speed--so drag coefficient is not a
factor.

Peter

No part confused me. I just have a hard time believing that a fuselage
can accomplish 50 percent of the lifting force of the total body. Yes
I know that some lift comes off of the fuselage on planes, especially
the tailwind as you suggest and the hyperbipe type of designs, but I
didn't think the Sonex fuselage shape was that much different than most
other 2 seat SBS types, including the RV-6. I'll take this into
consideration, though I'm still not convinced that the fuselage lift is
what puts the Sonex into the LSA category.

Neal

ET wrote:
wrote in
ups.com:

Actually, the CAFE numbers come out a little better than what Van
states as the performance figures for the RV-6. And the stall speeds
that Van posts are pretty much what J. Roncz predicts in his
spreadsheets, even though Van's are a bit better. But then again
Van's planes may be operating at a slightly higher CL than what Roncz
uses. Which leads me to believe that the spreadsheets are quite
accurate.

This is why I'm having a hard time believing that the Sonex aircraft
meet the LSA rules as written. Even at the lightest version of their
aircraft ( Jabiru 2200 power and flown solo and no fuel ) the plane
would have a hard time meeting the stall requirements of LSA which
require max gross wt. figures with a 51 mph stall speed.

And my intention is to fully understand the LSA rules, not "down" the
Sonex aircraft or the people behind it. I believe the Sonex and its
people to be top notch, as do many others, evidenced by how many are
flying and continue to be built. They are reasonally priced,
economical to operate and good "all around" performers for their
power. And from what I have seen, several of the other "popular"
LSA's would have a hard time meeting the LSA specs. as I see them
written.

Neal



Which part of my post that indicated the fuselage of the Sonex is a
lifting body confused you??? Steve Wittman is said to have won a bet or
two with the same issue on the Tailwind. I have not done it, but plug
the same numbers in for the Tailwind and see what pops out.

--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

wrote in
oups.com:

No part confused me. I just have a hard time believing that a
fuselage can accomplish 50 percent of the lifting force of the total
body. Yes I know that some lift comes off of the fuselage on planes,
especially the tailwind as you suggest and the hyperbipe type of
designs, but I didn't think the Sonex fuselage shape was that much
different than most other 2 seat SBS types, including the RV-6. I'll
take this into consideration, though I'm still not convinced that the
fuselage lift is what puts the Sonex into the LSA category.

Neal

ET wrote:
wrote in
ups.com:

Actually, the CAFE numbers come out a little better than what Van
states as the performance figures for the RV-6. And the stall
speeds that Van posts are pretty much what J. Roncz predicts in his
spreadsheets, even though Van's are a bit better. But then again
Van's planes may be operating at a slightly higher CL than what
Roncz uses. Which leads me to believe that the spreadsheets are
quite accurate.

This is why I'm having a hard time believing that the Sonex
aircraft meet the LSA rules as written. Even at the lightest
version of their aircraft ( Jabiru 2200 power and flown solo and no
fuel ) the plane would have a hard time meeting the stall
requirements of LSA which require max gross wt. figures with a 51
mph stall speed.

And my intention is to fully understand the LSA rules, not "down"
the Sonex aircraft or the people behind it. I believe the Sonex
and its people to be top notch, as do many others, evidenced by how
many are flying and continue to be built. They are reasonally
priced, economical to operate and good "all around" performers for
their power. And from what I have seen, several of the other
"popular" LSA's would have a hard time meeting the LSA specs. as I
see them written.

Neal



Which part of my post that indicated the fuselage of the Sonex is a
lifting body confused you??? Steve Wittman is said to have won a bet
or two with the same issue on the Tailwind. I have not done it, but
plug the same numbers in for the Tailwind and see what pops out.

--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

Hrm,

Well, where can I get a copy of this spreadsheet?... either you've got
the wrong dimensions, or the spreadsheet is flawed.

The Sonex stalls clean at 46mph, and those are real verified numbers (no
I cant point you to a cafe study or anything but all builders on the
list who have actually flown one have verified their numbers..)

Is the airfoil type taken into account??


--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

"ET" wrote in message
...
wrote in
oups.com:

snip

Well, where can I get a copy of this spreadsheet?... either you've got
the wrong dimensions, or the spreadsheet is flawed.

The Sonex stalls clean at 46mph, and those are real verified numbers (no
I cant point you to a cafe study or anything but all builders on the
list who have actually flown one have verified their numbers..)

Is the airfoil type taken into account??


--
-- ET :-)


The Sonex numbers are believable, but absolutely DO NOT trust performance
figures provided by builders. Pitot/Static systems are notoriously
inaccurate at low airspeeds and owner/builders are notoriously optimistic in
their performance reports. In addition, without very expensive and
sensitive test equipment, you're not going to get accurate figures. There
isn't a CAFE report on the Sonex, so unless Sonex Ltd. has invested the time
and money to conduct private tests, my guess is that accurate testing simply
hasn't been done.

KB

The Roncz spreadsheets were published in Sport Aviation from February
1990 thru January 1991 ( I believe ). The one I am referring to ran in
the March 1990 issue. I'm not at the house at the moment but I'll
check when I get home and verify.

Neal

ET wrote:
wrote in
oups.com:

No part confused me. I just have a hard time believing that a
fuselage can accomplish 50 percent of the lifting force of the total
body. Yes I know that some lift comes off of the fuselage on planes,
especially the tailwind as you suggest and the hyperbipe type of
designs, but I didn't think the Sonex fuselage shape was that much
different than most other 2 seat SBS types, including the RV-6. I'll
take this into consideration, though I'm still not convinced that the
fuselage lift is what puts the Sonex into the LSA category.

Neal

ET wrote:
wrote in
ups.com:

Actually, the CAFE numbers come out a little better than what Van
states as the performance figures for the RV-6. And the stall
speeds that Van posts are pretty much what J. Roncz predicts in his
spreadsheets, even though Van's are a bit better. But then again
Van's planes may be operating at a slightly higher CL than what
Roncz uses. Which leads me to believe that the spreadsheets are
quite accurate.

This is why I'm having a hard time believing that the Sonex
aircraft meet the LSA rules as written. Even at the lightest
version of their aircraft ( Jabiru 2200 power and flown solo and no
fuel ) the plane would have a hard time meeting the stall
requirements of LSA which require max gross wt. figures with a 51
mph stall speed.

And my intention is to fully understand the LSA rules, not "down"
the Sonex aircraft or the people behind it. I believe the Sonex
and its people to be top notch, as do many others, evidenced by how
many are flying and continue to be built. They are reasonally
priced, economical to operate and good "all around" performers for
their power. And from what I have seen, several of the other
"popular" LSA's would have a hard time meeting the LSA specs. as I
see them written.

Neal



Which part of my post that indicated the fuselage of the Sonex is a
lifting body confused you??? Steve Wittman is said to have won a bet
or two with the same issue on the Tailwind. I have not done it, but
plug the same numbers in for the Tailwind and see what pops out.

--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

Hrm,

Well, where can I get a copy of this spreadsheet?... either you've got
the wrong dimensions, or the spreadsheet is flawed.

The Sonex stalls clean at 46mph, and those are real verified numbers (no
I cant point you to a cafe study or anything but all builders on the
list who have actually flown one have verified their numbers..)

Is the airfoil type taken into account??


--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams