A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Home Built
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Aero engineer for designing homebuilt aircraft.



 
 
Thread Tools Display Modes
  #11  
Old June 2nd 10, 04:57 AM posted to rec.aviation.homebuilt
Brian Whatcott
external usenet poster
 
Posts: 915
Default Aero engineer for designing homebuilt aircraft.

Peter Dohm wrote:
"cavelamb" wrote in message
news
brian whatcott wrote:
cmyr wrote:

I chose what I believe is the best of both worlds by going with a
Jodel design. Efficient and economical on low H.P.,no apparent vices,
and most of the designs are former production aircraft with years of
goverment oversight to weed out any problems.
John G.
Good move! I have flown various Jodel flavors and can confirm that they
fly well. They are well liked and without vice.
Though how that trademark cranked wing does it, I'm not sure...

Brian W


Low wing load, moderate power loading, and a lot of leading edge.
No secrets there.

Actually, I envy you that one, Brian.
I've never had the pleasure.
I've heard they are really sweet.


--

Richard Lamb


I, too, have always heard that they were well known for extremely docile
handling; and my very limited experience with models as a kid suggests that
the docile handling is a common trait of that geometry.

You could certainly do much worse, and I did once think of building a D9. I
might even consider one of their designs again--but the obvious problem is
that scratch building in wood is a lot of work and not a lot cheaper that a
prepunched metal kit from Vans!

Peter



For me the concern is the wooden structure. I know that spruce is not a
durable wood - it qualifies because it is among the highest strength to
weight materials. I continually marvel that an aluminum structure can be
left outside year after year and still hold up. I don't think you could
expect that performance of wood.

Brian W
  #12  
Old June 2nd 10, 02:48 PM posted to rec.aviation.homebuilt
Stealth Pilot[_2_]
external usenet poster
 
Posts: 846
Default Aero engineer for designing homebuilt aircraft.

On Tue, 01 Jun 2010 22:57:57 -0500, brian whatcott
wrote:

Peter Dohm wrote:
"cavelamb" wrote in message
news
brian whatcott wrote:
cmyr wrote:

I chose what I believe is the best of both worlds by going with a
Jodel design. Efficient and economical on low H.P.,no apparent vices,
and most of the designs are former production aircraft with years of
goverment oversight to weed out any problems.
John G.
Good move! I have flown various Jodel flavors and can confirm that they
fly well. They are well liked and without vice.
Though how that trademark cranked wing does it, I'm not sure...

Brian W

Low wing load, moderate power loading, and a lot of leading edge.
No secrets there.

Actually, I envy you that one, Brian.
I've never had the pleasure.
I've heard they are really sweet.


--

Richard Lamb


I, too, have always heard that they were well known for extremely docile
handling; and my very limited experience with models as a kid suggests that
the docile handling is a common trait of that geometry.

You could certainly do much worse, and I did once think of building a D9. I
might even consider one of their designs again--but the obvious problem is
that scratch building in wood is a lot of work and not a lot cheaper that a
prepunched metal kit from Vans!

Peter



For me the concern is the wooden structure. I know that spruce is not a
durable wood - it qualifies because it is among the highest strength to
weight materials. I continually marvel that an aluminum structure can be
left outside year after year and still hold up. I don't think you could
expect that performance of wood.

Brian W


you cant expect that performance in any material unless the surfaces
are passivated or coated to diminish any hydroscopic effect.

most of us have invented the hangar.

Stealth Pilot
  #13  
Old June 4th 10, 02:25 AM posted to rec.aviation.homebuilt
[email protected]
external usenet poster
 
Posts: 1,130
Default Aero engineer for designing homebuilt aircraft.

On Jun 1, 8:43 pm, "Peter Dohm" wrote:

I, too, have always heard that they were well known for extremely docile
handling; and my very limited experience with models as a kid suggests that
the docile handling is a common trait of that geometry.




I have a Jodel D-11 and don't consider it particularly
docile, certainly not like a Cub or Champ. It stalls at 40 mph but
long before you get that slow it will start a dangerous sink. Short
wings will do that. 1.3 Vso approaches are too slow. The gear, placed
as per plans, makes the tail really light and easy to nose the
airplane over. My mains are a bit further ahead but it's still light
in the tail and much twitchier in the rollout than many other light
taildraggers.

If you're using Falconar's plans, be aware that the airplane
might come out tail heavy. The original French plans called for
mahogany ply, no fabric on the fuselage or stab, and a tailskid. With
birch ply and fabric and a tailwheel, you'll be out the aft limit
unless you lengthen the engine mount or use a heavier engine. His
F11/12 spring gear is far heavier than the oleos, I think, and I wish
I had the oleos. More work but much more useful load in the end. Empty
weight numbers on the plans are way off.

I don't know why anyone would want flaps on this airplane. It
glides like a brick as it is, and if you want to drop faster just slip
it. It will scare the daylights out of you the first time. No other
airplane I've ever flown slips as aggressively. This one has the all-
flying rudder; the F-series fin and stab might not have such
authority. Flaps and their mechanism would just add more weight and
build time.

Keep that wood dry. If rot gets into the spar, the airplane
would be a writeoff. Building the spar is a major part of the whole
project. Get it straight and get those ribs glued on in perfect
alignment. If they're off, they're off permanently. There's no
adjustment once the glue sets. You need a really long shop, as the 27-
foot spar is all one assembly.

There are no tiedowns provided for. Mine has hand-holes in the
wingtips for maneuvering it on the ground and for tiedowns but they're
too far out and place stress on the tips in a strong wind. Better to
make up some aluminum bands to go around the spar and stick out
through the wing's bottom fabric three or four feet outboard of the
gear attachments.

Dan
  #15  
Old June 7th 10, 04:01 AM posted to rec.aviation.homebuilt
Peter Dohm
external usenet poster
 
Posts: 1,754
Default Aero engineer for designing homebuilt aircraft.


wrote in message
...
On Jun 1, 8:43 pm, "Peter Dohm" wrote:

I, too, have always heard that they were well known for extremely docile
handling; and my very limited experience with models as a kid suggests
that
the docile handling is a common trait of that geometry.




I have a Jodel D-11 and don't consider it particularly
docile, certainly not like a Cub or Champ. It stalls at 40 mph but
long before you get that slow it will start a dangerous sink. Short
wings will do that. 1.3 Vso approaches are too slow. The gear, placed
as per plans, makes the tail really light and easy to nose the
airplane over. My mains are a bit further ahead but it's still light
in the tail and much twitchier in the rollout than many other light
taildraggers.

If you're using Falconar's plans, be aware that the airplane
might come out tail heavy. The original French plans called for
mahogany ply, no fabric on the fuselage or stab, and a tailskid. With
birch ply and fabric and a tailwheel, you'll be out the aft limit
unless you lengthen the engine mount or use a heavier engine. His
F11/12 spring gear is far heavier than the oleos, I think, and I wish
I had the oleos. More work but much more useful load in the end. Empty
weight numbers on the plans are way off.

I don't know why anyone would want flaps on this airplane. It
glides like a brick as it is, and if you want to drop faster just slip
it. It will scare the daylights out of you the first time. No other
airplane I've ever flown slips as aggressively. This one has the all-
flying rudder; the F-series fin and stab might not have such
authority. Flaps and their mechanism would just add more weight and
build time.

Keep that wood dry. If rot gets into the spar, the airplane
would be a writeoff. Building the spar is a major part of the whole
project. Get it straight and get those ribs glued on in perfect
alignment. If they're off, they're off permanently. There's no
adjustment once the glue sets. You need a really long shop, as the 27-
foot spar is all one assembly.

There are no tiedowns provided for. Mine has hand-holes in the
wingtips for maneuvering it on the ground and for tiedowns but they're
too far out and place stress on the tips in a strong wind. Better to
make up some aluminum bands to go around the spar and stick out
through the wing's bottom fabric three or four feet outboard of the
gear attachments.

Dan


Well, I certainly stand enlightened on more than a few items, and that tie
down location does sound like a poor choice.

Personally, I have mixed feelings about the low speed performance that you
described--and feel that I have to ask about the glide ratio at the best
glide speed. Part of my reason for asking is that I personally liked the
Piper Tomahawk, despite its sordid reputation, and it had a good gilde ratio
at its best glide speed--but the version with four stall strips also had a
fast sink. I recall the characteristic, but not the flap postition involved
(possibly due to old timer's disease) and I never got to fly a Tomahawk with
two strips or with no strips--but IIRC, the manual implied that the high
sink might have been replaced with a dramatic stall, at a much lower speed,
on the version with no stall strips. My best recollection is that there was
a 6 knot difference in the stall speed without the strips--but the manual is
inaccessible if I still have it.

OTOH, the balance problems are "interesting" because, although I have yet to
build my own project, I have seen a few interesting issues crop up in kits
as well as plans built aircraft. The most glaring problem that I can recall
was a two seat tandem kit that resembled a high wing ultralight in
appearance, but was always intended to be a very simple registered airplane.
I'll alow the type and manufacturer to remain nameless, but the factory
welded fusalage had been jigged incorrectly when it was welded with the
result that the wind was too far forward and the aircraft was tail heavy--so
that forward pressure was required on the stick as there was no provision
for trim. The good news was that the design CG position was shown in the
plans relative to the wing--and just happened to be the same place as the
wing strut attachment points with provision for balancing points to be
easily attached. That last part really qualifies as an outstanding design
feature--especially in the homebuild arena--and we were easily able to
properly balance the airplane with about 15 pounds of balast added to the
nose. After that, it flew perfectly hands off. (I know that a purist would
criticise the estra weight, and I basically agree, but it made a lot more
sense to the owner/pilot than cutting and rewelding the factory welded
fusalage.) The point of this long winded dissertation is simply that you
never know until you do a full weight and balance, both with and without
people and fuel, and any amateur-built aircraft may very well require
adjustment.

Peter




  #16  
Old June 7th 10, 04:24 AM posted to rec.aviation.homebuilt
cavelamb[_2_]
external usenet poster
 
Posts: 257
Default Aero engineer for designing homebuilt aircraft.

Peter Dohm wrote:
wrote in message
...
On Jun 1, 8:43 pm, "Peter Dohm" wrote:

I, too, have always heard that they were well known for extremely docile
handling; and my very limited experience with models as a kid suggests
that
the docile handling is a common trait of that geometry.



I have a Jodel D-11 and don't consider it particularly
docile, certainly not like a Cub or Champ. It stalls at 40 mph but
long before you get that slow it will start a dangerous sink. Short
wings will do that. 1.3 Vso approaches are too slow. The gear, placed
as per plans, makes the tail really light and easy to nose the
airplane over. My mains are a bit further ahead but it's still light
in the tail and much twitchier in the rollout than many other light
taildraggers.

If you're using Falconar's plans, be aware that the airplane
might come out tail heavy. The original French plans called for
mahogany ply, no fabric on the fuselage or stab, and a tailskid. With
birch ply and fabric and a tailwheel, you'll be out the aft limit
unless you lengthen the engine mount or use a heavier engine. His
F11/12 spring gear is far heavier than the oleos, I think, and I wish
I had the oleos. More work but much more useful load in the end. Empty
weight numbers on the plans are way off.

I don't know why anyone would want flaps on this airplane. It
glides like a brick as it is, and if you want to drop faster just slip
it. It will scare the daylights out of you the first time. No other
airplane I've ever flown slips as aggressively. This one has the all-
flying rudder; the F-series fin and stab might not have such
authority. Flaps and their mechanism would just add more weight and
build time.

Keep that wood dry. If rot gets into the spar, the airplane
would be a writeoff. Building the spar is a major part of the whole
project. Get it straight and get those ribs glued on in perfect
alignment. If they're off, they're off permanently. There's no
adjustment once the glue sets. You need a really long shop, as the 27-
foot spar is all one assembly.

There are no tiedowns provided for. Mine has hand-holes in the
wingtips for maneuvering it on the ground and for tiedowns but they're
too far out and place stress on the tips in a strong wind. Better to
make up some aluminum bands to go around the spar and stick out
through the wing's bottom fabric three or four feet outboard of the
gear attachments.

Dan


Well, I certainly stand enlightened on more than a few items, and that tie
down location does sound like a poor choice.

Personally, I have mixed feelings about the low speed performance that you
described--and feel that I have to ask about the glide ratio at the best
glide speed. Part of my reason for asking is that I personally liked the
Piper Tomahawk, despite its sordid reputation, and it had a good gilde ratio
at its best glide speed--but the version with four stall strips also had a
fast sink. I recall the characteristic, but not the flap postition involved
(possibly due to old timer's disease) and I never got to fly a Tomahawk with
two strips or with no strips--but IIRC, the manual implied that the high
sink might have been replaced with a dramatic stall, at a much lower speed,
on the version with no stall strips. My best recollection is that there was
a 6 knot difference in the stall speed without the strips--but the manual is
inaccessible if I still have it.

OTOH, the balance problems are "interesting" because, although I have yet to
build my own project, I have seen a few interesting issues crop up in kits
as well as plans built aircraft. The most glaring problem that I can recall
was a two seat tandem kit that resembled a high wing ultralight in
appearance, but was always intended to be a very simple registered airplane.
I'll alow the type and manufacturer to remain nameless, but the factory
welded fusalage had been jigged incorrectly when it was welded with the
result that the wind was too far forward and the aircraft was tail heavy--so
that forward pressure was required on the stick as there was no provision
for trim. The good news was that the design CG position was shown in the
plans relative to the wing--and just happened to be the same place as the
wing strut attachment points with provision for balancing points to be
easily attached. That last part really qualifies as an outstanding design
feature--especially in the homebuild arena--and we were easily able to
properly balance the airplane with about 15 pounds of balast added to the
nose. After that, it flew perfectly hands off. (I know that a purist would
criticise the estra weight, and I basically agree, but it made a lot more
sense to the owner/pilot than cutting and rewelding the factory welded
fusalage.) The point of this long winded dissertation is simply that you
never know until you do a full weight and balance, both with and without
people and fuel, and any amateur-built aircraft may very well require
adjustment.

Peter






If the purists give you static about it, just name it
Static Stability Augmentation System, and paint it bright red!

Seriously, why would anyone complain about properly balancing
an airplane??? It's rather important!



--

Richard Lamb


  #17  
Old June 7th 10, 04:27 AM posted to rec.aviation.homebuilt
Peter Dohm
external usenet poster
 
Posts: 1,754
Default Aero engineer for designing homebuilt aircraft.


"cavelamb" wrote in message
...
Peter Dohm wrote:

-----------------snipped-----------------

OTOH, the balance problems are "interesting" because, although I have yet
to build my own project, I have seen a few interesting issues crop up in
kits as well as plans built aircraft. The most glaring problem that I
can recall was a two seat tandem kit that resembled a high wing
ultralight in appearance, but was always intended to be a very simple
registered airplane. I'll alow the type and manufacturer to remain
nameless, but the factory welded fusalage had been jigged incorrectly
when it was welded with the result that the wind was too far forward and
the aircraft was tail heavy--so that forward pressure was required on the
stick as there was no provision for trim. The good news was that the
design CG position was shown in the plans relative to the wing--and just
happened to be the same place as the wing strut attachment points with
provision for balancing points to be easily attached. That last part
really qualifies as an outstanding design feature--especially in the
homebuild arena--and we were easily able to properly balance the airplane
with about 15 pounds of balast added to the nose. After that, it flew
perfectly hands off. (I know that a purist would criticise the estra
weight, and I basically agree, but it made a lot more sense to the
owner/pilot than cutting and rewelding the factory welded fusalage.) The
point of this long winded dissertation is simply that you never know
until you do a full weight and balance, both with and without people and
fuel, and any amateur-built aircraft may very well require adjustment.

Peter


If the purists give you static about it, just name it
Static Stability Augmentation System, and paint it bright red!

Seriously, why would anyone complain about properly balancing
an airplane??? It's rather important!


Richard Lamb

I agree, and it all was several years ago; but I will definitely use your
nomenclatu Static Stabiliby Augmentation System.

That's really outstanding!

Peter




  #18  
Old June 7th 10, 03:58 PM posted to rec.aviation.homebuilt
Stealth Pilot[_2_]
external usenet poster
 
Posts: 846
Default Aero engineer for designing homebuilt aircraft.

On Sun, 6 Jun 2010 23:27:43 -0400, "Peter Dohm"
wrote:


"cavelamb" wrote in message
...
Peter Dohm wrote:

-----------------snipped-----------------

OTOH, the balance problems are "interesting" because, although I have yet
to build my own project, I have seen a few interesting issues crop up in
kits as well as plans built aircraft. The most glaring problem that I


Richard Lamb

I agree, and it all was several years ago; but I will definitely use your
nomenclatu Static Stabiliby Augmentation System.

That's really outstanding!

Peter




The Auster J1B isnt a kit aeroplane. down in the tail there is a
location where the fuselage tubes form a "V" shape.
on each side of this V shape is some 1/8" steel riveted in position to
make a box.
in the standard aircraft there is a 10lb triangular lead weight bolted
in front of this "V".
if you put a metal prop on the aircraft instead of a wooden prop there
is a couple of pounds of lead in a triangular wedge to go in the box.
if you add the exhaust muffler on to the straight stacks there is
another triangular lead piece to go in the box.
all told I think there can be 21lbs of lead in the tail.

in flight you notice nothing if the CG is in the right place.

I wouldnt feel embarassed about some lead ballast to get the cg
correct. the aircraft will be a lethal trap if you dont get the cg
right. your passengers wont even see the lead so why worry about it.
of course if you make a second aircraft the way is open for some
tweaking to remove the need.
Stealth Pilot
  #19  
Old June 7th 10, 09:56 PM posted to rec.aviation.homebuilt
Peter Dohm
external usenet poster
 
Posts: 1,754
Default Aero engineer for designing homebuilt aircraft.


"Stealth Pilot" wrote in message
...
On Sun, 6 Jun 2010 23:27:43 -0400, "Peter Dohm"
wrote:


"cavelamb" wrote in message
...
Peter Dohm wrote:

-----------------snipped-----------------

OTOH, the balance problems are "interesting" because, although I have
yet
to build my own project, I have seen a few interesting issues crop up
in
kits as well as plans built aircraft. The most glaring problem that I


Richard Lamb

I agree, and it all was several years ago; but I will definitely use your
nomenclatu Static Stabiliby Augmentation System.

That's really outstanding!

Peter




The Auster J1B isnt a kit aeroplane. down in the tail there is a
location where the fuselage tubes form a "V" shape.
on each side of this V shape is some 1/8" steel riveted in position to
make a box.
in the standard aircraft there is a 10lb triangular lead weight bolted
in front of this "V".
if you put a metal prop on the aircraft instead of a wooden prop there
is a couple of pounds of lead in a triangular wedge to go in the box.
if you add the exhaust muffler on to the straight stacks there is
another triangular lead piece to go in the box.
all told I think there can be 21lbs of lead in the tail.

in flight you notice nothing if the CG is in the right place.

I wouldnt feel embarassed about some lead ballast to get the cg
correct. the aircraft will be a lethal trap if you dont get the cg
right. your passengers wont even see the lead so why worry about it.
of course if you make a second aircraft the way is open for some
tweaking to remove the need.
Stealth Pilot


The truth is: I agree!

It's just that I have run into so many people over the years, who seem to
place so much enphasis on weight that they seem willing to add a pound of
drag to save two pounds of weight, and frequently have seemed willing to
make some other questionable trades in other areas as well, that I just felt
compelled to make a comment about it--even if a few minutes more thought
might have provided a little better phrasing.

Peter



  #20  
Old June 8th 10, 12:49 PM posted to rec.aviation.homebuilt
Stealth Pilot[_2_]
external usenet poster
 
Posts: 846
Default Aero engineer for designing homebuilt aircraft.

On Mon, 7 Jun 2010 16:56:32 -0400, "Peter Dohm"
wrote:


The Auster J1B isnt a kit aeroplane. down in the tail there is a
location where the fuselage tubes form a "V" shape.
on each side of this V shape is some 1/8" steel riveted in position to
make a box.
in the standard aircraft there is a 10lb triangular lead weight bolted
in front of this "V".
if you put a metal prop on the aircraft instead of a wooden prop there
is a couple of pounds of lead in a triangular wedge to go in the box.
if you add the exhaust muffler on to the straight stacks there is
another triangular lead piece to go in the box.
all told I think there can be 21lbs of lead in the tail.

in flight you notice nothing if the CG is in the right place.

I wouldnt feel embarassed about some lead ballast to get the cg
correct. the aircraft will be a lethal trap if you dont get the cg
right. your passengers wont even see the lead so why worry about it.
of course if you make a second aircraft the way is open for some
tweaking to remove the need.
Stealth Pilot


The truth is: I agree!

It's just that I have run into so many people over the years, who seem to
place so much enphasis on weight that they seem willing to add a pound of
drag to save two pounds of weight, and frequently have seemed willing to
make some other questionable trades in other areas as well, that I just felt
compelled to make a comment about it--even if a few minutes more thought
might have provided a little better phrasing.

Peter


I had a fellow pilot complete a rebuild of his aircraft after the 3rd
crash destroying it.
you think you'd write him off at 82 after the third prang :-)

"how'd the rebuild go mitch?"
"3 lb lighter overall than last time" he said with some excitement.

Mitch earned my undying respect that day.
the accidents are just part of an active flying pasttime in an
unforgiving environment but to have the focus on weight control at age
82 when the temptations must have been to 'make it a bit stronger'
showed me that he is focussed on what matters.

doesnt pay to become jaundiced in life. some people surprise you when
you least expect it. :-)

Stealth Pilot

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
DARPA calls for help in designing submersible aircraft Charles Vincent Home Built 20 October 14th 08 05:45 PM
How to License Your Homebuilt Aircraft [email protected] Home Built 0 January 26th 05 05:11 PM
aero-domains for homebuilt experts secura Home Built 0 June 26th 04 07:11 AM
I'm STILL trying to ID a homebuilt aircraft Phillip Rhodes Restoration 1 November 27th 03 07:59 AM
I'm still trying to ID a homebuilt aircraft Phillip Rhodes Home Built 1 November 26th 03 09:43 PM


All times are GMT +1. The time now is 10:39 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.