Today's Message Index:
----------------------
1. 05:59 AM - Re: Plane sitting: need list advice on elevator control horns (Barry Davis)
2. 06:02 AM - Re: Patches (TOM STINEMETZE)
3. 06:38 AM - Re: Re:up too late tonight-Patches (H RULE)
4. 06:42 AM - Plane sitting: need list advice on elevator control horns (Jeff Boatright)
5. 08:19 AM - Re: Plane sitting: need list advice on elevator control horns (Gary Boothe)
6. 08:54 AM - Alternate Airfoils Riblett 612 and 613.5 (Ryan Michals)
7. 09:22 AM - Re: Plane sitting: need list advice on elevator control horns (Catdesigns)
8. 09:31 AM - Patch design (BYD@att.net)
9. 11:13 AM - Alternate Airfoils Riblett 612 and 613.5 (Oscar Zuniga)
10. 11:21 AM - Plane sitting: need list advice on elevator control (Oscar Zuniga)
11. 03:54 PM - Re: Alternate Airfoils Riblett 612 and 613.5 (Ryan Michals)
12. 05:24 PM - Re: Patch design (Steve Eldredge)
13. 05:53 PM - Alternate Airfoils Riblett 612 and 613.5 (Oscar Zuniga)
14. 06:31 PM - Re: Patch design (amsafetyc@aol.com)
15. 07:16 PM - Re: Plane sitting: need list advice on elevator control (Jeff Boatright)
16. 07:41 PM - Re: Plane sitting: need list advice on elevator control (amsafetyc@aol.com)
Message 1
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Subject: | Re: Plane sitting: need list advice on elevator control |
horns
Plane sitting: need list advice on elevator control hornsJeff
The stretch in the cable might be an indication of additional trouble.
There could be damage to something else in the system and not just
isolated to the horn. Other damage could occur before the horn gave way
and relieved the stress. I know you did not want to hear this, but my $
.02 worth.
Barry
( still groggy from a late night at the Big Piet Factory)
----- Original Message -----
From: Jeff Boatright
To: pietenpol-list@matronics.com
Sent: Monday, December 29, 2008 4:11 PM
Subject: Pietenpol-List: Plane sitting: need list advice on elevator
control horns
Dear Pieters,
Today my instructor and I managed to damage the Piet while still in
its chocks; we bent the upper horn of the left elevator bell crank. I
need your advice on repairs.
How it happened: I was sitting in the cockpit. The tail was resting on
a sawhorse. The instructor removed the sawhorse to lower the tail. The
sawhorse wasn't placed far enough away and it caught the lower elevator
cable. The tail was lowered all the way to ground without this being
noticed. The upper horn bent over about 45 degrees towards the
centerline (towards the rudder). We bent the horn back, and of course
the horn now looks like an hourglass when viewed from fore or aft.
Oddly, the lower cable has a little more slack than before; definitely
more than the lower elevator cable on the other side. There does not
appear to be any damage at all to the large, bell crank in the fuselage
(behind the pilot's seat) at the other end of the cable.
Note that the bell crank appears to be built to plans.
The concerns:
1. Why is the cable slack even when the horn was bent back to
vertical? I guess the cable could have stretched, but this is an eighth
inch cable and I weigh 180. Doesn't seem like there would be that much
tension.
2. Removing and replacing the bell crank will take a lot of effort and
I want to go flying. Now. Could stiffeners be riveted to the horn
instead? How much strength has been lost due to the bend-unbend cycle,
and how much strength is needed here?
3. If it must be removed and replaced/rebuilt, what procedure would
require the least number of steps to accomplish this, with minimal
further damage?
Thanks for any advice on this. I am seriously bummed as I planned to
fly all this week!
Jeff
Message 2
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>>I doubt we could do justice to the creator and the creation if we didn't
show the past with an eye to the future.The sky's >>the limit, the heavens
are the limit, space is the limit... space to our knowledge is limitless
>>John
I agree. Let's get this SpaceShip0.1 patch off the ground.
Stinemetze
Message 3
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Subject: | Re: re:up too late tonight-Patches |
I have an 80 hp Franklin and with the front seat covered I can get her up t
o 90 mph on the straight away.That's almost X15 speed to a GN-1 isn't it!
=0A=0A=0A=0A=0A________________________________=0AFrom: Gary Boothe <gbooth
e5@comcast.net>=0ATo: pietenpol-list@matronics.com=0ASent: Monday, December
29, 2008 8:01:04 PM=0ASubject: RE: Pietenpol-List: re:up too late tonight-
Patches=0A=0A=0AYeah=85if they have a Corvair up front!=0A-=0AGary Boothe
=0ACool, Ca.=0APietenpol=0AWW Corvair Conversion=0ATail done, working on fu
selage (endless metal parts!)=0A(12 ribs down=85)=0ADo not Archive=0A=0A___
_____________________________=0A=0AFrom:owner-pietenpol-list-server@matroni
cs.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of H RU
LE=0ASent: Monday, December 29, 2008 4:01 PM=0ATo: pietenpol-list@matronics
.com=0ASubject: Re: Pietenpol-List: re:up too late tonight-Patches=0A-=0A
Grega GN-1 Aircamper ;please.Calling us a Pietenpol Aircamper is like calli
ng an F16 an F18.GN-1 Aircampers are more like X15's;able to reach the edge
of space and all that stuff.Fly at incredible speeds-etc.-=0A-=0A-
=0Ado not archive=0A-=0A=0A________________________________=0A=0AFrom:Law
rence Williams <lnawms@yahoo.com>=0ATo: Pietlist < pietenpol-list@matronics
.com >=0ASent: Monday, December 29, 2008 1:31:53 PM=0ASubject: Pietenpol-Li
st: re:up too late tonight-Patches=0AWhat will be the criteria for who gets
/wears a Pietenpol patch? =0A-=0AOur newsletter editor and a number of li
sters seem to hold the view that there is no such thing as a Pietenpol Air
Camper. I think the P.C. designation currently in use is "Snowflake" which
should open up an entirely new logo for our patch.=0A-=0AAnother interest
ing question comes up when considering the annual "Pietenpol" reunion at Br
odhead and, since there are no Pietenpol Air Campers, can there really be a
ny legitimate representative aircraft on the line at OSH ?=0A-=0AWhere's
Chris Egsgaard when he's needed?=0A-=0ALarry Williams- xcg, xcmr, epp
===============0A
Message 4
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Subject: | Plane sitting: need list advice on elevator control horns |
Barry, Gary, Oscar, Don, and others,
Thanks much for the advice. I plan to remove the bell crank today,
repair if possible, make new one if not. However, the slack in the
lower elevator cable is of primary concern to me. As Barry points
out, it may indicate additional trouble. So, what are the
possibilities? I will list some, please comment on these, and add
others that you think of. I will check out all suggestions this
afternoon. Again, your time and thoughts are much appreciated.
1. The cable stretched. Seems unlikely as this is a 1/8" cable and
there wasn't that much tension. However, it is a possibility. Is
there a way to determine whether it stretched?
2. A horn of the large bell crank behind the pilot's seat also bent.
Or, the bracket assembly pulled loose or some other part of the
assembly was damaged. This seems unlikely for a couple of reasons.
First, I looked it over pretty closely and wiggled it all around. All
seems to be in order. Second, the elevator cables on the other side
are still just fine. Third, the whole thing is hell-for-stout
compared to the rest of the elevator system. However, please make
suggestions about what you think is the critical item(s) to inspect
on this.
3. The elevator leading edge (where the front of the bell crank is
attached) was damaged. I have not removed the bell crank entirely, so
this remains to be inspected. I got part way through this before the
sun set.
4. The entire horizontal tail assembly was pulled forward on that
side. I have looked closely at this, and did not see or feel any
looseness that would suggest this is happened.
5. Please add your own suggestions.
Thanks again,
Jeff
>Jeff
>The stretch in the cable might be an indication of additional
>trouble. There could be damage to something else in the system and
>not just isolated to the horn. Other damage could occur before the
>horn gave way and relieved the stress. I know you did not want to
>hear this, but my $ .02 worth.
>Barry
>( still groggy from a late night at the Big Piet Factory)
>
>----- Original Message -----
>From: <mailto:jboatri@emory.edu>Jeff Boatright
>To: <mailto:pietenpol-list@matronics.com>pietenpol-list@matronics.com
>Sent: Monday, December 29, 2008 4:11 PM
>Subject: Pietenpol-List: Plane sitting: need list advice on elevator
>control horns
>
>Dear Pieters,
>
>Today my instructor and I managed to damage the Piet while still in
>its chocks; we bent the upper horn of the left elevator bell crank.
>I need your advice on repairs.
>
>How it happened: I was sitting in the cockpit. The tail was resting
>on a sawhorse. The instructor removed the sawhorse to lower the
>tail. The sawhorse wasn't placed far enough away and it caught the
>lower elevator cable. The tail was lowered all the way to ground
>without this being noticed. The upper horn bent over about 45
>degrees towards the centerline (towards the rudder). We bent the
>horn back, and of course the horn now looks like an hourglass when
>viewed from fore or aft. Oddly, the lower cable has a little more
>slack than before; definitely more than the lower elevator cable on
>the other side. There does not appear to be any damage at all to the
>large, bell crank in the fuselage (behind the pilot's seat) at the
>other end of the cable.
>
>Note that the bell crank appears to be built to plans.
>
>The concerns:
>
>1. Why is the cable slack even when the horn was bent back to
>vertical? I guess the cable could have stretched, but this is an
>eighth inch cable and I weigh 180. Doesn't seem like there would be
>that much tension.
>
>2. Removing and replacing the bell crank will take a lot of effort
>and I want to go flying. Now. Could stiffeners be riveted to the
>horn instead? How much strength has been lost due to the bend-unbend
>cycle, and how much strength is needed here?
>
>3. If it must be removed and replaced/rebuilt, what procedure would
>require the least number of steps to accomplish this, with minimal
>further damage?
>
>Thanks for any advice on this. I am seriously bummed as I planned to
>fly all this week!
>
>Jeff
>
>
Message 5
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Subject: | Plane sitting: need list advice on elevator control |
horns
Jeff,
You reported that you tried to bend the horn back to position, but that it
ended up looking a little like an hour glass. That alone would probably
account for a dimensional change from where the original hole was.
Furthermore, once the horn was bent, you really have no way of knowing
exactly where the original position was. It is conceivable that the
fabricator may not have had the horn straight to begin with. It may have
been favoring the opposite direction.
I'm glad you have decided to give it a thorough inspection.just don't waste
time chasing ghosts.
Gary Boothe
Cool, Ca.
Pietenpol
WW Corvair Conversion
Tail done, working on fuselage (endless metal parts!)
(12 ribs down.)
_____
From: owner-pietenpol-list-server@matronics.com
[mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Jeff
Boatright
Sent: Tuesday, December 30, 2008 6:41 AM
Subject: Pietenpol-List: Plane sitting: need list advice on elevator control
horns
Barry, Gary, Oscar, Don, and others,
Thanks much for the advice. I plan to remove the bell crank today, repair if
possible, make new one if not. However, the slack in the lower elevator
cable is of primary concern to me. As Barry points out, it may indicate
additional trouble. So, what are the possibilities? I will list some, please
comment on these, and add others that you think of. I will check out all
suggestions this afternoon. Again, your time and thoughts are much
appreciated.
1. The cable stretched. Seems unlikely as this is a 1/8" cable and there
wasn't that much tension. However, it is a possibility. Is there a way to
determine whether it stretched?
2. A horn of the large bell crank behind the pilot's seat also bent. Or, the
bracket assembly pulled loose or some other part of the assembly was
damaged. This seems unlikely for a couple of reasons. First, I looked it
over pretty closely and wiggled it all around. All seems to be in order.
Second, the elevator cables on the other side are still just fine. Third,
the whole thing is hell-for-stout compared to the rest of the elevator
system. However, please make suggestions about what you think is the
critical item(s) to inspect on this.
3. The elevator leading edge (where the front of the bell crank is attached)
was damaged. I have not removed the bell crank entirely, so this remains to
be inspected. I got part way through this before the sun set.
4. The entire horizontal tail assembly was pulled forward on that side. I
have looked closely at this, and did not see or feel any looseness that
would suggest this is happened.
5. Please add your own suggestions.
Thanks again,
Jeff
Jeff
The stretch in the cable might be an indication of additional trouble. There
could be damage to something else in the system and not just isolated to the
horn. Other damage could occur before the horn gave way and relieved the
stress. I know you did not want to hear this, but my $ .02 worth.
Barry
( still groggy from a late night at the Big Piet Factory)
----- Original Message -----
From: Jeff Boatright <mailto:jboatri@emory.edu>
Sent: Monday, December 29, 2008 4:11 PM
Subject: Pietenpol-List: Plane sitting: need list advice on elevator control
horns
Dear Pieters,
Today my instructor and I managed to damage the Piet while still in its
chocks; we bent the upper horn of the left elevator bell crank. I need your
advice on repairs.
How it happened: I was sitting in the cockpit. The tail was resting on a
sawhorse. The instructor removed the sawhorse to lower the tail. The
sawhorse wasn't placed far enough away and it caught the lower elevator
cable. The tail was lowered all the way to ground without this being
noticed. The upper horn bent over about 45 degrees towards the centerline
(towards the rudder). We bent the horn back, and of course the horn now
looks like an hourglass when viewed from fore or aft. Oddly, the lower cable
has a little more slack than before; definitely more than the lower elevator
cable on the other side. There does not appear to be any damage at all to
the large, bell crank in the fuselage (behind the pilot's seat) at the other
end of the cable.
Note that the bell crank appears to be built to plans.
The concerns:
1. Why is the cable slack even when the horn was bent back to vertical? I
guess the cable could have stretched, but this is an eighth inch cable and I
weigh 180. Doesn't seem like there would be that much tension.
2. Removing and replacing the bell crank will take a lot of effort and I
want to go flying. Now. Could stiffeners be riveted to the horn instead? How
much strength has been lost due to the bend-unbend cycle, and how much
strength is needed here?
3. If it must be removed and replaced/rebuilt, what procedure would require
the least number of steps to accomplish this, with minimal further damage?
Thanks for any advice on this. I am seriously bummed as I planned to fly all
this week!
Jeff
Message 6
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Subject: | Alternate Airfoils Riblett 612 and 613.5 |
Those that are using alternate airfoils, how are you determining your CG ra
nge?
-
Ryan Michalkiewicz
-
--- On Thu, 12/25/08, LarryB55 <morrisonintexas@yahoo.com> wrote:
From: LarryB55 <morrisonintexas@yahoo.com>
Subject: Pietenpol-List: 612 and 613.5 Winglets
<morrisonintexas@yahoo.com>
I'm wondering if anyone knows if Mr. Buckolt is still selling the full size
profiles of the 612 and 613.5 airfoil? I have his snail-mail address. I als
o
emailed him through his website, but haven't heard back- thus the question.
Wouldn't want to call and disturb the man.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=221149#221149
=0A=0A=0A
Message 7
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Subject: | Re: Plane sitting: need list advice on elevator control |
horns
Jeff,
I would look for wood splitting near all the attachment bolts in the tail and control
setup. The front of the elevator would be the most likely spot. Also,
check to make sure the brace wire fittings are ok.
I think Gary might be correct on the cable could go slack just from trying to bend
it back. You really dont know where the hole was before it bent and how close
to that position you have it now.
As for fixing, the quickest horn to make would be a flat plate horn. I think the
GN-1 uses flat plate horns. I can check my GN-1 plans when I get home and
give you more detail if you want. Without seeing the damaged horn I would be
hesitant to weld on a patch to repair the horn. Seems like this is an important
part of the plane that contributes to a gentle return to earth.
--------
Chris Tracy
Sacramento, CA
WestCoastPiet.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=221799#221799
Message 8
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|
Just a suggestion but, has anyone considered the design that Steve Eldredge uses
on his caps as a patch design? Its been around awhile representing the fraternity
and I would think Steve would allow it and maybe even produce them since
he has an embroidery outfit already selected. Just a thought.
Larry Williams if youre looking for Chris Egsgaard or Billy Pobah, Id try the
machine shop!
Message 9
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Subject: | Alternate Airfoils Riblett 612 and 613.5 |
Ryan;
You could ask Riblett but If I remember correctly, Doc Mosher's narrative
and analysis on
determining CG range for the Piet pretty much covered most conventional
airfoils at least as a starting point. Here's Doc's commentary, from
Oct. of 2002:
======================
Recently there have been some questions concerning establishing practical
CG limits on homebuilt Pietenpols. Perhaps by going back to the Piet era
(1930s) we can gain an insight about how the CG limits were established in
those days ("That's how Bernie did it.")
Years ago, the CAA published a manual that all the A&E mechanics (Aircraft
& Engine mechanics in those days) used as a standard for airworthy repairs
and alterations. It was called the "Department of Commerce, Civil
Aeronautics Administration Manual 18." The title was "Maintenance, Repair,
and Alteration of Certificated Aircraft, Aircraft Engines, Propellers, and
Instruments." Manual 18 had a bunch of changes over the years, so don't
use a Manual 18 printed later than 1941 or it may not have these 1930s tips
about weight and balance limits.
Back in the early 1930s, the Type Certificate Data Sheets that were issued
by the CAA for each model of certificated airplane were quite brief - 10
or 12 lines of print. Today, those same TCDSs for those antique airplanes
still appear in that brief, sweet, naive condition. Compare that with
today's TCDS of the popular Aeronca Champion - 32 pages!
So if the C.G. limits are not set by the FAA in a TCDS (and of course, on
your homebuilt experimental Pietenpol there is no TCDS), how can you know
where the limits should be? If you can find an old pre-WWII Manual 18 (my
reference is "As amended June 1, 1941), you will find a couple of
interesting rules of thumb about Center of Gravity locations.
For instance, on page II-5, under "E. APPROVED CENTER OF GRAVITY LIMITS"
1. Current Models - stated on the pertinent aircraft specification in
percent of the MAC or in inches aft of a given datum. This information may
be obtained from the local Civil Aeronautics Inspector.
2. Older Models - In the case of those models for which approved limits
are not given on the specification or listing, it will usually be
acceptable to assume the limits to be at 18% and 30% of the MAC for low and
mid wing monoplanes and 22% and 34% of the MAC for high wing monoplanes and
biplanes.
Inasmuch as several models are known to have satisfactory flight
characteristics with the C.G. beyond such arbitrary positions, these should
not be considered hard and fast limits. In such cases, approval will
depend largely upon the recommendations of the examining inspector. The
major consideration governing approval of such cases will be the relative
change in the empty weight C.G. due to the alterations, rather than the
absolute C.G. extremes.
If the approved forward limit thus determined is exceeded, it may be
considered satisfactory provided that it is demonstrated to the local Civil
Aeronautics Inspector that the aircraft can be landed in the three-point
position when landed in the extreme forward condition.
Page II-6 of old CAA Manual 18 goes on to say:
G. DETERMINATION OF LOADED CENTER OF GRAVITY EXTREMES (The most forward
and most rearward C.G. positions obtainable as equipped and with the most
critical distribution of useful load.) The loaded extremes may be
determined either, (1) by weighing the two loaded conditions or, (2) by
computation. Both procedures have a common objective; namely, to
demonstrate that, under the most adverse loading conditions (forward and
aft), the C.G. positions will not exceed the approved limits (Part E)
which have been determined by flight test as the most extreme positions at
which the model will satisfactorily comply with the Civil Air Regulations.
A note on page II-17 states:
When the necessary information is not included in the pertinent
specifications (as for older models), it will be necessary to obtain such
data by computation and actual measurement.
OK, when you start your establishment of loaded C.G. limits on your
Pietenpol, lets use these old CAA limits (22% of the MAC for forward limit
and 34% of the MAC for the rearward limit on your high wing monoplane). A
forward C.G. may make it so you cannot land the airplane in a three-point
position (put another way, the engine is just too heavy for the too-small
elevators at slow speed to overcome). A rearward C.G. starts to get into
problems with stability and spin recovery. Vaughan Askue in his book
Flight Testing Homebuilt Aircraft says "C.G. provides the most direct
method the pilot has for controlling pitch stability. Moving the C.G.
forward increases the effectiveness of the horizontal tail and improves
both static and dynamic stability. The primary objective of a stability
test program is to prove that the airplane has acceptable stability
characteristics at a limiting C.G. This C.G. then becomes the aft C.G.
limit called out in the airplane's limitations. If moving the C.G. limit
forward gives acceptable stability without hurting the utility of the
airplane, then this is the simplest fix for a stability problem.
What does all this mean in your Piet? If you establish the fore and aft
loaded C.G. limits at something like 22% and 34% of the Mean Aerodynamic
Chord and try to stay away from the rear limit as much as possible (that's
the one where instability starts to take over), you will probably be OK.
Historically, most Piets come out of the jig being tail heavy because they
don't have that heavy Ford A engine on the front end of the
teeter-totter. If you increase the arm of the engine weight of a 220#
Corvair engine, for example, (move it 4 or 5 inches forward of where the
Ford used to be) your Piet will probably not be chronically tail
heavy. Then, if you want, you can tweak it by moving the wing fore or aft
- usually aft - to really set the loaded CG between your goal numbers of 22/34%
That's how Bernie did it. It still works. A pound is a pound the world
around.
Oscar Zuniga
San Antonio, TX
mailto: taildrags@hotmail.com
website at http://www.flysquirrel.net
Message 10
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Subject: | Plane sitting: need list advice on elevator control |
Chris wrote-
>Without seeing the damaged horn I would be hesitant to weld on a patch
>to repair the horn. Seems like this is an important part of the plane
>that contributes to a gentle return to earth.
That was my feeling about my rudder horn so I was good and ready to
make a new one. However, my master machinist/welder/shop supervisor
looked it over and told me that I wouldn't need to heat the part before
straightening it out and working it back into its "airfoil" shape
since it had not deformed that severely. As I say, we were good and
ready to make a new part but it was not deemed necessary once we worked
it back out to original shape and dressed it. Hopefully, Jeff's can
be worked back out too.
I think the slack cable situation will end up being Case #3 of the
scenarios he laid out... either crushed or broken wood. And yet, that's
the nice thing about wood: there are many ways to repair it.
Oscar Zuniga
Air Camper NX41CC
San Antonio, TX
mailto: taildrags@hotmail.com
website at http://www.flysquirrel.net
Message 11
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Subject: | Re: Alternate Airfoils Riblett 612 and 613.5 |
Thanks Oscar, looks like great info. I purchased the Riblett book in hopes
to find my answer there but no luck there. Next, how do you determine the
-correct angle of incedence for a non Piet wing?
Ryan M
-
--- On Tue, 12/30/08, Oscar Zuniga <taildrags@hotmail.com> wrote:
From: Oscar Zuniga <taildrags@hotmail.com>
Subject: Pietenpol-List: Alternate Airfoils Riblett 612 and 613.5
<taildrags@hotmail.com>
Ryan;
You could ask Riblett but If I remember correctly, Doc Mosher's narrative
and analysis on
determining CG range for the Piet pretty much covered most conventional
airfoils at least as a starting point. Here's Doc's commentary, from
Oct. of 2002:
======================
Recently there have been some questions concerning establishing practical
CG limits on homebuilt Pietenpols. Perhaps by going back to the Piet era
(1930s) we can gain an insight about how the CG limits were established in
those days ("That's how Bernie did it.")
Years ago, the CAA published a manual that all the A&E mechanics (Aircraft
& Engine mechanics in those days) used as a standard for airworthy repairs
and alterations. It was called the "Department of Commerce, Civil
Aeronautics Administration Manual 18." The title was "Maintenance,
Repair,
and Alteration of Certificated Aircraft, Aircraft Engines, Propellers, and
Instruments." Manual 18 had a bunch of changes over the years, so
don't
use a Manual 18 printed later than 1941 or it may not have these 1930s tips
about weight and balance limits.
Back in the early 1930s, the Type Certificate Data Sheets that were issued
by the CAA for each model of certificated airplane were quite brief - 10
or 12 lines of print. Today, those same TCDSs for those antique airplanes
still appear in that brief, sweet, naive condition. Compare that with
today's TCDS of the popular Aeronca Champion - 32 pages!
So if the C.G. limits are not set by the FAA in a TCDS (and of course, on
your homebuilt experimental Pietenpol there is no TCDS), how can you know
where the limits should be? If you can find an old pre-WWII Manual 18 (my
reference is "As amended June 1, 1941), you will find a couple of
interesting rules of thumb about Center of Gravity locations.
For instance, on page II-5, under "E. APPROVED CENTER OF GRAVITY
LIMITS"
1. Current Models - stated on the pertinent aircraft specification in
percent of the MAC or in inches aft of a given datum. This information may
be obtained from the local Civil Aeronautics Inspector.
2. Older Models - In the case of those models for which approved limits
are not given on the specification or listing, it will usually be
acceptable to assume the limits to be at 18% and 30% of the MAC for low and
mid wing monoplanes and 22% and 34% of the MAC for high wing monoplanes and
biplanes.
Inasmuch as several models are known to have satisfactory flight
characteristics with the C.G. beyond such arbitrary positions, these should
not be considered hard and fast limits. In such cases, approval will
depend largely upon the recommendations of the examining inspector. The
major consideration governing approval of such cases will be the relative
change in the empty weight C.G. due to the alterations, rather than the
absolute C.G. extremes.
If the approved forward limit thus determined is exceeded, it may be
considered satisfactory provided that it is demonstrated to the local Civil
Aeronautics Inspector that the aircraft can be landed in the three-point
position when landed in the extreme forward condition.
Page II-6 of old CAA Manual 18 goes on to say:
G. DETERMINATION OF LOADED CENTER OF GRAVITY EXTREMES (The most forward
and most rearward C.G. positions obtainable as equipped and with the most
critical distribution of useful load.) The loaded extremes may be
determined either, (1) by weighing the two loaded conditions or, (2) by
computation. Both procedures have a common objective; namely, to
demonstrate that, under the most adverse loading conditions (forward and
aft), the C.G. positions will not exceed the approved limits (Part E)
which have been determined by flight test as the most extreme positions at
which the model will satisfactorily comply with the Civil Air Regulations.
A note on page II-17 states:
When the necessary information is not included in the pertinent
specifications (as for older models), it will be necessary to obtain such
data by computation and actual measurement.
OK, when you start your establishment of loaded C.G. limits on your
Pietenpol, lets use these old CAA limits (22% of the MAC for forward limit
and 34% of the MAC for the rearward limit on your high wing monoplane). A
forward C.G. may make it so you cannot land the airplane in a three-point
position (put another way, the engine is just too heavy for the too-small
elevators at slow speed to overcome). A rearward C.G. starts to get into
problems with stability and spin recovery. Vaughan Askue in his book
Flight Testing Homebuilt Aircraft says "C.G. provides the most direct
method the pilot has for controlling pitch stability. Moving the C.G.
forward increases the effectiveness of the horizontal tail and improves
both static and dynamic stability. The primary objective of a stability
test program is to prove that the airplane has acceptable stability
characteristics at a limiting C.G. This C.G. then becomes the aft C.G.
limit called out in the airplane's limitations. If moving the C.G. limit
forward gives acceptable stability without hurting the utility of the
airplane, then this is the simplest fix for a stability problem.
What does all this mean in your Piet? If you establish the fore and aft
loaded C.G. limits at something like 22% and 34% of the Mean Aerodynamic
Chord and try to stay away from the rear limit as much as possible (that's
the one where instability starts to take over), you will probably be OK.
Historically, most Piets come out of the jig being tail heavy because they
don't have that heavy Ford A engine on the front end of the
teeter-totter. If you increase the arm of the engine weight of a 220#
Corvair engine, for example, (move it 4 or 5 inches forward of where the
Ford used to be) your Piet will probably not be chronically tail
heavy. Then, if you want, you can tweak it by moving the wing fore or aft
- usually aft - to really set the loaded CG between your goal numbers of 22
/34%
That's how Bernie did it. It still works. A pound is a pound the world
around.
Oscar Zuniga
San Antonio, TX
mailto: taildrags@hotmail.com
website at http://www.flysquirrel.net
=0A=0A=0A
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Good thought. I've already planned on making hats for the 80th, like I did for
the 70th and 75th. Patches and embroidered t-shirts are in the works too.
If you like it you can buy it. If you want to make your own, you can do that too.
Steve E.
-----Original Message-----
From: owner-pietenpol-list-server@matronics.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of BYD@att.net
Sent: Tuesday, December 30, 2008 10:31 AM
Subject: Pietenpol-List: Patch design
Just a suggestion but, has anyone considered the design that Steve Eldredge uses
on his caps as a patch design? Its been around awhile representing the fraternity
and I would think Steve would allow it and maybe even produce them since
he has an embroidery outfit already selected. Just a thought.
Larry Williams if youre looking for Chris Egsgaard or Billy Pobah, Id try the
machine shop!
Message 13
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Subject: | Alternate Airfoils Riblett 612 and 613.5 |
Ryan asks-
>how do you determine the correct angle of incidence for a
>non Piet wing?
Well, you could go through a bunch of analysis and probably
figure out a good starting point that way, but I'd say an
even easier way would be to start by setting the angle of
incidence of a non-Piet wing the same as for a Piet wing.
It's probably going to require some tweaking no matter what,
unless you use a wing and geometry that someone has already
used and flown and can tell you what angle works.
In order to change the incidence later, you'll have to change
the length of either the front cabanes or the rear ones, as
well as adjusting the front or rear lift struts to keep the
same washout when the incidence is adjusted. One way to
allow for adjustment of the cabane lengths is to use
adjustable connections for either the front or the rear
cabanes (I think I'd do the rear ones unless that adds more
complexity, such as if your fuel line runs down one of the
cabanes from a center-section fuel tank). That could be done
by attaching the top ends to the wing with fork ends or
something similar instead of fixed mounts.
Oscar Zuniga
Air Camper NX41CC
San Antonio, TX
mailto: taildrags@hotmail.com
website at http://www.flysquirrel.net
Message 14
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Subject: | Re: Patch design |
Steve
Sounds great you planning on showing us the patch before it goes into production?
John
------Original Message------
From: Steve Eldredge
Sender: owner-pietenpol-list-server@matronics.com
ReplyTo: pietenpol-list@matronics.com
Sent: Dec 30, 2008 8:23 PM
Subject: RE: Pietenpol-List: Patch design
Good thought. I've already planned on making hats for the 80th, like I did for
the 70th and 75th. Patches and embroidered t-shirts are in the works too.
If you like it you can buy it. If you want to make your own, you can do that too.
Steve E.
-----Original Message-----
From: owner-pietenpol-list-server@matronics.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of BYD@att.net
Sent: Tuesday, December 30, 2008 10:31 AM
Subject: Pietenpol-List: Patch design
Just a suggestion but, has anyone considered the design that Steve Eldredge uses
on his caps as a patch design? Its been around awhile representing the fraternity
and I would think Steve would allow it and maybe even produce them since
he has an embroidery outfit already selected. Just a thought.
Larry Williams if youre looking for Chris Egsgaard or Billy Pobah, Id try the
machine shop!
Sent from my Verizon Wireless BlackBerry
Message 15
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Subject: | Re: Plane sitting: need list advice on elevator control |
Well gang, I'm back from the airfield, and things look pretty good. I
pulled the bell crank and handed it over to the resident "master
machinist/welder/shop supervisor" and he said "that's unserviceable -
but we'll MAKE it serviceable and STRONGER". He heated it a bit,
straightened it, reformed it, then welded a stiffener along the
length of the horn that was damaged. It is heavier than the original,
but quite strong. It looked true from every angle, but the proof was
in the pudding...
Inspection of the wood showed no problems. It appears that the horn
and the ear tabs of the bell crank, which had been quite deformed,
took all the strain.
I bolted the repaired bell crank back in and connected the cables.
Astoundingly, all the holes lined up in the wood, and there was no
slack in the cables. I guess you just can't beat 30 years of
machining, welding, and fabricating in the field and shop. I would
have bet any amount of my wife's paycheck that we would end the day
with having to build a totally new one.
Tomorrow I patch the fabric, and then maybe, go flying on the first!
Thanks for all the input,
Jeff
At 1:21 PM -0600 12/30/08, Oscar Zuniga wrote:
>
>
>Chris wrote-
>
>>Without seeing the damaged horn I would be hesitant to weld on a patch
>>to repair the horn. Seems like this is an important part of the plane
>>that contributes to a gentle return to earth.
>
>That was my feeling about my rudder horn so I was good and ready to
>make a new one. However, my master machinist/welder/shop supervisor
>looked it over and told me that I wouldn't need to heat the part before
>straightening it out and working it back into its "airfoil" shape
>since it had not deformed that severely. As I say, we were good and
>ready to make a new part but it was not deemed necessary once we worked
>it back out to original shape and dressed it. Hopefully, Jeff's can
>be worked back out too.
>
>I think the slack cable situation will end up being Case #3 of the
>scenarios he laid out... either crushed or broken wood. And yet, that's
>the nice thing about wood: there are many ways to repair it.
>
>Oscar Zuniga
>Air Camper NX41CC
>San Antonio, TX
>mailto: taildrags@hotmail.com
>website at http://www.flysquirrel.net
>
--
---
Jeffrey H. Boatright, Ph.D.
Associate Professor of Ophthalmology
Emory University School of Medicine
Editor-in-Chief
Molecular Vision
Message 16
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Subject: | Re: Plane sitting: need list advice on elevator control |
Hey Jeff
Sounds like you got her fixed up without any ancillary issues to deal with.
Now about that paycheck bet, I met your wife a really nice person. I doubt she
would be all that nice having found out you bet her paycheck!
Glad to hear you'll be back in action tomorrow
Fly safe
John
Sent from my Verizon Wireless BlackBerry
-----Original Message-----
From: Jeff Boatright <jboatri@emory.edu>
Subject: Re: Pietenpol-List: Plane sitting: need list advice on elevator control
Well gang, I'm back from the airfield, and things look pretty good. I
pulled the bell crank and handed it over to the resident "master
machinist/welder/shop supervisor" and he said "that's unserviceable -
but we'll MAKE it serviceable and STRONGER". He heated it a bit,
straightened it, reformed it, then welded a stiffener along the
length of the horn that was damaged. It is heavier than the original,
but quite strong. It looked true from every angle, but the proof was
in the pudding...
Inspection of the wood showed no problems. It appears that the horn
and the ear tabs of the bell crank, which had been quite deformed,
took all the strain.
I bolted the repaired bell crank back in and connected the cables.
Astoundingly, all the holes lined up in the wood, and there was no
slack in the cables. I guess you just can't beat 30 years of
machining, welding, and fabricating in the field and shop. I would
have bet any amount of my wife's paycheck that we would end the day
with having to build a totally new one.
Tomorrow I patch the fabric, and then maybe, go flying on the first!
Thanks for all the input,
Jeff
At 1:21 PM -0600 12/30/08, Oscar Zuniga wrote:
>
>
>Chris wrote-
>
>>Without seeing the damaged horn I would be hesitant to weld on a patch
>>to repair the horn. Seems like this is an important part of the plane
>>that contributes to a gentle return to earth.
>
>That was my feeling about my rudder horn so I was good and ready to
>make a new one. However, my master machinist/welder/shop supervisor
>looked it over and told me that I wouldn't need to heat the part before
>straightening it out and working it back into its "airfoil" shape
>since it had not deformed that severely. As I say, we were good and
>ready to make a new part but it was not deemed necessary once we worked
>it back out to original shape and dressed it. Hopefully, Jeff's can
>be worked back out too.
>
>I think the slack cable situation will end up being Case #3 of the
>scenarios he laid out... either crushed or broken wood. And yet, that's
>the nice thing about wood: there are many ways to repair it.
>
>Oscar Zuniga
>Air Camper NX41CC
>San Antonio, TX
>mailto: taildrags@hotmail.com
>website at http://www.flysquirrel.net
>
--
---
Jeffrey H. Boatright, Ph.D.
Associate Professor of Ophthalmology
Emory University School of Medicine
Editor-in-Chief
Molecular Vision
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