Today's Message Index:
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1. 06:54 AM - Washout & Rigging (Rcaprd@aol.com)
2. 09:19 AM - Re: Rudder bar or rudder pedals (Dick Navratil)
3. 04:36 PM - Re: Rudder horn location (Rcaprd@aol.com)
Message 1
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Subject: | Washout & Rigging |
In a message dated 2/18/2006 9:05:06 AM Central Standard Time,
BARNSTMR@aol.com writes:
Tim Willis and I have been discussing a few things off list and lately about
washout. For all of you guys with flying Piets,
1) how much washout do you have?
2) have you ever tried changing it any to see if handling is improved?
I recently found an interesting article about the subject. (link below) It is
a a NACA report done by engineers at Texas A&M in 1953 using washout tests on
a Taylorcraft. (I have been trying to investigate to see if it was my
Taylorcraft. It was owned by A&M at that time). Anyway - The tests looked=20at
the
effects of washout and slots on lateral control near stall. The washout was
varied from zero to 8 degrees. They used tufts all across the top surface of
the wing to detect disturbed airflow. The idea is to have the inboard and
center section of the wing stall first with the singtips still flying, so that
the
ailerons remain effective throughout the stall.
I believe the NACA report conclusion was that 4 degrees washout was optimal
for the taylorcraft and thus recommended for light planes.
http://naca.larc.nasa.gov/reports/1953/naca-tn-2948/index.cgi?thumbnail11
It might be interesting to consider tests of such on the Piet wing to
determine its optimum. Any thoughts?
Terry B.
Hey Terry,
This is an area of aerodynamics that has always interested me. I tried
printing the pages of that naca report, because it's easier for me to relax=20in
the lazy boy chair to read, but my printer cut off the right side of the page.
Here is my understanding on the subject, and what I did:
A Hershey bar wing inherently stalls first at the inboard portion of the
wing, and washout increases drag. Washout is much more common in Tapered Wings,
because they inherently stall the tips first. Therefore, why even rig any
washout in the wing ? Because any slight discrepancies in construction, slight
errors in rigging, and in the event you don't keep the ball in the middle, I
suppose you could stall one wing before the other, albeit a rare occasion. =20I
have Never felt one tip stall before the other...it always breaks, or actually
just Mushes, straight ahead, however, I haven't tried it with the ball way off
center - at altitude of course.
The Pietenpol wing has a fairly sharp leading edge, which causes a
sharper stall break, than say the ol' T-craft. Have you ever noticed how big the
leading edge radius is on an aerobatic plane ? Those wings have a higher
critical angle of attack (the angle at which the wing begins to stall), but=20pay
for
it with an increase in drag. They have excess power to overcome the drag
penalty. Nothing is free !! The Pietenpol wing is All about Lift. It creates
a
Lot of lift at airspeeds that the T-craft wing isn't even considering flying
yet.
When I was flying in the Test Phase of my plane, I re-rigged my wing
several times, because I had a slightly Left Wing Heavy condition. I use the
plans built 'Lollipop' fittings at the upper lift strut fittings, so when I
re-rigged it was more of an adjustment in Symmetry, as opposed to changing the
length of the lift struts. I came to find that the front strap across the bottom
of the fuselage was the primary cause of the left wing heavy condition. I
nitially I didn't have any bolts through that strap, into the ash cross member.
Early on, that strap began to have a gap between it, and the bottom of the
fuselage. I thought it was because of the dimension change in the wood with the
season, and couldn't imagine that slight dimension change could cause some
washout, and a wing heavy condition. Came to find the cause was hard landings.
I
installed a #10 bolt down through the center of the ash cross piece and
strap... Presto !! Most all of the left wing heavy condition disappeared. =20Then
the
darn thing began to show a gap again, between the center, and the left side.
I now have three bolts down through the ash cross piece / cross strap, spaced
evenly.
Hard landings in a Pietenpol are because as you roundout for landing and
increase the angle of attack, the drag increases dramatically and rapidly
decreases the airspeed...as opposed to a sharp stall break. The sharp stall break
just isn't there in the Pietenpol wing.
To conclude, I have about 1/16" to 1/8" washout in my wingtips, which
probably is about 1=BA or so. The wing is rigged straight (no dihedral), and just
slightly err towards washout. Now, instead of testing the 'Runway Hardness',
I try to land as softly as a butterfly with sore feet !!
Chuck G.
NX770CG
p.s. them ol' boys from Texas A&M probably got hold of some Federal money to
go play around in the sky with the Taylorcraft, learned a Lot, shared their
findings with us, and I'm sure they had a Lot of Fun !!
Message 2
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Subject: | Re: Rudder bar or rudder pedals |
On the rudder horn, the GN-1 mounts the horn in a totally different location.
Structurally it shouldn't be a problem although you may want to look at the location
of the hinge and keep one hinge close to the horn.
On the question of the rudder bar, I currently have a rudder bar, which I really
don't care for that much. On my new project I'm putting in J-3 pedals. I
dont have any specific complaints about the bar but with the pedals, I will be
able to adjust them better for distance. It's a matter of choice.
Dick N.
----- Original Message -----
From: John and Phyllis Smoyer
To: pietenpol-list@matronics.com
Sent: Saturday, February 18, 2006 11:50 AM
Subject: Pietenpol-List: Rudder bar or rudder pedals
Pieters: from a pilot's point of view, which is preferred? If rudder pedals
are used, how big should the pedals be, and where should they be located? Thanks.
John Smoyer
Message 3
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Subject: | Re: Rudder horn location |
In a message dated 2/18/2006 12:11:26 PM Central Standard Time,
jpsmoyer@verizon.net writes:
Have any of you ever experimented with the vertical position of the rudder
horn? I've located it about where the plans indicate, although that location is
not dimensioned. What would happen if the horn were at a lower location?
Reason I ask is that it seems like this would make for an easier (straighter)
cable run from the rudder bar, maybe even avoid the need for a pulley or hard
wood block to guide the control cable back to the horn. Thanks and best regards,
John Smoyer
John,
If you locate the rudder horn down low, you will increase the torsional load
on the upper portion of the rudder, which could lead to Flutter. No worries
about the cable run with hardwood fairleads. Definitely not pulleys. AC43.13
says you can deflect a cable up to 7=BA without a pulley. It's much more than
that, where the control stick to bellcrank pass under the seat, and because=20of
the design load of the cables, there's not even a need for pulleys in that
location, either. Just don't use stainless cables where a change in direction
is
needed.
As far as rudder pedals go, they add a Lot of additional pieces that Must
be there, or you will over stress the rudder horn. Just remember - 'If it
isn't there, it can't break', and the Pietenpol motto : Keep it Simple !!
Chuck G.
NX770CG
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