Today's Message Index:
----------------------
1. 08:33 AM - wind tunnel (Christian Bobka)
2. 09:48 AM - Re: Aircamper for Realflight G2 program (N925WB1@aol.com)
3. 10:19 AM - Long fuse (dpaul)
4. 03:01 PM - Center of Gravity Computations (Ted Tuckerman)
5. 05:32 PM - Re: Center of Gravity Computations (walt evans)
6. 05:39 PM - Re: Center of Gravity Computations (Isablcorky@aol.com)
7. 06:53 PM - Metal Primer (Lynn & Doris Knoll)
8. 07:40 PM - Re: Metal Primer (Jack Phillips)
9. 08:14 PM - Re: Center of Gravity Computations (Rcaprd@aol.com)
10. 08:48 PM - Re: Center of Gravity Computations (Bert Conoly)
11. 08:56 PM - Re: Long fuse (Rcaprd@aol.com)
12. 08:56 PM - Sorry guys , Carl Levken (DOUGLAS BLACKBURN)
13. 09:08 PM - Re: Center of Gravity Computations (Rcaprd@aol.com)
Message 1
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--> Pietenpol-List message posted by: "Christian Bobka" <bobka@compuserve.com>
Robert,
Sorry to take a while to get back to you on this topic.
I would be very interested in seeing a properly executed wind tunnel
analysis of the Piet airfoil. This has come up a number of times on this
venue and we never seem to be able to organize well enough to do it.
I know Greg Cardinal would like to see it as well as Holcomb and a few
others.
What chord size and width are you contemplating? Would you make the airfoil
just like the real one with ribstitches and everything to have the surface
as close to actual as possible? I believe the holcomb's Aerodrome website
has an analysis of the airfoil using one of the canned programs. Does the
wind tunnel at SIU work at MSL density or is it pressurized?
Chris Bobka
Message 2
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| Subject: | Re: Aircamper for Realflight G2 program |
DJ,
A Piet on G2 would be the greatest!!! I'll take mine with the -A, straight
gear, M/C wheels, and a tailskid.
Yeah!!! ;-)
-Wayne
Message 3
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Dear List,
Is anyone flying a Piet with the long fuselage, who extended the front a few
inches, and is using a Continental 65hp for power? After looking at a lot of
Piets and reading list opinions, I added 6 inches to the front of my fuse.
(Which I can cut off later if it turns out to be a mistake). Anyway, before I
permanently attach my wood landing gear w/motorcycle wheels, I would like to
know for sure where the center of the axle should be in relation to the firewall.
One of the list members, a few weeks ago, said that the center of the wheel
should be back 21" from the firewall on the long fuse. The note said something
about a PhD, so with respect, I've got mine ready to go - 21" back from
where the ORIGINAL firewall would have been. Opinions would be very welcome.
Thanks.
Dave Paulsen - Missouri
Message 4
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| Subject: | Center of Gravity Computations |
This is in response to Chuck Gantzer's post of yesterday, suggesting the best way
to compare Pietenpols with regard to empty weight center of gravity (EWCG)
is to express EWCG in inches aft of the wing leading edge. I'd like to offer
the opinion that a better way is to express EWCG is as a percentage of mean aerodynamic
chord (MAC), particularly when discussing homebuilts that typically
have dimensional variances among individual aircraft.
The datum is an imaginary vertical plane from which all fore and aft measurements
are taken, to determine the arm of a particular item of weight. On a factory-built
aircraft, the datum is specified in the type certificate data sheet.
In a homebuilt (i.e., non-type certificated) it is wherever the builder wants
it to be. The important thing is that it be a location easy to measure from,
preferably one from which you can drop a plumb bob straight to the floor, allowing
you to mark the datum on the floor, again for ease of measurement. You
don't want to select as a datum a point whose location is changeable, like (on
a Pietenpol) the wing leading edge, or the front face of the propeller. On a
Piet, the firewall is probably as good a location as any.
If you assume the firewall face as your datum, your EWCG will be some number of
inches aft of the datum. Your wing leading edge (LE MAC) will also be some number
of inches aft of the datum. Take the EWCG location in inches, and subtract
the LE MAC location in inches. Divide the result by the MAC length in inches.
The result is your EWCG expressed as a percentage of MAC. For example,
if an aircraft has an EWCG 120 inches aft of the datum, and a wing leading edge
100 inches aft of the datum, and a MAC of 60 inches, your EWCG is at 33 1/3%
MAC. ((120 - 100)/60)
Ted Tuckerman
Message 5
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| Subject: | Re: Center of Gravity Computations |
Ted,
The final "go/no go" for CG is if the balance fits into the "window" on the wing,
no matter where it is. You can go through all the loop de loops and stretch
this and that, but the final numbers are on the wing from the leading edge.
Think this is the common denominator that Chuck was needing. :
)
walt evans
NX140DL
----- Original Message -----
From: Ted Tuckerman
To: pietenpol-list@matronics.com
Sent: Sunday, February 15, 2004 6:00 PM
Subject: Pietenpol-List: Center of Gravity Computations
This is in response to Chuck Gantzer's post of yesterday, suggesting the best
way to compare Pietenpols with regard to empty weight center of gravity (EWCG)
is to express EWCG in inches aft of the wing leading edge. I'd like to offer
the opinion that a better way is to express EWCG is as a percentage of mean
aerodynamic chord (MAC), particularly when discussing homebuilts that typically
have dimensional variances among individual aircraft.
The datum is an imaginary vertical plane from which all fore and aft measurements
are taken, to determine the arm of a particular item of weight. On a factory-built
aircraft, the datum is specified in the type certificate data sheet.
In a homebuilt (i.e., non-type certificated) it is wherever the builder wants
it to be. The important thing is that it be a location easy to measure from,
preferably one from which you can drop a plumb bob straight to the floor, allowing
you to mark the datum on the floor, again for ease of measurement. You
don't want to select as a datum a point whose location is changeable, like (on
a Pietenpol) the wing leading edge, or the front face of the propeller. On
a Piet, the firewall is probably as good a location as any.
If you assume the firewall face as your datum, your EWCG will be some number
of inches aft of the datum. Your wing leading edge (LE MAC) will also be some
number of inches aft of the datum. Take the EWCG location in inches, and subtract
the LE MAC location in inches. Divide the result by the MAC length in inches.
The result is your EWCG expressed as a percentage of MAC. For example,
if an aircraft has an EWCG 120 inches aft of the datum, and a wing leading edge
100 inches aft of the datum, and a MAC of 60 inches, your EWCG is at 33 1/3%
MAC. ((120 - 100)/60)
Ted Tuckerman
Message 6
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| Subject: | Re: Center of Gravity Computations |
Walt,
I thought I have been e mailing with a sane man. You don't mean to tell us
that you would loop de loop in a Piet like Mike Cuy, Chuck Gantzer and as few
others.
Corky in La
Do not archive
Message 7
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What type/brand do you fellow Pieters recommend?
Lynn Knoll
Wichita
Message 8
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I've had very good luck with PolyFiber's Epoxy primer. I started using
Randolph's Epoxy primer but found that it just doesn't hold up. Once the
PolyFiber primer is cured (it's a 2-part system) the only way to remove it
is with a sandblaster. Very tough. They make two colors - white and green.
I find the green to be easier to apply, and it seems to be tougher than the
white.
Jack Phillips
Raleigh, NC, where we are getting another 4" of snow tonight. Sure wish it
would warm up soon so I can start spray painting.
-----Original Message-----
From: owner-pietenpol-list-server@matronics.com
[mailto:owner-pietenpol-list-server@matronics.com]On Behalf Of Lynn & Doris
Knoll
Subject: Pietenpol-List: Metal Primer
What type/brand do you fellow Pieters recommend?
Lynn Knoll
Wichita
Message 9
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| Subject: | Re: Center of Gravity Computations |
--> Pietenpol-List message posted by: Rcaprd@aol.com
In a message dated 2/15/04 5:01:41 PM Central Standard Time,
ws133b341@cox.net writes:
<< I'd like to offer the opinion that a better way is to express EWCG is as a
percentage of mean aerodynamic chord (MAC), particularly when discussing
homebuilts that typically have dimensional variances among individual aircraft.
>>
Ted,
Determining the E.W.C.G. could certainly be done as a percentage of Mean
Aerodynamic Chord, but it would require an additional calculation. Keeping
everything in inches, is just easier and simpler to compare. My intention is to
show a common baseline to compare.
The datum called out in the plans is the Firewall. For comparison,
everyone should keep it there, and deal with the math of negative numbers. The
problem with this, is the negative arm, ahead of the firewall, which makes it
more complicated when doing weight and balance. Positive times Positive equals
Positive. Negative times Negative equals Positive. Negative times Positive
equals Negative. The contemporary location of the datum is ahead of the prop,
that way all numbers are a positive number.
One thing to keep in mind, that I forgot to mention yesterday, is that
B.H.P. called out the LOADED Center of Gravity Range (envelope) is between 1/4
to 1/3 of the chord. This is between 25% and 33 1/3% of the chord, or
between 15" and 20", aft of the Leading Edge. Also keep in mind this is for the
'Pietenpol FC10' airfoil. And remember, this is the LOADED Center of Gravity
range, not an Empty Weight Center of Gravity Range. There is no E.W.C.G range.
Fly safe, and stay in your envelope !!
Chuck Gantzer
NX770CG
in serious need of warmer weather
Message 10
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| Subject: | Re: Center of Gravity Computations |
--> Pietenpol-List message posted by: "Bert Conoly" <bconoly@earthlink.net>
Chuck- The interesting thing about using a EWCG is that it's really easy to
use it to determine how far out to extend an engine mount to accomodate a
different engine, prop, cowling, or Heaven Forbid, adding ballast to get the
loaded CG right. As long as you use a CG datum between the aircraft CG and
the engine CG, it's a simple exercise to build up a spreadsheet and play
with engine weights, prop weights, motor mount dimensions etc. I found the
firewall a great datum to use. But you're right that the EWCG has to be
referenced back to the LOADED CG at some point.
I recently went through this exercise in doing the W&B for a Boredome
Fighter. Had to move the engine WAY out front for a VW engine.
It's all about the math.
Bert
----- Original Message -----
From: <Rcaprd@aol.com>
Subject: Re: Pietenpol-List: Center of Gravity Computations
> --> Pietenpol-List message posted by: Rcaprd@aol.com
>
> In a message dated 2/15/04 5:01:41 PM Central Standard Time,
> ws133b341@cox.net writes:
>
> << I'd like to offer the opinion that a better way is to express EWCG is
as a
> percentage of mean aerodynamic chord (MAC), particularly when discussing
> homebuilts that typically have dimensional variances among individual
aircraft.
> >>
>
> Ted,
> Determining the E.W.C.G. could certainly be done as a percentage of
Mean
> Aerodynamic Chord, but it would require an additional calculation.
Keeping
> everything in inches, is just easier and simpler to compare. My intention
is to
> show a common baseline to compare.
> The datum called out in the plans is the Firewall. For comparison,
> everyone should keep it there, and deal with the math of negative numbers.
The
> problem with this, is the negative arm, ahead of the firewall, which makes
it
> more complicated when doing weight and balance. Positive times Positive
equals
> Positive. Negative times Negative equals Positive. Negative times
Positive
> equals Negative. The contemporary location of the datum is ahead of the
prop,
> that way all numbers are a positive number.
> One thing to keep in mind, that I forgot to mention yesterday, is that
> B.H.P. called out the LOADED Center of Gravity Range (envelope) is between
1/4
> to 1/3 of the chord. This is between 25% and 33 1/3% of the chord, or
> between 15" and 20", aft of the Leading Edge. Also keep in mind this is
for the
> 'Pietenpol FC10' airfoil. And remember, this is the LOADED Center of
Gravity
> range, not an Empty Weight Center of Gravity Range. There is no E.W.C.G
range.
> Fly safe, and stay in your envelope !!
>
> Chuck Gantzer
> NX770CG
> in serious need of warmer weather
>
>
Message 11
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--> Pietenpol-List message posted by: Rcaprd@aol.com
In a message dated 2/15/04 12:20:12 PM Central Standard Time,
dpaul@fidnet.com writes:
<< Is anyone flying a Piet with the long fuselage, who extended the front
a few inches, and is using a Continental 65hp for power? After looking at a
lot of Piets and reading list opinions, I added 6 inches to the front of my
fuse. (Which I can cut off later if it turns out to be a mistake). Anyway,
before I permanently attach my wood landing gear w/motorcycle wheels, I would
like to know for sure where the center of the axle should be in relation to the
firewall. One of the list members, a few weeks ago, said that the center of
the wheel should be back 21" from the firewall on the long fuse. The note said
something about a PhD, so with respect, I've got mine ready to go - 21" back
from where the ORIGINAL firewall would have been. Opinions would be very
welcome. Thanks. >>
Dave,
The axle placement is a measurement from the firewall, but it's
relationship is to the wing - on a taildragger, it's usually about 16% or 17% chord,
behind the leading edge.
The front 6" extension you have will greatly reduce the possibility of
needing to move your wing back from vertical, to get the C.G. correct -
especially if you weigh over 200 lbs.
On the 'Improved AirCamper', short fuse, the axle is 17" aft of datum
(firewall), and the wing leading edge is 7 1/2" aft of datum. This puts the axle
16% aft of the leading edge. On my short fuse, I moved the wing back 3 1/2",
which puts the axles at 6" or 10% aft of the leading edge, but I have brakes
and it reduces the possibility of nose over. However, I never use the brakes
to slow down the landing roll...only use them to do a run - up, and for
taxiing in tight quarters.
On the 'Long fuselage', 3" is added to the forward station. Assuming the
wing is in the plans location, 21 inches behind this firewall location puts
the axle at 10 1/2" behind the wing leading edge, which is 1" farther back than
the plans call out, and is close to the aft limit of axle placement...unless
you tilt the cabane struts and move your wing aft, but then you already have
that 6" fuse extension...
Chuck G.
Message 12
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| Subject: | Sorry guys , Carl Levken |
Carl, please resend an email to my address, I have lost your email address. twinboom@msn.com
Doug Blackburn
Do Not Archive
Message 13
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| Subject: | Re: Center of Gravity Computations |
--> Pietenpol-List message posted by: Rcaprd@aol.com
In a message dated 2/15/04 7:39:39 PM Central Standard Time,
Isablcorky@aol.com writes:
<< Walt,
I thought I have been e mailing with a sane man. You don't mean to tell us
that you would loop de loop in a Piet like Mike Cuy, Chuck Gantzer and as
few
others.
Corky in La
Do not archive >>
When you consider general public opinion, anyone who builds their own
airplane must be a bit less than sane !!
Chuck G.
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