Today's Message Index:
----------------------
1. 03:09 AM - Re: Question about Gross Weight (Jack Phillips)
2. 05:23 AM - my feeelings on dihedral (Michael D Cuy)
3. 05:52 AM - Re: I discoverd something (Cy Galley)
4. 06:17 AM - Re: I discoverd something (TomTravis@aol.com)
5. 07:35 AM - Re: Question about Gross Weight (Isablcorky@aol.com)
6. 07:47 AM - Re: Question about Gross Weight (John Dilatush)
7. 07:59 AM - Re: Question about Gross Weight (Greg Cardinal)
8. 08:13 AM - makes me dizzy at 60 degrees ! (Michael D Cuy)
9. 08:24 AM - spars (flyboy_120@webtv.net (Ed G.))
10. 08:45 AM - Re: spars (ZigoDan@aol.com)
11. 09:37 AM - Re: Question about Gross Weight (Hubbard, Eugene)
12. 10:35 AM - Re: Question about Gross Weight (Mike)
13. 11:44 AM - Re: spars (Ed Grentzer)
14. 11:53 AM - Airfoil (Isablcorky@aol.com)
15. 01:29 PM - Re: spars (travis battreal)
16. 01:47 PM - Re: spars (ZigoDan@aol.com)
17. 01:52 PM - Re: question on dihedral (Borodent@aol.com)
18. 02:15 PM - Carelson spars (lshutks@webtv.net (Leon Stefan))
19. 03:01 PM - Re: Re: fuel gauges (Richard Navratril)
20. 03:24 PM - Re: Question about Gross Weight (Jack Phillips)
21. 03:30 PM - Re: Question about Gross Weight (Jack Phillips)
22. 04:15 PM - Re: I discoverd something (Bert Conoly)
23. 05:33 PM - Re: Question about Gross Weight (ZigoDan@aol.com)
24. 07:05 PM - Re: Airfoil (Ken & Lisa Rickards)
25. 09:35 PM - Re: my feeelings on dihedral (Graham Hansen)
Message 1
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| Subject: | Question about Gross Weight |
--> Pietenpol-List message posted by: "Jack Phillips" <jackphillips@earthlink.net>
OK, I should know better than to make blanket statements like "1" is
overkill". Good points, Mike. Citabria spars are (I believe) six inches in
height, but they are also several feet longer than Pietenpol spars. I was
responding to the remark that some Aeroncas used 3/4" spars. I think 3/4"
is a much more common thickness than 1".
Before deciding on 3/4" spars for my bird, I ran a quick stress analysis,
with a number of assumptions:
3/4" spars
Gross weight 1050 lbs
65% of load carried by front spar, 35% by rear spar
ultimate tensile stress for Sitka Spruce is 9400 psi
no load carried by centersection (actually a pretty fair assumption, it
turns out)
even lift distribution over entire spar length
The result was that with the lift strut fittings as designed by BHP (not
in-line with the struts as modern ones are) the wing is good for about 4.9
G's. If a more modern lift strut attach point is used, which doesn't impart
its own bending moment to the spar, the wing is only good for 3.92 G's
These are ultimate loads, and I wouldn't expect the wing to survive too long
at these loads. This was enough to convince me that Pietenpols have no
business doing aerobatics, but are plenty strong for normal fun flying.
Jack
-----Original Message-----
--> Pietenpol-List message posted by: Mike <bike.mike@verizon.net>
Bernie routed down the center portions of his spars to save weight but
didn't rout the
spar caps. The material in the center of a beam (spar) in bending does very
little
other than carry shear loads. This is why there are many spars with the
"beef"
located at the top and bottom with only a plywood shear web between the
caps.
A much more important measurement than the spar thickness is the spar's
width, from
top to bottom. Before we go writing off Bernie's spars as overkill on
thickness, lets
do a real comparison with these other famously strong wings that includes
spar width,
length of the wing in actual bending (the Piet wing inboard of the strut
attach points
sees less bending load than the outboard portion), comparable flight loads,
etc. A
blanket statement that 1" is overkill because something like a Pitts has
thinner spars
is not really supportable.
The experiences of a very large number of builders who have successfully and
safely
flown 3/4" spars is certainly more reliable than comparing apples and
oranges, but I'm
not sure anyone has any idea how much safety margin is left over when
pulling
significant flight loads on spars thinner than designed.
Mike
Message 2
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| Subject: | my feeelings on dihedral |
--> Pietenpol-List message posted by: Michael D Cuy <Michael.D.Cuy@grc.nasa.gov>
Chris-- Wow. What an interesting post you had about dihedral. My feelings
on dihedral are
that I think just a titch of it in a Piet makes the wing look a bit
better. (like it's not sagging at the tips.)
Guess my approach to building is one of pleasing my eye in some instances.
Good post though !
Mike C.
18 F in Cleve.
Message 3
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| Subject: | Re: I discoverd something |
--> Pietenpol-List message posted by: "Cy Galley" <cgalley@qcbc.org>
I thought is was anhedral. When I spell check it, the correction comes up
"cathedral." Anhedral is what Burt Rutan called it on my Vari Eze.
Cy Galley
Editor, EAA Safety Programs
cgalley@qcbc.org or experimenter@eaa.org
----- Original Message -----
From: "Christian Bobka" <bobka@charter.net>
Subject: Pietenpol-List: I discoverd something
> --> Pietenpol-List message posted by: "Christian Bobka"
<bobka@charter.net>
>
> While researching dihedral I learned that the word meaning "negative
> dihedral" is the word "cathedral". I never could remember whether a
cathode
> was negative or positive. Now I will remember a Cathode is negative...
>
> chris bobka
>
>
Message 4
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| Subject: | Re: I discoverd something |
--> Pietenpol-List message posted by: TomTravis@aol.com
An easy way to remember it is that the word, "catheter" is definitely
negative. Even I can remember that.
Message 5
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| Subject: | Re: Question about Gross Weight |
--> Pietenpol-List message posted by: Isablcorky@aol.com
Jack,
My curiosity compels to ask you, " give me an estimate of G's on a Piet wing
(with 1 1/2 degree DIhedral) in a steep turn of 60 to 90 degrees,cruise speed
"? Thanks
Corky in La
Message 6
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| Subject: | Re: Question about Gross Weight |
--> Pietenpol-List message posted by: "John Dilatush" <dilatush@amigo.net>
----- Original Message -----
From: "Jack Phillips" <jackphillips@earthlink.net>
Subject: RE: Pietenpol-List: Question about Gross Weight
+++++++++++++++++++++
Jack,
In reading your stress analysis, I noticed that you used tensile strength of
the wood. I believe most wood beam failures occur due to compressive
failure of the fibers as opposed to tensile failure. Compressive strength in
wood is usually lower than tensile. Ever notice how a stick breaks?
You might want to go to:
http://www.fpl.fs.fed.us/documnts/FPLGTR/fplgtr113/Ch04.pdf Where there is
a table of compessive strengths of various woods to use in your
calculations.
I hope this helps,
John
+++++++++++++++++++++++++++++++++++
> --> Pietenpol-List message posted by: "Jack Phillips"
<jackphillips@earthlink.net>
>
> OK, I should know better than to make blanket statements like "1" is
> overkill". Good points, Mike. Citabria spars are (I believe) six inches
in
> height, but they are also several feet longer than Pietenpol spars. I was
> responding to the remark that some Aeroncas used 3/4" spars. I think 3/4"
> is a much more common thickness than 1".
>
> Before deciding on 3/4" spars for my bird, I ran a quick stress analysis,
> with a number of assumptions:
>
> 3/4" spars
> Gross weight 1050 lbs
> 65% of load carried by front spar, 35% by rear spar
> ultimate tensile stress for Sitka Spruce is 9400 psi
> no load carried by centersection (actually a pretty fair
assumption, it
> turns out)
> even lift distribution over entire spar length
>
> The result was that with the lift strut fittings as designed by BHP (not
> in-line with the struts as modern ones are) the wing is good for about 4.9
> G's. If a more modern lift strut attach point is used, which doesn't
impart
> its own bending moment to the spar, the wing is only good for 3.92 G's
>
> These are ultimate loads, and I wouldn't expect the wing to survive too
long
> at these loads. This was enough to convince me that Pietenpols have no
> business doing aerobatics, but are plenty strong for normal fun flying.
>
> Jack
>
>
> -----Original Message-----
> --> Pietenpol-List message posted by: Mike <bike.mike@verizon.net>
>
> Bernie routed down the center portions of his spars to save weight but
> didn't rout the
> spar caps. The material in the center of a beam (spar) in bending does
very
> little
> other than carry shear loads. This is why there are many spars with the
> "beef"
> located at the top and bottom with only a plywood shear web between the
> caps.
> A much more important measurement than the spar thickness is the spar's
> width, from
> top to bottom. Before we go writing off Bernie's spars as overkill on
> thickness, lets
> do a real comparison with these other famously strong wings that includes
> spar width,
> length of the wing in actual bending (the Piet wing inboard of the strut
> attach points
> sees less bending load than the outboard portion), comparable flight
loads,
> etc. A
> blanket statement that 1" is overkill because something like a Pitts has
> thinner spars
> is not really supportable.
> The experiences of a very large number of builders who have successfully
and
> safely
> flown 3/4" spars is certainly more reliable than comparing apples and
> oranges, but I'm
> not sure anyone has any idea how much safety margin is left over when
> pulling
> significant flight loads on spars thinner than designed.
> Mike
>
>
Message 7
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| Subject: | Re: Question about Gross Weight |
--> Pietenpol-List message posted by: "Greg Cardinal" <gcardinal@startribune.com>
Constant altitude, 60 deg. bank = 2 g. Airspeed doesn't matter. Load
increases very quickly as the angle of bank steepens.
Greg Cardinal
>>> Isablcorky@aol.com 02/05/03 09:34AM >>>
--> Pietenpol-List message posted by: Isablcorky@aol.com
Jack,
My curiosity compels to ask you, " give me an estimate of G's on a Piet
wing
(with 1 1/2 degree DIhedral) in a steep turn of 60 to 90 degrees,cruise
speed
"? Thanks
Corky in La
Message 8
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| Subject: | makes me dizzy at 60 degrees ! |
--> Pietenpol-List message posted by: Michael D Cuy <Michael.D.Cuy@grc.nasa.gov>
Corky-----do you mean how many g's does a Piet take when it's 60 F or 90 F
or bank angle ?
(has to be a smart @#$ in every group.)
One thing is for sure, the Piet in a 60 bank will turn on a dime. I mean
it's TIGHT. I don't even know
if you could make say a 70 deg. bank in a Piet and not loose
altitude. Even with that big 65 horses up
front like Walt and you and I have. Good question though.
In the older Piets the termites have to join hands in turns like that:)
Mike C.
17 F in Clev.
Message 9
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--> Pietenpol-List message posted by: flyboy_120@webtv.net (Ed G.)
Hi Pieter's ....While we're on the subject of spars I have a question
that's been bugging my curiosity for quite a while. Don't beat me up
here this strictly a theoretical question. Has anyone ever built a wing
with aluminum spars and wooden ribs? The reason I ask is that Carlson's
lists a sweet modified I beam
4 1/2" aluminum spar that they use in some of their kit planes with
slightly higher gross weights than the Piet. If I remember right they
are 45,000 psi tensile and 30,000 psi in shear. They're 9 lbs each and
not too expensive . With a little shimming they would fit the piet ribs.
I plan to use 3/4" spruce spars but Carlson's spars caught my curiosity.
Message 10
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--> Pietenpol-List message posted by: ZigoDan@aol.com
Wag Aero sells a cub replica kit. You can buy the wing kit one of three
ways, all wood, all aluminum, or aluminum with wood ribs. Now I sure don't
if any piets have been built using this technique, but it does seem possible.
Buy the way a couple years ago AS sold the extruded spars blanks for about
$100.00 $150.00 each.
Dan
Message 11
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| Subject: | Question about Gross Weight |
--> Pietenpol-List message posted by: "Hubbard, Eugene" <ehubbard@titan.com>
Mike,
Remember also that the "builder's manual" suggests using 3/4" spars and the
ca. 1960 wing center section supplemental drawing shows 3/4 inch. On that
basis, it's hard to say that 3/4" is "thinner than designed".
Gene
-----Original Message-----
From: Mike [mailto:bike.mike@verizon.net]
Subject: Re: Pietenpol-List: Question about Gross Weight
--> Pietenpol-List message posted by: Mike <bike.mike@verizon.net>
Bernie routed down the center portions of his spars to save weight but
didn't rout the
spar caps. The material in the center of a beam (spar) in bending does very
little
other than carry shear loads. This is why there are many spars with the
"beef"
located at the top and bottom with only a plywood shear web between the
caps.
A much more important measurement than the spar thickness is the spar's
width, from
top to bottom. Before we go writing off Bernie's spars as overkill on
thickness, lets
do a real comparison with these other famously strong wings that includes
spar width,
length of the wing in actual bending (the Piet wing inboard of the strut
attach points
sees less bending load than the outboard portion), comparable flight loads,
etc. A
blanket statement that 1" is overkill because something like a Pitts has
thinner spars
is not really supportable.
The experiences of a very large number of builders who have successfully and
safely
flown 3/4" spars is certainly more reliable than comparing apples and
oranges, but I'm
not sure anyone has any idea how much safety margin is left over when
pulling
significant flight loads on spars thinner than designed.
Mike
Jack Phillips wrote:
> --> Pietenpol-List message posted by: "Jack Phillips"
<jackphillips@earthlink.net>
>
> Citabrias also have 3/4" spars, as do Pitts Specials and many other
> aerobatic planes. 1" is overkill, which is why BHP routed them down. I
> used 3/4" spars fore and aft in my Piet.
>
> Jack
Message 12
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| Subject: | Re: Question about Gross Weight |
--> Pietenpol-List message posted by: Mike <bike.mike@verizon.net>
Jack,
In general, and I'd like Chris Bobka to check his extensive library on this,
ultimate load capability should be 1.5 times service loads, the actual
expected maximum normal loading. That would mean, if your assumptions are
correct, that your 4.9g Piet is a 3.2g airplane at 1050#GW.
However, your tensile strength for spruce seems a little higher than the
more conservative numbers I remember from the cobwebbed past. If the number
is actually 7500 psi, you should have a confidence in only 2.6g, even though
3.9g could be ultimately possible. The 1.5 safety margin should be there to
account for the unforeseen anomaly such as a hidden flaw in the spruce or a
not-so-perfect weld joint.
Since we're building homebuilts, we don't always have to comply with FAA
design guidelines. However, the FAA-mandated load capabilities for
certificated airplanes seem like a good idea to me.
As to John D's question about the term "tensile strength" or "tensile
stress", when used in bending: The number relates to the maximally stressed
fiber in a test specimen at failure. It does not have to actually be
tension as opposed to compression which, as John noted, would be found on
the side towards which the specimen is bent.
In a symmetrical specimen, the compressive stress and the tensile stress
would be equal during bending, though the first fiber to fail could be on
the compressive side.
Mike
>
> --> Pietenpol-List message posted by: "Jack Phillips"
> <jackphillips@earthlink.net>
>
> OK, I should know better than to make blanket statements like "1" is
> overkill". Good points, Mike. Citabria spars are (I believe) six inches in
> height, but they are also several feet longer than Pietenpol spars. I was
> responding to the remark that some Aeroncas used 3/4" spars. I think 3/4"
> is a much more common thickness than 1".
>
> Before deciding on 3/4" spars for my bird, I ran a quick stress analysis,
> with a number of assumptions:
>
> 3/4" spars
> Gross weight 1050 lbs
> 65% of load carried by front spar, 35% by rear spar
> ultimate tensile stress for Sitka Spruce is 9400 psi
> no load carried by centersection (actually a pretty fair assumption, it
> turns out)
> even lift distribution over entire spar length
>
> The result was that with the lift strut fittings as designed by BHP (not
> in-line with the struts as modern ones are) the wing is good for about 4.9
> G's. If a more modern lift strut attach point is used, which doesn't impart
> its own bending moment to the spar, the wing is only good for 3.92 G's
>
> These are ultimate loads, and I wouldn't expect the wing to survive too long
> at these loads. This was enough to convince me that Pietenpols have no
> business doing aerobatics, but are plenty strong for normal fun flying.
>
> Jack
>
Message 13
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--> Pietenpol-List message posted by: "Ed Grentzer" <flyboy_120@hotmail.com>
Thanks Dan...So it is feasable to use aluminum spars with wood ribs.
The Carlson's spar I was looking at is 4 1/2" X .812" (across the
flanges) X 14 ft.6061T aluminum flanged I beam affair for $86.00
each plus shipping....didn't sound too bad...Lets see Mikes termites
eat that sucker!!! Anyone know the best way to fasten ribs to
them??? I don't think it would be a good idea to drill the flanges??
but then the aluminum ribs must be riveted to the flanges. Or are
they?? Still just curious. Ed
>From: ZigoDan@aol.com
>Reply-To: pietenpol-list@matronics.com
>To: pietenpol-list@matronics.com
>Subject: Re: Pietenpol-List: spars
>Date: Wed, 5 Feb 2003 11:44:01 EST
>
>--> Pietenpol-List message posted by: ZigoDan@aol.com
>
>Wag Aero sells a cub replica kit. You can buy the wing kit one of three
>ways, all wood, all aluminum, or aluminum with wood ribs. Now I sure don't
>if any piets have been built using this technique, but it does seem
>possible.
> Buy the way a couple years ago AS sold the extruded spars blanks for
>about
>$100.00 $150.00 each.
>
>Dan
>
>
Message 14
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--> Pietenpol-List message posted by: Isablcorky@aol.com
Pieters,
Would some GNer please tell me what kind of airfoil the GN plan calls for.
Thanks
Corky in La
Message 15
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--> Pietenpol-List message posted by: travis battreal <travisbattreal@yahoo.com>
The J-3 had wooden spars and aluminum ribs.
--- "Ed G." <flyboy_120@webtv.net> wrote:
> --> Pietenpol-List message posted by:
> flyboy_120@webtv.net (Ed G.)
>
> Hi Pieter's ....While we're on the subject of spars
> I have a question
> that's been bugging my curiosity for quite a while.
> Don't beat me up
> here this strictly a theoretical question. Has
> anyone ever built a wing
> with aluminum spars and wooden ribs? The reason I
> ask is that Carlson's
> lists a sweet modified I beam
> 4 1/2" aluminum spar that they use in some of their
> kit planes with
> slightly higher gross weights than the Piet. If I
> remember right they
> are 45,000 psi tensile and 30,000 psi in shear.
> They're 9 lbs each and
> not too expensive . With a little shimming they
> would fit the piet ribs.
> I plan to use 3/4" spruce spars but Carlson's spars
> caught my curiosity.
>
>
>
> Contributions
> any other
> Forums.
>
> latest messages.
> List members.
>
> http://www.matronics.com/subscription
> http://www.matronics.com/FAQ/Pietenpol-List.htm
>
Digests:http://www.matronics.com/digest/pietenpol-list
> http://www.matronics.com/archives
> http://www.matronics.com/photoshare
> http://www.matronics.com/emaillists
>
>
>
>
>
Message 16
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--> Pietenpol-List message posted by: ZigoDan@aol.com
The original later model J3 had Aluminum ribs, wood spars. Just like the
Champ, and later model Chiefs. But despite that for the record I am looking
at a Wag Aero book right now and it say's Aluminum spar wood rib kit. BTW
some early model Chief's and J3's had all wood wings, rib's and spar's.
Right now I have a 41 chief, with all wood wings, just like Chris Bobka's 40
or 39 model.
Ed,
I once replaced a spar on a PA 22-108 Colt. The flange or T part was
drilled, in fact it didn't seem to mater, they put holes all through it. The
ribs were held on with about #4 sheet metal screws. I bought the spar from
Univiar, and it was predrilled, boy did that save some time.
Dan
Message 17
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| Subject: | Re: question on dihedral |
--> Pietenpol-List message posted by: Borodent@aol.com
I would love to hear a responce from piet pilots who have flown more or less
the same plane with dihedral, in one version and wirthout in another version.
If you have experience as above can you judge which form is nicer to fly?
Henry Williams
Message 18
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--> Pietenpol-List message posted by: lshutks@webtv.net (Leon Stefan)
Ed: Those spars look exactly like Piper spars. In fact, I understand
Mr. Carelson was an old Piper engineer-or something. I scrapped out a
couple Piper Pawnees. The ribs have 90 d sheet angles at the spar
openings with small #4 p.k. screws run threw them into the flange of
the spar. 4 screws on each side. So, if Piper did it that way, it must
be ok. It seems to me that the best way attach a Piet wood rib would be
to widen the verticals of the rib at the spar opening so as to have some
material to run a screw threw. Or, if you haven't built your ribs yet,
Carelson has 'T' and "L" angles for making ribs. Ed, here is your chance
to be a pioneer. The first known metal wing Piet! I would look into it
my self, but I already have my ribs and spars built. Leon S.
Message 19
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| Subject: | Re: RE: fuel gauges |
--> Pietenpol-List message posted by: "Richard Navratril" <horzpool@goldengate.net>
Chris
Again thanks for some great points that arrive as I am connecting fuel lines
and such. Which leads to a related question. I have a main tank in the
wing 11 gal. and a header tank in the fuse, 4 gal.with no independant fill,
feed directly from the main tank. The question I have been pondering is the
vent line in the header tank. I have installed a 1/8" line with a petcock
bleed to remove air. Should this have been led back up to the highest point
for venting? I have a fuel guage on the main wing tank but do not intend on
using that reserve header and no guage installed there.
Dick N.
----- Original Message -----
From: "Christian Bobka" <bobka@charter.net>
<pietenpol-list@matronics.com>
Subject: Pietenpol-List: RE: fuel gauges
> --> Pietenpol-List message posted by: "Christian Bobka"
<bobka@charter.net>
>
> Eddie,
>
> Follow these rules:
>
> The tank in the fusealge is the main tank.
>
> The tank in the wing is and auxialry tank.
>
> The fuselage tank must be no closer than 1/2 inch to the firewall.
>
> Both tanks must be vented and vented in such a manner is to prevent ice
> formation on the vent (even in florida).
>
> Both tanks must have a sump and sump drain at their lowest point in a
parked
> attitude.
>
> Air must be able to circulate around the tanks somehow and fumes and
liquid
> fuel must be able to escape down and out from the space beneath the tanks.
>
> The fuel for engine use will not be drawn from the main tank at the sump
but
> at some point higher than the sump.
>
> Test pressure is 3-1/2 psi for the tanks.
>
> And what you asked for: "Where two or more tanks are interconnected and
it
> is impossible to feed from each one separately, only one fuel-level gauge
> need be installed." Obviously the gauge is for the main tank only as the
> aux tank will drain into the main tank.
>
> Copper fuel lines must be annealed after they are bent.
>
> Ed, I hope this helps.
>
> chris
>
>
> -----Original Message-----
> From: Ed Grentzer [mailto:flyboy_120@hotmail.com]
> To: bobka@charter.net
> Subject: fuel gauges
>
>
> Hi Chris...How's it going...good luck with your D.A.R. application..We
> definitely need more qualitied D.A.R.s out there.
> I have a technical question..I'm building a 7.5 gallon wing tank for
the
> forward 15" of my center section. Behind the tank will be a small baggage
> compartment. I'm trying to keep the cg forward as much as I can so this
tank
> is centered above the most fwd/rearward recommended cg measurements. The
> function of the wing tank will just be to replenish the cowl tank during
> flight. I think Walt Evans has a similar set up but with a full sized wing
> tank. Anyhoo..I read somewhere that "each fuel tank must have a fuel
> quantity gauge" My question is if a tank is only used to refill a tank
which
> has a gauge does that tank ( the wing tank) have to have a gauge?? My tank
> mold is finished but if I HAVE TO install a gauge now would be the time to
> add the sender boss to the mold. Thanks in advance. Ed G.
>
>
Message 20
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| Subject: | Question about Gross Weight |
--> Pietenpol-List message posted by: "Jack Phillips" <jackphillips@earthlink.net>
In any plane, with or without dihedral, regardless of cruise speed, a sixty
degree bank will require a 2 G load on the wing, assuming you are neither
climbing or losing altitude. It has nothing to do with the design of the
plane, it's just simple trigonometry. The load on the wing equals the
weight of the aircraft divided by the cosine of the bank angle. The cosine
of 60 degrees is .5000, so the load is the weight of the plane divided by
.5, which is the same as the weight of the plane multiplied by 2. In a 90
degree bank, assuming all the lift forces come from the wing, the load on
the wing approaches infinity since the cosine of 90 degrees is zero.
Sufficiently confused? Me too.
Jack
-----Original Message-----
From: owner-pietenpol-list-server@matronics.com
[mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of
Isablcorky@aol.com
Subject: Re: Pietenpol-List: Question about Gross Weight
--> Pietenpol-List message posted by: Isablcorky@aol.com
Jack,
My curiosity compels to ask you, " give me an estimate of G's on a Piet wing
(with 1 1/2 degree DIhedral) in a steep turn of 60 to 90 degrees,cruise
speed
"? Thanks
Corky in La
Message 21
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| Subject: | Question about Gross Weight |
--> Pietenpol-List message posted by: "Jack Phillips" <jackphillips@earthlink.net>
You're right Mike, the published "G" loading for an airplane includes a 150%
safety factor. That's why I stressed that these were ultimate loads. This
is a 3 G airplane and should not be used for aerobatics. By the way, when I
continued with the simple stress analysis I did, I found that without Jury
struts, the lift struts could buckle under as little as 1.0 negative G's,
which can be produced by strong turbulence. Jury struts are absolutely
necessary.
Jack
-----Original Message-----
From: owner-pietenpol-list-server@matronics.com
[mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Mike
Subject: Re: Pietenpol-List: Question about Gross Weight
--> Pietenpol-List message posted by: Mike <bike.mike@verizon.net>
Jack,
In general, and I'd like Chris Bobka to check his extensive library on this,
ultimate load capability should be 1.5 times service loads, the actual
expected maximum normal loading. That would mean, if your assumptions are
correct, that your 4.9g Piet is a 3.2g airplane at 1050#GW.
However, your tensile strength for spruce seems a little higher than the
more conservative numbers I remember from the cobwebbed past. If the number
is actually 7500 psi, you should have a confidence in only 2.6g, even though
3.9g could be ultimately possible. The 1.5 safety margin should be there to
account for the unforeseen anomaly such as a hidden flaw in the spruce or a
not-so-perfect weld joint.
Since we're building homebuilts, we don't always have to comply with FAA
design guidelines. However, the FAA-mandated load capabilities for
certificated airplanes seem like a good idea to me.
As to John D's question about the term "tensile strength" or "tensile
stress", when used in bending: The number relates to the maximally stressed
fiber in a test specimen at failure. It does not have to actually be
tension as opposed to compression which, as John noted, would be found on
the side towards which the specimen is bent.
In a symmetrical specimen, the compressive stress and the tensile stress
would be equal during bending, though the first fiber to fail could be on
the compressive side.
Mike
>
> --> Pietenpol-List message posted by: "Jack Phillips"
> <jackphillips@earthlink.net>
>
> OK, I should know better than to make blanket statements like "1" is
> overkill". Good points, Mike. Citabria spars are (I believe) six inches
in
> height, but they are also several feet longer than Pietenpol spars. I was
> responding to the remark that some Aeroncas used 3/4" spars. I think 3/4"
> is a much more common thickness than 1".
>
> Before deciding on 3/4" spars for my bird, I ran a quick stress analysis,
> with a number of assumptions:
>
> 3/4" spars
> Gross weight 1050 lbs
> 65% of load carried by front spar, 35% by rear spar
> ultimate tensile stress for Sitka Spruce is 9400 psi
> no load carried by centersection (actually a pretty fair assumption, it
> turns out)
> even lift distribution over entire spar length
>
> The result was that with the lift strut fittings as designed by BHP (not
> in-line with the struts as modern ones are) the wing is good for about 4.9
> G's. If a more modern lift strut attach point is used, which doesn't
impart
> its own bending moment to the spar, the wing is only good for 3.92 G's
>
> These are ultimate loads, and I wouldn't expect the wing to survive too
long
> at these loads. This was enough to convince me that Pietenpols have no
> business doing aerobatics, but are plenty strong for normal fun flying.
>
> Jack
>
Message 22
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| Subject: | Re: I discoverd something |
--> Pietenpol-List message posted by: "Bert Conoly" <bconoly@earthlink.net>
Then why wouldn't "anhedral" mean "no hedral"? ;>)
Whats a hedral, anyway?
Bert
----- Original Message -----
From: "Christian Bobka" <bobka@charter.net>
Subject: RE: Pietenpol-List: I discoverd something
> --> Pietenpol-List message posted by: "Christian Bobka"
<bobka@charter.net>
>
> DJ,
>
> The prefixes A or AN mean "without" so anhedral is no dihedral and no
> cathedral. Atheist meaning without God and anonymous meaning without
name.
>
> Chris Bobka
>
> -----Original Message-----
> From: owner-pietenpol-list-server@matronics.com
> [mailto:owner-pietenpol-list-server@matronics.com]On Behalf Of DJ Vegh
> To: pietenpol-list@matronics.com
> Subject: Re: Pietenpol-List: I discoverd something
>
>
> --> Pietenpol-List message posted by: "DJ Vegh" <aircamper@imagedv.com>
>
> hmmm I've always known it as "anhedral"
>
> DJ Vegh
> N74DV
> www.raptoronline.com
> Mesa, AZ
>
>
> ----- Original Message -----
> From: "Christian Bobka" <bobka@charter.net>
> To: "pietenpol" <pietenpol-list@matronics.com>
> Subject: Pietenpol-List: I discoverd something
>
>
> > --> Pietenpol-List message posted by: "Christian Bobka"
> <bobka@charter.net>
> >
> > While researching dihedral I learned that the word meaning "negative
> > dihedral" is the word "cathedral". I never could remember whether a
> cathode
> > was negative or positive. Now I will remember a Cathode is negative...
> >
> > chris bobka
> >
>
>
> This email has been scanned for known viruses and made safe for viewing by
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>
>
Message 23
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| Subject: | Re: Question about Gross Weight |
--> Pietenpol-List message posted by: ZigoDan@aol.com
Jack,
I absolutely agree about the jury struts, and had mentioned this earlier. I
realize now were I went wrong on saying build per plans. It seems all the
Piets I have seen, including the Last Original have jury struts, so I guessed
they were on the plans. Someone corrected me on this oversight, and asked me
if I were to follow the plans which do not show the jury struts, then would I
also follow the plans by using #7 screws to hold the stabilizer on. Of
course not, AN hardware is the way to go, and I would certainly not leave
jury struts off either. I think the hole debate had been over some UK Piets
having only one jury strut, one is better than none, but for the price I
would rather have both.
Dan
Message 24
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--> Pietenpol-List message posted by: "Ken & Lisa Rickards" <KL0914@cogeco.ca>
It's the same basic airfoil as the Piet, a Clark "Y", uses 1"spars, front &
rear.
Ken
GN1 2992
----- Original Message -----
From: <Isablcorky@aol.com>
Subject: Pietenpol-List: Airfoil
> --> Pietenpol-List message posted by: Isablcorky@aol.com
>
> Pieters,
> Would some GNer please tell me what kind of airfoil the GN plan calls for.
> Thanks
> Corky in La
>
>
Message 25
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| Subject: | Re: my feeelings on dihedral |
--> Pietenpol-List message posted by: "Graham Hansen" <grhans@cable-lynx.net>
Chris Bobka,
Further to your treatise on dihedral, this is what an old aeronautical
engineering
book of mine says:
"...the High Wing or Parasol type of monoplane, which often has no Dihedral
Angle. The Low Wing Monoplane, on the other hand, must usually have a
Dihedral Angle."
Ref. MECHANICS OF FLIGHT by A. C. Kermode
London
Sir Isaac Pitman & Sons, Ltd. 1942
Kermode essentially says what you are saying: a parasol monoplane such as
the Pietenpol needs no dihedral for adequate lateral stability. (In spite of
this
I did incorporate a modicum of dihedral in my Pietenpol, mainly to reduce
the "droopy" look while parked.)
The other day I obtained a brochure on the new Murphy JDM 8 which in-
cluded a basic 3-view layout showing zero dihedral! Since this airplane has
a low wing, it seems strange that they went this route. It strongly reminds
me
of the Druine Turbulent (a delightful little plane) I test flew for a friend
years
ago, but the Turbulent had dihedral typical of low wing monoplanes. I know
of several low wingers with no dihedral, but some were not all that success-
ful.
Back in the 1980's a fellow from British Columbia built a low wing Pietenpol
powered by a Continental A-65. It had strut braced wings with appropriate
dihedral for this configuration. It flew successfully, but had a high sink
rate.
He cited easy access to the cockpits and good visibility as the chief
benefits.
Graham Hansen (Pietenpol CF-AUN) in sunny Alberta, Canada.
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