Today's Message Index:
----------------------
1. 05:59 AM - Re: Tippiness (Gary Boothe)
2. 05:59 AM - Re: Tippiness (Gary Boothe)
3. 02:55 PM - Re: Attaching ribs to spars question (John Francis)
4. 03:01 PM - Re: Re: Attaching ribs to spars question (Gary Boothe)
5. 03:14 PM - Re: Re: Attaching ribs to spars question (Gary Boothe)
6. 03:36 PM - Re: Re: Attaching ribs to spars question (Lion Mason)
7. 03:36 PM - Re: Attaching ribs to spars question (John Francis)
8. 03:51 PM - Re: Re: Attaching ribs to spars question (Gary Boothe)
9. 06:36 PM - Re: Tippiness (jarheadpilot82)
10. 07:43 PM - Re: Tippiness (tools)
11. 09:29 PM - Re: Re: Tippiness (Ken Bickers)
12. 10:58 PM - Re: Tippiness (jarheadpilot82)
Message 1
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Nicely done, Ken. I live on 'precise estimates!' J
Gary Boothe
NX308MB
From: owner-pietenpol-list-server@matronics.com
[mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Ken Bickers
Sent: Tuesday, June 11, 2013 10:54 AM
Subject: Pietenpol-List: Tippiness
Guys,
This past weekend, I was discussing the question of potential tippiness of
parasol winged airplanes with a flying buddy of mine who happens to be a
physicist at the University of Colorado.
The question I posed was how could we estimate the location of the center of
gravity in the vertical dimension, based on doing weight and balance
calculations. Knowing that location would allow for precise estimates of
the relative tippiness of different airplanes.
He thought this would make a great homework question for his undergraduates.
He sent me the solution, which I've attached for you.
To do the math, you'll need to do weight and balance measurements with the
fuselage in at least two different orientations. The easiest would be one
while the plane rests on the landing gear and one with the tail elevated to
make the top longeron level with the ground. Key here is that you'll need
to measure the change in angle at the top longeron, using an angle finder
that you can buy at any hardware store.
After that you just need to plug values into a calculator that can take
sines and cosines using the formula that is in the attached document. The
one you want is the one marked (4).
One more thing. I'd suggest loading the cockpits and fuel tank with normal
weights that would be seen on takeoff or landing, as this will affect the
vertical center of gravity just as surely as it will affect the longitudinal
center of gravity in any standard weight and balance calculation.
Cheers, Ken
Message 2
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Nicely done, Ken. I live on 'precise estimates!' J
Gary Boothe
NX308MB
From: owner-pietenpol-list-server@matronics.com
[mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Ken Bickers
Sent: Tuesday, June 11, 2013 10:54 AM
Subject: Pietenpol-List: Tippiness
Guys,
This past weekend, I was discussing the question of potential tippiness of
parasol winged airplanes with a flying buddy of mine who happens to be a
physicist at the University of Colorado.
The question I posed was how could we estimate the location of the center of
gravity in the vertical dimension, based on doing weight and balance
calculations. Knowing that location would allow for precise estimates of
the relative tippiness of different airplanes.
He thought this would make a great homework question for his undergraduates.
He sent me the solution, which I've attached for you.
To do the math, you'll need to do weight and balance measurements with the
fuselage in at least two different orientations. The easiest would be one
while the plane rests on the landing gear and one with the tail elevated to
make the top longeron level with the ground. Key here is that you'll need
to measure the change in angle at the top longeron, using an angle finder
that you can buy at any hardware store.
After that you just need to plug values into a calculator that can take
sines and cosines using the formula that is in the attached document. The
one you want is the one marked (4).
One more thing. I'd suggest loading the cockpits and fuel tank with normal
weights that would be seen on takeoff or landing, as this will affect the
vertical center of gravity just as surely as it will affect the longitudinal
center of gravity in any standard weight and balance calculation.
Cheers, Ken
Message 3
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Subject: | Re: Attaching ribs to spars question |
[quote="gboothe"]Once covered and stitched, those ribs ain't goin' nowhere! My
spar replace project got infinitely easier without glued ribs!!
Gary,
But maybe that spar wouldn't of broken if the ribs were glued to it???
Just saying.....
--------
John Francis
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=402568#402568
Message 4
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Subject: | Re: Attaching ribs to spars question |
Don't see how they would add any strength. They did not move, and they did not
break. I don't know, but I think slapping 1,000 lbs of aircraft down on one spar
was the culprit! ;-)
Gary
Sent from my iPhone
On Jun 12, 2013, at 2:54 PM, "John Francis" <Mrkringles@msn.com> wrote:
>
> [quote="gboothe"]Once covered and stitched, those ribs ain't goin' nowhere! My
spar replace project got infinitely easier without glued ribs!!
>
> Gary,
>
> But maybe that spar wouldn't of broken if the ribs were glued to it???
> Just saying.....
>
> --------
> John Francis
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=402568#402568
>
>
>
>
>
>
>
>
>
>
Message 5
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Subject: | Re: Attaching ribs to spars question |
That came out a little harsh...sorry John!
What I really mean to say is that, after completing and flying my plane, I am amazed
by how little I know. If someone can explain how fastening the ribs to the
spar will increase strength...I'm all ears!
Gary
Sent from my iPhone
On Jun 12, 2013, at 3:01 PM, Gary Boothe <gboothe5@comcast.net> wrote:
>
> Don't see how they would add any strength. They did not move, and they did not
break. I don't know, but I think slapping 1,000 lbs of aircraft down on one
spar was the culprit! ;-)
>
> Gary
>
> Sent from my iPhone
>
> On Jun 12, 2013, at 2:54 PM, "John Francis" <Mrkringles@msn.com> wrote:
>
>>
>> [quote="gboothe"]Once covered and stitched, those ribs ain't goin' nowhere!
My spar replace project got infinitely easier without glued ribs!!
>>
>> Gary,
>>
>> But maybe that spar wouldn't of broken if the ribs were glued to it???
>> Just saying.....
>>
>> --------
>> John Francis
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=402568#402568
>
>
>
>
>
Message 6
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Subject: | Re: Attaching ribs to spars question |
I thought that's what rib lacing is for
. Gardiner
Sent from my iPhone
On Jun 12, 2013, at 6:14 PM, Gary Boothe <gboothe5@comcast.net> wrote:
>
> That came out a little harsh...sorry John!
>
> What I really mean to say is that, after completing and flying my plane, I am
amazed by how little I know. If someone can explain how fastening the ribs to
the spar will increase strength...I'm all ears!
>
> Gary
>
> Sent from my iPhone
>
> On Jun 12, 2013, at 3:01 PM, Gary Boothe <gboothe5@comcast.net> wrote:
>
>>
>> Don't see how they would add any strength. They did not move, and they did not
break. I don't know, but I think slapping 1,000 lbs of aircraft down on one
spar was the culprit! ;-)
>>
>> Gary
>>
>> Sent from my iPhone
>>
>> On Jun 12, 2013, at 2:54 PM, "John Francis" <Mrkringles@msn.com> wrote:
>>
>>>
>>> [quote="gboothe"]Once covered and stitched, those ribs ain't goin' nowhere!
My spar replace project got infinitely easier without glued ribs!!
>>>
>>> Gary,
>>>
>>> But maybe that spar wouldn't of broken if the ribs were glued to it???
>>> Just saying.....
>>>
>>> --------
>>> John Francis
>>>
>>>
>>>
>>>
>>> Read this topic online here:
>>>
>>> http://forums.matronics.com/viewtopic.php?p=402568#402568
>
>
>
>
>
Message 7
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Subject: | Re: Attaching ribs to spars question |
Gary, I really have no idea what I'm talking about. How's the rebuild going?
--------
John Francis
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=402572#402572
Message 8
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Subject: | Re: Attaching ribs to spars question |
Slowly. We had just moved, and my wife thinks that un-packing is more important
than fixing airplanes....haven't come up with a good argument! So far, just got
the fabric off...
Gary
Sent from my iPhone
On Jun 12, 2013, at 3:36 PM, "John Francis" <Mrkringles@msn.com> wrote:
>
> Gary, I really have no idea what I'm talking about. How's the rebuild going?
>
> --------
> John Francis
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=402572#402572
>
>
>
>
>
>
>
>
>
>
Message 9
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Ken,
I have only briefly looked at your attachment. My question is this- based on the
formulas you have provided, how will that influence/affect my build?
I am familiar with the concept of a lateral CG when flying helicopters. What do
I do to make this vertical CG a part of my project? I am just not sure I see
the significance.
Thanks for your help on this.
--------
Semper Fi,
Terry Hand
Athens, GA
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=402583#402583
Message 10
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I was wondering at first too, but came up with this...
I imagine nearly ALL our planes will have similar vert cg locations with respect
to, say, the top longeron.
However, the distance of the vert cg to the ground... is going to be quite different.
I suspect what that will tell us is, you're best to keep the location of the vert
CG near where it was originally. OR, if it's gonna be much higher, you might
be better off with a stiffer than average suspension to help maintain control.
I'm now starting to understand rigid gear like a Fly Baby. Probably makes
it a bit tamer on the gear, not necessarily GETTING it on the gear. Seems EVERYTHING
has its compromises.
Quick caveat. MANY of our planes have the wing raised a bit. THAT is gonna change
the vert cg really fast, which will affect ground handling.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=402585#402585
Message 11
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Terry,
The formulas may or may not be of use to you in building your plane.
I was prompted to see if there was a way to identify the CG in the vertical
dimension by the article on Pazmany's thoughts on landing gear design
posted by Chris Tracy on June 6th (re-attached here). Maybe it would be
more accurate to say that I was prompted by Gary's incident dragging a wing
tip. One of the key variables in the design of landing gears is the
location of the CG vertically. It affects both how far forward or aft to
place the gear (especially on tail wheel airplanes) and how wide to make
the wheel base.
As all of us make decisions about where to locate fuel tanks (nose or
center section or both), lengthening cabane struts, sticking to the wheel
base called out in the original plans or widening the wheel base, extending
the motor mount, etc., it is useful to be able to think through the
implications of those decisions. Having the ability to run through
different scenarios using the formula that I forwarded, along with the
Pazmany formulas Chris provided, might lead to better decisions. Or it
might allow for some diagnostics after the fact to figure out why a
particular airplane behaved in a particular way.
Personally, I enjoy stuff like this. For others, mileage may vary.
Cheers, Ken
On Wed, Jun 12, 2013 at 7:36 PM, jarheadpilot82
<jarheadpilot82@hotmail.com>wrote:
> jarheadpilot82@hotmail.com>
>
> Ken,
>
> I have only briefly looked at your attachment. My question is this- based
> on the formulas you have provided, how will that influence/affect my build?
>
> I am familiar with the concept of a lateral CG when flying helicopters.
> What do I do to make this vertical CG a part of my project? I am just not
> sure I see the significance.
>
> Thanks for your help on this.
>
> --------
> Semper Fi,
>
> Terry Hand
> Athens, GA
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=402583#402583
>
>
Message 12
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Ken,
Thanks for uploading the Forum paper about landing gear design.
The last paragraph on page 1 gave me what I was looking for-
"On a front view, the angle between vertical and a line from CG to point of wheel
contact with ground should not be less than 25 degrees."
That is what I was looking for. With so many differing dimensions of gear width
that have been mentioned, I agree that some guidance needs to be published, and
this article gives it. My question pertained to the usefulness of the information,
and this article does put it to use. Thanks for bringing that out.
I guess the Grumman engineers slept through the landing gear design class in college
when they designed the gear on the F4F Wildcat!
--------
Semper Fi,
Terry Hand
Athens, GA
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=402593#402593
Attachments:
http://forums.matronics.com//files/f4f_4a_145.jpg
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