Matronics Email Lists Forum Index Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
 
 Get Email Distribution Too!Get Email Distribution Too!    FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

W&B Configuration

 
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> RV10-List
View previous topic :: View next topic  
Author Message
philperry9



Joined: 23 Nov 2011
Posts: 379

PostPosted: Sun Mar 26, 2017 6:08 pm    Post subject: W&B Configuration Reply with quote

I'm about to zero in on having this thing on the scales in the next couple of days.

Reading the FAA circular, they mention that the sumo should be full. (12 Qts in my case). Vans Section 5 is a little more vague.

I have a hard time seeing myself ever filling the sump with 12, just to watch it get pumped right overboard and settle in around 8-9 on the stick.

What have you all done with regards to sump capacity when running your W&B? I'm tempted to run it with full lines and 8 on the stick.

But I'm just curious to know what most of you have done with yours?

Sent from my iPhone


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
View user's profile Send private message
rv10flyer(at)live.com
Guest





PostPosted: Sun Mar 26, 2017 6:26 pm    Post subject: W&B Configuration Reply with quote

I thought through how I would fly the plane (aka 8qts) and did the W&B based on that assumption.
--


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
Kellym



Joined: 10 Jan 2006
Posts: 1700
Location: Sun Lakes AZ

PostPosted: Sun Mar 26, 2017 6:33 pm    Post subject: W&B Configuration Reply with quote

Do it on a measured 8 qts. The quantity to full is known. You likely
will run it between 6 and 8 qts, depending on whether you have an
air/oil separator or not.
You can then prepare a separate W&B with full sump.
I also recommend you weigh it with fuel tanks dry, because you won't
know what the exact full quantity is, much less its weight that depends
on temperature.

On 3/26/2017 7:06 PM, Phillip Perry wrote:
Quote:


I'm about to zero in on having this thing on the scales in the next couple of days.

Reading the FAA circular, they mention that the sumo should be full. (12 Qts in my case). Vans Section 5 is a little more vague.

I have a hard time seeing myself ever filling the sump with 12, just to watch it get pumped right overboard and settle in around 8-9 on the stick.

What have you all done with regards to sump capacity when running your W&B? I'm tempted to run it with full lines and 8 on the stick.

But I'm just curious to know what most of you have done with yours?

Sent from my iPhone



- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD
Back to top
View user's profile Send private message
Dave Saylor



Joined: 11 Jan 2015
Posts: 207
Location: GILROY, CA

PostPosted: Sun Mar 26, 2017 7:27 pm    Post subject: W&B Configuration Reply with quote

I do W&Bs in the most common empty configuration.  So I'd weigh it with 8 or 9 qts.

If you want the data for "just in case", weigh it with 8 and then add 2 quarts.  That should be enough to see the weight on a decent scale.  Record all your weights again and you'll have the data to extract the exact arm of the oil.  It's easy on a spreadsheet.
Same goes for pilot, pax, and baggage.  Plop down in the seat while it's still on the scales and you get the most accurate arm for your own self.  Put 50# in the center of the baggage compartment, and you can get that arm too.
Another thing to consider is to make the datum an easy-to-find spot, like the wing leading edge or the instrument panel or the front of the door.  Then when you want to actually measure something important some day, you don't have to mess with some imaginary point out in front of the plane.
--Dave
On Sun, Mar 26, 2017 at 7:06 PM, Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)> wrote:
Quote:
--> RV10-List message posted by: Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)>

I'm about to zero in on having this thing on the scales in the next couple of days.

Reading the FAA circular, they mention that the sumo should be full. (12 Qts in my case).   Vans Section 5 is a little more vague.

I have a hard time seeing myself ever filling the sump with 12, just to watch it get pumped right overboard and settle in around 8-9 on the stick.

What have you all done with regards to sump capacity when running your W&B?  I'm tempted to run it with full lines and 8 on the stick.

But I'm just curious to know what most of you have done with yours?



Sent from my iPhone
====================================
-List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?RV10-List
====================================
FORUMS -
eferrer" target="_blank">http://forums.matronics.com
====================================
WIKI -
errer" target="_blank">http://wiki.matronics.com
====================================
b Site -
          -Matt Dralle, List Admin.
rel="noreferrer" target="_blank">http://www.matronics.com/contribution
====================================





- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
--Dave
KWVI
Back to top
View user's profile Send private message
Lew Gallagher



Joined: 04 Jan 2008
Posts: 402
Location: Greenville , SC

PostPosted: Sun Mar 26, 2017 8:05 pm    Post subject: W&B Configuration Reply with quote

Hey guys,

Just curious here. Did I understand correctly that heating fuel changes the weight ... ?? If so, could someone explain why that would be?

Thanks, – Lew


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
non-pilot
crazy about building
NOW OFICIALLY BUILDER #40549
Fly off completed !
Back to top
View user's profile Send private message Send e-mail
jdriggs49(at)MSN.COM
Guest





PostPosted: Sun Mar 26, 2017 8:25 pm    Post subject: W&B Configuration Reply with quote

When you add heat for all practical purposes it adds mass to the object (liquid fuel).
There is a formula that shows this but since my iPad doesn't do "powers" I won't repeat it here. In actuality the added mass is so small as to be of virtually no easily measurable consequence. Heating causes an easily discerned expansion however.

Sent from my iPad

On Mar 26, 2017, at 11:11 PM, "lewgall(at)charter.net (lewgall(at)charter.net)" <lewgall(at)charter.net (lewgall(at)charter.net)> wrote:


Quote:
Hey guys,
 
Just curious here.  Did I understand correctly that heating fuel changes the weight ... ??  If so, could someone explain why that would be?
 
Thanks, – Lew





- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
Bob Turner



Joined: 03 Jan 2009
Posts: 881
Location: Castro Valley, CA

PostPosted: Sun Mar 26, 2017 8:34 pm    Post subject: Re: W&B Configuration Reply with quote

Lew Gallagher wrote:
Hey guys,

Just curious here. Did I understand correctly that heating fuel changes the weight ... ?? If so, could someone explain why that would be?

Thanks, – Lew


Nearly all materials (water being different) expand when heated. So one gallon of gas at some temperature might weigh exactly 6 pounds. Heat it up, it expands and overflows the container. There is now less (by weight, or number of molecules) gas in the one gallon container. In real life the aluminum fuel tank will also expand, but it's an order of magnitude less than the expansion of the gas. This is one reason jets (that carry huge amounts of gas) usually keep track of the actual weight.
Strictly speaking the statement should be "Heating decreases the density (mass per volume)".


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
Bob Turner
RV-10 QB
Back to top
View user's profile Send private message Send e-mail
Lew Gallagher



Joined: 04 Jan 2008
Posts: 402
Location: Greenville , SC

PostPosted: Mon Mar 27, 2017 4:15 am    Post subject: W&B Configuration Reply with quote

Volume, obviously yes. Weight? Sounds like "Trump science" to me Wink
Keep trying, not sure I believe it yet. Fuel consumption or
expansion/contraction changing COG; changing volume with overflow; density,
I can understand. Maybe that's the deal -- does the expansion with heat
shift the weight, not change the weight? As I said, it doesn't really
matter, just curious.

Later, - Lew

Nearly all materials (water being different) expand when heated. So one
gallon of gas at some temperature might weigh exactly 6 pounds. Heat it up,
it expands and overflows the container. There is now less (by weight, or
number of molecules) gas in the one gallon container. In real life the
aluminum fuel tank will also expand, but it's an order of magnitude less
than the expansion of the gas. This is one reason jets (that carry huge
amounts of gas) usually keep track of the actual weight.

--------
Bob Turner
RV-10 QB


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
non-pilot
crazy about building
NOW OFICIALLY BUILDER #40549
Fly off completed !
Back to top
View user's profile Send private message Send e-mail
Lew Gallagher



Joined: 04 Jan 2008
Posts: 402
Location: Greenville , SC

PostPosted: Mon Mar 27, 2017 4:28 am    Post subject: W&B Configuration Reply with quote

Then there's this: "Water expands about four percent when heated from room
temperature to its boiling point". Hence more issue of rising ocean levels
from global warming of ocean temperature than from melting ice caps.

Never mind, I'm just giddy from South Carolina making it into the Final Four
.. who would have thunk that!!
Do NOT archive.

Later, - Lew
"Nearly all materials (water being different) expand when heated. So one
gallon of gas at some temperature might weigh exactly 6 pounds. Heat it up,
it expands and overflows the container. There is now less (by weight, or
number of molecules) gas in the one gallon container. In real life the
aluminum fuel tank will also expand, but it's an order of magnitude less
than the expansion of the gas. This is one reason jets (that carry huge
amounts of gas) usually keep track of the actual weight."

--------


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
non-pilot
crazy about building
NOW OFICIALLY BUILDER #40549
Fly off completed !
Back to top
View user's profile Send private message Send e-mail
Tim Olson



Joined: 25 Jan 2007
Posts: 2870

PostPosted: Mon Mar 27, 2017 4:54 am    Post subject: W&B Configuration Reply with quote

Don't worry Lew, it's just that many people are better pilots that they are scientists. It is true that the fuel will expand when it is warm. But considering there will be the same number of molecules, they will not weigh differently when they are warm. Yes, the fuel tanks will overflow if they are all the way full to the top, so warm fuel would weigh less in that situation… If it overflowed some of the fuel. But, if you have your fuel tanks filled to 2 inches from the top, on a cold day, and then you take your plane out on a warm day, and the fuel is up to the top, it will not weigh less. It may in fact weigh a minuscule amount more, due to additional dissolved gases. The comment about Jets calculating fuel in pounds is accurate, but that would not simply be because fuel weighs less when it is warm. It would have more to do with that it has less volume when it is warm , for the same given amount of fuel in molecules. So you are not going crazy.
Either way, the warm fuel versus cold fuel is a small enough number has to be pretty much insignificant when calculating your weight and balance. Sure, it may weigh a few pounds more if you feel to the exact same spot on a cold day as on a warm day, but I don't think a weight and balance needs to be calculated to that Precision.
Tim

Quote:
On Mar 27, 2017, at 7:14 AM, <lewgall(at)charter.net> <lewgall(at)charter.net> wrote:



Volume, obviously yes. Weight? Sounds like "Trump science" to me Wink Keep trying, not sure I believe it yet. Fuel consumption or expansion/contraction changing COG; changing volume with overflow; density, I can understand. Maybe that's the deal -- does the expansion with heat shift the weight, not change the weight? As I said, it doesn't really matter, just curious.

Later, - Lew



Nearly all materials (water being different) expand when heated. So one gallon of gas at some temperature might weigh exactly 6 pounds. Heat it up, it expands and overflows the container. There is now less (by weight, or number of molecules) gas in the one gallon container. In real life the aluminum fuel tank will also expand, but it's an order of magnitude less than the expansion of the gas. This is one reason jets (that carry huge amounts of gas) usually keep track of the actual weight.

--------
Bob Turner
RV-10 QB











- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
View user's profile Send private message Send e-mail
Kellym



Joined: 10 Jan 2006
Posts: 1700
Location: Sun Lakes AZ

PostPosted: Mon Mar 27, 2017 6:10 am    Post subject: W&B Configuration Reply with quote

The weight per gallon of avgas varies approx. 0.1% per degree C.
So at 15C it is 6.01 lbs per gal. At -40 it is 6.41 lbs/gal, and at 35C
it is around 5.88 lb/gal. A swing of .53 lbs/gal. That would be
somewhere in the 32 lb range for full tanks. Yes, it is mostly very
close to the C.G. I wouldn't call it insignificant. Yes, the difference
between 10 and 30 C is around a 2% change, not big. Then you have
difference between individual tanks that may be a gallon or two, for
another 12 lb difference.
However, why worry about it when it is easy to weigh the plane with
tanks empty?
I don't advocate calculating weight to a couple decimals, nor c.g. by
more than about 1 decimal, but you should be aware that if you are
fueling in Phoenix in the summer, that 120 lbs of baggage will affect
c.g. more than it will at International Falls in Jan.

On 3/27/2017 5:53 AM, Tim Olson wrote:
Quote:

C.G.
Don't worry Lew, it's just that many people are better pilots that they are scientists. It is true that the fuel will expand when it is warm. But considering there will be the same number of molecules, they will not weigh differently when they are warm. Yes, the fuel tanks will overflow if they are all the way full to the top, so warm fuel would weigh less in that situation… If it overflowed some of the fuel. But, if you have your fuel tanks filled to 2 inches from the top, on a cold day, and then you take your plane out on a warm day, and the fuel is up to the top, it will not weigh less. It may in fact weigh a minuscule amount more, due to additional dissolved gases. The comment about Jets calculating fuel in pounds is accurate, but that would not simply be because fuel weighs less when it is warm. It would have more to do with that it has less volume when it is warm , for the same given amount of fuel in molecules. So you are not going crazy.
Either way, the warm fuel versus cold fuel is a small enough number has to be pretty much insignificant when calculating your weight and balance. Sure, it may weigh a few pounds more if you feel to the exact same spot on a cold day as on a warm day, but I don't think a weight and balance needs to be calculated to that Precision.
Tim


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD
Back to top
View user's profile Send private message
Tim Olson



Joined: 25 Jan 2007
Posts: 2870

PostPosted: Mon Mar 27, 2017 6:52 am    Post subject: W&B Configuration Reply with quote

As long as you understand that nearly the entire reason that
the fuel has a different "weight" per gallon is that the
actual QUANTITY of fuel molecules in that gallon is less
as it gets warmer, then you're right on. It's a VOLUME
issue, not a weight issue. If you took hot fuel
of a given weight, and cold fuel of a given weight, and
brought them to the same temperature, they would still
weigh the same but have different VOLUMES.

And, I will say that I do consider it to be pretty irrelevant
regarding the weight of fuel, despite the 32lbs of
difference. The reason I say it's irrelevant is because
I know of no person who flies small planes like RV's, who
would calculate their W&B for a given day of flying and
actually compensate for the weight of fuel THAT DAY
based on temperature.

But you're right, just weigh it with the tanks empty, or
if you wish, after adding some fuel and draining everything
but the unusable fuel. In the RV-10/14 the unusable fuel
is also such a small quantity that it really isn't a significant
number for practical purposes. I have flown my tanks to
dry in testing and there is about 1 cup, 2 max, left
in the tank when flown to empty.

So my personal summary is: The weight difference of fuel
is not significant in PRACTICAL terms for anything,
AFTER you have done an accurate airplane weighing. You're
not likely to ever need to consider that added or
decreased weight due to temperature when planning any
flight. And, for practical purposes, in the RV-10/14
models, useable fuel = total fuel, so you don't need to
mark your tanks with a label like "60 Gallons, 59 usable"
or anything like that.

I personally have never, other than during fuel tank
capacity testing, ever flown with less than 5 gallons in
a tank. I think the risk of fuel unporting during
turns in the pattern would be too high if you get much
lower than that.

And, I think weighing with tanks empty is the way to go.

Tim
On 03/27/2017 09:08 AM, Kelly McMullen wrote:
Quote:


The weight per gallon of avgas varies approx. 0.1% per degree C.
So at 15C it is 6.01 lbs per gal. At -40 it is 6.41 lbs/gal, and at 35C
it is around 5.88 lb/gal. A swing of .53 lbs/gal. That would be
somewhere in the 32 lb range for full tanks. Yes, it is mostly very
close to the C.G. I wouldn't call it insignificant. Yes, the difference
between 10 and 30 C is around a 2% change, not big. Then you have
difference between individual tanks that may be a gallon or two, for
another 12 lb difference.
However, why worry about it when it is easy to weigh the plane with
tanks empty?
I don't advocate calculating weight to a couple decimals, nor c.g. by
more than about 1 decimal, but you should be aware that if you are
fueling in Phoenix in the summer, that 120 lbs of baggage will affect
c.g. more than it will at International Falls in Jan.

On 3/27/2017 5:53 AM, Tim Olson wrote:
>
> C.G.
> Don't worry Lew, it's just that many people are better pilots that
> they are scientists. It is true that the fuel will expand when it is
> warm. But considering there will be the same number of molecules, they
> will not weigh differently when they are warm. Yes, the fuel tanks
> will overflow if they are all the way full to the top, so warm fuel
> would weigh less in that situation… If it overflowed some of the fuel.
> But, if you have your fuel tanks filled to 2 inches from the top, on a
> cold day, and then you take your plane out on a warm day, and the fuel
> is up to the top, it will not weigh less. It may in fact weigh a
> minuscule amount more, due to additional dissolved gases. The comment
> about Jets calculating fuel in pounds is accurate, but that would not
> simply be because fuel weighs less when it is warm. It would have more
> to do with that it has less volume when it is warm , for the same
> given amount of fuel in molecules. So you are not going crazy.
> Either way, the warm fuel versus cold fuel is a small enough number
> has to be pretty much insignificant when calculating your weight and
> balance. Sure, it may weigh a few pounds more if you feel to the exact
> same spot on a cold day as on a warm day, but I don't think a weight
> and balance needs to be calculated to that Precision.
> Tim


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
View user's profile Send private message Send e-mail
jesse(at)saintaviation.co
Guest





PostPosted: Mon Mar 27, 2017 7:23 am    Post subject: W&B Configuration Reply with quote

This whole discussion cracks me up. The weighing issue is that you have to do it with empty tanks or full tanks. That's the point made that started the expansion of fuel when heated discussion. If you use full tanks, the plane is lighter if the fuel is warm because it's bigger. If you fill it up with cold fuel and it warms up, the expansion will send fuel out the vents onto the ground, making the plane lighter. At half tanks it makes no difference in weight, but you can't weigh at half tanks because you don't know exactly how much fuel you have to calculate it back out for an accurate empty weight.

The actual best way to get empty weight is to disconnect the fuel line at the engine and pump it out, leaving the unusable fuel in the tanks.

Jesse Saint
Saint Aviation, Inc.
jesse(at)saintaviation.com
C: 352-427-0285
F: 815-377-3694

Sent from my iPhone

Quote:
On Mar 27, 2017, at 8:14 AM, <lewgall(at)charter.net> <lewgall(at)charter.net> wrote:



Volume, obviously yes. Weight? Sounds like "Trump science" to me Wink Keep trying, not sure I believe it yet. Fuel consumption or expansion/contraction changing COG; changing volume with overflow; density, I can understand. Maybe that's the deal -- does the expansion with heat shift the weight, not change the weight? As I said, it doesn't really matter, just curious.

Later, - Lew



Nearly all materials (water being different) expand when heated. So one gallon of gas at some temperature might weigh exactly 6 pounds. Heat it up, it expands and overflows the container. There is now less (by weight, or number of molecules) gas in the one gallon container. In real life the aluminum fuel tank will also expand, but it's an order of magnitude less than the expansion of the gas. This is one reason jets (that carry huge amounts of gas) usually keep track of the actual weight.

--------
Bob Turner
RV-10 QB











- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
flyboy(at)gmail.com
Guest





PostPosted: Mon Mar 27, 2017 7:26 am    Post subject: W&B Configuration Reply with quote

On Mon, Mar 27, 2017 at 8:43 AM, Tim Olson <Tim(at)myrv10.com (Tim(at)myrv10.com)> wrote:
Quote:
--> RV10-List message posted by: Tim Olson <Tim(at)MyRV10.com>

As long as you understand that nearly the entire reason that
the fuel has a different "weight" per gallon is that the
actual QUANTITY of fuel molecules in that gallon is less
as it gets warmer, then you're right on.  It's a VOLUME
issue, not a weight issue.   If you took hot fuel
of a given weight, and cold fuel of a given weight, and
brought them to the same temperature, they would still
weigh the same but have different VOLUMES.


Uhm, no.  If you take a pound of cold fuel and pound of hot fuel, they're going to have the same volume *and* weight once you equalize the temperature.  This is one of the many reasons we fuel airliners by weight.


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
rv10pro(at)gmail.com
Guest





PostPosted: Mon Mar 27, 2017 7:31 am    Post subject: W&B Configuration Reply with quote

On the long cross country flights from the West Coast to AirVenture I would swear the bugs get bigger and their weight becomes a factor as we approach Wisconsin.
Will need to tweak my W&B formula.
John 
On Mon, Mar 27, 2017 at 7:43 AM, Tim Olson <Tim(at)myrv10.com (Tim(at)myrv10.com)> wrote:
Quote:
--> RV10-List message posted by: Tim Olson <Tim(at)MyRV10.com>

As long as you understand that nearly the entire reason that
the fuel has a different "weight" per gallon is that the
actual QUANTITY of fuel molecules in that gallon is less
as it gets warmer, then you're right on.  It's a VOLUME
issue, not a weight issue.   If you took hot fuel
of a given weight, and cold fuel of a given weight, and
brought them to the same temperature, they would still
weigh the same but have different VOLUMES.

And, I will say that I do consider it to be pretty irrelevant
regarding the weight of fuel, despite the 32lbs of
difference.  The reason I say it's irrelevant is because
I know of no person who flies small planes like RV's, who
would calculate their W&B for a given day of flying and
actually compensate for the weight of fuel THAT DAY
based on temperature.

But you're right, just weigh it with the tanks empty, or
if you wish, after adding some fuel and draining everything
but the unusable fuel.  In the RV-10/14 the unusable fuel
is also such a small quantity that it really isn't a significant
number for practical purposes.  I have flown my tanks to
dry in testing and there is about 1 cup, 2 max, left
in the tank when flown to empty.

So my personal summary is:  The weight difference of fuel
is not significant in PRACTICAL terms for anything,
AFTER you have done an accurate airplane weighing.  You're
not likely to ever need to consider that added or
decreased weight due to temperature when planning any
flight.  And, for practical purposes, in the RV-10/14
models, useable fuel = total fuel, so you don't need to
mark your tanks with a label like "60 Gallons, 59 usable"
or anything like that.

I personally have never, other than during fuel tank
capacity testing, ever flown with less than 5 gallons in
a tank.  I think the risk of fuel unporting during
turns in the pattern would be too high if you get much
lower than that.

And, I think weighing with tanks empty is the way to go.

Tim


On 03/27/2017 09:08 AM, Kelly McMullen wrote:
Quote:
--> RV10-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>

The weight per gallon of avgas varies approx. 0.1% per degree C.
So at 15C it is 6.01 lbs per gal. At -40 it is 6.41 lbs/gal, and at 35C
it is around 5.88 lb/gal. A swing of .53 lbs/gal. That would be
somewhere in the 32 lb range for full tanks. Yes, it is mostly very
close to the C.G. I wouldn't call it insignificant. Yes, the difference
between 10 and 30 C is around a 2% change, not big. Then you have
difference between individual tanks that may be a gallon or two, for
another 12 lb difference.
However, why worry about it when it is easy to weigh the plane with
tanks empty?
I don't advocate calculating weight to a couple decimals, nor c.g. by
more than about 1 decimal, but you should be aware that if you are
fueling in Phoenix in the summer, that 120 lbs of baggage will affect
c.g. more than it will at International Falls in Jan.

On 3/27/2017 5:53 AM, Tim Olson wrote:
Quote:
--> RV10-List message posted by: Tim Olson <Tim(at)MyRV10.com>
C.G.
Don't worry Lew, it's just that many people are better pilots that
they are scientists. It is true that the fuel will expand when it is
warm. But considering there will be the same number of molecules, they
will not weigh differently when they are warm.  Yes, the fuel tanks
will overflow if they are all the way full to the top, so warm fuel
would weigh less in that situation… If it overflowed some of the fuel.
But, if you have your fuel tanks filled to 2 inches from the top, on a
cold day, and then you take your plane out on a warm day, and the fuel
is up to the top, it will not weigh less. It may in fact weigh a
minuscule amount more, due to additional dissolved gases.  The comment
about Jets calculating fuel in pounds is accurate, but that would not
simply be because fuel weighs less when it is warm. It would have more
to do with that it has less volume when it is warm , for the same
given amount of fuel in molecules. So you are not going crazy.
Either way, the warm fuel versus cold fuel is a small enough number
has to be pretty much insignificant when calculating your weight and
balance. Sure, it may weigh a few pounds more if you feel to the exact
same spot on a cold day as on a warm day, but I don't think a weight
and balance needs to be calculated to that Precision.
Tim
====================================
-List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?RV10-List
====================================
FORUMS -
eferrer" target="_blank">http://forums.matronics.com
====================================
WIKI -
errer" target="_blank">http://wiki.matronics.com
====================================
b Site -
          -Matt Dralle, List Admin.
rel="noreferrer" target="_blank">http://www.matronics.com/contribution
====================================







- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
rene(at)felker.com
Guest





PostPosted: Mon Mar 27, 2017 7:37 am    Post subject: W&B Configuration Reply with quote

I did mine, full lines and 9 on the stick. I am changing my starter and will
be redoing it in May. I am going to 8 this time. I almost always run
within a Quart of that. Never over 9 and as low as 6 is what I have seen in
my 700 hours.

Rene'
801-721-6080

--


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
rene(at)felker.com
Guest





PostPosted: Mon Mar 27, 2017 7:49 am    Post subject: W&B Configuration Reply with quote

Great idea.

Do not archive.

Rene'
801-721-6080

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Cox
Sent: Monday, March 27, 2017 9:31 AM
To: rv10-list(at)matronics.com
Subject: Re: Re: W&B Configuration

On the long cross country flights from the West Coast to AirVenture I would swear the bugs get bigger and their weight becomes a factor as we approach Wisconsin.



Will need to tweak my W&B formula.



John

On Mon, Mar 27, 2017 at 7:43 AM, Tim Olson <Tim(at)myrv10.com (Tim(at)myrv10.com)> wrote:
Quote:

--> RV10-List message posted by: Tim Olson <Tim(at)MyRV10.com (Tim(at)MyRV10.com)>

As long as you understand that nearly the entire reason that
the fuel has a different "weight" per gallon is that the
actual QUANTITY of fuel molecules in that gallon is less
as it gets warmer, then you're right on. It's a VOLUME
issue, not a weight issue. If you took hot fuel
of a given weight, and cold fuel of a given weight, and
brought them to the same temperature, they would still
weigh the same but have different VOLUMES.

And, I will say that I do consider it to be pretty irrelevant
regarding the weight of fuel, despite the 32lbs of
difference. The reason I say it's irrelevant is because
I know of no person who flies small planes like RV's, who
would calculate their W&B for a given day of flying and
actually compensate for the weight of fuel THAT DAY
based on temperature.

But you're right, just weigh it with the tanks empty, or
if you wish, after adding some fuel and draining everything
but the unusable fuel. In the RV-10/14 the unusable fuel
is also such a small quantity that it really isn't a significant
number for practical purposes. I have flown my tanks to
dry in testing and there is about 1 cup, 2 max, left
in the tank when flown to empty.

So my personal summary is: The weight difference of fuel
is not significant in PRACTICAL terms for anything,
AFTER you have done an accurate airplane weighing. You're
not likely to ever need to consider that added or
decreased weight due to temperature when planning any
flight. And, for practical purposes, in the RV-10/14
models, useable fuel = total fuel, so you don't need to
mark your tanks with a label like "60 Gallons, 59 usable"
or anything like that.

I personally have never, other than during fuel tank
capacity testing, ever flown with less than 5 gallons in
a tank. I think the risk of fuel unporting during
turns in the pattern would be too high if you get much
lower than that.

And, I think weighing with tanks empty is the way to go.

Tim

On 03/27/2017 09:08 AM, Kelly McMullen wrote:
Quote:

--> RV10-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>

The weight per gallon of avgas varies approx. 0.1% per degree C.
So at 15C it is 6.01 lbs per gal. At -40 it is 6.41 lbs/gal, and at 35C
it is around 5.88 lb/gal. A swing of .53 lbs/gal. That would be
somewhere in the 32 lb range for full tanks. Yes, it is mostly very
close to the C.G. I wouldn't call it insignificant. Yes, the difference
between 10 and 30 C is around a 2% change, not big. Then you have
difference between individual tanks that may be a gallon or two, for
another 12 lb difference.
However, why worry about it when it is easy to weigh the plane with
tanks empty?
I don't advocate calculating weight to a couple decimals, nor c.g. by
more than about 1 decimal, but you should be aware that if you are
fueling in Phoenix in the summer, that 120 lbs of baggage will affect
c.g. more than it will at International Falls in Jan.

On 3/27/2017 5:53 AM, Tim Olson wrote:
Quote:

--> RV10-List message posted by: Tim Olson <Tim(at)MyRV10.com (Tim(at)MyRV10.com)>
C.G.
Don't worry Lew, it's just that many people are better pilots that
they are scientists. It is true that the fuel will expand when it is
warm. But considering there will be the same number of molecules, they
will not weigh differently when they are warm. Yes, the fuel tanks
will overflow if they are all the way full to the top, so warm fuel
would weigh less in that situation… If it overflowed some of the fuel.
But, if you have your fuel tanks filled to 2 inches from the top, on a
cold day, and then you take your plane out on a warm day, and the fuel
is up to the top, it will not weigh less. It may in fact weigh a
minuscule amount more, due to additional dissolved gases. The comment
about Jets calculating fuel in pounds is accurate, but that would not
simply be because fuel weighs less when it is warm. It would have more
to do with that it has less volume when it is warm , for the same
given amount of fuel in molecules. So you are not going crazy.
Either way, the warm fuel versus cold fuel is a small enough number
has to be pretty much insignificant when calculating your weight and
balance. Sure, it may weigh a few pounds more if you feel to the exact
same spot on a cold day as on a warm day, but I don't think a weight
and balance needs to be calculated to that Precision.
Tim

====================================
-List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?RV10-List
====================================
FORUMS -
eferrer" target="_blank">http://forums.matronics.com
===========
WIKI -
errer" target="_blank">http://wiki.matronics.com
===========
b Site -
-Matt Dralle, List Admin.
rel="noreferrer" target="_blank">http://www.matronics.com/contribution
====================================




- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
Tim Olson



Joined: 25 Jan 2007
Posts: 2870

PostPosted: Mon Mar 27, 2017 7:50 am    Post subject: W&B Configuration Reply with quote

Hey Berck,

I, like Jesse, am getting a chuckle out of this whole discussion.

I read what you said here, and I think we're basically saying
the same thing. Of course, a pound of fuel hot and a pound
of fuel cold will have the same volume and weight, when
temperature equalizes. I think that is what I was trying
to say, but I just didn't do it eloquently enough. Smile

The weight of the fuel is due to the molecular structure
of the fuel itself having that weight per fuel molecule.
It just happens to be that if you heat things up, the
molecules become further apart and less dense, so the
volume changes. But, a the number of molecules and
weight doesn't change.
Now, if you really want to get a pressure/volume/density
problem that confuses people, try explaining why moist
air is LIGHTER than dry air. Everyone always says stuff
like "the air was so heavy and wet today". The funny
thing is, moist air weighs less than dry air.

That's why the dangerous factors in flying are
"Hot, High, and Humid".... the air is less dense.

If moist air was heavier than dry air, we'd be in
a constant state of ground fog, and clouds wouldn't
be up high in the sky. Wink

Tim

(I think I just caused worse thread creep than original.)
Smile
On 03/27/2017 10:25 AM, Berck E. Nash wrote:
Quote:

On Mon, Mar 27, 2017 at 8:43 AM, Tim Olson <Tim(at)myrv10.com
<mailto:Tim(at)myrv10.com>> wrote:



As long as you understand that nearly the entire reason that
the fuel has a different "weight" per gallon is that the
actual QUANTITY of fuel molecules in that gallon is less
as it gets warmer, then you're right on. It's a VOLUME
issue, not a weight issue. If you took hot fuel
of a given weight, and cold fuel of a given weight, and
brought them to the same temperature, they would still
weigh the same but have different VOLUMES.
Uhm, no. If you take a pound of cold fuel and pound of hot fuel,
they're going to have the same volume *and* weight once you equalize the
temperature. This is one of the many reasons we fuel airliners by weight.


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
View user's profile Send private message Send e-mail
Bob Turner



Joined: 03 Jan 2009
Posts: 881
Location: Castro Valley, CA

PostPosted: Mon Mar 27, 2017 9:16 am    Post subject: Re: more drift Reply with quote

Tim Olson wrote:
Hey Berck,

I, like Jesse, am getting a chuckle out of this whole discussion.
If moist air was heavier than dry air, we'd be in
a constant state of ground fog, and clouds wouldn't
be up high in the sky. Wink

Tim

(I think I just caused worse thread creep than origine]


More thread creep: Moist air doesn't rise because it's moist. In the lower atmosphere there's very good mixing. If that weren't true all the oxygen would be down low, and at higher altitudes it would be all nitrogen. What changes is the amount of water in the vapor state depends on temperature. As the air cools as it rises, you reach the dew point - where no more water can evaporate, so you start having liquid drops.

I thought an early post was referring to Einstein's theory of special relativity: E=mc2(squared). Strictly speaking a sealed container of anything should weigh more as energy (heat) is added. But the speed of light squared is such a big number that you can't measure it under most circumstances.


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
Bob Turner
RV-10 QB
Back to top
View user's profile Send private message Send e-mail
Tim Olson



Joined: 25 Jan 2007
Posts: 2870

PostPosted: Mon Mar 27, 2017 10:14 am    Post subject: W&B Configuration Reply with quote

Thread creep again....water...

It's amazing when you think of the design of things as simple as
water, in our world.

Think of ice...since water hits its greatest density at above
freezing, we can drive on lakes and go ice fishing.
If water followed other molecules pattern, the ice would
form and sink to the bottom of a cold lake, and eventually the
entire lake would turn into a giant ice block.

There are so many things that were designed just perfectly,
that they amaze me all the time.

Tim
do not archive
On 03/27/2017 12:16 PM, Bob Turner wrote:
Quote:

Tim Olson wrote:
> Hey Berck,
>
> I, like Jesse, am getting a chuckle out of this whole discussion.
> If moist air was heavier than dry air, we'd be in
> a constant state of ground fog, and clouds wouldn't
> be up high in the sky. Wink
>
> Tim
>
> (I think I just caused worse thread creep than origine]
More thread creep: Moist air doesn't rise because it's moist. In the lower atmosphere there's very good mixing. If that weren't true all the oxygen would be down low, and at higher altitudes it would be all nitrogen. What changes is the amount of water in the vapor state depends on temperature. As the air cools as it rises, you reach the dew point - where no more water can evaporate, so you start having liquid drops.

I thought an early post was referring to Einstein's theory of special relativity: E=mc2(squared). Strictly speaking a sealed container of anything should weigh more as energy (heat) is added. But the speed of light squared is such a big number that you can't measure it under most circumstances.

--------
Bob Turner
RV-10 QB


Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=467694#467694


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> RV10-List All times are GMT - 8 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Powered by phpBB © 2001, 2005 phpBB Group