Math Question

Ok Guys and Gals,
I do not remember the formula for this to save my life, so I will see if
yall can come up with it. Yes I did check on the web, but did not see the
formula I need.
I want to figure the volume of a gas tank that will not be round or
square, It will have five sides and then the two ends of the tank. With one
end being larger than the other. I would give exact measurements , but being
as I don't know what they will be yet I can't:} I need to find the right
volume in order to get the right measurement . Oh the dilemma !
Be gentle math wizards it's been 25 years since I have had to do this!


--
Patrick Dixon
student SPL
aircraft structural mech

sounds like you will need to just fill the tank and measure the output.

Dave

W P Dixon wrote:
Ok Guys and Gals,
I do not remember the formula for this to save my life, so I will see
if yall can come up with it. Yes I did check on the web, but did not see
the formula I need.
I want to figure the volume of a gas tank that will not be round or
square, It will have five sides and then the two ends of the tank. With
one end being larger than the other. I would give exact measurements ,
but being as I don't know what they will be yet I can't:} I need to find
the right volume in order to get the right measurement . Oh the dilemma !
Be gentle math wizards it's been 25 years since I have had to do
this!

W P Dixon wrote:

Ok Guys and Gals,
I do not remember the formula for this to save my life, so I will see
if yall can come up with it. Yes I did check on the web, but did not see
the formula I need.
I want to figure the volume of a gas tank that will not be round or
square, It will have five sides and then the two ends of the tank. With
one end being larger than the other. I would give exact measurements ,
but being as I don't know what they will be yet I can't:} I need to find
the right volume in order to get the right measurement . Oh the dilemma !
Be gentle math wizards it's been 25 years since I have had to do
this!


Depending on how irregular the tank shape is, you may have to solve this
using numerical integration. However, if the tank shape is the same in
at least one axis (say z or vertical), then figure the area of the shape
in the x-y plane and then simply multiply times the height, z, and
equate that to the volume you desire. Then solve for z.


Matt

Matt Whiting wrote:

W P Dixon wrote:

Ok Guys and Gals,
I do not remember the formula for this to save my life, so I will
see if yall can come up with it. Yes I did check on the web, but did
not see the formula I need.
I want to figure the volume of a gas tank that will not be round or
square, It will have five sides and then the two ends of the tank.
With one end being larger than the other. I would give exact
measurements , but being as I don't know what they will be yet I
can't:} I need to find the right volume in order to get the right
measurement . Oh the dilemma !
Be gentle math wizards it's been 25 years since I have had to do
this!


Depending on how irregular the tank shape is, you may have to solve this
using numerical integration. However, if the tank shape is the same in
at least one axis (say z or vertical), then figure the area of the shape
in the x-y plane and then simply multiply times the height, z, and
equate that to the volume you desire. Then solve for z.


Matt

That would work if it had the same cross sectional area along Z. He says
otherwise. This leaves to 3 solutions: 1) build it, fill it and measure
the volume coming out, 2) calculus which would be quickest and easiest
or 3) draw a diagram, cut it into solids you can calculate, then add up
the volume of the solids.

If the small end isn't very much smaller than the big end go ahead and
do it Matt's way and add a fudge factor.

Dan, U.S. Air Force, retired

Hee Hee,
No simple answer huh? Thanks guys, I looked more on the web late last
night and I do think I will have to make the shapes into smaller measureable
shapes and add the totals. I do think figuring up something before you
actually build it is alot cheaper,...you don't have to build it but once.
Well we all hope anyway!
Also planning to build a set of floats and that's where the volume
formulas really get funky. I would sure hate to spend a grand just to fill
it with water and say, well not right can't use it. Heck my old lady would
kill me if I wasted 200 bucks on a ruined gas tank! HAHA
It won't be to bad figuring it all up "cutting it into basic shapes" ,
just will take some time. For the gas tank, it will be in a VP-1. I am
welding aluminum instead of using the fiberglass. An old high school buddy,
certified nuclear welder is going to weld it up for me. So I need to send
him a drawing of it, thus the need for getting it right. That math stuff is
pretty cool when you can remember the formulas ain't it? So for the gas
tank, I just wanted to see how much fuel a aluminum tank would hold with
alittle mod. But the floats , I definitely have to know the volumes of each
compartment before I even think of starting the build there.

Patrick
student SPL
aircraft structural mech

W P Dixon wrote:
Also planning to build a set of floats and that's where the volume
formulas really get funky.

I just got my seaplane rating. I spent some time looking at the floats
-- it looks like the only way I could calculate the volume of the floats
I was looking at would be a double-integral. Elegant, but could still
be tricky.

One thing to keep in mind is the place where the float will contact the
water at various attitudes. If the contact-point is too far forward
(either because of the attitude of the aircraft or because of the design
of the float), you're flying a taildragger in a soft-sticky-massive
substance that is many times more dense than air... Scary!

Also, floats a have many effects on the aerodynamics of the aircraft.
The side area of the craft is different when it has floats -- a lot more
aerodynamic stuff happening in front of the CG, which can require a
bigger rudder. Also, the instructor told me that in a plow turn, the
change in the amount of the float exposed to the wind was one of the
things that makes the aircraft turn downwing. Lastly, the mass of the
floats would probably change the CG around a bit too.

-Luke

W P Dixon wrote:

Hee Hee,
No simple answer huh? Thanks guys, I looked more on the web late
last night and I do think I will have to make the shapes into smaller
measureable shapes and add the totals. I do think figuring up something
before you actually build it is alot cheaper,...you don't have to build
it but once. Well we all hope anyway!
Also planning to build a set of floats and that's where the volume
formulas really get funky. I would sure hate to spend a grand just to
fill it with water and say, well not right can't use it. Heck my old
lady would kill me if I wasted 200 bucks on a ruined gas tank! HAHA
It won't be to bad figuring it all up "cutting it into basic shapes"
, just will take some time. For the gas tank, it will be in a VP-1. I am
welding aluminum instead of using the fiberglass. An old high school
buddy, certified nuclear welder is going to weld it up for me. So I need
to send him a drawing of it, thus the need for getting it right. That
math stuff is pretty cool when you can remember the formulas ain't it?
So for the gas tank, I just wanted to see how much fuel a aluminum
tank would hold with alittle mod. But the floats , I definitely have to
know the volumes of each compartment before I even think of starting the
build there.

Patrick
student SPL
aircraft structural mech

Nothing says you have to build a full size model. Make a fiberglass
model at 1/8 to 1/4 the size you SWAG, fill it with water and measure it
out. You can now scale as needed mathematically.

Don't forget to take into consideration material thickness, baffle
thickness etc as you plan.

Dan, U.S. Air Force, retired

Now that may not be a bad idea, and it would be pretty cool to build a RC
plane to go on top too! Dang Dan now I have to build another toy!!!!! My
wife is gonna shoot me for sure!
Seriously , that is not a bad idea, may just do that. Will check out the
math stuff first. If it befuddles me to bad I may have to resort to a plan
B, or Plan Dan!

Patrick
student SPL
aircraft structural mech

"Dan, U.S. Air Force, retired" wrote in message
news:LHOce.1573$aB.391@lakeread03...
W P Dixon wrote:

Hee Hee,
No simple answer huh? Thanks guys, I looked more on the web late last
night and I do think I will have to make the shapes into smaller
measureable shapes and add the totals. I do think figuring up something
before you actually build it is alot cheaper,...you don't have to build
it but once. Well we all hope anyway!
Also planning to build a set of floats and that's where the volume
formulas really get funky. I would sure hate to spend a grand just to
fill it with water and say, well not right can't use it. Heck my old lady
would kill me if I wasted 200 bucks on a ruined gas tank! HAHA
It won't be to bad figuring it all up "cutting it into basic shapes" ,
just will take some time. For the gas tank, it will be in a VP-1. I am
welding aluminum instead of using the fiberglass. An old high school
buddy, certified nuclear welder is going to weld it up for me. So I need
to send him a drawing of it, thus the need for getting it right. That
math stuff is pretty cool when you can remember the formulas ain't it?
So for the gas tank, I just wanted to see how much fuel a aluminum tank
would hold with alittle mod. But the floats , I definitely have to know
the volumes of each compartment before I even think of starting the build
there.

Patrick
student SPL
aircraft structural mech

Nothing says you have to build a full size model. Make a fiberglass model
at 1/8 to 1/4 the size you SWAG, fill it with water and measure it out.
You can now scale as needed mathematically.

Don't forget to take into consideration material thickness, baffle
thickness etc as you plan.

Dan, U.S. Air Force, retired

"W P Dixon" wrote

.. For the gas tank, it will be in a VP-1. I am
welding aluminum instead of using the fiberglass. An old high school
buddy,
certified nuclear welder is going to weld it up for me.

Why not make it round on the ends, and just wrap it, instead of having flat
sides? Less welds to leak. That is, if you are welding each flat to the
other. If you are going continuous, nevermind! g
--
Jim in NC

Jim,
If I were welding it, it wouldn't be welded!!! HAHA It would be riveted
and sloshed. However the fellow that will be doing the welding welds at
nuclear facilities and has an xray certification. I know his work very well,
and it won't leak.

Patrick
student SPL
aircraft structural mech
"Morgans" wrote in message
...

"W P Dixon" wrote

. For the gas tank, it will be in a VP-1. I am
welding aluminum instead of using the fiberglass. An old high school
buddy,
certified nuclear welder is going to weld it up for me.

Why not make it round on the ends, and just wrap it, instead of having
flat
sides? Less welds to leak. That is, if you are welding each flat to the
other. If you are going continuous, nevermind! g
--
Jim in NC