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Old Nov 04, 2003, 04:00 AM
Greg
Guest
n/a Posts
Re: Building Light


"jflongworth" <strathboy@execulink.com> wrote in message
news:vqe6a0a2kvso8f@corp.supernews.com...
snip
> I would suggest that engines, mufflers, covering, paint, and undercarriage
>components are far more significant contributors to higher wing loadings
> than "light building techniques".

snip

Excluding the finishing process, these are "fixed" weights and only varied
by choice of engine and radio equipment. The rest is up to the builder.
If you're happy with building a flying brick, more power to ya'. Besides,
you're gonna' need it...more power that is. It sure saves all that needless
exercise picking up pieces when they just stick upon impact, huh? )


Old Nov 04, 2003, 07:00 PM
jflongworth
Guest
n/a Posts
Re: Building Light

Greg, the point I was trying to make was that any excess weight resulting
from the building process is insignificant in terms of wing loading. Even
if one pays no attention to weight saving building techniques, the
additional ounces added are inconsequential in terms of additional wing
loading. For example, is an extra wing load of 1 ounce per square foot
really noticeable in terms of flight characteristics? Not likely, since the
recommended flying weight for my model (as recommended by the manufacturer)
can vary by as much as 16 ounces which I suspect is intended to accommodate
variations in the components that could add weight either as part of the
building process or in the form of accessories such as the engine. I'm not
advocating flying bricks but rather that any weight added through the
building process is not going to have any noticeable effect on flying
characteristics. A more significant weight problem is poor aircraft design
resulting in a nose or tail-heavy condition. It would be interesting to know
just how heavy one could build in terms of wing loading without adversely
affecting the model's flying characteritics. This would be a complicated
calculation bearing in mind the variations in airfoils. I raise this not as
a justification for building heavy but rather for the purpose of adding
heavy items such as cameras. We often hear of full scale accidents where
planes have exceeded the recommended weight, especially on take-off where
the aircraft is only marginally over stall speed.
"Greg" <garnold77@notsohotmail.com> wrote in message
news:1067934441.693542@news.commspeed.net...
>
> "jflongworth" <strathboy@execulink.com> wrote in message
> news:vqe6a0a2kvso8f@corp.supernews.com...
> snip
> > I would suggest that engines, mufflers, covering, paint, and

undercarriage
> >components are far more significant contributors to higher wing loadings
> > than "light building techniques".

> snip
>
> Excluding the finishing process, these are "fixed" weights and only

varied
> by choice of engine and radio equipment. The rest is up to the builder.
> If you're happy with building a flying brick, more power to ya'. Besides,
> you're gonna' need it...more power that is. It sure saves all that

needless
> exercise picking up pieces when they just stick upon impact, huh? )
>
>



Old Nov 04, 2003, 07:01 PM
Paul McIntosh
Guest
n/a Posts
Re: Building Light

Greg, the point he was making was that your use of glues has FAR less effect
on the finished weight of a model than your engine selection or covering
choice. I have been designing and building for 40 years and I agree.

--
Paul McIntosh
Desert Sky Model Aviation
http://fly.mcintoshcentral.com
"Greg" <garnold77@notsohotmail.com> wrote in message
news:1067934441.693542@news.commspeed.net...
>
> "jflongworth" <strathboy@execulink.com> wrote in message
> news:vqe6a0a2kvso8f@corp.supernews.com...
> snip
> > I would suggest that engines, mufflers, covering, paint, and

undercarriage
> >components are far more significant contributors to higher wing loadings
> > than "light building techniques".

> snip
>
> Excluding the finishing process, these are "fixed" weights and only

varied
> by choice of engine and radio equipment. The rest is up to the builder.
> If you're happy with building a flying brick, more power to ya'. Besides,
> you're gonna' need it...more power that is. It sure saves all that

needless
> exercise picking up pieces when they just stick upon impact, huh? )
>
>



Old Nov 05, 2003, 04:00 AM
jnkessler
Guest
n/a Posts
Re: Building Light

overall weight is important, but where the weight is located is more
important.

when I was teaching my son to fly I added 3 ounces of weight to the ends of
the wing tips on a Kadet Lt40 and it really helped minimize the gust effect
on those windy days, although it rolled slower when flying. (The plane was
built light overall).

opinions will vary, jk


Old Nov 06, 2003, 04:00 AM
Brian
Guest
n/a Posts
Re: Building Light



me wrote:
>Building light pays big dividends in the air.


I normally build and fly CL stunt so it's a matter of course to build as
light as possible commensurate with adequate strength. Some time ago I
built an RC model for my son based on my CL stunters. With 865 sq inches
of wing and an Enya 80X it weighed 5.5 pounds and I wasn't trying too
hard to keep the weight down. It flew magnificently, at low throttle and
low rates it was like a trainer but at half throttle or above and high
rates it was a fun fly. But the point is that I built it to FLY as well
as possible, not to survive crashes. There's an article about it that I
wrote for my club web page at http://www.holdfastmac.com.au/kenny1.html

Brian Hampton
Adelaide, South Oz

Old Nov 06, 2003, 07:00 PM
w4jle
Guest
n/a Posts
Re: Building Light

If they enter at the same speed, they will exit at the same time.A heavier
aircraft may require a higher speed in the turn.

With all due respect, your observations are akin to cutting all the legs off
of a frog and telling it to jump. When it fails to do so, you concludes the
frog is deaf...

"Greg" <garnold77@notsohotmail.com> wrote in message
news:1068111787.434764@news.commspeed.net...

> we have both participated...SWRA racing. Two cloned models go into a

turn.
> One weighs 8 pounds and the other 10. Which one will exit the turn first?
> Which one will have the higher loading? It becomes a two-edged sword when
> unnecessary weight is added for the sake of "strength".
>
> While it's true that experience levels will dictate our opinions on this

and
> other aspects of this hobby, 35 years in the hobby have led me to a
> different place than you...not any better or worse, just different.



Old Nov 06, 2003, 07:00 PM
Tom Ivar Helbekkmo
Guest
n/a Posts
Re: Building Light

"w4jle" <W4JLE(remove this to reply)@pbtcomm.net> writes:

>> Two cloned models go into a turn. One weighs 8 pounds and the
>> other 10. Which one will exit the turn first?


> If they enter at the same speed, they will exit at the same time.


Not necessarily. If they enter at the same time, and the ligher
aircraft turns as hard as possible, right on the edge of the stall, it
will definitely exit the turn first. The heavier one will exit later,
and further out, having a larger turn radius, because both reach their
stall angle of attack at the same actual, instantaneous wing loading.

-tih
--
Tom Ivar Helbekkmo, Senior System Administrator, EUnet Norway
www.eunet.no T: +47-22092958 M: +47-93013940 F: +47-22092901
Old Nov 06, 2003, 07:00 PM
John Alt
Guest
n/a Posts
Re: Building Light

Some editing to keep responses in order. Top posting sucks.


> "Greg" <garnold77@notsohotmail.com> wrote in message
> news:1068111787.434764@news.commspeed.net...
>
> > we have both participated...SWRA racing. Two cloned models go into a

> turn.
> > One weighs 8 pounds and the other 10. Which one will exit the turn first?
> > Which one will have the higher loading? It becomes a two-edged sword when
> > unnecessary weight is added for the sake of "strength".


In article <bodjnh$63l3$1@news3.infoave.net>, "w4jle" <W4JLE(remove this
to reply)@pbtcomm.net> says...
> If they enter at the same speed, they will exit at the same time.A heavier
> aircraft may require a higher speed in the turn.


No, the lighter plane will always have an advantage. The heavier
aircraft must generate a higher angle of attack to produce the same
turn. That means more drag. Or get a larger radius turn from the same
AOA. The heavier aircraft is making the same lift, but the g loading is
less.

In the above example, if the 10 pound plane is making an 8 g turn, the 8
pound plane will make a 10 g turn _with the same AOA_ (Angle of Attack).
Both wings would be generating 80 pounds of lift. The lighter plane will
turn a lot tighter at the same control deflection, or need less
deflection to generate the same turn.

Either way, the lighter plane has a big advantage. Note that even
flying straight and level, the lighter plane will be faster. In the
above example, it needs to generate 2 pounds less lift just flying
along, and more lift equals more drag.
Old Nov 06, 2003, 07:00 PM
Greg
Guest
n/a Posts
Re: Building Light


"w4jle" <W4JLE(remove this to reply)@pbtcomm.net> wrote in message
news:bodjnh$63l3$1@news3.infoave.net...

snip

> With all due respect, your observations are akin to cutting all the legs

off
> of a frog and telling it to jump. When it fails to do so, you concludes

the
> frog is deaf...
>

snip

I'm having a hard time finding the slightest bit of respect in your comment,
much less any proof to back your opinion. Therefore, in like manner...

1) I like frogs and wouldn't cut off their legs.
2) Frogs aren't deaf...just some people.

Greg


Old Nov 06, 2003, 07:00 PM
Dan Thomas
Guest
n/a Posts
Re: Building Light

Tom Ivar Helbekkmo <tih+nr@eunetnorge.no> wrote in message news:<86oevpbi70.fsf@athene.i.eunet.no>...
> "w4jle" <W4JLE(remove this to reply)@pbtcomm.net> writes:
>
> >> Two cloned models go into a turn. One weighs 8 pounds and the
> >> other 10. Which one will exit the turn first?

>
> > If they enter at the same speed, they will exit at the same time.

>
> Not necessarily. If they enter at the same time, and the ligher
> aircraft turns as hard as possible, right on the edge of the stall, it
> will definitely exit the turn first. The heavier one will exit later,
> and further out, having a larger turn radius, because both reach their
> stall angle of attack at the same actual, instantaneous wing loading.
>
> -tih


Turn radius is determined by airspeed and bank angle, nothing more.
That applies to everything from models to a 747. Heavier airplanes are
unable to bank steeply if they want to avoid a stall.

Dan
Old Nov 06, 2003, 07:00 PM
w4jle
Guest
n/a Posts
Re: Building Light

Amen Dan, The angle of bank for a standard rate turn in full size aircraft
follows the rule of thumb:
Divide the air speed by 10 and add 50% to it.
i.e.: 100 knots =10 + (1/2 of 10)= 15 degrees.
500 knots = 50 +(1/2 of 50)=75 degrees.

Weight only applies to stalling speed that would be a limiting factor in the
tightest turn possible.
"Dan Thomas" <Dan_Thomas_nospam@yahoo.com> wrote in message
news:43cbd38a.0311061344.6dd88218@posting.google.c om...
> Tom Ivar Helbekkmo <tih+nr@eunetnorge.no> wrote in message

news:<86oevpbi70.fsf@athene.i.eunet.no>...
> > "w4jle" <W4JLE(remove this to reply)@pbtcomm.net> writes:
> >
> > >> Two cloned models go into a turn. One weighs 8 pounds and the
> > >> other 10. Which one will exit the turn first?

> >
> > > If they enter at the same speed, they will exit at the same time.

> >
> > Not necessarily. If they enter at the same time, and the ligher
> > aircraft turns as hard as possible, right on the edge of the stall, it
> > will definitely exit the turn first. The heavier one will exit later,
> > and further out, having a larger turn radius, because both reach their
> > stall angle of attack at the same actual, instantaneous wing loading.
> >
> > -tih

>
> Turn radius is determined by airspeed and bank angle, nothing more.
> That applies to everything from models to a 747. Heavier airplanes are
> unable to bank steeply if they want to avoid a stall.
>
> Dan



Old Nov 07, 2003, 04:00 AM
Tom Ivar Helbekkmo
Guest
n/a Posts
Re: Building Light

I said:

> The heavier one will exit later, and further out, having a larger
> turn radius, because both reach their stall angle of attack at the
> same actual, instantaneous wing loading.


Dan Thomas said:

> Heavier airplanes are unable to bank steeply if they want to avoid a
> stall.


"w4jle" said:

> Weight only applies to stalling speed that would be a limiting
> factor in the tightest turn possible.


OK... That's three ways of saying the same thing. Anyone want to add
to the list? :-)

Getting back to the original problem (two identical planes differing
only in weight entering a pylon turn at the same time), the lighter
one will, as has been explained, exit first. If it turns as tightly
as it can, the heavier one can't follow it. If both planes hold the
same turning radius, the heavier one will be using more of its power
to turn and lift, by suffering more induced drag, and thus lose more
speed in the turn.

The weight difference will be observable in every conceivable
maneuver. You can even deduce it by studying the two planes in
straight and level flight.

-tih
--
Tom Ivar Helbekkmo, Senior System Administrator, EUnet Norway
www.eunet.no T: +47-22092958 M: +47-93013940 F: +47-22092901
Old Nov 07, 2003, 07:00 PM
Greg
Guest
n/a Posts
Re: Building Light


"Tom Ivar Helbekkmo" <tih+nr@eunetnorge.no> wrote in message
news:868ymsbr12.fsf@athene.i.eunet.no...
> I said:
>
> > The heavier one will exit later, and further out, having a larger
> > turn radius, because both reach their stall angle of attack at the
> > same actual, instantaneous wing loading.

>
> Dan Thomas said:
>
> > Heavier airplanes are unable to bank steeply if they want to avoid a
> > stall.

>
> "w4jle" said:
>
> > Weight only applies to stalling speed that would be a limiting
> > factor in the tightest turn possible.

>
> OK... That's three ways of saying the same thing. Anyone want to add
> to the list? :-)


Nope. Pretty much covers it.

>
> Getting back to the original problem (two identical planes differing
> only in weight entering a pylon turn at the same time), the lighter
> one will, as has been explained, exit first. If it turns as tightly
> as it can, the heavier one can't follow it. If both planes hold the
> same turning radius, the heavier one will be using more of its power
> to turn and lift, by suffering more induced drag, and thus lose more
> speed in the turn.
>
> The weight difference will be observable in every conceivable
> maneuver. You can even deduce it by studying the two planes in
> straight and level flight.
>
> -tih
> --
> Tom Ivar Helbekkmo, Senior System Administrator, EUnet Norway
> www.eunet.no T: +47-22092958 M: +47-93013940 F: +47-22092901


And slower to regain the speed once the turn's completed. Good points Tom.

Greg


Old Nov 07, 2003, 07:00 PM
Dan Thomas
Guest
n/a Posts
Re: Building Light

John Alt <JohnAltDoesntneedSpam@charter.net> wrote in message news:<vql2fvm0tfl7ac@corp.supernews.com>...
> Some editing to keep responses in order. Top posting sucks.
>
>
> > "Greg" <garnold77@notsohotmail.com> wrote in message
> > news:1068111787.434764@news.commspeed.net...
> >
> > > we have both participated...SWRA racing. Two cloned models go into a

> turn.
> > > One weighs 8 pounds and the other 10. Which one will exit the turn first?
> > > Which one will have the higher loading? It becomes a two-edged sword when
> > > unnecessary weight is added for the sake of "strength".

>
> In article <bodjnh$63l3$1@news3.infoave.net>, "w4jle" <W4JLE(remove this
> to reply)@pbtcomm.net> says...
> > If they enter at the same speed, they will exit at the same time.A heavier
> > aircraft may require a higher speed in the turn.

>
> No, the lighter plane will always have an advantage. The heavier
> aircraft must generate a higher angle of attack to produce the same
> turn. That means more drag. Or get a larger radius turn from the same
> AOA. The heavier aircraft is making the same lift, but the g loading is
> less.
>
> In the above example, if the 10 pound plane is making an 8 g turn, the 8
> pound plane will make a 10 g turn with the same AOA (Angle of Attack).
> Both wings would be generating 80 pounds of lift. The lighter plane will
> turn a lot tighter at the same control deflection, or need less
> deflection to generate the same turn.


But the same AOA will not do for the heavier airplane as it will
for the light one. The nose will need to be raised further while in
the turn (with the same bank angle) to increase AOA to generate
sufficient lift. Leaving the AOA unchanged will result in a larger
radius caused by a skidding turn, which is uncoordinated flight, and
therefore does not fit the bank/airspeed formula for turn radius. A
skidding turn is also asking for a nasty stall and spin.
A given airspeed/bank angle/turn radius will generate the same G
forces regardless of the airplane's weight or AOA.

> Either way, the lighter plane has a big advantage. Note that even
> flying straight and level, the lighter plane will be faster. In the
> above example, it needs to generate 2 pounds less lift just flying
> along, and more lift equals more drag.


Cruise speed is the one performance parameter least affected by
weight. Weight increases induced drag (drag caused by generating
lift), and induced drag is already at a minimum in cruise. See my
earlier post (#26) in this thread. Having instruments make so many
things clear. Being an instructor of this stuff helps, too.

As far as the general argument goes, lighter is better if you want
good performance. But light must not come at the expense of reasonable
strength or minimal drag.

Dan
Old Nov 07, 2003, 07:00 PM
Dan Thomas
Guest
n/a Posts
Re: Building Light

Dan_Thomas_nospam@yahoo.com (Dan Thomas) wrote in message news:<43cbd38a.0311070725.280ffb2f@posting.google. com>...
> John Alt <JohnAltDoesntneedSpam@charter.net> wrote in message news:<vql2fvm0tfl7ac@corp.supernews.com>...
> > Some editing to keep responses in order. Top posting sucks.
> >
> >
> > > "Greg" <garnold77@notsohotmail.com> wrote in message
> > > news:1068111787.434764@news.commspeed.net...
> > >
> > > > we have both participated...SWRA racing. Two cloned models go into a

> turn.
> > > > One weighs 8 pounds and the other 10. Which one will exit the turn first?
> > > > Which one will have the higher loading? It becomes a two-edged sword when
> > > > unnecessary weight is added for the sake of "strength".

> >
> > In article <bodjnh$63l3$1@news3.infoave.net>, "w4jle" <W4JLE(remove this
> > to reply)@pbtcomm.net> says...
> > > If they enter at the same speed, they will exit at the same time.A heavier
> > > aircraft may require a higher speed in the turn.

> >
> > No, the lighter plane will always have an advantage. The heavier
> > aircraft must generate a higher angle of attack to produce the same
> > turn. That means more drag. Or get a larger radius turn from the same
> > AOA. The heavier aircraft is making the same lift, but the g loading is
> > less.
> >
> > In the above example, if the 10 pound plane is making an 8 g turn, the 8
> > pound plane will make a 10 g turn with the same AOA (Angle of Attack).
> > Both wings would be generating 80 pounds of lift. The lighter plane will
> > turn a lot tighter at the same control deflection, or need less
> > deflection to generate the same turn.

>
> But the same AOA will not do for the heavier airplane as it will
> for the light one. The nose will need to be raised further while in
> the turn (with the same bank angle) to increase AOA to generate
> sufficient lift. Leaving the AOA unchanged will result in a larger
> radius caused by a skidding turn, which is uncoordinated flight, and
> therefore does not fit the bank/airspeed formula for turn radius. A
> skidding turn is also asking for a nasty stall and spin.


And there, folks, I made a mistake. Insufficient AOA in the turn
will not only increase its radius, the airplane will descend as well.
The descent will be much more pronounced than any skid.
Too early in the morning, while thinking one thing and typing
another.

> A given airspeed/bank angle/turn radius will generate the same G
> forces regardless of the airplane's weight or AOA.
>
> > Either way, the lighter plane has a big advantage. Note that even
> > flying straight and level, the lighter plane will be faster. In the
> > above example, it needs to generate 2 pounds less lift just flying
> > along, and more lift equals more drag.

>
> Cruise speed is the one performance parameter least affected by
> weight. Weight increases induced drag (drag caused by generating
> lift), and induced drag is already at a minimum in cruise. See my
> earlier post (#26) in this thread. Having instruments make so many
> things clear. Being an instructor of this stuff helps, too.
>
> As far as the general argument goes, lighter is better if you want
> good performance. But light must not come at the expense of reasonable
> strength or minimal drag.
>
> Dan

 


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