CG Envelope?

[noel.wade]

Hi All,

I have a question for all of you more-experienced glider-pilots out
there:

Where is your glider's CG envelope?
Ideally, I'd love to know what it is relative to the wing chord or the
spar location - but any information is appreciated.

I'm looking for real numbers, either from your experience in a glider
or from a POH/Glider Manual... I am *not* interested in theory or
guesses (sorry, but it was a potentially bogus theory that led me to
have to ask this question, so I'm leery of theory at the moment).

Thanks, take care,

--Noel

[[email protected]]

Noel,

You mean where is the cg within the envelope when flying? With ballast
or without?

Try this, it's old, so no longer current because I no longer own it,
but it shows the location of the EW cg as well as a typical flying cg.

http://www.jimphoenix.com/jimphoenix2/pages/Nimbus/N3%20Data/N3%20Data%20img/weight%20and%20balance.xls

Jim
noel.wade wrote:
> Hi All,
>
> I have a question for all of you more-experienced glider-pilots out
> there:
>
> Where is your glider's CG envelope?
> Ideally, I'd love to know what it is relative to the wing chord or the
> spar location - but any information is appreciated.
>
> I'm looking for real numbers, either from your experience in a glider
> or from a POH/Glider Manual... I am *not* interested in theory or
> guesses (sorry, but it was a potentially bogus theory that led me to
> have to ask this question, so I'm leery of theory at the moment).
>
> Thanks, take care,
>
> --Noel

[Bob Kuykendall]

Earlier, noel.wade wrote:

> Where is your glider's CG envelope?

Dick Schreder generally recommended 25% to 40% of MAC; most sailplanes
are similar. I generally recommend 25% to 35% for the HP-18.

Basically, work back through the wing dimensions to find out what the
MAC is. Then find the spot on the wing where its chord is the same as
the MAC. Then find the longitudinal location of that wing station.
That's what the CG envelope relates to.

The final Article on the HP-18 shows how find the CG envelope in
relation to MAC and determine minimum and maximum cockpit weights from
it. The one thing in the Article I take issue with is that Dick assumes
that the mean chord is the same as the average chord, but they're not
the same. However, the difference is so small that it makes no
practical difference in this particular case:

http://www.soaridaho.com/Schreder/Schreder/Soaring_Aug_1976_HP-18.html

Thanks, Bob K.