At 10:04 AM 1/17/2019, you wrote:
why not fly with a fwd CoG
I have read somewhere that the CG range offered
in the manual still has a safety factor built
in, so its pretty safe anywhere forward of 2/3rds back.
Here is an interesting point about CG.
There are two primary ways that the pilot senses lift
1) increasing pressure in the buttocks, lower
spine and inner ear by vertical acceleration
2) by a change of the location of the horizon
(the tail raises) and the eyes sense the change
The latter is interesting, as the mix of these
two will result for some people in a sense lift
as push forward or push in the back feeling.
That is because the glider actually accelerates
momentarily on entering lift. Draw the diagram
and remember that the lift vector is at right
angles to the relative airflow. The time constant
for this is around 0.5 seconds for a modern
ballasted glider so after a bit over a second most of the effect has gone away.
Most people are flying attitude and will
automatically pull the stick back to maintain the
attitude. This results in them feeling like "the
tail is being pushed up" as they pull back. If
you are turning and the thermal is strong and
you are too keen to maintain the attitude you can
stall the wing(s), spin and try to kill yourself.
The dynamically and statically lighter the tail
is, the faster it will rise (it rises in
response to the change of angle of attack caused
by the rising air). The faster is rises the easier it is to feel.
A nose heavy CG slows the âriseâ response
making it harder to feel the lift, this is most
prominent when seeking bubbles and lines than big thermals.
Wrong way around. Forward C of G makes the glider
more statically stable. I was in Germany in 1988
when the SB13 flying wing glider flew. They were
pretty cautious and had a forward C of G and
being a wing it had a low moment of inertia
around the C of G in the pitching direction. It
proved unpleasant to fly like that as it reacted
too quickly to up and down gusts so they ran the
C of G aft to make the static stability more neutral.
Mike
The diana 2 is know to be able to signal lift
very well, this is likely why. (it has very low
tail and boom mass, and less inertial and therefore faster to respond)
Richard Frawley
<mailto:[email protected]>[email protected]
We do not inherit the earth from our ancestors, we borrow it from our children
On 17 Jan 2019, at 10:43 am, Nick Gilbert
<<mailto:[email protected]>[email protected]> wrote:
Mike,
Iâm sure this is the wrong answer, but to me
it feels more comfortable slightly nose high -
so yawstring indicating right rudder required
if turning right. I fly with forward c of g which may be a factor.
I have no idea if this is more or less
efficient, and Iâm under no impression that
itâs the optimal method. Just that it feels more comfortable.
Nick.
On 17 Jan 2019, at 10:09 am, Mike Borgelt
<<mailto:[email protected]>[email protected]>
wrote:
Yes, to be pedantic it is trailing but common
vernacular is to call the back end of the yaw
string the direction it is pointing.
Now can someone answer the questions please?
When circling in a thermal, do you
a) keep the string centered
b) fly with it pointing to the outside of the turn
c) why?
Mike
At 09:12 AM 1/17/2019, you wrote:
Mike,
In your original question,
Part b,
By "pointing" I presume you mean "trailing" ?
To me, in this case "pointing" could be the
direction of the forward end of the string.Ã
On Thu, 17 Jan. 2019, 9:54 am Mike Borgelt
<<mailto:[email protected]>
[email protected] wrote:
So how about answering the questions?
Mike
At 08:51 AM 1/17/2019, you wrote:
and what is the expected differential
(gain/loss) with say a 10degree slip
indication variation, given all the other factors that determine climb rate.
This might b able to be worked out
mathematically given the airflows angle on
the wing and fuselage drags differences
I suspect that are several aerodynamic
factors would have to be considered,
especially given the the thermal core is dynamic.
A question for modern designers perhaps,
especially when all aviation design is a trade off
Richard Frawley
<mailto:[email protected]>[email protected]
We do not inherit the earth from our
ancestors, we borrow it from our children
On 17 Jan 2019, at 9:43 am, Mike Borgelt
<<mailto:[email protected]>
[email protected]> wrote:
At 07:36 AM 1/17/2019, you wrote:
Perhaps the more important question is how
to you tell if one technique is better than another. What is a useful baseline?
Climbing better than the other gliders is
the test but what if everybody is using the same less than optimum technique?
Mike
On 17 Jan 2019, at 7:16 am, Mike Borgelt
<<mailto:[email protected]>
[email protected]> wrote:
When circling in a thermal, do you
a) keep the string centered
b) fly with it pointing to the outside of the turn
c) why?
Your technique may not be doing what you think it is.
Mike
Borgelt Instruments - design &
manufacture of quality soaring instrumentation since 1978
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