DG-100 vs Std Libelle - opinions wanted

On Sun, 01 Apr 2018 07:26:59 -0700, davidlawley wrote:

Libelles suffer from a lack of rudder authority when rolling quickly at
low speed, but are easy to rig.
They also have balsa core wings, rather than foam.

Roger easy to rig. I haven't particularly noticed any lack of rudder
authority, but you're wrong about them all having balsa in their wing
skins. Whether they have balsa of foam depends on age, with the change-
over being spread over approximately 100 airframes:

s/n 1 - 84 had balsa/glass skins on all flying surfaces. There was a
gradual change from balsa to foam from s/n 85 to s/n 182, starting with
just the wings on s/n 85 and gradually progressing to all surfaces.

Other known differences a

s/n 1 - 94 had top and bottom surface airbrakes.
s/n 95 was the first to have only top surface airbrakes.

At some point the tailplane changed, with increased chord and a thicker
section, but I don't know what this happened - possibly s/n 182, which
was the first H.201B Std Libelle.

At s/n 321 an AD allowed all Std Libelles to be recertified as
B-series. This was a flight manual revision: there were no other changes.


--
Martin | martin at
Gregorie | gregorie dot org

I thought the change ftom balsa was with the 201b, but wasnt certain.
The ones ive seen have all been balsa, with under over brakes.
Regards
Dave L

On Mon, 02 Apr 2018 00:19:37 -0700, davidlawley wrote:

I thought the change ftom balsa was with the 201b, but wasnt certain.
The ones ive seen have all been balsa, with under over brakes. Regards
Dave L

I don't remember exactly where I found that list detailing the change-
over stages from H.201 to H.201B, but it was almost certainly the
Technical notes list on the Glasfaser website. That has been revised
recently. The general sequence of the modifications that converted the
H.201 into an H.201B Std Libelle was correct, but the werk nrs at which
the changes were introduced have been revised. I've just updated my notes
to match Glasfaser's TN list. My notes are at:

https://www.gregorie.org/gliding/lib...201_notes.html



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Martin | martin at
Gregorie | gregorie dot org

Hi Martin, read your notes, under handling point 3, you suggest that differential makes the down going aileron travel further than the upgoing one.
That is the opposite of normal differential, which has the upgoing aileron travel more than the downgoing one. The downgoing aileron produces more drag than the upgoing one.
This is why rudder is required to prevent adverse yaw.
Just sayin.
Regards
Dave L

On Tue, 03 Apr 2018 17:07:47 -0700, davidlawley wrote:

Hi Martin, read your notes, under handling point 3, you suggest that
differential makes the down going aileron travel further than the
upgoing one.

Yep - and I was wrong. Just looked at the data sheet, which shows a lot
of differential, but in the other direction: 20 degrees up, 12 down.
Moral: trust the data sheet, not ones imperfect recollection.

Thanks for spotting it. I've just updated the page by removing the
reference to aileron differential, but the rest of the comment about the
occurrence of aileron stalls matches my experience.

This is why rudder is required to prevent adverse yaw.

Indeed, and its still needed because even a 12 degree downward deflection
adds more drag than 20 degrees of upward deflection.

However, I still think that this year I'll fit a set of 35mm wingtip
skids. Mine has 12mm rubber blocks fitted which are a bit too short: a
fully deflected aileron can touch the ground.


--
Martin | martin at
Gregorie | gregorie dot org

If you think of differential in terms of a ratio, yours is a bit less than 2:1, my DG202 is 2:1.
In my days of F3B model flying, I used up to 4:1 for thermalling, and still got adverse yaw, reqiring rudder mixed in.
For the speed task, flown at a very low angle of attack, no differential. With electronic control mixing, a lot of options open
such as flap to elevator (cruising) and elevator to flap (Thermaling) mixing.

On Wed, 04 Apr 2018 05:24:09 -0700, davidlawley wrote:

If you think of differential in terms of a ratio, yours is a bit less
than 2:1, my DG202 is 2:1.
In my days of F3B model flying, I used up to 4:1 for thermalling, and
still got adverse yaw, reqiring rudder mixed in.

You were obviously involved with another part of the model world than I
was. Flew C/L when I was a kid and then moved in to single channel RC. I
gave up RC just about the time that proportional radios appeared because
I'd got involved with competitive Free Flight, mostly F1A gliders and
1/2A / F1J power.


--
Martin | martin at
Gregorie | gregorie dot org