Max Weight of Non Lift Producing Components

At 01:59 08 December 2017, Dan Daly wrote:
On Thursday, December 7, 2017 at 7:27:02 PM UTC-5, Jim wrote:
I admit I am baffled by "max weight of non-lifting parts". I
understand
=
the issue of spar bending moment limits, and I think I understand that
weig=
hing a glider without its wings will give the current non-lifting (i.e.,
no=
n-wing) weight, but I have a feeling there are subtle things here that I
do=
not understand.

I've rigged an ASK-21 and its wings are HEAVY! I haven't weighed
them
so=
I don't know just how heavy they are though. Certainly felt like more
tha=
n 100 lbs each. Ask me how I know. I'll guess (I know, don't guess)
each
=
wing weighs 150 lbs. Likely more. If I subtract 300 lbs from 780 and
then=
subtract that result from 1320 I'm still short of 902 - which I suppose
is=
a good thing.
=20

Glider cockpit load limits are set by the lowest value determined by:
Max AUW
Seat strength limits
Max wt of non-lifting parts
Forward CG limit

For a ASK21 for which I have the actual weighing results:
Max AUW 1320 lbs
Empty weight, fully equipped, 884 lbs
Therefore disposable load is 436 lbs
Seat strength limit is 242 lbs, so with a max weight pilot the other pilot

cannot exceed 194 lbs

Each wing weighs 219 lbs, max weight of non-lifting parts is 904 lbs.
Fuselage, tailplane, etc wt is 884 - 438 = 446 lbs. Hence max load
considering only non-lifting parts limit is 904 - 446 = 458 lbs. The AUW

limit takes precedence.

On this aircraft forward CG limit did not determine max cockpit load.
Min cockpit load is set by aft CG limit.