At 13:17 13 December 2017, krasw wrote:
lauantai 9. joulukuuta 2017 7.57.41 UTC+2 FZ kirjoitti:
I'm driving past the nice grass field. Looks big, but it is surrounded
on=
all sides by the 80 ft high trees. What should be a minimum length of
this=
field, for a modern glider to safely land there? How to calculate it?

I would add 10 times the height of trees to required field length.
Inexperi=
enced pilots fly over treetops usually with too much altitude (yes it
feels=
safer, but at same time is kind of dangerous if the field is short).
Exper=
ienced pilot who aims for treetops (and with normal landing speed), 6
times=
tree height to touch-down should be doable.

Having landed in a field with tall trees on the far boundary and 15kts of
wind, I was amazed by the extra wind gradient the trees caused. If there is
any appreciable wind then give the trees a lot more room. A ground loop at
the end of the field is a lot less painful than a glider/tree interface
moment at 80ft in the air!

The better option is select a better field.