What are the forces on a tied down glider?

Just some facts, Eric. At Stead 2 gliders that were tied down at wing
tips and tail with 3/8" poly rope, broke all 3 ropes and performed a
near perfect half loop landing upside down after experiencing a
reported 100 knot wind (ships were tied down facing the wind).

At Minden 2 ships did much the same maneuver after experiencing about
the same wind (Winter storm frontal passage).

Raising the tail to get a negative angle of attack and locking the
spoilers open can go a long way in preventing the above OR, put it in
the box!
JJ

JJ Sinclair wrote:
Just some facts, Eric. At Stead 2 gliders that were tied down at wing
tips and tail with 3/8" poly rope, broke all 3 ropes and performed a
near perfect half loop landing upside down after experiencing a
reported 100 knot wind (ships were tied down facing the wind).

At Minden 2 ships did much the same maneuver after experiencing about
the same wind (Winter storm frontal passage).

Raising the tail to get a negative angle of attack and locking the
spoilers open can go a long way in preventing the above OR, put it in
the box!

Does anyone know the force required to break those ropes; for example,
were the ropes tested afterwards for breaking strength?

Was there any analysis of the forces on the gliders? A 100 knots might
destroy a glider, even if the ropes held. That happened to our club
Blanik years ago in winds of about 70 mph.

--
Eric Greenwell - Washington State, USA
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On Aug 13, 10:03*pm, Eric Greenwell wrote:
snip

Does anyone know the force required to break those ropes; for example,
were the ropes tested afterwards for breaking strength?
snip

The weakest point is where the problem is, and that is often the knot
not the rope unless the rope is old and tatty.

However, the breaking strength of ropes sold for marine applications
is tested and known, and some kinds of rope (probably not the best for
tie-down applications) are very, very strong.