On Sep 19, 2:47*pm, "Bill Daniels" bildan@comcast-dot-net wrote:
I one of them was Paul Hansen's Sisu 1A in California the other was a
Schweizer in Texas - Houston I think. *Anyway there are dozens more stories
of stakes pulling out leading to the distruction of gliders in the history
of gliding.

I don't think it's a matter of mechanical engineering, it's soil
engineering. *Stakes will hold in turf or damp soil held together by strong
roots. *The dry sand and gravel of western deserts just won't hold a stake
no matter how cleverly it's designed. *Even half axle shafts driven in with
a sledge hammer have pulled out. *The act of driving in the stake loosens
the soil enough to prevent the stake(s) from holding making the whole
exercise self-defeating.

My Sisu did indeed get pulled out when tied out with the Claw anchors,
but it was really my own fault and not a design flaw. They are
wonderful tiedowns, but like any portable solution they are NOT a
substitute for permanent anchors or proper ground handling. Mine were
in the ground for far too long prior to the big storm. I did have the
tail up on a bucket and the wings on stands, but this did not make up
for the compromised condition of the soil my anchors were in by the
time of the storm. There was an SGS 1-35 tied out right next to my
ship in the exact same manner. His tiedowns held. The difference? Mine
had been in for about 5 months. His only 2. There is no better
portable tiedown system out there, and I still use them today.

Recapping, they had no problem holding a 1-35 into the ground in a
sustained 60+mph headwind (gusting higher...), despite being in the
ground for 2 months, that was completely saturated, soft, and muddy by
the time of the storm. Hmmm, pretty impressive actually!

I have no details of the TX SGS, so I will not comment on that one.

With mine though, like any terrible incident in aviation there was a
chain of events that could have been broken at numerous links. Had I
simply pulled out my tiedowns and re-situated them in fresh earth, had
I opened my spoilers, had I added my second (then dormant) set, had I
de-regged and put it in the trailer...Any one of these solutions would
have made all the difference. Lesson learned : (

Bottom line though, those claw anchors are badd a$$, just use them as
they are supposed to be used. There are NO other portable spike/
dogscrew type anchors that come even close to competing with them for
holding power, ease of installation, and especially in ease of removal
(that I have heard of/seen tested anyways...).

-Paul

PS. I like the ditty bag idea, but there are many places out west
where you would have trouble getting even a full size spade shovel
into the ground let alone one of those army surplus portable shovels,
and you can't guarantee the prospect of finding loose rocks either.
The Claw anchors go in in about one minute apiece in hard ground, and
that is where they can develop their full 1200lb pull rating (they
take ~500lbs apiece to pull out of soft grass turf, close to double
the other styles tested by Sporty's [inc the spikes-through-a-hockey
puck type mentioned in a previous post here...]). The ditty bag
solution however IS light enough to have little excuse for not having
it on hand the ship just in case it may work though...