Tie Down Straps - Help Needed

Hi Bill,

That is a very strong accusation against the CLAW. Can you please give more
information about the circumstances of the 2 failures? Was the CLAW used
properly? It is designed for straight-up loads - not side-loads. I am
extremely impressed with the design of the CLAW. Until your post I have
heard only positive comments on it. It would seem to me (being a mechanical
engineer) that the CLAW is uniquely designed to grab hold more tightly when
a load is applied (from directly above).

The link to the flyties below does look interesting, but I don't agree that
it would be more robust than the CLAW.

Thanks,

Paul Remde

"Bill Daniels" bildan@comcast-dot-net wrote in message
...

"brianDG303" wrote in message
...
I always get tie down stuff from Mac's. They sell a nice strap for $5,
and check out this strap pad-

http://www.macscustomtiedowns.com/product/115/TieDowns


The CLAW- when I looked at this I decided to use flyties (
http://www.flyties.com/ ). The Claw looks like it will hold great as
long as the pulling force is directly up, but if the load moves around
it seems like the device itself would act as a lever with the near
arms prying the far stake up and out. In any case off center loads
will concentrate on individual stakes, perhaps.

Or maybe I just like the flyties better. The tool they give you to
pull the stakes out is really nice.


FWIW, I know of two gliders totaled as a result of the "claw" pulling out
of the ground. Gliders tend to repeatedly yank at their tiedowns in a
storm. This will weaken the hold of almost any stake system including the
"Claw".

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.

Take a look at airport tiedowns where there's some liability involved.
These are usually 1/2 - 3/4" steel cable set in several hundred pounds of
concrete at multiple points. Anything less is a short term expediency used
under emergency conditions with no guarantees.

I spent some time working on the problem before giving up on stakes
altogether and working out the "bury the ditty bag" scheme. Even if a
dittybag does pull out of the ground, there's still several hundred pounds
of dirt tied to each wing. Ditty bags and a folding trenching tool weigh
less than stakes too. Why not find a good source of those to sell?

BTW, trenching tools have dug some pretty deep holes. I've been sold by
Marines that it's truly amazing how quick and deep you can dig when being
shot at.

"Paul Remde" wrote in message
news:5sUAk.350834$yE1.314870@attbi_s21...
Hi Bill,

That is a very strong accusation against the CLAW. Can you please give
more information about the circumstances of the 2 failures? Was the CLAW
used properly? It is designed for straight-up loads - not side-loads. I
am extremely impressed with the design of the CLAW. Until your post I
have heard only positive comments on it. It would seem to me (being a
mechanical engineer) that the CLAW is uniquely designed to grab hold more
tightly when a load is applied (from directly above).

The link to the flyties below does look interesting, but I don't agree
that it would be more robust than the CLAW.

Thanks,

Paul Remde

"Bill Daniels" bildan@comcast-dot-net wrote in message
...

"brianDG303" wrote in message
...
I always get tie down stuff from Mac's. They sell a nice strap for $5,
and check out this strap pad-

http://www.macscustomtiedowns.com/product/115/TieDowns


The CLAW- when I looked at this I decided to use flyties (
http://www.flyties.com/ ). The Claw looks like it will hold great as
long as the pulling force is directly up, but if the load moves around
it seems like the device itself would act as a lever with the near
arms prying the far stake up and out. In any case off center loads
will concentrate on individual stakes, perhaps.

Or maybe I just like the flyties better. The tool they give you to
pull the stakes out is really nice.


FWIW, I know of two gliders totaled as a result of the "claw" pulling out
of the ground. Gliders tend to repeatedly yank at their tiedowns in a
storm. This will weaken the hold of almost any stake system including the
"Claw".

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...

On Sep 19, 5:38*pm, sisu1a wrote:
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

I agree with Bill. I did a test with the claw attached to my trailer
jack and the wheel on a scale. The claw pulled out of compacted
decomposed granite in my driveway at about 250 lbs, came completetly
out at 300, but this was aided by weed stop fabric under the DG. The
soil was damp to a great depth due the the Socal rains in January this
year, but not soggy. I doubt that dry, uncompacted sand would do
better.

I have the claw in my Cirrus as an emegency tie down only, I think it
is a good product for that application.

For permanent tie downs nothing like a tire buried with a chain around
it. One the sand is watered down, it is not goining anywhere.

Mike Malis.

On Sep 19, 6:05*pm, wrote:
On Sep 19, 5:38*pm, sisu1a wrote:

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

I agree with Bill. *I did a test with the claw attached to my trailer
jack and the wheel on a scale. *The claw pulled out of compacted
decomposed granite in my driveway at about 250 lbs, came completetly
out at 300, but this was aided by weed stop fabric under the DG. *The
soil was damp to a great depth due the the Socal rains in January this
year, but not soggy. *I doubt that dry, uncompacted sand would do
better.

I have the claw in my Cirrus as an emegency tie down only, I think it
is a good product for that application.

For permanent tie downs nothing like a tire buried with a chain around
it. *One the sand is watered down, it is not goining anywhere.

Mike Malis.

Ditto. I think the claw is a good option as an landout or similar
situation. I've tried a few screw in types and you just cant get them
into either the hard compacted dirt or rocky soils in many locations.
The best place for the glider to be is inside it's box or a hangar.
Otherwise get a real tie down installed, the claw and screw-ins are
all completely inappropriate for permanent tie downs. It is not that
hard to dig a hole, sink some anchors and fill with concrete.

Darryl

On Sep 19, 8:31*pm, Darryl Ramm wrote:
On Sep 19, 6:05*pm, wrote:



On Sep 19, 5:38*pm, sisu1a wrote:

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

I agree with Bill. *I did a test with the claw attached to my trailer
jack and the wheel on a scale. *The claw pulled out of compacted
decomposed granite in my driveway at about 250 lbs, came completetly
out at 300, but this was aided by weed stop fabric under the DG. *The
soil was damp to a great depth due the the Socal rains in January this
year, but not soggy. *I doubt that dry, uncompacted sand would do
better.

I have the claw in my Cirrus as an emegency tie down only, I think it
is a good product for that application.

For permanent tie downs nothing like a tire buried with a chain around
it. *One the sand is watered down, it is not goining anywhere.

Mike Malis.

Ditto. I think the claw is a good option as an landout or similar
situation. I've tried a few screw in types and you just cant get them
into either the hard compacted dirt or rocky soils in many locations.
The best place for the glider to be is inside it's box or a hangar.
Otherwise get a real tie down installed, the claw and screw-ins are
all completely inappropriate for permanent tie downs. It is not that
hard to dig a hole, sink some anchors and fill with concrete.

Same here. I keep a claw in each aircraft I fly (powered and glider)
because it's the best thing I've found out there. The kit is a bit
heavy, but that's fine by me because it' not cheap and will do the job
for a few days of tie-down.

Jeremy

On Fri, 19 Sep 2008 15:47:09 -0600, "Bill Daniels"
bildan@comcast-dot-net wrote:
[snip]

BTW, trenching tools have dug some pretty deep holes. I've been sold by
Marines that it's truly amazing how quick and deep you can dig when being
shot at.

And the dirt flying in the air tends to distract the enemy's aim...;-)

rj

"Paul Remde" wrote in message
news:5sUAk.350834$yE1.314870@attbi_s21...
Hi Bill,

That is a very strong accusation against the CLAW. Can you please give
more information about the circumstances of the 2 failures?

There was a Husky aircraft lost last year while tied out using the Claw. The
Claw's casting failed, IIRC. However, there was some question as to whether
a nearby aircraft's tie down failed first, hitting the Husky. Both aircraft
totaled.

bumper
zz
Minden