Improved Towhook from Aircraft Spruce

Bill Daniels wrote:
Robert Mudd is dead on.

I would add that there is considerable safety and operational value in
standardization. On any airfield today, Tost is the dominant
ringset/release system. If a second system is used, it adds ring switching
to the rope handling chore. There is always a temptation to use a Tost
ringset on a Schweizer which WILL occasionally jam the release.
Standardizing on Tost is expensive but safer and more convenient.

Well, good luck getting Schweizer gliders banned from airfields unless
they have a Tost conversion. But I agree that not having to hassle with
switching rings on the end of the tow rope would be best. Btw, The
three Schreder gliders that I have flown accepted either the Tost ring
or the Schweizer ring without problems.

Regards,

-Doug

I would like to shed some more light on the Schreder Hook.
The Schreder hook in fact has the same features as the Toast hook.
Back pressure will release the ring, this back pressure can easily be
metered by changing a simple hardware store spring.
Ring size is not critical, nothing gets twisted or jammed to prevent
release
An other feature, due to the rotating point of the hook being near to
where the line of force is located when the glider is high above the
tow plane. The release load become less as the glider climbs above
the two plane, as well the hook can be shaped that will allow an
automatic released if a certain angle is reached and it would still
function for all normal towing conditions.

As Doug Hoffman already mentioned the hook installation needs only a
small opening, when the hook rotates and retracts,
a cover automatically swings into place and makes it rather slick
looking arrangement.
Udo


On Nov 24, 10:09 am, Doug Hoffman no.spam wrote:
wrote:
Long time readers of this news group will remeber posting from me on
the subject of Tost tow hooks verses all the others. My opinion is
tilll the same, nothing compairs to a Tost tow hook either on the
glider or on the tow plane, for safety and reliability.

Hi Robert,

Actually I did do a search of the message archives before posting and
didn't see anything about problems with a Schreder tow hook. Yes, I saw
your comments, but they were directed at the Schweizer hook.

As mentioned
in other replys to this subject the other tow hooks have have an
increase in the force needed to actuate the release that is portional
to the tension on the tow line.

Interesting. I have flown several different Schreder gliders and never
had a problem with that.

This is not good. None of the other
tow hooks have a schedule of maintaince, none of the others lock over
center and hold the tow ring in a position for easy and clean release
of the tow rope. The Schweizer and Schreader style hooks just can not
compaire to a Tost.

What are the failure modes of the Schreder nose hook (not the Schweizer
or Applebay hook)? How does the failure rate of the Schreder hook
compare to the Tost hook? I think there are quite a few Schreder pilots
out there now who would be keenly interested in knowing about this.

One reason you do not see these other tow releases retrofitted to a
lot of other gliders is that except for the Schweizer gliders, they
are not legal to use in Type Certificated gliders. For a Type
Certificated glider that was originally fitted with a Tost hook, to
have the other sype hook installed would require a fair ammount of
paperwork. A knowlegable FAA inspector would not accept only a form
337 for this change.

Of course. Sorry if you thought I meant otherwise.

Regards,

-Doug

Robert has a good point: Everyone willing to more for a sailplane than
for a house should demand the very best in accessories and options.

Wandering off-topic, the other day I was flipping through a book
called "Graphic War," which shows and describes the technical drawings
used in the technical manuals of WWII aircraft. I was probably geeking
out from the tech writer perspective, but some of the stories behind
the documentation are as interesting as the stories behind the
aircraft themselves. Okay, maybe not, but I'd argue the case.

Anyhow, one of the drawings was a cutaway of the tailwheel and swivel
of the Junkers JU52. While the text described it only in terms of its
advantages over the tailskid, the drawing showed, in addition to the
tailwheel, a tow hitch mechanism with geometry identical to that of a
scaled-up Tost E85, right down to the actuation sector and the
mirrored torsion spring that holds the release knuckle down.