I don't recall a thermometer in the tail tank as a requirement in either of
my LS-6s. Maybe because they were early models...

My LAK-17a Pilot's Manual requires an OAT gauge if water ballast is carried
and states further:

Warning:
Flight with water ballast must be conducted at an OAT greater than 1° C
(34°F). If there is a risk of freezing temperatures, all water must be
dumped before freezing temperatures are reached.

Being somewhat of a "test pilot", I often fly with water at below freezing
temperatures (it's cold at 18,000' MSL regardless of seasons), but I
generally don't spend more than a couple of hours at those altitudes and
temperatures. I also spend plenty of time on the descent to allow things to
warm up at a reasonable rate.

Having said that, I've had a stuck wing dump valve more than once. It's not
noticeable until the glider comes to rest.

"Andy" wrote in message
...
On Jun 6, 3:37 pm, wrote:
What I was wondering is whether there are any gliders out there with
thermometers in the tanks.

I think some, if not all, LS gliders, have tail tank thermometers and
that it was a requirement of the type certificate. Never understood
why it should be required for one make/model but not for gliders from
other manufacturers.

When I had my ASW-19b I was concerned out wing ballast temperature.
Since the 19 uses bags it was easy to fit a thermistor probe under one
of the ballast bags and connect to a cockpit thermometer. (Radio Shack
indoor/outdoor thermometer with a connector break in the outdoor probe
lead). I was surprised at how warm the ballast stayed despite long
cold soaks at altitude.

The risk of tail ballast failing to dump is taken seriously by some
manufacturers but not by others. For the ASW-28 the aft cg limit
moves forward as mass is increased. If I operate within limits I
will not exceed the aft CG limit if my tail tank fails to dump.

On the other hand, the Duo Discus handbook recommends an increase in
minimum front seat mass if a tail tank is fitted. It then goes on to
say it's only a recommendation and you can ignore that safety
protection if you want to.

Failure to dump the tail ballast is not just a freeze risk. The valve
can jam or the cable can break when it's nice and warm outside. I've
even seen a well meaning crew tape over ballast vent holes.

Andy