fin/wing tanks freezing

Can anyone share some wisdom on using water at high elevations for long durations? How do you know your fin or wing tanks will not freeze? If I am at 18K for 6 hrs in the Sierras, I really don't want my vertical stab splitting open in flight. Has this ever happened? Any guidance would be appreciated.

Matt

On Wednesday, June 5, 2013 8:41:20 AM UTC-7, Matt Herron Jr. wrote:
Can anyone share some wisdom on using water at high elevations for long durations? How do you know your fin or wing tanks will not freeze? If I am at 18K for 6 hrs in the Sierras, I really don't want my vertical stab splitting open in flight. Has this ever happened? Any guidance would be appreciated.



Matt

I know in the Duo Discus I used to own (part of) the OAT gage was a required instrument just for this reason. It will take a long time for a wing tank, or even a fin tank to freeze. But we did have an incident where a dribbling leak from the fin tank collected in the rudder counterbalance and froze, freezing the rudder solid. This was on a day when the return from Mt. Whitney to Truckee was a no-turn romp at 17,999 ft. It did finally unfreeze as the Duo descended on final. I don't know of anyone who has had a fin tank freeze.

Am 05.06.2013 17:41, Matt Herron Jr. wrote:
Can anyone share some wisdom on using water at high elevations for long durations? How do you know your fin or wing tanks will not freeze? If I am at 18K for 6 hrs in the Sierras, I really don't want my vertical stab splitting open in flight. Has this ever happened? Any guidance would be appreciated.

Matt


They will freeze. Depending on the layout of the tanks, it may do damage
to the tank or wing structure.

If you fly in air mass below freezing point, either
- do not use water ballast
- or add the appropriate amount of antifreeze to the water.

If possible, you can land with the ballast water and then recollect the
antifreeze mixture. I know of several pilots that have done it that way.

--
Peter Scholz
ASW24 JE

I fly a Ventus C with integral tanks (no Bags) any issues with antifreeze and carbon/fiberglass tanks? What would be the recommended amount? Sounds like an environmental hazard to dump, and I certainly dont want to land wet unless I have to.

I have had issues with the Ventus fully loaded with water where the flaps seem to stick a bit. Not sure if it was a freezing leak or what, but was a little scary. Frozen rudder must not have been too fun.

Matt

It is folly to fly at high altitudes with water ballast on board. It is a
requirement to have an outside air temp gauge if your sailplane has water
tanks fitted (even if they are never used). I am amazed that this question
has even been posted.
cb



At 16:23 05 June 2013, Matt Herron Jr. wrote:
I fly a Ventus C with integral tanks (no Bags) any issues with antifreeze
and carbon/fiberglass tanks? What would be the recommended amount?
Sounds
like an environmental hazard to dump, and I certainly dont want to land
wet
unless I have to.

I have had issues with the Ventus fully loaded with water where the flaps
seem to stick a bit. Not sure if it was a freezing leak or what, but was
a
little scary. Frozen rudder must not have been too fun.

Matt

On Jun 5, 9:23*am, "Matt Herron Jr." wrote:
I fly a Ventus C with integral tanks (no Bags) any issues with antifreeze and carbon/fiberglass tanks? *What would be the recommended amount? *Sounds like an environmental hazard to dump, and I certainly dont want to land wet unless I have to.

I have had issues with the Ventus fully loaded with water where the flaps seem to stick a bit. *Not sure if it was a freezing leak or what, but was a little scary. *Frozen rudder must not have been too fun.

Matt

The factory probably has a recommended antifreeze agent; if so, use
that. In the absence of such a recommendation, I would probably use
propylene glycol-based antifreeze intended for winterizing RVs and
cabins; it is pretty safe stuff. I would be very wary about using
ethylene glycol antifreeze unless I knew for certain that the ballast
system bags, tanks, linings, plumbing, seals, and valves were all
compatible with it. And even then I probably wouldn't use it for
environmental reasons.

Thanks, Bob K.

even if it doesnt freeze in the tanks, it may well when dumped. I
know of a case of this in the uk, the ice buildup at the base of the
fin apparently made things interesting.

Anyone understand the the issues of high altitude limiting speeds
and a ballasted glider?

At 15:41 05 June 2013, Matt Herron Jr. wrote:
Can anyone share some wisdom on using water at high elevations
for long
dur=
ations? How do you know your fin or wing tanks will not freeze?
If I am
a=
t 18K for 6 hrs in the Sierras, I really don't want my vertical stab
splitt=
ing open in flight. Has this ever happened? Any guidance would
be
apprecia=
ted.

Matt

In the Sierra, we fly every day at high altitudes with water ballast on board. Literally 10s of thousands of flights. 18,000 feet is common, 24,000 not unusual, OAT of around 20 F is normal. I have never heard of anyone that filled his tanks with antifreeze. Routinely landing with full tanks would be a far greater hazard. I suppose if you were contemplating a dawn-to-dusk record winter wave flight, it might be worth considering.

But perhaps we are all guilty of folly.

On Thursday, June 6, 2013 3:41:20 AM UTC+12, Matt Herron Jr. wrote:
Can anyone share some wisdom on using water at high elevations for long durations? How do you know your fin or wing tanks will not freeze? If I am at 18K for 6 hrs in the Sierras, I really don't want my vertical stab splitting open in flight. Has this ever happened? Any guidance would be appreciated.



Matt

I fly at Omarama and we spend a lot of time high and cold. -10 to -20 C is common, sometimes less. As I mostly fly a Duo Discus I almost always have tail water and occasionally wing water.

I've never heard of any-one having a problem with wing water causing structural problems by freezing in flight. What does cause problems is the dump valves freezing and being unable to dump. You also see people having problems with leaking valves. They land with enormous ice sculptures under the wing.

Tail water does freeze, but I've never seen it break anything structural. The dump valves do fail when they freeze. Water going out the overflow holes freezes and can jam the rudder. I have seen a thin rod of ice forced out of the top overflow hole.

Some people do use anti-freeze in the tail, others prefer not to due to fears that the anti-freeze will damage the seals and such.

The real danger is if you load up with water and the tail valve freezes. The wings dump and you are left with the tail water and an aft C of G. In a Duo that isn't a problem because with two people you have the tail mostly full anyway for trim. In a single seater you might get into real trouble.

Different systems have different problems, but actual ballast turning solid and bursting the structure isn't a problem. Dump valves getting damaged and leaking does happen. That's just a nuisance.

Water getting into controls and freezing does happen. Being unable to dump the ballast does happen. That is much more serious.

--
Philip Plane

I mix half a liter of methanol in the tail tank of a Ventus C. I don’t put any in the wing tanks which have a higher mass to surface area ratio and thus a longer thermal time constant. I’ve been doing this for 20 years and have not had a problem yet. Your mileage may vary.
This system was put to the test recently on a particularly cold (for the southwest U.S.) early-season flight at altitudes up to 17,500’. The OAT got down to -10 C and was probably below freezing for 2 hours straight.
I have often had water leak from the wing valves, run back into the gap between the flap and wing fairing, freeze, and jam the flaps (which are interconnected to the ailerons). As a previous poster noted, this is quite unpleasant. I was encouraged by the fact that this did not occur on my recent flight for which I had been particularly diligent with the application of Chap Stick to the mating surfaces of the valves prior to filling.
Other than the leakage, I have never dumped untreated water when the OAT is below freezing. Considering the flap jamming issue and the potential for freezing on tail surfaces, this would seem to be a bad idea.
Methanol (methyl alcohol) is readily available at hot rod shops, reasonably priced, and relatively benign environmentally (it will evaporate before reaching the ground).
Mike Koerner